JPH0698346A - White balance automatic adjustment circuit - Google Patents

Abstract

PURPOSE:To adjust the white balance automatically by using a correction function to convert a drive voltage of each of R, G, B cathode ray tubes in a projection type color television receiver. CONSTITUTION:A drive voltage of each of cathode ray tubes 1R, 1G, 1B varies with optional several tens of stages of levels from a low light to highlight, and a brightness of a window pattern of the R, G, B projected on a screen 3 is measured by an optical measurement device 10. Then data of a drive voltage versus brightness characteristic are stored in a RAM 18. A luminous characteristic arithmetic operation circuit 20 uses the data to calculate a correlation function correction each brightness characteristic of the R, G, B and a drive ratio. A video signal processing circuit 17 generates a correction drive signal by using the correlation function data to control the drive voltage from a low light to a highlight so as to obtain a uniform white color.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic white balance adjusting device in a color television display device.

[0002]

2. Description of the Related Art A color television display device for providing a color image by adding and mixing three primary colors of red, green and blue is classified into various types according to a display device used. Typical display devices include cathode ray tubes, liquid crystals, plasma displays and the like. The most representative of these is the cathode ray tube, which is a direct-view type in which the self-luminous image of the display device is directly viewed, and the light-emitting image of the display device is enlarged and projected on another display screen through a refraction lens. There are two types of projection type to see.

Now, the white balance adjusting device compensates for the difference in the emission characteristics (relationship between the drive voltage or drive current and the emission brightness) of each monochromatic color of the display device so that the dark part (low light) on the image is changed. This is a device that realizes uniform white in all gradation regions up to the bright part (highlight). Here, a white balance adjusting device in a projection type cathode ray tube having an extremely large driving current range and a non-linear characteristic with complicated emission characteristics will be described.

There are two types of display devices (display devices) using a projection type cathode ray tube: a front projection type for viewing reflected light on the display screen and a rear projection type for viewing transmitted light on the display screen. FIG. 5 is a block diagram showing an example of a white balance adjusting device in a conventional front projection display device. The front projection type display device is configured to include an image emission unit including projection type cathode ray tubes 1R, 1G and 1B which are light sources, magnifying projection lenses 2R, 2G and 2B, and a screen 3.

In this display device, light from the red, green, and blue projection type cathode ray tubes 1R, 1G, and 1B is magnified by the magnifying projection lens 2.
The images are enlarged and projected by R, 2G, and 2B, respectively, and formed on the screen 3, so that the viewer can see the enlarged large-screen image.

The white balance adjustment of the image required at that time is ideally determined in advance for each R, G, B monochromatic light in each gradation from low light to midtone to highlight. It must be controlled to give the desired white color. For white balance adjustment in an actual projection display device, an adjuster manually adjusts various variable resistors while visually observing an image pattern on a screen.

First, for low light, adjustment of the screen voltage (G2 electrode voltage) of each monochromatic projection cathode ray tube,
Alternatively, white is synthesized by adjusting the mutual balance of the screen cutoff voltages of the monochromatic projection cathode ray tube. Next, for the region from the halftone to the highlight, balance the drive voltages of the monochromatic projection cathode ray tubes with each other,
Combine so that it becomes white.

FIG. 6 is a characteristic diagram showing the relationship between drive voltage and brightness of each monochromatic projection cathode ray tube. As shown in the figure, the emission characteristics of the red, green, and blue projection cathode ray tubes 1R, 1G, and 1B are represented by solid lines L _R , L _G , and L _B , and are different from each other. Especially for the blue projection cathode-ray tube 1B, a large current area (area where image brightness is high) compared to the other two colors.
The brightness in the field will drop significantly. Therefore, in order to match the other two emission characteristics with the emission characteristics of a particular single-color projection cathode ray tube among red, green, and blue, the characteristics are made uniform by adding γ correction to the drive characteristics.

Specifically, regarding the red and green projection cathode ray tubes, the drive voltage of the drive circuit with respect to the input voltage is corrected by the broken line correction as shown in the figure, as indicated by broken lines L _R 'and L _G ' in FIG. Correct so that That is, the characteristics of the red and green projection cathode ray tubes are arranged so as to be similar to the emission characteristics of the blue projection cathode ray tube. This polygonal line correction is performed at the output stage of the video signal processing circuit 4 in FIG. Here, in addition to the normal low light and high light of the video, correction is performed by changing the amplification factor of the transistor of the drive circuit at 2 to 4 points which are generally intermediate brightness.

FIG. 7 is a diagram showing the configuration of the transistor amplifier circuit in the video signal processing circuit 4. In the transistor TR1 having the collector resistance R1 and the emitter resistance R2, one of the diodes D1, D2, and D3 is made conductive via the resistances R3, R4, and R5 connected to the emitter, depending on the input signal level to the base. I am trying to let you. That is, the cathodes of the diodes D1 to D3 are connected to the power sources V1 to V3 via analog switches (not shown), respectively. Then, one of the analog switches is closed to supply power to the emitter of the transistor TR1.

In this way, the emitter resistance value of the transistor TR1 changes, and the amplification factor of the transistor TR1 changes stepwise. For example, when the emitter voltage of the transistor TR1 is higher than V1, the diode D1 becomes conductive,
The base input signal is converted into a drive voltage with an amplification factor determined by the values of the resistors R1 and R3.

