JP2002262171A - Image pickup device and its control method, image reproducing device and its control method, and video system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electronic camera that can correct luminous quantity with high accuracy and obtain excellent image quality. SOLUTION: A ROM 19 stores information of distortion of a photographing lens of a variator 3 and a focus lens group 4 and an arithmetic circuit 10 detects a state of the photographing lens. Then the arithmetic circuit 10 detects the distortion aberration information when an object is photographed under the detected state of the lens, the distortion is corrected on the basis of the detection information and a change in the luminous quantity distribution due to the image distortion is corrected by making an optional image height of the photographed image as a reference.

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 a video camera, a still camera or a silver halide camera, an image reproducing apparatus for reproducing a photographed image, a control method thereof, and a video system comprising a combination of these apparatuses. It is about.

[0002]

2. Description of the Related Art In general, the amount of light on an image forming surface of an image pickup device photographed by using a lens is such that peripheral portions are darker than central portions. This phenomenon occurs mainly due to the cosine fourth law and vignetting.

[0003] Conventionally, in order to correct the drop in the amount of light in the peripheral portion, for example, as disclosed in JP-A-6-165023, the position of a zoom lens, the position of a focus lens, and Based on the aperture value,
From the coefficient control circuit, the light amount ratio of the peripheral part to the central part on the light receiving surface of the imaging device such as a CCD is obtained, the reciprocal thereof is output as a correction coefficient, and the multiplication circuit multiplies the video signal by the correction coefficient. The light amount distribution of the image plane is electrically corrected.

[0004]

However, in the conventional imaging apparatus as described above, when the phenomenon that the brightness of the peripheral portion becomes darker than the brightness of the central portion of the image forming surface is electrically corrected, the cosine 4 is used. It is not sufficient to determine the correction coefficient only with the parameters of the power law and the vignetting, and high-precision light quantity correction cannot be expected. This is because the light amount distribution also fluctuates due to distortion.

[0005] In particular, in an image pickup system using an ultra wide angle lens,
Since the amount of peripheral light drop is large and distortion is relatively likely to remain, the amount of change in light distribution due to distortion is a value that cannot be ignored.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and provides an image pickup apparatus capable of performing high-precision light quantity correction, making the light quantity level of the entire screen uniform, and obtaining good image quality. It is an object of the present invention to provide a control method, an image reproducing device, a control method thereof, and a video system.

[0007]

According to the present invention, there is provided an image pickup apparatus, an image reproducing apparatus, and an image system, comprising: a distortion storage means for storing information on distortion of a photographic lens; and a lens state for detecting a state of the photographic lens. Detecting means; distortion detecting means for detecting distortion information when the image is taken based on information from the lens state detecting means; and distortion correction for correcting distortion based on the distortion information from the distortion detecting means. And light amount distribution correcting means for correcting a change in light amount distribution due to image distortion based on an arbitrary image height of a captured image.

In the above arrangement, when correcting the distortion, correcting the light amount distribution based on the distortion aberration information, correcting the light amount distribution based on the pupil information and the distortion information, The pupil information contains the light receiving rate of the image sensor. The distortion is a function Dist (y) of the image height y ′, and the light source is I
Then, the light quantity distribution correction coefficient K due to the distortion is as follows: K = (I + D) ³ / (I + D−y ′ · (dD / dy ′)) (1)

[0009]

Embodiments of the present invention will be described below with reference to the drawings.

First, before describing the embodiments, the light amount distribution on the imaging surface of the above-described image sensor will be described with reference to the drawings.

The light amount distribution (image surface illuminance ratio) of the image forming surface of the image pickup device is determined by the cosine fourth power rule of the lens, vignetting,
It is determined by distortion. In an imaging system using a solid-state image sensor such as a CCD, the effect of the light receiving rate of the solid-state image sensor is further added to the light amount distribution of image data captured by the device.

Here, the image plane illuminance ratio R on the image plane will be described.

FIG. 10 shows the image forming relationship of the lens. The light beam from the area dA on the object plane 20 becomes an area dS on the incident reference plane 21 of the optical system 22, becomes an area dS 'on the emission reference plane 23, and becomes dA' on the image plane 24.

