JPH06350930A - Dark state output correction device for image sensor - Google Patents

Abstract

PURPOSE:To attain excellent correction without re-acquisition of correction data even when ambient temperature is changed. CONSTITUTION:The dark state output correction device for an image sensor correcting a dark state output of the image sensor is provided with a multiplier gain decision device 8 deciding a multiplier gain by feature quantities of a correction data outputted from a temperature sensor and a picture output of the image sensor, a multiplier 9 multiplying a multiplication gain decided by the multiplier gain decision device 8 with the result of subtracting a correction data average value from the correction data, and an adder 10 adding the multiplication result of the multiplier 9 and a mean value of the picture outputs of the image sensor. Thus, prior to subtraction of dark state output correction data from the input picture data, the multiplier 9 is used to multiply them and the result of addition by the adder 10 is subtracted from the picture output of the image sensor, then dark state output correction in response to ambient temperature change is executed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dark output correction device for an image sensor, and more particularly to a dark output correction device that is advantageously applied to, for example, an infrared image sensor and the like, and performs correction in accordance with changes in ambient temperature.

[0002]

2. Description of the Related Art In an image sensor such as a solid-state image sensor, the image output of the image sensor fluctuates greatly depending on temperature,
As it is, image unevenness occurs. Therefore, the output correction in the dark is performed so that a high-quality image signal without image unevenness can be obtained.

FIG. 2 shows a technique for performing dark output correction by storing fixed pattern noise in dark as correction data. In this conventional technique, the video signal from the image sensor is converted into a digital signal by the A / D converter 1 and then sent to the subtractor 22. Then, the subtractor 22 subtracts it from the correction data stored in the memory 21, and the adder 23 adds the offset component and outputs it as an image signal. As described above, in the conventional technique shown in FIG. 2, the dark output correction is performed by the fixed correction data set in advance.

Further, FIG. 3 shows a LUT (Look Up Tab) instead of a memory so as to adapt to changes in ambient temperature.
le) is a conventional technique, for example, Japanese Patent Application Laid-Open No. 64-64-
It is disclosed in Japanese Patent Publication No. 24564. In this prior art, the output from the temperature sensor is converted into a digital signal by the A / D converter 32, and the LUT 33 is referred to from this temperature data so that the correction data corresponding to the ambient temperature change can be selected. Therefore, the A / D converter 1
The video signal converted into the digital signal by the subtractor 2
The correction data corresponding to the temperature change is subtracted by 2 and the offset component is added by the adder 23 and output as an image signal.

[0005]

However, in the prior art shown in FIG. 2, since the correction data is fixed, it is not possible to deal with the change in the dark output due to the change in the ambient temperature. There was a problem that it was necessary to re-acquire correction data. On the other hand, in the conventional technique shown in FIG.
Since the correction data can be selected according to the ambient temperature, the correction can be performed according to the change in the dark output due to the change in the ambient temperature. However, this conventional technique has a problem that it is not possible to cope with a slight variation in the dark output at each time because the correction data set in the LUT 33 in advance is used.

The present invention solves the drawbacks of the prior art and makes it possible to obtain the correction data corresponding to the ambient temperature change, thereby making it possible to cope with the slight variations in the dark output of the image sensor. It is an object to provide an output correction device.

[0007]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides a dark output correction device for an image sensor, which corrects the dark output of an image sensor, and a correction data and an image output from a temperature sensor. Multiplying gain determining means for determining a multiplying gain according to a feature amount with the image output of the sensor, multiplying means for multiplying a result obtained by subtracting the correction data average value from the correction data by the multiplying gain determined by the multiplying determining means, and multiplying by the multiplying means It has an addition means for adding the multiplied result and the average value of the image output of the image sensor, and performs the dark output correction by subtracting the addition result added by the addition means from the image output of the image sensor.

