JPH03188787A - White balance adjustment device - Google Patents

Abstract

PURPOSE:To easily obtain a desired dynamic range by providing plural expansion circuits having an opposite change characteristic to a compression conversion characteristic of a photoelectric conversion compression circuit and selectively outputting any output of the above circuit in response to the given control signal. CONSTITUTION:Expansion circuits 15, 16, 36, 38 have opposite conversion characteristic to a compression conversion characteristic of photoelectric conversion compression circuits 200a, 200b, 200c. Then outputs of subtraction circuits 13, 14 are subject to exponential transformation, then the deviation in a DC level is absorbed by the deviation in the gain and the DC level of the signal outputted from each circuit is made constant. Thus, a level gain adjustment circuit is not required. Moreover, the switches 17, 35, 39, 40 are selectively closed by a control signal from a control signal input terminal 19 to select an expansion circuit with a desired gain. As a result, it is not required to interlock the DC level adjustment and the gain adjustment and the desired dynamic range is easily obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a white balance adjustment device for adjusting the white balance built into a video camera or the like.

[Conventional technology]

FIG. 3 is a block diagram of a conventional white balance adjustment device. In the figure, 1 is a red filter, 2 is a green filter, 3 is a blue filter, 4 is an optical sensor that receives the transmitted light of the red filter 1, 5 is an optical sensor that receives the transmitted light of the green filter 2,
Reference numeral 6 denotes an optical sensor that receives the light transmitted through the blue filter 3.

1o is an operational amplifier with the optical sensor 4 connected between its input terminals, 11 is an operational amplifier with the optical sensor 5 connected between its input terminals, and 12 is an operational amplifier with the optical sensor 6 connected between its input terminals. 7 is a diode connected between the inverting input and output of the operational amplifier 10, 8 is a diode connected between the inverting input and output of the operational amplifier 11, and 9 is the operational amplifier 12.
is a diode connected between the inverting input and output of Red filter 1. Optical sensor 4. The photoelectric conversion compression circuit 200a is connected to the green filter 2 by the diode 7 and the operational amplifier 10.
゜Optical sensor 5. The diode 8 and the operational amplifier 11 constitute a photoelectric conversion compression circuit 200b, and the blue filter 3, the optical sensor 6, the diode 9, and the operational amplifier 12 constitute a photoelectric conversion compression circuit 200c.

13 is a subtraction circuit that takes the difference between the outputs of operational amplifiers 10 and 11; 14 is a subtraction circuit that takes the difference between the outputs of operational amplifiers 11 and 12; and 20 is a temperature compensation circuit that performs temperature compensation on the output of the subtraction circuit 13. , 21 is a temperature compensation circuit that performs temperature compensation on the output of the subtraction circuit 14, 22 is a level gain adjustment circuit that is connected to the output of the temperature compensation circuit 20 and adjusts the DC level and gain of the output, and 23 is a temperature compensation circuit. connected to the output of 21,
A level gain adjustment circuit that adjusts the DC level and gain of the output; 24 is an R/G output terminal connected to the output of the level gain adjustment circuit 22; 25 is a level gain adjustment circuit 2;
This is the B/G output terminal connected to the output of No. 3.

Next, the operation will be explained. The incident light is passed through a red filter, a green filter 2. The light passes through the blue filter 3 and is received by the optical sensors 4, 5.6. The optical sensors 4, 5.6 generate currents 1, I, and I according to the intensities of the red, green, and blue components contained in the applied light, respectively. Current 1, I.

RGB, RG, and IB are each logarithmically compressed by diodes 7, 8, and 9, and converted into voltages having temperature characteristics. The subtraction circuit 13 receives the photometric output (k T/Q) of the red component of the operational amplifier 10.
Take the difference between fI n (1/Is) and the photometric output (kT/q) fln (1°/I8) of the green component of the operational amplifier I1, and use the result as (kT/q)I n
It is output in the form of a ratio signal of the red component and the green component called (I R / I c ). Here, 18 is the reverse saturation current of the diode, k is Boltzmann's constant, T is the absolute temperature, and q
is the charge of the electron. Similarly, the subtraction circuit 14 calculates the blue component photometric output (kT/q)lln (I
R/I8) and the photometric output of the green component of the operational amplifier 11 (k
T/q) fIn (1°/I8) is calculated, and the result is output in the form of a ratio signal of the blue component and the green component called (kT/q) fin (IB/Io).

Subtraction circuit 13. The output of the subtraction circuit 14 is proportional to the absolute temperature T as described above, and is subjected to temperature compensation by the temperature compensation circuits 20 and 21. Since the output of the subtraction circuits 13 and 14 is a logarithmically compressed signal with a small level, it must be amplified by the level gain adjustment circuits 22 and 23. In this case, the deviation of the DC level from the reference value is also amplified. It will be done.

Therefore, a desired dynamic range can be obtained by adjusting the DC level and adjusting the gain in conjunction. Level gain adjustment circuits 22 and 23 perform this DC level adjustment and gain adjustment. The DC level and gain adjusted ratio signal is output to the R/G output terminal 24. The signal is output to the B/G output terminal 25, and the white balance is adjusted using this output.