The light beam dF included in the light beam passing through dS is:
From the luminous intensity I, the luminance B, the angle θ formed between the light beam and the optical axis, and the solid angle dW for dS from dA, it can be expressed by the following equation.

DF = Idw (2) = Bd · A · cos θ · dW (3) Here, it is assumed that the object surface 20 is a perfect diffusion surface.

Assuming that the distance from dA to dS is r, the following equation holds.

Dω = dS · cos θ / r ² (4) Assuming that the distance between the object plane and the incident reference plane is e, the following equation is established.

R = e / cos θ (5) df = B / e ² · cos ⁴ θ · dA · dS (6) If there is no light loss due to the lens, the light flux dF ′ reaching the image plane dA ′ is dF And the image plane illuminance distribution E (θ)
Can be expressed by the following equation.

E (θ) = B · ∫ _S (cos ⁴ θ / e ² / (dA ′ / dA)) dS (7) When there is no distortion, dA ′ / dA is constant and the square of the lateral magnification. , But generally do not match due to distortion.

FIG. 11 shows the relationship between dA and dA '.

In FIG. 11, y and y 'are the heights of the object and the corresponding image.

Assuming that the minute area on the object plane is dA and the minute area on the image plane is dA ', the following equation is established.

DA = y · δ · dy dA ′ = y ′ · δ · dy ′ (8) dA ′ / dA = y ′ · dy ′ / (y · dy) (9) , The following equation holds.

[0024] E (θ) = B · ∫ S (cos 4 θ / (e 2 ·
Table of y '/ y · dy' / dy)) dS ... (10) object point of height y, y image height for it when ', an ideal image height y' is _0, the distortion D in the following equation Is done.

D = (y′−y ′ ₀ ) / y ′ ₀ (11) Assuming that the paraxial magnification is β, the following equation is established.

Y ′ ₀ = β (12) y = y ′ / (β · (I + D)) (13) dy / dy ′ = (I + D−y ′ · (dD / dy ′)) / (β · (I + D)) (14) If the equation (14) is substituted into the equation (10) and it is considered that the opening S is not so large and θ is almost constant, the following equation is established.

E (θ) = BS / (e ² · β ² ) · cos ⁴ θ · (I + D−y ′ · (dD / dy ′)) / (I + D) ³ (15) When θ = 0 At this time, since y = 0 and D = 0, if the cross-sectional area of the on-axis light beam is S ₀ , the following equation is established.

E (0) = B · S ₀ / (e ² · β ² ) (16) Therefore, the image plane illuminance distribution R can be expressed as follows.

R = E (θ) / E (0) = S / S ₀ · cos ⁴ θ · (I + D−y ′ · (dD / dy ′)) / (1 + D) ³ (17) Vignetting correction term W _vig can be expressed by the following equation, where V is the _vignetting .

W _vig = S / S ₀ = IV (18) Angle of view weight correction term W _ang , W _ang = cos ⁴ θ (19) Distortion correction term W _dist , W _dist = (I + D− y ′ · (dD / dy ′)) / (I + D) ³ (20), the image plane illuminance ratio R is expressed by the following equation.

R = W _vig · W _ang · W _dist (21) Accordingly, the light quantity distribution correction coefficient K for correcting the component due to the distortion is K = I / W _ang = (I + D) ³ / (I + D-y) '· (DD / dy')) (22)

Next, the effect of the light receiving rate of the solid-state imaging device will be described.

A correction term W _ccd based on the light receiving rate of the solid-state image sensor.
_Wccd = (1-E) (23) where E is the vignetting rate.

The vignetting rate is determined from the position information of the condenser lens formed on the light receiving surface of the solid-state image pickup device such as a CCD and the exit pupil of the lens.

[0035] Then, the intensity distribution R _ccd of light received by the solid-state imaging device, formula (22), the equation _{(23), R ccd = R} · W ccd = W vig · W ang · W dist · W ccd ... (24).

(First Embodiment) Hereinafter, a first embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of an imaging apparatus according to the first embodiment.