As an actual white balance adjustment, a polygonal line correction circuit for each of the characteristic curves shown in FIG. 6 is provided in the video signal processing circuit 4 to perform the polygonal line correction according to the emission characteristics of each monochromatic projection cathode ray tube. The resistance values R3, R4, and R5 are adjusted in balance with highlight adjustment so that the amplification factor of each point and the drive voltage match.

In some cases, the above adjustment is automatically performed. As shown in FIG. 5, in order to capture an image formed on the screen 3, a light receiving element 5 for optically detecting its brightness (light amount) is arranged. Then, as a display image of each monochromatic projection cathode ray tube 1, a rectangular window pattern P is projected on the screen 3 as shown in FIG. Then, the white window pattern creating circuit 6 is connected to the video signal processing circuit 4. The white window pattern creating circuit 6 creates a window pattern signal in synchronization with the scanning frequency and outputs low-light, middle-light and highlight brightness signals, respectively. Then, the level / color switching circuit 7 switches the display for each of the single colors of red, green, blue, and white that is a mixture thereof, and the light-receiving element 5 outputs the amount of light emitted from each single-color projection type cathode ray tube 1R, 1G, 1B. Is detected at each gradation.

Next, the arithmetic circuit 8 calculates a relative amount of light so that a white color having a predetermined light amount ratio is obtained.
The feedback signal is given to the video signal processing circuit 4. In this way, the level control of low light adjustment, middle light adjustment, and highlight adjustment is performed, and the overall white balance from low light to high light is adjusted.

[0015]

The white balance adjustment as described above can be performed by a low light, a middle light, or a highlight either by a method visually performed by an operator or by an automatic adjustment method using a light receiving element. Is done at each brightness. In addition, the above-mentioned polygonal line correction also applies to the characteristic curve 2
It is performed so that the relative light emission characteristics are aligned at four points. However, as shown in FIG. 6, the emission characteristics of each of the red, blue, and green monochromatic projection cathode ray tubes have a complicated correlation, and in particular, a device often used in a large current region such as a projection display device. Then, it is hard to say that the adjustment of the white balance is satisfactory in the entire area by just aligning the specific 2 to 4 points on the characteristic curve.

Further, although it is easy to increase the number of polygonal line correction points, it is not superior in terms of complicated adjustment, and such a method is not realistic in view of simplification of adjustment. Further, the spectral distribution of the lens 2 causes a change in the spectral distribution after passing. In addition, the spectral distribution changes due to the influence of the reflection screen in the front projection type or the transmission screen in the rear projection type. Further, the conventional white balance adjusting method considers only the light emission characteristics of the cathode ray tube which is a display device, and is used as the white balance adjustment of the projection type display device in which the lens 2 and the screen 3 are interposed as a display system. Is insufficient.

The present invention has been made in view of such conventional problems, and the white balance of each of the red, green, and blue monochromatic cathode ray tubes can be automatically adjusted, and the monochromatic cathode ray tubes can be adjusted. It is an object of the present invention to provide an automatic white balance adjusting device capable of extremely accurately adjusting white balance in the entire drive voltage range.

[0018]

According to the first aspect of the present invention, the three primary colors of red, green and blue monochromatic cathode ray tubes are additively mixed,
A white balance automatic adjusting device used for a color television display device for outputting a color image on a display screen, and a brightness level changing means for changing an input signal of a monochromatic cathode ray tube into a plurality of levels from low light to high light. And an optical measuring means for optically measuring the brightness on the display screen and a monochromatic cathode ray tube driven by changing the input signal by the brightness level varying means respectively, on the display screen measured by the optical measuring means. The storage means for storing the measured data of the luminance level of the input signal, and the red, green, and blue signals of the image input from the outside, the input signal is corrected based on the data stored in the storage means, and the drive voltage is changed for each single color. And a video signal processing means for outputting to a cathode ray tube.

In the invention of claim 2 of the present application, the video signal processing means inputs from low light to high light of each color of red (R), green (G) and blue (B) stored in the storage means. A function f representing the luminance characteristics of red, green, and blue on the display screen from the luminance measurement data on the display screen with respect to the change of the signal x.
Luminance characteristic calculation means for obtaining _R (x), f _G (x) and f _B (x) respectively, and a function f output by the luminance characteristic calculation means.
_{Of R} (x), f _G (x), and f _B (x), the function f ₁ (x) indicating the luminance characteristic of the specific first color is used as a reference, and the other second and third colors Function f ₂ (x), f indicating the luminance characteristic
Correlation function g ₂ (x) = f ₁ (x) / f ₂ for matching the luminance characteristics of the second and third monochrome cathode ray tubes with the luminance function of the first color using ₃ (x) (X), g ₃ (x) = f
Correlation function computing means for computing ₁ (x) / f ₃ (x) respectively, and correlation function g ₂ (x), output by the correlation function computing means,
The correlation function g ₂ (x) is used to correct the luminance characteristics of the second and third monochromatic cathode ray tubes by using g ₃ (x) and drive the first to third monochromatic cathode ray tubes at the same time to obtain white. , G ₃ (x) by multiplying the first and second drive ratios k ₂ and k ₃ , respectively, and input signals x _{1 to} x indicating the brightness levels of the first to third monochromatic colors. ₃ are input respectively, and the correlation functions g ₂ (x) and g ₃ (x) output by the correlation function calculating means and the drive ratio calculating means of the second and third input signals x ₂ and x ₃ are input. Output drive ratio k ₂ , k ₃
And a video signal processing circuit for generating a drive voltage for each of the first to third monochromatic cathode ray tubes by multiplying each of the above.

