JPH0792443A - View finder and video camera using the same - Google Patents

Abstract

PURPOSE:To provide a compact low-power-consumption view finder for a video camera. CONSTITUTION:Light radiating at a wide solid angle from the light emitting part of the small region of a light emitting element 21 is converted into nearly parallel and narrow directional light by a condenser lens 23 and made incident on a liquid crystal panel 24. A high-molecular dispersion liquid crystal panel is used as a liquid crystal panel 24 and polarizing plates 28a and 28b are arranged on sides where the light enters a display region and outgoes. The liquid crystal panel 24 modulates the light outgoing from the condensor lens 23 to display an image in accordance with a video signal. The displayed image is magnified by magnifying lenses 25 and 26. An observer varies the position of an eyepiece ring 27, for focusing. Thus, the size of the light source can be made smaller to reduce the power consumption of the light source compared with the view finder using a conventional fluorescent light box. When the high- molecular dispersion liquid crystal panel is used, the opening ratio of a picture element can be made higher and the utilization factor of the light is made higher as well so that a high luminance display can be executed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a viewfinder for monitoring projected images and the like, and a video camera using the viewfinder.

[0002]

2. Description of the Related Art A display device using a liquid crystal panel is a CRT.
Since there is a high possibility that the display device will be lighter and thinner than a display device using, the research and development is active. In recent years, a liquid crystal panel of twisted nematic mode (TN mode) in which the optical rotatory power of liquid crystal is applied to image display has been put into practical use, and is used for a portable pocket TV, a viewfinder of a video camera and the like.

A conventional viewfinder will be described below. For example, as a conventional viewfinder, Japanese Patent Laid-Open No.
The one described in Japanese Patent Publication No. 2-111233 is shown. In this specification, a viewfinder includes at least a light source such as a light emitting element and an image display panel, which are integrally configured.

The external shape of the viewfinder (Fig. 16)
Shown in. A cross-sectional structure of a conventional viewfinder is shown in (FIG. 17). 11 is a body, 12 is an eyepiece cover,
27 is an eyepiece ring, and 173 is a TN liquid crystal panel. A light source such as a liquid crystal panel and a backlight as a light source is stored in the body 11. Body 11 and eyepiece ring 2
The magnifying lenses 25 and 26 are arranged inside 7 and function as a magnifying lens when two lenses are combined. By adjusting the insertion degree of the eyepiece ring 27, the focus can be adjusted according to the eyesight of the observer. TN liquid crystal panel 173
Has a liquid crystal layer thickness of about 5 μm and has a mosaic color filter. Further, on both sides of the TN liquid crystal panel, polarizing plates 28a functioning as a polarizer and an analyzer,
28b is arranged. The viewfinder is attached to the main body of the video camera by the mounting bracket 13. It should be noted that each drawing has a portion omitted or / and enlarged or reduced in order to facilitate understanding and / or drawing. For example, an eyepiece cover and the like are omitted in the sectional view of the viewfinder. The above also applies to the following drawings.

A perspective view of the main component parts shown in FIG. 17 is shown in FIG. The light source is composed of a fluorescent tube box 171 in which a fluorescent tube is arranged, and a diffusion plate 172 arranged on the entire surface thereof. The diffusion plate 172 is used to diffuse the light emitted from the fluorescent plate box 171 to form a surface light source with uniform brightness.

A rod-shaped fluorescent tube is used as the light generating means of the conventional viewfinder. Fluorescent tubes have a diameter of 2 to 2 when the diagonal length of the LCD screen is about 1 inch.
A 5 mm one is used. When the display screen of the liquid crystal panel has a diagonal length of 1 inch or more, a plurality of fluorescent tubes are often used. Light is emitted forward and backward from the fluorescent tube.
In order to utilize the light emitted to the rear of the fluorescent tube, a concave reflector is arranged behind the fluorescent tube. The light emitted rearward from the fluorescent tube is reflected forward by the reflector. A diffusion plate 172 is arranged between the fluorescent tube and the TN liquid crystal panel 173. The diffusion plate 172 is used for diffusing light from the fluorescent tube and making it a surface light source. A surface light source is formed by the diffusion plate 172, and light from the surface light source is emitted from the liquid crystal panel 17
It is incident on 3. The light emitting area of the surface light source is the liquid crystal panel 173.
Is the same as or larger than the image display area. Polarizing plates 28a and 28b are arranged in front of and behind the TN liquid crystal panel forming the liquid crystal panel 173. A polarizing plate 28b (hereinafter referred to as a polarizer) arranged between the diffusion plate 172 and the TN liquid crystal panel 173 has a function of converting light from a surface light source into linearly polarized light. The polarizing plate 28b (hereinafter referred to as an analyzer) arranged between the TN liquid crystal panel 173 and the observer has a function of blocking the light according to the degree of modulation of the light incident on the TN liquid crystal panel 173. Usually, a polarizer 28a and an analyzer 28b
Are arranged so that the polarization directions are orthogonal to each other.

As described above, the surface light source is formed, and the light from the surface light source is converted into the linearly polarized light by the polarizer 28a. The TN liquid crystal panel 173 modulates the linearly polarized light based on the applied image signal. Analyzer 28b
Shields or transmits light according to the degree of modulation. The image is displayed as described above. Displayed image is Analyzer 2
Magnifying lenses 25 and 26 arranged between 8b and the observer
You can enlarge it by clicking.

[0008]

The video camera is required to be compact and lightweight in terms of portability and operability. Therefore, a liquid crystal panel is being introduced as a viewfinder display. However, at present, the power consumption of a viewfinder using a liquid crystal panel is considerably large. For example, the power consumption of the viewfinder using the TN liquid crystal panel is about 0.1 for the TN liquid crystal panel.
W, the light source consumes about 1.0 W, and there is an example of 1.1 W in total. Video cameras have a limited battery capacity to ensure compactness and light weight. When the power consumption of the viewfinder is large, the continuous use time becomes short, which is a big problem.

