JPH089392A - Color balance setting device for frame sequential color camera - Google Patents

Abstract

(57) [Abstract] [Purpose] To realize a color balance setting device capable of stable and high-speed operation by preventing variations in noise level of an image pickup signal for each color. A color balance setting device for a frame-sequential color camera that color-separates and captures image light of a subject, and includes a stroboscopic light emitting means (21) for illuminating the subject with illumination light.
The amount of light emitted by the strobe light emitting means (21) at the time of picking up each color so that the magnitude of the image pickup signal of each color obtained by picking up the image light of the subject illuminated by the strobe light emitting means (21) becomes a predetermined ratio. Control means for adjusting (1
7, 23). The strobe light emitting means (21)
The emission amount of can be adjusted by changing the emission intensity, emission time, or FP emission frequency.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color balance setting device for a frame-sequential color camera, and more particularly to setting a color balance quickly and accurately by adjusting the light emission amount of a stroboscopic light emitting device at the time of capturing each color. It's about the technology that makes it possible.

[0002]

2. Description of the Related Art FIG. 8 shows a schematic structure of a color balance setting device in a conventional color camera. The device in the figure is
After the image light of the subject is converted into an image signal of a frame-sequential system by an image pickup device 3 such as a CCD device through an image pickup lens and a color separation filter 1 which are not shown, a signal processing circuit 7 performs a predetermined image processing and a variable gain. Output to the outside through the amplifier 9. Then, the signal processing circuit 7 equalizes the video signal outputs corresponding to the three primary colors R, G, B input from the image pickup device 3. That is, the detection level V _DET of the video signal of each color and the reference signal V _REF are sequentially input to the comparator 11 for white balance, and the two are compared. Then, the comparison result is fed back to the signal processing circuit 7 and the control voltage V _CNT of the variable gain amplifier 9 is adjusted so that the level of the video signal of that color becomes a predetermined value. The white balance is set by performing such processing for each color and controlling the video signal outputs of all colors to be equal.

In the white balance setting process, when the level of the video signal of each color is set to match the reference value, for example, a green (G) video signal level is used as the reference value. However, there is also an apparatus that sets the video signal levels of the other colors R and B to be equal to the G signal level.

For example, as shown in FIG. 9, the comparator 11 first obtains the difference between the R and G signal levels in step 901. If the R signal level is smaller than the G signal, the R signal is detected in step 902. The gain is increased and the process returns to step 901 again. Also, for the G signal, R
When the signal level of R is high, the gain of the R signal is reduced in step 903, and then the process returns to step 901.
Such an operation is repeated, and at step 901 R
If the signal levels of G and G become the same, the gain of R is stored in step 904, and the process proceeds to step 905.

In step 905, the signal levels of blue (B) and G are compared, and if the level of B is smaller than G as before, the gain of B is increased, and the signal level of B is the signal of G. If it is larger than the level, the gain of B is lowered and then the process returns to step 905. If the B and G signal levels become equal, the gain of B is stored in step 908, and then the process ends. by this,
The gain for each color of the variable gain amplifier 9 is set to the gain that is sequentially stored in a time division manner, and thereafter, it is possible to capture an image with a white balance set.

[0006]

However, in the conventional apparatus as described above, the variable gain amplifier is used to adjust the gain of each color when the white balance is set. However, this variable gain amplifier has a disadvantage that the setting state of the white balance cannot be stably maintained because the gain fluctuates due to, for example, a change in power supply voltage, a temperature change, and the like, and there is a variation in gain among products. Further, since the linearity of the gain with respect to the control voltage cannot be sufficiently obtained, the white balance setting accuracy may decrease. Further, when the ratio of the image light of the subject incident on the camera to each color is large, a color having a considerably large gain and a small color are generated in the variable gain amplifier, which causes noise to occur for each output of each color R, G, B. There was a problem that the difference between the presence and the absence of the item was quite noticeable.

Further, in the conventional white balance setting device, when setting the white balance, it takes time until the gain corresponding to each color is set to a predetermined value, and the change state of the gain of each color also affects the output video signal. To appear,
There is also an inconvenience that when the white balance is set, the state in which the magnitude of the output video signal changes is displayed on the screen and the screen becomes unsightly.

In view of the above-mentioned problems in the conventional white balance setting device, an object of the present invention is to stably maintain the color balance setting state and reduce the difference in the presence or absence of noise in the video signal for each color. In order to obtain stable and high quality images.

