JP5036229B2 - Visibility correction filter glass and visibility correction filter - Google Patents

Description

  The present invention is used in color correction filters for digital still cameras (hereinafter referred to as DSCs), color video cameras, and the like, and transmits the visible region and corrects the visibility with a sharp cut characteristic and a near ultraviolet cut characteristic near 700 nm. It relates to filter glass.

Conventionally, solid-state imaging devices such as CCDs and CMOSs used in DSCs and color video cameras have spectral sensitivity ranging from the visible region to the near infrared region near 1100 nm. Therefore, since good color reproducibility cannot be obtained as it is, it is necessary to correct to normal human visibility using a filter that absorbs the infrared region. This filter uses a filter glass in which CuO is added to a phosphate glass or a fluorophosphate glass so as to selectively absorb near-infrared wavelengths. This filter glass contains CuO containing a large amount of P ₂ O ₅ as an essential component, and exhibits a blue-green color by forming Cu ²⁺ ions coordinated to a large number of oxygen ions in an oxidizing molten atmosphere. It has a near infrared cut characteristic.

  Among the filter glasses, phosphate-based glass has insufficient weather resistance, so it causes weathering on the polished glass surface. System glass is mainly used.

As a near-infrared cut filter glass made of CuO-fluorophosphate glass, one described in Patent Document 1 is known. In order to suppress a decrease in transmittance around 400 nm in the glass of Patent Document 1, Sb ₂ O ₃ , Also known are those described in Patent Documents 2 and 3 containing a small amount of As ₂ O ₃ , CeO ₂ or the like.

Japanese Patent Laid-Open No. 1-219037 JP-A-2-204342 JP 2004-137100 A

As described above, a solid-state imaging device such as a CCD or CMOS has a spectral sensitivity ranging from the visible region to the near infrared region near 1100 nm, and also has sensitivity in the near ultraviolet region. The transmittance curve of a fluorophosphate glass filter containing Cu ²⁺ ions as described in the above patent document does not transmit a wavelength of approximately 300 nm or less, and the transmittance increases rapidly in the wavelength range of 300 nm to 400 nm, It is a curve that gradually falls from 600 nm to 700 nm. When the transmittance in the visible region is set to a certain level or more, it has a characteristic of slightly transmitting the longer wavelength side exceeding 900 to 1000 nm. For this reason, it may be difficult to make the human visibility and the color reproducibility of the photographed image completely coincide with each other only by absorption by the glass filter.

In such a case, the near-ultraviolet region and the near-infrared region are further cut by using a dielectric multilayer film in combination. The dielectric multilayer film is composed of an alternating laminated film of titanium dioxide (TiO ₂ ) as a high refractive index layer and silicon dioxide (SiO ₂ ) as a low refractive index layer, and is formed on the surface of a near infrared cut filter glass. In some cases, a low-pass filter may be formed by vacuum deposition or sputtering on the surface of a crystal plate built in the camera. The transmission characteristic of the infrared cut film by the dielectric multilayer film is that light having a wavelength of about 400 nm or less and 700 nm or more is reflected and hardly transmitted, and 400 to 700 nm is transmitted with respect to light incident perpendicularly to the film formation surface. . As a result, in an optical system that combines absorption by a glass filter and reflection by a dielectric multilayer film, a transmittance curve that transmits 400 to 600 nm at a high rate, gradually decreases from 600 to 700 nm, and does not transmit 700 nm or more. The characteristics can be drawn and approximated to human visibility.

  By the way, in recent years, in a DSC or the like using an image sensor with a large number of pixels, a purple outline blur called purple fringe is recognized in a photographed image due to chromatic aberration of a lens system. . In other words, the refractive index of a medium such as glass that constitutes an optical element has a property that depends on the wavelength of light, and even for the same medium, the refractive index for visible light, the refractive index for near ultraviolet light, and the refraction for near infrared light. It is different from the rate. Due to this property, when light passes through the glass optical element, the shorter wavelength light is refracted more strongly, and the longer wavelength light is less refracted. The infrared optical path is branched, and near ultraviolet rays are focused on the near side and near infrared rays are focused on the rear side relative to the focal position of visible light (axial chromatic aberration). At the position where the light beam branched in this way reaches the photoelectric conversion surface of the image sensor, the chromatic aberration becomes a two-dimensional deviation, and this deviation becomes a blur radius due to near ultraviolet rays or near infrared rays, thereby generating contour blur. Cause. In particular, in an image sensor with a high pixel count, the influence of chromatic aberration is easily recognized as the pixel size is reduced, and the influence is more likely to occur in the peripheral part than in the center part of the captured image. In other words, the problem of contour blur due to chromatic aberration can be said to be a problem that has become apparent as the number of pixels of the image sensor increases.

