JP4140394B2 - Imaging correction apparatus and imaging apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an imaging correction apparatus and an imaging apparatus.
[0002]
[Prior art]
The conventional imaging correction device has a normal correction method in which correction is performed by inserting an image correction shutter in front of the lens at the time of correction, and the visual axis is directed to something that seems to have uniform brightness (for example, “sky”). There is a method called “defocus calibration” in which correction is performed in a state where the focus of the lens is blurred. (For example, see Patent Document 1)
[0003]
[Patent Document 1]
Japanese Patent Laid-Open No. 10-142065 (Prior Art, Paragraph 6)
[0004]
[Problems to be solved by the invention]
As a conventional technique, a normal correction method in which correction is performed by inserting an image correction shutter and the above-described defocus calibration method are representative, but correction is performed with luminance as close to the imaging target as possible. Therefore, defocus calibration is excellent if a scene with almost uniform luminance can be obtained. However, the direction in which a scene with almost uniform brightness can be obtained differs depending on the situation. When a person must search for such a scene and make corrections by pointing the imaging device in that direction, an operator is required. (2) A display device is required for the operator to check in real time whether or not the imaging device is correctly oriented in a direction that seems to have uniform luminance. For this reason, for example, even when the imaging device is a monitoring device, the device cannot be completely automated, and there is a problem that the display device for the correction operator is increased in size.
[0005]
Also, when correcting by defocus calibration, if a scene with almost uniform brightness is not always obtained, the brightness change of the scene remains even if the lens focus is blurred, and correction processing is performed based on this There is a problem that the afterimage of the scenery at the time of correction remains as if burned in the corrected image.
[0006]
The present invention has been made to solve the above problems, and an object thereof is to automatically perform appropriate correction by selecting a good scenery and selecting a correction method.
[0007]
[Means for Solving the Problems]
An imaging correction apparatus according to the present invention includes an image processor that analyzes uniformity of an image signal, a main controller that outputs a correction timing signal from the output of the image processor, and variations in the image signal due to the correction timing signal. And a correction processor for correcting.
[0008]
An imaging apparatus according to the present invention includes an optical imager having a focus adjustment mechanism, a detector that converts an image formed by the optical imager into an electric signal, and the optical imager. A movable gantry that changes the light receiving direction, a correction processor that corrects variations in the signal of the detector, an image processor that analyzes the uniformity of the output signal of the correction processor, and an analysis result of the image processor To the movable gantry, the optical imager, and a main controller for controlling the correction processor.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Embodiment 1.
1 is a block diagram showing Embodiment 1 of the present invention.
1 is incident light, 2 is an optical imager, 3 is a detector that photoelectrically converts an image formed by the optical imager 2, 4 is a coarse image signal output by the detector 3, and 5 is optical. A movable frame on which the image forming device 2 and the detector 3 are mounted, 6 is a correction processor for correcting the coarse image signal 4, and 7 is a device for correcting the elements of the detector 3 necessary for the correction processing of the correction processor 6. A database storing data, 8 is an image signal output from the correction processor 6, 9 is an image processor for analyzing the characteristics of the image signal 8 as an image, 10 is an image analysis result output from the image processor 9, and 11 is The main controller 12 is a visual axis direction command for moving the movable frame 5 to obtain a desired imaging direction, 13 is a focus amount command for controlling the focusing state of the optical imager 2, and 14 is a correction process. This is a database update command for causing the device 6 to acquire a reference image for correction.
[0010]
During normal imaging, the incident light 1 is focused on the detector 3 by the optical imager 2. The detector 3 has a plurality of photoelectric conversion elements arranged in a plane, and converts an image formed on the photoelectric conversion elements into an electrical signal. Depending on the structure of the detector, some photoelectric conversion elements are arranged in a straight line, but in that case, it is the same as the case where photoelectric conversion elements are arranged in a plane by using a mechanism that scans the formed image. The effect of can be obtained.
[0011]
In any method, the detector 3 outputs the coarse image signal 4 by outputting the electrical signals of the plurality of photoelectric conversion elements in a certain order. Usually, since the characteristics of the plurality of photoelectric conversion elements are slightly different from each other, even if the same number of photons is received on the surface of the photoelectric conversion element, electric signals having the same intensity are not obtained. In addition, the brightness on the imaging surface varies depending on the performance of the optical imager 2, and in particular when the imaging target wavelength band is infrared, the brightness difference on the imaging surface is affected by the influence of infrared radiation of each part of the apparatus. I will create it. Therefore, noise is always mixed in the coarse image signal 4. In particular, when imaging with high sensitivity, noise becomes significant.
[0012]
Therefore, the coarse image signal 4 is appropriately corrected by the correction processor 6 using the database 7 to obtain the image signal 8. The database 7 is a parameter database for the correction processor 6 to correct the signal of each photoelectric conversion element so that the coarse image signal 4 becomes flat when a uniform landscape is captured.
Since the characteristics of each photoelectric conversion element may change with the passage of time or may change with the turning on / off of the power supply, the database 7 is turned on, after a certain time during operation, or when the image signal 8 is deteriorated. Need to be updated. In this case, a uniform landscape is required, and the correction processor 6 becomes a reference data by sending a database update command 14 from the main controller 11 to the correction processor 6 in a state where the uniform landscape is imaged. The correction parameters are calculated based on the above, and the database 7 is updated to complete the correction.
[0013]
In general, a truly uniform landscape is hard to find in a normal landscape. Nearly uniform scenery includes the sky without clouds, or the sky covered with clouds, the sea, asphalt roads, walls, etc., but there are fine patterns except for the sky without clouds, which is not uniform. . Therefore, before sending the database update command 14 to the correction processor 6, a focus amount command 13 is sent from the main controller 11 to the optical image forming device 2, and the uniform image is erased by blurring the focus to the fullest extent. obtain. Such defocusing is called “defocusing”, and a method of performing correction by this is called defocusing calibration.
[0014]
However, even after defocusing, a large pattern, in other words, a pattern with a low spatial frequency cannot be erased. Therefore, as a characteristic mechanism that was not found in the prior art of this embodiment, the following operation is performed before defocus calibration is started. That is, the visual axis direction command 12 is sent from the main controller 11 to the movable gantry 5 so that the movable gantry 5 is scanned within the area where the movable gantry 5 is to be imaged, the periphery thereof, or the area where the movable gantry 5 moves. The image capturing direction is changed by moving the image without moving. Next, the image signal 8 obtained in the meantime is analyzed by the image processor 9 to measure the magnitude of the low spatial frequency component in the image signal. The magnitude of the low spatial frequency component can be obtained by first calculating a variance value of the image signal from which the high spatial frequency component disappears by applying a simple low-pass filter by averaging the image signal in a certain region. Then, as soon as it falls below a certain value, the image capturing direction is directed to that direction, thereby obtaining an optimal scene for correction. Alternatively, there is a case where the imaging direction is directed to a direction in which this value becomes minimum after imaging the entire region.
[0015]
By doing so, the uniformity of the correction scenery after defocusing can be increased and the influence of the afterimage of the correction scenery in the corrected image can be reduced as compared with the case where the defocus calibration is simply performed.
[0016]
Here, for the magnitude of the low spatial frequency component of the image signal, for example, fast Fourier transform is performed at a spatial frequency equal to or lower than a preset threshold frequency, and the signal intensity obtained thereby is integrated with respect to the frequency. Obtainable.
[0017]
Thus, by using the spatial frequency for the analysis of the image uniformity, the influence of the high spatial frequency component can be eliminated and the amount of the low spatial frequency component can be accurately measured. In general, there are many image processes using Fourier transform. In such a case, the entire processing load can be reduced by sharing the process of the Fourier transform unit.
[0018]
The same effect as defocusing can be obtained by moving the movable gantry 5 at high speed instead of defocusing to create a camera shake state. Of course, it may be used together with defocus, and in this case, there is an effect of increasing blur.
[0019]
As for a method for searching for an optimal scenery, for example, in the case where the imaging device captures a certain area while periodically changing the imaging direction, an optimal scenery for correction is preliminarily determined in the periodic operation. You can look for it. In addition, in the case of an imaging device that changes the imaging direction systematically only for correction and searches for an optimal scene for correction, the imaging processor 9 can change the imaging direction while keeping the focus blurred. The frequency component extraction function can be reduced. This is because the blurring itself is equivalent to the extraction of low spatial frequency components. Thereby, cost reduction and size reduction can be realized.
[0020]
Further, in the analysis of the spatial frequency in the image signal by the image processor 9, signal strength is obtained in several frequency bands, a frequency where the signal strength exceeds a certain magnitude is obtained, and the frequency band beyond that is blurred. In this way, by sending the focus amount command 13 to the optical imager 2 in advance, the focus blurring amount of the optical imager 2 becomes smaller when the uniformity of the scenery is high, such as in a clear sky. Alternatively, correction can be performed without blurring. When the focus is greatly blurred, the image plane specific illuminance changes, or when the imaging target wavelength band is infrared, the amount of irradiating infrared radiation from the lens barrel called shading changes. Although this is a negative effect, the negative effect can be reduced by optimally adjusting the focus blur amount as described above.
[0021]
In addition, when the captured image is a color image, it cannot be used as a correction image even in a low-spatial frequency component in a landscape composed of only one color or only two colors. Thus, by allowing the image processor 9 to measure the intensity of each color, it is possible to select a landscape having a color suitable for correction as well as the magnitude of the low spatial frequency component.
[0022]
Embodiment 2.
FIG. 2 is a block diagram showing Embodiment 2 of the present invention.
Reference numeral 15 denotes a shutter. Reference numeral 16 denotes a shutter opening / closing command for inserting and removing the shutter 15 in front of the optical imager 2.
As shown in FIG. 2, the shutter 15 is added to the first embodiment, and the magnitude of the low spatial frequency component of the image signal 8 obtained by the image processor 9 is not less than a certain magnitude. Since it is considered that good correction cannot be performed in the defocus calibration, the main controller 11 sends a shutter open / close command 16 to the shutter 15 to insert the shutter for correction.
In this case, the focus may not be blurred.
[0023]
The shutter 15 may be a translucent plate such as frosted glass, or may be a black body plate controlled at a constant temperature when the imaging target wavelength band is infrared. The shutter may be inserted in the middle of the optical path in the optical imager 2 or between the optical imager 2 and the detector 3.
When a semi-transparent plate is used as the shutter, the brightness of the scene to be imaged is reflected, so that a good effect close to defocus calibration can be obtained.
[0024]
In this way, correction can be performed regardless of the surrounding scenery environment, and if correction is required periodically, correction is not made with an inappropriate correction landscape.
[0025]
Embodiment 3.
FIG. 3 is a block diagram showing Embodiment 3 of the present invention.
17 is an altimeter, 18 is altitude information output by the altimeter 17, 19 is an attitude angle meter, 20 is attitude angle information output by the attitude angle meter 19, 21 is a position measuring device that measures the position of the imaging device, and 22 is position measurement The position information output by the device 21, 23 is a map database, 24 is map information output by the map database 23, 25 is a clock, and 26 is time / date information output by the clock 25.
The third embodiment is a development of the first embodiment relating to an imaging apparatus attached to a moving platform, such as an aircraft, and is intended to shorten the time required to obtain a scene suitable for correction. The main controller 11 determines an imaging direction search pattern for obtaining a scene suitable for correction based on the altitude information 18, the attitude angle information 20, the position information 22, and the map information 24.
[0026]
Specifically, when the altitude obtained by the altitude information 18 is equal to or higher than a certain altitude, the main controller 11 uses the attitude angle obtained from the attitude angle information 20 to direct the imaging direction toward the zenith direction. The setting angle of the movable gantry 5 is calculated, the imaging direction is moved from the high elevation angle as close to the zenith as possible within the movable range to the low elevation angle, and the magnitude of the low spatial frequency component in the image signal 8 indicated by the image analysis result 10 is calculated. The defocus calibration is performed immediately when the value becomes below a certain level.
[0027]
In this way, a scene suitable for correction can be found at high speed. This is because, at high altitudes, it is very likely that a cloudless sky will be obtained from the horizon to the zenith, and in most cases, a scene suitable for correction can be obtained with the first one shot. Note that the attitude angle information 20 includes the direction in which it is facing on an east-west-north-north-north basis (this is referred to as an azimuth angle), and the sun direction relative to itself can be calculated from this information and the time-date information 26. Do not face this direction.
[0028]
Similarly, if it is determined that the position obtained by the position information 22 is maritime compared with the map information 24, or if it is determined that it is on the snow or ice compared with the time date information 26, the attitude The set angle of the movable base 5 for directing the imaging direction to the snow or ice direction is calculated using its own posture angle obtained from the angle information 20, and the imaging direction is set within a movable range from a low elevation angle that is as close as possible to the direct downward direction. The defocus calibration is performed immediately when the magnitude of the low spatial frequency component in the image signal 8 indicated by the image analysis result 10 becomes equal to or less than a certain level.
[0029]
In this way, a scene suitable for correction can be found at high speed. This is because a low-spatial frequency component in the image is usually small on the surface of the sea or on the snow, and it is highly likely that a scene suitable for correction can be obtained. In addition, since the sun direction with respect to oneself can be calculated from the attitude angle information 20 and the time date information 26, the azimuth angle of the imaging direction is prevented from being directed in this direction. This is because sunlight is reflected strongly on the sea surface or on snow, and the brightness increases in a band shape from a low elevation angle toward the horizon, and correct correction cannot be performed in this direction.
[0030]
Of course, the above-described imaging direction search pattern based on altitude and the imaging direction search pattern based on position and time can also be used in combination. When both conditions are met, the direction in which the imaging device captures the image for the original purpose is calculated from the set angle and attitude angle information 20 of the movable gantry 5, and if it is above the horizon, the imaging direction search pattern by altitude If the position is below the horizon, the image direction search pattern based on position and time is preferentially selected. This is because a better correction can be made by performing correction at a luminance close to the area where the image is actually captured.
[0031]
Embodiment 4.
FIG. 4 is a block diagram showing Embodiment 4 of the present invention.
27 is a tuner that synchronizes the operations of the movable gantry 5 and the correction processor 6, 28 is a correction start signal, 29 is angle information indicating the directivity direction of the movable gantry 5, and 30 is a timing signal when performing correction processing step by step. It is.
The tuner 27 receives the correction start signal 28 and starts processing, and outputs a timing signal 30 every time the movable gantry 5 obtained from the angle information 29 moves by a certain angle. Each time the correction processor 6 receives the timing signal 30, it records a part of the image signal 8.
[0032]
FIG. 5 explains the operation of the apparatus in the fourth embodiment.
Reference numeral 31 denotes an image at a certain point in time, which is an image in the imaging direction with the smallest low spatial frequency component in the surrounding scenery. Reference numeral 32 denotes a cloud, and the image 31 includes an image in the imaging direction in which the low spatial frequency component is minimized. However, since the image 31 includes this cloud, the low spatial frequency component does not fall below a certain value, and the image has good quality for correction. It is not. 33 is the angle step, 34 is the next image when the imaging direction has moved to the left by the angle step 33 from the time of the image 31, and 35 is the imaging direction further moved to the left by the angle step 33 from the time of the next image 34. One after another at the time, 36 is a correction image created inside the correction processor 6, 37 is a part of the image 31, and is captured as a part of the correction image 36 by the timing signal 30, and is sent to the angle step 33. Regions A and 38 having a corresponding width are a part of the next image 34, captured as a part of the correction image 36 by the timing signal 30, and regions B and 39 having a width corresponding to the angle step 33 are the images 35 one after another. A region that is captured as a part of the correction image 36 by the timing signal 30 and has a width corresponding to the angle step 33 40 is a region D is a sequence of one row of pixels constituting the horizontal correction image 36.
[0033]
As described above, the correction processor 6 sequentially captures the region A37, the region B38, the region C39, etc. one after another by the timing signal 30 output from the tuner 27 every time the movable mount 5 moves to the left by a certain angle, and finally A correction image 36 is generated inside. In FIG. 5, the correction image 36 is particularly jagged on the lower side, but by defocusing sufficiently and adjusting the setting value of the angle step 33, the actual image becomes an image consisting only of horizontal lines without jaggedness. For example, the region D40 is a region composed of an array of pixels in a horizontal row, and the signals in this column are as shown in FIG. 41 is an ideal signal that should be originally obtained when an image is generated by the above method, and 42 is an actual signal. That is, it is only necessary to correct the actual signal 42 so as to be flat, whereby a correction database for all lines in the horizontal direction can be created. As the next step, if the same processing is performed with the angle step set to the vertical, the vertical direction can be corrected. As a result, the entire screen can be corrected.
[0034]
Such a method makes it possible to perform correction even when a uniform landscape suitable for correction cannot be obtained.
[0035]
Note that, by taking the angle step 33 finely and corresponding to one pixel in the horizontal direction, although it takes time to obtain the correction image 36, correction can be performed without defocusing.
[0036]
【The invention's effect】
As described above, according to the present invention, it is possible to prevent correction using an image having no uniformity by searching for a scene having a small low spatial frequency component before performing defocus calibration.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing a configuration of an imaging correction apparatus according to Embodiment 1 of the present invention.
FIG. 2 is a block diagram showing a configuration of an imaging correction apparatus according to Embodiment 2 of the present invention.
FIG. 3 is a block diagram showing a configuration of an imaging correction apparatus according to Embodiment 3 of the present invention.
FIG. 4 is a configuration diagram showing the configuration of an imaging correction apparatus according to Embodiment 4 of the present invention.
FIG. 5 is a diagram for explaining a correction image generation method in an imaging correction apparatus according to Embodiment 4 of the present invention;
FIG. 6 is a view for explaining pixel signal strengths in a horizontal row of a correction image in an imaging correction apparatus according to Embodiment 4 of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Incident light 2 Optical imager 3 Detector 4 Coarse image signal 5 Movable mount 6 Correction processor 7 Database 8 Image signal 9 Image processor 10 Image analysis result 11 Main controller 12 Visual axis direction command 13 Focus amount command 14 Database update command 15 Shutter 16 Shutter opening / closing command 17 Altimeter 18 Altitude information 19 Attitude angle meter 20 Attitude angle information 21 Position measuring device 22 Position information 23 Map database 24 Map information 25 Clock 26 Time date information 27 Tuner 28 Correction start signal 29 Angle Information 30 Timing signal 31 Image 32 Cloud 33 Angle step 34 Next image 35 Next image 36 Correction image 37 Region A
38 Area B
39 Area C
40 Area D
41 Ideal signal 42 Real signal

Claims (10)

A detector that converts light incident from the outside into an electrical signal and outputs a coarse image signal;
A correction processor for correcting the coarse image signal output from the detector using correction data and outputting an image signal;
An image processor that analyzes the luminance uniformity of the image using the spatial frequency of the image signal output from the correction processor, and outputs an image analysis result;
Based on the image analysis result output from the image processor, a main controller that outputs an update command for the correction data;
An imaging correction apparatus comprising:
When the correction processor receives an update command output from the main controller, the correction processor updates the correction data to image data having a uniform brightness and takes in the coarse image signal using the correction data. to correct
An imaging correction apparatus characterized by the above. The imaging correction apparatus according to claim 1, wherein fast Fourier transform is used for analysis of the spatial frequency. An optical imager having a focus adjustment mechanism;
A detector that converts an image imaged by the optical imager into an electrical signal;
A movable frame for changing the light receiving direction of the optical imager;
A correction processor for correcting variations in the signal of the detector;
An image processor for analyzing the uniformity of the output signal of the correction processor;
An imaging apparatus comprising: the movable gantry, the optical imager, and a main controller that controls the correction processor to capture uniform correction data from the analysis result of the image processor. The imaging apparatus according to claim 3, wherein a spatial frequency is used for the uniformity analysis. The imaging apparatus according to claim 4, wherein a blurring amount of the optical imager is adjusted according to the spatial frequency. The imaging apparatus according to claim 3, wherein a variation correction shutter is provided on a front surface of the optical imager. The imaging apparatus according to claim 3, further comprising a uniformity calculator that calculates a direction in which a scene with high uniformity can be obtained with high probability. The imaging apparatus according to claim 7, wherein a direction in which the highly uniform background can be obtained with high probability is calculated from altitude, posture angle, position, and time. The imaging device according to claim 8, further comprising a map database. The imaging apparatus according to claim 3, further comprising a tuner that synchronizes operations of the movable base and the correction processor.

Images