The power consumption of the viewfinder using the TN liquid crystal panel is large because of the transmittance of the diffusion plate and the light collection efficiency of the magnifying lens. A light box including a fluorescent tube and a reflector needs to be a surface light source with less uneven brightness. Therefore, in the conventional viewfinder, T
A diffusion plate 172 is arranged between the N liquid crystal panel 173 and the fluorescent tube. When a diffuser plate having a low light diffusivity is used, a light emitting pattern 191 of the fluorescent tube appears as shown in FIG. 19 and can be seen through the display screen of the liquid crystal panel 173, thus deteriorating the display quality. Therefore, a diffuser plate 172 having a high diffusivity is used, but generally, if the diffusivity is increased, the light transmittance of the diffuser plate is lowered. The diffuser plate also scatters light. The magnifying lens or the like can condense only a part of the light transmitted through the magnifying plate 172. Therefore, the light utilization rate is poor and the display brightness is low. In order to obtain the required brightness, there is no choice but to increase the amount of light output from the light source. This causes an increase in power consumption of the light source.

A problem of the TN liquid crystal panel is rubbing treatment of the alignment film. In recent years, the pixel size has become as small as 100 μm square or less, and the rubbing process is becoming difficult. Especially T
The surface of the array substrate on which FT or the like is formed has many irregularities, and good rubbing cannot be performed. Therefore, a non-aligned region is generated or a reverse domain is generated to cause light leakage, resulting in poor display contrast. In order to prevent the light leakage, the width of the black matrix formed on the surface of the counter electrode substrate must be increased. Making the black matrix thicker lowers the pixel aperture ratio, thus lowering the display brightness.

[0011]

The viewfinder of the present invention is as follows. The light emitted from the small area light emitting portion of the light emitting element in a wide solid angle is converted into light with a narrow directivity by a condenser lens and is incident on a liquid crystal panel which is a light modulating means. As the liquid crystal panel, a polymer dispersed (PD) liquid crystal panel that displays an image depending on the degree of light scattering is used. Further, in order to increase the contrast of the displayed image, polarizing plates are arranged on the entrance side and the exit side of the panel. The liquid crystal panel displays the image by modulating the light emitted from the condenser lens according to the image signal. The displayed image can be magnified with a magnifying lens arranged between the observer's eyes and the liquid crystal panel.
The polarization plate of the incident light is attached to the plane of the condenser lens and rotated about the normal line of the condenser lens, whereby the angle between the polarization axis on the incident side and the polarization axis on the emission side can be adjusted. Brightness can be easily adjusted.

Since the viewfinder of the present invention does not use a diffusion plate and the size of the light source can be small, the power consumption of the light source is smaller than that of a conventional light box using a fluorescent tube. In addition, the entire viewfinder can be downsized.

As the light emitting element of the viewfinder of the present invention, a fluorescent light emitting tube, an LED (Light Emitting Diode) or the like is used. Each of them realizes a small-area light emitting portion by a light shielding plate or the like. That is, a good point light source is realized.

[0014]

In the viewfinder, the position of the observer's pupil is almost fixed by the eyepiece cover 12, and a wide viewing angle is not required. That is, when a liquid crystal panel is used for the viewfinder, the light source arranged behind it may have a narrow directivity. When a fluorescent backlight is used as a light source, only light that travels within a small solid angle in a certain direction from a region having substantially the same size as the display region of the liquid crystal panel is used.
Light traveling in the other direction is not used.

In the present invention, a light source having a small luminous body is used,
The light emitted from the light-emitting body in a wide solid angle is converted into nearly parallel light by a condenser lens. In this case, the light emitted from the condenser lens has a narrow directivity, and the narrow directivity is sufficient for use in a viewfinder. If the size of the luminous body is small, naturally, the power consumption is also small.

The condenser lens has no aberration and the transmittance is 100%.
In the case, the luminance of the light emitting body viewed through the condenser lens is equal to the luminance of the light emitting body itself. The maximum transmittance of the liquid crystal panel including the color filter and the polarizing plate is 3%, the transmittance of the condenser lens is 90%, and the brightness required for the viewfinder is 15%.
With [ft-L], the brightness required for the light source is about 560.
It becomes [ft-L]. In the present invention, the fluorescent light emitting tube, L
Use ED.

The viewfinder of the present invention efficiently collects light emitted from a light emitting element, which has a small light emitting body or a small light emitting area as a light source, in a wide solid angle by a condensing lens. Therefore, the efficiency is high and the power consumption of the light source is low as compared with the case where the diffuser plate and the fluorescent backlight are used.

The viewfinder of the present invention uses a PD liquid crystal panel as a light modulating means. Since a polarizing plate is arranged on the light incident side and the light emitting side of the PD liquid crystal panel,
The display contrast, which is an issue for LCD panels, has been significantly improved.

Further, since the PD liquid crystal panel does not require rubbing treatment, there is no occurrence of light leakage unlike the TN liquid crystal panel in which a non-aligned region is generated. Therefore, there is a possibility that the panel manufacturing method is easy, cost reduction can be expected, and display contrast can be increased. Since the width of the black matrix can be reduced or the PD panel can be configured without using the black matrix, the pixel aperture ratio can be improved and the brightness can be increased.

[0020]

Embodiments of the present invention will be described below with reference to the drawings.

FIGS. 1 to 11 are sectional views of the viewfinder of the present invention showing the internal structure of the body 11 shown in FIG.

FIG. 1 is a sectional view of a viewfinder according to the first embodiment of the present invention. 21 is a light emitting element, 23 is a condenser lens, 24 is a PD liquid crystal panel,
Reference numerals 25 and 26 are magnifying lenses.

First, the PD liquid crystal panel which is the light modulating means of the viewfinder of the present invention will be briefly described. Polymer dispersed liquid crystals are roughly classified into two types depending on the dispersion state of liquid crystals and polymers. One is a type in which liquid crystals in the form of water droplets are dispersed in a polymer. The liquid crystal exists in the polymer in a discontinuous state. Such a liquid crystal is called a PDLC, and a liquid crystal panel using the liquid crystal is called a PDLC panel. The other one is a type in which the liquid crystal has a network shape. The liquid crystal exists in the polymer in a continuous state. Such a liquid crystal is called PNLC,
A liquid crystal panel using the liquid crystal is called a PNLC panel.

PDLC utilizes the property that the refractive index is different in the direction in which the liquid crystal is aligned. When no voltage is applied, each water droplet liquid crystal is oriented in an irregular direction. In this state, a difference in refractive index occurs between the polymer and the liquid crystal, and incident light is scattered. When a voltage is applied here, the alignment directions of the liquid crystal are aligned. If the refractive index when the liquid crystal is oriented in a certain direction is matched with the refractive index of the polymer in advance, incident light is transmitted without being scattered.

