JP4207588B2 - Fixed pattern noise correction method and fixed pattern noise correction apparatus for infrared imaging device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an improvement of a fixed pattern noise correction method and a fixed pattern noise correction device for an infrared imaging device.
[0002]
[Prior art]
A fixed pattern noise correction method and a fixed pattern noise correction apparatus for removing fixed pattern noise, such as uneven brightness due to variations in characteristics of each pixel of an infrared sensor and uneven brightness due to unnecessary light incident from outside the field of view. It is already known.
[0003]
In the conventional fixed pattern noise correction method and fixed pattern noise correction apparatus, a uniform infrared incident environment is created over the entire imaging space by some method, and the image signal for each pixel obtained at this time is stored as a correction image signal. The normal final image signal is obtained by subtracting the correction image signal from the input image signal during normal imaging.
[0004]
However, the correction image signal required for proper correction changes every moment due to environmental changes of the infrared imaging device, for example, changes in the internal temperature of the infrared imaging device, etc., so that a high-quality image is continuously output. Therefore, it is necessary to periodically update the correction image signal in the memory.
[0005]
As means for creating a uniform infrared incident environment necessary for obtaining a correction image signal, an external shutter provided outside the infrared imaging device, that is, in front of the optical system, is used as an imaging target, and an infrared imaging device. In the optical system, that is, an internal shutter provided in any part of the section from the front lens to the infrared sensor in the optical system is used as an imaging target. In this regard, Patent Document 1 (example of external shutter) and This is already known from Patent Document 2 (an example of an internal shutter).
[0006]
[Patent Document 1]
JP-A-2-121480 (upper left column on page 2)
[Patent Document 2]
Japanese Patent Laying-Open No. 2002-310804 (FIG. 1)
[0007]
[Problems to be solved by the invention]
Among these, in the case where an external infrared shutter is used as an imaging target to obtain a uniform infrared incident environment, the external shutter is hardly affected by a change in the internal temperature of the infrared imaging device, and an infrared ray that is close to an ideal state. Since the incident environment can be created relatively easily, there is an advantage that a highly accurate image signal for correction can always be obtained.
However, since an external shutter is used, the overall scale of the apparatus becomes large, and when the correction image signal is frequently updated in pursuit of higher accuracy, the operation of the external shutter becomes troublesome. is there.
[0008]
On the other hand, using an internal shutter as an imaging target is excellent in portability of the device and convenience related to the opening operation of the shutter, etc., but the internal shutter is easily affected by changes in the internal temperature of the infrared imaging device, etc. Since the temperature unevenness occurs in the internal shutter itself, it is difficult to realize an ideal infrared incident environment, and there is a problem that it is difficult to obtain a highly accurate image signal for correction.
[0009]
OBJECT OF THE INVENTION
Accordingly, an object of the present invention is to solve the drawbacks of the prior art and to effectively use an internal shutter provided in the infrared imaging device to obtain a high-accuracy image signal. A fixed pattern noise correction method and a fixed pattern noise correction apparatus are provided.
[0010]
[Means for Solving the Problems]
A method for correcting a fixed pattern noise of an infrared imaging device according to the present invention converts an image formed on an infrared sensor through an optical system into an image signal, performs correction for removing fixed pattern noise, and then performs a final image signal. Is a fixed pattern noise correction method of an infrared imaging device to output as, in order to achieve the above object,
An image is captured in a state where the internal shutter provided inside the infrared imaging device is opened and the external shutter provided outside the infrared imaging device is closed, and the input image signal obtained by capturing the image is the first. After executing the sensor characteristic correction data acquisition process stored in the frame memory of
Internal image capture is executed with the internal shutter closed, and the image signal stored in the first frame memory is subtracted from the input image signal obtained by the image capture and stored in the second frame memory. Execute the shutter characteristic correction data acquisition process,
Further, the image capturing is performed again with the internal shutter closed, and the superimposition characteristic correction data acquisition step is executed to update and store the input image signal obtained by capturing the image in the first frame memory,
Thereafter, the image is captured every predetermined cycle with the internal shutter and the external shutter opened, and each time the image is stored in the first frame memory from the input image signal obtained by capturing the image of the cycle. The output data correction step of subtracting the image signal and adding the image signal stored in the second frame memory and outputting as the final image signal is repeatedly performed.
[0011]
In the above configuration, first, by executing the sensor characteristic correction data acquisition step, an image is captured with the internal shutter opened and the external shutter closed, and the input image signal obtained by capturing the image is Store in one frame memory. Since the external shutter to be imaged has a constant temperature distribution so as to obtain a uniform infrared incident environment, the input image signal acquired in this process is caused by variations in the characteristics of each pixel of the infrared sensor. This input image signal is stored in the first frame memory as sensor characteristic correction data, that is, data for correcting variations in characteristics of each pixel of the infrared sensor.
Next, an internal shutter characteristic correction data acquisition step is executed, an image is captured with the internal shutter closed, and an image signal stored in the first frame memory from the input image signal obtained by capturing the image Is stored in the second frame memory. Since the internal shutter to be imaged is likely to be affected by a change in the internal temperature of the infrared imaging device or the like, there is a high possibility that temperature unevenness has occurred in the internal shutter itself. Therefore, the input image signal captured in this step is a superimposition of luminance unevenness due to variation in characteristics of each pixel of the infrared sensor and temperature unevenness of the internal shutter itself. Since the image signal stored in the first frame memory, that is, the luminance unevenness due to the characteristic variation of each pixel of the infrared sensor is subtracted and removed, it is actually stored in the second frame memory. These are image signals representing the temperature unevenness of the internal shutter itself. This image signal is internal shutter characteristic correction data, that is, data for correcting temperature unevenness of the internal shutter.
Furthermore, by executing the superimposition characteristic correction data acquisition step, the image is captured while the internal shutter is closed, and the input image signal obtained by capturing the image is updated to the first frame memory. Remember. The input image signal captured in this process is obtained by superimposing the luminance unevenness due to the characteristic variation of each pixel of the infrared sensor and the temperature unevenness of the internal shutter itself, and this input image signal is directly superimposed. The correction data is updated and stored in the first frame memory. As a result, the sensor characteristic correction data first stored in the first frame memory in the sensor characteristic correction data acquisition step is discarded.
In other words, the sensor characteristic correction data acquisition step and the internal shutter characteristic correction data acquisition step described above substantially superimpose the luminance unevenness due to the characteristic variation of each pixel of the infrared sensor and the temperature unevenness of the internal shutter itself. The internal shutter characteristic correction data, which is an image signal indicating the temperature unevenness of the internal shutter itself, is separated by subtracting the luminance unevenness due to the characteristic variation of each pixel of the infrared sensor from the input image signal, and this internal shutter characteristic correction This is a preprocessing required to store only data in the second frame memory.
Then, in the normal process of outputting the final image signal, that is, in the output data correction step, the external monitoring target is imaged at predetermined intervals with the internal shutter and the external shutter being opened, and the image is captured. Each time, the image signal stored in the first frame memory is subtracted from the input image signal obtained by capturing the image of the cycle, and the image signal stored in the second frame memory is added. The process of outputting as the final image signal is repeatedly executed. The input image signal captured in this step is not only an appropriate image signal depending on the temperature difference of the external monitoring target, but also luminance unevenness due to characteristic variations of each pixel of the infrared sensor and temperature unevenness of the internal shutter itself. The image signal stored in the first frame memory is subtracted from the image signal, and the image signal stored in the second frame memory is added to the infrared signal. The influence of brightness unevenness due to variations in characteristics of each pixel of the sensor and temperature unevenness of the internal shutter itself is eliminated, and only an appropriate image signal depending on the temperature difference of the external monitoring target is output as the final image signal. Can do.
For example, the content of the sensor characteristic correction data obtained in the sensor characteristic correction data acquisition process is Xa, and the content of the internal shutter characteristic correction data stored in the second frame memory in the internal shutter characteristic correction data acquisition process is Xb. In this case, the content of the superimposition characteristic correction data updated and stored in the first frame memory in the superimposition characteristic correction data acquisition step is [Xa + Xb]. If the true content of the input image signal in the output data correction step is Xo, the input image signal recognized by the infrared sensor is affected by the characteristic variation Xa of each pixel of the infrared sensor [Xo + Xa [Xo + Xa] is subtracted from [Xa + Xb], which is the contents of the first frame memory, to become [Xo-Xb] once, and further, this image signal [Xo-Xb] By adding Xb which is the contents of the frame memory, Xo indicating the true contents of the input image signal is finally output as the final image signal.
In this way, in the output data correction step, the influence of the luminance unevenness Xa and the temperature unevenness Xb of the internal shutter itself due to the variation in the characteristics of each pixel of the infrared sensor is removed, so that the temperature difference between the external monitoring targets can be reduced. It is possible to output an appropriate dependent image signal Xo as a final image signal.
[0012]
In addition, when such a configuration is applied, the superimposition characteristic correction data acquisition step is repeatedly executed at predetermined intervals longer than the predetermined cycle of the output data correction step, and the sensor characteristic correction data acquisition step and the internal shutter characteristics are performed. It is desirable that the process including the correction data acquisition process and the superimposition characteristic correction data acquisition process is repeatedly executed at predetermined intervals longer than the predetermined period of the superimposition characteristic correction data acquisition process.
[0013]
In this way, by repeatedly executing the superimposition characteristic correction data acquisition process at predetermined intervals, the superimposition characteristic correction data [Xa + Xb] in the first frame memory can be sequentially updated to the latest value. Among the errors [Xa + Xb] in which the luminance unevenness Xa and the temperature unevenness Xb of the internal shutter itself are superposed due to the characteristic variation of each pixel, the characteristic of each pixel that changes due to the temperature drift of the infrared sensor, etc. The variation Xa can be accurately corrected.
