JPH0475451B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a non-linear conversion device used, for example, to detect color temperature information.

(Prior Art) Conventionally, as a circuit for detecting color temperature information of an object, a circuit as shown in FIG. 1 is known.

That is, R sensor 1 and B detecting the R (red) component.
A B sensor 2 that detects the (blue) component is installed adjacently, and the respective detection outputs are amplified by amplifiers 3 and 5, and logarithmically compressed by diodes 4 and 6, respectively, to suppress the dynamic range. The signal and the B signal are obtained from the outputs of amplifiers 3 and 5, and this is connected to the resistor.
A configuration is known in which the signal is led to a subtracter consisting of R1 to R4 and an amplifier 7, and the ratio of the two is obtained as a result.

Then, the color temperature value is displayed by reading out the color temperature information determined according to the ratio of the R signal and the B signal from the ROM, etc., and the predetermined gain control signal is output from the ROM etc. according to the ratio of the R signal and the B signal. There is known a device that controls the gain of each color of a color imaging device using this control signal.

This takes advantage of the fact that the ratio of the R signal and the B signal corresponds to the color temperature as a monovalent function.

However, in such a conventional color temperature detection device, two logarithmic compression circuits consisting of amplifiers 3 and 5 and diodes 4 and 6 are used, so the configuration is complicated and the temperature characteristics of the diodes 4 and 6 are Since they are not necessarily the same, errors tend to occur in the output obtained via amplifier 7, and in order to correct this error, it is necessary to connect a correction circuit to the outputs of amplifiers 3 and 5, respectively, and the correction The problem was that it was difficult to even do so.

(Objective) It is an object of the present invention to provide a non-linear conversion device that can eliminate the drawbacks of the prior art.

Another object of the present invention is to provide a nonlinear conversion device that can correct temperature characteristics with a simple configuration.

(Example) The present invention will be explained below based on examples.

FIG. 2 is a diagram illustrating an embodiment of the detection unit 100 constituting the non-linear conversion device of the present invention, and 1 in the figure indicates R.
A light receiving diode (2) serves as an R light detection means for detecting (red) light, a light receiving diode (2) serves as a B light detection means for detecting B (blue) light, and (8) serves as a G light detection means for detecting G (green) light. light-receiving diodes, and the light that each diode can detect is limited by a color filter or similar layer. or,
Each diode forms a photoelectric conversion means for photoelectrically converting incident light. 9 to 16 are switch circuits, especially switch circuits 9 to 11 and 15,1.
6 forms a switching means.

Also, 9c to 11c are switch circuits 9 to 11.
These terminals are connected to control inputs for controlling ON-OFF, respectively, and signals from terminals 9c to 11c are connected to control inputs for controlling ON-OFF of switch circuits 12 to 14 via inverters IN1 to IN3. are connected to each other.

Further, 15c and 16c are switch circuits 15 and 16c, respectively.
Terminals 9c to 11c, 15c, and 16 are connected to control inputs for ON-OFF control.
The outputs of interface circuits, which will be described later, are applied to the respective terminals 16c.

A logarithmic compression diode 17 serves as a nonlinear conversion means, and together with the amplifier 20 constitutes a logarithmic compression circuit.

The output of the amplifier 20 is a diode 18 for compensating the temperature characteristics of the reverse saturation current of the diode 17.
The cathode of the diode 18 is connected to the non-inverting input of the non-inverting amplifier 21 .

The gain of the amplifier 21 is fixed by resistors 22 and 23, and can be built into the IC.

43 is a reference voltage source, and buffer amplifier 24
via amplifiers 20, 21, diodes 1, 2,
The reference voltage is supplied to 8.

Also, 19 is a diode, 41 is a resistor, 25 to 3
Reference numeral 9 denotes a transistor, which constitutes a constant current source. Of these, transistor 30 constitutes a first constant current source, and transistors 25 to 2
9, transistors 33 to 36, etc. constitute a second constant current source. Here, the supply current of the second constant current source is 16 for the supply current of the first constant current source i ₁
The relationship is set to i ₁ .

Further, 40 is an adjustment resistor for adjusting _i1 .

