WO2008002302A1

WO2008002302A1 - System for measuring light levels from a display projector

Info

Publication number: WO2008002302A1
Application number: PCT/US2006/025045
Authority: WO
Inventors: Michael Allan Sterling; Robert Harry Heath
Original assignee: Thomson Licensing
Priority date: 2006-06-27
Filing date: 2006-06-27
Publication date: 2008-01-03

Abstract

A system for measuring light levels from a display projector comprises a projection screen (2), a display projector (4), and a light measuring device (3). The projection screen has a front surface with a light measuring area (10). The display projector has a light source (22) that projects about 100 percent white light on the light measuring area. The light measuring device measures the intensity of the white light on the light measuring area. The light source is then adjusted depending on the measurement of the intensity of the white light on the light measuring area.

Description

SYSTEM FOR MEASURING LIGHT LEVELS FROM A DISPLAY PROJECTOR

Field of the Invention The invention relates to a system for measuring light levels from a display projector.

More specifically, the invention relates to a system for measuring light levels incident on a projection screen such that adjustments may be made to the display projector to optimize the quality of the image projected from the display projector onto the projection screen.

Background of the Invention

A typical display projector, which is used in both commercial and non-commercial cinema environments, contains a light source that projects an image onto a projection screen. Variations in the intensity of the light source, however, can have a negative effect on the perceived quality of the image viewed on the projection screen. Variations in the intensity of the light source may occur, for example, as the light source ages within the display projector.

In order to solve this problem, sophisticated lamp control modules have been developed that adjust the intensity of the light source as the light source ages using a servo loop feedback mechanism. These servo loop feedback mechanisms increase the amount of current to the light source and/or adjust the position of the light source relative to a reflector to maintain a constant intensity. The intensity of the light source is adjusted based on the intensity of the light source when it was first installed in the display projector compared to feedback from a photo sensor arranged in a path of the light source. Another method includes taking light measurements at a point in the projector at a pick off point and then adjusting the intensity of the light source in response to the light measurements. One such system is known as a constant light output control and can be found in the Barco DPlOO digital cinema projector. This method provides only a crude estimate of the intensity of the light source as applied to the image on the projection screen, because no feedback occurs based on the actual brightness of the image projected on the projection screen.

Summary of the Invention

The invention provides a system for measuring light levels from a display projector comprising a projection screen, a display projector, and a light measuring device. The projection screen has a front surface with a light measuring area. The display projector has a light source that projects about 100 percent white light on the light measuring area. The light measuring device measures the intensity of the white light on the light measuring area. The light source is then adjusted depending on the measurement of the intensity of the white light on the light measuring area.

Brief Description of the Drawings

Figure 1 is a schematic illustration of a light level measuring system according to a first embodiment of the invention.

Figure 2 is schematic illustration of a projection screen. Figure 3 is a schematic illustration of a control panel of a receiver. Figure 4 is a schematic illustration of a graphing display of the receiver.

Figure 5 is a flowchart showing a method of operation of the system. Figure 6 is a schematic illustration of a light level measuring system according to a second embodiment of the invention. Figure 7 is a schematic illustration of an exemplary test pattern for use in the system of Figure 1 or Figure 6.

Detailed Description of the Invention Figure 1 shows a light level measuring system 1 according to a first embodiment of the invention. As shown in Figure 1, the light level measuring system 1 includes a projection screen 2, a light measuring device 3, a display projector 4, and a receiver 12. The projection screen 2 and the light measuring device 3 are arranged in a first area 5, such as an auditorium. The display projector 4 and the receiver 13 are arranged in a second area 6, such as a projection booth. The first and second areas 5, 6 are separated by a divider 7, such as a sheet of glass.

As shown in Figures 1-2, the projection screen 2 comprises a substantially rectangular sheet 8. The sheet 8 is provided with a plurality of perforations 24 (only an exemplary amount of the perforations 24 are shown in Figure 2) that extend from a front surface 15 to a rear surface 16 thereof. The perforations 24 may have, for example, a diameter of about 1.22 millimeters. The sheet 8 includes a border 9 and a substantially centrally located light measuring area 10. The light measuring area 10 comprises about 2 percent of the sheet 8. In the illustrated embodiment, the light measuring area 10 has a substantially square geometrical configuration, however, it will be appreciated by those skilled in the art that other geometrical configurations are possible.

As shown in Figure 1 , the light measuring device 3 is mounted in the first area 5 adjacent to the divider 7. In the illustrated embodiment, the light measuring device 3 is mounted in the first area 5, however, it will be appreciated by those skilled in the art that that the light measuring device 3 may alternatively be mounted in the second area 6. The light measuring device 3 includes a lens 11 and photo-optic light measuring electronics (not shown). The lens 11 is focused toward the light measuring area 10 on the front surface 15 of the projection screen 2. The light measuring device 3 is coupled to the receiver 12. The light measuring device 3 may communicate with the receiver 12, for example, via a standard interface (not shown), such as an Institute of Electrical & Electronics Engineers (IEEE) 488, or a wireless transmitter (not shown).