In the invention of claim 3 of the present application, the video signal processing means inputs from the low light of each single color of red (R), green (G) and blue (B) stored in the storage means to highlight. A function f representing the luminance characteristics of red, green, and blue on the display screen from the luminance measurement data on the display screen with respect to the change of the signal x.
Luminance characteristic calculation means for obtaining _R (x), f _G (x) and f _B (x) respectively, and a function f output by the luminance characteristic calculation means.
_{Of R} (x), f _G (x) and f _B (x), the function f _G (x) showing the luminance characteristic of green is used as a reference, and the function f _R (x) showing the luminance characteristic of red and blue is shown. Using f _B (x), a correlation function g _R (x) = f _G (x) / f for matching the luminance characteristics of the red and blue monochromatic cathode ray tubes with the green luminance function f _G (x)
_{R (x), g B (} x) = f G (x) / f B and correlation function calculating means for respectively calculating the (x), the correlation function g _R to the output of the correlation function calculation means (x), g _B ( x) is used to correct the luminance characteristics of the red and blue monochromatic cathode ray tubes, and the correlation function g _{R is set} so that the green, red and blue monochromatic cathode ray tubes are simultaneously driven to become white.
Red and blue drive ratio k by which (x), g _B (x) are multiplied
Drive ratio calculation means for determining _R and k _B respectively, green,
The input signals x _G , x _R , and x _B indicating the brightness levels of red and blue are input, respectively, and the correlation function g _R (output from the correlation function calculating means with respect to the red and blue input signals x _R and x _B x), g
_B (x) and a video signal processing circuit for multiplying the drive ratios k _R and k _B output from the drive ratio calculating means to generate drive voltages for the green, red and blue monochromatic cathode ray tubes. It is characterized by that.

[0021]

According to the present invention having such characteristics, the red, green, and blue luminance characteristics of the monochromatic cathode ray tube are compared with the input luminance signal before the actual video signal is input to the color television display device. to correct. First, the brightness level varying means generates a pattern signal synchronized with the scanning frequency, and varies the drive voltage for driving the monochromatic cathode ray tube into a plurality of levels from low light to high light. The optical measuring means optically measures the brightness on the display screen. The storage means
The measurement data of the brightness level at each stage from low light to high light of the display image is converted into a digital signal and the data is stored. Then, the video signal processing means corrects the input signal for the R, G, B signals of the video input from the outside based on the data stored in the storage means, and outputs the drive voltage to each monochromatic cathode ray tube. In this way, the brightness characteristics on the screen of each of the monochromatic cathode ray tubes are the same for all of red, green and blue, and the white balance is adjusted automatically and extremely accurately in the entire drive voltage range.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An automatic white balance adjusting apparatus according to a first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a block diagram showing the overall configuration of a white balance automatic adjustment apparatus according to the first embodiment of the present invention. The same parts as those in FIG. 5 showing the conventional example are designated by the same reference numerals, and the description thereof will be omitted. In this figure, red, green and blue projection cathode ray tubes 1
R, 1G, and 1B are arranged in parallel and form an image output unit. The magnifying lenses 2R, 2G, 2B are the cathode ray tubes 1
The image emitted from R, 1G, and 1B is enlarged and imaged on the screen 3.

The optical measuring device 10 is a device for measuring the brightness and hue of the image pattern for white balance adjustment projected on the screen 3, and is arranged in front of the screen 3. The sample hold (S / H) circuit 11 is used for the optical measuring device 10.
Is a circuit for temporarily holding the output signal of. The A / D converter 12 is a circuit that converts the output of the S / H circuit 11 into a digital signal.

The operation unit 13 is an input unit for instructing the start of white balance adjustment. The system control unit 14 is a CPU
When a white balance adjustment start signal is given from the operation unit 13, the color level switching control signal, the brightness level control signal, the operation control signal of the light emission characteristic operation circuit described later,
And a circuit for outputting other control signals. The brightness level changing means 14a in the system control unit 14 is a brightness means for changing the drive drive voltage of each monochromatic cathode ray tube 1 to a plurality of levels from low light to high light.

When the white window pattern creating section 15 receives a control signal from the brightness level varying means 14a in the system control section 14, it synchronizes with the vertical synchronizing signal (VD) and the horizontal synchronizing signal (HD) of the image. This is a circuit for generating a test signal such as a rectangular monochromatic pattern. The signal switching circuit 16 is a circuit that switches the R, G, B signals input from the outside and the test signal input from the white window pattern creating unit 15 and outputs the signals to the video signal processing circuit 17.

The video signal processing circuit 17 is a signal switching circuit 1
The signal levels of the R, G, and B signals output by 6 are corrected, and the drive voltage is changed to the projection type cathode ray tube 1R, 1G, 1
It is a circuit for outputting to B.

