JPH074013B2 - Camera with auto white balance device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a camera having an auto white balance device, more specifically, a color video camera, an electronic camera or the like having an auto white balance device for automatically performing color temperature correction. Regarding

[Prior Art] In a color video camera, electronic camera, or the like, white balance adjustment is necessary to obtain a good color image, and if the color temperature of the light source changes, the white balance also changes. Regarding color temperature correction of video cameras, etc., conventionally, in addition to image pickup tubes and image pickup elements, a color temperature detection sensor that measures the color temperature of the light source of the subject (from multiple elements with different spectral characteristics to detect color balance) Has been proposed, and an automatic white balance device has been proposed in which the white balance is automatically adjusted by calculating the output of this sensor.

[Problems to be Solved by the Invention] In a camera having such an automatic white balance device, the photographer may inadvertently cover the light-receiving surface of the color temperature detection sensor with his / her hand or clothes during photographing. Often. In such a case, the color temperature detection sensor cannot detect the color temperature information of the light source light, and the normal operation of the automatic white balance cannot be performed.

The present invention has been made in view of such problems, and an object of the present invention is to make it possible to detect that the light receiving surface of the color temperature detection sensor is covered with a hand, clothes, or the like.

[Means and Actions for Solving Problems] In order to achieve the above object, a camera having an auto white balance device according to the present invention detects a color temperature of light from a light source related to an object by a color temperature detection sensor, In a camera having an auto white balance device that adjusts white balance based on a detection output of a temperature detection sensor, the first photometric value obtained based on the output of the color temperature detection sensor and the color temperature detection sensor are separately provided. The second photometric value obtained on the basis of the output of the photometric sensor provided in the first photometric sensor is compared with the second photometric value, and the abnormality detection signal is output when the comparison result deviates from the predetermined range. The color temperature of the light source light regarding the subject is detected by the color temperature detection sensor. In a camera having an auto white balance device that detects and then adjusts the white balance based on the detection output of the color temperature detection sensor, it detects whether or not an object is in proximity to or in contact with the color temperature detection sensor. An abnormality detection unit is provided which outputs an abnormality detection signal when the detection output indicating that the state is obtained is set as an abnormal state.

Practical Example FIG. 1 is a block diagram of an electric circuit of a camera having an automatic white balance device showing an embodiment of the present invention. The camera shown in FIG. 1 is a color electronic camera. In this color electronic camera, one of the object light incident from the image pickup lens 11 and one light transmitted through the half mirror 12 forming the quick return mirror is imaged by the image pickup device 13. The other light imaged on the half mirror 12 is reflected by the half mirror 14 provided on the focusing screen (not shown), the reflected light is guided to the finder lens 15, and the transmitted light is for TTL metering. Is incident on the light receiving element 16. The photoelectric conversion output of the image pickup device 13 becomes a video output by being guided to a known video signal processing circuit 17. The photoelectric conversion output of the light-receiving element 16 for TTL photometry is guided to the first photometry circuit 18, and becomes an exposure control signal or an exposure display signal for aperture control, shutter control, or the like.

Here, a color temperature detection sensor 20 is provided on the front surface of the camera body or the like for white balance adjustment. In this embodiment, the color temperature detecting sensor 20 has three primary colors of R (red), G (green), B (blue), and R and B.
The light receiving element has a high light receiving characteristic with respect to the color temperature of. The R and B signals detected by the color temperature detection sensor 20 are guided to the white balance (WB) signal processing circuit 21, where the R and B signals in the video signal processing circuit 17 are adjusted for proper white balance adjustment. Are converted into gain control signals V _R and V _B for controlling the gain of the. The gain control signals V _R , V _B obtained by the WB signal processing circuit 21 are signals that change only with the change in color temperature of the light source light (subject light) regardless of the amount of incident light. When guided to the circuit 17, the amplification degree of the R signal and the B signal of the signal processing circuit 17 is controlled.
That is, if the subject is a blank sheet, the video output of the video signal processing circuit 17 must faithfully reproduce white, and therefore the WB signal processing circuit 21 needs to reproduce the white signal.
Of the three primary color signals of R, G, and B, the signal level of R and B is properly changed to perform the control operation of the automatic white balance.

