JPH0927926A - Image pickup device and optical axis deviation correcting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily correct an optical axis deviation, regardless of dispersion in accuracy of mechanism of a lens system in the image pickup device. SOLUTION: The measured deviation of an optical axis between a lens 1 and a CCD imager 2 is stored in a memory 5. A microcomputer 6 reads an optical axis deviation out of the memory 5 and controls a CCD imager controller 7 to correct an optical axis deviation by shifting a segmentation position so that the center of a valid image segmented from the CCD imager 2 and the optical axis are coincident.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image pickup apparatus such as an industrial video camera which requires a high quality lens in which the optical axis shift is not allowed, and more specifically, the optical axis shift is electronically corrected. It is about technology.

[0002]

2. Description of the Related Art Conventionally, as a lens system of an image pickup apparatus as described above, there are those shown in FIGS. 5 and 6, for example. 5 and 6 show an ideal lens system with no optical axis shift. FIG. 5 shows a state at the wide end by zooming, and FIG. 6 shows a state at the tele end.

As shown in these figures, in the lens system with no optical axis shift, even if the zoom lens 12 is moved, the image at the center A of the chart 11 which is the subject is always at the center B of the CCD imager 13. It is imaged. That is, the center of the image does not deviate according to the zoom operation.

However, in practice, a system in which an optical axis shift exists between the optical axis 15 of the lens and the center B of the CCD imager 13 for capturing an image due to mechanical variations. 8 and 9 show a lens system having an optical axis shift in the vertical direction. FIG. 8 shows a state at the wide end by zooming, and FIG. 9 shows a state at the tele end.

FIG. 8 shows a state in which the image pickup device is set so that the center A of the chart 11 coincides with the center B of the CCD imager 13 at the wide end. In this figure,
The distance between the zoom lens 12 and the chart 11 is L1,
The focal length at the wide end is Fw, the center A of the chart 11, the center of the zoom lens 12, and the CCD imager 13.
Assuming that the angle formed by a straight line passing through the center B of the optical axis 15 with the optical axis 15 is θw and the vertical optical axis shift is Y, the relationship is expressed by the following equation [1].
become that way. Y = Fw · tan θw [1]

Next, when zooming is performed from this state to the tele end, the state shown in FIG. 9 is obtained. Here, the distance between the zoom lens 12 and the chart 11 is L2, the focal length at the tele end is Ft, and the straight line passing through the center A of the chart 11 and the center of the zoom lens 12 and the center B of the CCD imager 13 is the optical axis. If the angle formed with 15 is θt and the deviation between the optical axis 15 and the center of the image on the CCD imager 13 is Y ′,
The relationship is as in the following expression [2]. Y ′ = Ft · tan θt ... [2]

Further, when the zoom ratio at the telephoto end and the wide-angle end is Z, there is a relation of Ft = Fw · Z ... [3], so that Y ′ = Ft · tan θt = Fw · Z · tan θt ... [4] Become.

Since L1 and L2 are usually very large, tan θw≈tan θt ... [5]

Therefore, Y '= Z.Y ... [6], and the CCD imager 1 at the tele end and the wide end.
A deviation of Y′−Y = Y (Z−1) ... [7] from the center B of 3 occurs.

The lens system having the optical axis shift Y in the vertical direction has been described above, but the optical axis shift X in the horizontal direction has been described.
Similarly, when X ′ is present, a shift of X′−X = X (Z−1) ... [8] occurs.

[0011]

As described above, if the optical axis of the lens system is deviated, the position of the object is deviated during zooming, so that it is suitable for industrial applications where high positional accuracy is required. Was inappropriate. For example, in a surveillance camera, even if the camera is fixed and adjusted so that the center of the subject is at the center of the screen at the wide end, the target that should have been at the center of the screen disappears when the tele end is used for enlargement. There will be a problem of being lost.

Therefore, conventionally, it was necessary to realize high mechanical accuracy so as to eliminate the optical axis shift. The present invention has been made in view of such a problem, and provides an image pickup apparatus and an optical axis shift correcting method thereof that can easily correct the optical axis shift regardless of the mechanical precision of the lens system. The purpose is to

[0013]

In order to solve the above problems, an image pickup apparatus according to the present invention comprises a first means for storing an optical axis shift amount between a lens and an image pickup element, and a first means. And a means for electronically moving the image according to the optical axis shift amount read from the means. Here, the second means is realized by variably configuring the position where the image is cut out from the image sensor or the image storage means.

