JP2008294692A - Image processing device - Google Patents

Abstract

In correction of chromatic aberration of magnification, an optical axis shift due to attachment / detachment of a lens causes a reduction in accuracy of aberration correction. Ideally, an operation of detecting an optical axis is required every time a lens is attached / detached. Etc.).
In an optical axis detection necessity determination unit 107, the maximum value of the inclination of aberration information stored in an aberration information storage unit 106 is obtained and compared with a threshold value, so that the influence of the optical axis shift on aberration correction is affected. The size is determined, and the necessity of the optical axis detection work is displayed to the worker.
[Selection] Figure 1

Description

  The present invention relates to an image processing apparatus that corrects lateral chromatic aberration of an imaging lens in an imaging apparatus such as a video camera or an electronic still camera.

  The chromatic aberration of magnification of the imaging lens is a phenomenon that occurs because the refractive index of the lens varies depending on the wavelength of light, and as shown in FIG. 5, red, blue, and green light forms images at different positions on the imaging surface. In addition, this is a phenomenon in which the image is blurred or the outline is colored.

  As a magnification chromatic aberration correction for correcting such a shift of the imaging position, for example, one described in Patent Document 1 is known.

  FIG. 6 is a block diagram of an image processing apparatus that performs lateral chromatic aberration correction described in Patent Document 1. In FIG. In FIG. 6, an image obtained through a lens 600 is color-separated into R, G, and B by a prism 601, imaged on an imaging surface of an imaging device 602 such as a CCD, and photoelectrically converted, and then an A / D converter 603. It becomes a digital video signal. Next, the aberration correction unit 604 corrects the chromatic aberration of magnification based on the chromatic aberration correction information stored in the aberration information storage unit 605.

  In such magnification chromatic aberration correction, the deviation of the optical axis may affect the correction accuracy. Since the lateral chromatic aberration changes in accordance with the distance from the optical axis, when the optical axis is shifted, an error occurs between the aberration information stored in the aberration information storage unit and the actual aberration, and the correction accuracy decreases.

  Patent Document 2 improves the correction accuracy by detecting such a deviation of the optical axis due to camera shake correction and generating magnification chromatic aberration correction information according to the detection result.

Moreover, what was described in patent document 3 is known as a means to detect the shift | offset | difference of the optical axis of a lens. A checkerboard chart is imaged, the zoom position of the lens is changed, and the optical axis of the lens is detected from the change of each pixel. If the optical axis coordinates in aberration correction are controlled according to the detection result, it is possible to prevent a reduction in correction accuracy.
JP-A-6-78314 JP 2004-336106 A Japanese Patent Laid-Open No. 4-65993

  However, in an image pickup apparatus in which a lens can be attached / detached, when the optical axis detection as described in Patent Document 3 is performed every time the lens is attached / detached to obtain magnification chromatic aberration correction information, the chart is adjusted each time and the image is taken. There is a problem that it requires work, and this is a burden on the operator (such as a photographer).

  The present invention solves the above-described conventional problems, and an object of the present invention is to display the necessity of optical axis detection to an operator, thereby reducing the burden on the operator.

  In order to solve the above problems, an image processing apparatus of the present invention includes a chart for detecting an optical axis of an imaging lens, and an optical axis detection unit for detecting the optical axis of the imaging lens from an image obtained by imaging the chart. An aberration correction unit that corrects chromatic aberration of magnification with reference to the optical axis detected by the optical axis detection unit, an aberration information storage unit that stores aberration information of the aberration correction unit, and light based on the aberration information of the aberration information storage unit An optical axis detection necessity determination unit that determines the necessity of axis detection, and a display unit that displays a determination result of the optical axis detection necessity determination unit. It has the effect of displaying the necessity / unnecessity to the user.