The R and B signals detected by the color temperature detection sensor 20 are also added by the adder 22 and then the second photometric circuit 23.
Then, the photometric circuit 23 measures the amount of light input to the color temperature detection sensor 20. The output of the first photometric circuit 18 and the output of the second photometric circuit 23 are guided to a comparison circuit 24 and compared. The comparison circuit 24 compares the outputs of both photometric circuits 18 and 23 and outputs the output of the second photometric circuit 23 to the first photometric circuit.
Abnormality detection signal S ₀
Emit. That is, when the light-receiving surface of the color temperature detection sensor 20 is covered with a hand or the like and the amount of incident light decreases, the output of the second photometric circuit 23 significantly decreases.
Emits an abnormality detection signal S ₀ . This abnormality detection signal S ₀ is a terminal to which well-known warning means such as an alarm buzzer and a warning lamp are connected.
It is applied to the WB signal processing circuit 21 as a signal for controlling the WB signal processing circuit 21 while being applied to 25.

The WB signal processing circuit 21 guides the R signal and the B signal detected by the color temperature detection sensor 20 to the WB control circuit 26 as shown in FIG.
R signal and B required for proper white balance adjustment
I'm trying to get a signal. This WB control circuit 26
An analog switch 27, 28 is provided in the signal path between the output end of the image signal processing circuit 17 and the video signal processing circuit 17. Normally, when the incident light of the color temperature detection sensor 20 is not blocked, the comparison circuit 24
Does not generate the abnormality detection signal S ₀ and its output is at L level, the inverter 29 applies the H level signal to the control terminals of the analog switches 27 and 28, and
27 and 28 are turned on, and the R-system and B-system gain control signals V _R and V _B from the WB control circuit 26 are analog switches 27 and 28.
It is guided to the video signal processing circuit 17 through 28 and the operation of adjusting the automatic white balance is performed. On the other hand, set voltages V _R0 , V _B0 that give a proper white balance to the light of the daylight light source (sunlight) or give a proper white balance to the light of a photo bulb.
Is a voltage setting variable resistor 3 connected between the power supply Vcc and ground
The analog switch 32 is connected between the variable terminal of the variable resistor 30 and the R system gain control input terminal of the video signal processing circuit 17, and is set by 0 and 31, respectively. An analog switch 33 is connected between the B system gain control input terminal of the signal processing circuit 17. The control terminals of the analog switches 32 and 33 are connected to the output terminal of the comparison circuit 24.
When 7,28 is on, analog switches 32,33 are off. Then, when the incident light on the color temperature detection sensor 20 is blocked, the comparison circuit 24 outputs an H level abnormality detection signal.
Since S ₀ is issued, the analog switches 27 and 28 are turned off, and the gain control signals V _R and V _B from the WB control circuit 26 are not transmitted to the video signal processing circuit 17, but at this time, the analog switch 32 , 33 are turned on, the voltages V _R0 , V _B0 set by the variable resistors 30, 31 are guided to the video signal processing circuit 17 instead of the gain control signals V _R , V _B through the analog switches 32, 33, respectively. Get burned. Therefore, even if the original auto white balance adjustment operation is not performed due to the light receiving surface of the color temperature detection sensor 20 being covered,
At this time, the standard color temperature adjustment operation is performed based on the set voltages V _R0 and V _B0 , and the standard white balance level compensation is performed while the incident light to the color temperature detection sensor 20 is blocked. The operation is performed.