On the other hand, PNLC uses the irregularity itself of the alignment of liquid crystal molecules. The incident light is scattered in the irregular alignment state, that is, in the state where no voltage is applied.
On the other hand, when a voltage is applied and the arrangement state is made regular, light is transmitted. In the present invention, the PDLC panel is not limited to one of the PDLC panel and the PNLC panel, but the PDLC panel will be described as an example for ease of description. Also,
PDLC and PNLC are collectively referred to as polymer dispersed liquid crystal, and PDLC panel and PNLC panel are collectively referred to as P.
D liquid crystal panel. Further, the liquid crystal dispersed in the polymer-dispersed liquid crystal layer in the form of water drops is called a water drop liquid crystal, and the resin component in the peripheral portion of the water drop liquid crystal is called a polymer.

Operation of polymer dispersed liquid crystal (FIG. 12)
A brief description will be given using (a) and (b). (Fig. 12 (a)
(B) is an explanatory view of the operation of the polymer dispersed liquid crystal. In FIGS. 12A and 12B, 122 is an array substrate on which TFTs and the like are formed, 124 pixel electrodes, 121 is a counter electrode, 125 is liquid crystal droplets, 126 is a polymer, and 123 is a counter electrode substrate. A TFT (not shown) or the like is connected to the pixel electrode 124, and a voltage is applied to the pixel electrode by turning the TFT on and off to change the liquid crystal alignment direction on the pixel electrode to modulate light. As shown in FIG. 12A, in the state in which no voltage is applied, each water droplet liquid crystal 125 is oriented in an irregular direction. In this state, a difference in refractive index occurs between the polymer 126 and the water droplet liquid crystal 125, and incident light is scattered. Here, when a voltage is applied to the pixel electrode 124 as shown in FIG. 12B, the directions of the liquid crystal are aligned. If the refractive index when the liquid crystal is aligned in a certain direction is matched with the refractive index of the polymer 126 in advance, the incident light is emitted from the array substrate 122 without being scattered.

The incident light is linearly polarized by the polarizing plate 28a. The polarized light is assumed to be P polarized light. Further, the polarized light whose polarization axis differs from that of the P polarized light by 90 degrees will be referred to as S polarized light. Even when the liquid crystal layer 127 is in the scattering state, part of the light is emitted from the counter electrode substrate 121. When the liquid crystal layer 127 is in the scattering state, the P-polarized light is in a random polarized state in which S-polarized light and P-polarized light are mixed. When the liquid crystal layer 127 is in a completely diffused state, theoretically P-polarized light and S-polarized light are used.
The ratio of polarization components is 1: 1. Therefore, the liquid crystal layer 1
When 27 is in a completely diffused state, half of the light emitted from the counter electrode substrate 121 is absorbed by the analyzer 28b. When the liquid crystal layer 127 is in the transmissive state, the P-polarized light incident on the liquid crystal layer 127 reaches the analyzer 28b as it is. Since the polarization axes of the polarizer 28a and the analyzer 28b are aligned with each other, the P-polarized light passes through the analyzer 28b as it is. As described above, when the liquid crystal layer 127 is in the scattering state, part of the light emitted from the counter electrode substrate 122 is absorbed by the analyzer 28b, and when it is in the transmitting state, the incident light is absorbed by the analyzer 28b. The display contrast can be improved because the light is not transmitted.

The liquid crystal material used for the liquid crystal of the PD liquid crystal panel of the viewfinder of the present invention is nematic liquid crystal,
Smectic liquid crystals and cholesteric liquid crystals are preferable,
A single or a mixture of two or more kinds of liquid crystal compounds or substances other than the liquid crystal compounds may be used. Among the liquid crystal materials described above, a cyanobiphenyl nematic liquid crystal having a relatively large difference between the extraordinary light refractive index n _e and the ordinary light refractive index n _o is most preferable. A transparent polymer is preferable as the polymer matrix material, and the polymer may be either a thermoplastic resin or a photocurable resin, but it is UV-curable from the viewpoint of ease of manufacturing process, separation from the liquid crystal layer, etc. It is preferred to use the type of resin. As a specific example, an ultraviolet curable acrylic resin is exemplified, and a resin containing an acrylic monomer or an acrylic oligomer which is polymerized and cured by ultraviolet irradiation is particularly preferable.

As such a polymer-forming monomer,
2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, neopentyl glycol acrylate, hexanediol diacrylate, diethylene glycol diacrylate, tripropylene glycol diacrylate, polyethylene glycol diacrylate,
Examples include trimethylolpropane triacrylate, pentaerythritol acrylate and the like.

Examples of the oligomer or prepolymer include polyester acrylate, epoxy acrylate and polyurethane acrylate.

A polymerization initiator may be used to accelerate the polymerization, and an example thereof is 2-hydroxy-2-methyl-1-phenylpropan-1-one-("Darocur 1173" manufactured by Merck & Co., Inc.). , 1- (4-isopropylphenyl) -2-hydroxy-2-methylpropane-1-
ON (“Darocur 1116” manufactured by Merck & Co., Inc.), 1-vidroxycyclohexyl phenyl ketone (“Irgacure 651” manufactured by Ciba-Gaiki), and the like are applicable. In addition, a chain transfer agent, a photosensitizer, a dye, a cross-linking agent and the like may be appropriately used as an optional component.

The proportion of the liquid crystal material in the polymer-dispersed liquid crystal is not specified here, but is generally 20% by weight to 95% by weight.
The degree is good, preferably about 50 to 85% by weight. If it is 20% by weight or less, the amount of water-drop liquid crystals is small, and the scattering effect is poor. On the other hand, when it is 90% by weight or more, the polymer and the liquid crystal tend to be phase-separated into upper and lower two layers, the ratio of the interface between the liquid crystal and the polymer becomes small, and the scattering property deteriorates. The structure of the polymer-dispersed liquid crystal layer varies depending on the ratio of the liquid crystals. At about 50% by weight or less, the liquid crystals exist as independent droplets, and at 50% by weight or more, the polymer and the liquid crystals form a continuous layer.

