JPH09203690A - Method and apparatus for measuring uniformity of illumination of liquid crystal light valve projector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a system for measuring uniformity of illumination of an LCLV for a liquid crystal light valve(LCLV) projector. SOLUTION: A projector 54 reflects a light emitted from a first LCLV 86A to form an image on a screen 58. An image sensing device 62 detects values of illuminance at a plurality of positions in the image. A processor 66 is connected to the image sensing device 62 and projector 54. The processor 66 determines an optimum bias voltage to obtain the maximum illuminance in terms of a plurality of pixels. This measuring system can independently measure non-uniformity of illuminance of the LCLV and non-uniformity of illuminance due to a roll-off of a projection lens, a gain of the screen and non-uniformity of illuminance of the other. A correction system can improve quality of the indication image by utilizing the non-uniformity of the measured illuminance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projector, and more particularly to measurement of illuminance uniformity of a liquid crystal light valve projector.

[0002]

An image light amplifier or liquid crystal light valve (LCLV) is an imaging device in which the transmission or reflection of light changes in response to an externally applied quantity such as voltage, current and / or light. Conventionally, one or more LCLVs have been adopted in the LCLV projection system. For example, a color LCLV projector uses three LCLVs, one for green light, one for red light, and one for blue light. The three colors of light are mixed by the three LCLVs to create another color and form a display image on the screen.

In a reflection type LCLV color projector, read light is separated by one or a plurality of dichroic mirrors. The reading light is separated into red, green, and blue lights by the dichroic mirror, and these lights go to one side of the first, second, and third LCLVs, respectively.
The first, second and third writing lights are the first, second and third LCs.
Directed to the other side of the LV. The writing light modulates the reflection of light emitted from each of the first, second, and third LCLVs, like a variable mirror. Each LCL illuminated by writing light
The V portion reflects the read light and changes the polarization. The other part of each LCLV that is not illuminated by the writing light is reflected with no change in polarization. The light reflected by the LCLV goes through a dichroic mirror to a polarization analyzer. The polarization analyzer discards the unpolarized light and transmits the polarized light through the projection lens onto the screen.

A typical reflective LCLV is made up of multiple layers of thin films. It is difficult to make multiple layers uniformly and with a uniform thickness. The LCLV optical transfer function, which represents the output light as a function of the input light, is also generally non-uniform, as single layer or multi-layer thin films are generally non-uniform and / or non-uniform in thickness. In other words, each layer is made non-uniform and / or non-uniform in thickness, resulting in an LC on the surface of the LCLV.
The LV light transfer function is not constant. If the LCLV light transfer function is not constant, undesirable non-uniformities such as gray scale errors or color shading errors will appear in the displayed image.

One way to detect the LCLV light transfer function is to inspect the displayed image on the screen that is reflected by one or more LCLVs. Before trying to determine the transfer function of the LCLV light by analyzing the displayed image, the roll-off of the projection lens is attempted.
f), projection angle to the screen, screen gain,
Illuminance non-uniformities due to other sources, such as illumination non-uniformities due to other sources, must be considered. It is preferable to measure and correct the nonuniformity of the transfer function of the LCLV light, excluding the adverse effects caused by the nonuniformity of illuminance due to these other causes.

In other words, the uniformity of the illuminance of the displayed image is a combination of the nonuniformity of the transfer function of the LCLV light and the nonuniformity of the illuminance due to other causes. Without first knowing the contribution of illumination non-uniformity due to other causes,
The non-uniformity of the transfer function of the LCLV light cannot be independently determined.

According to the conventional method of detecting the non-uniformity of the illuminance due to other causes, a mirror is installed in the projector instead of the LCLV as a "perfect LCLV". Performing the manual mounting work requires removing the LCLV projector from service, is time consuming, requires skilled technicians, and may, for example, accidentally mount a "perfect" LCLV. Measurement errors due to this are also likely to occur. Once the illuminance non-uniformity due to other causes is determined, a correction signal can be added to cancel the illuminance non-uniformity due to other causes. Then L
Non-uniformity in illuminance due to the CLV light transfer function can be measured and corrected.

[0008]

Therefore, the LCLV
It is desirable to have a simple and improved method and apparatus for measuring projector illumination uniformity.