The receiver 12 may include, for example, a control panel 13 and a graphing display 14. As shown in Figure 3, the control panel 13 includes a plurality of light indicators 17, 20. The light indicators 17 are configured to illuminate, for example, when an adjustment to the display projector 4 is needed. The light indicators 20 are configured to illuminate, for example, to instruct an operator (not shown) as to how the display projector 4 is to be adjusted. In the illustrated embodiment, the control panel 13 uses the light indicators 17, 20 to alert the operator (not shown) as to whether an adjustment to the display projector 4 is needed and how to make the adjustment, however, it will be appreciated by those skilled in the art that other mechanisms for alerting the operator (not shown) may additionally be used. Moreover, the receiver 33 may be configured to automatically adjust the display projector 4 based on the information received from the light measuring device 3.

As shown in Figure 4, the graphing display 14 includes a screen 19 and a computer interface 21 with software for generating a graph 18. In the illustrated embodiment, the graph 18 displays the light level measurements of the light measuring device 3 taken over a time period Tl, T2, T3, however, it will be appreciated by those skilled in the art that other diagnostics of light level measurements from the light measuring device 3 may be displayed. It should be understood that the computer interface may include storage media for storing the light level measurements and may also include means for transmitting stored light level measurements to a remote device such as a computer. The computer or remote device may process the light level measurements for a prediction of lamp life or light output performance. As shown in Figure 1, the display projector 4 includes a light source 22 and a lens 23. The light source 22 may be, for example, a light bulb. The display projector 4 may be, for example, a direct current projector wherein the intensity of the light source 22 may be altered by changing the voltage applied thereto. The light source 22 is configured to project an image through the divider 7 and onto the projection screen 2. The image may be, for example, pre-show material, a test pattern, main show material, etc. An exemplary test pattern 50 is shown in Figure 7. This test pattern 50 contains content sections 52 which may be on-screen advertising material as shown here but may alternatively be trivia, information, instructional or any other content. The content sections 52 are located in a border 9 which surrounds a light measuring area 10 in which white light is projected. It should be understood that while the border 9 is shown here as surrounding the light measuring area 10, other configurations of the border 9 and light measuring area 10 are within the scope of the invention. For example, the light measuring area 10 could be located in place of any one of the content sections 52. The test pattern 50 may additionally be configured to run different colors, logos, advertisements, or other indicia (not shown) on the border 9 while running the white light on the light measuring area 10.

The operation of the light level measuring system 1 will now be described in greater detail with reference to Figure 5. At step 30, main lighting in the first area 5 is dimmed. The display projector 4 is activated to run a pre-show image on the front surface 15 of the projection screen 2. At step 31, the main lighting in the first area 5 is rurned-off. The display projector 4 runs a test pattern 50 on the front surface 15 of the projection screen 2. The test pattern 50 is configured to run about 100 percent of white light on the light measuring area

10. The test pattern 50 may run for a length of about 5-10 seconds.

At step 32, the lens 11 of the light measuring device 3 focuses on the light measuring area 10 while the test pattern 50 in running. The light measuring device 3 measures the light level of the light measuring area 10 with the photo-optic light measuring electronics (not shown). At step 33, the light measuring device 3 transmits a signal to the receiver 33 indicating the light level of the light measuring area 10. The signal maybe transmitted, for example, via the interface (not shown) or the wireless transmitter (not shown). At step 34, the receiver 33 processes the signal received from the light measuring device 3. During processing, the receiver 33 compensates for any light attenuation attributed to the divider 7 that is used to isolate the display projector 4 from the first area 5. At step 35, the receiver 33 illuminates the light indicators 17 on the control panel 13 to communicate to the operator (not shown) the necessary adjustments that need to be made to the display projector 4. The receiver 33 additionally communicates with the graphing display 14 and provides data thereto for generating the graph 18.

At step 36, the operator (not shown) adjusts the display projector 4 based on the information displayed on the control panel 13 and/or the graphing display 14. For example, the voltage to the display projector 4 may be adjusted to increase or decrease the intensity of the light emitted from the light source 22 or the position of the light source 22 may be altered relative to a reflector to increase or decrease the intensity of the light emitted from the light source 22. Alternatively, the receiver 33 may be configured to automatically adjust the display projector 4 based on the information received from the light measuring device 3. At step 37, the display projector 4 runs a main show image (not shown). Because the display projector 4 has been adjusted based on the data communicated to the receiver 12 by the light measuring device 3, the quality of the main show image is optimized.