  As described above, the present invention determines and displays the influence of the deviation of the optical axis position due to the attachment / detachment of the lens on the aberration correction in the lateral chromatic aberration correction, and reduces the work when the optical axis detection is not necessary. The effect of being able to be obtained is obtained.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

(Embodiment 1)
FIG. 1 is a block diagram of an image processing apparatus according to the present invention. In FIG. 1, an image obtained through a lens 100 attached to a housing 110 is color-separated into R, G, and B by a prism 101, formed on an imaging surface of an imaging device 102 such as a CCD, and photoelectrically converted. The D converter 103 generates a digital video signal.

  The aberration correction unit 105 corrects the lateral chromatic aberration based on the lateral chromatic aberration correction information stored in the aberration information storage unit 106.

  The optical axis detection necessity determination unit 107 calculates the maximum value of the inclination of the correction information stored in the aberration information storage unit 106, determines the necessity of optical axis detection by comparison with a certain threshold value, and displays the display unit 108. Display the judgment result.

  The optical axis detection unit 104 detects the optical axis 111 of the lens 100 by calculation from a video signal when the chart 109 for optical axis detection is imaged. The detected optical axis position coordinates are input to the aberration correction unit 105, and the optical axis coordinates in the aberration correction are controlled.

  The operation of the image processing apparatus configured as described above will be described with reference to FIGS.

  FIG. 2 is an example of aberration information stored in the aberration information storage unit 106. In this example, the aberration information is information indicating the correspondence between the distance from the optical axis of each pixel and the estimated amount of aberration. In the figure, the horizontal axis indicates the distance from the optical axis of the pixel to be corrected for aberration. The vertical axis indicates the estimated value of the aberration amount in the target pixel. In addition, the point at which the estimated value of the aberration amount is 0 in this curve is the point at which the distance from the optical axis is 0. As shown in the figure, the chromatic aberration of magnification of the imaging lens changes with the distance from the optical axis as a parameter. In the drawing, the aberration amount of the R or B signal with the G signal as a reference is shown. Based on such aberration information, the aberration correction unit 105 corrects each pixel of the R and B signals according to the distance from the optical axis.

  That is, the optical axis position coordinate in aberration correction is an important point serving as a reference for correction. However, in the case of an interchangeable lens type video camera or the like, the positional relationship between the imaging lens 100 and the imaging surface of the imaging element 102 is shifted every time the lens is attached / detached due to slight distortion between the housing 110 and the imaging lens 100, and light. The axis position coordinates may be shifted. At this time, an error occurs between the aberration information stored in advance in the aberration information storage unit and the actual aberration, so that the accuracy of aberration correction is lowered. Accordingly, in an interchangeable lens type video camera or the like, aberration detection can be performed with higher accuracy by detecting the optical axis position coordinates each time the lens is attached and detached, and considering the detected optical axis position.

  The detection of the optical axis position coordinates is performed by the optical axis detection chart 109 and the optical axis detection unit 104.

  First, a chart having two or more straight lines in the horizontal and vertical directions as shown in FIG. 3 is imaged at two or more zoom lens positions. Next, in the optical axis detection unit 104, linear position coordinates X1, X2, Y1, Y2 at a certain lens position (lens position (1) in the figure) and another lens position (lens position (2)). Linear position coordinates X1 ′, X2 ′, Y1 ′, Y2 ′ are detected. At this time, since the optical axis position coordinates (Xc, Yc) are on the extended line of the change of each straight line as shown in FIG. 3, they are the intersections of the dotted lines in FIG. At this time, the coordinates of the optical axis position can be easily obtained by solving the following linear expression.

| Xc-X1 |: | Xc-X2 | = | X1'-X1 |: | X2'-X2 |
| Yc-Y1 |: | Yc-Y2 | = | Y1'-Y1 |: | Y2'-Y2 |
The above-described detection operation of the optical axis position coordinates should ideally be performed each time the lens is attached / detached, which is a burden on the operator (such as a cameraman).