[0009]

The method for measuring the illuminance uniformity of a liquid crystal light valve (LCLV) of a projector according to the present invention comprises: a) forming a picture on a screen by reflecting the light emitted from the LCLV. A) detecting an illuminance value of a plurality of portions of the image using an image sensing device; and c) determining an optimum bias voltage that gives maximum illuminance to the plurality of portions of the image. Including and

According to another feature of the invention, the method further comprises repeating steps a) to c) for a plurality of LCLVs, each associated with a different light.

According to yet another feature of the invention, the method further comprises initializing a bias voltage value, an old illumination value and a new illumination value for at least a portion of the image.

According to yet another feature of the invention, the method further comprises increasing the bias voltage value, measuring a new illuminance value for the bias voltage, the new illuminance value and the old illuminance value. And a step of making the new illuminance value equal to the new illuminance value if the new illuminance value is larger than the old illuminance value.

According to another aspect of the invention, a system for measuring the uniformity of illumination of a liquid crystal light valve (LCLV) of an LCLV projector includes a first LCLV, the first LCLV.
The projector includes means for reflecting light emitted from the LCLV to form an image on the screen. The image sensing means detects illuminance values for a plurality of parts of the image.
Processing means is connected to the image sensing means and the projection means to determine an optimum bias voltage that provides maximum illumination for the plurality of portions of the image.

According to another feature of the invention, the system further comprises designation means associated with the processing means for sequentially selecting each of the plurality of portions of the image.

According to another feature of the invention, the projection means comprises a plurality of LCLVs, each associated with a different light.

According to another feature of the invention, the system is further associated with the processing means and comprises the plurality of LCs.
An LCLV designation means for sequentially confirming each LV is included.

According to another feature of the invention, the system further comprises voltage setting means for continuously increasing the bias voltage applied to the first LCLV, the image sensing means corresponding to the bias voltage. Measure the new illuminance value.

According to another feature of the invention, the processing means comprises optimum setting means for recognizing a maximum illuminance value for each part of the image.

According to another feature of the invention, the image sensing means comprises a charge coupled device camera oriented towards said screen.

According to yet another aspect of the invention, an LCLV
A system for measuring the uniformity of illumination of a liquid crystal light valve (LCLV) for a projector includes a projection means including a first LCLV, the projection means projecting light modulated by the first LCLV, Form an image on the screen. The image sensing means detects illuminance values for a plurality of portions of the image. At least one processor is connected to the image sensing means and the projection means and is at least one of the plurality of images.
It has control means for performing a procedure of measuring the uniformity of the illuminance, which determines the maximum illuminance for the individual parts. Other objects, features and advantages will be readily apparent.

[0021]

Various advantages of the present invention will become apparent to those skilled in the art by describing the present invention with reference to the drawings. A typical project is to use an image light amplifier or a liquid crystal light valve (LCL) as an imaging device.
V) is adopted. The LCLV is made up of many thin film layers, and it is difficult to make these thin film layers uniformly and with a uniform thickness. The LCLV optical transfer function, which represents the output light as a function of the input light, is not uniform because some of the thin film layers are non-uniform and / or non-uniform in thickness. In other words, the LCLV light transfer function is not constant on the surface of the LCLV, which causes an undesirable phenomenon that the illuminance of the displayed image is not uniform.

Screen areas 10A-10K shown in FIG.
Have different illuminance values. For example, screen area 1
0A has the maximum illuminance measurement value, and the screen area 10
H has the smallest illuminance measurement value, and the illuminance measurement values of the remaining screen areas 10B-10G, 10I, and 10J are intermediate. It can be appreciated that non-uniform illuminance values affect the image quality of the displayed video.

According to the present invention, the image sensing device is provided toward the screen in order to measure the illuminance value of the image displayed on the screen. Preferably, the image sensing device divides the displayed image into a plurality of detection parts or detection areas. The number of detection parts depends on the resolution of the image sensing device. The size and shape of the sensing portion are preferably uniform. In a particularly preferred embodiment, the image sensing device has an illumination measurement for each pixel.