The thickness of the liquid crystal 15 is preferably in the range of 5 to 30 μm, more preferably 10 to 20 μm. If the film thickness is thin, the scattering characteristics deteriorate and the contrast cannot be obtained. On the other hand, if it is thick, high-voltage driving must be performed, making it difficult to design a drive IC that drives the liquid crystal. In addition, the power consumption of the drive IC also increases.

Further, the average value of the particle size of the water-drop-like liquid crystal is 0.
If it is not less than 5 μm and not more than 3.0 μm, the scattering characteristics are poor and sufficient contrast cannot be obtained. Moreover,
The particle diameter is preferably 1.5 μm or more and 2.5 μm or less. In the case of PNLC, the hole diameter of the polymer, that is, the hole diameter of the polymer network, corresponds to the above-mentioned particle diameter, which corresponds to the above-mentioned particle diameter.

An advantage of the PD liquid crystal panel is that it does not require a rubbing process unlike the TN liquid crystal panel. Therefore, a panel can be manufactured even if the pixel size is extremely small, such as 50 μm or less. In the case of a TN liquid crystal panel, when the pixel size is 50 μm or less, the alignment treatment becomes very difficult due to the unevenness of the TFTs on the array substrate. Since the PD liquid crystal panel does not perform rubbing treatment,
Naturally, no non-aligned region is generated and light leakage does not occur. Therefore, the display contrast can be increased. Further, unlike the NW mode TN liquid crystal panel, the reverse tilt domain does not occur, and light leakage does not occur from the pixel peripheral portion. Therefore, in the PD liquid crystal panel, the black matrix width can be narrowed and the pixel aperture ratio can be improved, so that the display brightness can be increased. Further, since a polarizing plate is arranged on the light incident surface and the light emitting surface of the PD liquid crystal panel used in the viewfinder of the present invention, the display contrast is high.

As an example, the diagonal length of the display area of the PD liquid crystal panel 24 is 28 mm, the effective diameter of the condenser lens 23 is 30 mm, and the focal length is 15 mm. The light emitting element 21 is arranged near the focal point of the condenser lens 23. The condenser lens 23 is a plano-convex lens, and the plane is a light emitting element 21.
Looking to the side. An eyepiece ring 27 is attached to the end of the body 11. Also, the body 11 and the eyepiece ring 27
The magnifying lenses 25 and 26 are attached to each of them. The inner surface of the body is black or dark to absorb unwanted light. A polarizer 28a is attached to the entrance side of the PD liquid crystal panel 24, and an analyzer 28b is attached to the exit side thereof. Polarization axis of polarizer 28a and polarization axis 28 of analyzer 28b
Match with b. That is, when the liquid crystal layer of the PD liquid crystal panel 24 is in the transmissive state, white display is performed.

Reference numeral 22 is a light-shielding plate having a circular hole in the center. More specifically, it is a pinhole plate. Light emitting element 2
It has a function of reducing the area where the light is emitted from 1 to a small area. When the area of the hole becomes large, the display image on the PD liquid crystal panel 24 becomes bright, but the contrast is lowered. This is because the amount of light entering the condenser lens 23 increases, but the directivity of the incident light deteriorates. When the diagonal length of the display area of the liquid crystal display device is 28 mm, the light emitting area should be about 15 mm ² or less. This corresponds to the diameter of a pinhole having a diameter of approximately 4 mm. It should preferably be 10 mm ² or less. However, if the diameter of the hole is made too small, the directivity of the light becomes narrower than necessary, and when the viewfinder is viewed, the display screen becomes extremely dark just by slightly shifting the viewpoint. Therefore, the area of the hole should be at least 2 mm ² or more. As an example, when the hole diameter is a straight line of 3 mm, the brightness of the display screen equal to or higher than that of a viewfinder using a conventional surface light source can be obtained. The area of the region that emits light also corresponds to the concept of a hole diameter of a diaphragm, a pinhole, a light shielding film of a light emitting element, etc., which will be described later. The area emitting light, ie the hole diameter, should be considered to be in the range of 0.5 mm to 5 mm in diameter. However, this has a display screen diagonal length of 28 m.
In the case of m, if the diagonal length becomes long, the hole diameter also becomes large in proportion to the diagonal length. If it is defined by the display area and the area ratio of the holes that emit light, it must be 20: 1 or less.
It is preferably 40: 1 or less. However, it is preferably 200: 1 or more from the viewpoint of the viewing angle.

The light emitted from the light emitting element 21 in a wide solid angle is converted into light having a narrow directivity by the condenser lens 23, which is nearly parallel. The light is linearly polarized by the polarizer 28a and enters from the side of the counter electrode (not shown) of the PD liquid crystal panel 24. The PD liquid crystal panel changes the amount of light transmitted through the liquid crystal or the degree of scattering of the liquid crystal according to an applied video signal to form an image. The observer attaches his / her eye to the eyepiece ring 22 or the eyepiece cover 12,
The display image on the liquid crystal panel 24 will be viewed. That is,
The position of the observer's eyes is almost fixed. LCD panel 2
Assuming that all the pixels of 4 make the light go straight, the condenser lens 23 is emitted from the light emitting element 21, and all the light incident on the effective area of the condenser lens 23 is transmitted through the magnifying lenses 25 and 26. The light is incident on the observer's pupil. The combination of the two lenses 25 and 26 functions as a magnifying lens, so that an observer can magnify and see a small display image on the liquid crystal panel 24. In other words, you can see the enlarged virtual image.

Since the position of the observer's pupil in the viewfinder is substantially fixed by the eyepiece cover 12, the light source arranged behind it may have a narrow directivity. In a conventional viewfinder that uses a light box that uses a fluorescent tube as a light source, only light that travels within a small solid angle in one direction from a region that is approximately the same size as the display region of the TN liquid crystal panel is used, and in the other direction. The traveling light is not used. That is, the light utilization efficiency is very poor.

In the present invention, a light source having a small luminous body is used,
The light emitted from the light-emitting body in a wide solid angle is converted into nearly parallel light by the condenser lens 23. In this way, the light emitted from the condenser lens 23 has a narrow directivity. If the observer's viewpoint is fixed, the above-mentioned narrow directional light is sufficient for the viewfinder. If the size of the luminous body is small, naturally, the power consumption is also small. As described above, the viewfinder of the present invention utilizes that the observer views the displayed image with the viewpoint fixed. A normal direct-viewing type liquid crystal panel requires a certain viewing angle, but the viewfinder is sufficient as an application if the displayed image can be observed well from a predetermined direction.