  The above-mentioned dielectric multilayer film cuts light in the ultraviolet region and infrared region by reflection, but the dielectric multilayer film changes its reflection characteristics depending on the incident angle of the light beam, so that it transmits light incident on the film surface perpendicularly. Even light with a wavelength of 0 may not be completely reflected with respect to obliquely incident light and may be transmitted. For this reason, an image sensor that has sensitivity to near ultraviolet rays and near infrared rays cannot eliminate blurring due to chromatic aberration, and an effect tends to be exerted on an image peripheral portion where light incident on the image sensor obliquely increases. In addition, when the light reflected by the dielectric multilayer film becomes stray light in the optical system and enters the dielectric multilayer film obliquely again, it reaches the photoelectric conversion surface of the image sensor and changes the color of the photographed image such as false color. It will cause disturbance.

  Therefore, if light in the ultraviolet region or infrared region can be cut by glass absorption without relying on the dielectric multilayer film, the adverse effects can be eliminated even if these unnecessary lights are incident obliquely. As the method, since the above-mentioned CuO-fluorophosphate glass originally has absorption in the ultraviolet region, it is conceivable to increase the amount of CuO added in order to enhance absorption in the near ultraviolet region. FIG. 7 shows a transmittance curve of a conventional CuO-fluorophosphate glass in which the amount of CuO added is changed. This is a comparative glass to be described later, in which curve 19 is added with 2 parts by mass of CuO and curve 20 is added with 5 parts by mass of CuO with respect to 100 parts by mass of the mother glass made of fluorophosphate glass. is there. As can be seen from FIG. 7, when the amount of CuO added is increased, the absorption in the near infrared region increases with the absorption in the near ultraviolet region, and the cut pattern of 600 to 700 nm moves to the short wavelength side. That is, the cut characteristics in the near-ultraviolet region and the near-infrared region cannot be controlled independently only by changing the CuO addition amount.

  The near-ultraviolet or near-infrared cut pattern of the visibility correction filter that is actually used in DSCs and video cameras is determined according to the sensitivity characteristics of each CCD or CMOS or the design of the camera. It is desirable that the cut characteristic in the ultraviolet region and the cut characteristic in the near infrared region can be controlled independently.

  The present invention has been made in consideration of such circumstances, and a filter glass used for correcting the visibility of a solid-state imaging device has a near-ultraviolet absorption characteristic, and a near-infrared absorption characteristic and a near-ultraviolet absorption characteristic. The object is to provide glass that can be changed independently. It is another object of the present invention to provide a visibility correction filter that can reduce disturbances in a captured image such as blurring due to near-ultraviolet chromatic aberration of a lens system.

In order to solve the above-mentioned problems, the present invention provides a group consisting of Fe ₂ O ₃ , MoO ₃ , WO ₃ and CeO _{2 in} an outer ratio with respect to 100 parts by mass of the base glass made of CuO-fluorophosphate glass. A visual sensitivity correction filter glass comprising the following effective amount of at least one selected from: The effective amounts of Fe ₂ O ₃ , MoO ₃ , WO ₃ and CeO ₂ are as follows: Fe ₂ O ₃ is 0.6 to 5 parts by mass, MoO ₃ is 0.5 to 5 parts by mass, and WO ₃ is 1 to 6 parts by mass. Part, CeO ₂ is 2.5 to 6 parts by mass. Also, the base glass is, by _mass%, P 2 _{O 5}
10-60%, AlF ₃ 0-20%, RF (R is at least one of Li, Na, K) 1-30%, R′F ₂ (R ′ is at least of Mg, Ca, Sr, Ba) 1 type)
10% to 75% (however, up to 70% of the total amount of fluoride can be replaced with oxide), 100% by weight of the mother glass is 90% or more. It contains 12 parts by mass.

