JPH06205273A - Video camera with built-in geometrical correction function - Google Patents

Abstract

PURPOSE:To provide the video camera from which a picture without distortion due to aberration of an image pickup lens is obtained. CONSTITUTION:A ROM 103 storing a color magnification aberration parameter of a lens is built in an image pickup lens 1 of the video camera. A CPU 102 reads R, B magnification based on G in the parameter in the replacement of lenses and the result is fed to a control circuit 8 through a lens side contact 101 and a camera side contact 9. R, B pictures are magnified or reduced by a reciprocal of the magnification. When the picture data magnified or reduced are not an integer, a microcomputer in the control circuit 8 calculates an interpolation weighted correction coefficient and the correction coefficient is stored in a RAM 11. An arithmetic operation section 12 executes the product sum arithmetic operation of the coefficients, the result is stored in a buffer memory 13 and to a memory card 15 via a memory card interface 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to image pickup and signal processing means therefor, and more particularly to a video camera device for correcting aberration of an image pickup lens to obtain a high quality image.

[0002]

2. Description of the Related Art Conventionally, in image pickup by a video camera, in order to obtain a high quality image, an image pickup device such as C
In addition to the high density of CD image pickup devices and the high performance of subsequent signal processing, the performance of the image pickup lens that forms an image on the image pickup device is also important, and the image quality commensurate with subsequent photoelectric conversion and signal processing is required. Obtained lenses have been sought. That is, it has been required to have a lens in which each aberration of the lens is well-balanced below a certain level.

However, it is impossible to eliminate geometrical distortion called distortion, especially in a wide-angle lens having a short focus, and an obtained image is also distorted. Further, even in a lens having a relatively long focus, in order to reduce all aberrations to a certain level or less, the number of lenses is increased, the configuration is complicated, and the size is large and heavy.

In the field of image processing, a technique for obtaining an image without distortion by image processing for measurement or the like has been reported, but it is based on a computer for general-purpose image processing, and a video camera. It is not easily realized by itself.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above conventional problems. Among the aberrations of the image pickup lens, the geometric distortion is allowed as a single lens while the geometrical distortion is allowed as a whole. It is an object of the present invention to provide a video camera equipped with an image pickup unit and a signal processing unit for obtaining an image without distortion.

[0006]

The video camera of the present invention comprises:
An imaging lens, an imaging element that converts an object image formed by the imaging lens into an electric signal, an analog-digital converter that converts an output signal of the imaging element into a digital signal, and an analog-digital converter A video camera provided with a frame or a field memory for temporarily storing an output is provided with an arithmetic means for correcting geometric distortion such as chromatic magnification aberration and distortion due to the image pickup lens, and When the geometrical distortion is, for example, a chromatic magnification aberration, a memory for converting the signal into a color signal and storing the color signal is provided, and the arithmetic means calculates each color component based on the output of the memory. The image is enlarged or reduced so as to correct the magnification.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment to which the present invention is applied is shown in FIG.
It will be described with reference to FIG. FIG. 1 shows an embodiment applied to an electronic still camera for recording on a memory card. In FIG. 1, 1 is an interchangeable imaging lens (hereinafter,
It is called a lens. ) 2 is a color separation prism and is a reflecting surface 20
Blue light and red light are selectively reflected by 1, 202, and B (blue), G (green), R are reflected by the image pickup devices 301, 302, 303.
The image is separated into (red) and imaged. The image pickup device 301
The signals read from ˜303 are sampled and held by the sample and hold circuit 4, and converted into digital signals by the A / D conversion circuit 5. The digital signal is subjected to signal processing such as white balance and gamma correction in the signal processing circuit 6, and then stored in the frame memory or the field memory 7 for each color component.

Reference numeral 8 is a control circuit for the entire video camera. The control circuit 8 passes through a communication contact (camera side contact) 9 in the camera and a communication contact (lens side contact) 101 provided in the lens 1 to the lens. The lens control CPU 102 communicates with the control CPU 102, and as a result, the lens control CPU 102 controls a lens diaphragm driving unit (not shown).

Reference numeral 103 denotes a ROM that stores magnification aberration parameters of lens colors, and stores, for example, color information that maximizes the size of an image and magnification information of other color components. When the lens is replaced or when the power of the camera is turned on, the chromatic magnification aberration parameter is set to the lens control C.
It is read by the PU 102 and sent to the control circuit 8 of the entire camera through the in-camera lens communication contact 101 and the in-camera communication contact 9. For example, the magnifications Kr and Kb of R and B are read based on G. In the following description, both magnifications are represented by K.