  However, depending on the chromatic aberration characteristics of the lens, even if the optical axis position is slightly shifted, there is a case where the correction accuracy is hardly affected. If it is known, it is not necessary to perform the above-described optical axis position coordinate detection operation, and the burden on the operator can be eliminated.

  Therefore, the optical axis detection necessity determination unit 107 determines the magnitude of the influence of the deviation of the optical axis position coordinate on the correction accuracy, and displays the determination result on the display unit 108.

  The determination method will be described with reference to FIG.

  First, the rate of change of the curve indicating the aberration information stored in the aberration information storage unit 106, that is, the maximum value of the tangent slope is calculated. When the maximum value is large as shown in (a) in the figure, if the optical axis position is shifted (0 ′ → 0 in the figure), the error between the aberration (same dotted line) and the actual aberration (same solid line) in the aberration information storage unit Therefore, the correction accuracy is greatly reduced. Therefore, it is determined that optical axis detection is necessary. When the maximum value is small as shown in (b) in the figure, even when the optical axis position is deviated, the error between the aberration in the aberration information storage unit and the actual aberration is small, so the decrease in correction accuracy is small. Therefore, it is determined that optical axis detection is not necessary.

  In actual determination, the necessity of optical axis detection is determined based on a comparison result between the maximum value of the inclination and a certain threshold value. The above determination result is displayed on the display unit 108.

  As described above, according to the present embodiment, it is possible to display to the operator the magnitude of the influence of the optical axis shift on the aberration correction from the magnification chromatic aberration information of the lens used, and the operator needs to detect the optical axis. Therefore, the optical axis can be detected only when it is determined to be necessary, and the burden on the optical axis detection can be reduced.

  Note that the output of the optical axis detection necessity determination unit 107 is not limited to the determination result of whether or not it is necessary, and the value of the tilt may be output and displayed as it is.

  Note that the determination criterion in the optical axis detection necessity determination unit 107 is not limited to the maximum value of inclination, and may be, for example, an average value of inclinations at a plurality of arbitrary points.

  The image processing apparatus according to the present invention determines whether the optical axis position shift due to the attachment / detachment of the lens has an effect on the aberration correction in the lateral chromatic aberration correction, and displays whether the optical axis detection is necessary. This is advantageous in that the work can be reduced when it is not necessary, and is also useful as an image processing device or the like for correcting the lateral chromatic aberration of a lens in an imaging device such as a video camera or an electronic still camera.

Block diagram in Embodiment 1 of the present invention Explanatory diagram showing the relationship between the distance from the optical axis and the amount of aberration Optical axis detection chart and optical axis explanatory diagram Explanatory drawing showing operation of an optical axis detection necessity judgment part Explanation of chromatic aberration of lens magnification Block diagram of a conventional image processing apparatus that performs lateral chromatic aberration

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Lens 101 Prism 102 Image pick-up element 103 A / D converter 104 Optical axis detection part 105 Aberration correction part 106 Aberration information storage part 107 Optical axis detection necessity determination part 108 Display part 109 Chart 110 Housing 111 Optical axis 600 Lens 601 Prism 602 Image sensor 603 A / D converter 604 Aberration correction unit 605 Aberration information storage unit

Claims (3)

An optical axis detector that detects the optical axis of the imaging lens from the video signal;
An aberration correction unit that performs lateral chromatic aberration correction with reference to the optical axis detected by the optical axis detection unit;
An aberration information storage section for storing aberration information of the aberration correction section;
An optical axis detection necessity determination unit that determines the necessity of optical axis detection based on the aberration information in the aberration information storage unit;
A display unit for displaying a determination result of the optical axis detection necessity determination unit;
An image processing apparatus. The image processing according to claim 1, wherein the optical axis detection necessity determination unit outputs information that optical axis detection is necessary if the inclination of the aberration information stored in the aberration information storage unit is greater than or equal to a threshold value. apparatus. The image processing apparatus according to claim 1, wherein the optical axis detection unit detects an optical axis of an imaging lens from a video signal when an optical axis detection chart is captured.

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