The condenser lens 23 has no aberration and the transmittance is 10
In the case of 0%, the brightness of the light emitter seen through the condenser lens is equal to the brightness of the light emitter itself. The maximum transmittance of the liquid crystal panel, including the color filter, polarizing plate, and aperture ratio of the image, is 3%,
When the transmittance of the condenser lens 23 is 90% and the brightness required for the viewfinder is 15 [ft-L], the brightness required for the light source is about 560 [ft-L]. Light emitting elements that satisfy these requirements include cathode ray tubes, fluorescent tubes, and other light emitting tubes that use the light emitting principle, fluorescent light emitting elements, xenon lamps, halogen lamps, tungsten lamps, metal halide lamps, LEDs, and EL (Electro Luminesc).
PD, an element that emits light by the action of electrons such as
Examples thereof include P (Plasma Display Panel), which emits light by discharge, and the like, which self-luminesce. Any of these light emitting elements may be used as the light generating means, but among them, an LED having a fluorescent light emitting tube, red, blue, and green light emitting chips is the most suitable in terms of low power consumption, small size, and white light emission. is there.

In the PD liquid crystal panel, when the voltage applied to each pixel is changed, the light scattering degree of that pixel changes. The light scattering degree is the largest when no voltage is applied, and the light scattering degree decreases when the applied voltage is increased. When light with narrow directivity is incident on the liquid crystal panel 24 and the degree of light scattering is changed, the amount of light incident from the pixel to the observer's pupil changes. That is,
Since the brightness of the pixel viewed from the observer changes, an image is displayed using this.

Next, the liquid used in the viewfinder of the present invention
The drive circuit section of the crystal panel will be described. The present invention
High-contrast display in the viewfinder
Therefore, the LCD panel is an active matrix LCD panel.
Use (Figure 13) is an active matrix liquid
It is an equivalent circuit diagram of a crystal panel. In Fig. 13, G
₁~ G_mIs a gate signal line, one end of which is a gate drive line
Connected to the IC 146. Gate drive IC1
46 is a thin film transistor (hereinafter referred to as a switching element)
After that, a voltage called "TFT" depending on the operating state (hereinafter, turned on)
Voltage) or the voltage to put it into a non-operating state (hereinafter, turned off)
Output). Also, S₁~ S_nIs the source signal
Line, one end of which is connected to the source drive IC 147
Has been done. The TFT 131 is connected to the pixel electrode 124.
Accordingly, the PD liquid crystal 12 is formed between the pixel electrode 124 and the counter electrode 123.
Holds 7. In addition, one terminal of the TFT 131 is electrically charged.
When an additional capacitor 132 as a load storage element is connected
There is.

FIG. 14 is a block diagram of a signal circuit of the liquid crystal panel. In FIG. 14, reference numeral 141 is a video amplifier that amplifies the video signal to a predetermined value, 142 is a phase division circuit that creates a positive polarity and a negative polarity video signal, and 143 outputs an AC video signal whose polarity is inverted for each field. Output switching circuit 145, liquid crystal panel 144, source drive IC 147 and gate drive IC 14
6 is a driver control circuit for performing synchronization and control.

The signal processing circuit of the liquid crystal panel will be described below. First, the video signal is subjected to gain adjustment by the video amplifier 141 so that the video output amplitude corresponds to the electro-optical characteristics of the liquid crystal. Next, the gain-adjusted video signal enters the phase division circuit 142, and two video signals of positive polarity and negative polarity are created. These two video signals enter the output switching circuit 143, and the video signals whose polarities are inverted for each field are output. The reason for inverting the polarity of the signal for each field is to prevent the liquid crystal from being deteriorated by applying an AC voltage. Next, the video signal from the output switching circuit 143 is input to the source drive IC 147, and the source drive IC 147 performs signal processing such as level shift and sample hold of the video signal by the control signal from the drive control circuit 144, and the gate drive IC 146. In synchronization with the above, a predetermined voltage is output to the source signal line of the liquid crystal panel 145.

When an ON voltage is applied to the gate signal line,
The TFT connected to the gate signal line is turned on, and the video signal output to the source signal line is applied to the pixel electrode. When the off voltage is applied to the gate signal line, the TFT is turned off and the signal applied to the pixel voltage is held for one field. In the case of PD liquid crystal, a driving voltage higher than that of TN liquid crystal is required,
A maximum voltage of plus or minus 6 (V) to 8 (V) must be applied to the liquid crystal.

A mosaic color filter (not shown) is attached to the liquid crystal display device 24. The pixel arrangement is a delta arrangement, and the number of pixels is about 100,000 pixels. The color filter transmits any color of red, green and blue. The PD liquid crystal panel has poor scattering characteristics for long-wavelength light (red light). Therefore, if the liquid crystal layer thickness of the red pixel is made thicker than that of the other blue and green pixels, the scattering performance can be improved and the red, green, and blue gradation can be made uniform.

The condenser lens 23 has a flat surface, that is, a surface having a large radius of curvature, facing the light emitting body 21 side. This is because the sine condition is easily satisfied and the brightness uniformity of the display image on the liquid crystal panel 24 is improved. However, it goes without saying that the condenser lens 23 is not limited to the above-mentioned plano-convex lens, and may be a normal positive lens.

By adjusting the degree of insertion of the eyepiece ring 27 into the body 11, the focus can be adjusted according to the visual acuity of the observer. Since the position of the observer's eyes is fixed by the eyepiece cover 12, the viewpoint position hardly shifts during use of the viewfinder. If the viewpoint is fixed, the observer can see a good image even if the directivity of light to the liquid crystal panel 24 is narrow. To make it look better, the emission direction of the light from the light emitting element 21 may be moved to an optimum direction. for that reason,
It is preferable to add a position adjusting mechanism to the light emitting element 21 so that the light emitting element 21 can be moved slightly back and forth or left and right. The positive lens 25 shown in FIG.
It can also be used in the configuration shown in (a)). In this case, the magnifying power of the display screen changes slightly due to the movement of the eyepiece ring 27, but there is no problem in practical use. Of course, the focus can be adjusted according to the eyesight of the observer. The cost can be reduced, and the size and weight can be reduced. Further, it is clear that the diaphragm 22 can be omitted when the light emitting area of the light emitting element 21 is formed in a small area.

