CN112714300A - Color correction method based on spectral response under ultralow illumination - Google Patents
Color correction method based on spectral response under ultralow illumination Download PDFInfo
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- CN112714300A CN112714300A CN202011384481.2A CN202011384481A CN112714300A CN 112714300 A CN112714300 A CN 112714300A CN 202011384481 A CN202011384481 A CN 202011384481A CN 112714300 A CN112714300 A CN 112714300A
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- 230000003595 spectral effect Effects 0.000 title claims abstract description 48
- 230000004044 response Effects 0.000 title claims abstract description 45
- 238000005286 illumination Methods 0.000 title claims abstract description 17
- 238000000034 method Methods 0.000 title claims abstract description 17
- 238000001228 spectrum Methods 0.000 claims abstract description 41
- 230000010354 integration Effects 0.000 claims abstract description 9
- 238000009826 distribution Methods 0.000 claims description 6
- 238000003384 imaging method Methods 0.000 claims description 4
- 230000035945 sensitivity Effects 0.000 claims description 4
- 239000003086 colorant Substances 0.000 description 4
- 230000004297 night vision Effects 0.000 description 4
- 230000009467 reduction Effects 0.000 description 3
- 238000004364 calculation method Methods 0.000 description 2
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N9/00—Details of colour television systems
- H04N9/64—Circuits for processing colour signals
- H04N9/646—Circuits for processing colour signals for image enhancement, e.g. vertical detail restoration, cross-colour elimination, contour correction, chrominance trapping filters
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
- G01J3/46—Measurement of colour; Colour measuring devices, e.g. colorimeters
- G01J3/465—Measurement of colour; Colour measuring devices, e.g. colorimeters taking into account the colour perception of the eye; using tristimulus detection
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
- G01J3/46—Measurement of colour; Colour measuring devices, e.g. colorimeters
- G01J3/50—Measurement of colour; Colour measuring devices, e.g. colorimeters using electric radiation detectors
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Abstract
The invention discloses a color correction method based on spectral response under ultralow illumination, which comprises the following steps: acquiring a daylight spectrum in the day and a night light spectrum at night by using a spectrometer; acquiring a spectral response curve of a camera by using a monochromator and a spectrometer; calculating the integral of the daily spectrum and the spectral response curve and the integral of the night light spectrum and the spectral response curve; and respectively calculating the correction values of the RGB three-channel values according to the integration result to obtain the image after color correction. The invention can finish the spectrum correction of the image only by knowing the spectrum response curve of the camera and the spectrum curve that the acquired image is night light, and the required information amount is small.
Description
Technical Field
The invention belongs to the field of computer vision, and particularly relates to a color correction method based on spectral response under ultralow illumination.
Background
Under the condition of weak light, human eyes gradually lose the resolving power of colors, and even images of scenes cannot be obtained due to the reduction of sensitivity. The ultra-low illumination color restoration technology is characterized in that the characteristic that human eyes have higher resolution on color vision is utilized, and an image acquired under weak illumination is processed into a color image suitable for human eyes to observe, so that the performance of a night vision system and the observation effect of a night vision image are improved, and an observer can acquire more effective information. The method is based on the visual characteristics of human eyes, and a color correction algorithm under the ultra-low illumination is researched according to the change of an environment spectrum.
Based on the color vision principle of human eyes, the human eyes have three different cone-shaped photosensitive cells which respectively only generate visual reflection to the stimulation of the energy of red, green and blue spectrums. When the same object is illuminated by light sources with different energy spectral distributions, the colors seen are different. The difference of spectral distribution characteristics of sunlight, moonlight and starlight, and the difference of spectral curves of sunlight, moonlight and starlight should be an important reason why the color reduction capability of the CMOS imaging device is reduced at low illumination.
The true-color low-light-level image has the defects of low color reduction degree, high noise, large influence of colors on the environment and the like, and the existing color correction method cannot completely meet the requirement of color correction of the true-color low-light-level image. The automatic white balance method is greatly influenced by illumination and is easy to generate larger deviation; the gray world method is limited by scene colors and cannot be used for all scenes; the color correction method based on Retinex algorithm can generate large image noise and is not suitable for true-color low-light level images.
Disclosure of Invention
The invention aims to provide a color correction method based on spectral response under ultralow illumination.
The technical scheme for realizing the purpose of the invention is as follows: a color correction method based on spectral response under ultralow illumination comprises the following steps:
step 1: acquiring a daylight spectrum in the day and a night light spectrum at night by using a spectrometer;
step 2, acquiring a spectral response curve of the camera by using a monochromator and a spectrometer;
step 3, calculating the integral of the daily spectrum and the spectral response curve and the integral of the night light spectrum and the spectral response curve;
and 4, respectively calculating the correction values of the RGB three-channel values according to the integral result to obtain the color-corrected image.
