JPH04103286A - Color correction circuit for color television camera - Google Patents

Abstract

PURPOSE:To simplify an adjustment by providing a means selecting a coefficient to be multiplied with each color difference signal depending on the polarity of each color difference signal between two color signals in three primary color signals and multiplying the coefficient with the color difference signal and a means adding the each color difference signal multiplied with the coefficient to a relevant color signal of the three primary color signals. CONSTITUTION:Subtractors 7-9 output color difference signals R-G, G-B, B-R respectively, and when the output is positive, switches 19-21 select coefficients K1, K2, K3 and they are multiplied with each of relevant color difference signals by multipliers 22-24. Then each output of the multipliers 22-24 is added to G, B, R signals by adder circuits 30, 32, 29. On the other hand, when any of the outputs 7-9 is negative, the switches 25-27 is switched as shown in dotted lines and the output of the multipliers 22-24 is added to each of the R, G, B signals by adders 28, 31, 33. Since a hue adjustment coefficient of each of the R, G, B color signals is provided independently, the hue is singly and simply adjusted.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a signal processing circuit for a color television camera.

[Summary of the invention]

The present invention aims to simplify the hue adjustment of a color television camera and to rationalize the circuit, which is a disadvantage of the conventional hue adjustment circuit called a linear matrix system. This is intended to improve the problem that the circuit scale is large and that when trying to adjust the hue of a certain color (for example, R), this effect extends to other colors (G?B), making it difficult to adjust.

The present invention provides y C1-Cj (C1l CjE R+ G
rB) This method facilitates two-hue adjustment by distinguishing between the positive and negative components of the color difference signal, multiplying them by appropriate coefficients, and adding and subtracting the corresponding Ci and Cj multiplied signals. , and also to improve the increase in the scale of two circuits due to the large number of multipliers, which is a problem when digitizing the circuit.

[Conventional technology]

In Figure 2, a prism optical system was used. An example of a color television camera is shown. The optical signal from the subject passes through the lens 31 and is converted into R (red), 3G (green), and B (
blue), and image sensors 33 to 35 for each color
The signal is converted into R, G, and B electrical signals. Normally, the spectral sensitivity characteristics of this prism 32 are as shown in FIG. 3(A). Although the ideal spectral sensitivity characteristic is one in which there is no overlap of R, G, and H as indicated by diagonal lines, it is actually very difficult to obtain such a prism 32.

Therefore, even when photographing a bright red subject.

Some of the light reaches the G and B image sensor 34.35 and 3G
and B as electrical signals.

Therefore, in the output image of this camera viewed on a color monitor, a bright red subject will be reproduced in a slightly dull color.

Therefore, the R3G and B signals that have been subjected to necessary processing such as amplification in the signal processing circuits 36 to 38 are transferred to the masking circuit 3.
9, hue correction is performed in the state of the electrical signal. Generally, a linear matrix circuit is often used as this masking circuit.

FIG. 4 shows a block diagram of this masking circuit.

To briefly explain this operation, the subtraction circuits 41 to 43 calculate R-G3G-B from the input R, G, and B signals.

Each color difference signal of B-R is generated, the above signal is multiplied by an appropriate coefficient of 1 to 6 in coefficient multiplication circuits 44 to 49, and this is added to the R, G, and B signals in addition circuits 50 to 55. be.

In this way, the spectral sensitivity characteristics shown in FIG. 3(A) are changed isometrically as shown in FIG. 3(B), and nine-color reproducibility can be improved.

However, the two-wire method has the following drawbacks.

That is, for example, 1 is added to the R-G coefficient to be added to the R signal.
When changing , the two equivalent spectral sensitivity characteristics are:

It changes as shown in FIG. 3(B). In other words, when attempting to adjust the spectral sensitivity related to R, the 3G characteristics also work together, creating the problem that adjustment is difficult. Of course,
In principle, the linear matrix circuit described above is a circuit that can accurately correct color mixture in optical systems such as prisms and filters, but in reality, the two-hue adjustment circuit is a circuit that can accurately correct color mixture between multiple cameras rather than color mixture correction. It is often used as a tone adjustment, and the problem is that it is difficult to adjust.

In addition, when 9 circuits are configured with digital circuits.

In the conventional linear matrix method, six multipliers are required for multiplying coefficients by 1 to 6. In digital circuits, the number of multipliers has a large effect on the scale of the two circuits, which poses problems in terms of cost, size, and power.

[Problem to be solved by the invention]

An object of the present invention is to solve this drawback of the conventional circuit and provide a digital hue correction circuit that is easy to adjust and has a small circuit scale.

[Means to solve the problem]

In order to achieve the above object, the present invention converts C1-Cj (Ci) from digitized R3G and B signals.

CjER, G, B) subtraction means for obtaining a signal; means for selecting two different types of coefficients depending on the positive/negative polarity of these subtraction results; means for multiplying the selected coefficients by the above subtraction results; The present invention is characterized in that it has a configuration that includes means for adding or subtracting a corresponding Ci or Cj multiplied signal depending on the polarity of the subtraction result.