Figure 6 shows a light level measuring system 40 according to a second embodiment of the invention. Elements of the light level measuring system 40 according to the second embodiment of the invention that are substantially identical to the elements of the light level measuring system 1 according to the first embodiment of the invention will be identified using the same reference numerals and will not be described further herein.

As shown in Figure 6, the light level measuring system 40 includes a light measuring device 41. The light measuring device 41 is positioned adjacent to the rear surface 16 of the projection screen 2. The light measuring device 41 includes at least one light sensor 42. The light sensor 42 may be, for example, a solid state sensor or a photoconductive CdS cell with high level of temperature stability, such as EG&G VT935G. The light sensor 42 is mounted adjacent to at least one of the perforations 24 in the light measuring area 10 and has a diameter of about 3.6 millimeters. The light sensor 42 may be calibrated against a reference photometer based on the diameter of the perforations 24 to compensate for light attenuation. A protective coating 43 may be applied to a light sensing surface of the light sensor 42. The protective coating 43 may be, for example, plastic.

The light measuring device 41 may be connected to a circuit that converts the output of the light sensor 42 to a voltage or binary value that may be transmitted to the receiver 12. For example, a typical analog device would provide a battery power source and a reference voltage circuit for an A/D converter. An output of the A/D converter would, for example, be stored as a 12 bit value in a memory register that would allow for remotely triggered transmission of the stored data to the receiver 33. One example of such an analog device would be differential A/D converter ADuC834.

The method of operation of the light level measuring system 40 according to the second embodiment of the invention is substantially identical to the method of operation of the light level measuring system 1 according to the first embodiment of the invention and therefore will not be described further herein.

The foregoing illustrates some of the possibilities for practicing the invention. Many other embodiments are possible within the scope and spirit of the invention. It is, therefore, intended that the foregoing description be regarded as illustrative rather than limiting, and that the scope of the invention is given by the appended claims together with their full range of equivalents.

Claims

1. A system for measuring light levels from a display projector, comprising: a projection screen having a front surface with a light measuring area; a display projector having a light source that projects about 100 percent white light on the light measuring area; and a light measuring device that measures the intensity of the white light on the light measuring area, the light source being adjusted depending on the measurement of the intensity of the white light on the light measuring area.

2. The system of claim 1, wherein the projection screen includes a plurality of perforations that extend from a front surface to a rear surface thereof, the light measuring device having a sensor mounted adjacent to at least one of the perforations on the rear surface of the projection screen.

3. The system of claim 1, wherein the light measuring area is about 2 percent of the projection screen. 4. The system of claim 1, wherein the light measuring area is substantially centrally located on the projection screen.

5. The system of claim 1 further comprising at least one content section located adjacent the light measuring area.

6. The system of claim 5 wherein the at least one content section comprises on- screen advertising.

7. The system of claim 1 , wherein the projection screen and the light measuring device are arranged in a first area and the display projector is arranged in a second area, the second area being separated from the first area by a divider.

8. The system of claim 1, further comprising a receiver that processes the measurement of the intensity of the white light on the light measuring area and signals a control panel.

9. The system of claim 1, further comprising a graphing display that displays diagnostics of light level measurements from the light measuring device.

10. The system of claim 9 further comprising a storage media for the light level measurements, the storage media being capable of storing trend data including the light level measurements.

11. The system of claim 10 wherein the light level measurements or trend data are transmitted to a remote device.

12. A method for measuring light levels from a display projector, comprising the steps of: providing a projection screen; projecting about 100 percent white light on a light measuring area on a front surface of the projection screen with a light source in a display projector; measuring the intensity of the white light on the light measuring area with a light measuring device; and adjusting the intensity of the light source depending on the measurement of the intensity of the white light on the light measuring area. 13. The method of claim 12, wherein the projection screen includes a plurality of perforations that extend from the front surface to a rear surface thereof, the light measuring device having a sensor mounted adjacent to at least one of the perforations on the rear surface of the projection screen.

14. The method of claim 12, wherein the light measuring area is about 2 percent of the projection screen.

15. The method of claim 12, wherein the light measuring area is substantially centrally located on the projection screen. 16. The method of claim 12 further comprising locating at least one content section adjacent to the light measuring area.

17. The method of claim 12, further comprising arranging the projection screen and the light measuring device in a first area and the display projector in a second area and separating the first area from the second area with a divider. IS. The method of claim 12, further comprising processing the measurement of the intensity of the white light on the light measuring area and signaling a control panel.

19. The method of claim 12, further comprising displaying diagnostics of light level measurements from the light measuring device of a graphing display.

20. The method of claim 12 further comprising storing light level measurements and transmitting the stored light level measurements to a remote device.