GB2163246A

GB2163246A - Lighting projector

Info

Publication number: GB2163246A
Application number: GB08517690A
Authority: GB
Inventors: Marcello Bertozzi
Original assignee: IANIRO QUARTZCOLOR SpA; QUARTZCOLOR IANIRO SpA
Current assignee: IANIRO QUARTZCOLOR SpA; QUARTZCOLOR IANIRO SpA
Priority date: 1984-07-13
Filing date: 1985-07-12
Publication date: 1986-02-19
Also published as: DE3524818A1; GB2163246B; DE8520110U1; FR2567622B1; FR2567622A1

Abstract

A lighting projector for diffuse illumination comprising a casing (10) with a front window (11), a lower compartment, a bottom wall, a back wall, a combination of a concentrated light source (15) and a reflecting mirror (17), the reflecting mirror (17) cooperating with the concentrated light source (15) and being a quadric surface mirror, and a diffuser mirror (12) arranged between the reflecting mirror (17) and the window (11). <IMAGE>

Description

SPECIFICATION Lighting projector The present invention relates to a lighting projector and particularly to a lighting projector for diffuse or "soft light" illumination, as used for example in theatres, photographic, motion picture and television studios, and the like.

As is well known to those who are skilled in the art, in order to obtain a diffuse illumination use is made of the so-called diffused or "soft" lighting projectors comprising a casing that incorporates a diffuser that receives both direct light from a lamp and light reflected by a mirror, the lamp being arranged so that no direct light therefrom can go out of the casing.

Lamps available at the present time and commonly employed in such lighting projectors are of an elongate shape, both in the case of incandescent lamps which are characterized by a low color temperature, and in the case of discharge lamps which are characterized by a high colour temperature.

The mirror which is also of an elongate shape, has a curved polygonal transverse profile, and reflects the light it receives directly from the lamp to the diffuser, which light would otherwise be lost on the inside wall of the lighting projector.

Generally, such lighting projectors do not suffer from substantial inefficiencies when using incandescent, low colour temperature lamps, but they become inefficient when using discharge, high colour temperature lamps or incandescent lamps with concentrated filaments.

Inefficiencies occur when a mirror of an elongate shape is used with a concentrated light source such as a discharge lamp, for which the luminous arc can be considered pointlike or an incandescent filament.

Among recent types of lighting projector there are those in which a single body mirrorand-lamp unit is used, this providing a number of advantages which will be clear from the following.

A further disadvantage of known lighting projectors is that they do not have the possibility of total dimming of the luminous intensity, or of gradually varying the intensity of the diffused light.

According to this invention there is provided a lighting projector for diffuse illumination, comprising a casing with a window, a combination of a concentrated light source and a quadric surface mirror mounted in the casing, and a diffuser mirror arranged to reflect light from said quadric surface mirror out through said window.

The present invention provides a lighting projector for diffuse illumination in which either incandescent, concentrated filament lamps or discharge lamps can be used with no detriment to the optical yield, efficiency or visual effects, or, in other words, in which both low and high colour temperature lamps can be used with no such detriments.

Also according to this invention there is provided a lighting projector for diffuse illumination, comprising a casing having a light outlet window, lower compartment, a bottom wall, a back wall and an upper panel; a first diffuser mirror mounted in said lower compartment; a second diffuser mirror mounted to direct light out through said window; and a single-body lamp and reflecting mirror unit carried by a lamp holder pivotally mounted in the casing, said unit being movable between a working position in which it cooperates directly with said first diffuser mirror, and a retroverted inoperative position.

Such a lighting projector gives the possibility of varying the intensity of the diffused light from a maximum value down to zero and vice versa, i.e. the so-called "dimming" effect can be realized.

With the lighting projector of the present invention, the lamp can be of the double-base type mounted in lamp holders arranged at opposite sides of the associated mirror, or the lamp can be of the single-base type mounted in a lamp holder arranged in front of the associated mirror or through a hole in the mirror.

A filter can be provided between the lamp and the diffuser, for example a U.V. filter in particular for discharge lamps, or lamps incorporating such filters can be used.

Further, the light beam from the lamp can be redirected by means of at least one auxiliary diffuser or reflector mirror before impinging on the main difuser.

This invention will now be described by way of example with reference to the drawings, in which: Figures 1 and 2 show schematically two lamp-mirror units according to the prior art; Figure 3 shows a schematic front view of a lighting projector according to the present invention; Figure 4 shows a side view of the lighting projector of Figure 3; Figures 5 and 6 show schematically a front view and a side view respectively of a lighting projector according to the present invention, having an elliptical mirror; Figure 7 shows a schematic side crosssection of another lighting projector according to the present invention; Figure 8 shows a detailed view of a motor used for rotating the lamp unit in the lighting projector of Figure 7; and Figure 9 shows a schematic side crosssection view of another lighting projector according to the present invention.

