JPH03291086A - Image pickup device - Google Patents

Abstract

PURPOSE:To attain proper white balance adjustment even at pickup with unfavorable condition by synthesizing white balance adjustment control signals based on signals from an image pickup element and other colorimetric sensor in a synthesis ratio varied with a difference between both outputs. CONSTITUTION:An output of an image pickup element 1 is fed to the circuit via a chroma signal processing section 3 and averaging sections 11, 13 and a 1st white balance adjustment signal is obtained from a control voltage leadout section 14. Moreover, a 2nd white balance adjustment signal is outputted from a control voltage leadout section 11 receiving a colorimetric output by a color temperature sensor 10. Switches 15, 16 are controlled by a switch control signal leadout section 17 based on a difference between an output of the sensor 10 and an output equivalent to an output of the element 1 from a colorimetric sensor 18. Thus, the 1st and 2nd white balance adjustment control signals are synthesized in a ratio varied with an output difference of the sensors 10, 18 to obtain a proper white balance adjustment signal, and proper white balance adjustment is implemented even under bad conditions such as remote scene, dispersion in lighting state and rear light.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an imaging device, and particularly to an imaging device having a white balance adjustment means.

[Conventional technology]

Conventionally, as a white balance adjustment device for an imaging device, there is an external measurement method that adjusts the white balance using the output signal of an external colorimetric sensor as shown in Figure 7, and a white balance adjustment method that adjusts the white balance using the output signal of the image sensor as shown in Figure 8. A through-the-lens method (hereinafter referred to as TTL method) for performing balance adjustment is known.

The conventional example will be explained below using FIGS. 7 and 8.

FIG. 7 is a block diagram of a conventional example of the external measurement method, and numeral 1 indicates a solid-state image sensor which is an image sensor that converts optical information into an electrical signal. 2 is a brightness signal processing unit that performs appropriate processing on the output of the image sensor 1 and derives a brightness signal Y; 3 is a brightness signal processing unit that performs appropriate processing on the output of the image sensor 1 and generates a low-range brightness signal YL, a color signal R, A chroma signal processing unit (hereinafter referred to as chroma signal processing unit) that derives B. Reference numerals 4 and 5 denote an R gain control section and a B gain control section which respectively control the levels of the outputs R and B of the chroma signal processing section 3 and output R, , B. 6 is a differential amplifier that derives the color difference signal RY from YL and R3. 7 is a differential amplifier that derives the color difference signal B-Y from YL and B1. 8 is color difference signal R-Y
and a modulation unit that derives a modulation signal specified by NTSC, PAL, etc. from B-Y. Reference numeral 9 denotes an adder that derives a predetermined video signal from the output Y of the luminance signal processing section 2 and the output of the modulation section 8. 10 is a color temperature sensor which is a colorimetric sensor other than the image sensor that measures the color temperature of the light source illuminating the subject; 11 is an amplifier for the R gain control section 4 and the B gain control section 5 based on the output of the color temperature sensor 10; This is a control voltage derivation unit that derives a voltage for controlling the gain.

The operation will be explained below according to FIG.

A luminance signal processing section 2 derives a Y signal from the output of the first image sensor, and a chroma signal processing section 3 derives YL and R signals.

get B. Then, the color temperature of the light source illuminating the subject is measured by the 10 color temperature sensors, and the control voltage deriving unit 11 outputs the color temperature to the R gain control unit 4 and the B gain control unit 5 in order to correct the white balance. A control voltage is derived, and color signals R+ and B+ whose white balance has been adjusted by an R gain control section 4 and a B gain control section 5 are obtained. Below, differential amplifier 6.7. A modulator 8 and an adder 9 derive a predetermined video signal whose white balance has been adjusted from Y, YL, R, . . . Bl.

Next, FIG. 8 is a block diagram of a conventional example of the TTL system. Blocks 1 to 9 correspond to blocks with the same numbers in the conventional example of FIG. 7, and 12 and 13 are R- Y
This is an averaging unit such as a low-pass filter that averages the BY signal and converts it into a DC potential. Reference numeral 14 denotes a control voltage deriving section that derives control voltages to be applied to the R gain control section 4 and the B gain control section 5 in order to correct the white balance from the signal averaged by the averaging section 12.13.

The operation will be explained below.

The operations of blocks 1 to 9 are similar to the conventional example shown in FIG.

The R-Y and B-Y signals averaged over one screen or several screens in the averaging section 12.13 are then converted to a specific potential corresponding to the zero level of color difference No. 18 in the control voltage deriving section 14. compared.