Now, three types of monochromatic cathode ray tubes 1R, 1B,
Consider the luminance characteristics of 1G. The input signal of the cathode ray tube 1 and x, when the luminance data at that time and y, the cathode ray tube 1 for a plurality of input signals x _i, a plurality of luminance data _{y i ((x 1, y} 1), (x ₂ , y ₂ ), ‥‥‥‥‥‥‥‥‥‥
(X _n , y _n )) shall be obtained.

The red, green, and blue luminance characteristics for the input signal x thus obtained are respectively represented by f _R (x), f
Let _G (x) and f _B (x). In the calculation process for obtaining this function, f _R (x),
Formulas of f _G (x) and f _B (x) are obtained. This function is obtained as a cubic function from the shapes of L _R and L _{B in} FIG. Next, x = 0 is the limiting of low light are substituted into these formulas, it obtains the offset amount O _R, O _G, and O _B. This value corresponds to the white balance adjustment amount in low light.

Next, in order to match the functions f _R (x) and f _B (x) with the bright function f _G (x), the function f
_R (x), performing a calculation shown below using _{f B (x), f G} (x).

[0030] _{F G (x), F R} (x), correlating the F _B (x) function _{g R (x), g B} (x) G after receiving the correction by, R, on the screen of the B As a function of the luminance characteristic of, the following equations (1) to (3) are established.

F _G (x) = f _G (x) (1) F _R (x) = f _R (x) × g _R (x) = F _G (x) (2) F _B (x) = f _B (x) × g _B (x) = F _G (x) (3) That is, F _G (x) = F _R (x) = F _B (x) Then, the correlation functions g _R (x) and g _B (x) are determined.

That is, assuming that the correlation functions of the R and B signals with respect to the G signal are g _R (x) and g _B (x), respectively, the correlation functions are expressed by the following equations (4) and (5).

## EQU00002 ## g _R (x) = f _G (x) / f _R (x) ... (4) g _B (x) = f _G (x) / f _B (x) ... (5) The RAM 18 stores the correlation function g thus obtained.
It is a memory that temporarily holds _R (x) and g _B (x).

Next, the brightness measurement data stored in the RAM 18 is read out and the functions F _R (x), F _B (x) and F _G are read.
The drive ratios k _R and k _B are calculated so that when the respective images of the three cathode ray tubes 1 are simultaneously emitted using (x) (= f _G (x)), white is displayed on the screen 3. That is, the drive ratios k _R and k _B are determined so that the relationship F _G (x) = F _R (x) / k _R = F _B (x) / k _B is established.

Here, assuming that the input / output transmission relations of the luminance characteristics of driving the green, red and blue projection type cathode ray tubes at the same time to be white are F _G , F _R 'and F _B ', respectively, the following relational expression is obtained. To establish.

## EQU00003 ## F _G (x) = f _G (x) ... (6) F _R '(x) = k _R × {g _R (x) × f _R (x)} ... (7) F _B '(x) = k _B × {g _B (x) × f _B (x)} (8)

The video signal processing circuit 17 uses the characteristic function, the offset amount, the correlation function, and the drive ratio calculated as described above to perform the following calculation.

The EEPROM 19 is a non-volatile memory that stores the coefficients a, b, c and d when the correlation function g (x) stored in the RAM 18 is expressed as ax ³ + bx ² + cx + d. Here, RAM 18 and EEPROM 1
Reference numeral 9 constitutes a storage means for storing the measurement data.
The light emission characteristic calculation circuit 20 is a circuit which reads each coefficient stored in the EEPROM 19 and uses the drive ratio k to calculate the following equations (9) and (10).

That is, when a function obtained by multiplying the correlation function g (x) by the drive ratio k is g '(x),

Equation 4] g '(x) = k ( ax 3 + bx 2 + cx + d) ······ (9) = k {x (ax 2 + bx + c) + d} ········ (10) = k {x (α ₁ x + β ₁ ) (α ₂ x + β ₂ ) + d} ... (11) where α ₁ α ₂ = a α ₁ β ₂ + β ₁ α ₂ = b β ₁ β ₂ = c

Here, the light emission characteristic calculation circuit 20 uses the luminance characteristic calculation means 20a for obtaining the respective functions representing the red, green and blue luminance characteristics on the display screen, and the green luminance from the red, green and blue functions. Correlation function calculating means 20b for obtaining a correlation function for matching the function showing the red and blue luminance characteristics with the function for green on the basis of the function showing the characteristic, and the correlation function for synthesizing each single color to be white Drive ratio calculation means 20c for determining the drive ratios of red and blue by which g _R (x) and g _B (x) are respectively multiplied, and the coefficients a, b, c and d of the correlation function g (x).
The function of the coefficient calculating means 20d for calculating is achieved.

FIG. 2 is a block diagram showing the internal structure of the video signal processing circuit 17 in the first embodiment. In FIG. 2, the first operational amplifier 17a is a circuit that multiplies the input signal x indicating the brightness level by a linear function (α ₁ x + β ₁ ). The second operational amplifier 17b is the operational amplifier 17a.
It is a circuit that multiplies the output of by a linear function (α ₂ x + β ₂ ). The low light adjustment unit 17c is a circuit that corrects the output level of each R, G, and B when the brightness is low, and includes an operational amplifier 17c.
It is a circuit that adds a constant d to the output of b. The highlight adjustment unit 17d is a circuit that corrects the output level of each R, G, and B at high brightness, and is a circuit that multiplies the output of the low adjustment unit 17c by a constant k.