FIG. 2A shows the LCLV optical transfer function for one uniform sensing portion measured by the image sensing device. As the bias voltage Vbias of the LCLV driver is increased, the illuminance Lout increases and reaches the maximum illuminance Lopt at the optimum voltage Vopt. When the bias voltage Vbias becomes higher than the optimum voltage Vopt, the LCLV
Turns on and the illumination decreases as the bias voltage increases. At voltages near Vopt, the transfer function is relatively flat and wide.

To get closer to a "perfect" LCLV,
The measured illuminance value of each uniform sensing part shall be maximized. However, there is only one bias voltage input for a typical reflective LCLV for all LCLVs. That is, in order to control the illuminance value of each detection part of the image, the LC
The LCLV does not have a matrix input for individually addressing different parts of the LV.

FIG. 2B shows the color LCLV project 3
The transfer function for each region is shown. A color LCLV projector has three LCLVs each corresponding to each of the three primary colors.
It is preferred to have LCLVs. Each of the three LCLVs has its own LCLV light transfer function for each sensing portion or pixel measured by the image sensing device. It can be seen that each sensing portion or pixel measured by the image sensing device has its own Lopt. If uncorrected, differences in the LCLV light transfer functions will manifest themselves as color shading errors or grayscale errors. These vary on the surface of the LCLV or on the projected image. That is, the LCLV light transfer function of the other sensing portion or pixel is L in FIG. 2B.
Not the same as the CLV light transfer function. As a result, the colors of the displayed image will be distorted.

In the method and apparatus for measuring the uniformity of illuminance according to the present invention, the bias voltage Vbias of each LCLV is increased. While increasing the Baice voltage Vbias from zero, check the optimum illuminance Lopt of each detection part or pixel. In a preferred embodiment, the LCLV has only one voltage input. While increasing the bias voltage Vbias, the optimum illuminance Lopt for each detection portion or pixel is simultaneously measured. After checking, the optimum illuminance Lopt is stored in the memory for each detection portion or each pixel of the display image.

FIG. 3 shows an illuminance uniformity measuring device 50.
The measuring device 50 is an LCL that projects an image on the screen 58.
It includes a V projector 54 and an image sensing device 62 for measuring a part or pixel of a displayed image.
The LCLV projector 54 includes a central processing unit 66 having a microprocessor 70, a memory 74 and an input / output (I / O) interface 78. The LCLV projector 54 further includes an LCLV bias voltage driver 82 and one or more LCLVs 86A, 86B, 8
6C and. The LCLV projector 54 further includes a reading light source 88 that emits light to a dichroic separator and polarization analyzer 90. LCLV projector 5
4 is one or more writing light sources 92A, 92B, 9
2C and lens 96 are included. Such a projection system is described in US application S. N. 08 / 318,532, "Color projection system with one projection lens (" Single Projection
Lens Color Projection System ")". This application is assigned to the applicant together with the present application and is incorporated by reference.

In use, the reading light source providing the first polarization emits light towards the dichroic separator and polarization analyzer 90, and the dichroic separator and polarization analyzer 90.
Separates the reading light into first, second and third color lights.
The first, second and third color lights are LCLV86A, 86
B, directed to one side of 86C. Writing light source 92
A, 92B and 92C are LCLV86A and 86, respectively.
Irradiate the opposite side of B and 86C.

Each LCLV acts as a variable mirror. When the writing light source 92 is "bright", the LCLV reflects the reading light and changes the first polarized light into the second polarized light. Writing light source 9
When 2 is "dark", the reading light is reflected from the first polarized light without changing its polarization state. The dichroic separator and polarization analyzer 90 discards the first polarization and transmits the second polarization to lens 96 to create the image.

The LLV bias driver 82 is used for each LCL.
Connected to V. It will be appreciated that the bias voltage Vbias applied to the LCLV controls the reflection of the read light impinging on the surface of the LCLV. If the bias voltage Vbia
Without s, the polarization of the light reflected by the LCLV remains unchanged. When the bias voltage Vbias is applied, the read light reflected by the LCLV increases and the change in polarization increases. In fact, when the bias voltage Vbias is increased to the optimum value, LC
The LV illuminance is increased.

