JPH067067B2 - Correction signal generator - Google Patents

Description

TECHNICAL FIELD The present invention relates to a correction signal generation device, and more particularly to a means for enabling substantially instantaneous photographing without requiring much time for proper offset setting.

Regarding the means to enable Noh.

(Prior Art) For example, as a colorimetric sensor device in an imaging device, conventionally, color temperature information is obtained by using an output ratio of an R sensor that detects an R (red) color component and a B sensor that detects a B (blue) color component. Those who get are known.

By the way, in this type of colorimetric sensor device, the brightness range of the target light source light is very wide, so the output of the above color sensor is converted into a digital signal for accurate processing over a wide level range. However, in that case, the performance of the A / D converter that is an interface to the microcomputer becomes a problem,
Due to its performance, the range of light quantity that can be processed is greatly limited, and it is difficult to use an inexpensive A / D converter that is not highly accurate.

In order to solve the above-mentioned drawbacks, the present applicant has previously filed Japanese Patent Application No.
No. 9-64969 (filed on Mar. 30, 1984), the offset of the output of each color sensor is set according to the output of the level detecting means for detecting the output level of a plurality of color sensors respectively detecting different color signals. We have proposed a colorimetric sensor device with means for adjusting.

(Problems to be Solved by the Invention) According to the colorimetric sensor device according to the above proposal, the output of each color sensor can be kept within a predetermined level range by adjusting the offset of the output of each color sensor. ,
An A / D converter with a simple structure can be used to convert into a digital signal, and there is an effect that highly accurate color temperature information can be obtained at low cost.

By the way, in the above colorimetric sensor device, in order to adjust the offset so that the output of the color sensor falls within the corresponding input range of the A / D converter, for example, the offset voltage is changed stepwise to output the color sensor. When is within a predetermined range, the output is taken and the arithmetic processing is performed. However, in that case, some time is required for color balance adjustment due to the calculation time of the microcomputer as the control and calculation means, the switching time of the photocurrent of the color sensor and the current for temperature correction, etc. May interfere with the shooting of still images.

Therefore, the present invention is based on the above-mentioned Japanese Patent Application No. 59-6496.
The invention according to No. 9 is further improved to provide a colorimetric sensor device that does not substantially take time to set an appropriate offset even when a target light source has a very wide range of brightness. The purpose of this is to enable substantially instantaneous shooting.

(Means for Solving Problems) In order to solve the above-mentioned problems, the colorimetric sensor device of the present invention uses a plurality of color sensors that detect different color signals and an offset of the output of the color sensor. Adjusting means, means for converting the offset-adjusted output into a digital signal, and means for processing the digital signal to form color temperature information, wherein the offset adjusting means comprises the color sensor. And a means for determining an offset value to be given to the output of the color sensor in a state in which the output of is reduced more than when the apparatus is operating.

(Operation) According to the correction signal generation device of the present invention, based on the above configuration, the output of the color sensor is attenuated more than when the device is operating,
The offset value for adjusting the offset of the output of the color sensor is determined in a state where the entire range of the light to be measured is within the input range of the analog / digital conversion means.

(Embodiment) A colorimetric sensor device to which the correction signal generation device of the present invention is applied will be described below with reference to the drawings. The following explanation
The overall configuration of the embodiment of the colorimetric sensor device of the present invention, the offset adjusting means in the embodiment, the output level detecting means of the color sensor, the manner of determining the offset value, and the operation order of the embodiment of the present invention are performed.

(Overall Configuration of Embodiment of Colorimetric Sensor Device of this Invention) (FIG. 1 (A)) FIG. 1 (A) shows the overall configuration of one embodiment of the colorimetric sensor device of this invention. 1 is a decoding unit, 2 is an input end to which a select signal is input from the system controller SC to the decoding unit 1, 3 is a switch unit, 4 is an R sensor for detecting red and a B sensor for detecting blue, for example. The colorimetric sensor including 5 includes a log amplifier section, 6 represents a final amplifier section, and the decoding section 1 outputs which signal from the final amplifier section 6 to the A / D converter 11 according to the select signal input to the input terminal 2. Controls whether to output. Switch part 3
Selects whether to transfer the photocurrent output from the colorimetric sensor 4 to the log amplifier unit 5 under the control of the decoding unit 1. When the photocurrent is not transferred to the log amplifier unit 5, the sensor is short-circuited to remove the excess electron hole pair. The log amplifier unit 5 is a colorimetric sensor 4
From the switch unit 3 to convert the photocurrent output to a logarithmically compressed voltage, and output the voltage. The final amplifier unit 6 outputs the output of the log amplifier unit 5 to the input level of the A / D converter 11 in the next stage. Amplify to match.