The optical axis correction method for an image pickup apparatus according to the present invention measures the amount of optical axis shift between the lens and the image pickup element,
It is characterized in that the optical axis shift is corrected by electronically moving the image according to the optical axis shift amount. Here, for measuring the optical axis shift amount between the lens and the image pickup device, for example, the zoom lens is moved from the wide end to the tele end, and the optical axis shift is based on the moving amount of the subject center and the zoom ratio at that time. This is done by calculating the amount.

[0015]

Embodiments of the present invention will be described below in detail with reference to the drawings. (First Embodiment) FIG. 1 shows a first embodiment of an image pickup apparatus according to the present invention.
It is a block diagram showing an embodiment. This embodiment is
A CCD imager having a size larger than the effective screen of the image pickup device is used, and the position where the effective screen is cut out from this CCD imager is adjusted according to the amount of optical axis deviation to correct the optical axis deviation.

As shown in FIG. 1, in this embodiment, a lens 1, a CCD imager 2 for converting an image of an object transmitted through the lens 1 into an electric signal, and an output of the CCD imager 2 are digitized. A / D converter 3 and A / D
A signal processing block 4 that performs a predetermined signal processing on the output of the converter 3 is provided.

Further, in this embodiment, a memory 5 for storing the optical axis shift amount of the image pickup apparatus, a microprocessor 6 for sending a command signal to a CCD imager controller 7 described later based on the output of the memory 5, and a microprocessor 6 are provided. CCD according to the command signal sent from the processor 6
A CCD imager controller 7 for controlling the position of the effective screen cut out from the imager 2 is provided.

Here, the CCD imager 2 has a size larger than the effective screen of the image pickup device, and the position where the effective screen is cut out can be changed by the control of the CCD imager controller 7. Also,
The memory 5 is an electrically rewritable storage element such as an EEPROM.

FIG. 2 is a flow chart showing a procedure for measuring the optical axis shift amount and storing it in the memory 5 in the embodiment of the image pickup apparatus according to the present invention. Further, FIG. 3 is a diagram for explaining the principle of measuring the optical axis shift amount.

First, the zoom lens of the image pickup device is set to the wide end (step S1 in FIG. 2). At this time, if there is an optical axis shift, the center of the chart and the center of the image do not match, so the position of the image pickup device is finely adjusted in the horizontal and vertical directions so that the center of the chart comes to the center of the image (S2).

Next, Z times of zooming is performed from that state to obtain the tele end (S3). At this time, as shown in FIG. 3, the center of the chart located at the center of the image at the wide end is moved horizontally by x and vertically by y to move horizontally from the center of the optical axis to X ′, vertical. It is located at a position (X ′, Y ′) displaced by Y ′ in the direction. At this time, (x, y) is measured. As a measuring method, for example, the amount of movement x in the horizontal direction is counted in units of a clock signal having a predetermined frequency, and in the vertical direction, the number of lines of an image is counted as a unit.

At this time, as shown in FIG. 3, x = X'-X ... [9] y = Y'-Y ... [10].

From this equation and the equations [7] and [8] described with reference to FIGS. 8 and 9, the optical axis shift amount (X, Y) is obtained.
Is expressed by the following equations [11] and [12]. X = x / (Z-1) [11] Y = y / (Z-1) [12]

Therefore, the optical axis shift amount is calculated using this relational expression (S5). Then, this result is stored in the memory 5 (S6). Here, the calculation process of the optical axis shift amount may be calculated and stored by the microprocessor 6 incorporated in the imaging device, but may be calculated externally and only the result is stored in the memory 5.
May be stored.

Next, a method for correcting the optical axis shift based on the optical axis shift amount thus obtained will be described with reference to FIGS. 1 and 4. The microprocessor 6 reads the optical axis shift amount (X, Y) from the memory 5. And
CC by controlling the CCD imager controller 7
The optical axis shift (X, Y) is corrected by shifting the cutout position so that the center C of the effective screen 14 cut out from the D imager 2 and the optical axis 15 coincide with each other. As a result, an image pickup apparatus equivalently having no optical axis deviation is realized.