The image pickup light from the subject is transmitted to a lens group (not shown) and a variator (zoom lens group) in the image pickup apparatus main body 1.
3, through the focus lens group 4, the CC
An image is formed on the light receiving surface of D5.

The signal from the CCD 5 is sampled by the CDS circuit 11, gain-adjusted by the AGC circuit 13, digitized by the A / D converter 13, and sent to the image processing circuit 16.

On the other hand, a signal from the encoder 6 arranged in the variator 3 is input to a zoom position detecting circuit 8, which detects a zoom position and sends it to an arithmetic circuit 10.

A signal from the encoder 7 arranged in the focus lens group 4 is input to a focus position detection circuit 9, which detects a focus position and sends it to an arithmetic circuit 10.

Here, in this embodiment, the ROM 19 constitutes a distortion storage means for storing information on the distortion of the variator 3 and the photographing lens of the focus lens group 4. Further, a lens state detecting means for detecting a state of the photographing lens, a distortion aberration detecting means for detecting distortion information when photographing is performed based on information from the lens state detecting means, The arithmetic circuit 10 includes a distortion correction unit that corrects distortion based on distortion aberration information and a light amount distribution correction unit that corrects a change in light amount distribution due to image distortion based on an arbitrary image height of a captured image. ing.

The operation performed by the arithmetic circuit 10 will be described below.

The ROM 19 stores data on the amount of vignetting, the amount of distortion, and the vignetting rate of the CCD 5 at each zoom position and focus position.

First, data corresponding to the zoom position and the focus position obtained by the zoom position detection circuit 8 and the focus position detection circuit 9 are read from the ROM 19. Then, based on the read data, the luminous intensity I of the light amount distribution is calculated by Expression (22), and the reciprocal thereof is sent to the image processing circuit 16 as a correction coefficient.

FIG. 2 shows the light quantity distribution component based on the cosine fourth law determined by equation (9), FIG. 3 shows the light quantity distribution component obtained by vignetting determined by equation (18), and FIG.
FIG. 5 shows the light amount distribution component due to the distortion obtained by the equation (20), and FIG. 6 shows the light receiving rate of the CCD 5 obtained by the equation (23).

FIG. 7 shows the light quantity distribution R _ccd obtained by the equation (24), and FIG. 8 shows the correction coefficient which is the reciprocal thereof.

The image processing circuit 16 corrects the image data from the A / D converter 13 on the basis of the light amount distribution correction coefficient from the arithmetic circuit 10 and outputs the result to the LCD 14.
Or to the memory 15.

As described above, in the present embodiment, it is possible to electrically correct a light drop in the peripheral portion of the digital camera with high precision. For this reason, the light amount level of the entire screen becomes uniform, and excellent image quality with very high accuracy can be obtained.

(Second Embodiment) Hereinafter, a second embodiment of the present invention will be described with reference to the drawings.

FIG. 9 is a block diagram showing an imaging apparatus according to the second embodiment.

In FIG. 1, reference numeral 1 denotes a main body of the imaging apparatus, and reference numeral 2 denotes a lens unit. The lens unit 2 includes a lens group (not shown), a variator 3, a focus lens group 4, an encoder 6, an encoder 7, a zoom position detection circuit 8, and a focus position detection circuit 9. The lens unit 2 is replaceable. Other configurations are the same as those in FIG.

The operation performed by the operation circuit 10 will be described below.

The ROM 19 stores information on a vignetting amount V, a distortion amount D, and a pupil position at each zoom position and focus position.

The image plane illuminance ratio R at the zoom position and the focus position obtained by the zoom position detection circuit 8 and the focus position detection circuit 9 is obtained by the above equation (21).

The ROM 18 has a CCD based on the pupil position.
The vignetting rate E of 5 is stored.

The value of the image plane illuminance ratio R and the pupil position information are sent to the image processing circuit 16 via the communication circuit 17, and the intensity distribution R of the light received by the CCD 5 is calculated by the above-mentioned equation (24).
_ccd is calculated, and the correction coefficient is the reciprocal thereof.