Reference numeral 7A is a reference current control unit, which adjusts the magnitude of the reference current Iref by an external resistor R ₀ , for example, and cancels the offset of the final amplifier unit 6 and the like.
A reference voltage setting unit 7B sets a reference voltage Vref for the log amplifier unit 5 and the final amplifier unit 6. A current shunting unit 8 sets a current for canceling the temperature variation of the voltage in the log amplifier unit 5. Reference numeral 9 denotes an offset unit as a signal source and an offset adjusting unit, which outputs the output Vou of the final amplifier unit 6 in order to convert the R signal and the B signal into signals in the convertible range of the A / D converter 11.
A current is formed to give an offset voltage to t. The details will be described later with reference to FIG. 1
Reference numeral 0 denotes a mode setting input terminal for controlling the offset value of the offset unit 9, which receives a mode setting signal from the system controller SC.

Reference numeral 11 is an A / D converter for converting the output of the final amplifier unit 6 into a digital signal, 1 is a memory for storing the output, and 13 is an operation as an arithmetic means for forming color temperature information based on the output of the memory 12. Circuit, memory M1,
M2 is connected.

Reference numeral 14 is a level detection circuit which is an example of a level detection means, which detects the range of the level of the output Vout of the final amplifier section 6 and outputs the detection signal to the system controller SC. The details will be described later with reference to FIG. The system controller SC controls the operation and operation timing of each part of the colorimetric sensor device as shown in the figure. For details, see FIG. 1 (C).
Will be described later with reference to.

Reference numerals 15 to 18 show an outline of an image pickup apparatus whose gain is controlled by this colorimetric sensor, and 15 is an image sensor,
Reference numerals 16 and 17 denote gain control amplifiers that relatively control the gains of the R, G, and B signals that are the respective color signals in the output of the image sensor 15. In this example, the gain control amplifiers are provided for the R and B signals, respectively. The gain is controlled by the output of the circuit 13, and the level of each color signal is adjusted according to the color temperature of the subject. A process encoder 18 is a standard television signal based on the R, G and B signals,
For example, it forms an NTSC signal.

Reference numeral 19 is a pin for taking in a control signal from the system controller SC to the final amplifier section 6, and the above-mentioned control signal lowers the gain of the final amplifier section 6 when the offset value is determined, as described later. . Reference numeral 20 denotes an AE sensor provided as a deforming means for determining an offset value, and the system controller SC is provided according to the output of the AE sensor.
The offset value is determined in.

Next, the operation of the colorimetric sensor device of FIG. 1 (A) will be described. The photocurrent generated by the color measurement sensor 4 including the R sensor and the B sensor is selectively sent to the log amplifier unit 5 or short-circuited by the decoding unit 1 and the switch unit 3. The photocurrent sent to the log amplifier unit 5 is converted into a voltage, logarithmically compressed, amplified by the final amplifier unit 6, and output. The above flow is set to the signal acquisition mode. Further, under the control of the decoding unit 1, no current is sent from the colorimetric sensor 4 to the log amplifier unit 5, but a constant current described below is flown from the current shunt unit 8 to the log amplifier unit 5, and output from the final amplifier unit 6 in the same manner as above. To do. Since the ambient temperature is measured by this, the above flow is set to the temperature measurement mode.
That is, when a (0, 0) signal is sent from the system controller SC to each of the input terminals A and B of the select signal input terminal 2, the output of the B sensor is output from the final amplifier section 6 via the log amplifier section 5, ( The output of the R sensor is sent when the (0,1) signal is sent, the output current i ₁ of the current shunt unit 8 is sent when the (1,0) signal is sent, and the current shunt unit 8 is sent when the (1,1) signal is sent. The output current 16i _{1 of} is similarly output from the final amplifier section. Therefore, the output of each sensor and the current shunting unit 8 as the constant current source is subjected to the time-division processing, so that the circuit configuration can be simplified.