With reference now to Figures 1 and 2, a brief mention will be made of the prior tech niques. As can be clearly seen, lamps commonly employed are of an elongate shape, both the incandescent filament lamps, as in Figure 1, and the discharge lamps, as in Figure 2. Mirrors employed in connection with such lamps are of an elongate shape, with a curved transverse profile, as in Figure 1, or with a polygonal profile as in Figure 2.Disadvantages of such units, as already mentioned above, are evident if the observation is made that the diffuser, though curved, is of a rectangular shape across the whole width of the projector, so that whereas the use of an elongate mirror is acceptable in connection with an elongate filament lamp, as in Figure 1, such use is not acceptable in connection with a discharge lamp, as in Figure 2, or with an incandescent lamp with a filament of the concentrated type. Such mismatching is a source of poor efficiency, as well as of other inefficiencies and optical effects that are of detriment to the fitness of the device as a lighting projector for diffuse illumination, as the uniformity of the light diffusing is impaired.

When the consideration is made that incandescent filament lamps are low colour temperature lamps, typically of the of the order of 3000-3200"K, whereas discharge lamps are high colour temperature lamps, typically of the order of 5500-5600"K, it is evident that lighting projectors for diffuse illumination are not suitable for a satisfying high colour temperature illumination.

With reference now to Figures 3 and 4, the lighting projector here shown comprises a casing 10 with an upper front rectangular window 11, and with a closed bottom part, with a front wall 1 3 hinged at the bottom at 14, so that easy access is allowed to the inside.

A conventional diffuser 1 2 is arranged on the back part of the casing 10, the diffuser being of rectangular shape with a curved transverse profile, and reflecting towards the outside through the window 11, and in diffusing way, light it receives directly or indirectly from a lamp 1 5.

A mirror 1 7 is associated with the lamp 15, arranged between lamp holders 1 6A and 1 6B. The mirror 1 7 has a quadric surface, the expression "quadric surface" meaning the shape obtained by sectioning a surface such as and ellipsoid, a paraboloid or the like. For illustrative purposes, the mirror can be described as a spherical mirror. The mirror shown in Figures 5 and 6 has an elliptical profile both as seen from the front and in transverse section.

With reference now to Figure 7, the lighting projector here shown comprises a casing 10 with a small rectangular front window 11 in an upper part, a lower front wall 18 and a bottom 19, both the wall 1 8 and bottom 1 9 being closed.

The back side of the casing 10 is closed by a back wall 20 and an upper panel 21.

The bottom 19, the back wall 20 and the upper panel 21 include the commonly employed louvers which are suitably screened according to industrial regulations for allowing circulation of cooling air while at the same time preventing light from leaking out of the device.

The back wall 20 or the upper panel 21, or the back wall and the upper panel as a unit, can be hinged so that they can be opened for easy access to the lamp, for maintenance or replacement purposes.

A first diffuser mirror 22 is housed inside the casing 10, the mirror 22 being of a circular arc section, and a second diffuser mirror 23 is arranged opposed to the first mirror 22, the second mirror 23 also being of a curved section. However, a circular arc shape for the mirrors 22 and 23 is not essential; the shapes of the mirrors can be modified within certain limits, for example into an arc of an ellipse or of a parabola, or into an arc of mixed type, provided the result is obtained of diffused light emission with the highest possible degree of diffusion and uniformity out of the window 11.

As is well known, the surfaces of diffuser mirrors are worked so as to give the highest possible number of reflections. Particularly advantageous results have been obtained by finishing the surface of the first diffuser mirror 22 more coarsely than the surface of the second diffuser mirror 23.

The lamp employed in the lighting projector is of the so-called P.A.R. type which is a single body type of lamp 24 which comprises, in additon to the lamp proper (not shown in the drawing) a concave reflecting mirror with a quadric section and a protecting glass 26.

The use of such a lamp avoids the need for a supplementary glass plate for the absorption of ultraviolet rays as well as the need for a protecting net against explosions.

Moreover, as the lamps employed in such lighting projectors usually have a very short useful life, the very simple replacement operations needed for "P.A.R." lamps with a mirror incorporated are advantageous.

The lamp unit 24 is mounted on a lamp holder 27 which is in turn pivoted within the casing 1 0 of the lighting projector.

The mounting of the lamp holder 27 by pivoting at 0 inside the lighting projector casing 10 allows the whole assembly of the lamp holder 27 and the lamp 24 to be rotated from the working position shown by a full line in Figure 7 to the retroverted inoperative position shown by the dotted line.

When the lamp 24 is in the retroverted position, it is very easily accessible for maintenance and/or replacement purposes, from the back of the lighting projector, when the back wall 20 and/or the upper panel 21 are hinged so they can be opened.

Such rotation of the lamp holder is obtained in the following way and by the following means.

A toothed wheel 28 is fastened to the lamp holder 27, the wheel 28 engaging with a toothed wheel 29 that is rotated through a 90 transmission coupling, for example a bell device 30.