Determine whether the level is lower or higher than the zero level, R-Y,
A control voltage is derived so that the B-Y level reaches the level closest to the zero level. Then, this control voltage is set to R-8
The signal is input to the gain control section 4.5 to perform white balance adjustment.

In addition to the above two methods, an example of an addition method that combines the external measurement method and the TTL method is known.

FIG. 9 is a block diagram showing an example of an addition method.

In the figure, blocks 1 to 14 correspond to blocks with the same numbers in the conventional example shown in FIGS. 7 and 8. Note that hereinafter 14 is the first control voltage deriving section, and 11 is the second control voltage deriving section.
This is called the control voltage derivation section.

Further, 27 and 28 are adders that add the control voltage obtained by the first control voltage deriving section 14 and the control voltage obtained from the second control voltage deriving section 11 at a constant ratio. Then, white balance adjustment is performed using this added voltage.

That is, in this conventional example, by adding both control voltages obtained from the signal obtained from the image sensor 1 and the signal from the color temperature sensor, which is the colorimetric sensor 10 other than the image sensor, at a constant ratio, It is configured to perform good white balance adjustment.

In addition, Japanese Patent Application Laid-Open No. 63-3144 filed by the applicant
Publication No. 24 detects the amount of light incident on a colorimetric sensor,
There is also a description that white balance is adjusted by selectively selecting two colorimetric methods based on the detection output.

[Problem to be solved by the invention]

However, in the above conventional example, in the external measurement method shown in Fig. 7,
When the imaging device main body and the subject are far apart and different light sources illuminate them, or at sunset, the accuracy of white balance adjustment is significantly reduced.

In addition, in the TTL method shown in Figure 8, when the subject is a large area of chromatic color, and most of the screen is occupied by a single color, the single color is corrected to white. As expected, it will lead to a decrease in the accuracy of white lance adjustment.

On the other hand, in the addition method shown in FIG. 9, in order to compensate for the shortcomings of the two conventional examples mentioned above, the control voltages derived by the external measurement method and the TTL method are simply added together, resulting in zero improvement in accuracy. However, by adding them in the opposite direction, the accuracy of white balance adjustment for each scene is reduced, which is a drawback. Furthermore, JP-A-63
The example shown in Japanese Patent No. 314424 is a remedy only when the surroundings are dark, and is not suitable for white balance adjustment in bright scenes that are difficult to use.

This invention solves the above-mentioned problems of the conventional technology, and allows for distant views, variations in illumination conditions, backlighting, and imaging under dark backgrounds, which the outside measurement method is not good at, and the imaging screen, which is not good at the TTL method, is a single color. To provide an imaging device that can perform appropriate white balance adjustment even in various types of imaging, and can obtain an appropriate effect, which is different from the adjustment that dilutes the characteristics of both of the above methods, which tends to occur with additive methods. The purpose is to

[Means to solve the problem]

Therefore, the imaging device according to the present invention includes a first white balance adjustment means that generates a control signal for white balance adjustment using a signal obtained from an image sensor, and a first white balance adjustment means that uses a signal obtained from a colorimetric sensor. and second white balance adjustment means that generates a control signal for white balance adjustment, the imaging device comprising a second white balance adjustment means that generates a control signal for white balance adjustment, the imaging device comprising: a signal obtained from the image sensor or an equivalent signal thereto, and a second white balance adjustment means that generates a control signal for white balance adjustment; This object is achieved by a configuration characterized in that it includes a combining means that changes the combining ratio of each of the control signals according to the difference between the control signals and the control signal.

Furthermore, a first white balance adjustment means generates a control signal for white balance adjustment using the signal obtained from the image sensor, and a colorimetric sensor having a surface angle different from the imaging angle of view of the imaging optical system. a second white balance adjustment means that generates a control signal for white balance adjustment using the signal; and a comparison between an output from a photometry means different from the colorimetry sensor and an output from the colorimetry sensor. The above object is achieved by a configuration characterized in that it includes a combining means for outputting the two control signals in a variable manner.

(Operation) With the above configuration, control No. 13 for white balance adjustment obtained by the first white balance adjustment means and control No. 13 for white balance adjustment obtained by the second white balance adjustment means The signal is controlled by a synthesizing means to adjust the white balance by varying the synthesis ratio according to the difference between the signal obtained from the image sensor or an equivalent signal and the signal obtained from the colorimetric sensor. A signal is output, and an appropriate white balance adjustment is performed using this control signal to capture an image.