At the same time, since the process consisting of the sensor characteristic correction data acquisition step, the internal shutter characteristic correction data acquisition step, and the superimposition characteristic correction data acquisition step is repeatedly executed every predetermined cycle longer than this, the second frame memory The internal shutter characteristic correction data Xb can be updated to the latest value sequentially. Therefore, even when the temperature unevenness Xb of the internal shutter itself fluctuates due to a change in the internal temperature of the infrared imaging device or the like, the value of Xb constituting a part of the superimposition characteristic correction data in the first frame memory and the first It becomes possible to synchronize with the value of Xb constituting the internal shutter characteristic correction data in the second frame memory, and an appropriate image signal Xo that is not affected by fluctuations in temperature unevenness Xb of the internal shutter itself is used as the final image signal. It becomes possible to output.
In addition, the pre-processing required for updating the internal shutter characteristic correction data, that is, the sensor characteristic correction data acquisition process that needs to use the external shutter as an imaging target, etc., is performed using the internal shutter. Since it is executed at predetermined intervals that are relatively longer than the update period of the characteristic correction data, the conventional fixed pattern noise that has acquired the data required for correction only by imaging the external shutter Compared to the correction method, the number of times the external shutter is imaged can be reduced, and the troublesomeness of the external shutter operation can be reduced.
[0014]
In order to achieve the same object as described above, an operating state detecting means for detecting the operating state of the infrared imaging device is provided, and an image signal at the time of internal shutter imaging that varies according to the operating state of the infrared imaging device is captured by infrared imaging. Store it in the memory of the infrared imaging device in advance corresponding to the operating status of the device,
Superimposition characteristic correction data acquisition step of executing image capturing in a state where an internal shutter provided in the infrared imaging device is closed, and storing an input image signal obtained by capturing the image in the first frame memory;
After executing an internal shutter characteristic correction data acquisition step of retrieving an image signal at the time of internal shutter imaging corresponding to the operation status detected by the operation status detection means from the memory and storing it in the second frame memory,
The image capture is executed every predetermined cycle with the internal shutter opened, and each time, the image signal stored in the first frame memory is subtracted from the input image signal obtained by capturing the image of the cycle, In addition, the output data correction step of adding the image signals stored in the second frame memory and outputting as the final image signal may be repeatedly executed.
[0015]
When such a configuration is applied, an image signal (internal shutter characteristic correction data) Xb at the time of internal shutter imaging that fluctuates according to the operating status of the infrared imaging device is preliminarily infrared-linked in accordance with the operating status of the infrared imaging device. It is stored in the memory of the imaging device. As a parameter representing the operating status of the infrared imaging device, the elapsed time after the operation of the infrared imaging device or the internal temperature of the infrared imaging device can be used. Here, in the case of using the elapsed time after the operation of the infrared imaging device as a parameter representing the operating state of the infrared imaging device, the image signal at the time of imaging the internal shutter is previously associated with the elapsed time after the operation of the infrared imaging device. (Internal shutter characteristic correction data) Xb is measured, for example, in increments of several minutes and stored in a memory. Further, when the internal temperature of the infrared imaging device is used as a parameter representing the operating status of the infrared imaging device, an image signal (internal shutter characteristic correction data at the time of internal shutter imaging) is previously associated with the internal temperature of the infrared imaging device. ) Xb is measured with a step size of several degrees C. and stored in the memory.
First, by executing the superimposition characteristic correction data acquisition step, the image is captured while the internal shutter is closed, and the input image signal obtained by capturing the image is stored in the first frame memory. To do. The input image signal captured in this step is [Xa + Xb] in which the luminance unevenness Xa caused by the variation in characteristics of each pixel of the infrared sensor and the temperature unevenness Xb of the internal shutter itself are superimposed. Is stored in the first frame memory as superimposition characteristic correction data [Xa + Xb].
Next, an internal shutter characteristic correction data acquisition step is executed, and the operating status of the infrared imaging device is detected by the operating status detecting means, for example, the elapsed time after the operation of the infrared imaging device and the internal temperature of the infrared imaging device. The image signal (internal shutter characteristic correction data) Xb at the time of internal shutter imaging corresponding to the range (elapsed time and range of the internal temperature increment) is retrieved from the memory and stored in the second frame memory.
The normal process of outputting the final image signal, that is, the output data correction process is the same as described above, and the external monitoring target is imaged at predetermined intervals with the internal shutter and the external shutter opened, and the image is captured. Each time, the image signal [Xa + Xb] stored in the first frame memory is subtracted from the input image signal [Xo + Xa] obtained by capturing the image of the period, and stored in the second frame memory. Repeatedly adding the image signal Xb and outputting it as the final image signal Xo eliminates uneven brightness due to variations in characteristics of each pixel of the infrared sensor and uneven temperature of the internal shutter itself. Then, an appropriate image signal depending on the temperature difference of the external monitoring target is output as the final image signal.
When such a configuration is applied, the image signal (internal shutter characteristic correction data) Xb at the time of internal shutter imaging, which varies according to the operating status of the infrared imaging device, is captured in advance by infrared imaging in a manner corresponding to the operating status of the infrared imaging device. Since it is stored in the memory of the apparatus, processing such as imaging of an external shutter is not required to specify this Xb. Therefore, it is not necessary to provide an external shutter for the infrared imaging device, and the troublesome operation of the external shutter is eliminated, and the portability of the infrared imaging device is improved.
[0016]
Here, the superimposition characteristic correction data acquisition step and the internal shutter characteristic correction data acquisition step may be repeatedly executed every predetermined cycle longer than the predetermined cycle of the output data correction step.
[0017]
By repeatedly executing the superimposition characteristic correction data acquisition step every predetermined period, the superimposition characteristic correction data in the first frame memory can be sequentially updated to the latest value, so that the characteristic of each pixel of the infrared sensor can be changed. Of the error [Xa + Xb] in which the luminance unevenness due to the variation and the temperature variation of the internal shutter itself are superimposed, in particular, the characteristic variation Xa that changes due to the temperature drift of the infrared sensor can be corrected accurately. it can.
At the same time, since the internal shutter characteristic correction data acquisition step is repeatedly executed, the internal shutter characteristic correction data in the second frame memory can be sequentially updated to the latest value. Value of Xb constituting a part of the superimposition characteristic correction data in the first frame memory even if the temperature unevenness Xb of the internal shutter itself fluctuates due to the operating time of the camera, the change in the internal temperature of the infrared imaging device, etc. And the value of Xb constituting the internal shutter characteristic correction data in the second frame memory can be substantially synchronized and matched.
Accordingly, it is possible to output an appropriate image signal Xo as a final image signal without being affected by variations in characteristics Xa of each pixel that change due to temperature drift of the infrared sensor or fluctuations in temperature unevenness Xb of the internal shutter itself. .
[0018]
The fixed pattern noise correction apparatus according to the present invention also fixes an infrared imaging apparatus that converts an image formed on an infrared sensor through an optical system into an image signal, removes the fixed pattern noise, and outputs it as a final image signal. In order to achieve the above object, a pattern noise correction device,
An openable / closable internal shutter provided inside the infrared imaging device; an openable / closable external shutter provided outside the infrared imaging device; first and second frame memories for storing image signals;
Sensor characteristic correction data acquisition means for storing an input image signal acquired from an infrared sensor in a state where the internal shutter is opened and the external shutter is closed;
Internal shutter characteristic correction data acquisition means for subtracting the image signal stored in the first frame memory from the input image signal acquired from the infrared sensor in a state where the internal shutter is closed, and storing it in the second frame memory;
Superimposition characteristic correction data acquisition means for storing the input image signal acquired from the infrared sensor in a state where the internal shutter is closed in the first frame memory;
An input image signal is obtained from the infrared sensor at predetermined intervals with the internal shutter and the external shutter opened, the image signal stored in the first frame memory is subtracted from the input image signal, and the second Output data correction means for adding the image signals stored in the frame memory and outputting as final image signals;
The superimposition characteristic correction data acquisition means is repeatedly operated every predetermined operation cycle longer than the operation cycle of the output data correction means, and the sensor characteristic correction data acquisition means, the internal shutter characteristic correction data acquisition means, and the superimposition characteristic correction data acquisition Are sequentially operated in the order of sensor characteristic correction data acquisition means, internal shutter characteristic correction data acquisition means, and superimposition characteristic correction data acquisition means, every predetermined operation cycle longer than the operation cycle of the superimposition characteristic correction data acquisition means. And a control means.
[0019]
In the apparatus configuration described above, first, the sensor characteristic correction data acquisition unit, the internal shutter characteristic correction data acquisition unit, and the superimposition characteristic correction data acquisition unit operate in this order under the control of the sequential control unit.
That is, first, the sensor characteristic correction data acquisition unit is operated, and the input image signal acquired from the infrared sensor in a state where the internal shutter is opened and the external shutter is closed is stored as sensor characteristic correction data in the first frame memory. Since the external shutter to be imaged has a constant temperature distribution so as to obtain a uniform infrared incident environment, the input image signal acquired by the sensor characteristic correction data acquisition means is a characteristic for each pixel of the infrared sensor. The input image signal is stored in the first frame memory as sensor characteristic correction data, that is, data for correcting the characteristic variation of each pixel of the infrared sensor. Become.
Next, the internal shutter characteristic correction data acquisition means is activated to subtract the image signal stored in the first frame memory from the input image signal acquired from the infrared sensor with the internal shutter closed. Store in frame memory. Since the internal shutter to be imaged is likely to be affected by a change in the internal temperature of the infrared imaging device or the like, there is a high possibility that temperature unevenness has occurred in the internal shutter itself. Therefore, the input image signal captured by the internal shutter characteristic correction data acquisition unit is a superimposition of the luminance unevenness due to the characteristic variation of each pixel of the infrared sensor and the temperature unevenness of the internal shutter itself. Since the image signal stored in the first frame memory, that is, the luminance unevenness due to the characteristic variation of each pixel of the infrared sensor is subtracted from the input image signal, the second frame is actually removed. What is stored in the memory is an image signal representing the temperature unevenness of the internal shutter itself. This image signal is internal shutter characteristic correction data, that is, data for correcting temperature unevenness of the internal shutter.
