JPH05347765A - Automatic white balance adjusting device - Google Patents

Abstract

PURPOSE:To attain optimum white balance adjustment by providing a deciding means which decides that a peripheral light source of a subject is identical with a fluorescent lamp except an AC lighting fluorescent lamp of the commercial frequency. CONSTITUTION:When the color information is inputted from an A/C converter 8, a high frequency flicker detecting circuit 39 or a flicker detecting circuit 38 decides whether the flicker is detected or not. If so, the characteristic information is read out of a 2nd control table 22 which has the white balance adjustment characteristic when the subject is illuminated by the natural light. If not, the characteristic information is read out of a 1st control table 21 having the white balance adjustment characteristic when the subject is illuminated by the light of a fluorescent lamp. Then the gains of the variable amplifier circuits 4R and 4B are controlled based on the color information given from the converter 8 and the characteristic information given from the table 21 or 22. Thus the output of an image pickup part 3 undergoes white balance adjustment.

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 such as a video camera for recording images and an electronic still camera for recording still images.

[0002]

2. Description of the Related Art The human eye has the flexibility of seeing a white object as white even if the color temperature of illumination light changes.
On the other hand, with video cameras, electronic still cameras, etc.,
A white subject cannot be reproduced in white unless the white balance is adjusted according to the color temperature of the light around the subject.

FIG. 4 shows an example of an automatic white balance adjusting circuit in a conventional color camera. In this figure, an image pickup unit 203 that receives light from a subject (not shown) via an optical system 201 and a diaphragm 202 is a color solid-state image pickup device such as a CCD (charge transfer device) or a MOS device, and a predetermined amount from the image pickup device. And a circuit for taking out the imaging output at the synchronization timing of R, R (red), G (green), B
Outputs signals for each color (blue).

Outputs R and B from the image pickup unit 203 are variable amplifications for white balance adjustment controlled by the control unit 210 according to color temperature information from a color measurement unit 230 that measures the color temperature of the ambient light of the subject. The output G is directly input to the signal processing unit 205 via the circuits 204R and 204B. The signal processing unit 205 adjusts the gain, setup level, gamma and knee of each color signal,
The image signal output is sent to the recording unit 206 such as a magnetic recording device. Further, the diaphragm 202 is controlled by the control unit 210 so as to provide proper exposure by the output from the photometry unit 207 that measures the brightness of the subject.

Next, the control of the variable amplifier circuits 204R and 204B for white balance adjustment will be described below.
In the colorimetric unit 230, the ambient light of the subject is incident on the R light receiving element 232R, the G light receiving element 232G, and the B light receiving element 232B via the diffusion plate 231, and the red component Rb and the green component Gb of the incident light are emitted from these light receiving elements, respectively. , And the blue component Bb is output.

These are logarithmically compressed by the logarithmic compression circuit 233 and output as log Rb, log Gb and log Bb. Next, in the subtraction circuits 234 and 235, log (Rb /
Gb), log (Bb / Gb) and expanded circuit 23
Inverse log conversion into Rb / Gb and Bb / Gb at 6 and further through the current / voltage conversion circuit 237, A / D converter 208
Are digitally converted by the above and are output to the control unit 210 as color temperature information. Also, log Gb logarithmically compressed
The output is input to the flicker detection circuit 238, and if the signal includes flicker of light from the fluorescent lamp lit at the commercial frequency, a detection signal is generated from the flicker detection circuit 238 and output to the control unit 210. .. This flicker detection circuit detects a flicker component of 100 to 120 Hz, and specifically, a known comparator or the like is used.

When the flicker detection circuit 238 determines that the light source has no flicker, the control unit 210 follows the control information for natural light stored in the first control table 221 for white balance adjustment prepared in advance. ,
The gains of the variable amplifier circuits 204R and 204B are controlled according to the digital outputs of Rb / Gb and Bb / Gb from the color measuring unit 230. On the other hand, when flicker is detected by the flicker detection circuit 238, the control unit 210 determines that the light source is a fluorescent lamp, and stores it in the second control table 222 for white balance adjustment prepared in advance. Rb from the color measurement unit 230 according to the control information for the fluorescent lamp
The gains of the variable amplifier circuits 204R and 204B are controlled according to the digital outputs of / Gb and Bb / Gb. In this way, the white balance adjustment is automatically performed for each case of natural light or fluorescent lamp illumination light.