Further, instead of the WB signal processing circuit 21, the WB signal processing circuit 21A having the configuration shown in FIG. 3 can be used. In the WB signal processing circuit 21A shown in FIG. 3, hold circuits 36 and 37 are connected to the output terminals of the WB control circuit 26 which generate the gain control signals V _R and V _B , respectively. The hold circuit 36 includes an analog switch 38, a hold capacitor 39 and a voltage follower buffer amplifier 40. The hold circuit 37 also has an analog switch 41 and a capacitor 4 as well.
2 and buffer amplifier 43. The output terminals of the comparison circuit 24 are connected to the control terminals of the analog switches 38 and 41 via an inverter 44. This WB signal processing circuit
In 21A, normally, when the comparison circuit 24 does not issue the abnormality detection signal S ₀ and the output is at the L level, the analog switches 38 and 41 are on, so the WB control circuit 2
The gain control signal V _R, which is the output of 6, is directly guided to the video signal processing circuit 17 through the analog switch 38 and the buffer amplifier 40, and the gain control signal V _B is directly guided to the video signal processing circuit 17 through the analog switcher 41 and the buffer amplifier 43. Adjustment operation is being performed. And the color temperature detection sensor 20
When the incident light is blocked and the comparison circuit 24 issues the H-level abnormality detection signal S ₀ , the analog switches 38 and 41 are turned off. At this point, therefore, the gain control signal V _R output from the WB control circuit 26 is output. , V _B is cut off by the analog switches 38 and 41 and is not guided to the video signal processing circuit 17. But,
When the analog switches 38 and 41 are turned off, the outputs of the WB control circuit 26 immediately before that are held in the capacitors 39 and 42, respectively, so that the held voltage replaces the real-time gain control signals V _R and V _B. The signals are guided to the video signal processing circuit 17 through the buffer amplifiers 40 and 43, respectively, and the white balance compensation operation is performed.

In the WB signal processing circuit 21 shown in FIG. 2 or the WB signal processing circuit 21A shown in FIG. 3, the white balance control signal is output from the color temperature detection sensor 20 on the output side of the WB control circuit 26. Although the switching is controlled by the output, it is not always necessary to control the output side of the WB control circuit 26, but the input side of the WB control circuit 26, that is, the output of the color temperature detection sensor 20 is switched and controlled. May be.

Although the embodiment shown in FIG. 1 is an application of the present invention to an electronic camera, it is obvious that the present invention can also be applied to a color video camera. For example, FIG. It is configured as shown in. In the color video camera shown in FIG. 4, the subject light incident from the image pickup lens 51 passes through the diaphragm 52 and forms an image on the image pickup device 53. The photoelectric conversion output of the image pickup device 53 is a video signal processing circuit. While being guided to 17, the first photometric circuit 55
Is led to one of the input terminals. The aperture control signal S _A generated by the video signal processing circuit 17 is guided to the aperture control device 54 to control the aperture of the aperture 52 according to the incident light amount of the image sensor 53, and at the same time, the first photometric circuit described above. It is led to the other input terminal of 55. In this photometric circuit 55, the photoelectric conversion output of the image pickup device 53 and the aperture control signal S _A are calculated to measure the subject light, and the photometric output is sent to the color temperature detection sensor 20 similar to that in the above embodiment. Second to measure the amount of incident light
Is introduced to the comparison circuit 24 for comparison with the photometric output of the photometric circuit 23. Other configurations are the same as the circuit configuration of the electronic camera shown in FIG. The WB signal processing circuit 21 can also be configured as shown in FIG. 2, or the WB signal processing circuit 21 can be replaced with a WB signal processing circuit 21A having a configuration as shown in FIG. Therefore, also in the color video camera shown in FIG. 1, the light-receiving surface of the color temperature detection sensor 20 is covered to reduce the amount of incident light, and the output of the second photometry circuit 23 is the first photometry circuit 55.
When lowered or is from the output value, a warning is performed by a warning means is abnormal detection signal S ₀ from the comparator circuit 24 is connected to be issued terminal 25, the abnormality detection signal S ₀ is conductive to the WB signal processing circuit 21 Original, color temperature detection sensor
Instead of the automatic white balance adjustment operation based on the output of 20, the WB signal processing circuit 21
Is switched to the compensation operation state corresponding to the standard set value of the color temperature or the color temperature immediately before the abnormality detection as described above.