Here, the large difference between the above control signals means that
Since the imaging conditions of the image sensor, for example, the brightness of the subject and the imaging conditions of the colorimetric sensor, are significantly different, it is possible to generate control signals for white balance adjustment using such comparison results. ,
Realizes more accurate white balance control.

〔Example〕

(First Embodiment) FIG. 1 is a block diagram showing a first embodiment of an imaging apparatus according to the present invention.

Blocks 1 to 14 correspond to blocks with the same numbers shown in the conventional example.

Further, imaging light is incident on the imaging device 1 via an imaging optical system 1a, and an imaging angle of view is appropriately set in this imaging optical system 1a. 15.16 is a switch, 17 is a switch 15.
A switch control signal deriving section 18 is a photometric sensor that measures the brightness of a subject, and is provided separately from the imaging optical system 1a and the color temperature sensor 10, which is a colorimetric sensor.

In addition, a white diffuser plate 10 is provided in front of the color temperature sensor 10.
Optical means such as a are arranged, so that the angle of view of this sensor 10 is set wider than the angle of view of the imaging optical system 1a. Then, the photometric sensor 18 has
Since the imaging light incident through the imaging optical system 1a is extracted by, for example, a half mirror, etc., the angle of view of this sensor 18 is approximately the same photometric angle of view as the imaging angle of view of the imaging optical system 1a. This is to enable more accurate output of brightness information in the imaging range of the subject. Note that the photometric angle of view of this sensor 18 may be narrower than the imaging angle of view.

FIG. 2 is a diagram illustrating the switch control signal deriving section 17, in which 19 is a comparator (hereinafter referred to as a comparator), and 20 is an adder.

The image sensor 1, the averaging sections 12 and 13, and the control voltage deriving section 14 constitute a first white balance adjustment means, and the color temperature sensor 10, which is a colorimetric sensor other than the image sensor, and the control voltage deriving section 11 constitutes a second white balance adjustment means. Further, the switch control signal deriving section 17 and the switches 15 and 16 constitute a combining means.

In this example, the synthesis ratio of the control signals from each adjustment means by the synthesis means of the present invention is set to O and 100%.
It is variable.

Next, the operation will be explained.

In FIG. 1, operations 1 to 14 are the same as in the conventional example. The switch control number 13 deriving unit 17 includes a photometric sensor 1
8 and a signal Yc representing luminance information among the outputs of the color temperature sensor 1° are input. Here, Yc is an output corresponding to the green component of the light source light, or a value obtained by mixing a red component, a blue component, and a green component in an appropriate ratio.

As mentioned above, the color temperature sensor 10 and the photometric sensor 18
This depends on the angle of view, so if the output of the color temperature sensor 10 and the output of the photometry sensor 18 are significantly different, the light irradiating the subject and the light irradiating the imaging device may be different light sources. Therefore, in this case, switches 15 and 16 are connected to the TTL side, which is the first medium-wide balance adjustment means, and white balance control is performed based on the imaging light from the subject. The output of the switch control signal deriving unit 17 is set so that the switches 15 and 16 are connected to the external measurement method side, which is the second white balance adjustment means, if the value is within a certain level.

The operation of the switch control signal deriving section 17 will be explained with reference to FIG. The photometric sensor output Y is input to the non-inverting input terminal of the comparator 19, and Yc+E, which is the color temperature sensor output Yc plus a specific value E, is input to the inverting input terminal. As a result, Y>Y, +E, so to speak, the output of the switch control signal deriving section 17 becomes high level, and Y<Y. At +E, the output becomes low level.

When the output of the switch control signal deriving section 17 is at a high level, the switches 15 and 16 select the TTL method which is the first white balance adjustment means, that is, the output of the control voltage deriving section 14 as the control voltage, and derive the switch control signal. Part 17
If the output is at a low level, the external measurement method as the second white balance adjustment means, that is, the output of the control voltage deriving section 11 is selected to perform white balance adjustment.

Furthermore, another example of the switch control signal deriving section 17 will be explained with reference to FIG. 21 is the same comparator as 19 in the previous example, 22 is the same adder as 20 in the previous example, 23 is a NAND gate, and 24 is an inverter.

In this case, if Y c E < Y < Y c + E,
The output of the inverter 24 becomes a low level and selects the second white balance adjustment means, and if Yc-E>Y or Yc+E<Y, it becomes a high level and selects the first white balance adjustment means.

In the above example, yc-IE:=y or YC+E4
In the case of Y, since the frequency of system changes increases, the comparators 19 and 21 may have bisteresis characteristics.

