JPH1098738A - Uneven color correction circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable the uneven color correcting circuit which is used for a projection display to appropriately correct uneven colors corresponding to the changes of a raster area only with common correction data of one plane (one group) even if the raster area on the screen of a CRT changes. SOLUTION: Correction data by the colors R, G, and B are set by small block areas obtained by dividing a video area and stored in a nonvolatile memory 3, correction data read out of the nonvolatile memory 3 at a reset time are so interpolated as to have lines as many as scanning lines in the longitudinal direction of the video and expanded in a VRAM 5, and after data of the VRAM 5 are outputted in order in the normal mode after resetting by using a horizontal and a vertical synchronizing signal as a trigger, the data are passed through analog filters 6 to 11 as in the lateral direction of the video to generate correction signals for the three colors R, G, and B, so that a composite signal obtained by operating the source signal for the primary colors R, G, and B by using the correction signals is inputted to CRT drive circuits 18 to 20.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection-type display, in which color unevenness on a screen caused by unevenness in alignment of liquid crystal molecules inherently provided in a liquid crystal panel as a display device is reduced, and a uniform image is obtained. The present invention relates to a color non-uniformity correction circuit for ensuring color unevenness.

[0002]

2. Description of the Related Art In recent years, projection-type displays (projectors) have become widespread as large displays for home theater or business use. On the other hand, switching of various videos, such as general television broadcasts, high-vision broadcasts, and computer output images, using the same video display device has been increasing. Therefore, even a projection type display needs to have a function of switching an aspect ratio, which is an aspect ratio of a screen, and a function of changing and adjusting the shape, position, and size of a raster on a screen.

In a liquid crystal light valve as one of such projection displays, a liquid crystal panel as a display device is illuminated with an image from a CRT, and an illuminated area is irradiated with strong light from a lamp light source, so that a light is emitted from the display device. A large screen image is obtained by projecting the reflected light onto a screen. In the case of a liquid crystal light valve, three liquid crystal panels of RGB are used as a display device, but the alignment unevenness of liquid crystal molecules inherent in these liquid crystal panels has a great influence as a cause of color unevenness in a screen image after RGB three-color synthesis. I do. In order to reduce the color unevenness, color unevenness correction is performed for each of the RGB colors by applying an electrical correction voltage that cancels the color unevenness voltage.

A conventional color unevenness correction circuit is disclosed in
The one described in JP-A-125585 is known.
This color unevenness correction circuit has a configuration as shown in FIG.
An image on the screen is captured in advance by a video camera, the entire image is divided into a plurality of small blocks, correction data is set for each of the small blocks for each color of RGB, and stored in a nonvolatile memory. Finer correction is possible as the number of small blocks into which the video is divided, that is, the finer the division, but if the division is too fine, it takes time to set and store the correction data. Further, the required capacity of the nonvolatile memory 45 increases, which leads to an increase in cost.

Immediately after the reset, the microcomputer 46 reads out the correction data stored in the nonvolatile memory 45. In the normal mode, the horizontal and vertical synchronizing signals output from the synchronizing circuit are used as triggers to sequentially convert the correction data into analog correction signals by the DA converters 47 to 49 and supply the analog correction signals to the gain controllers 50 to 52. Each of the RGB video signals is multiplied by an analog correction signal by the gain controllers 50 to 52, and then amplified by the amplifiers 53 to 55 and input to the CRT 56.

As described above, usually, the projector is C
It has a function to change the raster area on the RT screen. When the raster area changes, the microcomputer 46 needs to develop correction data corresponding to the changed raster area in the internal RAM. Therefore, a plurality of sets of color non-uniformity correction data corresponding to a plurality of raster patterns are set, and a plurality of areas for storing these correction data are secured in the nonvolatile memory 45 (see FIG. 5). The microcomputer 46 determines the currently used raster pattern and reads the color unevenness correction data corresponding to the raster pattern.