Next, the superimposition characteristic correction data acquisition unit operates to store the input image signal acquired from the infrared sensor in a state where the internal shutter is closed in the first frame memory. The input image signal captured by the superimposition characteristic correction data acquisition unit is a superimposition of luminance unevenness due to characteristic variations of each pixel of the infrared sensor and temperature unevenness of the internal shutter itself. Are stored in the first frame memory as superimposition characteristic correction data as they are. As a result, the sensor characteristic correction data first stored in the first frame memory by the sensor characteristic correction data acquisition unit is discarded.
Through the processing executed by each of the above means, the superimposition characteristic correction in which the luminance unevenness Xa caused by the characteristic variation of each pixel of the infrared sensor and the temperature unevenness Xb of the internal shutter itself are superimposed on the first frame memory. Data [Xa + Xb] is stored, and only the internal shutter characteristic correction data Xb representing the temperature unevenness of the internal shutter itself is stored in the second frame memory.
Then, under the control of the sequential control means, the output data correction means is repeatedly operated every predetermined period, and the image signal Xo to be monitored and the luminance unevenness Xa from the infrared sensor with the internal shutter and the external shutter opened. Input image signal [Xo + Xa] is acquired, superimposition characteristic correction data [Xa + Xb] stored in the first frame memory is subtracted from this input image signal [Xo + Xa], and further the second frame memory is subtracted. The stored internal shutter characteristic correction data Xb is added and output as the final image signal Xo.
Here, since [Xo + Xa] − [Xa + Xb] + Xb = Xo, the first term Xa on the left side is equal to the second term Xa on the left side, and the second term Xb on the left side and the third term on the left side As long as the term Xb is equal, the image signal Xo to be monitored that is not affected by the luminance unevenness Xa caused by the variation in characteristics of each pixel of the infrared sensor and the temperature unevenness Xb of the internal shutter itself is appropriately used as the final image signal. Can be output.
In addition, while the output data correction unit is repeatedly operated, the sequential control unit repeatedly operates the superimposition characteristic correction data acquisition unit for each predetermined operation cycle longer than the operation cycle of the output data correction unit. The value of the superimposition characteristic correction data [Xa + Xb] is sequentially updated, and sensor characteristic correction data acquisition means, internal shutter characteristic correction data acquisition means, and superposition characteristic correction data acquisition means are obtained every predetermined operation cycle longer than this. Are repeatedly operated in the same manner as described above to successively update the value of the internal shutter characteristic correction data Xb in the second frame memory.
In this way, as a result of sequentially updating the value of the superimposition characteristic correction data [Xa + Xb] in the first frame memory, the first term Xa on the left side and the second term Xa on the left side are substantially equal. In addition, since the value of the internal shutter characteristic correction data Xb in the second frame memory is sequentially updated, the second term Xb on the left side and the third term Xb on the left side are substantially equal.
Therefore, the variation in characteristics Xa of each pixel changes due to temperature drift of the infrared sensor, and further, the temperature unevenness Xb of the internal shutter itself changes due to the change of the internal temperature of the infrared imaging device etc. superimposed on this. Even in such a case, the influence of the luminance unevenness Xa and the temperature unevenness Xb of the internal shutter itself due to the variation in characteristics of each pixel of the infrared sensor is surely removed, and it depends on the temperature difference of the external monitoring target. The appropriate image signal Xo can be continuously output as the final image signal.
In addition, pre-processing required for updating the internal shutter characteristic correction data Xb, that is, acquisition of sensor characteristic correction data that requires the use of the external shutter as an imaging target is performed using the internal shutter. Since it is executed at predetermined intervals that are relatively longer than the update period of the superimposition characteristic correction data, a conventional fixed pattern that acquires data required for correction only by imaging the external shutter Compared to the noise correction method, the number of times the external shutter is imaged can be reduced, and the troublesome operation of the external shutter is reduced.
[0020]
In order to achieve the same object as described above, an openable and closable internal shutter provided inside the infrared imaging device, first and second frame memories for storing image signals, and operating status of the infrared imaging device An operation state detection means for detecting, a memory that stores in advance an image signal at the time of internal shutter imaging that varies according to the operation state of the infrared imaging device, corresponding to the operation state of the infrared imaging device;
Superimposition characteristic correction data acquisition means for storing the input image signal acquired from the infrared sensor in a state where the internal shutter is closed in the first frame memory;
An internal shutter characteristic correction data acquisition unit that retrieves an image signal at the time of internal shutter imaging corresponding to the operation state detected by the operation state detection unit from the memory and stores it in the second frame memory;
An input image signal is obtained from the infrared sensor at predetermined intervals with the internal shutter opened, and the image signal stored in the first frame memory is subtracted from the input image signal, and the second frame memory Output data correction means for adding the image signals stored in and outputting as the final image signal;
The superimposition characteristic correction data acquisition unit and the internal shutter characteristic correction data acquisition unit may include a sequential control unit that repeatedly operates every predetermined operation cycle longer than the operation cycle of the output data correction unit.
[0021]
When such a configuration is applied, first, the superimposition characteristic correction data acquisition unit and the internal shutter characteristic correction data acquisition unit operate in this order under the control of the sequential control unit.
That is, first, the superimposition characteristic correction data acquisition unit operates to store the input image signal acquired from the infrared sensor with the internal shutter opened as superimposition characteristic correction data in the first frame memory. The input image signal captured by the superimposition characteristic correction data acquisition means is [Xa + Xb] obtained by superimposing the luminance unevenness Xa caused by the variation in characteristics of each pixel of the infrared sensor and the temperature unevenness Xb of the internal shutter itself, This input image signal is directly stored in the first frame memory as superimposition characteristic correction data [Xa + Xb].
Next, the internal shutter characteristic correction data acquisition unit operates, the operation state detection unit detects the operation state of the infrared imaging device, and an image signal (internal shutter characteristic correction data) at the time of internal shutter imaging corresponding to this operation state Xb is retrieved from the memory and stored in the second frame memory. As a parameter representing the operating status of the infrared imaging device, it is possible to use an elapsed time after the operation of the infrared imaging device or an internal temperature of the infrared imaging device. When the elapsed time after operation of the infrared imaging device is used as a parameter representing the operation status of the infrared imaging device, an image signal (internal shutter) at the time of imaging the internal shutter is previously associated with the elapsed time after operation of the infrared imaging device. The characteristic correction data (Xb) is measured, for example, in increments of several minutes and stored in the memory. Further, when the internal temperature of the infrared imaging device is used as a parameter representing the operating status of the infrared imaging device, an image signal (internal shutter characteristic correction data at the time of internal shutter imaging) is previously associated with the internal temperature of the infrared imaging device. ) Xb is measured with a step size of several degrees Celsius, for example, and stored in the memory.
Specifically, the internal shutter characteristic correction data acquisition means is based on the elapsed time or the internal temperature detected by a timer or temperature sensor serving as the operating status detection means, and the range of the operating status (the increment of the elapsed time or the internal temperature). The image signal (internal shutter characteristic correction data) Xb at the time of internal shutter imaging corresponding to the range (2) is retrieved from the memory and stored in the second frame memory.
Through the processing executed by each of the above means, the superimposition characteristic correction in which the luminance unevenness Xa caused by the characteristic variation of each pixel of the infrared sensor and the temperature unevenness Xb of the internal shutter itself are superimposed on the first frame memory. Data [Xa + Xb] is stored, and only the internal shutter characteristic correction data Xb representing the temperature unevenness of the internal shutter itself is stored in the second frame memory.
Then, under the control of the sequential control means, the output data correction means is repeatedly operated every predetermined period, and includes the image signal Xo to be monitored and the luminance unevenness Xa from the infrared sensor in a state where the internal shutter is opened. The input image signal [Xo + Xa] is acquired, the superimposition characteristic correction data [Xa + Xb] stored in the first frame memory is subtracted from the input image signal [Xo + Xa], and further stored in the second frame memory. The internal shutter characteristic correction data Xb is added and output as the final image signal Xo.
Similarly to the above, [Xo + Xa] − [Xa + Xb] + Xb = Xo, so that the first term Xa on the left side is equal to the second term Xa on the left side, and the second term Xb on the left side is the same as the second term Xb. As long as Xb in the third term is equal, it is possible to appropriately output the image signal Xo to be monitored as the final image signal.
Here, the sequential control means repeatedly operates the superimposition characteristic correction data acquisition means and the internal shutter characteristic correction data acquisition means at every predetermined operation cycle longer than the operation cycle of the output data correction means, and the first frame memory Since the value of the superimposition characteristic correction data [Xa + Xb] is sequentially updated, and at the same time, the value of the internal shutter characteristic correction data Xb in the second frame memory is sequentially updated. Xa of the second term on the left side is substantially equal, and Xb of the second term on the left side and Xb of the third term on the left side are also substantially equal.
Therefore, the variation in characteristics Xa of each pixel changes due to temperature drift of the infrared sensor, and further, the temperature unevenness Xb of the internal shutter itself changes due to the change of the internal temperature of the infrared imaging device etc. superimposed on this. Even in such a case, the influence of the luminance unevenness Xa and the temperature unevenness Xb of the internal shutter itself due to the variation in characteristics of each pixel of the infrared sensor is surely removed, and it depends on the temperature difference of the external monitoring target. The appropriate image signal Xo can be continuously output as the final image signal.