With the above configuration and operation, when the subject and the imaging device are under the influence of different light sources, such as in the case of long distance or backlight, or when the brightness of the subject and its surroundings are different, the photometry sensor When the output is large, the IIJ control signal from the first white balance adjustment means is selected, and when the subject and the imaging device are illuminated by the same light source, and when the brightness of the subject and the surroundings are the same. etc., the white balance adjustment is performed by selecting the control signal from the second white balance adjustment means, so that appropriate white balance adjustment can be performed even under various lighting conditions.

Note that the incident angle of the photometric sensor 18 is determined by imaging optics, %1a
By making the incident angle substantially the same as or narrower than the incident angle, it is possible to provide an imaging device having a more appropriate white balance adjustment effect.

Also, 1st. By providing a bisteresis effect to the switching point of the second white balance adjustment means, a stable white balance adjustment control signal can be output even near the switching point, and stable imaging can be achieved.

(Second Embodiment) FIG. 4 is a block diagram of a second embodiment of the imaging device according to the present invention, and ]a, 1 to 10, 12, 13.18 are the first
There is a blower corresponding to the same reference numeral block in FIG. 1 of the embodiment. 25, 26, and 27 are A/D converters, 28 is a D/A converter, and 29 is a microcomputer (hereinafter referred to as microcomputer).

The image sensor 1, the averaging sections 12 and 13, and the A/D converter 26 constitute a first white balance adjustment means, and the color temperature sensor 10 and A/D which are colorimetric sensors other than the image sensor The converter 25 constitutes second white balance adjustment means, and the microcomputer 29 constitutes composition means.

FIG. 5 is a flowchart illustrating the operation of the microcomputer 29 shown in FIG. The operation of this second embodiment will be explained below with reference to FIGS. 4 and 5.

First, a threshold value (threshold level) for level determination is set as E=E (step (a)). Next, the output Yc of the color temperature sensor ] 0 and the output Y of the photometric sensor 18 are A/D converted by the A/D converter 25.27 and input manually to the microcomputer 29 (step (b)), then step Y<Yc+E at (c), Y> at step (d)
Check Yc-E, and if both are Y and es, step (
Proceeding to step (e), the output CC of the color temperature sensor 10 is A/D converted and manually input, and in step (e), a white balance control signal voltage is derived from CC and output to the D/A converter 28. Furthermore, in (g), E=E2. However, E2
>E.

If Y, 1=Yc+E or Y≦YC-E in steps (c) and (d), the process proceeds to step (h), where the output of the averaging section 12.13 is A/D converted and the microcomputer 29 is manually operated. Then, a white balance control signal 3 voltage is derived and output to the D/A converter 28. Furthermore, in (nu), set E=E.

However, E3<E. The signal input to the D/A converter 28 becomes an analog signal and is sent to the R and B gain control section 4.5 where appropriate white balance adjustment is performed.

As described above, if there is a large difference between the output Y of the photometric sensor 18 and the luminance information output Yc of the color temperature sensor 10, the first
If Y and yc are similar values, the second white balance adjustment means is selected to perform white balance adjustment, and E2
By setting >El >E3, it is possible to provide bisteresis so that even if IY-YCI fluctuates around El or E2°E3, it does not affect the selection of the white balance method. Stable white balance adjustment can be performed even near the switching point of the second white balance adjustment means.

(Third Embodiment) In the above embodiment, the predetermined processing is performed directly on the output of the image sensor 1, but the output of the image sensor 1 may be temporarily stored in the image memory and then performed on the output. , FIG. 6 shows an embodiment of the same, and numeral 30 is a frame memory. In this case, processing for each screen is easy, and an improvement in white balance adjustment accuracy can be expected.

(Fourth Embodiment) In the above embodiments, R-Y and B-Y signals were used as color signals used in the first white balance adjustment means, but R, G, B signals, etc. may also be used as color signals. good. In this case, it is possible to further improve the effect of white balance adjustment.

(Fifth Example) In addition, in the above example, the control signal was obtained by averaging the color signals on the entire screen of the TTL method as the signal used in the first white balance adjustment means, but only the color signal of the high brightness portion was used. Other methods may also be used, such as determining the control signal using .

(Sixth Embodiment) In the above embodiments, the selection of the first or second white balance adjustment means was switched to select the control signal voltage of either the TTL method or the external measurement method. In the vicinity of the threshold, the control voltage may be gradually switched using a value that takes both control voltages into consideration, such as an average value of the control signal voltages of both types or an approximate value thereof. In this case, more stable and preferable imaging can be performed even near the threshold value.

