JPS63284435A - Color temperature detector - Google Patents

Abstract

PURPOSE:To detect the color temperature of incident light over a wide illuminance range by detecting charges which are excited with the incident light and stored by color components and outputting them as color temperature information according to a discharge time length signal corresponding to the amount of stored charges. CONSTITUTION:A color component detection part 1 decomposes the incident light into three primary color components and converts them photoelectrically to outputs voltages corresponding to the charges stored in a converter as color signal components SR, SG, and SB. A comparison part 2 compares the signals, SR, SG, and SB with reference voltages VR, VG, and VB and detects the time up to when the signals SR, SG, and SB which vary with the amount of stored charges reach the voltages VR, VG, and VB, thereby outputting comparison signals CR, CG, and CB. Further, a NOR circuit 24 outputs a comparison end signal CE to a detection part 1 according to the detection result. An output part 24 finds the ratio of the respective color components according to the signals CR, CG, and CB and outputs color temperature information as a red output signal RC and a blue output signal BC. Thus, the detection is performed over a wide illuminance range.

Description

[Detailed Description of the Invention] [Industrial Application Field] The invention is a color suitable for a white balance device of a color television camera, etc., which detects color components in illumination of a subject and automatically performs white balance. The present invention relates to a temperature detection device.

[Technology background]

White balance in color television cameras is one of the important signal adjustments. White balance means that the component ratio of the three primary colors (red, green, and blue) in the illumination of the subject (i.e., the light surrounding the subject) is 1:1 for a white subject.
This means that the gain of the color signal of the photographed object is variably adjusted so that the color signal becomes 1. The component ratio of the three primary colors varies depending on the type of lighting, so if the white balance is incorrectly adjusted, the entire photographed screen will appear realistic or reddish, making it impossible to faithfully reproduce colors.

Therefore, an outer automatic tracking white balance device has been proposed as a white balance device that accurately and automatically adjusts the white balance device (Japanese Patent Laid-Open No. 54-5392
4, JP-A-55-158792, etc.). These devices detect the external light of the subject using a light receiving system that is installed separately from the imaging system, and automatically adjust the white balance. Alternatively, install three optical sensors, detect two or three different color components from the ambient light, logarithmically compress them, and then calculate the difference between each color component isometrically. A configuration in which white balance is performed by detecting the ratio and controlling the gain of the color signal amplifier of the imaging system according to the ratio.
be.

[Problem that the invention seeks to solve]

However, in the conventional device described above, in order to deal with peripheral light in a wide illuminance range, high accuracy is required for the logarithmic compression amplifier, and a correction circuit such as temperature correction is required, which causes problems with the device. This has led to increased complexity and higher costs.

An object of the present invention is to provide a color temperature detection device that can accurately detect the color temperature of incident light over a wide illuminance range with a simple configuration.

[Means for solving problems]

The color temperature detection device according to the present invention includes: a color component detection means for detecting charge excited by incident light and accumulated over time for each color component and outputting it as a color component signal; a comparison means for comparing the signal with the signal and outputting it as a time length signal proportional to the amount of accumulated charge; and calculating a ratio of each color component based on the time length signal from the comparison means, and generating a signal corresponding to the ratio as color temperature information. It consists of an output section that outputs data, and

[Effect]

According to the configuration of this invention, the intensity of each color component of incident light is
It detects the amount of charge excited according to the amount of light, and then outputs it as a time length signal by detecting the entire discharge time of this charge, and outputs the signal based on the time length as color temperature information, so it has a simple configuration. It is possible to detect the color temperature of incident light over a wide illuminance range.

Therefore, when applied to the light receiving system of the above-mentioned external automatic tracking white balance device, accurate white balance adjustment can be performed with a simple configuration.

〔Example〕

FIG. 1 is a circuit diagram showing an embodiment of a color temperature detection device according to the present invention.

The color component detection unit l separates the three primary colors in the incident light into each component and photoelectrically converts the components, and outputs voltages corresponding to the charges accumulated in the converter as a red component signal SR, a green component signal SG, and a '# color component. This is output as signal SB.