In addition, the image signal (internal shutter characteristic correction data) Xb at the time of internal shutter imaging that varies according to the operating status of the infrared imaging device is stored in advance in the memory of the infrared imaging device in a manner corresponding to the operating status of the infrared imaging device. Therefore, it is not necessary to perform processing such as imaging the external shutter in order to specify this Xb. Therefore, it is not necessary to provide an external shutter in the infrared imaging device, and the troublesome operation of the external shutter is eliminated, and the portability of the infrared imaging device is improved.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a conceptual diagram showing an outline of the configuration of an infrared imaging device 1 according to an embodiment to which the fixed pattern noise correction method of the present invention is applied. FIGS. 2 and 3 are fixed patterns provided in the infrared imaging device 1. FIG. 6 is an operational principle diagram showing an outline of the operation of the noise correction apparatus 2.
[0023]
In FIG. 1, the first frame memory 3 includes a superimposition characteristic obtained by adding a fixed pattern noise component caused by variation in characteristics of each pixel of the infrared sensor 4 and a fixed pattern noise component caused by temperature unevenness of the internal shutter 5. The correction data is stored. The second frame memory 6 is for recording only the fixed pattern noise component caused by the temperature unevenness of the internal shutter 5.
The fixed pattern noise component resulting from the variation in characteristics of each pixel of the infrared sensor 4 is the actual sensor characteristic correction data, and the fixed pattern noise component resulting from the temperature unevenness of the internal shutter 5 is the actual internal shutter. The characteristic correction data, which is a combination of these, is the actual superposition characteristic correction data.
[0024]
In this fixed pattern noise correction apparatus 2, various correction data output from the first frame memory 3 and the second frame memory 6 are added to or subtracted from the input image signal 7 acquired by the infrared sensor 4. Thus, it is possible to obtain an appropriate final image signal 8 that does not depend on variations in characteristics of each pixel of the infrared sensor 4 and temperature unevenness of the internal shutter 5.
[0025]
Here, the function of each part of the infrared imaging device 1 will be briefly described with reference to FIG. First, infrared rays incident from the outside are imaged on the infrared sensor 4 by the optical system 9. The output signal of the infrared sensor 4 is amplified by the amplifier 10, converted to a digital signal by the AD converter 11, and input to the fixed pattern noise correction device 2 as the input image signal 7. The first frame memory 3 and the second frame memory 6 are memories for storing correction data. When the correction data is updated, images of the input image signal 7 and the intermediate image signal 11 are recorded, respectively. The subtracter 12 subtracts the output of the first frame memory 3 from the input image signal 7 and outputs it as an intermediate image signal 11 to the adder 13. The adder 13 adds the output of the second frame memory 6 to the intermediate image signal 11 and outputs it as a final image signal 8 to a signal processing device such as the display device 14.
[0026]
The external shutter 15 is for creating a uniform infrared incident environment for each pixel of the infrared sensor 4, and is normally maintained at a temperature equivalent to the imaging scene. It is used only when the correction data in the frame memory 6 is completely updated. Since the internal shutter 5 is built in the infrared imaging device 1, it is difficult to maintain a temperature environment equivalent to that of the imaging scene, and temperature unevenness occurs on the shutter surface itself, so a uniform infrared incident environment for each pixel. However, it is the same as the external shutter 15 in that it is installed for the purpose of creating a predetermined infrared incident environment.
[0027]
Next, the overall operation of the fixed pattern noise correction apparatus 2 will be briefly described with reference to FIGS.
[0028]
The general infrared imaging device 1 outputs an optical system 9 and an amplifier 10 that amplifies an output signal of the infrared sensor 4 and an amplifier 10 to collect infrared rays incident from an imaging scene onto the infrared sensor 4. There are components such as an AD converter 11 for converting an analog signal to a digital signal, a display device 14 for displaying an infrared image, and the like, and these components are already known, and Since it is not directly related to the gist, detailed description is omitted here.
[0029]
The operation of the fixed pattern noise correction apparatus 2 is roughly divided into an operation at the time of normal imaging and an operation at the time of updating correction data. Further, the operation at the time of updating correction data is the first frame memory 3 and the second frame memory 6. The correction data is updated together with the case where only the correction data in the first frame memory 3 is updated.
[0030]
First, the operation when both the correction data of the first frame memory 3 and the second frame memory 6 are updated will be described with reference to FIGS.
First, the input image signal 7 when the external shutter 15 is closed is first stored in the first frame memory 3. The waveform image of this signal is as shown in FIG. Since the imaging space is covered with the external shutter 15, the imaging scene incident on the infrared sensor 4 is flat regardless of the position of each pixel of the infrared sensor 4. Therefore, the input image signal 7 output from the infrared sensor 4 becomes data Xa reflecting the fixed pattern noise component caused by the characteristic variation of each pixel of the infrared sensor 4, and this sensor characteristic correction data Xa is the first data Xa. It is stored in the frame memory 3. This is a processing procedure corresponding to the sensor characteristic correction data acquisition step.
Next, the intermediate image signal 11 when the internal shutter 5 is closed is stored in the second frame memory 6. The waveform image of each signal is as shown in FIG. Since the imaging space is covered with the internal shutter 5, the input image signal 7 output from the infrared sensor 4 includes the fixed pattern noise component Xa and the internal shutter 5 due to the characteristic variation of each pixel of the infrared sensor 4. The fixed pattern noise component Xb resulting from the temperature unevenness is reflected. However, since the fixed pattern noise component Xa resulting from the variation in the characteristics of the infrared sensor 5 is subtracted and removed by the subtractor 12, the intermediate image signal 11 stored in the second frame memory 6 is the temperature of the internal shutter 5. Only the fixed pattern noise component Xb caused by the unevenness, that is, the internal shutter characteristic correction data Xb. This is a processing procedure corresponding to the internal shutter characteristic correction data acquisition step.
Then, the input image signal 7 when the internal shutter 5 is closed is updated and stored in the first frame memory 3 again. The waveform image of each signal is as shown in FIG. Since the imaging space is covered with the internal shutter 5, the input image signal 7 output from the infrared sensor 4 includes the fixed pattern noise component Xa and the internal shutter 5 due to the characteristic variation of each pixel of the infrared sensor 4. The fixed pattern noise component Xb caused by the temperature unevenness of the image data is reflected, and the data stored in the first frame memory 3 includes the fixed pattern noise component Xa caused by the variation in characteristics of each pixel of the infrared sensor 4 and the internal The fixed pattern noise component [Xa + Xb] is obtained by superimposing the fixed pattern noise component Xb caused by the uneven temperature of the shutter 5, that is, the superimposition characteristic correction data [Xa + Xb]. This is a processing procedure corresponding to the superimposition characteristic correction data acquisition step.
[0031]
Usually, a series of these processing operations are performed at a relatively long predetermined period, for example, at an interval of 10 minutes after the infrared imaging apparatus 1 is turned on.
[0032]
Next, the operation when only the correction data of the first frame memory 3 is updated will be described with reference to FIG. 1 and FIG.
This operation is based on the superimposition characteristic correction data [Xa + Xb] stored in the first frame memory 3, and in particular, the fixed pattern noise component related to the characteristic variation for each pixel that changes due to the temperature drift of the infrared sensor 4. The processing content is the same as the processing corresponding to the above-described superimposition characteristic correction data acquisition step.
[0033]
This operation is performed at a relatively short predetermined period, for example, at an interval of 1 minute after the infrared imaging device 1 is turned on.
[0034]
Next, operations during normal imaging will be described with reference to FIGS. This operation is repeated at predetermined intervals that are much shorter than the correction data update process (superimposition characteristic correction data acquisition step) related to the first frame memory 3 described above with both the external shutter 15 and the internal shutter 5 opened. To be implemented. The waveform image of each signal during normal imaging is as shown in FIG.
First, true imaging scene data Xo depending on the temperature difference of the imaged monitoring target is input to the infrared sensor 4, but the infrared sensor 4 is fixed due to variation in characteristics of each pixel or temperature drift. Since the pattern noise component Xa affects the infrared sensor 4, [Xo + Xa] reflecting the fixed pattern noise component Xa is output as the input image signal 7.
Next, the subtractor 12 performs a subtraction process on the input image signal 7 based on the superimposition characteristic correction data [Xa + Xb] stored in the first frame memory 3. The content of the signal 11 is [Xo + Xa] − [Xa + Xb], that is, [Xo−Xb].
Further, the adder 13 executes addition processing on the intermediate image signal 11 based on the internal shutter characteristic correction data Xb stored in the second frame memory 6, and as a result, the final output from the adder 13 is performed. The content of the image signal 8 is [Xo−Xb] + Xb, that is, Xo, and the influence of luminance unevenness Xa caused by variation in characteristics of each pixel of the infrared sensor 4 or temperature drift or temperature unevenness Xb of the internal shutter itself is removed. Thus, the image signal Xo to be monitored can be appropriately output as the final image signal 8. This is a processing procedure corresponding to the output data correction step.
[0035]
While the process corresponding to the output data correction process is repeatedly executed in this way, a temperature drift may occur in the infrared sensor 4 and the sensor characteristic correction data Xa may change to an appropriate value. Since the update process of the correction data [Xa + Xb] in the first frame memory 3 is repeatedly executed, for example, at intervals of 1 minute, the contents of the item Xa related to the sensor characteristic correction data in the superimposition characteristic correction data [Xa + Xb] It can be automatically updated in accordance with the temperature drift of the infrared sensor 4.
In addition, the temperature unevenness of the internal shutter 5 itself may change and change to an appropriate value as the internal shutter characteristic correction data Xb. However, the process of updating the correction data Xb in the second frame memory 6 is, for example, 10 minutes. Since it is repeatedly executed at intervals, even if the temperature unevenness of the internal shutter 5 itself fluctuates, the content of the internal shutter characteristic correction data Xb in the second frame memory 6 is automatically updated in response to this variation. can do.