Note that the control signal voltages are not limited to the vicinity of the threshold value, but may be combined at a predetermined ratio over the entire range of control signal voltages.

(Seventh Embodiment) In the above embodiments, a photometric sensor separate from the imaging optical system was used, but an image sensor may also be used as the photometric sensor.

In each of the above-mentioned embodiments, the synthesis ratio by the synthesis means of the present invention was varied between 0 and ioo% to selectively output each control signal, but this synthesis ratio may be changed continuously or It may be made to vary stepwise.

Furthermore, in each of the above embodiments, the colorimetric field angle of the colorimetric sensor was wider, but the opposite may be true.

Further, in the above-described embodiment, the photometric sensor 18 is provided independent of the image sensor engineer, but it goes without saying that the luminance signal obtained from the image sensor 1 may be used as the output of the photometric sensor 18.

(Effects of the Invention) As described above, according to the present invention, the first white balance adjustment means generates a control signal for white balance adjustment using a signal obtained from an image sensor, and a second
The white balance adjustment means generates a control signal for white balance adjustment using the signal obtained from the colorimetric sensor, and the signal obtained from the image sensor or a signal equivalent thereto and the colorimetric sensor are synthesized by the synthesis means. A control signal for white balance adjustment is output by varying the synthesis ratio of each control signal according to the difference with the signal obtained from the sensor, and this control signal is used to perform appropriate white balance adjustment and image capturing. It is also capable of capturing images of a single color or a subject with a strong influence of a single color, which the external method was weak at, as well as distant views, variations in lighting conditions, backlighting, outdoor imaging from indoors, and imaging against a dark background, which the external measurement method was weak at. Appropriate white balance adjustment can be made. Furthermore, it is possible to provide an imaging device that can obtain an appropriate white balance effect, which is different from the half-hearted adjustment that dilutes the characteristics of both of the above methods, which tends to occur with simple addition methods.

Further, according to the present invention, desired detection can be performed accurately regardless of the color, brightness, or distance of the subject, and thereby more accurate white balance control can be realized.

Note that by making the incident angle of the photometric sensor substantially the same as or narrower than the incident angle of the imaging optical system, an imaging device having a more appropriate white balance adjustment effect can be provided.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the first embodiment, FIGS. 2 and 3 are explanatory diagrams of the switch control signal deriving section of FIG. 1, FIG. 4 is a block diagram showing the second embodiment, and FIG. 6 is a flowchart explaining the second embodiment, FIG. 6 is a block diagram showing the third embodiment, and FIG. 7.8.9 is a block diagram showing the conventional example. 1 is an image sensor, 2 is a luminance signal processing section, 3 is a chroma signal processing section, 4.5 is an R, B gain control section, 6°7 is a differential amplifier, 8 is a modulation section, 9 is an adder, 10 is a 11. A color temperature sensor which is a colorimetric sensor; 14 is a control voltage derivation unit; 12.
13 is an averaging unit, 15.16 is a switch, 17 is a switch control signal derivation unit, 18 is a photometric sensor, 19.21 is a comparator, 20.22 is an adder, 23 is a NAND gate,
24 is an inverter, 25, 26, 27# A/D converter,
28 is a D/A converter, 29 is a microcomputer, and 30 is a frame memory.

Claims (5)

[Claims] (1) A first white balance adjustment means that generates a control signal for white balance adjustment using the signal obtained from the image sensor, and a control signal for white balance adjustment using the signal obtained from the colorimetric sensor. An imaging device comprising a second white balance adjustment means that generates a white balance,
Imaging characterized by comprising a combining means for varying a combining ratio of each of the control signals according to a difference between a signal obtained from the image sensor or a signal equivalent thereto and a signal obtained from the colorimetric sensor. Device. (2) A first white balance adjustment means that generates a control signal for white balance adjustment using a signal obtained from an image sensor, and a colorimetric sensor that has a different angle of view from the imaging optical system. a second white balance adjustment means that generates a control signal for white balance adjustment using a signal obtained by comparing the output from a photometry means different from the colorimetry sensor with the output from the colorimetry sensor; 2. The imaging apparatus according to claim 1, further comprising: combining means for varying and outputting the two control signals. (3) The imaging device according to claim 2, wherein the photometry means has a photometry angle of view that is substantially the same as the imaging angle of view of the imaging optical system. (4) The imaging device according to claim 2, wherein the photometry means has a photometry field angle narrower than the imaging field angle of the imaging optical system. (5) The imaging device according to claim 2, wherein the photometry means uses an imaging device.