It has a diffuser plate 11 that diffuses the incident light that has passed through the light receiving system to eliminate uneven color information, and the light that has passed through the diffuser plate 11 is
Red (6), green a), blue (B) color filters 12,1
3 and 14, each color component is taken out and sent to the photoelectric converter 1.
5, 16, and 17.◎ These photoelectric converters 15 to 17 output the charge accumulated by photoexcitation as a voltage signal, as will be explained in detail in Fig. 2 below. The voltage signal is the color component signal SR, SG
, 8B. Therefore, these color component signals SR, SG
, SB are voltage signals that change depending on the amount of accumulated charge.

The reset circuit 18 receives a comparison end signal CE from the comparator 2, which will be described later, and a signal H synchronized with the horizontal synchronization signal of the television.
8, a reset signal R81 with a constant error width is generated, and the photoelectric converters 15 to 17 erase the accumulated charges by this reset signal R8 and return to their initial states.

The readout circuit 19 includes a photoelectric converter 15°16.17 which will be described later.
Emitter voltage SSR output from.

88G and 888, and outputs a common continuous signal RE when any one of these signals reaches a predetermined level.

FIG. 2 is a circuit diagram showing an example of the photoelectric converters 15 to 17.

In the figure, capacitor C1 has one plate connected to input terminal 15m, and the other plate connected to phototransistor q.
1 and is grounded via FETQ2. The input terminal 15m has a reset signal R8.
and read signal RE are supplied.

The collector terminals of the 7t transistors Q, ti, and y are connected to the power supply terminal 15b, and the emitter terminals are connected to the output terminal 15e, respectively.Furthermore, the emitter terminals are grounded through FET Q3, and connected to capacitor C2 through FET Q4t? Connected to one plate.

One plate of the capacitor C2F1 is connected to the output terminal 15d, and the other plate is grounded together with the parallel-connected diode D and constant current source To. From the output terminal 15d, the 11 charges accumulated in the capacitor C2 are output as a color component signal.

Furthermore, the darts of FETs Q2 and Q3 are connected to the control terminal 15 to which the reset signal R8 is supplied, and the darts of FETs Q2 and Q3 are
The dart Q4 is connected to the control terminal 1 to which the read signal RE is supplied.
Connected to 5f.

The above is the configuration of the photoelectric converter. In addition, capacitor C3
The capacitance is set such that the capacitance for the G component is 172 compared to the capacitance for the R and B components. Maku,
The constant current source 16 may be provided commonly to the photoelectric converters 15 to 17.

Returning to FIG. 1 again, the comparator 2 receives the color component signal SR,8.
G, SB are compared with reference voltages VR, VG, VB, and color component signals SR, SG change depending on the amount of accumulated charge.
, SB are set to predetermined reference voltages VR, VG, VB, respectively.
It detects the time until K is reached, and consists of an OP amplifier configuration including a red comparator 21 and a green comparator 22. It has a blue comparator 23.

The non-inverting terminals of the comparators 21, 22, and 23 receive the color component signal S.
R, SG, and SB are input, and the reference voltage VR is input to the inverting terminal.
, VG, and VB are input. Therefore, comparator 21.
22.23 outputs "L" level comparison signals CR, CG, CBt- until the color component signals SR, SG, SB reach the reference voltages VR, VG, VB, and then reach the "H" level.

Further, the NOR circuit 24 receives color component signals SR and SG.

It is detected that all of 8B have reached the level of the corresponding reference voltages VR, VG, and VB, and a comparison end signal CE is output to the color component detection section l.

Note that the reference voltages VR, VG, and VB are all set to 0 [v] in this example.

The output unit 3 outputs color temperature information corresponding to the color temperature of the incident light based on the comparison signals CR, CG, and CB, and as described above, the comparison signals CR, CG.

Since CB is a signal obtained by converting the initial accumulation amount of each color component signal 19R, SQ, and 19B into a time length, the time lengths are compared to find the ratio between each color component, and the good signal is colorized according to the ratio. It is configured to output as temperature information. In this example, the green comparison signal CGt - as a reference, the red comparison signal CR and the blue comparison signal C to this signal CG.
Find the time ratios of B and apply them to the smoothing circuit 40.4
1 and converts it into a voltage signal and outputs it as a red output signal RC and a blue output signal BC, respectively.A logic circuit consisting of an inverter 31 and AND circuits 32 to 35, and a red signal depending on the output of this logic circuit. Output voltage ER
1 and EB2(EB2(ER,) ft Selecting switches 36 and 37 and blue output voltages EB and EB
2 (EB2<EB, ), and smoothing circuits 40 and 41 that smooth the selected red output voltage and blue output voltage, respectively.