In this way, according to the select signal from the system controller SC, the outputs of the R sensor, the B sensor, and the current shunt unit 8 are time-sequentially passed through the log amplifier unit 5 and the final amplifier unit 6, respectively, and then by the A / D converter 11. It is A / D converted and supplied to the memory 12, where the R sensor and B
The outputs of the sensor and the current shunt unit 8 are temporarily stored. The arithmetic circuit 13 calculates the output ratio of the R sensor and the B sensor, which is free from the influence of the temperature fluctuation, based on these stored values, and the output ratio corresponds to the color temperature one to one.

(Offset Adjusting Means in Embodiment of the Present Invention) (FIGS. 2 to 4) Next, the essential points of the offset adjusting means in the above embodiments will be described with reference to the specification of Japanese Patent Application No. 59-64969. To do. FIG. 2 shows an example of a specific circuit configuration of the final amplifier section 6 and the offset section 9 in FIG. 1 (A). In the final amplifier section 21, 21 is a hair amplifier and its (+) input terminal. The potential of the signal voltage is Vs (Vs
+ Vref), and the potential at the other end of the resistor R ₁ connected to its (−) input end is Vref. In the offset unit 9, CM1, CM2 and CM3 are current mirror circuits, C,
D and E are input terminals that form the mode setting input terminal 10 of FIG. I ₀ is the output voltage V of the final amplifier section 6.
It is the output current of the offset unit 9 for adjusting the offset of out, and its value is the input terminal C, as described later.
It is determined by the combination of the output currents I ₁ , I ₂ and I ₃ of the respective mirror circuits controlled by the signals input to D and E. The ratio of I ₁ , I ₂ , and I ₃ is approximately 4:
The ratio is set to 2: 1, which will be described in detail later. Further, I ₂ is set to I ₂ = I _c with _respect to the constant current I _c .

Here, a mode of adjusting the offset of the final amplifier unit 6 will be described. In FIG. 2, the current Is flowing through the resistor R ₁ is given by Is = (Vs + Vref−Vref) / R ₁ = Vs / R ₁ , while Is is the current flowing through the resistor R ₂ and is Is ′. since = represented by is _{'-I 0} becomes _{is' = Vs / R 1 +} I 0. Accordingly, the output voltage Vout is expressed by _{Vout = Vs + Vref + (Vs} / R 1 + I 0) · R 2 = Vs · (R 1 + R 2) / R 1 + Vref + I 0 R 2 ··· (1).

Therefore, by changing the magnitude of I ₀ , Vou
The offset of t can be adjusted. For example, as shown in FIG. 3, when I ₀ R ₂ = 0, EV5 to EV1
Although it can handle only the light amount up to 0, it can handle the light amount of EV2.5 to EV7.5 when I ₀ · R ₂ = 1.5V and the light amount of EV _{0 to} EV 5 when I ₀ · R ₂ = 3V. That is, EV0 to EV0 by adding the offset I ₀ · R ₂
The light quantity up to EV10 can be handled. Therefore, I ₁ , I ₂ , and I ₃ are set as described above, and the output current I ₀ and the offset voltage are shown in Table 1 depending on the combination of 1 or 0 signals input to the input terminals C to E of FIG. It changes as shown.

Here, in order to form the color temperature information in the apparatus of FIGS. 1 (A) and 2, the R sensor and B are set as Vs of the equation (1).
It suffices to read the output signal of the sensor and obtain the ratio, but since the above-mentioned sensor offset adjustment is performed, it is necessary that both types of signals are in the same mode. For example, it causes an error. That is, when the offset is not provided with redundancy as shown in FIG. 4 (a), assuming that the above two types of signals are R and B, R and B are in the same mode as shown by 22 in FIG. When it is in the upper mode, as in 23 in the figure, R is in the upper mode, and when B is in the lower mode, the ratio of R and B is in this state. Even if is calculated, a completely incorrect result will be calculated.