Then, the R and B images are enlarged or reduced by the reciprocal of the read magnification K. The center of this expansion or contraction is the optical axis of the lens, the address on the frame memory 7 of the image corresponding to the optical axis is (0, 0), and the pixel at the address (u, v) is expanded or contracted (x ，
If the address is y), then u = Kx v = Ky.

When obtaining the (x, y) data P of the enlarged image, if the above equations u and v are integers, they may be replaced with the image data of (u, v).
Needs interpolation. As an interpolation method, for example, the third-order convolution interpolation method (“Image Analysis Handbook”, first edition on January 17, 1991, second edition on October 15, 1991, published by The University of Tokyo Press, Mikio Takagi, Yoshihisa Shimoda Supervised, 443
Page), weighting is added to the image data of the 16 observation points P _{11 to} P ₄₄ around the address (u, v) of the data P of the image to be interpolated as shown in FIG. A product-sum operation to match is required.

A frame memory control circuit 10 for accessing the corresponding data from the frame memory 7 is provided to perform the sum of products operation. The weighting coefficient is calculated by the microcomputer in the control circuit 8 and is sent to the RAM 11 holding the coefficient. Reference numeral 12 denotes an arithmetic unit that performs a product-sum operation of the held coefficients, and the result calculated by the arithmetic unit 12 is held in the buffer memory 13 and then passed through a memory card interface (I / F) 14 to a memory card. 15 is recorded.

At this time, if the chromatic aberration of magnification is corrected on the basis of the color component imaged with the maximum image size, the other color components will be enlarged and the image will not be lost. Further, when the chromatic aberration of magnification is corrected with reference to the color component formed into the minimum image size, the image in the widest range can be obtained. Further, if one color is always used as a reference, such as in a lens exchange system, information about the reference color is not needed, and less information needs to be transmitted.

Next, lens distortion (distortion)
When correcting, the correction algorithm is, for example,
For example, the method described in “Technical correction method for images that do not require positioning” (Yasuhiro Onodera, Kenichi Kanaya) of SIJ Technical Report (PRU91-113) can be adopted. According to this method, a new address is represented by u = x + Ax ³ + Bxy ² v = y + Cx ² y + Dy ³ using the same address as described above, and this is not necessarily an integer value. Can be asked. In the above equation, when A = B = C = D, there is no distortion, A and D represent corrections that nonlinearly expand in the x-axis and y-axis directions, and B and C represent x-axis and y, respectively.
It represents a correction that gives a deflection symmetrical about the axis.

In the case of axially symmetric distortion like a lens, A =
If D and B = C are obtained, the lens distortion can be easily corrected. This interpolation calculation may be performed by a dedicated calculation unit or a program on a microcomputer that controls the entire camera.

By the way, in many cases, the pixel pitches of the image pickup device are not equal in the vertical and horizontal directions, but in still image data for image processing and the like, this pitch is often treated as equal. As still image data of such a processing system, it is necessary to interpolate data sampled by an anisotropic image sensor whose pixel pitch is not the same in the vertical and horizontal directions and convert it into square grid data with the same vertical and horizontal pitches. There is.

When this function is built into the camera, it can be calculated at once by combining with the geometric distortion correction calculation. Now, assuming that the pitch of the image pickup device is m times the horizontal length, forming a square lattice means that
This means magnifying the image laterally by a factor of m. This processing and the enlargement or reduction of the image when the magnification aberration of the color is corrected can be performed at the same time. That is, 1 / K times in the vertical direction,
Lateral expansion may be performed by m / K times, and the calculation time can be shortened by performing each separately. This embodiment employs a configuration for performing geometric correction in the camera, but an embodiment in which correction information is only recorded or output will be described below.

FIG. 2 shows an embodiment of a video camera integrated with a recording function, which is provided with means for recording information representing geometric distortion of the image pickup lens on a recording medium different from the video signal. In FIG. 2, reference numeral 1 is an interchangeable imaging lens, 2 is a color separation prism, and reflecting surfaces 201 and 20.
2 selectively reflects blue and red light, and the image sensor 30
Images are separated into B, G, and R on 1, 302, and 303 to form an image. The signals read from the image pickup devices 301 to 303 are sampled and held by the sample and hold circuit 4, converted into digital signals by the A / D conversion circuit 5, and further, white balance and gamma correction are performed by the signal processing circuit 6. And the like, and the matrix circuit 16 converts the signals into color difference signals.