The arithmetic control circuit 21 performs D / A conversion of various digital correction coefficients output from the system control unit 14 on the basis of control signals such as contrast and brightness output from the system control unit 14 to obtain a constant a, The circuit outputs analog signals b, c, d, and k to the video signal processing circuit 17.

The operation of the white balance automatic adjusting apparatus of the first embodiment having the above-described structure will be described. First, when an instruction to start white balance adjustment is given from the operation unit 13, the system control unit 14 outputs a control signal. The white window pattern creating unit 15 generates a window pattern signal as a test signal for white balance adjustment, and the signal switching circuit 16
Output to. Then, the signal switching circuit 16 switches the externally input RGB signal for displaying a general image to the white balance adjustment mode, and gives the window pattern signal to the image signal processing circuit 17.

First, to project a red window pattern,
The brightness level varying means 14a of the system control unit 14 gives the white window pattern creating unit 15 an instruction to project red as a color level switching control signal. For example, a level signal having a voltage of several tens of levels is given to the white window pattern creating unit 15. At the beginning, a control signal for instructing the low light level is given. The lowest level red window pattern projected in this manner is projected on the screen 3.

Next, the system controller 14 gives an instruction for measuring the brightness of the red window pattern, and the optical measuring instrument 10 measures the brightness of the window pattern. This measurement result is S / H
It is temporarily held in the circuit 11 and converted into a digital signal by the A / D converter 12. These measurement data are stored in the RAM 18 via the light emission characteristic calculation circuit 20. When one level measurement is completed, a control signal indicating the next level is sent from the system control section 14 to the brightness level changing means 14
It is subsequently output via a. In this way, from the low light to the highlight, a red window pattern having a brightness level of several tens of points is displayed, the brightness on the screen 3 at that time is measured by the optical measuring device 10, and the data is stored in the RAM 18. To be done. Similarly, green and blue window patterns having several tens of brightness levels are displayed, and their brightness data are stored in the RAM 18.

When the measurement of the brightness of the color window patterns of the three types of single-tube cathode-ray tubes 1 is completed in this way, the system controller 14
Transfers the brightness data stored in the RAM 18 to the light emission characteristic calculation circuit 20. In the light emission characteristic calculation circuit 20, assuming that an input signal serving as a drive voltage of the cathode ray tube 1R is x and luminance data at that time is y, a plurality of stored data ((x ₁ , y ₁ ), (x ₂ , y ₂ ) 、 ‥‥‥‥‥‥
From (x _n , y _n )), a relational expression expressing the brightness characteristic on the screen with respect to the change of the input signal of the red cathode ray tube 1R is calculated. This relational expression is similarly measured and calculated for the cathode ray tubes 1B and 1G.

The light emission characteristic calculation circuit 20 calculates the luminance characteristics f _R (x), f of red, green and blue obtained by using the method of least squares.
_G (x), and f _B (x), the offset amount O _R, O _G, O
Store _B in RAM 18. Next, the light emission characteristic calculation circuit 20
Is the function f _R (x), f _B (x) with high brightness f _G
In order to match with (x), the functions f _R (x), f _B (x), f _G (x) stored in the RAM 18 are read,
Using the equations (4) and (5), the correlation function g _R (x), g
_{Find B} (x). And these correlation functions g
_R (x) and g _B (x) are stored in the RAM 18 again.

Next, the luminance measurement data stored in the RAM 18 is transferred to the light emission characteristic calculation circuit 20. Then, the light emission characteristic calculation circuit 20 uses the equations (7) and (8) to calculate
The drive ratios k _R and k _B are calculated so that a white window pattern can be obtained on the screen 3 when the cathode ray tubes 1G, 1R and 1B are driven by F _G , F _R 'and F _B '. Furthermore, the light emission characteristic calculation circuit 20 uses the coefficient a,
b, c and d are calculated respectively and stored in the EEPROM 19. Next, the arithmetic control circuit 21 retrieves each coefficient stored in the EEPROM 19 through the light emission characteristic arithmetic circuit 20,
Coefficients α ₁ , β ₁ , α ₂ , β ₂ are converted to D / A
It is converted and given to the video signal processing circuit 17 in FIG.

That is, the coefficients α ₁ and β ₁ are given to the operational amplifier 17a, and the coefficients α ₂ and β ₂ are given to the operational amplifier 17b. When the signal x is input, the operational amplifier 17a multiplies the signal x by the coefficient α ₁ and adds the coefficient β ₁ , and further multiplies the generated linear expression (α ₁ x + β ₁ ) by the value of the signal x.
Next, the operational amplifier 17b outputs the output x of the operational amplifier 17a.
To _{(α 1 x + β 1)} , multiplied to generate a linear expression _{(α 2 x + β 2)} , x (α 1 x + β 1) (α 2 x + β 2) and outputs a.

The arithmetic control circuit 21 also supplies the coefficient d to the low light control unit 17c and the coefficient k to the highlight control unit 1
Give to 7e respectively. The low light control unit 17c adds a coefficient d corresponding to the offset amount O to the output of the operational amplifier 17b. Further, the highlight controller 17d outputs the output x (α ₁ x + β ₁ ) (α ₂ x + β ₂ ) of the low light controller 17c.
+ D is multiplied by the drive ratio k, and the value of the correlation function g ′ shown in the equation (11) is output.