The image processing circuit 16 corrects the image data from the A / D converter 13 on the basis of the light amount distribution correction coefficient from the arithmetic circuit 10 and outputs the result to the LCD 14 or the memory 1.
Output to 5

Even with such a configuration, the same operation and effect as those of the embodiment of FIG. 1 can be obtained, and the light amount can be corrected with high accuracy.

The calculation of the light amount distribution change data may be performed in the lens unit 2 or in the image pickup apparatus main body 1.

FIG. 12 is a flowchart showing the flow of the processing of the above-described embodiment. The control processing shown in this flowchart is stored in advance by the CPU (not shown) in the imaging device main body 1 or the lens unit 2. It is executed according to a program.

At the start of photographing, information on the distortion of the photographing lens is stored in the memory 19 (S1), the information on the photographing lens is detected (S2), and the photographing is performed based on the detection result. The distortion information is detected (S3).
Then, the distortion is corrected based on the detection result of the distortion (S4), and the change in the light amount distribution is corrected (S5).

[0063]

As described above, according to the present invention,
By performing the light amount correction described above, highly accurate light amount correction can be performed. Therefore, the light amount level of the entire screen becomes uniform, and very good image quality can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of an imaging apparatus according to a first embodiment.

FIG. 2 is a diagram showing a light quantity distribution component based on the cosine fourth power rule;

FIG. 3 is a diagram showing a light amount distribution component by vignetting.

FIG. 4 is a diagram showing a distortion amount;

FIG. 5 is a diagram showing a light amount distribution component due to distortion.

FIG. 6 is a diagram showing a light receiving ratio of a CCD.

FIG. 7 is a diagram showing a light amount distribution.

FIG. 8 is a diagram showing a correction coefficient.

FIG. 9 is a block diagram illustrating a configuration of an imaging apparatus according to a second embodiment.

FIG. 10 is a diagram showing an image forming relationship of a lens;

FIG. 11 is a diagram showing a relationship between an object plane and an area of an image plane.

FIG. 12 is a flowchart illustrating a flow of a process according to the embodiment;

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 imaging apparatus main body 2 lens unit 3 variator 4 focus lens group 5 CCD (imaging element) 6 encoder 7 encoder 8 zoom position detection circuit 9 focus position detection circuit 10 arithmetic circuit 11 CDS circuit 12 AGC circuit 13 A / D converter 14 LCD 15 Memory 16 Image processing circuit 17 Communication circuit 18 ROM 19 ROM

Claims (30)