Further, according to the present invention, an A / D for converting an analog output signal of the image sensor into a digital image signal.
A converter, a first average value calculator for calculating an average value of the image signals output from the A / D converter, a storage device for storing dark output correction data of the image sensor, and a storage device. A second average value calculator for calculating an average value of the dark output correction data, and a first characteristic amount calculator for calculating a value characterizing the ambient temperature of the image signal output from the A / D converter. A second characteristic amount calculator for calculating a value characterizing the ambient temperature of the dark output correction data stored in the storage device;
Gain calculator for inputting the feature amount from the feature amount calculator and the second feature amount calculator to calculate the multiplication gain from them, and the dark output correction data from the storage device and the second average value calculation A first subtractor for inputting the average value of the dark-time output correction data from the calculator to perform subtraction processing of these data, and a multiplication for multiplying the subtraction result of the first subtractor by the multiplication gain calculated by the gain calculator. , An adder for adding the image data average value calculated by the first average value calculator to the multiplication result of the multiplier, and an image output from the A / D converter for the addition result obtained by the adder A subtractor for subtracting from the data.

[0009]

According to the present invention, the multiplication gain is determined by using the amount that characterizes the ambient temperature, that is, the feature amount of both the temperature sensor output or the image output of the image sensor and the dark output correction data, and determines the gain. The output correction data is multiplied and the multiplication result is added to the average value of the image output. Then, by subtracting the addition result from the image output, the output change in darkness caused by the change in ambient temperature is appropriately corrected.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a dark output correction device for an image sensor according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a functional block diagram showing an embodiment in which the dark output correction device for an image sensor according to the present invention is applied to a dark output correction device for an infrared image sensor. The dark-time output correction apparatus according to the present embodiment performs the dark-time output correction due to a change in ambient temperature, and therefore outputs the correction data to the storage device 21 shown in FIG. 2 and the A / D converter shown in FIG. Instead of 32 and LUT 33, memory 2, average value calculators 3, 4, subtractor 5, feature quantity calculator 6,
7, multiplication gain calculators 8 and 9 and an adder 10 are provided.

A / D converter 1 for converting an analog image signal from an infrared sensor (not shown) into a digital image signal
The output side of is connected to the + side of the subtractor 11, the average value calculator 4, the storage device 2 and the feature amount calculator 7. The average value calculator 4 is a calculator that calculates the average value of the digital image signal, and is connected to the adder 10.

The memory 2 is a memory for storing the correction data, and is connected to the average value calculator 3, the + side of the subtractor 5 and the feature amount calculator 6. The average value calculator 3 is a calculator that calculates the average value of the correction data, and is connected to the minus side of the subtractor 5. The subtractor 5 is a subtracter that performs a subtraction process between the correction data and the average value of the correction data, and is connected to the multiplier 9.

The feature quantity calculator 6 is, for example, the minimum quantity of the correction data, and the feature quantity calculator 7 is, for example, A.
These are calculators that respectively calculate the minimum feature value of the image signal output from the / D converter 1, and these are connected to the multiplication gain calculator 8. The multiplication gain calculator 8 is a calculator that calculates a multiplication gain from two feature quantities,
It is connected to the multiplier 9.

The multiplier 8 is a multiplier for multiplying the subtraction result of the subtractor 5 by the multiplication gain of the multiplication gain calculator 8, and is connected to the adder 10. The adder 10 is an adder that adds the multiplication result of the multiplier 9 and the average value of the digital image signal of the average value calculator 4, and is connected to the minus side of the subtractor 11. The subtractor 11 is a subtractor that subtracts the addition result output from the adder 10 from the digital image signal, and is connected to the adder 12. The adder 12 is an adder that adds the subtraction result of the subtractor 11 and the offset component.

The analog output of the image sensor is converted into a digital image signal by the A / D converter 1. A / D
The image signal from the converter 1 is stored in the storage device 2 as correction data according to a correction data acquisition command. The stored correction data has the DC component removed by subtracting the average value calculated by the average value calculator 3 by the subtractor 5, and is multiplied by the multiplier 9.