In this manner, the value of the correction data [Xa + Xb] in the first frame memory 3 and the value of the correction data Xb in the second frame memory 6 are sequentially updated. As a result, the superimposition characteristic correction data in the first frame memory 3 is obtained. The value of the item Xb constituting a part of [Xa + Xb] and the value of the item Xb constituting the internal shutter characteristic correction data in the second frame memory 6 are substantially always the same value. The image signal Xo to be monitored can always be appropriately output as the final image signal 8 by the cooperative operation by the processing and the addition processing of the adder 13, that is, the calculation processing of [Xo + Xa] − [Xa + Xb] + Xb. .
[0036]
The outline of the configuration and the overall operation process of the fixed pattern noise correction apparatus 2 has been described above.
[0037]
Next, specific configurations of the infrared imaging device 1 and the fixed pattern noise correction device 2 will be described with reference to the functional block diagram of FIG.
[0038]
The fixed pattern noise correction apparatus 2 includes a CPU 16 for arithmetic processing, a ROM 17 storing various control programs, a RAM 18 used for temporary storage of arithmetic data, the first frame memory 3 and the second frame. The display device 14 and the operation panel 20 are connected to the input / output circuit 19 of the CPU 16 that includes the memory 6.
[0039]
The optical system 9, the infrared sensor 4, the amplifier 10, and the AD converter 11 in the infrared imaging device 1 are known components, and the input image signal 7 output from the AD converter 11 is sent to the CPU 16 via the input / output circuit 19. To be read.
[0040]
The CPU 16 implements functions as sensor characteristic correction data acquisition means, internal shutter characteristic correction data acquisition means, superimposition characteristic correction data acquisition means, output data correction means, and sequential control means together with a control program stored in the ROM 17.
[0041]
The external shutter 15 is provided in front of the internal optical system 9 outside the infrared imaging device 1 and is opened and closed by a solenoid 22 via an input / output circuit 19 and a solenoid drive circuit 21 in response to a command from the CPU 16. The internal shutter 5 is provided inside the infrared imaging device 1, more specifically, between the optical system 9 and the infrared sensor 4, and the input / output circuit 19 and the solenoid drive circuit 23 are connected in response to a command from the CPU 16. And is opened and closed by a solenoid 24.
[0042]
Next, referring to the flowchart of FIG. 5 showing the internal processing executed by the CPU 16, sensor characteristic correction data acquisition means, internal shutter characteristic correction data acquisition means, superimposition characteristic correction data acquisition means, output data correction means, sequential A processing operation of the CPU 16 functioning as a control unit will be described in detail. It is assumed that the external shutter 15 and the internal shutter 5 are kept open in the initial state.
[0043]
When the infrared imaging device 1 and the fixed pattern noise correction device 2 are turned on by operating the operation panel 20, internal processing of the CPU 16 functioning as a sequential control unit is started.
[0044]
The CPU 16 functioning as sequential control means first activates the CPU 16 functioning as sensor characteristic correction data acquisition means, operates the solenoid 22 via the input / output circuit 19 and the solenoid drive circuit 21, and closes only the external shutter 15. (Step a1) Further, an image acquisition command is sent to the infrared sensor 4 via the input / output circuit 19, and the input image signal 7 input via the amplifier 10 and the AD converter 11 and the input / output circuit 19 is read ( In step a2), this input image signal 7 is stored in the first frame memory 3 as sensor characteristic correction data Xa (step a3).
The waveform image of the sensor characteristic correction data Xa at this time is as shown in FIG. In addition, although the pixel arrangement on the infrared sensor 4 is actually two-dimensional, in FIG. 2A, for simplification of description, all the data of each pixel are shown side by side in the horizontal axis direction. The processing of step a1 to step a3 is processing corresponding to the sensor characteristic correction data acquisition step.
[0045]
Next, the CPU 16 operates the solenoid 22 via the input / output circuit 19 and the solenoid drive circuit 21 to open the external shutter 15 (step a4).
[0046]
Then, the CPU 16 functioning as the sequential control means activates the CPU 16 functioning as the internal shutter characteristic correction data acquisition means, operates the solenoid 24 via the input / output circuit 19 and the solenoid drive circuit 23, and closes the internal shutter 5. (Step a5), further, an image acquisition command is sent to the infrared sensor 4 via the input / output circuit 19, and the input image signal 7 input via the amplifier 10 and the AD converter 11 and the input / output circuit 19, that is, Then, the input image signal [Xa + Xb] reflecting the fixed pattern noise component Xa caused by variation in characteristics of each pixel of the infrared sensor 4 and the fixed pattern noise component Xb caused by temperature unevenness of the internal shutter 5 is read (step a6). ).
Next, the image signal Xa stored in the first frame memory 3 is subtracted from the input image signal 7 to eliminate the influence of the fixed pattern noise component Xa caused by the variation in characteristics of each pixel of the infrared sensor 4. The intermediate image signal 11, that is, the fixed pattern noise component Xb caused by the temperature unevenness of the internal shutter 5 is obtained (step a7), and this intermediate image signal 11 is stored in the second frame memory 6 as the internal shutter characteristic correction data Xb. (Step a8).
The waveform image of each signal at this time is as shown in FIG. The processing from step a5 to step a8 is processing corresponding to the internal shutter characteristic correction data acquisition step.
[0047]
In this way, when the first data update process for storing the internal shutter characteristic correction data Xb in the second frame memory 6 is completed, the CPU 16 functioning as the sequential control means updates the data in the second frame memory 6. The timer T1 for measuring the cycle is reset and restarted (step a9).
[0048]
Next, the CPU 16 functioning as a sequential control unit activates the CPU 16 functioning as a superimposition characteristic correction data acquisition unit, and again sends an image acquisition command to the infrared sensor 4 with the internal shutter 5 kept closed. Due to the input image signal 7 inputted through the AD converter 11 and the input / output circuit 19, that is, due to the fixed pattern noise component Xa caused by the variation in characteristics of each pixel of the infrared sensor 4 and the temperature unevenness of the internal shutter 5. The input image signal [Xa + Xb] superimposed with the fixed pattern noise component Xb to be read is read (step a10), and this input image signal 7 is stored in the first frame memory 3 as the superimposition characteristic correction data [Xa + Xb] (step a11). .
The waveform image of each signal at this time is as shown in FIG. The processing from step a10 to step a11 is processing corresponding to the superimposition characteristic correction data acquisition step.
[0049]
In this way, when the first data update process for storing the superimposition characteristic correction data [Xa + Xb] in the first frame memory 3 is completed, the CPU 16 functioning as the sequential control means stores the data in the first frame memory 3. The timer T2 for measuring the update cycle is reset and restarted (step a12).
[0050]
Next, the CPU 16 functioning as the sequential control means activates the CPU 16 functioning as the output data correction means, operates the solenoid 24 via the input / output circuit 19 and the solenoid drive circuit 23, and opens the internal shutter 5 (step). a13). Since the external shutter 15 has already been opened by the process of step a4, a normal imaging operation for imaging an external monitoring target is permitted when the process of step a13 is completed.
[0051]
Next, the CPU 16 functioning as a sequential control unit determines whether or not the measurement time of the timer T2 has reached the set value t2 (for example, 1 minute) of the data update period of the first frame memory 3 (step a14).
[0052]
If the measurement time of the timer T2 has not reached the set value t2, the CPU 16 functioning as a sequential control unit further sets the set time t1 (for example, the data update cycle of the second frame memory 6). It is determined whether or not (10 minutes) has been reached (step a15).
[0053]
If both the determination results of step a14 and step a15 are false, it is necessary to update neither the correction data in the first frame memory 3 nor the correction data in the second frame memory 6 at that time. This means that the CPU 16 functioning as output data correction means sends an image acquisition command to the infrared sensor 4 via the input / output circuit 19 and is input via the amplifier 10 and the AD converter 11 and the input / output circuit 19. The input image signal 7, that is, the input in which the data Xo of the true imaging scene depending on the temperature difference of the imaged monitoring target and the fixed pattern noise component Xa caused by the characteristic variation of each pixel of the infrared sensor 4 are superimposed. The image signal [Xo + Xa] is read (step a16).
Then, the superimposition characteristic correction data [Xa + Xb] stored in the first frame memory 3 is subtracted from the input image signal 7 to obtain an intermediate image signal 11, that is, [Xo−Xb] (step a 17). The internal shutter characteristic correction data Xb of the second frame memory 6 is added to the intermediate image signal 11 to obtain the final image signal 8, that is, the final image signal 8 comparable to the true imaging scene data Xo (step a18). The final image signal 8 is sent to the display device 14 via the input / output circuit 19 and displayed on the display device 14 (step a19).
The waveform image of each signal is as shown in FIG. The processing from step a16 to step a19 is processing corresponding to the output data correction step.
[0054]
Next, the CPU 16 functioning as a sequential control means determines whether or not the measurement time of the timer T2 has reached the set value t2 of the data update cycle of the first frame memory 3 (step a14), and further the measurement time of the timer T1. It is determined whether or not has reached the set value t1 of the data update period of the second frame memory 6 (step a15). As long as these determination results are both false, the process goes to steps a16 to a19. The process corresponding to the output data correction process is repeatedly executed every predetermined period Δt.
The predetermined period Δt is affected by the conversion period of the AD converter 11 and the processing capability of the CPU 16 itself, but is a period much shorter than the set value t2 and the set value t1 described above. As described above, the magnitude relationship between the set value t2 and the set value t1 is t1> t2, and Δt is much smaller than t2.
[0055]
While the process corresponding to the output data correction process is repeatedly executed in this way, it is determined by the determination process in step a14 that the measurement time of the timer T2 has reached the set value t2 of the data update cycle of the first frame memory 3. When detected, the CPU 16 functioning as the sequential control means starts up the CPU 16 functioning as the superimposition characteristic correction data acquisition means, and operates the solenoid 24 via the input / output circuit 19 and the solenoid drive circuit 23 to close the internal shutter 5. (Step a20), an image acquisition command is sent to the infrared sensor 4, and the input image signal 7 inputted through the amplifier 10, the AD converter 11 and the input / output circuit 19, that is, for each pixel of the infrared sensor 4. The fixed pattern noise component Xa caused by the variation in the characteristics of the internal shutter 5 and the fixed shutter noise caused by the temperature unevenness of the internal shutter 5 The input image signal [Xa + Xb] on which the pattern noise component Xb is superimposed is read (step a10), and this input image signal 7 is updated and stored as superimposition characteristic correction data [Xa + Xb] in the first frame memory 3 (step a10). a11) The timer T2 is reset again and restarted (step a12), the internal shutter 5 is opened again (step a13), and the normal imaging operation, that is, the process corresponding to the output data correction process is resumed. Allow.