[Claims] 1. A distortion aberration storage means for storing information on distortion of a photographic lens, a lens state detection means for detecting a state of the photographic lens, and a lens for detecting an image based on information from the lens state detection means. A distortion detecting means for detecting distortion information, a distortion correcting means for correcting distortion based on the distortion information from the distortion detecting means, and an amount of light due to image distortion based on an arbitrary image height of a captured image. An image pickup apparatus comprising: a light amount distribution correction unit for correcting a change in distribution. 2. The distortion correcting means, when correcting the distortion,
2. The imaging apparatus according to claim 1, wherein the light amount distribution is corrected based on the distortion information. 3. The imaging apparatus according to claim 1, wherein the light amount distribution correction unit corrects the light amount distribution based on pupil information and distortion information. 4. The imaging apparatus according to claim 2, wherein the pupil information includes pupil vignetting information. 5. The imaging device according to claim 2, wherein the pupil information includes a light receiving rate of an imaging device. 6. The distortion is a function D of the image height y ', and the light source is I
Then, the light quantity distribution correction coefficient due to the distortion is (I + D)
The imaging device according to claim 1, wherein ³ / (I + D−y ′ · (dD / dy ′)). 7. An image reproducing apparatus for reproducing a photographed image, comprising: a distortion aberration storage means for storing information on a distortion of a photographing lens; a lens state detecting means for detecting a state of the photographing lens; A distortion detection unit that detects distortion information when the image is captured based on the information from the detection unit; a distortion correction unit that corrects the distortion based on information from the distortion detection unit; An image reproducing apparatus comprising: a light amount distribution correction unit that corrects a change in light amount distribution due to image distortion based on an image height. 8. The distortion correcting means, when correcting the distortion,
The image reproducing apparatus according to claim 7, wherein the light amount distribution is corrected based on the distortion information. 9. The image reproducing apparatus according to claim 7, wherein the light amount distribution correcting means corrects the light amount distribution based on pupil information and distortion information. 10. The image reproducing apparatus according to claim 8, wherein the pupil information includes pupil vignetting information. 11. The image reproducing apparatus according to claim 8, wherein the pupil information includes a light receiving rate of an image sensor. 12. Assuming that the distortion is a function D of the image height y 'and the luminous intensity is I, the light quantity distribution correction coefficient due to the distortion is (I +
12. The image reproducing apparatus according to claim 8, wherein D) ³ / (I + Dy ′ · (dD / dy ′)). 13. A video system comprising an image pickup apparatus and an image reproducing apparatus for reproducing an image taken by the image pickup apparatus, wherein a distortion aberration storage means for storing information on distortion of a photographic lens, and a lens for detecting a state of the photographic lens. State detecting means, distortion detecting means for detecting distortion information when the image is taken based on information from the lens state detecting means, and distortion correcting means for correcting distortion based on information from the distortion detecting means And a light amount distribution correcting means for correcting a change in light amount distribution due to image distortion based on an arbitrary image height of a captured image. 14. The video system according to claim 13, wherein the distortion correcting means corrects the light amount distribution based on the distortion information when correcting the distortion. 15. The image system according to claim 13, wherein the light amount distribution correction means corrects the light amount distribution based on pupil information and distortion information. 16. The image system according to claim 14, wherein the pupil information includes pupil vignetting information. 17. The image system according to claim 14, wherein the pupil information includes a light receiving rate of an image sensor. 18. If the distortion is a function D of the image height y 'and the luminous intensity is I, the light amount distribution correction coefficient due to the distortion is (I +
18. The video system according to claim 14, wherein D) ³ / (I + Dy ′ · (dD / dy ′)). 19. storing information on distortion of a taking lens, detecting a state of the taking lens, detecting distortion information at the time of photographing based on the detection information of the lens state, and detecting the distortion of the taking lens; A method for controlling an imaging apparatus, comprising: correcting distortion based on detection information; and correcting a change in light amount distribution due to image distortion based on an arbitrary image height of a captured image. 20. The method according to claim 19, wherein when correcting the distortion, the light amount distribution is corrected based on the distortion aberration information. 21. The method according to claim 19, wherein the light amount distribution is corrected based on pupil information and distortion information. 22. The method according to claim 20, wherein the pupil information includes pupil vignetting information. 23. The method according to claim 20, wherein the pupil information includes a light receiving ratio of an image sensor. 24. Assuming that the distortion is a function D of the image height y ′ and the luminous intensity is I, the light quantity distribution correction coefficient due to the distortion is (I +
24. The method according to claim 20, wherein D) ³ /(I+Dy'.(dD/dy ')). 25. A control method of an image reproducing apparatus for reproducing a photographed image, wherein information on distortion of the photographing lens is stored, the state of the photographing lens is detected, and based on the detection information on the lens state. Detecting distortion information at the time of photographing, correcting distortion based on the detection information of the distortion, and correcting a change in light amount distribution due to image distortion based on an arbitrary image height of a photographed image. A method for controlling an image reproducing apparatus, comprising: 26. The method according to claim 25, wherein when correcting the distortion, the light amount distribution is corrected based on the distortion aberration information. 27. The method according to claim 25, wherein the light amount distribution is corrected based on pupil information and distortion information. 28. The method according to claim 26, wherein the pupil information includes pupil vignetting information. 29. The control method for an image reproducing apparatus according to claim 26, wherein said pupil information includes a light receiving ratio of an image pickup device. 30. Assuming that the distortion is a function D of the image height y 'and the luminous intensity is I, the light amount distribution correction coefficient due to the distortion is (I +
30. The method according to claim 26, wherein D) ³ / (I + Dy '. (DD / dy')).