FIG. 4 shows an illumination homogenization procedure 100 performed by the illumination uniformity measuring apparatus 50 shown in FIG. 3 and its associated data structure 110. Data structure 110
Includes an LCLV pointer 112 (designating the current LCLV), a pixel pointer 114 (designating the current pixel of the current LCLV), and an old illuminance (Lold) variable 120.
A new illuminance (Lnew) variable 122 (as the illuminance value corresponding to the new bias voltage for each pixel) is included (as the illuminance value corresponding to the previous bias voltage for each pixel).

Illuminance equalization procedure 100 begins at step 130. The LCLV pointer 112 is preferably used here to designate the first LCLV. For example, the projector 54 is preferably a color projector having three LCLVs. 3 LCLVs in step 130
One of them is selected. In step 132, the variables Lnew and Lold are set to zero and the bias voltage is also set to zero for each sensor portion or pixel. Step 134
Then, the control determines whether or not Vbias has reached the maximum. In step 134, it is checked whether or not the illuminance uniformization processing has been completed for the designated LCLV. If Vbias is less than the maximum value, control proceeds to step 140.

At step 140, the bias voltage Vbias applied to the LCLV is increased. In step 144, the image sensing device 62 measures the new illuminance Lnew for each part or pixel detected by the image sensing device.
In step 146, using the pixel pointer 114,
The first part or pixel to be detected by the image sensing device is designated. In step 148, control is the old illuminance
New illuminance of Lold detected by image sensing device
Compare with Lnew. If Lnew is greater than Lold, control proceeds to step 150. Lold is Lnew in step 150
Is set equal to If in step 148 Lnew is Lold
If not, control proceeds to step 156.
Proceed to. At step 156, control determines whether all portions or pixels of the current LCLV have been compared at the current Vbias. If not, control specifies the next portion or pixel in step 160 and returns to step 148 to create a loop. If all portions or pixels have been compared with the current bias voltage, control returns to step 134.

When it is determined in step 134 that Vbias has reached the maximum value, control proceeds to step 166. In step 166, control determines whether another LCLV measurement is required. If yes, control is step 170.
Specify a new LCLV with and return to step 132
Make a loop. If not, control ends.

As can be seen from FIG. 4, the bias voltage Vbias applied to the LCLV is gradually increased from zero. While increasing the bias voltage applied to the LCLV, the control simultaneously determines the optimum illuminance Lopt for each part or pixel. After a portion or pixel reaches the maximum value corresponding to the optimum illuminance, the comparison to the increased Vbias is denied at step 148 and the control stores the optimum illuminance. Control continues until Vbias reaches the maximum value. If yes,
All sensor parts or pixels have stored the optimum illuminance value. Control then continues for the next LCLV, until all LCLV measurements are complete.

It will be appreciated that there are several other sources of non-uniform illuminance that may be affected by the positional relationship of the screen 58 with respect to the projector 54 and the image sensing device 62. Illuminance uniformity measuring device 5 in FIG.
A typical physical relationship of 0 is shown. Projector 5
4 and the image sensing device 62 are both on the screen 5
It is located above the center line perpendicular to 8. The illuminance distribution of a typical light source 84 of the projector 54 is not perfectly flat. Normally, the illuminance is strongest at the center of the light source and roll-off at the edges. Projection lenses generally exhibit roll-off with respect to uniformity as shown in FIG.

Another source of non-uniform illumination is screen gain, which can be 1 to 3 or more. The screen gain is not always monotonic and may be as shown in FIG. If the projector 54 and the image sensing device 62 have a screen 58 as shown in FIG.
Leaning about, "hot-spot
"Is out of the center of the screen. For example, in the arrangement shown in FIG. 5, the "hot spot" is offset from the center of the screen upwards as shown in FIG. Both the projector 54 and the image sensing device 62 are located near the top of the screen 58. Moreover, in FIG. 5, the displayed image may require keystone correction so that the displayed image looks square on the screen 58.

Placing the projector 54 and the image sensing device 62 in different positions will cause other errors due to non-uniformity of illumination due to other causes. As shown in FIG. 9, when the projector is arranged above the center of the screen 58 and the image sensing device 62 is arranged below the center of the screen 58, the screen 5
The illuminance of 8 would be as shown in FIG.