Therefore, the superimposition characteristic correction data acquisition unit repeatedly operates every predetermined operation cycle t2 longer than the operation cycle Δt of the output data correction unit, and only the value of the superimposition characteristic correction data [Xa + Xb] in the first frame memory 3 is obtained. Will be updated.
[0056]
While the process corresponding to the output data correction process is repeatedly executed, the determination process in step a15 detects that the measurement time of the timer T1 has reached the set value t1 of the data update period of the second frame memory 6. Then, the CPU 16 functioning as a sequential control means, in the same manner as described above, sensor characteristic correction data acquisition means (function achieved by the processing of step a1 to step a3), internal shutter characteristic correction data acquisition means (steps a5 to a5). The function achieved by the process of step a8) and the superimposition characteristic correction data acquisition means (the function achieved by the process of step a10 to step a11) are sequentially activated, and the internal shutter characteristic correction data Xb in the second frame memory 6 is And the superimposition characteristic correction data [Xa + X in the first frame memory 3 is updated. After updating the value of], normal imaging operation, that is, will permit the resumption of processing corresponding to the output data correction process.
Therefore, these series of means are repeatedly operated every predetermined operation cycle t1 longer than the operation cycle t2 of the superimposition characteristic correction data acquisition means, and the value of the internal shutter characteristic correction data Xb in the second frame memory 6, and The value of the superimposition characteristic correction data [Xa + Xb] in the first frame memory 3 is updated substantially simultaneously.
[0057]
The above is the overall processing flow when the CPU 16 is used as the adder 12 or the subtractor 13.
[0058]
Here, while the process corresponding to the output data correction process is repeatedly executed, a temperature drift may occur in the infrared sensor 4 and the sensor characteristic correction data Xa may change to an appropriate value. Since the content of the correction data [Xa + Xb] in the frame memory 3 is repeatedly updated every operation period t2, the content of the item Xa related to the sensor characteristic correction data in the superposition characteristic correction data [Xa + Xb] It can be automatically updated to accommodate temperature drift.
In addition, the temperature unevenness of the internal shutter 5 itself may change and change to an appropriate value as the internal shutter characteristic correction data Xb. However, the content of the correction data Xb in the second frame memory 6 is also changed every operation cycle t1. Since it is repeatedly updated, the content of the internal shutter characteristic correction data Xb in the second frame memory 6 can be automatically updated in accordance with this even if the temperature unevenness of the internal shutter 5 itself fluctuates. it can.
In this manner, the value of the correction data [Xa + Xb] in the first frame memory 3 and the value of the correction data Xb in the second frame memory 6 are sequentially updated. As a result, the superimposition characteristic correction data in the first frame memory 3 is obtained. The value of the item Xb constituting a part of [Xa + Xb] and the value of the item Xb constituting the internal shutter characteristic correction data in the second frame memory 6 are substantially always the same value. It is possible to always appropriately output the monitoring target image signal Xo as the final image signal 8 by the arithmetic processing of the corresponding steps a17 and a18, that is, [Xo + Xa] − [Xa + Xb] + Xb.
[0059]
Next, with reference to FIGS. 6 to 8, the configuration and internal processing of the infrared imaging device 1 ′ and the fixed pattern noise correction device 2 ′ of another embodiment to which the fixed pattern noise correction method of the present invention is applied will be described in detail. explain.
[0060]
The fixed pattern noise correction device 2 ′ of this embodiment uses a timer To as an operation status detection means for detecting the operation status of the infrared imaging device 1 ′, and an elapsed time (operation status) after the operation of the infrared imaging device 1 ′. Accordingly, the value of the internal shutter characteristic correction data Xb in the second frame memory 6 is updated.
Therefore, the external shutter 15 used for obtaining the internal shutter characteristic correction data Xb in the embodiment of FIG. 4 is unnecessary, and instead, it corresponds to the elapsed time after the operation of the infrared imaging device 1 ′. A memory 25 is provided that stores internal shutter characteristic correction data Xb that is an image signal at the time of imaging the internal shutter.
Since other hardware configurations are substantially the same as those of the fixed pattern noise correction apparatus 2 shown in FIG. 4, the same reference numerals as those in FIG. 4 are given in FIG. Description is omitted.
[0061]
An example of data stored in the memory 25 is shown in FIG. In this example, the internal shutter characteristic correction data Xb1 is stored in correspondence with the increment of 0 to 5 minutes after the infrared imaging device 1 ′ is operated, and the elapsed time 5 after the infrared imaging device 1 ′ is operated. The internal shutter characteristic correction data Xb2 is stored in correspondence with the step size of 10 minutes to 10 minutes, and further, the internal shutter characteristic correction is performed in correspondence with the step size of 10 minutes to 20 minutes after the operation of the infrared imaging device 1 ′. The configuration of storing the data Xb3 is applied.
The step width of the elapsed time is gradually extended because the temperature unevenness of the internal shutter 5 is greatly changed for a while after the start of operation, and the change gradually converges to a certain time after the start of operation. It is assumed that the fixed pattern noise component caused by the temperature unevenness of the internal shutter 5 is saturated at the time when elapses, and does not change any more. The longest elapsed time stored in the memory 25 is determined based on the continuous usable time of the infrared imaging device 1 ′.
Although the contents of the image signals Xb1, Xb2, Xb3,... Of the internal shutter 5 experimentally imaged at each elapsed time are different from each other, for example, FIG. The internal shutter characteristic correction data Xb.
[0062]
Next, referring to the flowchart of FIG. 7 showing the internal processing executed by the CPU 16 ′ built in the fixed pattern noise correction apparatus 2 ′, the superimposition characteristic correction data acquisition means, the internal shutter characteristic correction data acquisition means, the output The processing operation of the CPU 16 ′ functioning as data correction means and sequential control means will be described in detail.
[0063]
When the infrared imaging device 1 ′ and the fixed pattern noise correction device 2 ′ are turned on by operating the operation panel 20, internal processing of the CPU 16 ′ functioning as a sequential control unit is started.
[0064]
The CPU 16 ′ functioning as the sequential control means first resets and restarts the timer To functioning as the operating condition detection means, and starts measuring the elapsed time after the start of the operation of the infrared imaging device 1 ′ (step b1). .
[0065]
Next, the CPU 16 ′ functioning as a sequential control unit activates the CPU 16 ′ functioning as an internal shutter characteristic correction data acquisition unit, operates the solenoid 24 via the input / output circuit 19 and the solenoid drive circuit 23, and the internal shutter 5. (Step b 2), and further, an image acquisition command is sent to the infrared sensor 4 via the input / output circuit 19, and the input image signal 7 input via the amplifier 10, the AD converter 11 and the input / output circuit 19. That is, the input image signal [Xa + Xb] reflecting the fixed pattern noise component Xa caused by the variation in characteristics of each pixel of the infrared sensor 4 and the fixed pattern noise component Xb caused by the temperature unevenness of the internal shutter 5 is read ( Step b3), the input image signal 7 is stored in the first frame memory 3 with the superimposition characteristic correction data [X + Xb] is stored as (step b4).
The waveform image of each signal at this time is as shown in FIG. The processing from step b2 to step b4 is processing corresponding to the superimposition characteristic correction data acquisition step.
[0066]
Next, the CPU 16 ′ functioning as the sequential control means activates the CPU 16 ′ functioning as the internal shutter characteristic correction data acquisition means, and reads the current value of the timer To functioning as the operation status detection means (step b5). Based on the time To, that is, the operating state of the infrared imaging device 1 ′, the memory 25 as shown in FIG. 8 is searched, and the internal shutter characteristic correction stored corresponding to the increment of the elapsed time including the elapsed time To is stored. The data Xb, in short, the internal shutter characteristic correction data Xb corresponding to the operating status of the infrared imaging device 1 ′ is specified, and the content is read from the memory 25 and stored in the second frame memory 6 (step b6). Therefore, for example, if the value of the elapsed time To is 1 minute, the internal shutter characteristic correction data Xb1 corresponding to the step size of 0 to 5 minutes is selected from the data of FIG. 8, and the correction data Xb1 is It is stored in the second frame memory 6 as Xb.
The processing from step b5 to step b6 is processing corresponding to the internal shutter characteristic correction data acquisition step.
[0067]
As described above, in the present embodiment, the data stored in the memory 25 is the content of the internal shutter characteristic correction data Xb that is appropriate at that time based on the value of the elapsed time To after the operation of the infrared imaging device 1 ′. Therefore, it is not necessary to calculate the internal shutter characteristic correction data Xb by performing pre-processing as shown in FIGS. 2A and 2B, and therefore the external shutter 15 is not required. It becomes.
[0068]
In this way, when the first data update process for storing the internal shutter characteristic correction data Xb in the second frame memory 6 is completed, the CPU 16 ′ functioning as the sequential control means performs the first frame memory 3 and the first frame memory 3 The timer T2 for measuring the data update period of the second frame memory 6 is reset and restarted (step b7).
[0069]
Thereafter, the CPU 16 ′ functioning as a sequential control means operates the solenoid 24 via the input / output circuit 19 and the solenoid drive circuit 23, opens the internal shutter 5 (step b8), and captures an image of an external monitoring target. The execution of the imaging operation is allowed.