Therefore, in this device, this defect is prevented by providing an overlapping portion between the modes as shown in FIG. However, this overlapping portion is set to be larger than the difference between R and B. In this way, for example,
In (a), R enters the mode, but even if B is lower than the lower limit, if the mode in (b) is entered, both R and B will enter this mode.

The mode of determining the offset value in the embodiment of the present invention will be described later with reference to FIG. 1 (B). If the mode in which the output of the R sensor is input is found by the mode described later, is the output of the B sensor input? Find out. If the output of the B sensor is also in that mode, a code signal is input from the system controller SC to the mode setting input terminal 10 to give an offset corresponding to that mode, and a predetermined offset is given. The R sensor output, the B sensor output, and the output of the current shunt unit 8 are sequentially processed under the control of the select signal, A / D converted, and then stored in the memory 12, and then these are arithmetically processed to form color temperature information. . Here, the current mirror circuits CM1 to CM
If the current values of the outputs I _{1 to} I ₃ of M3 have an error, the offset voltage includes an error corresponding to that, and it becomes impossible to cover the target range of light brightness. The difference between R and B is EV 0.5 stage.

Two problems arise in this case. The first is that a sufficient margin must be taken against the error so that the lower limit (mode) can cover the target range of light brightness. For example, the currents I _{1 to} I ₃ are ± 10
If Ic = 100 μA assuming that an error of 100% is given, I ₂ = 200 μA → 220 to 180 μA I ₂ = 100 μA → 110 to 90 μA I ₃ = 50 μA → 55 to 45 μA

When the maximum error is generated in the mode, what should be 350 μA becomes 385 μA or 315 μA. In this case, the problem is 315 μA, but this problem can be dealt with by determining the lower limit EV value of the mode by looking at the error voltage obtained by multiplying the error component 35 μA by R ₂ .
If the error voltage is 1 V, it corresponds to one EV stage. Therefore, if the lower limit of the mode is EV1, then EV2 can be guaranteed.

The second problem occurs in the following cases. That is,
In FIG. 4B, it is assumed that R is in the mode but B is smaller than the lower limit of the mode. In this case, jump to the mode, and in the mode, both R and B should enter due to the provision of overlap, but at this time, due to an error, the mode becomes too high by 0.5V and the mode becomes low by 0.5V. If that happens, the overlap will disappear. In other words, even if the error is subtracted, if the overlapping part is not larger than the difference between R and B,
There will be a problem that R and B are not covered in the same mode.

To deal with this problem, a constant current I for offset setting is used.
_{When 1 to} I ₃ are set at equal intervals, even if the error is taken into consideration, the maximum error among the modes may vary, and a very large maximum error may occur. There is. Therefore, the overlap between the respective modes must be taken extra, and as a result, the configuration of the constant current source for forming I ₀ and its control are complicated.

Therefore, in this embodiment, the output of each reference signal source is set so that the above errors are averaged in order to reduce this error.