The bell device 30 which is described in Italian Patent No. 884.552, is a device that allows the remote control of suspended lighting projectors. The device consists of a bell member with a cross member inside which can engage with a hook borne by a perch.

When the bell member is rotated, the toothed wheel 29 is rotated through a 90 bevel gear pair and through the wheel 29 rotation of the toothed wheel 28 is obtained and with it rotation of the lamp holder 27 which is integral with the wheel 28, and thus rotation of the whole lamp unit 24.

The gear ratio of the 90 bevel gear pair and of the two toothed wheels 29 and 28 is not critical, but is such as to allow easy movement of the lamp unit 24 from the working position to the retroverted position.

The diffuser mirror 23 must be suitably cut in its lower part in order to allow passage of the lamp 24 during movement thereof.

In the case of remote control obtained through a cord or through a radio control unit or ultrasonic units or the like, the bell device 30 can be replaced by a small electric motor 30A (Figure 8) which acts through a 90 bevel gear pair and a toothed wheel 29A on a toothed wheel 28A which is integral with the lamp holder.

In the lighting projector shown in Figure 9 the second diffuser mirror is not realized with a single curved member as found in the embodiment of Figure 7, but is formed with two sectors, these being an upper curved sector 23A and a lower planar sector 23B. In this construction it is the lower planar sector 23B of the diffuser mirror that is to be suitably cut in order to allow passage of lamp 24 during rotation thereof from the working positon to its retroverted inoperative position.

A very important aspect of this lighting projector is that in the working position shown by the full line, the whole luminous flux from the lamp 24 is conveyed onto the first diffuser 22 and then onto the second diffuser 23 or 23A, 23B and therefore to the outside through the window 11, whereas in the inoperative or retroverted position shown by the dotted line, the luminous flux that goes out of the window 11 is almost zero, the flux taking on values intermediate the nominal maximum value and zero as the lamp rotates from the working position to the retroverted position.

Thus, by rotating the lamp it is possible to obtain a gradual variation of the luminous intensity of the projector from the maximum intensity value to zero value (i.e., the so-called dimming effect) as well as from the zero to the maximum value.

In the retroverted positon with full dimming, i.e. with practically zero value of the luminous intensity from the window 11, the lamp 24 is in the positon of optimal loss of heat produced, so that the problem is eliminated that is met with other dimming arrangements, in which the worst conditions of heat loss occur at the full dimming position.

Claims

1. A lighting projector for diffuse illumination, comprising a casing with a window, a combination of a concentrated light source and a quadric surface mirror mounted in the casing, and a diffuser mirror arranged to reflect light from said quadric surface mirror out through said window.

2. A lighting projector according to Claim 1, wherein said combination of a concentrated light source and a quadric surface mirror is an integral unit.

3. A lighting projector according to Claim 1 or Claim 2, wherein the casing has a bottom compartment with a front wall hinged to allow easy access to said combination.

4. A lighting projector according to any preceding claim, including at least one auxililary diffuser or reflector arranged between the quadric surface mirror and said diffuser mirror.

5. A lighting projector for diffuse illumination, comprising a casing having a light outlet window, lower compartment, a bottom wall, a back wall and an upper panel; a first diffuser mirror mounted in said lower compartment; a second diffuser mirror mounted to direct light out through said window; and a single-body lamp and reflecting mirror unit carried by a lamp holder pivotally mounted in the casing, said unit being movable between a working position in which it cooperates directly with said first diffuser mirror, and a retroverted inoperative position.

6. A lighting projector according to Claim 6, wherein with said unit in said working position the output luminous flux from said window is of maximum value, and with said unit in said retroverted inoperative positon the output luminous flux from said window is practically of zero value, the output luminous flux having intermediate values for intermediate positions of said unit.

7. A lighting projector according, to Claim 5 or Claim 6, wherein said diffuser mirrors have rectangular surfaces with a curved section profile.

8. A lighting projector according to Claim 6 or Claim 7, wherein said second diffuser mirror comprises a first upper sector with a rectangular surface and curved section profile, and a second, planar surface, lower sector.

9. A lighting projector according to any one of Claims 5 to 8, wherein said second diffuser mirror is cut in order to allow said unit to pass.

10. A lighting projector according to any one of Claims 5 to 9, including means to rotate said unit comprising a toothed wheel fastened to said lamp holder, said wheel engaging with a second toothed wheel that is driven by way of a gear arrangement by a rotation device.

11. A lighting projector according to Claim 10, wherein said rotation device comprises an electric motor.

12. A lighting projector according to any one of Claims 5 to 11, wherein said back wall and/or said upper panel form a hinged door for access to said unit when in the retroverted inoperative position.

1 3. A lighting projector for diffuse illumination substanially as hereinbefore described with reference to Figures 3 and 4, Figures 5 and 6, Figures 7 and 8 or Figure 9 of the drawings.