CN105812661B - A kind of digital camera uniformity correcting method based on light box and gray card - Google Patents
A kind of digital camera uniformity correcting method based on light box and gray card Download PDFInfo
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- CN105812661B CN105812661B CN201610150471.XA CN201610150471A CN105812661B CN 105812661 B CN105812661 B CN 105812661B CN 201610150471 A CN201610150471 A CN 201610150471A CN 105812661 B CN105812661 B CN 105812661B
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- digital camera
- gray card
- light source
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- card
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N23/00—Cameras or camera modules comprising electronic image sensors; Control thereof
- H04N23/60—Control of cameras or camera modules
- H04N23/68—Control of cameras or camera modules for stable pick-up of the scene, e.g. compensating for camera body vibrations
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N17/00—Diagnosis, testing or measuring for television systems or their details
- H04N17/002—Diagnosis, testing or measuring for television systems or their details for television cameras
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N23/00—Cameras or camera modules comprising electronic image sensors; Control thereof
- H04N23/10—Cameras or camera modules comprising electronic image sensors; Control thereof for generating image signals from different wavelengths
- H04N23/13—Cameras or camera modules comprising electronic image sensors; Control thereof for generating image signals from different wavelengths with multiple sensors
- H04N23/16—Optical arrangements associated therewith, e.g. for beam-splitting or for colour correction
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- Engineering & Computer Science (AREA)
- Multimedia (AREA)
- Signal Processing (AREA)
- Health & Medical Sciences (AREA)
- Biomedical Technology (AREA)
- General Health & Medical Sciences (AREA)
- Color Television Image Signal Generators (AREA)
Abstract
The invention discloses a kind of digital camera uniformity correcting method based on light box and gray card.Standard gray card is positioned in light box by this method, translates the image for obtaining standard color card by way of camera is repeatedly shot in image different location vertical optical axis, homogeneity correction coefficient is mathematically obtained finally by difference or fitting.The method of the present invention exchanges the spatially uniform of light source for the time stability of light source, overcome traditional digital cameras uniformity test and correction must be in the limitation using such as integrating sphere uniform source system, the scope of application for considerably increasing test and correcting digital camera imaging uniformity, also avoid as metamerism phenomenon that color filter type integrating sphere light source generates and caused by measurement error.
Description
Technical field
The present invention relates to optical imagery, digital image processing fields, more particularly to one kind being based on light box and gray card
The method for substituting the digital camera imaging homogeneity corrections of special uniform source of light device such as integrating sphere.
Background technology
Currently, digital camera is widely used, it is used not only for captured image recording landscape, also in scientific research
Field is used as the colour examining equipment of imaging type.But digital camera imaging and imperfect, one of them typical imaging phenomenon is exactly
The heterogeneity of imaging.Since (illuminance of off-axis image point is with field angle for the dark angle of cosine of the vignetting stop of camera lens, off-axis image point
The biquadratic of cosine and reduce), the common work of image-forming component (such as CCD or CMOS) heterogeneity many factors of itself
With camera finally shows characteristic heterogeneous for the object imaging of a brightness uniformity.This non-homogeneous phenomenon of imaging
Also often referred as shade (shading).
ISO 17957 recommends the skiametry condition of digital camera imaging：A uniform field target is needed, it can
To represent the light source of three kinds of common lighting environments, i.e. averagely outdoor daylight, indoor incandescent lighting and room fluorescent lights illumination.In order to
Satisfactory test condition is generated, needs specially to build the lighting environment for testing shade.Industry is usually using integrating sphere
Uniform source of light system is to provide uniform illumination condition.On the one hand, such test condition and method significantly limit number
The test occasion of camera uniformity test and correction measures and correction is made troubles to be practical, especially for using wide-angle lens
The digital camera of head, the uniform illumination that provide enough large area are even more difficulty.On the other hand, it to realize as defined in ISO
Three kinds of exemplary light sources, at present integrating sphere often generate different types of light source by the way of incandescent lamp and optical filter combination,
Such light source can only ensure the accurate of colour temperature, can but cause potentially to measure inaccurate risk because of metamerism.
Invention content
In order to need to fill using special uniform source of light in overcoming the test bearing calibration of existing digital camera imaging uniformity
The inconvenience set, present invention offer is a kind of to use light box and standard gray card, tests the imagewise uniform of digital camera
With the method for correction.
The purpose of the present invention is achieved through the following technical solutions：A kind of digital phase based on light box and gray card
Machine uniformity correcting method, this approach includes the following steps：
(1) it arranges lamp box, places gray card：Lamp box is positioned in darkroom, gray card is positioned in lamp box, gray card and lamp box
Bottom surface is at fixed angle.