This can be theoretically explained as follows. That is, in order to minimize the conversion error to the adjacent mode, the ratio of the output current of each signal source is set to 1 instead of 1: 2: 4 :.
+ Α: 2 + β: 4 + γ: ..., I ₁ = x ₁ , I ₂ = x ₂ , I ₃ = x ₃ x ₁ = 4x−z x ₂ = 2x + (z−z ′) x ₃ = 2x + z ′ x ₁ + x ₂ + x ₃ = 7x is set so that the value considering the error in each mode approaches the specified value. Assuming that x has an error of ± y%, the above formula is x ₁ ′ = (4x−z) (1 ± y) x ₂ ′ = (2x + z−z ′) (1 ± y) x ₃ ′. = (X + z ') (1 ± y), and the difference from the adjacent mode is (x + z') (1 + y) = x + xy + z '+ z'y (2) (mode, interval) (2x + z-z ′) (1 + y) − (x + z ′) · (1−y) = x + 3xy + z−
2z '+ zy ... (3) (mode, interval) (4x-z) (1 + y)-{(2x + z-z') + (x + z ')} (1-y) = x + 7xy-2z ... (4 ) (Mode, interval), and z and z ′ may be determined so that these error amounts become equal, so from equations (2) and (3), 2xy−3z ′ + z + zy−z′y = 0 ... (5) From equations (3) and (4), 4xy-3z + 2z'-zy = 0 ... (6) Equations (5) and (6) are solved for z and z '. Is obtained. For example, if x = 50 and y = 0.1, then z = 11.06, z ′ = 7.152, and from this, x ₁ = 200-11.06 = 188.94 x ₂ = 100 + (11.06-7 .152) = 103.908 × ₃ = 50 + 7.152 = 57.152, so I ₁ = 189 μA, I ₂ = 104 μA, I
₃ = 57 μA, even if each current has an error of ± 10%, I ₁ = 189 ± 10% = 207.9 to 170.1 I ₂ = 104 ± 10% = 114.4 to 93.6 I ₃ = 57 ± 10% = 62.7 to 51.3 Within each μA range, the difference between modes is as shown in Table 2 even in the worst case, and the maximum error is between modes, between and between modes. Become 1 Significantly reduced.

(Output Level Detection Means of Color Sensor in Embodiment of the Present Invention) (FIG. 5) FIG. 5 shows the output level of the final amplifier section 6 input to the A / D converter 11 of FIG. The details of the level detection circuit 14 for detecting the output level of the color sensor of the color measurement sensor 4 are shown. Reference numerals 31 and 32 in the figure are comparators, and the output of the final amplifier section 6 is input to the A / D converter 11. And the (−) input terminal of the comparator 31 and the comparator 32.
Is input to the (+) input terminal of. The (+) input end of the comparator 31 and the (−) input end of the comparator 32 have a reference potential source V corresponding to the upper and lower limits convertible by the A / D converter 11.
_H and V _L , respectively. The outputs of the comparators 31 and 32 are input to the AND gate 33, and the AND gate 3
3 and the output of the comparator 31 are input to the NOR gate 34,
The outputs of the AND gate 33 and the comparator 32 are NOR gates 3.
5 is input to AND gate 33 and NOR gate 3
The outputs of 4, 35 are input to the system controller SC.

Therefore, if the output of the final amplifier unit 6 is within the convertible range of the A / D converter 11, the comparators 31, 32
Both of the outputs go high, and the output of the AND gate 33 also goes high. On the contrary, the output of the final amplifier 6 is A /
If the level is higher than the convertible upper limit of the D converter 11, the comparator 31, the comparator 32, and the AND gate 33.
Output becomes low, high and low respectively, and the high output is supplied only from the NOR gate 34 to the system controller SC. If the output of the final amplifier unit 6 is lower than the lower limit of conversion of the A / D converter 11, the high output is similarly supplied from the NOR gate 35 to the system controller SC. As a result, it is determined whether the output of the final amplifier unit 6 is within the level range that can be converted by the A / D converter 11, or is higher or lower than this range.

As a modification of the above, as indicated by the broken line in FIG.
The output of the / D converter 11 may be input to the system controller SC and the system controller SC itself may detect the level of the color sensor output. In this case, the level detection circuit 14 in the figure can be omitted.

(Aspect of Offset Value Determination in Embodiment of this Invention)
(FIG. 1 (B)) By adjusting the offset of the output of the color sensor by the means described above, the output of each color sensor can be kept within a predetermined level range, and an A / D converter having a simple structure is used. Can obtain accurate color temperature information,
For that purpose, as described above, for example, when the offset voltage is changed stepwise and the output of the color sensor falls within a predetermined range, the output is taken in and arithmetic processing is performed. Since it takes some time to make a decision, it is not suitable for instant photography.