[Problem to be solved by the invention]

The conventional white balance adjustment device is configured as described above, and since the outputs of the subtraction circuits 13 and 14 are logarithmically compressed signals with low levels, they must be amplified by the level gain adjustment circuits 22 and 23. In this case, the deviation of the DC level from the reference value is also amplified.

Therefore, the adjustment of the volume must be performed in an analog manner in conjunction with the adjustment of the DC level and the adjustment of the gain, which poses a problem in that it is difficult to obtain a desired dynamic range.

This invention was made to solve the above-mentioned problems, and it is possible to eliminate the need to perform DC level adjustment and gain adjustment in conjunction with each other, and to digitally adjust only gain adjustment. An object of the present invention is to obtain a white balance adjustment device that can easily obtain a desired dynamic range.

[Means to solve the problem]

The present invention includes a plurality of photoelectric conversion/compression circuits that generate electrical signals corresponding to the intensity of a predetermined color component contained in irradiated light, which are logarithmically compressed according to predetermined compression conversion characteristics; It is connected to every two predetermined photoelectric conversion and compression circuits among the plurality of photoelectric conversion and compression circuits, and the predetermined two
a ratio signal generation circuit that outputs a ratio signal representing the ratio of the outputs of the two photoelectric conversion compression circuits; and a ratio signal generation circuit that is connected to the ratio signal generation circuit and adjusts the DC level and gain of the ratio signal provided from the ratio signal generation circuit. The present invention is applied to a white balance adjustment device equipped with a signal processing circuit.

The white balance adjustment device according to the present invention includes a signal processing circuit connected to the ratio signal generation circuit and adjusting the DC level and gain of the ratio signal given from the ratio signal generation circuit. , the signal processing circuit is configured by a plurality of expansion circuits connected in parallel to the output of the ratio signal generation circuit and having conversion characteristics opposite to the compression conversion characteristics of the photoelectric conversion and compression circuit, and the output of the plurality of expansion circuits a switch circuit that is connected to the switch circuit and selectively outputs the output of any one of the plurality of expansion circuits by switching in response to a given control signal; The apparatus further includes control signal input means for providing a control signal.

[Effect]

Since the expansion circuit according to the present invention has conversion characteristics that are opposite to the compression conversion characteristics of the photoelectric conversion and compression circuit, the DC level of the signal converted by the expansion circuit remains constant. The switch circuit is connected to the outputs of the plurality of expansion circuits and switches in response to a control signal given from the control signal human power means;
Selectively outputs the output of any one of the plurality of expansion circuits.

Therefore, there is no need to link DC level adjustment and gain adjustment in an analog manner.

〔Example〕

FIG. 1 is a block diagram showing an embodiment of a white balance adjustment circuit according to the present invention. In the figure, the difference from the conventional example shown in FIG.
39.40 was established. The output of the subtraction circuit 13 is input to the expansion circuits 15 and 36. Extension circuit 15°3
6 outputs are connected to output terminal 1 through switches 17 and 39, respectively.
8 is connected. The output of the subtraction circuit 14 is input to the expansion circuits 16 and 38. The output of the expansion circuit 16.38 is connected to the output terminal 18 via a switch 35.40. The switches 17°35, 39, and 40 are connected to the control signal input terminal 19, and are selectively turned on in response to a control signal input from the control signal input terminal 19. Expansion circuits 15, 16, 36, 38 are photoelectric conversion compression circuits 200a
, 200b, 200c compression conversion characteristics and inverse conversion characteristics,
In other words, it has the characteristic of eliminating the temperature dependence of a given signal and performing exponential conversion.

FIG. 2 is a circuit diagram showing an example of the configuration of the expansion circuits 15, 16, 36, 38. The operational amplifier 27 has a terminal connected to the input terminal 26, and a diode 28 between the output and the terminal.
is connected. Constant current source 30 is connected to the anode of diode 28. The operational amplifier 33 is grounded, and the input is connected to the operational amplifier 27 via the diode 29.
The output is connected to the output terminal 34 and fed back to the output terminal 34 via the resistor 31.

Next, the operation will be explained. The operation until the output of the subtraction circuits 13 and 14 is obtained is the same as the conventional one. Subtraction circuit 1
3 output (k T / q ) J! n (IR/
I, ) is expanded by an expansion circuit 15.36 to become a signal Ax (16/IR) which has no temperature dependence and has been exponentially converted. Output of subtraction circuit 14 (kT/q)lln (IB/
Io) is similarly expanded by the expansion circuit 16°38, and the signal BX (I/
IB). Here, A and B are proportionality constants.

This operation will be explained using FIG. 2. From the subtraction circuit 13 to the input terminal 26, (k T/ Q ) fln (I R
/IG) is input, the voltage V1 of node v1
is the current value of the constant current source 30. Then, kT I
RIs −□Ω n−x− (1) q I c I .

becomes. Since the voltage v2 of the operational amplifier 33 is 0, the voltage difference between V2 and Vl is as follows. By the way, the current flowing through the two diodes! ,
Then, the forward voltage drop of the diode 29 is kT ID −I n□ (
3) Is becomes. From equations (2) and (3), the resistor 31 has I.