When two or more components selected from the group consisting of Fe ₂ O ₃ , MoO ₃ , WO ₃ and CeO ₂ are contained, the total amount is up to 10 parts by mass with respect to 100 parts by mass of the basic glass. It is preferable to be in the range.

  Furthermore, the present invention is a visibility correction filter made of the glass.

  Since the glass of the present invention can absorb near ultraviolet rays in addition to the absorption characteristics of near infrared rays, unnecessary ultraviolet rays do not reach the image sensor in the imaging optical system, and outline blurring and stray light ultraviolet rays caused by near ultraviolet chromatic aberration are prevented. It is possible to reduce the disturbance of the captured image due to the above. In addition, since the near-UV cut characteristics and near-infrared cut characteristics can be controlled independently, it is possible to provide filters with characteristics that match the image sensor used in combination with the glass of the present invention, and color reproduction of the image sensing device. It is useful for improving the performance.

The present invention achieves the above-mentioned object by the above-described configuration, and the reason for limiting the content of each component constituting the glass of the present invention as described above will be described below.

First, the reason why the CuO-fluorophosphate glass is used as the basic glass is that, as described above, the absorption characteristics in the near-infrared region due to Cu ²⁺ ions coordinated to oxygen ions are necessary for correcting the visibility.

Since Fe ₂ O ₃ , MoO ₃ , WO ₃ and CeO ₂ exhibit absorption in the ultraviolet region in the fluorophosphate glass, at least one of them is contained in a predetermined amount as an ultraviolet absorbing component. It is preferable that the content of each component is indicated as an outer ratio with respect to 100 parts by mass of the basic glass and is within the above range.

If Fe ₂ O ₃ is less than 0.6 parts by mass, the absorption effect in the near-ultraviolet region is not sufficient, and if added over 5 parts by mass, it becomes difficult to melt in the glass, and absorption also appears in the visible region. The transmittance decreases. Preferably it is 1-3 mass parts.

If MoO ₃ is less than 0.5 part by mass, the absorption effect in the near-ultraviolet region is not sufficient, and if it is added in excess of 5 parts by mass, it becomes difficult to melt into glass. Preferably it is 1-3 mass parts.

When WO ₃ is less than 1 part by mass, the expected effect cannot be obtained, and when it is added in excess of 6 parts by mass, it is difficult to melt into glass. Preferably it is 3-5 mass parts.

When these three components are added in an increased amount, unmelted parts are generated, causing glass defects. Increasing the melting temperature of the glass can eliminate the remaining melting, but an increase in the melting temperature is not preferable because it makes Cu ²⁺ ions in the glass unstable and the desired absorption characteristics cannot be obtained.

When CeO ₂ is less than 2.5 parts by mass, the absorption effect in the near-ultraviolet region is small, and when it exceeds 6 parts by mass, the glass tends to devitrify. Preferably it is 3-5 mass parts.

  In addition, the said ultraviolet absorption component can also be contained in combination of 2 or more type. In this case, the total amount is preferably in the range of up to 10 parts by mass with respect to 100 parts by mass of the basic glass. When the total amount exceeds 10 parts by mass, unmelted parts are generated, or depending on the combination, absorption in the visible region is increased and the visible transmittance is lowered.

Next, components constituting the basic glass will be described. P ₂ O ₅ is a main component that forms a network structure of glass, but if it is less than 10%, vitrification is difficult, and if it exceeds 60%, chemical durability is lowered, and there is a concern about the influence of weathering in long-term use. Is done. Preferably it is 20 to 50%.

AlF ₃ is an effective component for improving the chemical durability of the glass, but if it exceeds 20%, the meltability of the glass decreases. Preferably it is 1 to 15%.

  LiF, NaF, and KF shown as RF are effective components for introducing fluorine into glass and lowering the melting temperature and viscosity. However, when the total amount of RF is less than 1%, the effect cannot be obtained. If it exceeds 50%, the chemical durability is remarkably lowered. Preferably it is 5 to 25% of range.

MgF ₂ , CaF ₂ , SrF ₂ , and BaF ₂ shown as R′F ₂ are effective in stabilizing the glass without reducing chemical durability, but the total amount of R′F ₂ is 10 If it is less than%, it is difficult to vitrify, and if it exceeds 75%, the tendency to devitrify becomes remarkable. Preferably it is 20 to 60% of range.