Therefore, in the embodiment of the present invention, when the offset value is determined, the gain of the final amplifier unit 6 is lowered and the output of the color sensor is attenuated more than when the apparatus is operating, so that the total range of the light to be measured is reduced. The input range of the A / D converter 11 is set. For example, when the gain of the final amplifier unit 6 is high, only the range of EV15 to EV18 was included in the input range of the A / D converter 11, but by lowering the gain, the input range of EV3 to EV18 can be achieved. it can. Then, in this state, the output signal of the color sensor is arithmetically processed to determine the offset value, and after the determination, the output of the color sensor is returned to the required level by means such as returning the gain of the final amplifier unit 6 to the original value. To perform color measurement operation.

Hereinafter, a specific mode of determining the offset value will be described with reference to FIG. First, the final amplifier section 6
To a predetermined small value (step 20).
1). Next, the select signal input is set to (0, 1) to select the R reading mode, and the offset mode is set to an appropriate mode in consideration of the gain and offset current of the final amplifier section 6 (step 202), and the R sensor The output data is input to the log amplifier unit 5 via the switch unit 3 (step 203). As described above, since the data taken in with the gain of the final amplifier unit 6 lowered falls within the input range of the A / D converter 11, for example, the reference for which this data is set by the level detection circuit 14 is used. Level A ~
It is determined whether or not it is larger than G (levels are in alphabetical order) (steps 204, 20).
5, ..., 206), and one of the modes is set based on the determination result (steps 207, 208, ..., 209, 210). When the offset mode is set, the gain of the final amplifier section 6 is returned to the original value (step 211), and then the process proceeds to step 102 of FIG. 1 (C).

(Operation of Embodiment of the Present Invention) (FIG. 1) Next, in the embodiment of FIG. 1 (A), the photocurrent of the colorimetric sensor 4 and the current for temperature correction output from the current shunt unit 8 are supplied. The overall operation up to importing and forming color temperature information will be described with reference to FIG. First, in step 102 following step 211 in FIG. 9B, the input signal (R data) is taken in. Next, the level detection circuit 14 or the like determines whether the level of the input signal is higher than the range in which A / D conversion is possible (step 103) or lower than this range (step 104), and the data is M
If ax>data> Min, the process proceeds to step 105.

In step 105, it is determined whether the select signal input is (0, 1). In this case, since it is YES, the process proceeds to step 106, and the data (R data in this case) is stored in the memory 12.

Next, the select signal input is set to (0,0). Thus, the B mode for reading the output of the B sensor is set, and the process returns to step 102 (step 107). This time, the output of the B sensor is taken in via the switch unit 3, and if Max>Data> Min as described above, the process proceeds to step 105 (steps 102 to 104).

In step 105, it is determined whether or not the select signal input is (0, 1). In this case, since it is (0, 0), the process proceeds to step 108 and the select signal input is (0, 1).
0), and if yes, step 10
9, the B data is stored in the memory 12 via the A / D converter 11.

Next, the select signal input is set to (1, 0), and the constant current i ₁
It is set to a mode for reading the information such as "step" (step 110). Here, in step 111, constant currents i ₁ and 16i ₁
Input a mode setting signal to the input terminal 10 so as to set an offset value that can be input to the A / D converter 11, and then returns to step 102 again to take in the constant current i ₁ via the switch unit 3 and Max> i _{If 1} data> Min, the process proceeds to step 105 and steps 105 and 108.
Since both determination results of No are No, the process proceeds to step 112. In step 112, the select signal input is (1,
It is determined whether or not it is 0), and since this is YES, the process proceeds to step 113, and the i ₁ data is stored in the memory 12.

Next, the select signal input is set to (1, 1), whereby the mode for reading the constant current 16i ₁ is set (step 114), and then the process returns to step 102 to read the 16i ₁ data through the switch unit 3. , Max> 16i ₁
If data> Min, the process proceeds to step 105. Since the determination results in steps 105, 108, and 112 are all negative, the process proceeds to step 115, and 16i ₁ data is stored in the memory 12.

By the above operation, the R, B, I ₁ and 16i ₁ data are once stored in the memory 12, and the ratio of the output of the R sensor and the output of the B sensor is calculated by removing the influence of temperature fluctuation from these data. That is, in the arithmetic circuit 14, (logR-lo
gB) is calculated (step 116), and the color temperature information is introduced based on the value of logR-logB = logR / B (step 11).
7) Then, the gains of the gain control amplifiers 16 and 17 are controlled to adjust the level of each color signal according to the color temperature of the subject (step 118).