(Second Embodiment) FIG. 5 is a block diagram showing a second embodiment of the image pickup apparatus according to the present invention. Here, parts corresponding to those in FIG. 1 are assigned the same numbers. In this embodiment, the image is enlarged by using the image memory 7 and the effective screen is made smaller than the output image of the CCD imager 2 for correction.

As shown in FIG. 5, in the present embodiment, the lens 1, the CCD imager 2 for converting the image of the subject transmitted through the lens 1 into an electric signal, and the output of the CCD imager 2 are digitized. A / D converter 3 and A / D
A signal processing block 4 for performing a predetermined signal processing on the output of the converter 3 and an image memory 8 for storing the output video signal of the signal processing block 4 are provided.

Further, in this embodiment, the memory 5 for storing the optical axis shift of the image pickup apparatus, the microprocessor 6 for sending a command signal to the memory controller 9 described later based on the output of the memory 5, and the microprocessor 6 A memory controller 9 for supplying a writing / reading signal to the image memory 8 according to a command signal sent thereto.

Here, the optical axis shift amount of the image pickup device is measured and stored in the memory 5 by the procedure shown in FIG. Further, the memory controller 9 writes a video signal corresponding to the size of the CCD imager 2, cuts out a part of the written image as an effective screen, and enlarges and reads it. And the position to cut out the effective screen is
By shifting according to the optical axis shift amount read from the memory 5, an image pickup apparatus equivalently free from optical axis shift is realized. In other words, the first embodiment corrects the optical axis shift by shifting the position cut out from the CCD imager, while the second embodiment corrects the optical axis shift by shifting the position cut out from the image memory. There is.

In the first or second embodiment, the CCD is based on the optical axis shift amount read from the memory 5.
As means for controlling the imager controller 7 or the memory controller 9, hardware may be used instead of the microprocessor.

[0031]

As described above, according to the present invention,
Even if the lens system in the image pickup apparatus has an optical axis shift due to variations in mechanical accuracy, it is possible to easily realize a lens system equivalent to no optical axis shift without being influenced by the variation. Therefore, it is not necessary to manufacture the lens system with high mechanical accuracy as in the conventional case.

[Brief description of drawings]

FIG. 1 is a block diagram showing a first embodiment of an image pickup apparatus according to the present invention.

FIG. 2 is a flowchart showing a procedure for measuring an optical axis shift amount and storing it in a memory in the embodiment of the present invention.

FIG. 3 is a diagram for explaining a principle of measuring an optical axis shift amount.

FIG. 4 is a diagram for explaining an optical axis correction method.

FIG. 5 is a block diagram showing a second embodiment of an imaging device according to the present invention.

FIG. 6 is a diagram showing a state at the wide end of an ideal lens system with no optical axis deviation.

FIG. 7 is a diagram showing a state at the tele end of an ideal lens system without optical axis deviation.

FIG. 8 is a diagram showing a state at a wide end of a lens system having an optical axis shift.

FIG. 9 is a diagram showing a state at a tele end of a lens system having an optical axis shift.

[Explanation of symbols]

1 ... Lens, 2 ... CCD imager, 5 ... Memory,
6 ... Microprocessor, 7 ... CCD imager controller, 8 ... Image memory, 9 ... Memory controller

Claims (4)

[Claims] 1. A first means for storing an optical axis shift amount between a lens and an image pickup device, and a second means for electronically moving an image in accordance with the optical axis shift amount read from the first means. And an image pickup device. 2. The image pickup apparatus according to claim 1, wherein the second means is configured such that a position where an image is cut out from the image pickup element or the image storage means is variable. 3. An optical axis shift is corrected by measuring an optical axis shift amount between a lens and an image sensor and electronically moving an image according to the optical axis shift amount. A method for correcting an optical axis shift of an imaging device. 4. The optical axis shift of the image pickup apparatus according to claim 3, wherein the zoom lens is moved from the wide end to the tele end, and the optical axis shift amount is measured based on the moving amount of the subject center and the zoom ratio at that time. Correction method.