[0008]

By the way, in recent years, a high frequency lighting fluorescent lamp using a thyristor or a transistor inverter has been increasing in place of the AC lighting system of commercial frequency. In the conventional auto white balance adjustment device, the flicker detection circuit detects flicker included in light from an AC lighting fluorescent lamp at a commercial frequency, that is, flicker of 100 to 120 Hz which is twice the frequency of 50 to 60 Hz. Therefore, the high-frequency flicker of several kHz to several tens of kHz included in the light from the fluorescent lamp of the inverter lighting system is not detected, and the control unit judges it as natural light that is not a fluorescent lamp.
The automatic white balance adjustment is performed in a mode in which the gains of the variable amplifier circuits 204R and 204B are controlled according to the first white balance control table 221 for natural light. Therefore, there is a problem that the color of the photographed object is reddish or bluish under the light of a high-frequency lighting fluorescent lamp.

The present invention solves the above problems and provides accurate automatic white balance even when photographing under the light of a fluorescent lamp other than an AC lighting fluorescent lamp of a normal commercial frequency such as a high frequency inverter lighting fluorescent lamp. The purpose is to obtain a device that can be adjusted.

[0010]

In order to achieve the above object, in the automatic white balance adjusting apparatus according to the invention described in claim 1, it is judged that the light source around the subject is an AC lighting fluorescent lamp of commercial frequency. No. 1 determination means, a first storage means having a white balance adjustment characteristic when the subject peripheral light source is natural light, and a second storage means having a white balance adjustment characteristic when the subject peripheral light source is a fluorescent lamp. In the automatic white balance adjusting device including: a second judgment means for judging that the light source is a fluorescent lamp other than the AC-lighted fluorescent lamp of the commercial frequency, and at least one of the first and second judging means. When a judgment is made, it is based on the output of the second storage means, and when no judgment is made by any of the judgment means, it is based on the output of the first storage means. Te is one having an adjusting means for adjusting the white balance.

According to a second aspect of the present invention, there is provided an automatic white balance adjusting device according to the first aspect, wherein the automatic white balance adjusting device further comprises component signals relating to red, green and blue from the ambient light of the subject. Detect
A measuring means for measuring a color temperature from the component signal, wherein the adjusting means makes an adjustment based on the measurement result of the measuring means and the outputs of the first storing means and the second storing means,
The second judging means judges, by using the green light component signal detected by the measuring means, that the light source is a fluorescent lamp other than the AC-lighted fluorescent lamp of the commercial frequency.

Further, in the automatic white balance adjusting apparatus according to a third aspect of the present invention, in the automatic white balance adjusting apparatus according to the first aspect, the second judging means determines that the light source is the light source depending on the presence or absence of flicker. It is determined that the fluorescent lamp is a fluorescent lamp other than the AC-lighted fluorescent lamp of commercial frequency.

Further, in the automatic white balance adjusting device according to the invention described in claim 4, in the automatic white balance adjusting device according to claim 1, the fluorescent lamps other than the AC lighting fluorescent lamp of the commercial frequency have a frequency of about 40 kHz. It is an AC lighting fluorescent lamp.

[0014]

According to the present invention, the light source around the subject is at the commercial frequency because it is an automatic white balance adjusting device provided with a determining means for determining whether the light source around the subject is a fluorescent lamp other than the AC lighting fluorescent lamp at the commercial frequency. Optimal white balance adjustment is possible even for fluorescent lamps other than the AC lighting fluorescent lamp.

[0015]

EXAMPLES Examples of the present invention will be described below. Figure 1
FIG. 7A is a block diagram showing the configuration of an automatic white balance adjustment circuit in this embodiment together with the main part of the camera. In this figure, light from a subject (not shown) is imaged on the light receiving surface of the image pickup unit 3 via the optical system 1 and the diaphragm 2. The image pickup unit 3 includes a CCD (charge transfer device) and a MOS.
It is composed of a color solid-state image pickup device such as a device and a circuit for taking out an image pickup output from the image pickup device at a predetermined synchronization timing. The output from the image pickup unit 3 is R (red), G
(Green) and B (blue) color signals.

Outputs R and B from the image pickup unit 3 are variable amplification for white balance adjustment controlled by the control unit 10 according to color temperature information from the color measurement unit 30 which measures the color temperature of the ambient light of the object. Output G through circuits 4R and 4B
Is directly input to the signal processing unit 5. The signal processing unit 5
The gain, setup level, gamma and knee of each color signal are adjusted, and the image signal output is sent to the recording unit 6 such as a magnetic recording device. Further, the diaphragm 2 is controlled by the control unit 10 so as to give proper exposure by the output from the photometry unit 7 which measures the brightness of the subject.