Next, FIG. 3 is a diagram showing the configuration of the signal processing section 200 and the imaging device 300 connected to the output terminal 42 shown in FIG. 2, which together with the detection section shown in FIG. 2 constitute a color information detection device. In the figure, 44 is an A/D converter that converts the output of the amplifier 21 into a digital signal. 45 is an input/output interface circuit, 46
47 is an arithmetic/control circuit as an arithmetic means;
ROM circuits 48 and 49 are D/A converters, which form gain control signals V _R and V _B , respectively, which will be described later. Also, SWC is a switch for operating the color information detection device.

Reference numeral 50 denotes an image sensor as an imaging means such as a solid-state imaging device, and a color stripe filter 64 as shown in the fourth figure is provided on its light receiving surface.

Reference numeral 51 is a low-pass filter for cutting out the high frequency side color signal component modulated by this filter 64 to obtain a pseudo luminance signal. Sample and hold circuits 52 to 54 sample and hold the R component signal, G component signal, and B component signal modulated by the filter 64, respectively; 55 to 57;
is a low-pass filter that cuts out high-frequency components of color signals.

Process circuits 58 to 61 perform various corrections such as black level clamp gamma correction, contour correction, and white clipping on the luminance signal, R component signal, G component signal, and B component signal, respectively.

Incidentally, the process circuits 59 and 61 are both configured to be able to control their gains, and the gain control signals which are the outputs of the D/A converters 48 and 49
The gains are controlled by V _R and V _B , respectively.

62 is a matrix circuit which outputs a pseudo luminance signal S _Y
A color difference signal, etc. is formed by mutually calculating the color signals S _R , S _G , and S _B . An encoder 63 applies a predetermined modulation to the output of the matrix circuit 62 to form a standard television signal or the like.

FIG. 5 is a diagram showing an example of the configuration of the arithmetic control circuit 46, in which ORE is an output register and CNT is a ring counter.
This configuration is such that the "1" level is sequentially shifted to the two output terminals from the left side in the figure. Also, C is the carry out terminal and R is the reset terminal for the counter.
The first digit (LSB) of CNT is "1" and the other digits are "0". That is, the output of counter CNT is set to (00001). Furthermore, the first value of this counter CNT
The outputs of the digit (LSB) to the fifth digit (MSB) are sent to terminals 9c to 11c, 1 via the interface circuit 45.
5c and 16c.

REG is the first register and counter CNT
A/D converter 44 is located at the address corresponding to the output of
The A/D converter 44 is used to input and store the output of the
It forms a synchronization means for synchronizing the sequential outputs of at a predetermined timing. Also, OPC is an arithmetic circuit,
The CPU is a control unit, and this control unit CPU is ROM4
Input/output to 7, input/output to arithmetic circuit OPC, 1st
Input/output to the register REG, output to the output register ORE, output to the counter CNT, input of signals from the switch SWC via the interface circuit 45, etc. are controlled as shown in the flowchart of FIG.

The operation of the color information detection device will be explained below using this flowchart.

When a power switch (not shown) is turned on, the arithmetic/control circuit 46 and the like start operating, and the program starts (step). Next, it is determined whether the switch SWC for operating the color information detection device is turned on (step). If it is off, repeat this step.

If the SWC is on, the process advances to step 5, where the counter CNT in the arithmetic/control circuit 46 is reset, and the output from the output terminal of this counter CNT is changed to the fifth output terminal.
From the digit (MSB) to the first digit (LSB) is (00001).

As a result, the second illustrated switches 9, 13, 14 are activated.
ON, 10 to 12, 15, and 16 are OFF, and the photocurrent of diode 1 is input to the inverting input terminal of amplifier 20, and the outputs of diodes 2 and 8 are shot. The output of the constant current source is also cut off. The output of diodes 2 and 8 is proportional to the amount of incident light of each color.
If these are respectively I _SR , I _SB , and I _SG , then the current in these is
I _SR is input to amplifier 20 , and current I _SR flows through diode 17 to the output of amplifier 20 .

At this time, the forward voltage of diode 17 (V _F )
-The current (I _F ) characteristics are given by the following equation.

I _F = I _FO {exp(qV _F /nkT)−1} (1) where I _FO : Constant with temperature dependence q: Electron charge k: Boltzmann constant T: Absolute temperature (〓) n: Coefficient By the way Since it is usually used within the range of exp(qV _F /nkT)≫1, equation (1) is approximated by the following equation (2). That is, I _F = I _FO exp (qV _F /nkT) (2) Therefore, V _F = (nkT/q) (lnI _F −lnI _FO ) (3) In this way, the output V _F of the amplifier 20 is connected to the photodetector diode. The currents flowing from 1, 2, and 8 are obtained by logarithmically compressing them.