The multiplication gain at that time is determined by the multiplication gain calculator 8 using the characteristic amount of the correction data calculated by the characteristic amount calculator 6 and the characteristic amount of the image signal calculated by the characteristic amount calculator 7. . The multiplication gain calculator 8 has a multiplication gain calculated in advance as a Look Up Table. The characteristic amount is preferably the minimum value of the output after the A / D conversion of the temperature sensor output or the image signal. Note that FIG. 1 shows an example of calculating the feature amount from the image signal. When the temperature sensor output is used as the characteristic amount, the temperature data is stored at the same time when the correction data is stored.

By multiplying by the multiplier 9,
The correction data can correspond to a change in output during dark due to a change in ambient temperature. To the multiplication result, the average value of the image signals calculated by the average value calculator 4 is added by the adder 10 to adjust the DC level. Finally, the subtractor 11 subtracts from the image signal, and the adder 12 adds the offset component.

Although the present invention is applied to the infrared image sensor in this embodiment, the present invention is not limited to this and can be applied to image sensors other than infrared.

[0020]

As described above in detail, according to the present invention, since the dark output correction data corresponding to the ambient temperature is multiplied by the gain, the dark output correction can be satisfactorily performed even when the ambient temperature changes. it can. Moreover, immediately after the dark output correction data is taken in, that is, when the ambient temperature has not changed, the multiplication gain is set to 1, which is equivalent to the conventional correction method, and it is possible to cope with variations in the dark output from time to time. .

[Brief description of drawings]

FIG. 1 is a functional block diagram showing an embodiment of a dark output correction device for an image sensor according to the present invention.

FIG. 2 is a dark-state output correction device in the related art.

FIG. 3 is a dark-state output correction device according to the related art.

[Explanation of symbols]

 1 A / D converter 2 Storage device 3, 4 Average value calculator 5, 11 Subtractor 6, 7 Feature amount calculator 8 Multiplying gain calculator 9 Multiplier 10, 12 Adder

Claims (4)

[Claims] 1. A dark output correction device for an image sensor, which corrects a dark output of an image sensor, wherein multiplication is determined by a characteristic amount of correction data output from a temperature sensor and an image output of the image sensor. Gain determining means, multiplying means for multiplying a result obtained by subtracting a correction data average value from the correction data by a multiplication gain determined by the multiplying determining means, and a multiplication result multiplied by the multiplying means and an image output of the image sensor. A dark time of the image sensor, wherein the dark output correction is performed by subtracting the addition result added by the adding means from the image output of the image sensor. Output correction device. 2. An A / D converter for converting an analog output signal of an image sensor into a digital image signal, and a first average value calculation for calculating an average value of the image signals output from the A / D converter. A storage device for storing the dark output correction data of the image sensor, a second average value calculator for calculating an average value of the dark output correction data stored in the storage device, and the A / D A first characteristic amount calculator that calculates a value characterizing the ambient temperature of the image signal output from the converter, and a value that characterizes the ambient temperature of the dark output correction data stored in the storage unit. A second feature quantity calculator, a gain calculator that inputs a feature quantity from the first feature quantity calculator and the second feature quantity calculator, and calculates a multiplication gain from these, and a dark output from the storage unit. Enter the correction data The average value of the dark-time output correction data is input from the average value calculator 2 and the subtraction result of the first subtractor and the subtraction result of the data is calculated by the gain calculator. A multiplier that multiplies the multiplication gain, an adder that adds the image data average value calculated by the first average value calculator to the multiplication result of the multiplier, and the addition result obtained by the adder And a subtracter for subtracting from the image data output from the A / D converter. 3. The dark output correction device according to claim 2, wherein the dark output correction data stored in the storage unit is a temperature from a temperature sensor that detects the image signal and the ambient temperature of the image sensor. A dark output correction device for an image sensor, which includes data. 4. A dark output correction device for an image sensor, wherein the dark output correction device according to claim 2 is applied to an infrared image sensor.