Next, the control of the variable amplifier circuits 4R and 4B for white balance adjustment will be described below. Colorimeter 3
At 0, the ambient light of the subject is incident on the R light receiving element 32R, the G light receiving element 32G, and the B light receiving element 32B via the diffusion plate 31, and the red component R of the incident light from each of these light receiving elements
b, the green component Gb, and the blue component Bb are output.

These color component signals are logarithmically compressed by a logarithmic compression circuit 33 to obtain log Rb, log Gb and log Bb.
Will be output. Next, in the subtraction circuits 34 and 35, log
(Rb / Gb) and log (Bb / Gb) are converted to Rb / Gb and Bb / Gb are inversely log-converted by the expansion circuit 36, and A / A is further converted via the current / voltage conversion circuit 37.
It is digitally converted by the D converter 8 and output to the control unit 10 as color temperature information.

On the other hand, log Gb logarithmically compressed is 100 to 100.
Flicker detection circuit 3 for detecting 120 Hz amplitude fluctuation component
It is input to a high frequency flicker detection circuit 39 which detects amplitude fluctuation components of 8 and 80 kHz. Here, detection of light flicker from a fluorescent lamp by a commercial frequency AC lighting system and high-frequency flicker detection of light from an inverter lighting system fluorescent lamp are separately detected from a logarithmically compressed output log Gb signal. It is possible. This detection target frequency is, for example, in a high-frequency inverter lighting fluorescent lamp for general indoor lighting, the lighting frequency is almost 40 kHz at present, so it is doubled to 80 kHz. Since the lighting frequency is 20 kHz, the frequency may be doubled. For detection, a method using one or more corresponding bandpass filters, a method using a light receiving element sensitive to a high frequency of kHz order, and the like can be adopted. Here, a method of detecting a frequency component of 80 kHz is used to detect high frequency flicker.

As a method of detecting the high frequency component, for example, the circuit shown in FIG. 1B is used. That is, the output log Gb which is logarithmically compressed by the logarithmic compression circuit 33 is set to 80 kHz.
The bandpass filter 4 is passed through the bandpass filter 41.
The output from 1 is integrated by the integrator 42 having a predetermined time constant, and the integrated output is digitally converted by the A / D converter 43 and input to the control unit 10. In the control unit 10, the output levels of the integrator 42 are digitally compared, and if this is greater than or equal to a predetermined constant K, it is determined that the subject light includes light from the inverter fluorescent lamp. The control unit 10 selects the control table described below according to the determination result.

In this embodiment, the first control table 21 and the second control table 21 are used as white balance adjustment control tables according to the digital output of the color information: Rb / Gb and Bb / Gb from the colorimetric section 30 in advance. And the control table 22 of No. 2 are prepared. The first control table 21 has characteristic information for white balance adjustment when the light source is natural light, and the second control table 22 has characteristic information for white balance adjustment when the light source is a fluorescent lamp. The characteristic information stored in advance in the two control tables 21 and 22 is the characteristic information of the first control table 21 when neither the flicker detection circuit 38 nor the high frequency flicker detection circuit 39 produces a detection output. When either one of them produces a detection output, the second control table 22
Characteristic information is selectively extracted, and the control unit 10 controls the white balance adjustment variable amplifier circuit 4R according to the color information from the color measurement unit 30 based on the extracted characteristic information.
4B gain control is performed.

FIG. 3 is a flow chart showing the control relating to the white balance of the control unit in this embodiment. In FIG. 3, when color information is input from the A / D converter 8 (101), the high frequency flicker detection circuit 3
9 or flicker is detected by the flicker detection circuit 38 (102), and when detected, the flicker is stored in the second control table having the white balance adjustment characteristic when the subject illumination light is natural light. The characteristic information is read (103). If it is not detected, the characteristic information stored in the first control table having the white balance adjustment characteristic when the subject illumination light is the light from the fluorescent lamp is read (104). The color information input from the A / D converter and the read second control table or first
The gains of the variable amplifier circuits 4R and 4B are controlled on the basis of the characteristic information from the control table (1) to white balance the output from the image pickup unit 3 (105).