Here, since the photocurrent I _R of the diode 1 flows, the output voltage V _RF of the amplifier 20 at that time is V _RF = (nkT/q) (lnI _R − lnI _FO ) (4), and this voltage V _RF Through this, V _RF ′=(bkT/q) (lnI _R −lnI _FO ) (5) (where b is a constant). This V _RF ' is sent to an arithmetic control circuit 46 via an A/D converter 44 and an interface circuit 45.
be guided by

Next, in step A/
The output of the D converter 44 is input via an interface circuit and stored.

That is, this step stores the digital value of the voltage V _RF ' in the register REG. Note that the addresses of register REG (a ₁ , a ₂ , a ₃ , a ₄ ,
a ₅ ) is stored in REG (a ₁ , a ₂ , a ₃ , a ₄ ,
a ₅ ).

In the next step, the "1" of the counter CNT is shifted by one bit by applying a clock to the CNT. This allows the counter CNT
The output becomes (00010) and switches 9 to 16 are controlled via the interface circuit.

In other words, 10, 12, 14 become ON and 9, 11,
13, 15, and 16 are turned off. Therefore, the output current of the diode 2 is input to the amplifier 20, and further via the amplifier 21, the output V _BF '=(bkT/q) (lnI _B −lnI _FO ) (6) is obtained.

This output is input to an arithmetic control circuit 46 via an A/D converter 44 and an interface circuit 45.

Next, in the step, it is determined whether or not 1 is output from the carry-out terminal, and since it is not output at this stage, the process returns to the step, and this time, the digital value of the voltage V _BF ' is stored in address (00010) of the register REG. As a result, V _RF ′ and V _RF ′ obtained in time series are made simultaneous.

Next, as described above, shift CNT by 1 bit and output (00100) to turn on switches 11 to 13, 9, 10, 15, 16.
is turned off to obtain V _GF ′=(bKT/q) (lnI _G −lNI _FO ) ……(7).

Then, in this step, this digital value is stored in address (00100) of register REG. Furthermore, by shifting CNT by 1 bit and outputting (01000), switches 12 to 15 are turned on.
and turn 9 to 11 and 16 OFF.

As a result, 16i ₁ is input to the amplifier 20, V _16i1F = (nkT/q) (ln16i ₁ − lnI _FO ) ...(8) is obtained at the output of the amplifier 20, and V _16i1F is obtained at the output of the amplifier 21. ′=(bkT/q) (ln16i ₁ −lnI _FO ) ...(9) is obtained.

Then, at the next step, there is no carry out yet, so return to the step and this
V _16i1F ′ digital value of register REG (01000)
Store it in the address.

Also, shift CNT by 1 bit in step,
By outputting (10000), switch 12~
14 and 16 are turned ON, and 9 to 11 and 15 are turned OFF to obtain the output of the amplifier 21 as follows: V _i1F ′=(bkT/q) (lni ₁ −lnI _FO ) ……(10).

Then, a carry-out is detected in the step, but since there is no carry-out yet, the process returns to the step and stores the digital value of V _i1F ' at address (10000) of the register REG.

When CNT is further shifted by one bit in the step, counter CNT outputs a carry out.

Therefore, this will be detected in the next step and the process will proceed to the next step. In the step, information REG (00010) at address (00010) of the register and information REG (00001) at address (00001) are operated to obtain X=REG (00010) - REG (00001) (11). Therefore, from equations (5) and (6), we obtain X=(bkT/q) (lnI _B −lnI _R ) ...(12). In this way, in the embodiment of the present invention, since the _IFO is common, temperature correction can be easily performed. Next, in the same step, by calculating Y=REG (01000) − REG (10000), from equations (9) and (10), Y=(bkT/q)(ln16i ₁ −lni ₁ ) =(bkT/ q) Obtain ln16 (13). Since I _FO is common here as well, errors due to variations in elements due to non-linear exchange do not occur.

Then in the step Z=(X/Y)lnN (14) Calculate.

Here, N represents the ratio of the output current of the second constant current source to the output current of the first constant current source, and in this embodiment, N=16i ₁ /i ₁ =16.

Therefore, Z=lnI _B −lnI _R =lnI _B /I _R (15) is obtained. This corresponds to the logarithmic value of the current ratio of the light receiving diodes 1 and 2. As described above, according to the present invention, temperature-corrected color information can be detected with a simple configuration.