[0007]

However, in the conventional configuration as described above, when the raster area changes on the screen of the CRT, it is necessary to set the same number of correction data as the number of types of raster patterns. It takes a lot of effort and time. Further, since the correction data for a plurality of planes is stored in the non-recursive memory, the required memory capacity is increased, the efficiency is reduced, and the cost increases.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a color shading correction circuit capable of appropriately performing color shading correction even when a raster area changes, using correction data for only one surface (one set). .

[0009]

SUMMARY OF THE INVENTION A color shading correction circuit according to the present invention comprises a plurality (A) of image areas divided vertically and horizontally.
× B) correction data for each of the RGB colors is set for each of the small block areas and stored in the nonvolatile memory, and the correction data read from the nonvolatile memory at the time of reset is the same as the number of scanning lines in the vertical direction of the image. After performing an interpolation calculation so as to obtain a number, the data is developed in a VRAM, and in a normal mode after reset, data output from the VRAM sequentially through a horizontal and vertical synchronization signal as a trigger is passed through an analog filter in the horizontal direction of the image. A correction signal for three colors of RGB is generated, and for each of the three colors of RGB,
A composite signal obtained by performing an arithmetic operation on the original signal with the correction signal is input to a CRT drive circuit.

[0010] Preferably, the correction data comprises luminance correction data and contrast correction data.
For each of the colors, a luminance correction signal generated from the luminance correction data is added to the original signal, a contrast correction signal generated from the contrast correction data is multiplied, and a resultant signal is input to a CRT drive circuit. .

The above-mentioned interpolation operation can be realized by, for example, software of a microcomputer.
In this case, the microcomputer is configured to perform an m-th order (m is an integer of 2 or more) spline interpolation operation that is linear interpolation or curve interpolation, thereby minimizing the amount of data stored in the nonvolatile memory. Is preferred.

Further, a CR constituting a projection type display is provided.
When at least one of the shape, size, and position of the raster area changes on the screen of T, the corrected data after the change is preferably obtained as follows. As a first method, the coordinates of the movement destination of each correction point in the raster area are automatically coordinated based on the value obtained by AD converting a plurality of adjustment voltages for controlling the horizontal and vertical deflection circuits for determining the correction data and the raster area. The correction data estimated by the conversion and corresponding to the correction point on the grid closest to the coordinates of the movement destination is read from the nonvolatile memory.

As a second method, the coordinates of the movement destination of each correction point in the raster area are determined based on the values obtained by AD-converting the correction data and a plurality of adjustment voltages for controlling the horizontal and vertical deflection circuits for determining the raster area. Is estimated by automatic coordinate conversion, the correction data corresponding to a plurality of correction points on the grid around the coordinates of the movement destination are read from the nonvolatile memory, and these correction data are read out from the coordinates of the movement destination and each correction point. Thus, the value obtained by performing the weighted averaging process according to the distance is used as the correction data of the coordinates of the movement destination.
Even when the raster area changes, the corrected data can be obtained only by the common correction data for one surface, so that the time and effort of imaging by the camera for setting the correction data are minimized. The required capacity of the nonvolatile memory for storing the correction data can be reduced.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a schematic configuration of a color shading correction circuit according to a first embodiment of the present invention. In the color shading correction circuit, an input video signal is separated by a sync separation circuit 1 into a chroma signal and horizontal / vertical sync signals. The chroma signal is input to the RGB separation circuit 2,
The GB separation circuit outputs RGB three-system original signals. When these original signals are input to the respective CRT drive circuits as they are and irradiated to the liquid crystal panel from each CRT, the RGB signals are generated due to the uneven alignment of the liquid crystal molecules inherent in the three liquid crystal panels.
The combined light causes two-dimensional color unevenness on the screen.

Therefore, before inputting each original signal to each CRT drive circuit, an appropriate image is obtained on the screen by adding an electric correction signal for correcting color unevenness to the original signal. The user corrects the brightness and contrast for each of the divided small blocks by using the remote controller or the control button while watching the image on the screen, so that an appropriate image is obtained. Instead of the user manually compensating,
The image on the screen is converted into an electric signal by the camera,
The correction data may be automatically obtained based on the obtained image data.

