JP2001211456A - Image processing method and image processing unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image processing unit that can obtain an image with high quality by applying luminance distortion correction and color difference correction to a picked-up image. SOLUTION: The image processing unit is provide with an image pickup device 14 that photographs an object and a computer 16 that applies image processing to an image photographed by the image pickup device, the computer analyzes (17) an image of a reference object 11 which is photographed by the device 14 and whose entire face is uniform in lightness plain white, stores correction data 19 used to correct the luminance of the image and distortion of the color difference, and corrects (111) the luminance and the color difference of the image of the object 110 photographed by the image pickup device by using the correction data. By correcting distortion in the luminance in the middle and the surrounding of the image due to a lens 13 and also the coloring, an image with high image quality can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing method for processing an image photographed by a digital camera, and an image processing apparatus and an image pickup apparatus.
This is to obtain a high quality image.

[0002]

2. Description of the Related Art Conventionally, in a small camera, an external light is converged by using a small lens and an image is obtained by a solid-state image pickup device. Distortion occurs in which the peripheral portion of the image becomes darker than the central portion, which causes the image quality to be significantly reduced.

Japanese Patent Laid-Open Publication No. Hei 10-97617 discloses a shading processing method for correcting such a deviation in luminance level. In this method, a white reference image and a black reference image are photographed prior to photographing of a target object, and shading correction data for correcting a luminance difference between a central portion and a peripheral portion of the image based on the video data. create. Next, the target object is photographed, and the video data is corrected based on the shading correction data.

[0004] By doing so, it is possible to correct the difference in luminance between the central portion and the peripheral portion of the image caused by optical distortion of the lens.

[0005]

However, in the conventional shading correction, only luminance correction is performed.
There is a disadvantage that the image after correction becomes whitish. This is because the color component is relatively reduced by performing the correction for increasing the luminance component around the image.

SUMMARY OF THE INVENTION The present invention has been made to solve the conventional problems, and has as its object to provide an image processing method capable of obtaining a high-quality image, and to provide an apparatus to which the method is applied. I have.

[0007]

Therefore, according to the image processing method of the present invention, a solid white reference object is photographed with uniform brightness over the entire surface, and digital data of the image is analyzed to correct each pixel of the image. Data is created, and the correction data is added to the luminance and color difference data of each pixel of an image of an image of a subject to correct distortion of the image luminance and color difference.

Further, the image processing apparatus of the present invention includes an imaging device for photographing a subject and a computer for image-processing an image photographed by the imaging device.
An image of a solid white reference subject with uniform brightness over the entire surface captured by the imaging device is analyzed, and correction data for correcting distortion of the luminance and color difference of the image is created and held, and captured by the imaging device. The luminance and the color difference of the image of the subject are corrected using the correction data.

Further, the image pickup apparatus of the present invention accepts correction data for correcting distortion of luminance and color difference of an image, which is analyzed from an image obtained when a solid white reference object is photographed with uniform brightness over the entire surface. The configuration is such that distortion of luminance and color difference of an image when recording and photographing a subject is corrected using the correction data.

[0010] With this configuration, it is possible to obtain a high-quality image in which distortion of luminance caused by the lens is corrected and color tone is corrected.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In an image processing method according to the present invention, first, a reference object of solid white color with uniform brightness over the entire surface is imaged by a camera, the image is analyzed by a computer, and correction profile data of the image is obtained. Create and record this.

When the subject is photographed by the camera,
The luminance and color difference information of the image is corrected using the correction profile data.

FIG. 1 schematically illustrates this image processing method. Solid white reference subject with uniform brightness over the entire surface
When the camera 11 captures the image 11, the image 12 is generally bright at the center of the image and dark at the periphery because of the optical distortion caused by the lens 13. The distorted image data 15 is taken into the computer 16, the luminance information is analyzed (17), and correction profile data 19 is created and recorded in the recording device 18.