Next, in step, the data M _R (Z) and M _B (Z) stored in the address corresponding to the value Z in the ROM 47 are read out. This data is, for example, the first few bits of the data stored at address Z in the ROM47.
M _R (Z) and the last few bits are read as M _B (Z). And this read M _R (Z), M _B
(Z) in the output register ORE in the next step.
Set to .

After that, return to the step again and set the switch SWC.
ON-OFF is detected, and if it is ON, the above cycle is repeated again.

Note that after the output register ORE is set by the step, it holds its output state until the step is performed again.

Further, the outputs M _R (Z) and M _B (Z) of the register ORE are input to D/A converters 48 and 49, respectively, and control the gains of the process circuits 59 and 61 as gain control signals V _R and V _B. . Here, the gain ratio of the process circuits 59, 60, 61 changes according to a predetermined correlation depending on the output ratio of the light receiving diodes 1, 2. That is, as I _R /I _B becomes larger, the gain of the process circuit 59 is controlled to be smaller than the gain of the process circuit 60.

In the above embodiments, a diode was used as the photoelectric conversion means, but the photoelectric conversion means is not limited to a diode, but may be a transistor, CdS, or the like.

Further, in the embodiment, a diode is used as a conversion means for performing non-linear conversion, but a transistor or the like may also be used.

Further, in the embodiment, the first register is used as the synchronization means, but if the analog signal is processed as it is, a sample-and-hold circuit may be used. Moreover, it goes without saying that the present invention can be used not only for detecting color temperature, but also for detecting optical information and performing non-linear conversion.

Further, the conversion means for performing the non-linear transformation is not limited to one that performs logarithmic compression, but may be any one that performs a predetermined non-linear transformation. For example, the present invention is applicable even to a device that stretches non-linearly. Furthermore, I _R /I _B may be corrected using the output I _G of the G color detection means in the embodiment.

(Effects) As explained above, the non-linear conversion device of the present invention has a photoelectric conversion means that converts incident light into an electrical signal, and a characteristic that varies at a predetermined ratio depending on the environmental temperature. A signal conversion means that non-linearly converts an electrical signal obtained from the conversion means to obtain a signal conversion output including a temperature fluctuation component corresponding to the fluctuation of the environmental temperature, and a signal conversion means having the above characteristics. By arithmetic processing the conversion output of each constant current source obtained by supplying a plurality of constant current sources that differ in terms of The structure includes a correction signal generation means for generating a correction signal, and a correction means for removing the temperature fluctuation component in the signal conversion output by performing arithmetic processing on the signal conversion output and the correction signal. The temperature proportional term generated when non-linearly converting the electrical signal obtained by the converting means can be removed with high accuracy, and this can be realized with an extremely simple configuration.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the main parts of a conventional color temperature detection device, and FIG. 2 is a detection section 1 of the nonlinear conversion device of the present invention.
00, FIG. 3 is a diagram showing an example of the configuration of the signal processing unit 200 and the imaging device 300, FIG. 4 is a diagram showing an example of the configuration of the color filter, and FIG. 5 is an example of the configuration of the arithmetic/control circuit 46. Figure 6 shows the control section.
This is a program chart for the CPU. 1, 2, 3...A light receiving diode as a photoelectric conversion means, 17...A logarithmic compression diode as a conversion means, 9-16...A switch as a switching means, 46...A calculation/control circuit as a calculation means,
30...Transistors forming the first constant current source, 25-29, 33-36...Transistors forming the second constant current source.

Claims (1)

[Scope of Claims] 1. A photoelectric conversion means that converts incident light into an electrical signal, and has a characteristic that varies at a predetermined ratio depending on the environmental temperature, and non-linearly converts the electrical signal obtained from the photoelectric conversion means. A plurality of substantially different constant current sources are supplied to the signal conversion means for obtaining a signal conversion output including a temperature fluctuation component corresponding to the above-mentioned environmental temperature fluctuation, and the signal conversion means having the above-mentioned characteristics. By processing the conversion output of each constant current source obtained,
a correction signal generating means for generating a correction signal having a temperature fluctuation component that fluctuates at approximately the same rate as the temperature fluctuation component; and a signal conversion output by performing arithmetic processing on the signal conversion output and the correction signal. A non-linear conversion device comprising: a correction means for removing the temperature fluctuation component.