Reference numeral 17 denotes a VTR section for digitally recording the obtained video signal, to which an error correction code (ECC) is added in the ECC encoder 171, and the recording modulation coding circuit 1 is added.
At 72, recording modulation coding suitable for the next magnetic tape recording is performed, and it is amplified by the recording amplifier 173 to be recorded on the magnetic tape 174.
Recorded in.

On the other hand, 8 is a control circuit for the whole video camera with a recording function, and the control circuit 8 communicates with the lens control CPU 102 through a communication contact 9 in the camera and a communication contact 101 provided in the lens 1. As a result, the lens control CPU 102 has a lens diaphragm drive unit (not shown).
Control, etc.

Reference numeral 103 denotes a ROM in which parameters for correcting the distortion of the lens 1 are stored. For example, as in the embodiment shown in FIG.
1-113) "Correction method for geometric correction of image without positioning", the correction coefficient (A, B, C,
D) is stored. Then, when the lens is replaced or the power of the camera is turned on, the correction coefficient is controlled by the control CPU 1
02, the contact 101 for communication in the camera lens,
It is sent to the control circuit 8 of the entire camera through the in-camera communication contact 9.

From the memory card interface (I / F) 18, the control circuit 8 causes the IC memory card 19 to store the correction coefficient of the lens used for photographing and the first and last time codes when the lens is used. Record.

In order to correct the distortion of the image at the time of reproduction, the image is read for one frame, the correction coefficient (A to D) corresponding to the time code is read from the IC memory card 19, and the image address and the correction coefficient are used. , The image coordinates (u, v) corrected by the numerical calculation shown in the above-mentioned “Geometric correction method of image not requiring positioning” are obtained, and the image data of the address of the corrected image is converted into the neighboring image by the interpolation method. It is obtained by interpolating the coordinate image data by numerical calculation.

Next, FIG. 3 shows an embodiment of a video camera which outputs a video signal, in which the information indicating the geometric distortion of the imaging lens is output by an output means different from the video signal. . In FIG. 3, 1 is an interchangeable imaging lens, 2 is a color separation prism, and a reflecting surface 201,
The blue and red lights are selectively reflected by 202, and the image sensor 3
The images are separated into B, G, and R on 01, 302, and 303 to form an image. The signals read from the image pickup devices 301 to 303 are sampled and held by the sample and hold circuit 4, converted into digital signals by the A / D conversion circuit 5, and white balance and gamma correction are performed by the signal processing circuit 6. Signal processing is performed, converted into color difference signals by the matrix circuit 16, and digitally output by the digital output I / F unit 20.

On the other hand, 8 is a control circuit for the entire video camera integrated with a recording function. The control circuit 8 communicates with the lens control CPU 102 through a communication contact 9 in the camera and a communication contact 101 provided in the lens 1. As a result, the lens control CPU 102 has a lens diaphragm drive unit (not shown).
Control, etc.

Reference numeral 103 is a ROM in which parameters for correcting the distortion of the lens 1 are stored.
Similar to the embodiment shown in FIG.
-113) "Geometric correction method for images that do not require positioning", the correction coefficients (A, B, C,
D) is stored. Then, when the lens is replaced or the power of the camera is turned on, the correction coefficient is controlled by the control CPU 1
02, the contact 101 for communication in the camera lens,
It is sent to the control circuit 8 of the entire camera through the in-camera communication contact 9. This point is no different from the embodiment of FIG.

Reference numeral 21 denotes a camera control I / F for externally controlling the video camera. When a correction coefficient is requested to be output from an external control device, the correction coefficient of the lens used for photographing is set. Output to external control device.

By connecting such a video camera to a computer having an image memory and the communication means and programmed to correct the image distortion, a computer can read the picked-up image and its image distortion correction coefficient. Even if a lens having image distortion is used, it is possible to obtain an image without distortion by the image distortion correction program.

By the way, when a zoom lens is used as the interchangeable lens, the distortion and the chromatic aberration of magnification often change depending on the focal length of the lens. In such a case, the correction data for each focal length can be stored in the ROM 103 as a table, the focal length information can be read by the lens control CPU 102 by the encoder, and the corresponding correction data can be sent to the camera body.