The polarizer 28a may be attached to the flat surface of the condenser lens 23 as shown in FIG. 2 (b).
The condenser lens 23 is made rotatable. By rotating the condenser lens, the angle formed by the polarization axis of the polarizer 28a and the polarization axis of the analyzer 28b can be changed, so that the brightness of the display image can be easily adjusted. That is, the amount of light flux emitted from the light emitting element 21 and reaching the magnifying lens 26 can be varied by the rotation of the condenser lens 23. In addition, as shown in FIG. 2C, the convex portion of the condenser lens 23 may be directed to the light emitting element 21 side. However, it becomes difficult to satisfy the sine condition to some extent.

A part of the light emitted from the liquid crystal panel 24 enters the observer's pupil, but the other light becomes stray light, which causes a reduction in the contrast of the displayed image. In order to avoid this problem, a diaphragm 61 may be arranged between the light emitting element 21 and the condenser lens 23 as shown in FIG. The diaphragm 61 has a circular window in the center thereof, and a plurality of diaphragms are arranged concentrically at a predetermined interval. The diaphragm 61 allows only the light emitted from the light emitting element 21 to directly enter the effective area of the condenser lens 23. The inner surfaces of the body 11 and the eyepiece ring 27 are black or dark in order to prevent light reflection. Of the light emitted from the light emitting element 21, unnecessary light is absorbed by the light shielding portion of the diaphragm 61, and light which is not absorbed but slightly reflected is absorbed by the light shielding portion of another diaphragm or the inner surface of the body 11. Therefore, it does not enter the condenser lens 23. Therefore, the reduction in the contrast of the displayed image due to the incidence of unnecessary light on the liquid crystal panel 24 becomes very small. The number of diaphragms may be one, but the greater the number, the greater the effect.

As shown in FIG. 3, a diaphragm 31 may be used to change the light emitting area of the light emitting element. The diaphragm 31 may be a variable diaphragm used in a camera, and the hole diameter of the diaphragm 31 may be changed by rotating a lever (not shown) taken out of the body 11. However, the center of the diaphragm 31 is the condenser lens 13.
Must be placed so that it passes through the central axis of. When the size of the diaphragm 31 is changed, the size of the light emitting portion of the light emitting element 21 is changed, and the directivity of the light emitted from the condenser lens 23 is changed, so that the contrast of the display image on the liquid crystal panel 24 is changed. be able to. The viewing angle can also be adjusted. While observing the displayed image, the observer can adjust the position to obtain the best display by using the lever.

Needless to say, when the light emitting area of the light emitting element 21 is very small or the area where the light shielding film is formed and light is emitted is very small, the diaphragm 22 or the like is not required as shown in FIG.

As described above, the viewfinder of the present invention efficiently collects the light emitted from the small light-emitting body of the light-emitting element 21 in a wide solid angle by the condenser lens 23.
The power consumption of the light source can be significantly reduced as compared with the case of using a backlight of a surface light source using a fluorescent tube.

The liquid crystal panel 24 is usually formed with a black matrix (not shown). The black matrix is used to obscure the movement of the liquid crystal on the signal lines of the liquid crystal panel 24 and / or to block light to the thin film transistors that switch the pixels.
However, when the number of pixels of the liquid crystal panel 24 is small, the black matrix is conspicuous and the image quality is deteriorated. By disposing a diffraction grating as an optical low-pass filter between the liquid crystal panel 24 and the observer's pupil, the black matrix can be made inconspicuous. An example of this configuration is shown in FIG. The diffraction grating 81 is arranged between the two positive lenses 25 and 26. In addition, the positive lens 26
It may be arranged in the vicinity of the incident light side of, and on the outgoing light side of the liquid crystal panel 24. However, it goes without saying that it is necessary to change the pitch, height, etc. of the diffraction grating 81 depending on the arrangement position. The diffraction grating 81 has an effect of making the black matrix hard to see. Therefore, it is possible to obtain a smooth display image without seeing the black matrix.

A transmission type diffraction grating 81 is used, and the cross-sectional shape of the diffraction grating 81 may be a sine curve shape, an arc shape, a trapezoid shape, or the like. Many variations such as one-dimensional and two-dimensional patterns of the diffraction grating 81 can be considered. The pitch is 10 when the size of the pixels of the liquid crystal panel 14 is 100 to 30 μm and the diffraction grating 81 is arranged near the liquid crystal panel 24.
The range of 0 to 20 μm is suitable. In addition, the diffraction grating 81
2 to 0.1 m when locating near the magnifying lens
m is suitable. As a method of manufacturing the diffraction grating 81, S
A method of evaporating and patterning an inorganic substance such as io ₂ on a glass substrate, a method of spin coating a mixture of a polymer and a dopant on the glass substrate, exposing through a pattern mask, and then sublimating the dopant by heating under reduced pressure. There is.

Positive lenses 25 and 26 as shown in FIG.
The viewfinder can be configured by removing.
In this case, the display screen is small because there is no magnifying lens, but the observer sees the display image by eye-contacting the eyepiece cover (not shown in (FIG. 7)) or the body 11, which is not very practical. There is no. Particularly, it is practically sufficient if the image display area of the liquid crystal panel 24 is as large as 1.5 inches or more.

FIG. 8 shows the construction of the second embodiment of the viewfinder of the present invention. Light emitting element 21
And the portion where the condenser lens 23 is arranged, and the liquid crystal panel 24
Is arranged at an angle θ, the body 1
1 has the shape of <. Light emitted from the condenser lens 23 obliquely enters the liquid crystal panel 24. Magnifying lens 25
And the normal line passing through the center of the screen of the liquid crystal panel 24 are matched. The angle θ depends on the scattering characteristics of the liquid crystal panel 24, but is in the range of 3 degrees to 20 degrees, and is optimally 4 degrees to 15 degrees. It is also easy to make the angle θ variable in terms of configuration.

In the configuration shown in (FIG. 1) to (FIG. 7),
Although the light traveling straight through the liquid crystal panel 24 is recognized as a white display of the display image, in the configuration shown in FIG.
The light scattered at 4 and traveling obliquely is recognized as a white display of the display image. That is, the former is a positive display and the latter is a negative display. To convert the negative display to the positive display, the liquid crystal panel 24
The polarity of the video signal to be added to the signal may be inverted by using an inverting amplifier or the like.