It will be appreciated that the illumination uniformity of the projector 54 will vary depending on the application. By measuring the displayed image on the screen using the illuminance uniformity measuring device 50, the stored perfect illuminance value for each sensor pixel determined using the illuminance measurement procedure is used to obtain a "perfect" LCLV. You can get closer. Since the optimum illuminance value is used, all the differences in illuminance are the roll-off of the projection lens,
It is a result of non-uniformity of illumination due to other factors such as projection angle to the screen, screen gain, etc. (LCL
This is not due to the uneven illuminance of V).

The use of the LCLV projector in normal mode reduces or eliminates illumination non-uniformity due to these other causes. Thus, the non-uniformity due to the LCLV light transfer function can be determined. For example, let's project a blue light with a medium illuminance value. The image sensing device 62 can measure the relevant illuminance value and make an appropriate correction to the LCLV light transfer function based on it. Then another LCLV can be measured. The light transfer function for the resulting data is purely a function of the LCLV inhomogeneity. Thus, rather than correcting for non-uniformity of illuminance due to other causes,
Only the non-uniformity of the LCLV can be corrected.

Once the error data relating to the non-uniformity of the illuminance due to other causes is obtained and corrected, the non-uniformity data is smoothed and used in the servo system.
It is possible to correct the non-uniformity of the LCLV illuminance. The error data may be processed with pixels and subjected to a two-dimensional filtering process for smoothing the data. In a three-color LCLV projector system, each channel would have its own illumination non-uniformity measurement data. Preferably, the data obtained from the three LCLVs should be normalized and averaged into one common function to prevent color shading errors from being artificially introduced.

It will be appreciated that the apparatus for measuring illumination uniformity according to the present invention eliminates the problems associated with using mirrors. With the uniformity of illuminance measurement device, it is not necessary to remove the projector from service in order to mount the mirror. By following the illuminance uniformity measurement procedure, measurement errors that occur when conventional mirrors are not properly mounted are less likely to occur. The illumination uniformity measurement procedure can also be performed quickly.

As can be understood from the above description, according to the present invention, the user can determine the nonuniformity of the illuminance of the LCLV of the LCLV projector.
Although the present invention has been described in connection with specific embodiments, it is not intended to be limited except as set forth in the following claims. that is,
It will be appreciated by those skilled in the art, after studying the specification, drawings and claims, that other modifications can be made without departing from the spirit of the invention.

[Brief description of drawings]

FIG. 1 is a diagram showing nonuniformity of illuminance of a projector.

FIG. 2 is a graph showing a light transfer function of a liquid crystal light valve (LCLV), where A is a light transfer function of a part of the LCLV and B is a light transfer function of three parts of the LCLV color projector. .

FIG. 3 is a schematic diagram of an electrical system of an apparatus for measuring illuminance uniformity according to the present invention.

FIG. 4 is a diagram showing a flowchart showing an illuminance uniformization procedure executed by the illuminance uniformity measuring device of FIG. 3 and a diagram showing a data structure associated therewith.

5 is a diagram showing one possibility of a physical positional relationship with respect to a screen of the illuminance uniformity measuring device of FIG.

FIG. 6 is a graph showing an illuminance distribution of a light source used for an LCLV projector.

FIG. 7 is a diagram showing that the gain of the screen is not monotonic.

FIG. 8 is a diagram showing a change in illuminance due to the positions of the LCLV projector and the image sensing device deviating from the center in the physical arrangement shown in FIG.

FIG. 9 is a diagram showing another possibility regarding the physical arrangement of the image uniformity measuring device, in which the LCLV projector and the image sensing device are arranged on both sides of a center line perpendicular to the screen.

10 is a graph showing an illuminance distribution in the physical arrangement shown in FIG.