  Moreover, even if up to 70% of the total amount of metal fluoride constituting the mother glass is replaced with a metal oxide, desired spectral characteristics and chemical durability can be obtained.

As described above, a glass having a total of 90% or more of components composed of P ₂ O ₅ , AlF ₃ , RF, and R′F ₂ (including a metal oxide substituted with a metal fluoride) is referred to as a mother glass in the present invention. The mother glass can be a glass composed of the above components, but in addition to the above components, materials that do not impair the properties of the visibility correction filter glass, such as ZnF ₂ , ZrF ₄ , LaF ₃ , Sb ₂ O ₃ , It can be contained in the range of up to 10% for the purpose of improving the weather resistance and meltability of the glass and adjusting the thermal expansion coefficient.

  CuO is an essential component for cutting near-infrared rays, but it is an outer split with respect to 100 parts by mass of the mother glass, and if it is less than 0.5 parts by mass, the near-infrared absorbing effect is not sufficient, and if it exceeds 12 parts by mass. The transmittance in the visible range is also lowered, and the glass becomes unstable and devitrification increases. Preferably it is 1-10 mass parts. In general, in the visibility correction in a DSC or color video camera, a cut pattern in which the wavelength at which the transmittance is 50% in the near infrared region is in the range of 590 nm to 670 nm, and in many cases is in the range of 610 nm to 650 nm, is preferably used. Further, in order to ensure good color reproducibility and incident light quantity, the transmittance at a wavelength of 500 nm is at least 80% or more, more preferably 85% or more, for a single glass not coated with an antireflection film or the like. preferable. On the other hand, in order to reduce the influence of near-ultraviolet rays with which the image sensor has sensitivity, the wavelength at which the transmittance is 50% in the near-ultraviolet spectral transmittance is on the long wavelength side of 360 nm or more, more preferably 370 nm or more. It is preferable.

The glass of the present invention can be produced as follows. First, the raw materials are weighed and mixed so that the obtained glass has the above composition range. This raw material mixture is placed in a platinum crucible, covered, and heated and melted at a temperature of 700 to 1000 ° C. in an electric furnace. After sufficiently stirring and clarifying, it is cast into a mold, slowly cooled, then cut and polished to form a flat plate having an inner thickness of about 0.1 to 1 mm. Increasing CuO tends to make the glass unstable and easily devitrified. However, when melting with a crucible, the crucible is sealed with a lid made of platinum or the like to suppress the volatilization of the fluorine component, and within the crucible In order to eliminate the stagnation of the glass, devitrification of the glass can be suppressed by devising and strengthening the glass stirring method. The glass of the present invention does not cause any striae that cannot be removed in the subsequent polishing process through the melting and forming processes, and an optically homogeneous glass can be obtained.

  The visibility correction filter of the present invention is obtained by shaping the glass prepared as described above into a thin plate that has been subjected to mechanical processing such as cutting, grinding, polishing, and chamfering and finally optically polished on both sides. is there. This visibility correction filter is made of the glass and has absorption characteristics in the near infrared and near ultraviolet, so that the visibility correction for the image sensor can be performed. Appropriate transmission characteristics can be obtained for the thickness of the filter used in combination with the glass composition such as the content of CuO, which is a near-infrared absorbing material, and the content of an ultraviolet absorber, depending on the required characteristics on the side of the image sensor to be combined. It is used as adjusted. In a general DSC, the thickness is about 0.1 to 1 mm, preferably about 0.2 to 0.5 mm. As a usage mode of the filter, the visibility correction filter of the present invention is sandwiched between two quartz plates, bonded to only one side, or bonded to optical glass. it can. Further, an optical multilayer film such as an antireflection film or an ultraviolet cut film can be formed on the surface of the filter as required by a known means such as vacuum deposition.

  Since the filter of the present invention is mainly used for correcting the visibility of a solid-state imaging device, it is used by being disposed on the optical path between the imaging lens of the imaging device and the imaging device, and absorbs the near infrared rays and the near ultraviolet rays. Good visibility correction can be performed according to the characteristics, and generation of false colors and the like can be suppressed. Further, since the glass of the present invention has excellent weather resistance, weathering is hardly generated in the glass, and good optical characteristics can be maintained over a long period of time.