FIG. 2 shows a second embodiment of the present invention, in which an inverter fluorescent lamp is discriminated by a light receiving element 141 having a light receiving sensitivity for incident light having a high frequency amplitude fluctuation, and a light receiving element 141 connected thereto. A high frequency flicker detection circuit 142 is used. The high frequency flicker detection circuit 142 can be composed of a filter and an integrator. In this case, it is not necessary to use the output signal from the light receiving element (32R, 32G, 32B) for color measurement to detect the high frequency amplitude fluctuation component included in the light from the inverter fluorescent lamp. It is sufficient if the light receiving element 141 and the high frequency flicker detection circuit 142 are additionally provided.

Further, in the case where the lighting frequency of the inverter fluorescent lamp is different from each other, it is sufficient to provide a detection circuit of twice the frequency component according to the lighting frequency of each inverter fluorescent lamp. It is also possible to select corresponding characteristic information and perform optimum white balance adjustment.

[0025]

As described above, according to the present invention, even if the ambient light of an object is light from a fluorescent lamp other than an AC-lighted fluorescent lamp having a normal commercial frequency, a proper color balance adjustment is made by a judging means for judging this. It is possible to perform an appropriate white balance adjustment by selecting a characteristic, and for example, to provide a white balance adjustment device that can be used even when shooting with a high frequency inverter lighting fluorescent lamp as a light source, which has been popularized in recent years. Can be done.

[Brief description of drawings]

FIG. 1A is a block diagram showing a configuration of an automatic white balance adjusting apparatus according to a first embodiment of the present invention together with a main part of a color camera, and FIG. 1B is a high-frequency flicker detection circuit used here. It is a block diagram showing a system.

FIG. 2 is a block diagram showing a configuration of an automatic white balance adjusting apparatus according to a second embodiment of the present invention together with a main part of a color camera.

FIG. 3 is a flowchart showing the operation steps of white balance adjustment in the automatic white balance adjustment device shown in FIG.

FIG. 4 is a block diagram showing a configuration of a conventional automatic white balance adjusting device together with a main part of a color camera.

[Explanation of symbols]

1, 201: Optical system 2, 202: Aperture 3, 203: Imaging unit 4R, 4B, 204R, 204B: Variable amplifier circuit for white balance adjustment 5, 205: Signal processing unit 6, 206: Recording unit 7, 207: Photometry Part 10, 210: Control part 21,221: First control table 22, 222: Second control table 30,230: Colorimetric part 31,231: Diffuser 32R, 232R, 32G, 232G, 32B, 232
B, 142: Light receiving element 33, 233: Logarithmic compression circuit 38, 238: Flicker detection circuit 39, 142: High frequency flicker detection circuit 34, 234, 35, 235: Subtraction circuit 36, 236: Expansion circuit 37, 237: Current voltage Conversion circuit

Claims (4)

[Claims] 1. A first determining means for determining that the light source around the subject is an AC-lighted fluorescent lamp of commercial frequency, and a first storage means having a white balance adjustment characteristic when the light source around the subject is natural light. An automatic white balance adjusting device having a second storage unit having a white balance adjusting characteristic when the light source around the subject is a fluorescent lamp, wherein the light source is a fluorescent lamp other than the AC-lighted fluorescent lamp of the commercial frequency. When the judgment is made by the second judgment means for judging the above and at least one of the first and second judgment means, based on the output of the second storage means, no judgment is made by any judgment means. An automatic white balance adjusting device, characterized in that the automatic white balance adjusting means comprises an adjusting means for adjusting the white balance based on the output of the first storage means. 2. A measuring means for detecting a component signal for each color of red, green, and blue from ambient light of an object and measuring a color temperature from the component signal is provided, and the adjusting means includes a measurement result of the measuring means. Adjustment is made based on the outputs of the first storage means and the second storage means, and the second determination means uses the green light component signal detected by the measurement means to output the light source to the commercial source. The automatic white balance adjusting device according to claim 1, wherein the automatic white balance adjusting device determines that the fluorescent lamp is a fluorescent lamp other than an AC lighting fluorescent lamp having a frequency. 3. The auto according to claim 1, wherein the second judging means judges that the light source is a fluorescent lamp other than the AC-lighted fluorescent lamp of the commercial frequency depending on the presence or absence of flicker. White balance adjustment device 4. The automatic white balance adjusting apparatus according to claim 1, wherein the fluorescent lamps other than the AC-lighted fluorescent lamp of the commercial frequency are AC-lighted fluorescent lamps of about 40 kHz.