Another object of the present invention is to allow a color balance setting device for a frame sequential color camera to quickly set a color balance and to display a change in an output video signal on the screen when the color balance is set. To prevent that.

Still another object of the present invention is to enable a color balance setting device for a frame sequential color camera to set an appropriate color balance over a wide range of subject brightness.

[0011]

In order to achieve the above object, according to the present invention, there is provided a color balance setting device for a frame sequential color camera for color-separating and capturing image light of an object. The strobe light emitting means 21 for irradiating the subject with illumination light, and the image pickup signal for each color obtained by picking up the image light of the subject illuminated by the strobe light emitting means have a predetermined ratio. In this case, the control means (17, 23) for adjusting the light emission amount of the strobe light emitting means is provided.

The control means can adjust the light emission amount by changing the light emission intensity of the strobe light emitting means (see FIG. 2A) or by changing the light emission time (see FIG. 2B). it can.

Further, when the strobe light emitting means is capable of emitting FP light, the control means changes the FP light emission frequency of the strobe light emitting means (FIG. 2 (c)).
See) The amount of light emission can be adjusted.

Further, an optical sensor (19) for detecting the image light from the subject illuminated by the strobe light emitting means.
It is convenient that the control means adjusts the light emission amount of the strobe light emitting means based on the integrated value of the output signal of the optical sensor.

It is also convenient for the photosensor to detect the subject light after color separation by the color separation filter.

Further, in addition to the above-mentioned configurations, a variable gain amplifier (25) for adjusting the magnitude of the image pickup signal of each color.
Can be provided.

[0017]

In the color balance setting device having the above structure, when the image light of the object is picked up by the frame sequential method through the rotating disk type color separation filter, the three primary colors are not picked up at the same time. Focusing on the fact that
Unlike the conventional color camera, the color balance is not set by the variable gain amplifier, but the light emission amount by the strobe light emitting device is set to be different for each of R, G, and B colors to set the color balance.

That is, the image light of the subject illuminated by the strobe light emitting means is imaged for each color to obtain an image pickup signal for each color. Then, the light emission amount of the strobe light emitting means at the time of image pickup of each color is adjusted so that the magnitudes of the image pickup signals are equal or have a predetermined ratio. As a result, the color balance can be set such that the image pickup signals based on the image lights of the respective colors of the subject are equalized or have a predetermined ratio. As a result, the size of the image pickup signal of each color can be made equal or a predetermined ratio can be obtained without using a variable gain amplifier as in the prior art. Can be removed. Also, it is possible to quickly set the color balance.

Adjustment of the light emission amount of the strobe light emitting means is as follows.
The light emission intensity of the strobe light emitting means may be changed as shown in FIG. 2 (a), or the light emission time may be changed as shown in FIG. 2 (b). Further, when the strobe light emitting means is capable of FP light emission such that a small light emission is continuously performed, the control means changes the FP light emission frequency of the strobe light emitting means as shown in FIG. 2C. The amount of light emission can be adjusted.

In such a case, an optical sensor for detecting the image light from the object illuminated by the strobe light emitting means is provided, and the control means is based on the integrated value of the output signal of the optical sensor, and the light emission amount of the strobe light emitting means. The color balance can be set by adjusting. In addition,
Instead of this optical sensor, the light emission amount of the strobe light emitting means may be adjusted based on the image pickup signal obtained from the image pickup device of the camera.

Further, the light sensor is configured to detect the subject light after color separation by the color separation filter, so that the light emission amount for each color can be accurately detected and the precise color balance can be set. It will be possible.

Furthermore, the color balance setting device as described above is further combined with a variable gain amplifier for adjusting the size of the video signal of each color as in the conventional case, so that the image pickup can be performed without using the stroboscopic light emitting means. It is possible to set the color balance when performing the setting, and it is possible to accurately set the color balance even in an illumination state that cannot be corrected only by the stroboscopic light emitting means, thereby increasing the degree of freedom of the color balance setting. It will be possible.

[0023]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic structure of a frame sequential color camera including a color balance setting device according to an embodiment of the present invention. The color camera of FIG. 1 includes a rotary color filter 13 for color separation that receives image light of a subject (not shown) via an image pickup lens (not shown), and the rotary color filter 13
The image pickup device 15 is composed of, for example, a CCD device for receiving the image light having passed therethrough and converting it into an electric signal. The output of the image sensor 15 is connected to a signal processing circuit 17 for performing gamma correction and various image processing.