Next, the glass of this invention is demonstrated in detail based on an Example. No. in Table 1 and Table 2. 1-18, Examples of the present invention, No. 19 and 20 show comparative examples showing conventional glass. In addition, the composition in a table | surface shows a mother glass part by the mass%, shows CuO content by the outer part with respect to 100 mass parts of mother glasses, and 100 mass of basic glasses which consist of mother glass and CuO as a component added as a ultraviolet absorber. It is shown as an external division for the part. The glass described in the table was weighed and mixed with the raw material powder so as to have the composition shown in the table, and melted at a temperature of 700 to 1000 ° C. using a platinum crucible. Then, the glass that has been sufficiently stirred and clarified is poured into a rectangular frame, sliced to a thickness of about 1 mm after slow cooling, and cut into 11 mm × 11 mm sizes, and fixed to the surface plate of the polishing apparatus 300 sheets at a time. Then, polishing was performed using cerium oxide as an abrasive to a thickness of 0.3 mm.

  Spectral transmittance was measured for the flat glass prepared as described above. Spectral transmittance is measured by using a UV-IR spectrophotometer V-570 manufactured by JASCO Corporation, which uses a diffraction grating in the optical system, and the glass is not coated with an antireflection film or the like. The rate was measured. As a result, the wavelengths at which the transmittance on the ultraviolet side of each Example and Comparative Example glass is 50% are shown in Tables 1 and 2, and the spectral transmittance curves of some examples are shown.

In FIG. 1 and no. 2 and Comparative Example No. The spectral transmittance curves of 19 glasses are shown as curves 1, 2 and 19. These three samples have the same CuO content, and the example glass contains Fe ₂ O ₃ as an ultraviolet absorber. Since the CuO content is the same, the cut pattern on the near-infrared side shows almost the same characteristics, but the near-ultraviolet side has a remarkable absorption of the example glass, and the wavelength at which the transmittance on the ultraviolet side shows 50%. It can be seen that is shifted to the longer wavelength side compared to the comparative example.

In FIG. 3 and no. 4 and Comparative Example No. The spectral transmittance curves of 19 glasses are shown as curves 3, 4 and 19. These three samples have the same CuO content, and the example glass contains MoO ₃ as an ultraviolet absorber. Since the CuO content is the same as in FIG. 1, the cut pattern on the near infrared side shows almost the same characteristics, but the absorption range on the near ultraviolet side is expanded in the example glass.

In FIG. 5 and no. 6 and Comparative Example No. The spectral transmission curves of 19 glasses are shown as curves 5, 6 and 19. These three samples have the same CuO content, and the example glass contains WO ₃ as an ultraviolet absorber. Since the CuO content is the same as in FIG. 1, the cut pattern on the near infrared side shows almost the same characteristics, but the wavelength at which the transmittance on the ultraviolet side shows 50% is higher in the example than in the comparative example. It is shifted to the long wavelength side.

In FIG. 9 and no. The spectral transmission curves of 14 glasses are shown as curves 9 and 14. Example No. The glass of No. 9 contains Fe ₂ O ₃ and MoO ₃ . 14 glass contains WO ₃ and CeO _2. As in this example, the absorption characteristics in the near-ultraviolet region can be changed even when an additive component as an ultraviolet absorber in the present invention is used in combination.

In FIG. 7 and Comparative Example No. The spectral transmittance curves of 20 glasses are shown as curves 7 and 20. Comparative Example No. The glass No. 20 contains 5 parts by mass of CuO. The glass No. 7 contains ₂ parts by mass of CuO and 3 parts by mass of CeO ₂ . From the wavelength at which the transmittance on the ultraviolet side in FIG. 4 and Table 1 and Table 2 shows 50%, the cut pattern in the near ultraviolet region shows almost the same characteristics, but the absorption characteristics in the near infrared region are greatly different. .