[Explanation of symbols]

 50 Illuminance uniformity measuring device 54 Projector 58 Screen 62 Image sensing device 66 Processor 86 LCLV

Claims (19)

[Claims] 1. A) a step of reflecting light emitted from a liquid crystal light valve (LCLV) to form an image on a screen, and (b) an illuminance value of a plurality of portions of the image using an image sensing device. And (c) determining the optimum bias voltage that gives the maximum illuminance to the plurality of parts of the image, and measuring the uniformity of the illuminance of the liquid crystal light valve of the projector. 2. The method of claim 1, further comprising the step of: d) repeating steps a) to c) for a plurality of LCLVs, each of which is associated with light of a different color. Measuring method. 3. The method according to claim 1, wherein step c) further comprises c) 1) a bias voltage value, an old illuminance value and a new illuminance value related to at least one of the plurality of portions of the image. A method for measuring the uniformity of illuminance, further comprising the step of: 4. The method according to claim 3, wherein step c) further comprises c) 2) increasing the bias voltage, c) 3) measuring a new illuminance value with respect to the bias voltage, and c) 4) Comparing the new illuminance value with the old illuminance value; c) 5) if the new illuminance value is greater than the old illuminance value, setting the old illuminance value equal to the new illuminance value. Further included is a method of measuring the uniformity of illuminance. 5. The method of claim 4, wherein step c) further comprises c) 6) repeating steps 3) to 5) for each of the remaining portions of the image. , Measuring the uniformity of illuminance. 6. A projection means including a first liquid crystal light valve (LCLV) for reflecting light emitted from the first LCLV to form an image on a screen, and a plurality of portions of the image. An LCLV projector including: an image sensing unit that detects an illuminance value; and a processing unit that is connected to the image sensing unit and the projection unit and that determines an optimum bias voltage that gives a maximum illuminance for the plurality of portions of the image. System for measuring the illuminance uniformity of liquid crystal light valves for LCD. 7. The illuminance uniformity measurement system according to claim 6, further comprising: designation means associated with the processing means, the designation means for selecting each of the plurality of portions of the image in conformity. . 8. The apparatus according to claim 6, wherein the projector comprises a plurality of LCs each associated with a different color of light.
Illuminance uniformity measurement system including LV. 9. The illuminance uniformity measurement system according to claim 8, further comprising: an LCLV designating unit that is associated with the processing unit and sequentially confirms each of the plurality of LCLVs. 10. The apparatus according to claim 6, further comprising a voltage setting means for continuously increasing a bias voltage applied to the first LCLV, wherein the image sensing means has a new illuminance value corresponding to the bias voltage. Measuring system of illuminance uniformity. 11. The illuminance uniformity measurement system according to claim 10, wherein said processing means includes optimum setting means for recognizing a maximum illuminance value for each part of said image. 12. The system of claim 6, wherein the image sensing means comprises a charge coupled device camera oriented toward the screen. 13. A first liquid crystal light valve (LCLV) comprising: projecting light modulated by the first LCLV,
A projection means for forming an image on a screen; an image sensing means for detecting illuminance values with respect to a plurality of portions of the image; and a plurality of the plurality of the images connected to the image sensing means and the projection means. Illuminance uniformity of a liquid crystal light valve for an LCLV projector, comprising: at least one processor having a control means for performing an illumination uniformity measuring procedure to determine a maximum illumination for at least one portion. Measuring system. 14. The apparatus according to claim 13, further comprising: designation means associated with the control means and the at least one processor for sequentially selecting each of the plurality of portions of the video. Including, illumination uniformity measurement system. 15. The system of claim 13, wherein the projector comprises a plurality of LCLVs, each associated with a different color of light. 16. The illumination according to claim 15, further comprising: an LCLV designating means associated with the control means and the at least one processor, for sequentially selecting each of the plurality of LCLVs. Uniformity measurement system. 17. The apparatus according to claim 13, further comprising voltage setting means associated with said control means and said processor, for continuously increasing a bias voltage, said image sensing means corresponding to said bias voltage. Illuminance uniformity measurement system that measures the measured illuminance value. 18. The apparatus according to claim 17, wherein the control means and the processor a) measure an illuminance value corresponding to the bias voltage, and b) compare a new illuminance value with an old illuminance value. C) If the new illuminance value is greater than the old illuminance value,
A illuminance uniformity measurement system that replaces the old illuminance value with a new illuminance value. 19. The illuminance uniformity measurement system according to claim 18, wherein the control means and the processor repeat steps a) to c) for each of the plurality of portions.