In the above embodiment, the fact that the incident light amount on the color temperature detecting sensor 20 is actually reduced is detected and the incident light is judged to be blocked. This may be detected when, for example, directly touches or approaches. Figure 5 shows
In such an embodiment, the metal plate 61 is arranged around the color temperature detection sensor 20. This metal plate 61 is a high input impedance amplifier with an input impedance of several MΩ or more.
Since it is connected to 62, when the finger of the photographer touches the metal plate 61, the noise received by the human body of the photographer is picked up by the metal plate 61, and this is amplified by the high input impedance amplifier 62. This amplified noise is guided to the half-wave rectification circuit 63 and rectified, and then LPF (low-pass filter) 64
The high frequency component is cut off and only the low frequency direct current component is taken out and introduced to the comparison circuit 65. In the comparison circuit 65, the output of the LPF 64 is compared with a certain reference value, and when this output exceeds the reference value, the abnormality detection signal S ₀ is taken out to the terminal 66. This terminal
The abnormality detection signal S ₀ output to 66 is used as a signal to be guided to a warning means to give a warning, or to the WB signal processing circuit 21 to perform its white balance operation, as described in the above embodiment. It is used as a signal for performing an operation of compensating for a condition that is no longer normal.

In addition to the configuration shown in FIG. 5, a piezoelectric element, a capacitance sensor, or the like may be used in the vicinity of the color temperature detection sensor 20 to detect contact or proximity with a finger or the like. Of course.

Further, the color temperature detection sensor 20 used in the above embodiment is R
It is a two-color sensor having excellent light-receiving characteristics with respect to the two color temperatures of B and B, but it goes without saying that a three-color sensor having excellent light-receiving characteristics with respect to the color temperatures of G may also be used.

As described above, according to the present invention, when the light receiving surface of the color temperature detecting sensor is covered with a hand or clothes, this state can be immediately detected. It is possible to confirm that there is a possibility that the normal operation of auto white balance may not be performed and prevent its malfunction, or when the abnormality is detected, it is automatically switched to the compensation operation state of color temperature adjustment. Has the excellent effect of.

[Brief description of drawings]

FIG. 1 is a block diagram of an electric circuit of a camera having an auto white balance device showing an embodiment of the present invention, and FIG. 2 is an electric circuit diagram showing an example of a WB signal processing circuit in FIG. FIG. 3 is an electric circuit diagram showing another example of the WB signal processing circuit. FIG. 4 is a block diagram of an electric circuit of a camera having an automatic white balance device showing another embodiment of the present invention. FIG. 9 is a block diagram of an electric circuit in a main part of a camera having an automatic white balance device showing still another embodiment of the present invention. 16 …… Light receiving element (photometric element) 18 …… Photometric circuit (〃) 20 …… Color temperature detection sensor 24 …… Comparison circuit (abnormality detection means) 53 …… Image sensor (photometric element) 55 …… Photometric circuit (〃 ) 61 …… Metal plate (Abnormality detection means) 65 …… Comparison circuit (〃) S ₀ …… Abnormality detection signal

Claims (2)

[Claims] 1. A camera having an automatic white balance device for detecting a color temperature of light from a light source with respect to a subject by a color temperature detecting sensor and adjusting white balance based on a detection output of the color temperature detecting sensor. First obtained based on the output of the detection sensor
When the photometric value and the second photometric value obtained based on the output of the photometric sensor provided separately from the color temperature detection sensor are compared and the comparison result deviates from the predetermined range. A camera having an automatic white balance device, comprising: an abnormality detection unit configured to output an abnormality detection signal in which an abnormal state is indicated. 2. A camera having an auto white balance device for detecting a color temperature of light from a light source with respect to an object by a color temperature detecting sensor and adjusting white balance based on a detection output of the color temperature detecting sensor. An abnormality detecting means for detecting whether or not an object is in proximity to or in contact with the detection sensor and outputting an abnormality detection signal as an abnormal state when a detection output indicating that the object is in that state is obtained. A camera having an automatic white balance device characterized by being provided.