FIG. The spectral transmittance curves of glasses 8 and 18 are shown as curves 8 and 18. In these, the CeO ₂ content is the same and the CuO content is changed. This also shows that the cut pattern in the near ultraviolet region shows almost the same characteristics from the wavelength at which the transmittance on the ultraviolet side in FIG. 4 and Tables 1 and 2 shows 50%, but the absorption characteristics in the near infrared region are the same. It is very different. Thus, the absorption characteristic on the infrared side can be adjusted mainly by the CuO content.

In addition, as a weather resistance test of the polished glass sample of each Example, it was kept under the conditions of a temperature of 60 ° C. and a relative humidity of 95%, and the time until the surface of the glass was altered was measured. As a result, it was judged that the glass of this example was able to withstand actual use without any change in the surface even after 1000 hours.

  FIG. 8 shows an example in which the visibility correction filter glass of the present invention is applied to an imaging optical system such as DSC. FIG. 8 is a cross-sectional view schematically showing an example of the configuration of the imaging optical system. The imaging optical system 30 is packaged via a photographing lens 31 for forming an image of a subject, a visual sensitivity correction filter 32, an optical low-pass filter 33 made of a quartz plate, etc., and a cover glass 34 with the same optical axis. An image sensor 36 enclosed in 35 is disposed. The subject light image formed on the photoelectric conversion surface 361 of the image sensor 36 by the photographing lens 31 is photoelectrically converted and output as an electrical video signal. The visibility correction filter 32 is made of the glass according to the present invention described above, and has a characteristic of transmitting visible light and absorbing near infrared rays and near ultraviolet rays.

  When a light beam is incident on such an imaging optical system 30, the refractive index for visible light and the refractive index for near ultraviolet light of the photographing lens 31 are different, so that the optical path V of visible light and the optical path U of near ultraviolet light are illustrated. In an imaging optical system that branches in this manner and does not have a near-ultraviolet cut filter on the optical path, near-ultraviolet rays reach the image sensor 36 via optical paths U and U ′. As a result, in the photoelectric conversion surface 361 of the image sensor 36, a shift indicated by L in the drawing occurs. Since a general image sensor has sensitivity to near ultraviolet rays, the deviation L is recorded as an outline blur in an image.

  In the imaging optical system 30 using the visibility correction filter 32 according to the present invention, visible light can be substantially transmitted and light having a wavelength of near-ultraviolet light or less can be substantially absorbed. Near-ultraviolet rays that have reached the conversion surface 361 but branched into the optical path U are absorbed by the visibility correction filter 32 and do not reach the photoelectric conversion surface 361, and remove chromatic aberration caused by optical elements such as lenses. It is possible to reduce deterioration in image quality such as outline blur and false color in a captured image.

  At this time, when the central light beam reaching the center of the image sensor 36 is compared with the peripheral light beam reaching the periphery of the image sensor 36, the peripheral light beam contains more rays incident obliquely. The near-ultraviolet ray absorption amount of the filter 32 is such that as the length of the optical path through which the light passes through the filter increases, more light is absorbed. In this case, the optical path length is longer, and the peripheral light beam can absorb more light rays having a wavelength shorter than the near ultraviolet ray than the central light beam.

  The deviation L due to the chromatic aberration described above increases as the angle formed by the light beam with respect to the optical axis increases. Therefore, the chromatic aberration generated by near ultraviolet rays or the like increases toward the periphery of the photoelectric conversion surface 361, but as described above, it is oblique. Since the amount of absorption of near-ultraviolet rays by the visibility correction filter 32 increases as the peripheral light flux contains more light rays incident on the light, the influence of chromatic aberration can be effectively removed.

  In addition, for example, when an ultraviolet cut film made of a dielectric multilayer film is formed on the surface of the visibility correction filter 32 on the photographing lens 31 side, ultraviolet rays incident obliquely with respect to the film formation surface are reflected by the ultraviolet cut film. Even if it is transmitted without being transmitted, it is effectively absorbed by the visibility correction filter 32 as described above, so that it is possible to prevent or suppress the arrival of light having a wavelength of near-ultraviolet light or less to the photoelectric conversion surface 361. .

  Note that the configuration of the imaging optical system shown in FIG. 8 is an example. For example, even if there is a change such as sandwiching the visibility correction filter between two quartz plates or replacing it with a cover glass, The effect of the visibility correction filter according to the invention does not change.