(2) a kind of light source for opening lamp box, preheats light source.
(3) camera position and parameter setting：Wait for that lamphouse light source preheating finishes, digital camera is positioned over gray card can be normal right
At burnt distance, digital camera optical axis is arranged perpendicular to gray card plane and fixes digital camera acquisition parameter so that digital camera
It is correct to grey exposed card；The digital camera acquisition parameters include ISO sensitivity, aperture, shutter and focal length.
(4) camera is shot：Digital camera is being translated and shot on optical axial plane so that n times were shot
Gray card spreads each position for appearing in image as far as possible；Extract the rgb value in gray card uniform illumination region in the i-th pictures
Average value RGBiAnd the center q in the regioni, i=1,2 ..., N.
(5) uniformity of prediction and correcting camera：The location variable q obtained according to step (4)iWith image response value RGBi,
It is obtained from location variable q by interpolation or fittingiIt is mapped to image response value RGBiAnticipation function f (), for image P
In any point p, obtain the homogeneity correction coefficient k (p)：
(6) the light source type for replacing lamp box, repeats step (2)~(5), until all kinds test of light source finishes, obtains
The digital camera is directed to the homogeneity correction coefficient of each light source.
The beneficial effects of the invention are as follows：The present invention uses light box and standard gray card, using multiple translation camera shooting
The mode of same standard color card obtains the homogeneity correction coefficient of image by the mathematical method of interpolation fitting.This method is with light
The time stability in source exchanges the spatially uniform of light source for, overcomes traditional digital cameras uniformity test and correction that must use
Such as limitation of integrating sphere uniform source system considerably increases the applicable model of test and correcting digital camera imaging uniformity
It encloses.
Description of the drawings
Fig. 1 is digital camera imaging uniformity test and the flow chart of correction；
Fig. 2 is experimental apparatus for testing figure；
Fig. 3 is the standard gray card picture shot in example；
Fig. 4 is that the test result of integrating sphere method and the method for the present invention compares figure, and (a) is using A light sources, is (b) to use
D65 light sources.
Specific implementation mode
Below with Nikon digital single-lens reflex camera D3x with Nikon AF-S Nikkor 24-120mm f/4G ED VR camera lenses,
Gray card in GretagMacbeth Spectralight III light boxs and X-rite ColorChecker Passport
For, it illustrates test and corrects the specific steps of the imagewise uniform of this digital camera.It should be noted that the present invention is not limited to
Nikon digital single-lens reflex camera, it is also unlimited as long as the digital camera that can get the output of image digitization format is suitable for the present invention
In GretagMacbeth light boxs or X-rite colour atlas, as long as stabilized light source can be provided and comprising spectral neutrality color lump
Colour atla is suitable for the present invention.
As shown in Figure 1, a kind of digital camera uniformity correcting method based on light box and gray card provided by the invention,
Include the following steps：
(1) it arranges lamp box, places gray card：As shown in Fig. 2, Spectralight III light boxs are positioned over darkroom
In, X-rite ColorChecker Passport colour atlas are turned into white balance target page (i.e. neutral grey page), are positioned over lamp box
In, gray card is with lamp box bottom surface at 45 angles so as to camera captures images.
(2) light source is selected：D65 light sources are selected from Spectralight III light boxs, open preheating.
(3) camera position and parameter setting：It waits for that the lamphouse light source preheating of step (2) finishes, D3x digital cameras is positioned over
At the distance 2.0m that gray card can normally focus, simultaneously fixed camera acquisition parameters are arranged as possible perpendicular to gray card plane in camera optical axis,
ISO sensitivity 200, F-number 4, shutter 1/80s, focal length 50mm so that digital camera is correct (Ev=0) to grey exposed card.
(4) camera is shot：By camera on optical axial plane from left to right from top to bottom translation (axial displacement is made
At theoretical error be only f Δs r/ [r (f+r)] × 100%, wherein r is object distance, and f is camera focus, and Δ r is that axial displacement is poor,
Δ r units are mm.Theoretical error caused by axial displacement is only Δ r/82000 × 100% in the present embodiment) so that 40 times
It shoots obtained gray card and spreads each position for appearing in image as far as possible.Extract gray card uniform illumination area in the i-th pictures
The average value of the rgb value in domain, is denoted as RGBiAnd the center in the region, it is denoted as qi, i=1,2 ..., 40.
(5) uniformity of prediction and correcting camera：The location variable qi and image response value obtained according to step (4)
RGBi, i=1,2 ..., 40, by two dimension a cube interpolation method obtain from location variable qiIt is mapped to image response value RGBiIt is pre-
It surveys function f () and the homogeneity correction coefficient k (p) is obtained for any point p in image P：
In formula, max () is maximizing function.