Preferably, the specific steps of acquiring the spectral response curve of the camera by using the monochromator and the spectrometer are as follows:
aligning the light outlet of the integrating sphere with the light inlet of the monochromator, and aligning the true color camera with the light outlet of the monochromator;
adjusting the wavelength of a monochromator to a set initial value, setting a step length, and sequentially recording imaging data of a camera detector until a set final wavelength value is reached;
determining RGB values of the picture in different wave bands, and calculating a spectral response curve of the camera according to tristimulus values at different wavelengths and a spectral curve of the light source.
Preferably, the integral of the daily spectrum and the spectral response curve is calculated, and the specific formula of the integral of the night light spectrum and the spectral response curve is as follows:
er＝∫Pr(λ)Sr(λ)dλ
eg＝∫Pg(λ)Sg(λ)dλ
eb＝∫Pb(λ)Sb(λ)dλ
in the formula, Sr(λ)、Sg(λ)、Sb(λ) respectively represents the spectral sensitivity response characteristics, P, of the RGB three channels of the camerar(λ)、Pg(λ)、Pb(λ) is the RGB three-channel power spectrum distribution of daylight/night-day light.
Preferably, the calculation formula of the correction value of the RGB three-channel values is:
R′＝R*(edr/enr)
G′＝G*(edg/eng)
B′＝B*(edb/enb)
c＝R′+G′+B′
in the formula, edr、edg、edbAs a result of integration of the daytime spectrum with the spectral response curve of the camera, enr、eng、enbR, G, B is the integration result of the night spectrum and the camera spectrum response curve, and R ', G ' and B ' are the corrected RGB three-channel pixel values.
Compared with the prior art, the invention has the following remarkable advantages: (1) the invention has good prospect in the field of color low-light night vision; (2) the invention can finish the spectrum correction of the image only by knowing the spectrum response curve of the camera and acquiring the spectrum curve that the image is night sky light, and the required information amount is less; (3) the invention has small calculated amount and good real-time property.
The present invention is described in further detail below with reference to the attached drawing figures.
Drawings
FIG. 1 is a flow chart of a color correction method based on spectral response under ultra-low illumination.
Fig. 2 is an unprocessed night-day image captured by a true color camera.
Fig. 3 is a graph of the spectrum during the day.
Fig. 4 is a spectral curve of night sky light.
Fig. 5 is a spectral response curve of a camera.
Fig. 6 is an image corrected using the present invention.
Detailed Description
As shown in fig. 1, a color correction method based on spectral response under ultra-low illumination includes the following steps:
step 1, acquiring a daylight spectrum in the day and a night light spectrum at night by using a spectrometer.
Step 2, acquiring a spectral response curve of the camera by using a monochromator and a spectrometer;
in one embodiment, a spectrometer is used to measure the spectral curve of an integrating sphere light source;
aligning the light outlet of the integrating sphere with the light inlet of the monochromator, and aligning the true color camera with the light outlet of the monochromator;
and adjusting the wavelength of the monochromator to 380nm, setting the step length to be 10nm, and sequentially recording imaging data of the camera detector until the wavelength reaches 800 nm.
Determining RGB values of the picture in different wave bands, and calculating a spectral response curve of the camera according to tristimulus values at different wavelengths and a spectral curve of the light source.
Step 3, calculating the integral of the daily spectrum and the spectral response curve and the integral of the night light spectrum and the spectral response curve, wherein the specific calculation formula is as follows:
er＝∫Pr(λ)Sr(λ)dλ
eg＝∫Pg(λ)Sg(λ)dλ
eb＝∫Pb(λ)Sb(λ)dλ
in the formula, Sr(λ)、Sg(λ)、Sb(λ) respectively represents the spectral sensitivity response characteristics, P, of the RGB three channels of the camerar(λ)、Pg(λ)、Pb(lambda) is the RGB three-channel power spectrum distribution of sunlight/night sky light, er、eg、ebThe color of the image in the camera is represented by e, which is the integral of the spectral response of each color channel of the camera in the visible ranger、eg、ebThe sum of the three is the color distribution of the image.
And 4, respectively calculating correction values of RGB three-channel values according to the integration result in the step 3 to finish the color correction of the image, wherein the specific formula is as follows:
R′＝R*(edr/enr)
G′＝G*(edg/eng)
B′＝B*(edb/enb)
c＝R′+G′+B′
edr、edg、edbas a result of integration of the daytime spectrum with the spectral response curve of the camera, enr、eng、enbR, G, B is the integration result of the night spectrum and the camera spectrum response curve, and R ', G ' and B ' are the corrected RGB three-channel pixel values.
And synthesizing the color corrected image according to the corrected pixel values of the RGB three channels.