[0070]
Next, the CPU 16 ′ functioning as a sequential control unit determines whether or not the measurement time of the timer T2 has reached the set value t2 (for example, 1 minute) of the data update period of the first frame memory 3 and the second frame memory 6. Is determined (step b9).
[0071]
If the measurement time of the timer T2 does not reach the set value t2, it means that neither the correction data in the first frame memory 3 nor the correction data in the second frame memory 6 needs to be updated at that time. The CPU 16 ′ functioning as output data correction means sends an image acquisition command to the infrared sensor 4 via the input / output circuit 19, and the input image input via the amplifier 10, the AD converter 11 and the input / output circuit 19. The input image signal in which the signal 7, that is, the true image scene data Xo depending on the temperature difference of the imaged monitoring target and the fixed pattern noise component Xa resulting from the variation in the characteristics of each pixel of the infrared sensor 4 is superimposed. [Xo + Xa] is read (step b10).
Then, the superimposition characteristic correction data [Xa + Xb] stored in the first frame memory 3 is subtracted from the input image signal 7 to obtain an intermediate image signal 11, that is, [Xo−Xb] (step b11). The internal shutter characteristic correction data Xb of the second frame memory 6 is added to the intermediate image signal 11 to obtain the final image signal 8, that is, the final image signal 8 comparable to the true imaging scene data Xo (step b12). The final image signal 8 is sent to the display device 14 via the input / output circuit 19 and displayed on the display device 14 (step b13).
The waveform image of each signal is as shown in FIG. The processing from step b10 to step b13 is processing corresponding to the output data correction process.
[0072]
Next, the CPU 16 ′ functioning as a sequential control means determines whether or not the measurement time of the timer T2 has reached the set value t2 of the data update period of the first frame memory 3 and the second frame memory 6. However (step b9), as long as both of the determination results are false, the process corresponding to the output data correction process from step b10 to step b13 is repeatedly executed every predetermined period Δt.
The predetermined period Δt is influenced by the conversion period of the AD converter 11 and the processing capability of the CPU 16 ′ itself, but is a period much shorter than the set value t2.
[0073]
While the processing corresponding to the output data correction process is repeatedly executed in this way, the measurement time of the timer T2 has reached the set value t2 of the data update period of the first frame memory 3 and the second frame memory 6. Is detected by the determination process of step b9, the CPU 16 ′ functioning as a sequential control unit and the superimposition characteristic correction data acquisition unit (functions achieved by the process of step b2 to step b4) The shutter characteristic correction data acquisition means (functions achieved by the processing of step b5 to step b6) is activated in order, and the value of the superimposition characteristic correction data [Xa + Xb] in the first frame memory 3 and the internal value in the second frame memory 6 After updating the value of the shutter characteristic correction data Xb, the normal imaging operation, that is, the output data correction process is performed. The corresponding process can be resumed.
Accordingly, these series of means are repeatedly operated every predetermined operation period t2 longer than the operation period Δt of the output data correction means, and the value of the superposition characteristic correction data [Xa + Xb] in the first frame memory 3 and the second The value of the internal shutter characteristic correction data Xb in the frame memory 6 is updated.
[0074]
The above is the overall processing flow when the timer To and the memory 25 are used as the operating condition detection means instead of the external shutter 15.
[0075]
Here, while the process corresponding to the output data correction process is repeatedly executed, a temperature drift occurs in the infrared sensor 4 to change an appropriate value as the sensor characteristic correction data Xa, or the temperature unevenness of the internal shutter 5 itself. May change to an appropriate value as the internal shutter characteristic correction data Xb, but as described above, the contents of the correction data [Xa + Xb] in the first frame memory 3 and the second frame memory 6 Since the contents of the correction data Xb are repeatedly updated every operation cycle t2, it is possible to always maintain these correction values at appropriate values and appropriately output the monitoring target image signal Xo as the final image signal 8. it can.
[0076]
Here, the timer for measuring the elapsed time after the operation of the infrared imaging device has been described as an example of the operating state detection means, but a temperature sensor for measuring the internal temperature of the infrared imaging device may be used instead of this timer. Good.
[0077]
An embodiment in which a temperature sensor is used will be briefly described with reference to FIGS.
[0078]
The fixed pattern noise correction device 2 ″ of FIG. 9 uses the temperature sensor 26 as an operation status detection means for detecting the operation status of the infrared imaging device 1 ″, and according to the internal temperature (operation status) of the infrared imaging device 1 ″. The value of the internal shutter characteristic correction data Xb in the second frame memory 6 is updated.
As shown in FIG. 9, the fixed pattern noise correction device 2 ″ includes a temperature sensor 26 installed in the vicinity of the internal shutter 5 and an image signal at the time of imaging the internal shutter corresponding to the internal temperature of the infrared imaging device 1 ″. A memory 25 ′ in which internal shutter characteristic correction data Xb is stored.
Since the other hardware configuration is substantially the same as that of the fixed pattern noise correction apparatus 2 ′ shown in FIG. 6, only the same reference numerals as those in FIG. 6 are given in FIG. Description of is omitted.
[0079]
An example of data stored in the memory 25 ′ is shown in FIG. In this example, the internal shutter characteristic correction data Xb1 ′, Xb2 ′, Xb3 ′,... Corresponding to each temperature range is stored with a step size of 10 ° C. The minimum and maximum temperature ranges stored in the memory 25 ′ are determined based on the usage environment of the infrared imaging device 1 ″.
Although the contents of the image signals Xb1 ′, Xb2 ′, Xb3 ′,... Of the internal shutter 5 experimentally imaged at each temperature are different from each other, for example, FIG. The internal shutter characteristic correction data Xb shown in FIG.
[0080]
The internal processing executed by the CPU 16 ″ incorporated in the fixed pattern noise correction apparatus 2 ″ is shown in the flowchart of FIG. As is clear from a comparison between FIG. 10 and FIG. 7, the flow of the processing operation as a whole is the same as that of the embodiment of FIG. However, in the embodiment of FIG. 10, there is no need to measure the elapsed time after the operation, so the processing corresponding to step b1 of FIG. 7 is not necessary.
[0081]
In the present embodiment shown in FIG. 10, the current value Ho of the internal temperature of the infrared imaging device 1 ″ detected by the temperature sensor 26 functioning as the operating condition detecting means is read (step c4), and this internal temperature Ho, that is, infrared rays is read. The internal shutter characteristic correction data Xb stored in correspondence with the step size of the temperature including the internal temperature Ho is searched by searching the memory 25 ′ as shown in FIG. Therefore, the internal shutter characteristic correction data Xb corresponding to the operating state of the infrared imaging device 1 ″ is specified, and the content is read from the memory 25 ′ and stored in the second frame memory 6 (step c5). For example, if the value of the internal temperature Ho of the infrared imaging device 1 ″ is 15 ° C., the step size is 10 ° C. to 20 ° C. from the data in FIG. 'Is selected, the correction data Xb3' internal shutter characteristic correction data Xb3 to respond will be stored in the second frame memory 6 as a value corresponding to Xb.
[0082]
Other processes are the same as those in the embodiment described with reference to FIG.
[0083]
【The invention's effect】
The fixed pattern noise correction method and the fixed pattern noise correction apparatus for an infrared imaging device according to the present invention are an image signal that represents luminance unevenness due to variation in characteristics of each pixel of the infrared sensor and an image signal that represents temperature unevenness of the internal shutter itself. Are stored as superimposition characteristic correction data in the first frame memory, and only the image signal representing the temperature irregularity of the internal shutter itself is stored as internal shutter characteristic correction data in the second frame memory. The superimposition characteristic correction data stored in the first frame memory is subtracted from the input image signal output from the infrared sensor with the influence of the characteristic variation for each pixel, and the second frame memory By adding the stored internal shutter characteristic correction data, the characteristics of each pixel of the infrared sensor can be varied. Because the influence of the uneven brightness and the temperature unevenness of the internal shutter itself are removed, the internal environment that always generates the infrared incident environment without being affected by the temperature unevenness of the internal shutter itself and its fluctuations. An appropriate final image signal can be obtained by effectively using the shutter.
[0084]
Further, when updating the superimposition characteristic correction data of the first frame memory or the internal shutter characteristic correction data of the second frame memory, the second frame memory is compared with the update period of the superimposition characteristic correction data in the first frame memory. Since the update cycle of the internal shutter characteristic correction data in the frame memory is made longer, the external shutter can be used even when an apparatus configuration that requires imaging of the external shutter when updating the internal shutter characteristic correction data is applied. Compared with the conventional fixed pattern noise correction method and fixed pattern noise correction apparatus that have acquired data required for correction only by imaging, the number of imaging of the external shutter can be reduced, and the trouble of external shutter operation is reduced. Is reduced.
Further, by updating the superimposition characteristic correction data of the first frame memory and the internal shutter characteristic correction data of the second frame memory in this way, the variation in characteristics of each pixel that changes due to the temperature drift of the infrared sensor or the like. It is possible to cope with the change in temperature and the variation in temperature unevenness of the internal shutter itself, and to obtain a more appropriate final image signal.
[0085]
In addition, an operation status detection means for detecting an elapsed time after operation related to the operation status of the infrared imaging device, an internal temperature of the device, and the like, and an image signal at the time of imaging an internal shutter that varies depending on the operation status of the infrared imaging device A memory stored in correspondence with the operating status of the device, and a configuration for identifying and updating correction data in the second frame memory by searching the memory based on the operating status of the device detected by the operating status detecting means In this case, it is not necessary to image an external shutter to obtain correction data to be stored in the second frame memory, so that the external shutter of the infrared imaging device is not necessary, and the trouble of the external shutter operation is reduced. In addition to the elimination, the portability of the infrared imaging device is also improved.
[0086]
As described above, the second frame memory for storing the internal shutter characteristic correction data for correcting the fixed pattern noise component due to the uneven temperature of the internal shutter is provided independently, and only this internal shutter characteristic correction data is stored. Since the optimization was performed in a timely manner through the update operation, even when using a small internal shutter built into the infrared imaging device, the fixed pattern noise is almost as accurate as when using a large external shutter outside the device. An unprecedented excellent effect was obtained, such as being able to correct.