As described above with reference to FIG. 1B, in step 201, the entire range of the light whose color is to be measured by reducing the gain of the final amplifier unit 6 falls within the input range of the A / D converter 11. Since the offset mode is set in this state, the result of the determination of the fetched data in steps 103 and 104 of FIG. 1 (C) should be no. If the determination is made, the device of FIG. 1 (A) operates as follows. In other words, if YES in step 103, the R sensor or B sensor is exceptionally set even if the mode is set.
This is the case where the output data of the sensor is so small that it does not fall within the input range of the A / D converter 11 and the color temperature is extremely low. In this case, the specific value stored in the memory M1 in step 119 The temperature information is output to prevent colorimetry from being impossible, and it is possible to take a substantially instantaneous image without adjusting the color balance.
Similarly, if YES in step 104,
Exceptionally, even if the mode is set, the output of the sensor is so large that it does not fall within the input range of the A / D converter 11, and it is determined that the color temperature is extremely high. In this case, in step 120 The specific value stored in the memory M2 is output as color temperature information.

As described above, the system controller SC may determine the offset value according to the output of the AE sensor 20 of FIG. This invention also
In addition to using R, B two-color filters, R, G, B
When using three color filters (logR-log
By determining the value of B) and performing the same operation as described above, the same effect can be obtained.

(Effect of the Invention) As described above, according to the correction signal generation device of the present invention,
Since the means for determining the offset value to be given to the output of the color sensor when the output level of the color sensor is attenuated compared to the operation of the device is provided, in the normal color measurement operation, the The offset value can be determined in a state in which the entire range is within the input range of the analog / digital conversion means, and it is possible to perform substantially instantaneous shooting without substantially taking time to set an appropriate offset.

[Brief description of drawings]

FIG. 1 (A) is a block diagram showing the overall configuration of an embodiment of the colorimetric sensor device of the present invention, and FIG. 1 (B) is a flow chart for explaining the mode of offset value determination in the embodiment of FIG. FIG. 2C is a flow chart for explaining the operation of the embodiment of FIG. 2A, FIG. 2 is a circuit diagram showing an example of the final amplifier section and offset section in FIG. 1A, and FIG. Is an explanatory view showing the principle of offset adjustment in the embodiment of the present invention.
FIG. 6A is an explanatory diagram showing a comparative example of the offset adjustment method,
5B is an explanatory diagram showing an example of the offset adjusting method in the embodiment of the present invention, and FIG. 5 is a circuit diagram showing an example of the level detection circuit in the embodiment of FIG. 1A. Explanation of Codes 1: Decode section, 2: Select input terminal, 3: Switch section, 4: Colorimetric sensor, 5: Log amplifier section, 6: Final amplifier section, 8: Current shunt section, 9: Offset section, 10: Mode setting input terminal, 11: A / D converter, 12: memory, 13: arithmetic circuit, 14: level detection circuit, 16, 1.
7: Gain control amplifier, 19: Pin for taking in control signal,
20: AE sensor, SC: system controller.

Front page continued (72) Inventor Toshio Blacksmith 770 Shimotegome, Takatsu-ku, Kawasaki, Kanagawa Canon Inc., Tamagawa Plant (72) Akihiko Tojo 770, Shimonoge, Takatsu-ku, Kawasaki, Kanagawa Prefecture

Claims (1)

[Claims] 1. A photoelectric conversion means for photoelectrically converting imaging light from a subject, an amplifier means for level control of an output signal of the photoelectric conversion means, and an offset adjustment of an output signal of the amplifier means. Offset control means, correction signal generation means for generating a correction signal based on the output signal adjusted by the offset adjustment means, and control means for variably setting the gain in the amplifier means, wherein the control means is A correction signal generation device, characterized in that the gain in the amplifier means during the offset adjustment in the offset adjustment means is set smaller than the gain other than during the offset adjustment.