The invention can carry out color correction on the true-color low-light-level night vision image collected under ultralow illumination, so that the color of the night-day image of the scene is closer to the color of the scene under sunlight, the color observation rule of human eyes is better met, the color of the night-day image is similar to the color of the image scene commonly used in computer vision, and the subsequent target identification and target detection are facilitated.
Claims (4)
1. A color correction method based on spectral response under ultralow illumination is characterized by comprising the following steps:
step 1: acquiring a daylight spectrum in the day and a night light spectrum at night by using a spectrometer;
step 2: acquiring a spectral response curve of a camera by using a monochromator and a spectrometer;
and step 3: calculating the integral of the daily spectrum and the spectral response curve and the integral of the night light spectrum and the spectral response curve;
and 4, step 4: and respectively calculating the correction values of the RGB three-channel values according to the integration result to obtain the image after color correction.
2. The color correction method based on spectral response under ultralow illumination according to claim 1, wherein the specific steps of using the monochromator and the spectrometer to obtain the spectral response curve of the camera are as follows:
aligning the light outlet of the integrating sphere with the light inlet of the monochromator, and aligning the true color camera with the light outlet of the monochromator;
adjusting the wavelength of a monochromator to a set initial value, setting a step length, and sequentially recording imaging data of a camera detector until a set final wavelength value is reached;
determining RGB values of the picture in different wave bands, and calculating a spectral response curve of the camera according to tristimulus values at different wavelengths and a spectral curve of the light source.
3. The method for color correction based on spectral response under ultra-low illumination of claim 1, wherein the integral of the daily spectrum and the spectral response curve is calculated, and the specific formula of the integral of the night spectrum and the spectral response curve is as follows:
er＝∫Pr(λ)Sr(λ)dλ
eg＝∫Pg(λ)Sg(λ)dλ
eb＝∫Pb(λ)Sb(λ)dλ
in the formula, Sr(λ)、Sg(λ)、Sb(λ) respectively represents the spectral sensitivity response characteristics, P, of the RGB three channels of the camerar(λ)、Pg(λ)、Pb(λ) is the RGB three-channel power spectrum distribution of daylight/night-day light.
4. The method of claim 1, wherein the correction value for the RGB three channel values is calculated by the formula:
R′＝R*(edr/enr)
G′＝G*(edg/eng)
B′＝B*(edb/enb)
c＝R′+G′+B′
in the formula, edr、edg、edbAs a result of integration of the daytime spectrum with the spectral response curve of the camera, enr、eng、enbR, G, B is the integration result of the night spectrum and the camera spectrum response curve, and R ', G ' and B ' are the corrected RGB three-channel pixel values.
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Citations (4)
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|---|---|---|---|---|
| CN107170013A (en) * | 2017-05-03 | 2017-09-15 | 北京理工大学 | A kind of scaling method of RGB camera spectral response curve |
| CN107197225A (en) * | 2017-06-13 | 2017-09-22 | 浙江大学 | Color digital camera white balance correcting based on chromatic adaptation model |
| CN108051376A (en) * | 2017-12-12 | 2018-05-18 | 中国地质大学（武汉） | A kind of spectrum reconstruction method based on RGB color camera image |
| CN111047539A (en) * | 2019-12-27 | 2020-04-21 | 上海工程技术大学 | Fabric image color calibration algorithm based on spectral reflectivity reconstruction |
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2020
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Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107170013A (en) * | 2017-05-03 | 2017-09-15 | 北京理工大学 | A kind of scaling method of RGB camera spectral response curve |
| CN107197225A (en) * | 2017-06-13 | 2017-09-22 | 浙江大学 | Color digital camera white balance correcting based on chromatic adaptation model |
| CN108051376A (en) * | 2017-12-12 | 2018-05-18 | 中国地质大学（武汉） | A kind of spectrum reconstruction method based on RGB color camera image |
| CN111047539A (en) * | 2019-12-27 | 2020-04-21 | 上海工程技术大学 | Fabric image color calibration algorithm based on spectral reflectivity reconstruction |
Non-Patent Citations (1)
| Title |
|---|
| 项金蓉等: "基于光谱可调积分球光源的多光谱相机颜色校正研究", 《激光与光电子学进展》 * |
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Inventor after: Zhang Junju Inventor after: Chen Jiahui Inventor after: Chen Ruoxi Inventor after: Zhang Yuyang Inventor after: Zhang Xuhui Inventor after: Huang Wei Inventor after: Song Yuxin Inventor before: Chen Jiahui Inventor before: Chen Ruoxi Inventor before: Zhang Yuyang Inventor before: Zhang Xuhui Inventor before: Huang Wei Inventor before: Song Yuxin Inventor before: Zhang Junju |
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