CN108989697A - For responding the standard source picture construction method of nonuniformity correction in road imaging measurement - Google Patents
For responding the standard source picture construction method of nonuniformity correction in road imaging measurement Download PDFInfo
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- CN108989697A CN108989697A CN201810763282.9A CN201810763282A CN108989697A CN 108989697 A CN108989697 A CN 108989697A CN 201810763282 A CN201810763282 A CN 201810763282A CN 108989697 A CN108989697 A CN 108989697A
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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
- H04N23/70—Circuitry for compensating brightness variation in the scene
- H04N23/73—Circuitry for compensating brightness variation in the scene by influencing the exposure time
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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
- H04N23/70—Circuitry for compensating brightness variation in the scene
- H04N23/76—Circuitry for compensating brightness variation in the scene by influencing the image signals
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Abstract
The invention discloses in a kind of road imaging measurement for responding the standard source picture construction method of nonuniformity correction, comprising steps of 1, camera placed into standard source images position to be built, time for exposure and the F-number of camera are set under a response range；2, a photograph frame is shot；3, with random translation and horizontal rotation camera lens, n photograph frame is acquired；4, the photo that step 2 and 3 are shot is synthesized into mean value image5, step 3, step 4 are repeated, when σ changes less than 0.1%, stops repeating, synthetic standards source images；6, other response ranges, the i.e. time for exposure of change camera and F-number are selected, step 1 is repeated and arrives step 5, construct the standard source images under other response ranges.The standard source picture construction method that the method for the present invention obtains is simple, cheap using equipment, and preferable with the commensurate in scope of road scene response, the practicability of the standard source images of building is preferable.
Description
Technical field
The present invention relates to standard source picture construction methods, more specifically to non-for responding in road imaging measurement
The standard source picture construction method of uniformity correction.
Background technique
The reflection of pavement of road be diffusing reflection, mirror-reflection, scattered reflection, mix reflection etc. it is coefficient as a result, but with
Based on diffusing reflection.Road imaging system responds nonuniformity correction usually application point correction method, and this method uses homogeneous radiation source, real
Existing homogeneous radiation or the characteristic (Lambertian reflection) of transmitting.Standard source figure is known as to the resulting image of standard source based on imaging system
Picture.
On the one hand the prior art needs complicated radiation source real to obtain uniform radiation standard source or reflectance standard source
Facility is tested, building process is relatively complicated, on the other hand carries out the precision of system response nonuniformity correction with road scene using it
Lower, application range is relatively narrow.In order to make up the defect of the prior art, standard source figure is constructed using the standard source of nonuniformity correction
Picture can be completed in such a way that random multiframe shoots roadway scene, only need to shoot less frame number, can reach multiple repairing weld
Scene corresponds to the consistent building requirement of radiance summation, and measuring device is simple, easy to implement the method.In addition, using pavement of road into
The quasi- source images of rower construct, and in the response section that can make the standard source images of building, match with the response range of road scene
Preferably.
Summary of the invention
Method that simple and direct, practicability preferably constructs standard source images that it is an object of the invention to preparation methods, is applied to
Road imaging measurement.
In order to achieve the above object, the present invention provides a kind of for responding the standard source picture construction side of nonuniformity correction
Method.
In the consistent situation of illumination condition, technical solution of the present invention includes the following steps:
Step 1: camera being placed into standard source images position to be built, when setting the exposure of camera under a response range
Between and F-number；
Step 2: one photograph frame of shooting；
Step 3: with random translation and rotating horizontally camera lens, shoot photo, acquire n photograph frame；
Step 4: the photo that step 2 and 3 are shot is synthesized into mean value image
In formula, fkThe radiance image on the road surface of-expression kth time sampling.
Its relative standard deviation are as follows:
In formula, Rnun- indicate relative standard deviation；
σ-expression synthesizes mean value imageThe standard deviation of gray average；
μ-expression synthesizes mean value imageGray average.
Wherein ask the formula such as (4) of standard deviation shown
In formula: fij- indicate composographGray value；
μ-expression composographAverage gray；
I, j-expression imageRanks number；
M, N-expression imageRanks number；
Step 5: repeating step 3, step 4, when σ changes less than 0.1%, stop repeating, shoot n altogether at this time0Photograph frame；
Synthetic standards source images, formula is such as shown in (5):
Wherein,- indicate the standard source images synthesized；
- indicate the pavement image that the 1st time imaging obtains；
- indicate the pavement image that kth time imaging obtains；
n0- indicate to acquire the totalframes of image；
Step 6: other respective ranges, the i.e. time for exposure of change camera and F-number are selected, step 1 is repeated and arrives step 5,
Construct the standard source images under other response ranges.