[Effect]

In the present invention, when the calculation result of C1-Cj calculated by the subtraction means is positive, this calculation result is added to a predetermined constant by 1.
Multiply by and subtract (add) Kl (Ci - Cj) from Cj times the signal
Also, when the calculation result of C1-Cj is negative, this calculation result is multiplied by 2 by another predetermined constant, and 2 (Ci-Cj) is added (subtracted) to the Ci multiplied signal. By using this method, it is possible to perform hue adjustment independently for each color signal of R2O and B, and it is also possible to reduce the number of multipliers used to three, which is half of the conventional method. .

[Embodiment] FIG. 1 shows a first embodiment of the present invention, and the present invention will be described in detail below. The R3G and B signals color-separated by the prism 32 or color filter in FIG. The signals are converted into digital signals by converters 4 to 6. The eight digital signals from the A-D converters 4 to 6 are sent to subtracters 7 to 9 to produce color difference signals R-G.
.

Converted to GB, B-H.

A feature of the present invention is the color difference signal R-G3G-B.

Depending on the polarity of each of B-R, the corresponding switch 19-2
1.25 to 27, and the hue adjustment of the three colors R, G, and B can be performed independently using half the number of multipliers 22 to 24 compared to the conventional one. Describing this process in detail below, subtracters 7-9 output color difference signals R-G3G-B and BR with sign bits 10-12, and are sent to 9 multipliers 22-24. Coefficients 1 to 6, which are multiplied by each color difference signal in each of the multipliers 22 to 24, are stored in coefficient registers 13 to 18. Among these, Kl,
5 is the hue adjustment coefficient of the R signal, and similarly 2. 3 is for G, 4 is for G. 6 is for B. In other words.

In the present invention, two coefficients are prepared in the coefficient register for one multiplier. When the outputs of the subtracters 7-9 are positive, the switches 19-21 change the coefficient Kl to 3. 5 is selected and each corresponding color difference signal is multiplied by 9 multipliers 22-24. and.

This multiplication result is sent to switches 25-27.

The switch is switched as shown by the solid line in FIG. 2 when the positive values of the subtractors 7 to 9 are positive. At this time, the outputs of the 2 multipliers 22 to 24 are added to the 3G, B, and R signals by an adder circuit 30°32.29. On the other hand, when the outputs of 7 to 9 are negative, the switches 25 to 27 are switched as shown by the dotted line, and the outputs of 7 multipliers 122 to 24 are transferred to the adders 28, 31.3.
3 is added to each signal of R2O and H.

As a result of the above operations, for example, if a red object is being imaged now, the R-G signal becomes positive and the B-R signal becomes negative, and the switches 19.25 and 21.
27 is switched as shown by the dotted line. In other words, KI for 3G signal
X (R-G) signal.

A 6X (BR) signal is added to the B signal.

Here, we set the coefficient to 1 as a negative value and 6 as a positive value, so that the red light
, if the value is adjusted to a value that can exactly cancel out the amount leaked into the B image pickup elements 34 and 35 (FIG. 2).

When this red object is imaged, the G and B signal outputs become zero, and a pure red image can be reproduced. On the other hand, when a green object is imaged, the RG signal becomes negative and the 3G-B signal becomes positive.

Therefore, switch 19.25 is placed on the dotted line side, switch 2
0.26 switches to the solid line side, and the R signal has 2X (R-
The G) signal is added to the B signal, and the 3.times.(G-B) signal is added to the B signal. Therefore.

2 for the coefficient. By adjusting 3 to an appropriate value, a pure green image can be reproduced. Similarly, the coefficient is 4. A pure blue image can be reproduced by adjusting the K5.

2. Although only three multipliers are used in the present invention, R
, G, and B color signals are as follows.

6 for R signal to Kl. Crab for G signal 2. 3. Crab for B signal 4. and 5 are independent, so it is possible to easily adjust the hue of each color individually.

〔Effect of the invention〕

As described above, the use of the present invention has the great advantage of being able to significantly reduce the circuit scale compared to the conventional method, and making it possible to independently adjust the hue of each color.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention. FIG. 2 is a schematic block diagram of a television camera. FIG. 3 is a spectral sensitivity characteristic diagram of a prism, and FIG. 4 is a block diagram showing a conventional masking circuit. 4-6: A-D converter, 7-9: Subtractor, 28-3
3: Adder, 22-24: Multiplier, 19-21.25-
27: Switch.

Claims (1)

[Claims] 1, R (red), 3G (green), B (blue), or their complementary colors, take the level difference between each two color signals, and apply this difference at a predetermined ratio to the corresponding three primary color signals,
In a color television camera that performs hue correction by addition or subtraction, means for selecting and multiplying the value of a coefficient to be multiplied by each difference signal according to the polarity of each difference signal between two color signals in the three primary color signals; , and means for adding each difference signal multiplied by the coefficient to the corresponding three primary color signals.