During the adjustment of the color unevenness correction, it is necessary to make the raster area on the CRT screen the maximum area. The brightness and contrast correction data obtained by the adjustment are the correction data at the representative points for each small block obtained by dividing the entire image into A × B (A is the number of vertical divisions, B is the number of horizontal divisions). It is. These correction data are stored in the nonvolatile memory 3 for each of RGB.

When the microcomputer 4 is reset, the data stored in the nonvolatile memory 3 is read into the internal RAM of the microcomputer 4 in the initial processing. The microcomputer 4 includes the nonvolatile memory 3
The vertical interpolation of the video is performed on the correction data read from the CPU to generate correction data of a number corresponding to the number of scanning lines. The result is expanded in VRAM5. As the interpolation calculation, spline interpolation, which is a kind of curve interpolation capable of performing smoother interpolation, can be adopted in addition to linear interpolation, which is simple and can be processed in a short time.

In the normal mode, horizontal / vertical synchronization signals output from the synchronization separation circuit 1 are input to the VRAM 5, and correction data is sequentially output using these synchronization signals as triggers. The output of the VRAM 5 has not been subjected to the horizontal interpolation processing of the video, and is a digital waveform. Therefore, the luminance correction signal passes through the analog filters 6 to 8, and the contrast correction signal passes through the analog filters 9 to 11, thereby generating an analog correction signal.

Thereafter, a multiplier 1 is added to the RGB original signal.
The contrast correction signals are multiplied by 2 to 14, and the luminance correction signals are further added by adders 15 to 17. RGB obtained through these multiplication and addition processes
Are input to the CRT drive circuits 18 to 20, respectively, so that the uneven color distribution generated on the CRTs 21 to 23 is corrected.

Normally, a projection type display has a function of changing a raster area on a screen of a CRT. When the raster area changes, the microcomputer 4 executes automatic coordinate conversion for developing correction data corresponding to the position of the raster area in the VRAM 5. FIG. 2 shows the concept of the automatic coordinate conversion algorithm.

In FIG. 2, reference numeral 24 denotes coordinates before conversion;
Reference numerals 34 to 34 denote respective adjustment units, 35 denotes an addition unit, and 36 denotes coordinates after conversion. Each of the adjustment units 25 to 34 includes a position (position) adjustment unit 25, a linearity (linear) adjustment unit 26, and a size adjustment unit 2.
7, diagonal inclination (skew) adjustment unit 28, bow (baud) adjustment unit 29, centering adjustment unit 30, keystone distortion adjustment unit 31, keystone distortion balance (keystone balance) adjustment unit 32, pincushion distortion (pin cushion) ) Adjustment unit 3
3. A pincushion balance adjusting section 34 for pincushion distortion.

Each adjustment parameter of each of the adjustment units 25 to 34 is converted into a signal having a sawtooth waveform or a parabolic waveform, and controls the CRT drive circuits 18 to 20. The sawtooth waveform and the parabolic waveform are approximated by L-order expression and M-order expression (L and M are integers of 1 or more), and the movement amounts in the horizontal and vertical directions are represented by Δx _i , Δ
y _i , the horizontal and vertical coordinates before movement are x, y, and the movement coefficient (1
When the movement amounts per adjustment step) are α _i , β _i , the user adjustment values are m _i , n _i , and the adjustment default values are m _0i , n _0i , the movement amounts Δx _i , Δy _i by the respective adjustment parameters are shown in FIG. It is approximated as shown in FIG. However, the A / D conversion value of the CRT drive control voltage is fed back to the microcomputer 4 and user adjustment values m _{1 to} m ₁₀ and adjustment standard values m _{01 to} m ₀₁₀ are input.

FIG. 2 shows an example in which L = 1 and M = 2 are approximated by mathematical formulas. To pursue high-precision correction, it is necessary to increase the orders L and M. The parameters 25 to 34 are representative examples, and even when there are other adjustment parameters, the parameters may be similarly approximated and added.