Since a current of -(1, /I)xio flows through the output terminal 34, I o x Rx (Ic / I
R) output voltage is output. Here, R is the resistance value of the resistor 31. As is clear from this equation, since an output voltage without temperature dependence can be obtained, the temperature compensation circuit 20.21
There is no need for

Expansion circuits 15.16, 36.38 are subtraction circuits 13.14
Since the output of the expansion circuit 15.16.36. is subjected to exponential conversion, the deviation in DC level is absorbed by the deviation in gain.
The DC level of the signal output from 38 is a constant value.

For example, the output of the compression circuit is (11nX+FnY), 1nX includes a DC level shift, and II n
Assuming that Y includes a gain shift, when (pnX+9nY) is exponentially converted by an expansion circuit, it becomes (x - y), and X including a DC shift is absorbed by the gain change. Therefore, the gain can be adjusted by changing (X - Y). As a result, by providing the expansion circuits 15 and 16 degrees 36.38, the level gain adjustment circuits 22 and 23 become unnecessary.

The gains of the expansion circuits 15, 16, 36, and 38 are adjusted by changing the resistance value of the resistor R for each expansion circuit, and the switches 1.
By selectively turning on 7, 35, 39, and 40, an expansion circuit with a desired gain can be selected. As a result, it is no longer necessary to perform DC level adjustment and gain adjustment in conjunction with each other as in the past, and the output terminal 18
The gain of the output signal can be changed digitally, and a desired dynamic range can be easily obtained.

In the above embodiment, the circuit shown in FIG. 2 is shown as an example of the configuration of the expansion circuit 15.16° 36 and 38, but if the expansion circuit has conversion characteristics opposite to the compression conversion characteristics of the compression circuit 200a etc. Any configuration may be used.

Further, in the above embodiment, the case where two subtraction circuits are provided has been described, but the same effect can be obtained even if only one subtraction circuit is provided. Further, in the above embodiment, the output of the expansion circuit 15° 16, 36, 38 was connected to the output terminal 18 via the switch 17, 35° 39, 40, but it is not necessary to connect it to the output terminal 18; 17, 35, 39, and 40, the output may be obtained as is.

Further, in the above embodiment, red filter 1. Green filter 2.
Although the case where the primary color filter of blue filter 3 is used has been described, these filters are yellow.

It can also be used as a complementary color filter for cyan and magenta, and
A primary color filter and a complementary color filter may be combined.

〔Effect of the invention〕

As described above, according to the present invention, a signal processing circuit is configured by a plurality of expansion circuits that are connected in parallel to the output of a ratio signal generation circuit and have conversion characteristics opposite to the compression conversion characteristics of the photoelectric conversion compression circuit. a switch circuit that is connected to the output of the expansion circuit and selectively outputs the output of any one of the plurality of expansion circuits by switching in response to a given control signal; Since the apparatus further includes a control signal manual means for supplying a control signal, the signal converted by the expansion circuit has a constant DC level, and it is not necessary to perform DC level adjustment and gain adjustment in conjunction with each other as in the conventional method. Therefore, the gain of the output signal can be changed digitally. As a result, there is an effect that a desired dynamic range can be easily obtained.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of a white balance adjustment device according to the present invention, FIG. 2 is a circuit diagram showing an example of the configuration of an expansion circuit, and FIG. 3 is a block diagram showing a conventional white balance adjustment device. It is. In the figure, 13 and 14 are subtraction circuits, 15°16.3
6. and 38 are expansion circuits, 17, 35°, 39 and 40 are switches, 18 is an output terminal, one is a control signal input terminal,
200a, 200b and 200c are photoelectric conversion compression circuits. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (1)

[Claims] (1) a plurality of photoelectric conversion and compression circuits that generate an electrical signal corresponding to the intensity of a predetermined color component contained in the irradiated light and logarithmically compressed according to a predetermined compression conversion characteristic; a ratio signal generation circuit that is connected to every two predetermined photoelectric conversion and compression circuits of the photoelectric conversion and compression circuits and outputs a ratio signal representing a ratio of outputs of the two predetermined photoelectric conversion and compression circuits; a signal processing circuit connected to a circuit and adjusting the DC level and gain of the ratio signal provided from the ratio signal generation circuit, the white balance adjustment device comprising: a signal processing circuit connected in parallel to the output of the ratio signal generation circuit; The signal processing circuit is configured by a plurality of expansion circuits having conversion characteristics opposite to the compression conversion characteristics of the photoelectric conversion compression circuit, and is connected to the outputs of the plurality of expansion circuits and is switched according to a given control signal, A white balance further comprising: a switch circuit that selectively outputs the output of any one of the plurality of expansion circuits; and control signal input means that is connected to the switch circuit and supplies the control signal to the switch circuit. Adjustment device.