[0048] Thus the correction represented by controlling the various adjustment functions of the video signal processing circuit 17 with the function g _'R (x) can be carried out on the luminance signal x red. Hereinafter, the same correction calculation is performed for green and blue as in the case of red described above. Here, the video signal processing circuit 17, the light emission characteristic calculation circuit 20, and the calculation control circuit 21 respond to the R, G, and B signals of the image input from the outside by the RAM 18, EEPRO.
A video signal processing means 22 for correcting the signal level based on the data stored in M19 and outputting the drive voltage to each of the monochromatic cathode ray tubes 1R-1B is configured.

After correcting the above three colors, each luminance is automatically measured again. In other words, the light emission characteristic calculation circuit 20 checks whether or not the light becomes white from low light to high light. When the comparison result is not within the specified range, the same calculation and correction are performed again, and when the result of the automatic measurement is within the specified value, the correction is finished. The various coefficients at this time are stored in the EEPROM 19 as saved data, and all the processes are completed.

Next, an automatic white balance adjusting apparatus according to the second embodiment of the present invention will be described with reference to FIG.
FIG. 3 is a block diagram showing the configuration of the main part of the white balance automatic adjustment apparatus according to the second embodiment of the present invention.
The same parts as those in FIG. 1 of the first embodiment are designated by the same reference numerals,
The description is omitted. In the figure, a video signal input / output circuit 30 is a circuit which inputs an uncorrected R, G, B luminance signal and outputs a brightness-corrected R, G, B luminance signal. The signal level determination circuit 31 is the video signal input / output circuit 30.
Is a circuit for determining the level of the luminance signal output by the.

Third to fifth operational amplifiers 32, 33, 34
Is a circuit for calculating the cube, square, and square of the input signal x. On the other hand, the EEPROM 19 has a correction coefficient a,
It is a non-volatile memory that stores b, c, d, and k, and is calculated and stored in the same manner as the first correction method described above. The D / A converter 35 is a circuit that converts the correction coefficients a, b, c, d, and k read by the EEPROM 19 into analog values, and is included in the arithmetic control circuit 21 of FIG. The sixth operational amplifier 36 outputs the correction coefficient a output from the operational amplifier 32 and the D / A converter 35.
Is a circuit for multiplying by. Similarly, the seventh and eighth operational amplifiers 37 and 38 are circuits for multiplying the outputs of the operational amplifiers 33 and 34 by the correction coefficients b and c output from the D / A converter 35, respectively.

Next, the adder 39 includes operational amplifiers 36 to 38.
It is a circuit for adding each of the outputs and the correction coefficient d output from the D / A converter 35. The multiplier 40 is a circuit that multiplies the output of the adder 39 by the correction coefficient k output by the D / A converter 35. The DC control circuit 41 is a circuit which receives the signal from the multiplier 40, converts it into a drive voltage for the cathode ray tubes 1R, 1G and 1B, and outputs it to the video signal input / output circuit 30.

A second correction method of the white balance automatic adjusting apparatus of the second embodiment having the above-mentioned structure will be described by taking red correction as an example. First, the EEPROM 19
The coefficients a, b, c, of the correlation function g _R (x) stored in
d and the drive ratio k _R are read by the control signals of the system control unit 14 and converted into analog signals by the D / A converter 35.

The red luminance signal input to the video signal input / output circuit 30 is applied to the signal level determination circuit 31 and the signal level is converted. The converted signal x is input to operational amplifiers 32, 33 and 34, and the values of x ³ , x ² and x are calculated respectively. Next, these operation results and the analog-to-analog converted correction data a, b, and c are used as operational amplifiers 36 to 38.
Are respectively input to and multiplication is performed. Further, the correction coefficient d is added to the calculation result by the adder 39, and the added value is given to the multiplier 40 and is multiplied by the drive ratio k _R. This calculation is to obtain the value of k _R × g _R (x) in real time for the luminance signal input to the video signal input / output circuit 30.

Now, the analog operational amplifiers 32 to 34,
Instead of using 36 to 38, the adder 39, and the multiplier 40, there is also a method of correcting using digital means as shown in FIG. FIG. 4 is a block diagram showing the configuration of the main part of the white balance automatic adjustment apparatus in the third example of the present invention. The same parts as those in FIG. 3 of the second embodiment are designated by the same reference numerals, and the description thereof will be omitted. In the figure, an S / H circuit 51 is provided with R,
It is a circuit that judges the levels of the G and B luminance signals and temporarily holds the level-converted signal x. A / D converter 52
Is a circuit for converting the output signal x of the S / H circuit into a digital signal.

The digital arithmetic circuit 53 is the EEPROM 1
Using the coefficients a, b, c, d, and k stored in 9 (9)
It is a circuit that calculates the operation shown in the equation by digital processing.
The D / A converter 54 is a circuit that converts the output of the digital arithmetic circuit 53 into an analog signal and supplies it to the DC control circuit 41.