Further, an optical sensor 19 for receiving the image light of the subject that has passed through the rotary color filter 13 is provided, and the optical sensor 19 can be composed of, for example, a CdS cell, an SPD element or the like. Further, a strobe light emitting device 21 is provided which irradiates a subject (not shown) with illumination light based on a control signal from the signal processing circuit 17. Also,
Used for color balance setting, the set voltage V _SET from the signal processing circuit 17 and the detection voltage V from the optical sensor 19
A comparator 23 for comparing _SNS is provided,
The output of the comparator 23 is input to the signal processing circuit 17.

In the frame-sequential color camera shown in FIG. 1, image light from a subject illuminated by the stroboscopic light emitting device 21 is incident on the image pickup device 15 through the image pickup lens (not shown) and the rotary color filter 13. The rotary color filter 13 has color regions that respectively transmit light of the three primary colors of red (R), green (G), and blue (B), and is rotationally driven at a predetermined speed and sequentially transmitted to the image sensor 15. The color-separated image lights of the three primary colors are made incident. Image sensor 15
Converts the image lights of the respective colors R, G, B into corresponding image signals and sends them to the signal processing circuit 17. The signal processing circuit 17 performs a color balance setting operation, which will be described later, and various kinds of image processing, and outputs an image signal corresponding to the subject image from an output terminal (not shown).

In such a frame sequential color camera,
When color balance setting is performed, for example, white paper is imaged as a subject or a light source that emits white light is imaged, and a color balance setting switch (not shown) is operated to set color balance in the signal processing circuit 17. Give instructions. In response to this, the signal processing circuit 17 causes the image sensor 15
Among the image signals of the respective colors obtained from the above, for example, the image light of G is used as a reference and compared with the size of the image light of other colors, and the light emission amount of the strobe light emitting device 21 is set so that the two coincide. In this case, the light intensity of the strobe light emitting device 21 corresponding to the color to be set is detected by the optical sensor 19, and the voltage obtained by integrating the voltage corresponding to the light intensity is detected voltage V.
_It is applied to one input of the comparator 23 as _SNS . Further, the set voltage V _SET indicating the level to be set by the signal processing circuit 17 is input to the other input of the comparator 23. The comparator 23 compares the two input voltages and returns the comparison result to the signal processing circuit 17. Therefore,
The comparator 23 calculates the integrated value of the image light of the subject and the set voltage V
_{When SET} is compared with each other, and when both match, a signal indicating the match between the two is input to the signal processing circuit 17. The signal processing circuit 17 receives the strobe light emitting device 2 in response to the input of the coincidence signal.
The light emission of 1 is stopped.

Therefore, the signal processing circuit 17 starts the light emission of the strobe light emitting device 21 at the same time as the start of the image pickup of the image light of each color or before the start of the image pickup. Then, as described above, the strobe light emitting device 21 is caused to emit light until the comparator 23 outputs the coincidence signal. In this way, the light emission amount of each color is adjusted, and the light emission amount of the strobe light emitting device 21 is adjusted so that the obtained image pickup signal levels of the respective colors are equal. This makes it possible to set the color balance of the image pickup signal.

The color balance setting usually means a white balance setting in which the levels of the image signals of the respective colors are made equal, but the levels of the imaging signals of the respective colors are not the same value but, for example, a predetermined ratio. It also includes adjusting to. For example, depending on the type of subject, a clearer image may be captured by changing the ratio of the imaging signals of each color. For example, in the case of a subject with a strong redness, it is possible to obtain a clearer image by reducing the redness. Furthermore, the level of the image signal of each color can be intentionally changed to obtain a special effect.

In the above-mentioned device, as a method of controlling the light emission amount of the strobe light emitting device, a method of controlling the light emission intensity of the strobe according to the light emission form of the strobe light emitting device,
How to control the flash firing time and strobe
If it can emit light, FP emission time, that is, FP
There is a method of controlling the number of times of light emission.

That is, as a method of controlling the light emission intensity of the strobe, the light emission intensity may be changed for each color R, G, B as shown in FIG. Further, (b) shows a method for controlling the strobe light emission time for each color R, G, B, and (c) shows a method for controlling the number of light emission in FP light emission for each color.