The AND circuit 32 performs a logical product of the comparison signals CR and CG, and its output is a switch 36 that selects the output voltage ER1.
This becomes the control signal. Further, the AND circuit 33 performs a logical product of the comparison signal CR and the inverted signal of CC, and its output becomes a switch 370 control signal for selecting the output voltage ER21. The red output voltages ER and EB2 selected at a predetermined time ratio by the switches 36 and 37 are smoothed by the smoothing circuit 4o and outputted as a red output signal RC.

The blue color has a similar configuration, and the AND circuit 34 outputs the comparison signal CB.
and CG, and its output controls a switch 38t which selects the output voltage EB, and an AND circuit 3
In step 5, perform the AND of the comparison signal CB and the inverted signal of CG.
The output controls a switch 39 that selects the output voltage EB2. The blue output voltage EB and EB2 at the predetermined time ratio selected by the switch 38 or 39 are outputted by the smoothing circuit 41.
is smoothed and output as a blue output signal BC.

The above is the configuration of the embodiment of this invention. Next, the operation of this embodiment will be explained with reference to the waveform diagram in FIG. Note that only the red color will be explained here, and the description of the blue color will be omitted since it is the same.

First, time t. When the reset signal R8 is generated (FIG. 3A), the capacitors C of the photoelectric converters 15 to 17 are
4 is discharged via FETs Q2 and Q3 (reset operation).

At time t1, when the reset state is released, charges are accumulated in each capacitor C1 of the photoelectric converters 15 and 16 over time. This charge is transferred to the phototransistor Q,
Emitter voltage SSR, SA from output terminal 15c via
Output as G. Now, if the color temperature of the incident light is low, the signal will maintain the SSG (SSH) relationship and increase with time (Fig. 3B) [accumulation operation].

At time t2, the emitter air pressure SSR reaches the predetermined reference voltage vs, so the readout signal RE is generated from the readout circuit 19 (Fig. 3C), and the FETs of the photoelectric converters 15 and 16 are
Q4 is turned on, the potential of capacitor C1 is increased, and the accumulated charge is transferred to capacitor C2 [read operation].

The electric charge accumulated in the capacitor C2 is discharged at a constant rate by the constant current source 1o from time t3, and the electric charge is discharged at a constant rate from the time t3 to the output terminal 15d.
are output as color component signals SR and SG, respectively (
Figure 3D). Immediately after the read operation, the outputs of the comparators 21 and 22 of the comparator 2 rise from the Ill L 5 level to the "H" level (FIG. 3E, F).

At time t4, the color component signal SG reaches the reference voltage VG, so the comparison signal CG returns to the "L" level (Fig. 3E)
). Furthermore, at time t5, the color component signal SR reaches the reference voltage, so the comparison signal CR also returns to the "L" level (
Figure 3F) [Comparison operation].

The nine comparison outputs CR and CG thus obtained are supplied to the output section 3.

Now 1 time t1-t2t 1 hour T. 1 If time t2 to t4 is time T1 and time t4 to t5 is time T2, time 〒
1, the AND condition of the AND circuit 32 is satisfied, so
When the switch 36 is on and the switch 37 is off (the third
Figures G and H), the output voltage ER1 is supplied to the smoothing circuit 40 (third diagram).

・Next, at time 2, the AND condition of the AND circuit 33 is satisfied, the switch 36 is off and the switch 37 is on (FIG. 3 G, H), and the output voltage ER2 is the same as that of the smoothing circuit 4.
0 (3rd diagram).

After time t5, the AND conditions of AND circuits 32 and 33 are not satisfied, and switches 36 and 37 are both turned off (
(G, H) in FIG. 3, the input to the smoothing circuit 40 becomes a high impedance Q (I(IGHZ)) (■ in FIG. 3).