In the PD liquid crystal panel, the ratio of the transmitted light when the liquid crystal is on and the scattered light when the liquid crystal is off is called contrast. As shown in FIG. 8, collimated light is made incident on the liquid crystal panel 24, and the light emitting element 21, the condenser lens 23, and the liquid crystal panel 24.
When the eye positions are matched with each other, the transmitted light in the on state of the liquid crystal is larger than the scattered light in the off state. However, when the light is obliquely incident on the liquid crystal panel 24 and the display image of the liquid crystal panel 24 is viewed as in the configuration shown in (FIG. 8), the angle at which the scattered light in the off state becomes larger than the transmitted light. There is. Usually, the above phenomenon occurs when the angle θ is several degrees or more.
In the configuration shown in (FIG. 8), the displayed image is darker than the configurations shown in (FIG. 2) to (FIG. 7), but the contrast becomes good by selecting the angle θ. Since the eye position of the viewfinder is fixed when the display image is viewed, it is easy to adjust the predetermined angle θ so that the display image with the best contrast can be viewed.

Further, a third embodiment of the viewfinder of the present invention will be described. (FIG. 9) to (FIG. 11) are examples of the configuration. First, in order to shorten the depth of the viewfinder, the viewfinder is constructed as shown in FIG. Light emitting element 2
The light radiated from the laser beam No. 1 is deflected in the direction of 90 degrees by the mirror 91 and enters the condenser lens 23. The portion of the body 11 in which the light emitting element 11 is inserted is inserted in the video camera body. That is, the positive lens 26 is rotatable about the portion in which the light emitting element 21 is inserted so that the flat surface can be oriented horizontally or vertically.
The display image on the liquid crystal panel 24 can be viewed by freely changing the direction of the image upward or horizontal. Light emitting element 21
The light from is deflected by 90 degrees by the mirror 91 and enters the condenser lens 23. Since the other parts and matters are the same as the configurations and contents already described, the description thereof will be omitted.

Furthermore, in order to shorten the depth (Fig. 1
This is achieved by adopting the configuration of 1). Light emitting element 21
The light emitted from the mirror is bent by the mirrors 111 and 91 and enters the condenser lens 23. Note that 112 and 113
Is a circular light transmitting hole.

Although the condensing lens 23 is a plano-convex lens, it is used when the number of display pixels of the liquid crystal panel 24 is relatively small and / or when high quality image is not required (FIG. 10).
The condensing lens 23 can be replaced with the Fresnel lens 101 as shown in FIG. Since the distance between the Fresnel lens 101 and the liquid crystal panel 24 can be shortened by using the Fresnel lens 101, the depth of the viewfinder can also be shortened. In addition, weight reduction can be realized. Similarly, it goes without saying that the positive lens 26 and the like are also replaced by Fresnel lenses.

Many variations of the viewfinder of the present invention can be considered based on the description of the embodiments. All of these variations belong to the present invention. For example, in the viewfinder shown in (FIG. 9), the variable diaphragm 31 or the diffraction grating 8 is provided.
For example, a viewfinder with 1 added is applicable. Similarly, the condensing lens 23 (FIG. 1) may be replaced with a Fresnel lens.

A fluorescent light emitting tube used as the light emitting element 21 is a Luna light-type sold by Mini Pyro Electric Co.
There is a 07 series. The arc tube has a miniature bulb shape in appearance. The diameter is 7 mm, and the filament and the anode electrode are arranged inside. A DC voltage of about 4 V to 8 V is applied to the filament to heat the filament. The voltage applied to the anode is about 10 to 25 V DC. The anode voltage accelerates the electrons emitted by heating the filament. A phosphor is coated on the inner surface of the case of the arc tube, and mercury atoms are enclosed inside. The accelerated electrons emit ultraviolet rays by colliding with the mercury atoms. This ultraviolet ray excites the phosphor to generate visible light. The pulse period is 30 hertz or more, preferably 60 hertz or more. By making the voltage applied to the anode a pulse signal, the amount of emitted light can be varied in proportion to the pulse width.

When an LED is used as the light emitting element 21, a light emitting chip of three colors of red, green and blue is built in. The light emitting chip of each color has four terminals, one terminal each and a common terminal. The three light emitting chips are molded with transparent resin. The optimum number of light emitting chips of each color are densely molded so as to achieve color balance so as to obtain white light.

The LED can adjust the emission color by controlling the voltage or current applied to each of the red, green and blue light emitting chips, and can also adjust the chromaticity of the image displayed on the liquid crystal panel 24. it can. This chromaticity adjustment is extremely easy as compared with the case of using a backlight.

FIG. 15 is an explanatory view showing a state in which the viewfinder of the present invention is attached to a video camera. The body 11 of the viewfinder is attached to the video main body by a mounting bracket 13. 24 is a polymer dispersed liquid crystal display panel, and the diagonal length of the display screen is about 0.7 inch. Reference numeral 154 is a drive circuit for the liquid crystal panel mainly shown in FIG. Light emission (Lunalight-07 series) manufactured by Mini Pyro Electric Co., Ltd. was used as the light emitting element 21. The arc tube has a diameter of 7 mm and emits white light. The arc tube power supply circuit 153 supplies a voltage to the arc tube. The arc tube power supply circuit 153 supplies a heater voltage and an anode voltage to the arc tube 21. Both voltages are DC voltages. The arc tube voltage circuit has a circuit for pulse-modulating the anode voltage. The pulse period is 60 hertz. By making the voltage applied to the anode a pulse signal, the amount of emitted light can be varied in proportion to the pulse width. The pulse width ratio can be continuously changed from 0 to 1/1 by rotating a volume attached to the video body.
In one embodiment, when the pulse width is ½, the brightness of the arc tube is about 800 [ft-L]. That is, 1/1, that is, 1600 [ft-L], which is doubled when the anode voltage is continuously applied. On the other hand, a video signal is output from the CCD sensor 151, and the video amplifier 141 of the liquid crystal drive circuit 154 is output.
, And an image is displayed on the liquid crystal panel 24. In addition, the video signal recorded on the video tape is reproduced by the reproducing circuit 15.
5 and is applied to the video amplifier 141.
Reference numeral 152 denotes a battery attached to the main body of the video camera, which supplies electric power to the arc tube power supply circuit 153, the liquid crystal drive circuit 154, and the reproduction circuit 155.