R input to the video signal input / output circuit 30,
The G and B luminance signals are held by the S / H circuit 51 at the sampling clock cycle, digitally converted by the A / D converter 52, and input to the digital arithmetic circuit 53. The EEPROM 19 is controlled by the control signal from the system controller 14.
The coefficients a, b, c, d and k are read out from and input to the digital arithmetic circuit 53. The second in the digital arithmetic circuit 53
The same calculation as the analog calculation of the embodiment is performed digitally. That is, for the signal x of each sampling period, k ·
The value of {ax ³ + bx ² + cx + d} is calculated. Then, the data is analog-converted by the D / A converter 54,
It is output to the DC control circuit 41. And the DC control circuit 4
1, the output drive voltage of the video signal input / output circuit 30 is continuously adjusted with respect to the change of the input signal level.

Hereinafter, the same correction as for red is performed for green and blue. Then, the brightness is automatically measured again. That is, the arithmetic circuit 43 performs an inspection as to whether or not it becomes white from low light to high light. If the comparison result is not within the specified range, the same calculation and correction are performed again, and the correction is ended when the result of the automatic measurement is within the specified value. Various coefficients at this time are stored as EEPRO.
Store in M19 and end all processing.

The luminance characteristic f of the green cathode ray tube 1G
_With reference to _G (x), the red and blue correlation functions g _R (x),
Although g _B (x) is set, the reference cathode ray tube may be red or blue.

[0060]

As described above, according to the present invention, red, green,
The white balance of each blue monochromatic cathode ray tube can be automatically adjusted, and the white balance can be adjusted extremely accurately in the entire drive voltage range from the low light to the highlight level of each monochromatic cathode ray tube. Therefore, a color image with extremely good color reproducibility in the projection display device can be obtained, and the effect of significantly improving the quality of the display image can be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram showing an overall configuration of a white balance automatic adjustment device according to first to third embodiments of the present invention.

FIG. 2 is a block diagram showing a configuration of a video signal processing circuit used in the first embodiment of the present invention.

FIG. 3 is a block diagram showing a configuration of a video signal processing means used in a second embodiment of the present invention.

FIG. 4 is a block diagram showing a configuration of a video signal processing means used in a third embodiment of the present invention.

FIG. 5 is a block diagram showing an example of a conventional white balance automatic adjustment device.

FIG. 6 is a characteristic diagram showing drive voltage versus screen brightness characteristics of a monochromatic projection cathode ray tube.

FIG. 7 is a circuit diagram showing a configuration of a polygonal line correction circuit in a conventional white balance automatic adjustment device.

FIG. 8 is an explanatory diagram of a white window pattern signal.

[Simple explanation of symbols]

 1R, 1G, 1B Projection type cathode ray tube 2R, 2G, 2B Magnifying lens 3 Screen 10 Optical measuring device 11, 51 S / H circuit 12, 52 A / D converter 13 Operation part 14 System control part 14a Brightness level changing means 15 White window pattern creation section 16 Signal switching circuit 17 Video signal processing circuit 17a, 17b, 32-34, 36-38 Operational amplifier 17c Low light adjustment section 17d Highlight adjustment section 18 RAM 19 EEPROM 20 Light emission characteristic calculation circuit 20a Luminance characteristic calculation Means 20b Correlation function operation means 20c Drive ratio operation means 20d Coefficient operation means 21 Operation control circuit 22 Video signal processing means 30 Video signal input / output circuit 31 Signal level determination circuit 35, 54 D / A converter 39 Adder 40 Multiplier 41 DC control circuit 53 Digital operation circuit

Claims (7)