FIG. 3 shows a detailed control procedure for controlling the light emission intensity of the strobe. In the figure, first, in step 301, the magnitudes of the R and G signals are compared by the comparator 23, and if the intensity of R is smaller than the intensity of G, in step 302, the intensity of R is lowered and then step 3
Return to 01. If the intensity of R is higher than the intensity of G, the emission intensity corresponding to R is reduced in step 303, and then the process returns to step 301. In step 301, information indicating the signal intensities of R and G, that is, the emission intensity corresponding to R when the amounts of incident light become equal, is obtained in step 3
After storing in 04, the process proceeds to step 305. That is, the emission intensity of the strobe is adjusted until the R and G incident light amounts become equal.

Next, in step 305, similar processing is performed for B and G. That is, if the incident light amount of B is smaller than the incident light amount of G, the emission intensity of the strobe light corresponding to B is increased in step 306, and if the incident light amount of B is larger than the incident light amount of G, step 30 is performed.
In step 7, the emission intensity of the strobe light corresponding to B is lowered, and then the process returns to step 305. In this way, step 305
If it is determined in B that the incident light amounts of B and G are equal, in step 308, the information indicating the emission intensity of B is stored, and then the process ends.

FIG. 4 shows a processing procedure for setting the color balance by controlling the flash emission time. In FIG. 4, first, in step 401, R and G
Of the incident light intensity of the
In Step 2, if the R light emission time of the strobe is extended and the R incident light amount is larger than the G incident light amount, step 40
In step 3, the process of shortening the R light emission time of the strobe is performed, and then the process returns to step 401. If it is determined in step 401 that the R and G incident light amounts are equal, in step 404, information indicating the R light emission time of the strobe is stored, and then the process proceeds to step 405. Next, in steps 405 to 408, similar processing is performed on B and G, and then the processing is ended.

FIG. 5 shows a procedure for setting the color balance by controlling the number of FP emission times or the FP emission time in a strobe capable of FP emission. Figure 5
In step 501, the incident light amounts of R and G are compared by the comparator 23. If the incident light amount of R is smaller than the incident light amount of G, in step 502, the R of the strobe light is emitted.
If the incident light amount of R is larger than the incident light amount of G, the number of FP light emission of R is decreased in step 503, and then the process returns to step 501. When the amounts of incident light of R and G become equal in step 501, the process proceeds to step 504, and the data indicating the number of times of FP light emission of R is stored, and then the process proceeds to step 505. In steps 505 to 508, the number of times of FP emission is adjusted for B and G as in the case of R. Note that F corresponding to R and B stored in steps 504 and 508
The P light emission frequency is used together with data indicating the preset G FP light emission frequency to set the strobe FP light emission frequency in the subsequent operation of the color camera.

FIG. 6 shows a schematic structure of a frame sequential color camera equipped with a color balance setting device according to another embodiment of the present invention. The color camera of FIG. 6 is obtained by adding a variable gain amplifier 25 to the color camera of FIG. The other parts are the same as those of the color camera of FIG. 1 and are given the same reference numerals. In addition to the signal processing circuit 17 of FIG. 1, the signal processing circuit 27 also performs processing for controlling the gain of the variable gain amplifier 25.

In the color camera shown in FIG. 6, the color balance can be set by using the stroboscopic light emitting device 21 similarly to the color camera shown in FIG. 1, but the variable gain amplifier 25 is used to set the color balance. The color balance can be set in the same manner as in the color camera shown in FIG. That is, for example, in the case where the color balance cannot be sufficiently corrected only by the illumination light of the strobe 21, in addition to the adjustment of the light emission amount of the strobe 21, or in place of the color balance setting by the adjustment of the light emission amount of the strobe 21, the variable gain amplifier 25 is used. Color balance settings can be made. Also, strobe 2
It is also possible to deal with the case where imaging is performed without using 1. Therefore, it is possible to easily deal with the case where the illumination condition of the subject fluctuates over a wide range, and it is possible to deal with the image pickup without using the strobe, and it is possible to greatly increase the degree of freedom of the image pickup by the color camera.