[0069]

As is apparent from the above description, in the viewfinder of the present invention, light emitted from a small light-emitting body of a light-emitting element in a wide solid angle is made nearly parallel by a condenser lens and has narrow directivity. Since the image is converted and modulated by the liquid crystal panel to display an image, power consumption is low and uneven brightness is small. Moreover, since the drive circuit of the light emitting element has a simple structure as compared with a conventional viewfinder that uses a backlight, a small and lightweight viewfinder can be provided.

Since the PD liquid crystal panel is used,
Unlike the TN liquid crystal panel, there is no light leakage from the non-aligned region and light leakage due to the reverse tilt domain, and the display contrast is good. Further, since the width of the black matrix can be narrowed, the pixel aperture ratio can be increased and the display brightness can be increased.

If the polarizer is attached to the condenser lens and the condenser lens can be rotated, the brightness of the displayed image can be easily adjusted.

[Brief description of drawings]

FIG. 1 is a sectional view of a viewfinder according to an embodiment of the present invention.

FIG. 2 is a sectional view of a viewfinder according to another embodiment of the present invention.

FIG. 3 is a sectional view of a viewfinder according to another embodiment of the present invention.

FIG. 4 is a sectional view of a viewfinder according to another embodiment of the present invention.

FIG. 5 is a sectional view of a viewfinder according to another embodiment of the present invention.

FIG. 6 is a sectional view of a viewfinder according to another embodiment of the present invention.

FIG. 7 is a sectional view of a viewfinder according to another embodiment of the present invention.

FIG. 8 is a sectional view of a viewfinder according to another embodiment of the present invention.

FIG. 9 is a sectional view of a viewfinder according to another embodiment of the present invention.

FIG. 10 is a sectional view of a viewfinder according to another embodiment of the present invention.

FIG. 11 is a sectional view of a viewfinder according to another embodiment of the present invention.

FIG. 12 is an explanatory diagram of the operation of the polymer dispersed liquid crystal.

FIG. 13 is an equivalent circuit diagram of a liquid crystal panel.

FIG. 14 is a block diagram of a drive circuit of a liquid crystal panel.

FIG. 15 is a circuit block diagram of a video camera.

16 is an external view of the viewfinder.

FIG. 17 is a sectional view of a conventional viewfinder.

FIG. 18 is a perspective view of main components of a conventional viewfinder.

FIG. 19 is a plan view of the light box.

[Explanation of symbols]

 11 Body 12 Eyepiece Cover 13 Mounting Hardware 21 Light-Emitting Element 22, 31, 61 Aperture 23 Condensing Lens 24 Liquid Crystal Panel 25, 26 Magnifying Lens 27 Eyepiece Ring 28a, 28b Polarizing Plate 81 Diffraction Grating 91, 111 Mirror 101 Fresnel Lens 102, 112 , 113 holes 121 counter electrode substrate 122 array substrate 123 counter electrode 124 pixel electrode 125 water droplet liquid crystal 126 polymer 127 liquid crystal layer 131 TFT 132 additional capacitor 146 gate drive IC 147 source drive IC 171 fluorescent tube box 172 diffusion plate 173 TN liquid crystal panel 191 Luminous pattern of fluorescent tube

Claims (16)

[Claims] 1. A light generating means, a condensing means for converting light emitted from the light generating means into substantially parallel light, and light emitted from the condensing means is modulated so that a light scattering state is changed. The light modulating means for forming an image, the first polarizing means arranged on the light incident side of the light modulating means, and the second polarizing means arranged on the light emitting side of the light modulating means. A viewfinder featuring. 2. A light generating means, a light collecting means for converting light emitted from the light generating means into substantially parallel light, and light emitted from the light collecting means is modulated so as to change the light scattering state. Light modulating means for forming an image, first polarizing means arranged on the light incident side of the light modulating means, second polarizing means arranged on the light emitting side of the light modulating means, and the light modulating means And a magnifying display means for magnifying an optical image of the means and for making the magnified optical image visible to an observer. 3. The condensing means is characterized in that the light emitted from the light generating means, incident on the effective surface area of the condensing means, and traveling straight through the light modulating means reaches the observer's pupil. The viewfinder according to claim 1 or 2. 4. The viewfinder according to claim 1, wherein the light converging means is a plano-convex lens, and the flat surface of the lens is arranged so as to face the light generating means. 5. The viewfinder according to claim 1, wherein the light converging means is a plano-convex lens, and the first polarizing means is adhered or arranged on the flat surface portion of the lens. 6. The viewfinder according to claim 1, wherein the polarization axis of the first polarization means and the polarization axis of the second polarization means are substantially in the same direction. 7. The light generating means is a fluorescent light emitting lamp or LE.
The viewfinder according to claim 1 or 2, wherein the viewfinder is D. 8. The viewfinder according to claim 1, wherein the light modulating means is a polymer dispersed liquid crystal panel. 9. The viewfinder according to claim 1 or 2, wherein an area where the light generating means emits light is smaller than an image display area of the light modulating means. 10. The viewfinder according to claim 1 or 2, wherein an eyepiece cover capable of substantially fixing the viewpoint position of the observer is arranged between the enlarged display means and the observer. 11. The viewfinder according to claim 2, wherein the magnifying display means includes a magnifying lens and a holder for holding the magnifying lens, and a distance between the magnifying lens and the light modulating means can be varied. 12. A polymer-dispersed liquid crystal of a polymer-dispersed liquid crystal panel, wherein the liquid crystal film thickness of the polymer-dispersed liquid crystal is 5 μm or more and 30 μm or less, and the average value of the particle diameter of the water droplet liquid crystal or the average value of the hole diameter of the polymer network is 0. 9. The viewfinder according to claim 8, wherein the viewfinder is 5 μm or more and 3.0 μm or less. 13. The view according to claim 1, wherein the area of the light emitting area of the light generating means and the area of the image display area of the light modulating means are 1: 200 or more and 1:20 or less. finder. 14. The viewfinder according to claim 1, further comprising a diaphragm for blocking unnecessary light from the light generating means between the light generating means and the light collecting means. 15. A diaphragm for changing a region for emitting light is provided on the light emitting surface of the light generating means.
Alternatively, the viewfinder according to claim 2. 16. A video camera using the viewfinder according to claim 1 or 2.