[Claims] 1. A white balance automatic adjusting device used in a color television display device for additively mixing the three primary colors of red, green and blue monochromatic cathode ray tubes and outputting a color image on a display screen. Luminance level changing means for changing the input signal of the cathode ray tube into a plurality of levels from low light to highlight, an optical measuring means for optically measuring the brightness on the display screen, and the monochromatic cathode ray tube, respectively. Storage means for storing the measured data of the brightness level on the display screen measured by the optical measuring means when driven by changing the input signal by the brightness level varying means, and red and green of the image inputted from the outside. , A video signal processor for correcting the input signal for the blue signal based on the data stored in the storage means and outputting the drive voltage to each of the monochromatic cathode ray tubes. If, automatic white balance adjustment device characterized by comprising a. 2. The video signal processing means responds to changes in an input signal x from low light to high light of each color of red (R), green (G) and blue (B) stored in the storage means. A function f that represents the brightness characteristics of red, green, and blue on the display screen from the brightness measurement data on the display screen.
Luminance characteristic calculation means for obtaining _R (x), f _G (x) and f _B (x) respectively, and a function f _R (x), f _G output by the luminance characteristic calculation means.
Of (x) and f _B (x), a function f ₁ (x) showing the luminance characteristic of a specific first color is used as a reference, and a function f ₂ showing the luminance characteristic of other second and third colors is used. Using (x) and f ₃ (x),
Correlation function g ₂ (x) = f for matching the luminance characteristics of the second and third monochromatic cathode ray tubes with the luminance function of the first color.
₁ (x) / f ₂ (x), g ₃ (x) = f ₁ (x) / f ₃
Correlation function calculating means for calculating (x) respectively, and correlation function g ₂ (x), output from the correlation function calculating means,
The correlation function g ₂ (x) is used to correct the luminance characteristics of the second and third monochromatic cathode ray tubes by using g ₃ (x) and drive the first to third monochromatic cathode ray tubes at the same time to obtain white. , G ₃ (x) by multiplying the first and second drive ratios k ₂ and k ₃ , respectively, and input signals x _{1 to} x indicating the luminance levels of the first to third monochromatic colors.
_{3 respectively,} and the correlation function g output from the correlation function calculating means with respect to the second and third input signals x ₂ and x ₃ .
₂ (x) and g ₃ (x) are multiplied by the drive ratios k ₂ and k ₃ output from the drive ratio calculating means, respectively, to obtain the first
3. A white balance automatic adjusting apparatus according to claim 1, further comprising: a video signal processing circuit for generating a drive voltage for a third monochromatic cathode ray tube. 3. The video signal processing means responds to changes in the input signal x from low light to high light of each color of red (R), green (G) and blue (B) stored in the storage means. A function f that represents the brightness characteristics of red, green, and blue on the display screen from the brightness measurement data on the display screen.
Luminance characteristic calculation means for obtaining _R (x), f _G (x) and f _B (x) respectively, and a function f _R (x), f _G output by the luminance characteristic calculation means.
Of (x) and f _B (x), a function f _G indicating the luminance characteristic of green
A function f indicating the luminance characteristics of red and blue with reference to (x)
_{Using R} (x) and f _B (x), a correlation function g _R (x) = f _G (for matching the luminance characteristics of the red and blue monochromatic cathode ray tubes with the green luminance function f _G (x). x) / f _R (x), g _B
(X) = f _G (x) / f _B (x) respectively, and a correlation function g _R (x), which is output from the correlation function calculation means.
Using g _B (x), the luminance characteristics of the red and blue monochromatic cathode ray tubes are corrected, and the correlation functions g _R (x) and g are obtained so that the green, red, and blue monochromatic cathode ray tubes are simultaneously driven to become white. Drive ratio calculating means for respectively determining red and blue drive ratios k _R and k _{B by} which _B (x) is multiplied, and input signals x _G , x _R and x indicating the brightness levels of green, red and blue.
The _B and respectively input, the red, the input signal of the blue x _R, with respect to x _B, the correlation function output of said correlation function computing means g
_R (x), g _B (x) and the drive ratios k _R and k _B output from the drive ratio calculating means are multiplied to obtain green,
2. An automatic white balance adjusting apparatus according to claim 1, further comprising a video signal processing circuit for generating a drive voltage for the red and blue monochromatic cathode ray tubes. 4. When the correlation function g (x) output from the correlation function calculating means is expressed as g (x) = ax ³ + bx ² + cx + d using the input signal x generated by the brightness level varying means, Coefficient calculating means for calculating the coefficients a, b, c, d of, a non-volatile memory for storing the coefficients a, b, c, d output by the coefficient calculating means, and the correlation function as g (x) = { x (α ₁ x + β ₁ ) (α ₂
x + β ₂ ) + d}, the coefficient α ₁ , b, c, d stored in the non-volatile memory is used to obtain the coefficient α ₁ ,
An arithmetic control circuit for calculating α ₂ , β ₁ , β ₂ and converting these coefficients into an analog signal; a first operational amplifier for inputting an input signal x and multiplying by (α ₁ x + β ₁ ); The output of the first operational amplifier is (α ₂
x + β ₂ ), a second operational amplifier, a low light adjusting unit that adds the coefficient d to the output of the second operational amplifier, and a highlight adjusting unit that multiplies the output of the low light adjusting unit by a drive ratio k. A video signal processing circuit having :, A white balance automatic adjusting apparatus according to claim 2 or 3, characterized in that: 5. When the correlation function g (x) output from the correlation function computing means is expressed as g (x) = ax ³ + bx ² + cx + d using the input signal x generated by the brightness level varying means, these Coefficient computing means for computing the coefficients a, b, c, d of the above, a non-volatile memory for storing the coefficients a, b, c, d output by the coefficient computing means, and a non-volatile memory for the non-volatile memory with respect to an input signal x. Using the output coefficients a, b, c, d, a third operational amplifier that calculates ax ³ , a fourth operational amplifier that calculates bx ² , a fifth operational amplifier that calculates cx, and the third to third 5. An image signal processing circuit including: an adder for adding each output of the operational amplifier of 5 to the coefficient d; and a multiplier for multiplying the output of the adder by a drive ratio k. Alternatively, the white balance automatic adjustment device described in item 3. 6. When the correlation function g (x) output from the correlation function computing means is expressed as g (x) = ax ³ + bx ² + cx + d using the input signal x generated by the brightness level varying means, The coefficient function g (x) = ax ³ + bx ² + cx + d is calculated by using the coefficient calculating means for calculating the coefficients a, b, c, d of and the coefficients a, b, c, d output by the coefficient calculating means. 4. The automatic white balance adjusting device according to claim 2, further comprising a video signal processing circuit that performs digital signal processing for multiplying this value by the drive ratio k. 7. A window pattern creating means for displaying an input signal for measuring the luminance characteristic of each monochromatic cathode ray tube by displaying each monochromatic window pattern and a white white window pattern in which each monochromatic color is combined on the display screen. The automatic white balance adjusting device according to claim 1, further comprising: