Magnification chromatic aberration correction circuit, magnification chromatic aberration correction method, and magnification chromatic aberration correction program

Abstract

This technology provides automatic correction of chromatic aberration. [Solution] The chromatic aberration correction circuit 1 includes a control unit 11 that controls the focal length, an imaging unit 12 that captures a test image at the focal length, a test image detection unit 13 that detects a first test image and a second test image from a first color signal and a second color signal obtained from the video signal of the test image, respectively, a chromatic aberration detection unit 14 that detects the chromatic aberration of the second test image relative to the first test image each time the focal length is changed, and a chromatic aberration correction unit 16 that corrects the second color signal obtained from the video signal of the subject based on the chromatic aberration corresponding to the focal length at the time the subject was photographed when the subject was photographed.

Description

Technical Field

[0001] The present invention relates to a magnification chromatic aberration correction circuit, a magnification chromatic aberration correction method, and a magnification chromatic aberration correction program.

Background Art

[0002] When light enters a lens obliquely, due to the difference in refractive index depending on the color of the light, a shift occurs in the size of the image for each color on the focal plane. This shift is called magnification chromatic aberration. Patent Document 1 describes a technique for correcting magnification chromatic aberration.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, Patent Document 1 only corrects so that the images of the B signal and the G signal match each other, and when the focal length from the lens to the focal plane is changed using a zoom lens or the like, the magnification chromatic aberration cannot be automatically corrected.

[0005] The present invention has been made in view of the above circumstances, and an object thereof is to provide a technique capable of automatically correcting magnification chromatic aberration.

Means for Solving the Problems

[0006] A chromatic aberration correction circuit according to one aspect of the present invention comprises: a control unit for controlling the focal length; an imaging unit for capturing a test image at the focal length; a test image detection unit for detecting a first test image and a second test image, respectively, from a first color signal and a second color signal obtained from the video signal of the test image; a chromatic aberration detection unit for detecting the chromatic aberration of the second test image relative to the first test image each time the focal length is changed; and a chromatic aberration correction unit for correcting the second color signal obtained from the video signal of the subject based on the chromatic aberration corresponding to the focal length at the time the subject was photographed, when the subject was photographed.

[0007] One embodiment of the present invention is a computer-based method for correcting chromatic aberration, in which the focal length is controlled, a test image is captured at the said focal length, a first test image and a second test image are detected from a first color signal and a second color signal obtained from the video signal of the test image, the chromatic aberration of the second test image relative to the first test image is detected each time the focal length is changed, and when a subject is captured, the second color signal obtained from the video signal of the subject is corrected based on the chromatic aberration corresponding to the focal length at the time the subject was captured.

[0008] A magnification chromatic aberration correction program according to one aspect of the present invention causes a computer to execute the above-described magnification chromatic aberration correction method. [Effects of the Invention]

[0009] According to the present invention, chromatic aberration can be automatically corrected. [Brief explanation of the drawing]

[0010] [Figure 1] This figure shows an example of a chromatic aberration correction circuit configuration. [Figure 2] This figure shows an example of the operation when calculating the correction amount for chromatic aberration. [Figure 3] This figure shows a specific example of a test image. [Figure 4] This figure shows an example of the operation when correcting chromatic aberration. [Figure 5] This figure shows a specific example of a test image. [Figure 6] This figure shows a specific example of a test image. [Figure 7] This figure shows a specific example of a test image. [Figure 8] This figure shows an example of a chromatic aberration correction circuit configuration. [Modes for carrying out the invention]

[0011] Embodiments of the present invention will be described below with reference to the drawings. In the drawings, identical parts are denoted by the same reference numerals and their descriptions are omitted.

[0012] Figure 1 shows an example of the configuration of a chromatic aberration correction circuit.

[0013] The magnification chromatic aberration correction circuit 1 is, for example, a circuit within a camera and comprises a control unit 11, an imaging unit 12, a test image detection unit 13, a chromatic aberration detection unit 14, a storage unit 15, a chromatic aberration correction unit 16, and an output unit 17.

[0014] The control unit 11 has a function to control the focal length of the imaging unit 12.

[0015] The imaging unit 12 has the function of capturing a subject at a focal length controlled by the control unit 11 and outputting a video signal of the subject. For example, the imaging unit 12 is a lens group with a changeable focal length, such as a manual zoom lens, an auto-zoom lens with autofocus function, or an image sensor.

[0016] The subjects include not only portraits of people or landscapes that the user wishes to photograph, but also test images of predetermined patterns to correct chromatic aberration. Furthermore, the video signal of the subject includes, for example, an R signal (red signal), a G signal (green signal), and a B signal (blue signal).

[0017] The test image detection unit 13 inputs the video signal of the test image output from the imaging unit 12, and detects a red test image R, a green test image G, and a blue test image B from the R signal, G signal, and B signal included in the video signal, respectively, and has a function of outputting the detected test image R, test image G, and test image B.

[0018] The chromatic aberration detection unit 14 inputs the test image R, test image G, and test image B output from the test image detection unit 13, and has a function of detecting the deviation amount (magnification chromatic aberration) indicating how much the test image R and test image B are respectively deviated from the test image G.

[0019] Further, the chromatic aberration detection unit 14 calculates an R signal correction amount for aligning the image of the R signal with the image of the G signal using the deviation amount of the test image R with respect to the test image G, and calculates a B signal correction amount for aligning the image of the B signal with the image of the G signal using the deviation amount of the test image B with respect to the test image G.

[0020] Further, the chromatic aberration detection unit 14 acquires the focal length information from the control unit 11, associates the focal length with the R signal correction amount and the B signal correction amount, stores them in the storage unit 15, and further outputs them to the chromatic aberration correction unit 16.

[0021] Note that the test image detection unit 13 and the chromatic aberration detection unit 14 execute their respective functions each time the focal length of the imaging unit 12 is changed by the control unit 11.

[0022] The storage unit 15 has a function of storing, in association with each other, each focal length of the imaging unit 12 changed by the control unit 11 and the R signal correction amount and the B signal correction amount respectively calculated by the chromatic aberration detection unit 14 at each focal length.

[0023] The chromatic aberration correction unit 16 has a function of correcting the R signal and the B signal included in the video signal of the subject based on the deviation amount (magnification chromatic aberration) corresponding to the focal length at the time of subject shooting when the subject is photographed.

[0024] Specifically, the chromatic aberration correction unit 16 receives the video signal of the subject output from the imaging unit 12 and has the function of correcting the R signal and B signal contained in the video signal, respectively, using the R signal correction amount and B signal correction amount corresponding to the focal length at the time of subject shooting.

[0025] The R signal correction amount and B signal correction amount used by the chromatic aberration correction unit 16 for correction may be output from the chromatic aberration detection unit 14 or obtained from the storage unit 15.

[0026] The output unit 17 has the function of outputting the R signal and B signal corrected by the chromatic aberration correction unit 16, and the original G signal that was not corrected by the chromatic aberration correction unit 16, as the video signal of the subject to the outside of the magnification chromatic aberration correction circuit 1.

[0027] Figure 2 shows an example of the operation when calculating the correction amount for chromatic aberration.

[0028] Step S101; The imaging unit 12 is equipped with a lens whose characteristics regarding chromatic aberration are unknown. This lens can be zoomed by electronic control. The control unit 11 controls the zooming and focusing of the lens in the imaging unit 12, and sets the focal length of the lens to its shortest wide-angle end.

[0029] Step S102; The imaging unit 12 captures a test image T, which has a circle (test image) drawn in black in the center on a white background, as shown in Figure 3, and outputs the video signal of the circle contained in the captured test image T to the test image detection unit 13 as three video signals: R signal, G signal, and B signal.

[0030] Step S103; The test image detection unit 13 detects the red circle R, the green circle G, and the blue circle B from the R signal, G signal, and B signal output from the imaging unit 12, and calculates the diameter L of each circle R, G, and B.

[0031] For example, the test image detection unit 13 can both detect circles and calculate their diameters by using the Hough transform. The test image detection unit 13 then outputs the diameter data for each circle R, G, and B to the chromatic aberration detection unit 14.

[0032] Step S104; The chromatic aberration detection unit 14 uses the diameter data of circles R, G, and B output from the test image detection unit 13 to calculate how many times larger the diameters of circles R and B are compared to the diameter of circle G, and determines the reciprocal of these magnifications as the R signal correction amount and the B signal correction amount.

[0033] Step S105; The chromatic aberration detection unit 14 acquires the current focal length information from the control unit 11 and stores the acquired current focal length, the R signal correction amount, and the B signal correction amount in the storage unit 15, associating them with each other.

[0034] Step S106; The control unit 11 determines whether the current focal length is the longest telephoto end. If the current focal length is not the telephoto end, the process returns to step S101, and the focal length of the imaging unit 12 is increased by a predetermined fixed distance.

[0035] Subsequently, the chromatic aberration correction circuit 1 repeats steps S101 to S105 until the focal length reaches the telephoto end. As a result, the memory unit 15 stores the R signal correction amount and B signal correction amount for each different focal length. The number of measurement points between the wide-angle end and the telephoto end can be arbitrarily determined by the user. The more measurement points there are, the more accurately chromatic aberration can be corrected.

[0036] Figure 4 shows an example of the operation when correcting chromatic aberration.

[0037] Step S201; The control unit 11 adjusts the focal length of the imaging unit 12 to the focal length determined by the user. The imaging unit 12 photographs the subject at that focal length and outputs the image signal of the photographed subject to the chromatic aberration correction unit 16 as three video signals: R signal, G signal, and B signal.

[0038] Step S202; The chromatic aberration correction unit 16 obtains the R signal correction amount and B signal correction amount corresponding to the focal length determined by the user from the storage unit 15, and corrects the R signal and B signal contained in the video signal, respectively, using the obtained R signal correction amount and B signal correction amount.

[0039] In other words, the chromatic aberration correction unit 16 corrects the subject image of the R signal and the subject image of the B signal to match the subject image of the G signal, respectively. Specifically, the chromatic aberration correction unit 16 multiplies the R signal correction amount and the B signal correction amount, respectively, for the R signal and B signal included in the video signal.

[0040] If there are no R signal correction amounts and B signal correction amounts corresponding to the focal length determined by the user, the chromatic aberration correction unit 16 uses R signal correction amounts and B signal correction amounts linearly interpolated using nearby focal lengths before and after the determined focal length.

[0041] Step S203; The output unit 17 outputs the R and B signals corrected by the chromatic aberration correction unit 16, along with the original G signal that was not corrected by the chromatic aberration correction unit 16, as the video signal of the subject to the outside of the magnification chromatic aberration correction circuit 1.

[0042] (Variation 1) The operation for calculating the correction amount for chromatic aberration shown in Figure 2 may start after setting the focal length to the telephoto end, or it may start after setting the focal length to any position between the wide-angle and telephoto ends.

[0043] (Modification 2) The test image pattern may be concentric circles or ellipses, as shown in Figure 5. Since the only requirement is to calculate the distance L between two predetermined points spaced apart on the test image, the test image may be a triangle or a quadrilateral, or a shape that is not entirely enclosed in space, such as a combination of four L-shaped figures as shown in Figure 6, or a combination of two arch-shaped figures as shown in Figure 7.

[0044] (Variation 3) The chromatic aberration correction unit 16 may correct the subject's video signal using the R signal correction amount and B signal correction amount output from the chromatic aberration detection unit 14, or it may correct the subject's video signal using the R signal correction amount and B signal correction amount acquired from the storage unit 15.

[0045] (Modification 4) The combination of colors in the color signals and the number of color signals only need to be two color signals of distinct colors. For example, chromatic aberration can be corrected using only two of the three RGB color signals.

[0046] This embodiment can also be applied when the imaging unit 12 is capable of outputting four video signals by adding one color signal to the three RGB color signals, when the imaging unit 12 is capable of outputting two or more color video signals other than RGB, or when the imaging unit 12 is capable of outputting two or more color signals separated by color wavelength, such as infrared.

[0047] (Variation 5) This embodiment can also be applied when the imaging unit 12 outputs, for example, a luminance signal or a chromatic difference signal (such as YUV) instead of a color signal. In this case, as shown in Figure 8, a conversion unit 18 that converts the luminance signal or chromatic difference signal into a color signal can be placed between the imaging unit 12, the test image detection unit 13, and the chromatic aberration correction unit 16.

[0048] (Experimental variation 6) The chromatic aberration correction circuit 1 may be a chromatic aberration correction device (a computer equipped with a CPU, memory, etc.) built into the camera. The operations shown in Figures 2 and 4 may also be performed by that computer.

[0049] As described above, according to this embodiment, test image R, test image G, and test image B are detected from the R signal, G signal, and B signal obtained from the video signal of the test image, respectively. Each time the focal length is changed, the chromatic aberration of test image G relative to test image R and test image B is detected, respectively. When a subject is photographed, the R signal and B signal obtained from the video signal of the subject are corrected based on the chromatic aberration corresponding to the focal length at the time the subject was photographed. Therefore, even when the focal length is changed using manual zoom lenses or motorized zoom lenses used in broadcast cameras and consumer cameras, chromatic aberration can be automatically corrected. [Explanation of Symbols]

[0050] 1 Lateral chromatic aberration correction circuit 11 Control Unit 12 Imaging Unit 13 Test image detection unit 14 Chromatic aberration detection unit 15 Storage section 16 Chromatic aberration correction section 17 Output section 18 Conversion section

Claims

1. A control unit that controls the focal length, An imaging unit that captures a test image at the aforementioned focal length, A test image detection unit detects a first test image and a second test image, respectively, from a first color signal and a second color signal obtained from the video signal of the test image. Each time the focal length is changed, a chromatic aberration detection unit detects the magnification chromatic aberration of the second test image relative to the first test image, When a subject is photographed, a chromatic aberration correction unit corrects a second color signal obtained from the video signal of the subject based on the magnification chromatic aberration corresponding to the focal length at the time of subject photography. A chromatic aberration correction circuit equipped with a magnification chromatic aberration correction circuit.

2. The magnification chromatic aberration correction circuit according to claim 1, further comprising an output unit that outputs a first color signal obtained from the video signal of the subject and a corrected second color signal as the video signal of the subject.

3. The first color signal is a green signal, The magnification chromatic aberration correction circuit according to claim 1, wherein the second color signal is a red signal or a blue signal.

4. In a computer-based method for correcting chromatic aberration, Control the focal length, A test image was taken at the aforementioned focal length. The first test image and the second test image are detected from the first and second color signals obtained from the video signal of the aforementioned test image. Each time the focal length is changed, the chromatic aberration of the second test image relative to the first test image is detected. When a subject is photographed, a second color signal obtained from the video signal of the subject is corrected based on the chromatic aberration corresponding to the focal length at the time of photographing the subject. Lateral chromatic aberration correction method.

5. A chromatic aberration correction program that causes a computer to execute the chromatic aberration correction method described in claim 4.

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