[Brief description of the drawings]
FIG. 1 is a conceptual diagram showing an outline of a configuration of an infrared imaging device according to an embodiment to which a fixed pattern noise correction method of the present invention is applied.
FIG. 2 is an operation principle diagram showing an outline of an operation of a fixed pattern noise correction device provided in the infrared imaging device of the embodiment, and FIG. 2A illustrates a process of a sensor characteristic correction data acquisition step; 2B shows the process of the internal shutter characteristic correction data acquisition process, and FIG. 2C shows the process of the superimposition characteristic correction data acquisition process.
FIG. 3 is an operational principle diagram showing an outline of the operation of the fixed pattern noise correction apparatus according to the embodiment, showing a process of an output data correction process;
FIG. 4 is a functional block diagram showing a specific configuration of the fixed pattern noise correction apparatus according to the embodiment;
FIG. 5 is a flowchart showing internal processing executed by a CPU provided in the fixed pattern noise correction apparatus according to the embodiment;
FIG. 6 is a functional block diagram showing a specific configuration of a fixed pattern noise correction apparatus according to another embodiment to which the fixed pattern noise correction method of the present invention is applied.
FIG. 7 is a flowchart showing internal processing executed by a CPU provided in the fixed pattern noise correction apparatus according to the embodiment;
FIG. 8 is a conceptual diagram showing an outline of a memory built in the fixed pattern noise correction apparatus of the embodiment;
FIG. 9 is a functional block diagram showing a specific configuration of a fixed pattern noise correction apparatus according to still another embodiment to which the fixed pattern noise correction method of the present invention is applied.
FIG. 10 is a flowchart showing internal processing executed by a CPU provided in the fixed pattern noise correction apparatus according to the embodiment;
FIG. 11 is a conceptual diagram showing an outline of a memory built in the fixed pattern noise correction apparatus of the embodiment.
[Explanation of symbols]
1 Infrared imaging device
1 'Infrared imaging device
1 "infrared imaging device
2 Fixed pattern noise correction device
2 'Fixed pattern noise correction device
2 "fixed pattern noise correction device
3 First frame memory
4 Infrared sensor
5 Internal shutter
6 Second frame memory
7 Input image signal
8 Final image signal
9 Optical system
10 Amplifier
11 Intermediate image signal
12 Subtractor
13 Adder
14 Display device
15 External shutter
16 CPU (sensor characteristic correction data acquisition means, internal shutter characteristic correction data acquisition means, superimposition characteristic correction data acquisition means, output data correction means, sequential control means)
16 'CPU (superimposition characteristic correction data acquisition means, internal shutter characteristic correction data acquisition means, output data correction means, sequential control means)
16 "CPU (superimposition characteristic correction data acquisition means, internal shutter characteristic correction data acquisition means, output data correction means, sequential control means)
17 ROM
18 RAM
19 I / O circuit
20 Operation panel
21 Solenoid drive circuit
22 Solenoid
23 Solenoid drive circuit
24 Solenoid
25 memory
25 'memory
26 Temperature sensor (operation status detection means)
To timer (operation status detection means)

Claims (10)

This is a fixed pattern noise correction method for an infrared imaging device in which an image formed on an infrared sensor through an optical system is converted into an image signal, corrected to remove fixed pattern noise, and then output as a final image signal. And
An image is captured in a state where an internal shutter provided inside the infrared imaging device is opened and an external shutter provided outside the infrared imaging device is closed, and an input image signal obtained by capturing the image is obtained. After executing the sensor characteristic correction data acquisition process stored in the first frame memory,
Image capture is performed with the internal shutter closed, and the image signal stored in the first frame memory is subtracted from the input image signal obtained by capturing the image and stored in the second frame memory. Executing an internal shutter characteristic correction data acquisition step
Further, an image capturing process is performed again with the internal shutter closed, and an input characteristic signal obtained by capturing the image is updated and stored in the first frame memory. ,
After that, image capture is executed every predetermined cycle with the internal shutter and the external shutter opened, and each time, the input image signal obtained by capturing the image of the cycle is stored in the first frame memory. Infrared imaging characterized by repeatedly executing an output data correction step of subtracting the image signal being added and adding the image signal stored in the second frame memory and outputting as a final image signal Fixed pattern noise correction method for the apparatus. The superposition characteristic correction data acquisition step is repeatedly executed at predetermined intervals longer than the predetermined cycle of the output data correction step, and the sensor characteristic correction data acquisition step, the internal shutter characteristic correction data acquisition step, and the superposition characteristic correction 2. The fixed pattern noise correction method for an infrared imaging device according to claim 1, wherein the processing including the data acquisition step is repeatedly executed at predetermined intervals longer than the predetermined cycle of the superimposition characteristic correction data acquisition step. This is a fixed pattern noise correction method for an infrared imaging device in which an image formed on an infrared sensor through an optical system is converted into an image signal, corrected to remove fixed pattern noise, and then output as a final image signal. And
An operating condition detecting means for detecting an operating condition of the infrared imaging device is provided, and an image signal at the time of internal shutter imaging that varies according to the operating condition of the infrared imaging device is previously associated with the operating condition of the infrared imaging device. Store in the memory of the infrared imaging device,
A superimposition characteristic correction data acquisition step of capturing an image in a state in which an internal shutter provided in the infrared imaging device is closed, and storing an input image signal obtained by capturing the image in a first frame memory; ,
After executing an internal shutter characteristic correction data acquisition step of retrieving an image signal at the time of internal shutter imaging corresponding to the operation status detected by the operation status detection means from the memory and storing it in a second frame memory,
The image is captured every predetermined cycle with the internal shutter opened, and each time, the image signal stored in the first frame memory is subtracted from the input image signal obtained by capturing the image of the cycle. And a fixed pattern noise correction method for an infrared imaging device, wherein an output data correction step of adding the image signals stored in the second frame memory and outputting as a final image signal is repeatedly executed. . The infrared imaging device according to claim 3, wherein the superimposition characteristic correction data acquisition step and the internal shutter characteristic correction data acquisition step are repeatedly executed at a predetermined cycle longer than a predetermined cycle of the output data correction step. Fixed pattern noise correction method. 5. The fixed pattern noise correction method for an infrared imaging device according to claim 3, wherein the operating state is an elapsed time after the infrared imaging device is operated. 5. The fixed pattern noise correction method for an infrared imaging device according to claim 3, wherein the operating state is an internal temperature of the infrared imaging device. A fixed pattern noise correction device for an infrared imaging device that converts an image formed on an infrared sensor through an optical system into an image signal, removes fixed pattern noise, and outputs it as a final image signal,
An openable / closable internal shutter provided inside the infrared imaging device, an openable / closable external shutter provided outside the infrared imaging device, first and second frame memories for storing image signals,
Sensor characteristic correction data acquisition means for storing an input image signal acquired from the infrared sensor in a state where the internal shutter is opened and the external shutter is closed;
Acquisition of internal shutter characteristic correction data stored in the second frame memory by subtracting the image signal stored in the first frame memory from the input image signal acquired from the infrared sensor with the internal shutter closed Means,
Superimposition characteristic correction data acquisition means for storing, in the first frame memory, an input image signal acquired from the infrared sensor with the internal shutter closed;
Obtaining an input image signal from the infrared sensor at predetermined intervals with the internal shutter and the external shutter opened, subtracting the image signal stored in the first frame memory from the input image signal; and Output data correction means for adding the image signal stored in the second frame memory and outputting as a final image signal;
The superimposition characteristic correction data acquisition means is operated repeatedly every predetermined operation cycle longer than the operation cycle of the output data correction means, and the sensor characteristic correction data acquisition means, the internal shutter characteristic correction data acquisition means, and the superposition The characteristic correction data acquisition means is arranged in the order of sensor characteristic correction data acquisition means, internal shutter characteristic correction data acquisition means, and superimposition characteristic correction data acquisition means for each predetermined operation cycle longer than the operation cycle of the superimposition characteristic correction data acquisition means. And a fixed pattern noise correction device characterized by comprising a sequential control means for repeatedly operating. A fixed pattern noise correction device for an infrared imaging device that converts an image formed on an infrared sensor through an optical system into an image signal, removes fixed pattern noise, and outputs it as a final image signal,
An openable / closable internal shutter provided inside the infrared imaging device, first and second frame memories for storing image signals, an operating status detecting means for detecting an operating status of the infrared imaging device, and the infrared A memory that stores in advance an image signal at the time of internal shutter imaging that fluctuates according to the operating status of the imaging device in association with the operating status of the infrared imaging device;
Superimposition characteristic correction data acquisition means for storing, in the first frame memory, an input image signal acquired from the infrared sensor with the internal shutter closed;
Internal shutter characteristic correction data acquisition means for retrieving an image signal at the time of internal shutter imaging corresponding to the operation situation detected by the operation situation detection means from the memory and storing it in a second frame memory;
An input image signal is obtained from the infrared sensor at predetermined intervals with the internal shutter opened, the image signal stored in the first frame memory is subtracted from the input image signal, and the second Output data correction means for adding the image signals stored in the frame memory and outputting as a final image signal;
And a sequential control unit that repeatedly operates the superimposition characteristic correction data acquisition unit and the internal shutter characteristic correction data acquisition unit at predetermined operation cycles longer than the operation cycle of the output data correction unit. Fixed pattern noise correction device. 9. The fixed pattern noise correction apparatus according to claim 8, wherein the operating state detection means is constituted by a timer that measures an elapsed time after the infrared imaging apparatus is operated. 9. The fixed pattern noise correction apparatus according to claim 8, wherein the operating state detection means is constituted by a temperature sensor that measures an internal temperature of the infrared imaging device.

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