Wherein, for the photo with the storage of RAW format, position to be built is road.For roadway scene random shooting
Multiple image can reach more by shooting less frame number since the statistical property difference that roadway scene is reflected and radiated is smaller
The consistent building requirement of the corresponding radiance summation of the scene of secondary sampling.Method application pavement of road is constructed, so that structure
The corresponding response section of the standard source images built is placed exactly in road radiancy and the dynamic range of photometric measurement.
The present invention has the advantage that
(1) standard source picture construction can be realized in random multiframe shooting pavement of road scene, only need to shoot less frame number i.e.
It can be achieved, avoid using homogeneous radiation source Experimental Establishment costly, image pickup method is simple and easy；
(2) the standard source images constructed are placed exactly in the response section of road survey scene, preferable with the matching of scene,
The practicability of the standard source images of building is preferable.
Detailed description of the invention
Fig. 1 is the standard source images constructed in one embodiment.
Fig. 2 is in Fig. 1 embodiment with the variation of the increase relative standard deviation of building frame number
Fig. 3 is the precision curve graph for constructing standard source images in Fig. 1 embodiment under different frame numbers
Fig. 4 is in Fig. 1 embodiment close to the corresponding integrating sphere image of gray average
Fig. 5 is the gray average of integrating sphere image and the standard path source images established at 1/1000s in Fig. 1 embodiment
With relative standard deviation's relation curve.
Specific embodiment
One, standard source images are constructed
Step 1: in the case where illumination condition is basically unchanged, placing the cameras at any position and distance on bituminous pavement
On high 1.5 meters of the tripod in road surface, time for exposure and the F-number of camera are set, makes the vertical road surface of camera lens.
Step 2: keeping the time for exposure of camera and aperture number state constant, shoot a frame image, be stored as RAW format.
Step 3: keeping the time for exposure of camera and aperture number state constant, with certain step-length (it is recommended that 10cm) mobile three
Foot prop position, and rotating lens at a certain angle, rotating lens then shoots a photograph frame to every tripod positions of change simultaneously,
It is stored as RAW format, acquires n photograph frame；(this step can shoot photo with random translation and horizontal rotation camera lens)
Step 4: all photos of shooting are synthesized into mean value image
In formula, fkThe radiance image on the road surface of-expression kth time sampling.
Its relative standard deviation are as follows:
In formula, Rnun- indicate relative standard deviation；
σ-expression synthesizes mean value imageThe standard deviation of gray average；
μ-expression synthesizes mean value imageGray average.
Wherein ask the formula such as (4) of standard deviation shown
In formula: fij- indicate composographGray value；
μ-expression composographAverage gray；
I, j-expression composographRanks number；
M, N-expression composographRanks number.
Step 5: repeating step 3, step 4, when σ changes less than 0.1%, stop the process of superposed average, clap altogether at this time
Take the photograph n0Frame.It at this time can synthetic standards source images.Composite formula is such as shown in (5):
Wherein,- indicate the standard source images synthesized；
- indicate the pavement image that the 1st time imaging obtains；
- indicate the pavement image that kth time imaging obtains；
n0- indicate to acquire the totalframes of image.
Step 6: changing time for exposure and the F-number of setting camera, repeat step 1 to step 5 and rebuild imaging system
Standard source images under other response ranges.
Compared with the mode of existing building standard source images, the present invention has the advantage that (1) is random for roadway scene
Shoot multi-frame images can be reached since the statistical property difference that roadway scene is reflected and radiated is smaller by shooting less frame number
To the consistent building requirement of the corresponding radiance summation of scene of multiple repairing weld.(2) method application pavement of road is constructed,
So that the corresponding response section of standard source images of building is placed exactly in road radiancy and the dynamic range of photometric measurement, with
The commensurate in scope of road scene response is preferable, carries out system using it and responds nonuniformity correction precision with higher.
Two, the precision and evaluation of standard source images are constructed
1, the standard source images constructed
Using method above, use its pixel size of the camera of Canon's EOS600 model for 4.3 μm of 4.3 μ m, total pixel
Number is 5184 × 3456, and storage format is RAW format, time of integration t=1/1000s；F number chooses f/8, works as n0It is closed when=20 frame
At standard source images it is as shown in Figure 1.
2, the evaluation of the standard source precision of images is constructed
(1) precision evaluation based on statistical property difference frame number synthetic standards source images
With synthesis frame number n0Increase, the synthesis precision of the standard source images of building is gradually increased.Construct standard source figure
The relative standard deviation of picture can characterize the Photo-Response Non-Uniformity with imaging system of the standard source images of building.When this index
When no longer changing, illustrate that the corresponding average radiation brightness value of each sampled point is equal, corresponding standard source images can at this time
Using as evaluation criteria.That is, working as frame number n0When increasing to certain amount, the relative standard deviation for constructing image no longer declines, explanation
The Photo-Response Non-Uniformity of system is had reached.The difference of the image and the image that construct under different frame numbers can express structure under the frame number
Build the precision of standard source images.The precision is characterized with absolute error are as follows:
In formula, E (n)-indicates the precision that standard source images are constructed under n frame；
- indicate the uniformity that standard source images are constructed under n frame；
- indicate in n0The uniformity of standard source images is constructed when frame；
Under camera imposes a condition above, building frame number and the relative standard deviation's curve such as Fig. 2 institute for constructing standard source images
Show.It can be seen that when n=20 frame, Rnun=5.233%；After 20 frames, relative standard deviation's variation is more slow, when reaching
When 80 frame, relative standard deviation is basically unchanged, value Rnun=3.844%.Structure under the different frame numbers of Fig. 3 application formula (6) assessment
Build the precision of standard source images.As it can be seen that the standard source precision of images constructed in 10 frame is 4%；The standard source constructed when 20 frame
The precision of images is 1%.