In the present algorithm, each adjustment parameter is
The amount of coordinate movement Δx by the data 25 to 34 ₁~ △ x_TenAnd △
y₁~ △ y_TenAre calculated independently, and these calculation results are added.
Horizontal / vertical movement amount {x /}
Find y. As a result, the coordinates after the movement are P ′ = (x ′,
y ′) = (x + △ x, y + △ y). This operation al
Apply the algorithm to all adjustment points. Control of deflection circuit
In other cases where the mechanism differs from that of FIG.
Then, an automatic coordinate conversion algorithm can be created.

FIG. 3 shows the positional relationship before and after the automatic coordinate conversion. In FIG. 3, reference numeral 37 denotes an adjustment point before movement.
The coordinates are P = (x, y). 38 is a correction point after the movement, and its coordinates are P ′ = (x ′, y ′) =
(X + △ x, y + △ y). In order to create correction data that matches the raster area after the movement, it is necessary to use not the correction data of the P point but the correction data of the P ′ point. The microcomputer 4 substitutes the correction data of the correction point P ₁ = (x ₁ , y ₁ ) on the grid closest to the point P ′ in order to make the process of obtaining the correction data of the point P ′ short and simple. This processing is performed for all correction points, and after performing vertical interpolation processing of the video, the VRA
Develop data to M5.

Next, a color shading correction circuit according to a second embodiment of the present invention will be described. In the color nonuniformity correction circuit, in order to increase the accuracy of the color nonuniformity correction, correction data matching the raster area after the movement is more accurately obtained by the internal differentiation processing than in the first embodiment.

The concept of the internal differentiation processing here will be described based on the positional relationship before and after the automatic coordinate transformation shown in FIG. FIG.
In 39, 39 indicates an adjustment point before coordinate conversion, and its coordinates are P = (x, y). Numeral 40 denotes a correction point after coordinate conversion, and its coordinates are P '= (x', y '). Reference numerals 41 to 44 denote four correction points on the grid around the point P ′, and their coordinates are P ₁ = (x ₁ , y
₁ ), P ₂ = (x ₂ , y ₂ ), P ₃ = (x ₃ , y ₃ ), P ₄ =
(X ₄ , y ₄ ). D ₁ , D ₂ , D ₃ , and D ₄ are adjustment data of the respective correction points 41 to 44.

In the first embodiment (FIG. 3), when the correction data at the point P 'is obtained before the interpolation processing in the vertical direction of the image is performed, P ₁ which is closest to the point P' in order to simplify the calculation.
The point correction data is substituted. In this case, the point P 'and P
An error occurs according to the distance from _one point, and correction data that exactly matches the two-dimensional uneven color distribution cannot be created.
Therefore, in order to create more accurate correction data, in the present embodiment, the correction data of the coordinate P ′ of the movement destination is used by using the correction data of the adjustment points P _{1 to} P ₄ on the four grids around the coordinate P ′. Calculated by internal differentiation processing (weighted average).

That is, the coordinates P '(x', y ') of the movement destination
Taking each adjustment point _{P i (x i, Y i} ) point each adjusting weighted in inverse proportion to the distance L _i between _{P i (x i, Y i} ) the average of these after applying the correction data D _i in Is the correction data D at the destination coordinate P ′ obtained by the internal differentiation operation. Here, i = 1 to 4.
Therefore, this processing can be expressed by the following two equations (Equation 1 and Equation 2).

[0030]

[Number 1] ^{_{L i 2 = (x'-x}} i) 2 + (y'-y i) 2

[0031]

D = (D ₁ L ₄ + D ₂ L ₃ + D ₃ L ₂ + D ₄ L ₁ ) /
(L ₁ + L ₂ + L ₃ + L ₄ ) In this way, correction data after coordinate conversion can be created more accurately by the internal differentiation process. as a result,
The two-dimensional uneven color distribution is further reduced.

[0032]

As described above, the color non-uniformity correction circuit of the present invention can appropriately perform color non-uniformity correction even when a raster area is changed by one plane (one set) of common correction data. Therefore, the time required for setting the correction data by the camera or the time for adjusting the color non-uniformity performed by the user using the remote controller can be shortened, and the required capacity of the nonvolatile memory can be minimized.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a color shading correction circuit according to a first embodiment of the present invention.