Thereafter, an image of the subject 110 taken by the camera 14 is taken into the computer 16, and a correction process 111 for luminance and color difference of each pixel is performed based on the recorded correction profile data 19.

By displaying the corrected image data 112 on the monitor 113, it is possible to obtain a high-quality image in which there is no difference in luminance between the central portion and the peripheral portion of the image and the color tone is corrected.

FIG. 2 shows a procedure for creating correction profile data.

Step 21: The magnitude of the luminance information of each pixel of the reference object is compared for all the pixels, and the maximum value Ymax of the luminance information is obtained.

Step 22: Next, a correction coefficient of each pixel is calculated based on Ymax and luminance information Y (x, y) of each pixel.

The correction coefficient of each pixel is calculated by, for example, the following (Equation 1). K (x, y) = {Ymax / Y (x, y) -1} * a + 1 (Equation 1) where K (x, y): correction coefficient of point at coordinate (x, y) Ymax: all Maximum luminance value Y (x, y) on the screen: luminance of a point at coordinates (x, y) a: coefficient (0 to 1) for adjusting the intensity of correction.

By repeating this for all pixels,
Correction profile data for all pixels can be created.

FIG. 3 shows a processing procedure for correcting the luminance of the image of the subject.

Step 31: In this correction processing, the luminance is corrected by integrating the correction profile data with the luminance information of the image of the subject. By repeating this for all pixels, the luminance is corrected.

FIG. 4 is a graph showing an example of a change in luminance due to correction. The luminance of the image before correction tends to decrease as the distance from the focal point of the lens increases (41).
However, this relationship is not constant due to distortion of the individual lens and displacement of the optical axis of the lens.

By multiplying each pixel by the correction coefficient obtained by (Equation 1), it is possible to correct a decrease in luminance around the image as indicated by 42. The correction becomes stronger as the coefficient a for adjusting the correction intensity is closer to 1, and the graph becomes closer to a straight line. As described above, by performing the luminance correction using the correction profile data, it is possible to obtain an image having no difference in luminance between the central part and the peripheral part.

FIG. 5 shows a processing procedure for correcting the color difference. Image information is divided into luminance information and color difference information. The information on the color difference is expressed by an equation of the difference between the color component and the luminance component as shown in the following (Equation 2) and (Equation 3). rY (Equation 2) bY (Equation 3) Here, r: a red component, b: a blue component, and Y: a luminance component.

When the luminance information is corrected using the correction profile data obtained by the above method, since the luminance component increases, the color component relatively decreases and the image becomes whitish. Therefore, Step 51: Integrate the correction profile data with the luminance information of the image of the subject, and Step 52: Integrate the correction profile data also with the color difference information of each pixel.

By repeating this process for all the pixels, it is possible to obtain an image in which the hue has been corrected together with the luminance.

As described above, the correction profile data is created from the information of the reference subject, and the program defining the operation of correcting the luminance and color difference distortion of the subject is recorded on the recording medium by using the correction profile data. By causing a computer to read the program on the recording medium, the image processing method of the present invention can be executed.

Further, it is also possible to hold correction profile data created by a computer in a camera and to perform correction of luminance and color difference inside the camera.

FIG. 6 schematically shows a mode in which image processing is performed in such a mode. A solid white reference object 61 is photographed with a camera 64, and the image data 67 is taken into a computer 68, the luminance information is analyzed (69), and correction profile data 66 is created. The profile data 66 is transferred to the camera 64 and recorded on the recording device 65 of the camera 64.

Thereafter, the camera 64 that has photographed the subject 611
Performs correction processing 612 on the image information of the subject 611 using the correction profile data 66, and outputs image information 613 in which luminance and color difference have been corrected. Computer 68
By performing only output processing to the monitor 614, a corrected image can be obtained.

[0032]

As is apparent from the above description, according to the image processing method of the present invention, correction profile data is created and recorded from the data of the reference subject, and the brightness and chrominance are used for the image of the subject by using this data. Is corrected, it is possible to correct the optical distortion due to the lens, the individual difference of the lens, and the distortion of the image due to the shift of the optical axis when the lens is attached, and a high quality image can be obtained.