In this way, the signal shown in FIG. 3 is input to the smoothing circuit 40. Since the smoothing circuit 40 has a large time constant, when a plurality of vehicle pressure signals of different levels are input, it outputs the average value according to the supply time ratio of each input voltage, and the input is in a high impedance state. When , the previous voltage state is maintained.

Therefore, the red output signal RC takes a value between the voltages ER and ER2 depending on the input time T1 and the ratio of 〒2 of the output voltages ER1 and ER2. To explain this relationship in detail, now the amount of light incident on the photoelectric converter 150 t-
Assuming LR, the incident light amount LG of the photoelectric converters 1 and 6, and their respective conversion coefficients tAR and AG, and the readout voltage 1v□, v8°, then V, 1mLR@AR@T.

V,, ==LG-AG-T.

becomes. Therefore, the signals SR and SG are at the reference voltage V
R, VG (VR=VG=O[V)) The time it takes to reach VC is the capacitance of the capacitor C2 of the photoelectric converter 15, tcBs, the total capacitance of the capacitor C2 of the photoelectric converter 16, C. When you toss it, it becomes .

Since the red output signal RC is the average value of the voltages ER and ER2 input to the smoothing circuit 40 during one hour T and T2, here, CR-2C, so the following is obtained.

As is clear from equation (1), the red output signal RC has voltages ER1 to E depending on the ratio of the R component and the G component of the incident light φ.
This is a signal that changes between R20, and when the R component is smaller than the G component, it approaches the voltage ER, and when it is larger, it approaches the voltage ER2, and is used to control the gain of the red signal amplifier of the imaging system (not shown). Become.

When all the color component signals reach the corresponding reference voltages, the condition of the NOR circuit 24 of the comparator 2 is satisfied, and the comparison end signal CE is supplied to the reset circuit 18. In this state, when the signal H8 synchronized with the horizontal synchronization signal of the television is applied to the reset circuit 18 at time t6, the reset signal R8 is generated again, the electric charge of the photoelectric converters 15 to 17Fi capacitor C4 is discharged, and the initial state is reset again. After that, the same operation is repeated.

In the above embodiments, the red (8) component, the edge) component, and the blue (B) component of the incident light are used. Although the configuration is configured to detect color components, the present invention is not limited to this, and two or four or more color components may be detected.

〔Effect of the invention〕

As described above in detail, the color temperature detection device according to the present invention detects the intensity of each color component of incident light as a time length signal from the discharge time corresponding to the amount of charge excited depending on the scene, Since a signal based on the time length is outputted as color temperature information, it is possible to detect the color temperature of incident light in a wide illuminance range with a simple configuration.

Therefore, when applied to the light receiving system of the external single-motion tracking white balance device as described above, it becomes possible to perform accurate white balance adjustment with a simple configuration. Moreover, in the present invention, since the magnitude of each color component signal is detected depending on the discharge time, the time T and T2 are almost constant without being influenced much by the intensity of the incident light, so the output of the smoothing circuit is becomes stable.

Temporarily, comparators 21 to 23 calculate the emitter voltage SSR.

The levels of SSG and SSB are set to the reference voltage VR, respectively.
VG.

When configured to directly compare with VB, the comparison time in the comparators 21 to 23 changes, for example, from 100 μsec to Zoo ms@c depending on the strength of the incident light as described above, and the response time for white balance adjustment changes. This can be a problem in that it changes significantly depending on the strength of the incident light, and the matching with the time constant of the smoothing circuit also deviates depending on the strength of the incident light, resulting in errors. It can also solve problems.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing an embodiment of the present invention, Fig. 2 is a circuit diagram showing an example of the photoelectric converter of Fig. 1, and Fig. 3 is a circuit diagram showing an example of the photoelectric converter of Fig. 1. FIG. 1... Color component detection section 2... Comparison section 3... Output section

Claims (1)

[Claims] 1. (a) color component detection means for detecting charge excited by incident light and accumulated over time for each color component and outputting it as a color component signal; (b) said color component; a comparison means for comparing the signal with a predetermined reference signal and outputting the signal as a discharge time length signal corresponding to the accumulated charge amount; (c) determining a ratio of each color component based on the time length signal from the comparison means; A color temperature detection device comprising: an output section that outputs a signal according to color temperature information as color temperature information;