FIG. 2 is a conceptual diagram of an automatic coordinate conversion algorithm in the color shading correction circuit of FIG. 1;

FIG. 3 is a positional relationship diagram before and after automatic coordinate conversion in the color unevenness correction circuit of FIG. 1;

FIG. 4 is a diagram showing a color unevenness correction circuit according to a second embodiment of the present invention before and after automatic coordinate conversion.

FIG. 5 is a schematic configuration diagram of a conventional color shading correction circuit.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Synchronization separation circuit 2 RGB separation circuit 3 Non-volatile memory 4 Microcomputer 5 VRAM 6,7,8 Analog filter for contrast 9,10,11 Analog filter for luminance 12,13,14 Multiplier 15,16,17 Adder 18 , 19,20 CRT drive circuit 21,22,23 CRT 24 Coordinate P 25 before conversion Position (position) adjustment 26 Linearity (linear) adjustment 27 Size adjustment 28 Skew (skew) adjustment 29 Bow (baud) adjustment 30 Center Ring Adjustment 31 Keystone Distortion Adjustment 32 Keystone Distortion Balance (Keystone Balance) Adjustment 33 Pincushion Distortion (Pin Cushion) Adjustment 34 Pincushion Distortion Balance (Pin Cushion Balance)
Adjustment 35 Addition unit 36 Coordinates P '37,39 after conversion P 38,40 Coordinates before conversion P' 41,42,43,44 Coordinates after conversion Coordinates of adjustment points

Claims (5)

[Claims] 1. A color shading correction circuit for reducing color shading that occurs in an image projected on a screen of a projection display, wherein the image area is divided into a plurality of small block areas divided vertically and horizontally. The correction data for each color was set and stored in the non-volatile memory, and at the time of reset, the correction data read from the non-volatile memory was subjected to an interpolation operation so that the number of scanning lines in the vertical direction of the image was the same as the number of scanning lines. Then, in the normal mode after the reset, the data output from the VRAM are sequentially passed through an analog filter in the horizontal direction of the image in a normal mode after reset, and a correction signal for three colors of RGB is generated. For each of the above, a composite signal obtained by performing an operation using the correction signal on the original signal is used as a CRT drive circuit. A color shading correction circuit configured to be input to a road. 2. The correction data includes luminance correction data and contrast correction data, and for each of three colors RGB, a luminance correction signal generated from the luminance correction data is added to the original signal and generated from the contrast correction data. 2. The color non-uniformity correction circuit according to claim 1, wherein the circuit is configured to multiply the obtained contrast correction signal and to input the obtained composite signal to a CRT drive circuit. 3. The means for performing an interpolation operation on the correction data in the vertical direction of an image is configured to perform an m-th order spline interpolation operation, which is a linear interpolation or a curve interpolation. 3. The color shading correction circuit according to claim 1, wherein is minimized. 4. When at least one of the shape, size and position of a raster area changes on a screen of a CRT constituting a projection type display, a plurality of adjustment voltages for controlling horizontal and vertical deflection circuits for determining the raster area are applied to AD. Based on the converted values, the coordinates of the destination of each correction point in the raster area are estimated by automatic coordinate conversion, and correction data corresponding to the correction point on the grid closest to the coordinates of the destination is stored in the nonvolatile memory. The color non-uniformity correction circuit according to claim 1, wherein the color non-uniformity correction circuit reads out. 5. When at least one of the shape, size, and position of a raster area changes on a screen of a CRT constituting a projection type display, a plurality of adjustment voltages for controlling horizontal and vertical deflection circuits for determining the raster area are adjusted. Based on the converted values, the coordinates of the destination of each correction point in the raster area are estimated by automatic coordinate conversion, and correction data corresponding to a plurality of correction points on a grid around the coordinates of the destination is stored in the nonvolatile memory. 4. The correction data of the coordinates of the movement destination, wherein a value obtained by reading out the correction data from the memory and performing a weighted averaging process according to the distance between the coordinates of the movement destination and each correction point is used. The color unevenness correction circuit described.