When setting the color balance as described above,
You can freeze the output screen to make it easier to see. That is, as shown in FIG. 7, when the color balance is set, first, at step 701, the current image pickup signal is stored in the frame memory attached to the frame sequential color camera. This frame memory is provided, for example, in the signal processing circuits 17 and 27 of each of the color cameras, and the one used for temporarily storing the image signal of each color and converting it into a simultaneous signal can be used. Next, in step 702, the color balance setting such as white balance (WB) is performed as described above, and then in step 703, the newly captured image signal is output after the color balance setting, thereby releasing the freezing of the output screen. To do. By this processing, the change state of the output image signal at the time of color balance setting is not displayed on the screen, and if it is used in the color balance setting device according to the present invention which is capable of color balance setting at a high speed, the screen at the time of color balance setting is displayed. Not only is it unsightly, the freezing time of the output screen can be shortened, and unnaturalness due to the output screen freezing can be minimized.

[0038]

As described above, according to the present invention, the fluctuation of the noise level for each color is eliminated as compared with the conventional white balance setting device using the variable gain amplifier.
Further, as compared with the case where a uniform light emission amount is given for each color, it is sufficient to emit light with only the required light emission intensity for each color,
Useless emission energy is not used, and heat generation of the strobe light emitting device can be suppressed. Also, the energy storage capacitor used in the strobe device can be made smaller than the conventional one.

Further, according to the present invention, since the color balance can be set without necessarily using the variable gain amplifier, the disadvantages of the variable gain amplifier, such as the gain characteristic due to the fluctuation of the power supply voltage and the temperature change, can be obtained. It is possible to suppress adverse effects due to fluctuations and variations among products.

Further, by additionally using such a variable gain amplifier, it is possible to cope with a wide range of variation of the illumination condition of the object, and the range of application of the color camera is expanded.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of a frame sequential color camera equipped with a color balance setting device according to an embodiment of the present invention.

FIG. 2 is a waveform diagram for explaining a strobe control mode in the color camera of FIG.

FIG. 3 is a flowchart showing a procedure for setting color balance by adjusting the light emission intensity of a strobe.

FIG. 4 is a flowchart showing a procedure for setting color balance by changing the flash emission time.

FIG. 5 is a flowchart showing a procedure for setting color balance by changing the number of FP flashes of a strobe.

FIG. 6 is a block diagram showing a schematic configuration of a frame sequential color camera provided with a color balance setting device according to another embodiment of the present invention.

FIG. 7 is a flowchart showing a procedure for freezing an output screen when setting color balance.

FIG. 8 is a block diagram showing a schematic configuration of a conventional white balance setting device.

9 is a flowchart for explaining the operation of the color balance setting device in FIG.

[Explanation of symbols]

 13 Rotation Color Filter 15 Image Sensor 17, 27 Signal Processing Circuit 19 Optical Sensor 21 Strobe Light Emitting Device 23 Comparator 25 Variable Gain Amplifier

Claims (7)

[Claims] 1. A color balance setting device for a frame-sequential color camera that color-separates and captures image light of a subject, and strobe light emitting means for illuminating the subject with illumination light, and the strobe light emitting means illuminates the subject. And a control means for adjusting the light emission amount of the strobe light emitting means at the time of image pickup of each color so that the magnitude of the image pickup signal of each color obtained by picking up the image light of the subject becomes a predetermined ratio. A color balance setting device for a frame sequential color camera. 2. The color balance setting device for a frame sequential color camera according to claim 1, wherein the control unit adjusts the light emission amount by changing the light emission intensity of the strobe light emitting unit. 3. The color balance setting device for a frame sequential color camera according to claim 1, wherein the control unit adjusts the light emission amount by changing the light emission time of the strobe light emission unit. 4. The strobe light emitting means is capable of emitting FP light, and the control means is FP of the strobe light emitting means.
2. The color balance setting device for a frame sequential color camera according to claim 1, wherein the amount of light emission is adjusted by changing the number of times of light emission. 5. A light sensor for detecting image light from a subject illuminated by the strobe light emitting means is provided, and the control means is based on an integrated value of an output signal of the light sensor, and a light emission amount of the strobe light emitting means. 5. The color balance setting device for a frame sequential color camera according to claim 1, wherein 6. The color balance setting device for a frame-sequential color camera according to claim 5, wherein the optical sensor detects subject light after color separation by a color separation filter. 7. The color balance of the frame sequential color camera according to claim 1, further comprising a variable gain amplifier for adjusting the magnitude of the image pickup signal of each color. Setting device.