(6) Spectralight III light boxs are replaced to A light sources, are repeated (2)~(5) step, are obtained the number phase
Homogeneity correction coefficient of the eedle to various light sources.
Experimental result is by taking green channel (channels G) as an example, as shown in figure 4, the experimental result and integrating sphere of the method for the present invention
The correction coefficient obtained under uniform source of light system is very close.
Claims (1)
1. a kind of digital camera uniformity correcting method based on light box and gray card, which is characterized in that this method include with
Lower step：
(1) it arranges lamp box, places gray card：Lamp box is positioned in darkroom, gray card is positioned in lamp box, gray card and lamp box bottom surface
At fixed angle；
(2) a kind of light source for opening lamp box, preheats light source；
(3) camera position and parameter setting：It waits for that lamphouse light source preheating finishes, digital camera is positioned over what gray card can normally focus
At distance, digital camera optical axis is arranged perpendicular to gray card plane and fixes digital camera acquisition parameter so that digital camera is to ash
Exposed card is correct；The digital camera acquisition parameters include ISO sensitivity, aperture, shutter and focal length；
(4) camera is shot：Digital camera is being translated and shot on optical axial plane so that the gray card that n times are shot
The each position for appearing in image is spread as far as possible；Extract the average RGB responses in gray card uniform illumination region in the i-th pictures
Value RGBiAnd the center q in the regioni, i=1,2 ..., N；
(5) uniformity of prediction and correcting camera：The location variable q obtained according to step (4)iWith average RGB responses RGBi,
It is obtained from location variable q by interpolation or fittingiIt is mapped to average RGB responses RGBiAnticipation function f (), for figure
As any point p in P, the homogeneity correction coefficient k (p) is obtained：
(6) the light source type for replacing lamp box, repeats step (2)~(5), until all kinds test of light source finishes, obtains the number
Code camera is directed to the homogeneity correction coefficient of each light source.
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| CN201610150471.XA CN105812661B (en) | 2016-03-16 | 2016-03-16 | A kind of digital camera uniformity correcting method based on light box and gray card |
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| CN105812661A CN105812661A (en) | 2016-07-27 |
| CN105812661B true CN105812661B (en) | 2018-07-17 |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN108120680B (en) * | 2017-12-19 | 2019-11-22 | 清华大学 | The stray light minimizing technology and device of micro-imaging based on photoelectric characteristic priori |
| CN109889823B (en) * | 2019-04-08 | 2021-02-26 | 苏州莱测检测科技有限公司 | Detection method for detecting performance of stereoscopic vision imaging equipment |
| CN110275387A (en) * | 2019-07-02 | 2019-09-24 | 珠海达明科技有限公司 | A kind of camera flat field calibration platform and calibration method |
| CN111609998A (en) * | 2020-05-11 | 2020-09-01 | 歌尔股份有限公司 | Detection method and detection device for illumination uniformity and readable storage medium |
| CN113143521B (en) * | 2020-12-07 | 2022-06-24 | 深圳云甲科技有限公司 | Color correction method for image acquired by three-dimensional scanning equipment |
Citations (4)
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|---|---|---|---|---|
| EP1561338A1 (en) * | 2002-10-09 | 2005-08-10 | Diane Wallace | System and method for effectively performing a white balance procedure for electronic cameras |
| CN101907488A (en) * | 2010-07-28 | 2010-12-08 | 中国建筑科学研究院 | Image brightness meter based on digital camera and measuring method thereof |
| CN103389162A (en) * | 2012-11-26 | 2013-11-13 | 中国计量学院 | Reflective object color measuring instrument with color digital camera |
| CN104168475A (en) * | 2014-08-15 | 2014-11-26 | 浙江大学 | Digital-camera-parameter-variable imaging type method for obtaining color tristimulus value |
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Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP1561338A1 (en) * | 2002-10-09 | 2005-08-10 | Diane Wallace | System and method for effectively performing a white balance procedure for electronic cameras |
| CN101907488A (en) * | 2010-07-28 | 2010-12-08 | 中国建筑科学研究院 | Image brightness meter based on digital camera and measuring method thereof |
| CN103389162A (en) * | 2012-11-26 | 2013-11-13 | 中国计量学院 | Reflective object color measuring instrument with color digital camera |
| CN104168475A (en) * | 2014-08-15 | 2014-11-26 | 浙江大学 | Digital-camera-parameter-variable imaging type method for obtaining color tristimulus value |
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