[0030]

According to the present invention, by incorporating a calculating means for correcting the geometrical distortion caused by the lens in the video camera, the distortion and the chromatic aberration of the magnification of the wide lens can be automatically corrected. With such a function, it is possible to remove some of the restrictions imposed on the lens design, and it is possible to provide a video camera device using a small, lightweight and inexpensive lens.

Further, the image pickup lens is a replaceable video camera, which has information indicating geometric distortion of the lens in the lens as a parameter, and the video camera reads this information when the lens is attached, The effect can be obtained even with an interchangeable lens type video camera by performing a geometric distortion correction calculation suitable for the mounted lens based on the read information.

Further, in a video camera which performs a calculation of a square lattice of a pixel pitch, the processing speed can be increased by performing the calculation together with the calculation of the geometric distortion correction. In a video camera with a built-in recording function that records geometric distortion correction information together with video signals, parameters related to geometric distortion due to the lens are recorded together with image data so that similar correction outside the camera is possible. As a result, the same effect as the above can be obtained as a system.

[Brief description of drawings]

FIG. 1 is a block diagram of a first embodiment of the present invention.

FIG. 2 is a block diagram of a second embodiment of the present invention.

FIG. 3 is a block diagram of a third embodiment of the present invention.

FIG. 4 is an explanatory diagram of a cubic convolution interpolation method.

[Explanation of symbols]

 1 Imaging Lens 2 Color Separation Prisms 301, 302, 303 Imaging Device 4 Sample and Hold Circuit 5 A / D Conversion Circuit 6 Signal Processing Circuit 7 Frame Memory 8 Camera Control Section 9 Camera Side Contact 10 Frame Memory Control Section 11 RAM 12 Coefficient Calculation Part 15 Memory card 101 Lens side contact 102 Lens control CPU 103 ROM

Claims (12)

[Claims] 1. An imaging lens, an imaging element for converting a subject image formed by the imaging lens into an electric signal, and an analog circuit for converting an output signal of the imaging element into a digital signal.
A video camera comprising a digital converter and a frame or field memory for temporarily storing the output of the analog-to-digital converter, further comprising an arithmetic means for correcting the geometric distortion caused by the imaging lens. Video camera. 2. The geometric distortion of the lens to be corrected is a chromatic aberration of magnification, the memory includes a memory for converting a signal into a color signal and storing the color signal, and the arithmetic means outputs the output of the memory. 2. The video camera according to claim 1, wherein the image is enlarged or reduced so that the magnification is corrected for each color component. 3. The video camera according to claim 1, wherein the geometric distortion of the lens to be corrected is distortion of the lens, and the distortion is corrected. 4. The video camera according to claim 1, wherein the geometric correction calculation is performed in combination with the calculation of a square lattice of the pixel pitch. 5. The video camera according to claim 2, wherein the calculation for correcting the color magnification is performed by reducing the image of the other color with the image of the color for which the minimum image is obtained as a reference. . 6. The video camera according to claim 2, wherein the calculation for correcting the color magnification is performed by enlarging the image of another color with the image of the color that gives the maximum image as a reference. . 7. A recording function comprising an imaging lens, an imaging element for converting a subject image formed by the imaging lens into an electric signal, and means for converting an output signal of the imaging element into a video signal for recording. A video camera of a body type, comprising means for recording information representing geometric distortion of the imaging lens on a recording medium common to the video signal or a recording medium different from the video signal. 8. A video camera comprising an imaging lens, an imaging element for converting a subject image formed by the imaging lens into an electric signal, and means for converting an output signal of the imaging element into a video signal for recording. A video camera comprising means for superimposing information indicating geometric distortion of the imaging lens on a video signal or outputting the information separately from the video signal. 9. A camera system in which an imaging lens can be replaced, wherein the imaging lens stores information indicating geometric distortion of a subject image formed by the imaging lens, the stored information and the camera. A camera system comprising: means for calculating and generating information indicating distortion from the above state; and means for reading the information from the camera side. 10. The information of color magnification of one interchangeable lens is transmitted as information indicating a reference color and magnification of an image of another color with respect to an image of that color. The video camera described in 2 or 7 or 8. 11. The color magnification information of one interchangeable lens is not transmitted for a reference color, but only the magnification and color information of an image of another color with respect to that color is transmitted. The video camera according to claim 2, 7 or 8. 12. The video camera according to claim 7, wherein the geometric distortion information to be transmitted or recorded is distortion of an imaging lens.