  As described above, the glass of the present invention can absorb not only near-infrared rays but also near-ultraviolet rays. By adjusting the contents of CuO and ultraviolet-absorbing components, the near-ultraviolet region cut characteristics and near-infrared region cuts can be achieved. The characteristics can be controlled independently. Even when the dielectric multilayer film is used in combination when the desired spectral characteristics cannot be obtained only by the absorption characteristics of the glass, when the glass of the present invention is used, the near-ultraviolet region due to the glass is higher than that of the conventional glass. Since the amount of absorption of unnecessary light is increased, the influence of light incident obliquely on the dielectric multilayer film formation surface described above can be suppressed to a low level.

As described in detail above, the glass according to the present invention can selectively and effectively absorb and remove infrared rays and ultraviolet rays which are unnecessary for the image sensor, so that color reproducibility of an imaging device such as a DSC or a color video camera can be obtained. It is useful for improvement and is suitable as a visibility correction filter used in these imaging devices.

Example No. 5 according to the present invention. 1, no. 2 and Comparative Example No. It is a curve figure which shows the spectral transmittance curve of 19 glasses. Example No. 5 according to the present invention. 3, no. 4 and Comparative Example No. It is a curve figure which shows the spectral transmittance curve of 19 glasses. Example No. 5 according to the present invention. 5, no. 6 and Comparative Example No. It is a curve figure which shows the spectral transmittance curve of 19 glasses. Example No. 5 according to the present invention. 9, no. It is a curve figure which shows the spectral transmittance curve of 14 glass. Example No. 5 according to the present invention. 7 and Comparative Example No. It is a curve figure which shows the spectral transmittance curve of 20 glass. Example No. 5 according to the present invention. 8, no. It is a curve figure which shows the spectral transmittance curve of 18 glasses. Comparative Example No. 19 and No. It is a curve figure which shows the spectral transmittance curve of 20 glass. It is typical sectional drawing which shows the structure of the imaging optical system to which the visibility correction filter glass which concerns on this invention is applied.

Explanation of symbols

1 Example glass No. 1 No. 1 spectral transmittance curve, 2. No. 2 spectral transmittance curve, 3. No. 3 spectral transmittance curve, 4. No. 4 spectral transmittance curve, 5 ... Example glass No. 4 No. 5 spectral transmittance curve, 6. No. 6 spectral transmittance curve, 7. No. 7 spectral transmittance curve, 8. No. 8 spectral transmittance curve, 9. No. 9 spectral transmittance curve, 14 Example glass No. No. 14 spectral transmittance curve, 18. No. 18 spectral transmittance curve, No. 19 Comparative glass No. 19 spectral transmittance curve, 20... Comparative glass No. 20 spectral transmittance curve, 30 ... imaging optical system, 31 ... lens, 32 ... visibility correction filter, 33 ... optical low-pass filter, 34 ... cover glass, 36 ... imaging device, 361 ... photoelectric conversion surface

Claims (4)

The following effective amount of at least one selected from the group consisting of Fe ₂ O ₃ , MoO ₃ , WO ₃ and CeO _{2 is included in} an outer ratio with respect to 100 parts by mass of the base glass made of CuO-fluorophosphate glass. The basic glass is P ₂ O _{5 by} mass%.
10-60%, AlF ₃ 0-20%, RF (R is at least one of Li, Na, K) 1-30%, R′F ₂ (R ′ is at least of Mg, Ca, Sr, Ba) 1 type)
10% to 75% (however, up to 70% of the total amount of fluoride can be replaced with oxide), 100% by weight of the base glass is 90% or more, and CuO 0.5% Visibility correction filter glass characterized by containing 12 parts by mass .
Fe ₂ O ₃ 0.6-5 parts by mass MoO ₃ 0.5-5 parts by mass WO ₃ 1-6 parts by mass CeO ₂ 2.5-6 parts by mass 2. Two or more components selected from the group consisting of Fe ₂ O ₃ , MoO ₃ , WO ₃ and CeO ₂ are contained in a range of up to 10 parts by mass with respect to 100 parts by mass of the basic glass. The visibility correction filter glass according to claim 1. The visibility correction filter glass according to claim 1 or 2, which is used for visibility correction of a solid-state imaging device. Visibility correction filter consisting visibility correction filter glass according to any one of claims 1 to 3.

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