Further, an image pickup apparatus that records the correction profile data therein can output a high-quality image in which luminance and color difference have been corrected.

[Brief description of the drawings]

FIG. 1 is a block diagram schematically showing an image processing method according to an embodiment of the present invention;

FIG. 2 is a flowchart illustrating a procedure of a correction profile data creation process according to the embodiment;

FIG. 3 is a flowchart illustrating a procedure of a brightness correction process according to the embodiment;

FIG. 4 is a graph showing a change in luminance due to a luminance correction process;

FIG. 5 is a flowchart showing a procedure of a luminance and color difference correction process according to the embodiment;

FIG. 6 is a block diagram schematically illustrating an image processing method when performing a correction process in the camera of the embodiment.

[Explanation of symbols]

 11, 61 Reference subject 12, 62 Video 13, 63 Lens 14, 64 Camera 15, 67 Image data 16, 68 Computer 17, 69 Brightness information analysis processing 18 Recording device 19, 66 Correction profile data 65 Recording device 110, 611 Subject 111 , 612 Correction processing 112, 613 Corrected image data 113, 614 Monitor 610 Correction profile data returned to camera

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Etsumi Rokutobe 3-1, Tsunashimahigashi 4-chome, Kohoku-ku, Yokohama-shi, Kanagawa Prefecture F-term (reference) 5C022 AB51 AC42 AC54 AC69 5C065 AA01 BB01 BB06 BB23 CC02 CC03 CC09 DD01 EE12 GG15 GG23 GG32 5C066 AA01 AA11 CA07 CA08 EA05 EA07 EA13 EC03 GA02 GA05 GA32 GA33 GB01 HA01 JA01 KA12 KD01 KD06 KE03 KE16 KM02

Claims (7)

[Claims] An image of a solid white reference subject with uniform brightness over the entire surface is analyzed, digital data of an image of the reference subject is analyzed to create correction data for each pixel of the image, and an image of the subject photographed is obtained. An image processing method, wherein the correction data is added to the luminance and color difference data of each pixel to correct distortion of the image luminance and color difference. 2. The method according to claim 1, wherein a point at which the luminance of the image of the reference subject is the maximum is set as a reference point, and the correction data of each pixel is calculated based on a ratio of the luminance to the reference point. The image processing method described in the above. 3. An image of the reference subject taken by an imaging device is analyzed by a computer, the calculated correction data is recorded by the computer, an image of the subject taken by the imaging device is taken into the computer, and 3. The image processing method according to claim 1, wherein the computer corrects the distortion of the luminance and the color difference. 4. An image of the reference subject photographed by an imaging device is analyzed by a computer, the calculated correction data is recorded by the imaging device, and distortion of luminance and color difference of the image of the subject photographed by the imaging device is calculated. The image processing method according to claim 1, wherein the correction is performed by the imaging device. 5. An image capturing apparatus for capturing an image of a subject, and a computer for performing image processing on an image captured by the image capturing apparatus, the computer comprising: Analyzing the image of the white reference subject, creating and holding correction data for correcting the distortion of the brightness and color difference of the image, and using the correction data to calculate the brightness and color difference of the image of the subject captured by the imaging device. An image processing apparatus, wherein the image processing apparatus corrects the image. 6. An image obtained by receiving and recording correction data for correcting distortion of luminance and color difference of an image, which is analyzed from an image obtained when a solid white reference object is photographed with uniform brightness over the entire surface, and photographed. An image pickup apparatus for correcting distortion of brightness and color difference of an image at the time using the correction data. 7. A procedure for creating correction data for correcting the luminance and color difference of each pixel from image data of a solid white reference subject with uniform brightness over the entire surface, and using each pixel of the subject image using the correction data. And a computer-readable recording medium storing a program defining a procedure for correcting the luminance and color difference of the image.