(2) the standard source images constructed by integrating sphere picture appraisal
Since integrating sphere inner wall is uniform ideal diffusing layer, Lambert law is obeyed, therefore acquires what three color of Zhejiang University was produced
SL300 model, 1 meter of diameter of integrating sphere inner wall image is as standard non-uniform reflection source images, for evaluating the road road sign of building
The uniformity of quasi- source images.It is keeping camera status above constant, is shooting integrating sphere inner wall under each time of integration
Image, the integrating sphere image obtained when the time of integration is 1/8s are as shown in Figure 4.The different times of integration are imaged on to integrating sphere
Under, the gray average of imaging system output and the relation curve of relative standard deviation are as shown in Figure 5.It will be 1/ in the time of integration
The standard source images constructed under 1000s are compared with integrating sphere image, the mistake of the two relative standard deviation under identical gray average
Difference is 1.4%.Illustrate that the standard source images constructed are compared to homogeneity error with integrating sphere standard non-uniform reflection source images
1.4%.
As it can be seen that the precision of construction method homogeneity error compared with integrating sphere image is 1.4%.It can be used for lacking uniformly
In the case of radiation source, the building of standard source images can remove the Photo-Response Non-Uniformity of imaging system based on building image.
The present invention is based on this characteristics of road reflection can be constructed based on Monte Carlo arbitrary sampling method for being imaged
The standard source images of system Photo-Response Non-Uniformity correction.It is logical using planar array detector in order to eliminate the difference of road reflection brightness
The multiple random sampling of multi-point sampling is crossed, road area reflection is extracted, when planar array detector multiple repairing weld number n reaches certain amount
When, the corresponding radiance summation of the scene of multiple repairing weld is consistent.Then, the corresponding average radiation brightness value phase of each sampled point
Deng as shown in formula (1).
In formula,- indicate the corresponding average radiation brightness of each sampled point；
The radiance on the road surface that-expression samples for the first time；
The radiance on the road surface of-expression kth time sampling
N-expression sampling number.
Repeatedly pavement of road is imaged using planar array detector, obtains multiple image, mean value synthesis is carried out to image
Obtain the standard picture with non-uniform reflection characteristic scene.
The foregoing is only a preferred embodiment of the present invention, but scope of protection of the present invention is not limited thereto,
Anyone skilled in the art within the technical scope of the present disclosure, according to the technique and scheme of the present invention and its
Inventive concept is subject to equivalent substitution or change, should be covered by the protection scope of the present invention.
Claims (2)
1. for responding the standard source picture construction method of nonuniformity correction in a kind of road imaging measurement, which is characterized in that
In the consistent situation of illumination condition, include the following steps:
Step 1: by camera place standard source images position to be built, under a response range set camera time for exposure and
F-number；
Step 2: one photograph frame of shooting；
Step 3: with random translation and rotating horizontally camera lens, shoot photo, acquire n photograph frame；
Step 4: the photo that step 2 and 3 are shot is synthesized into mean value image
In formula, fkThe radiance image on the road surface of-expression kth time sampling.
Its relative standard deviation are as follows:
In formula, Rnun- indicate relative standard deviation；
σ-expression synthesizes mean value imageThe standard deviation of gray average；
μ-expression synthesizes mean value imageGray average.
Wherein ask the formula such as (4) of standard deviation shown
In formula: fij- indicate composographGray value；
μ-expression composographAverage gray；
I, j-expression imageRanks number；
M, N-expression imageRanks number；
Step 5: repeating step 3, step 4, when σ changes less than 0.1%, stop repeating, shoot n altogether at this time0Photograph frame；Synthesis
Standard source images, formula is such as shown in (5):
Wherein,- indicate the standard source images synthesized；
- indicate the pavement image that the 1st time imaging obtains；
- indicate the pavement image that kth time imaging obtains；
n0- indicate to acquire the totalframes of image；
Step 6: selecting other respective ranges, the i.e. time for exposure of change camera and F-number, repeat step 1 and arrive step 5, building
Standard source images under other response ranges.
2. according to claim 1 for responding the standard source picture construction method of nonuniformity correction in road imaging measurement,
It is characterized in that, the photo is with the storage of RAW format.
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