CN102253594B - Platform for testing performance of camera based on EMVA1288 standard - Google Patents

Abstract

The invention relates to a platform for testing performance of a camera based on an EMVA1288 standard. The method is used for testing the performance of the camera to be tested. The platform comprises an integrating sphere, a camera obscure, an optical power meter arranged in the camera obscure, a computer control system and a bracket, wherein a light inlet hole is formed in the camera obscure; the light inlet hole is matched with a light outlet hole of the integrating sphere; a double-dick filtering component and the camera to be tested are sequentially arranged in the camera obscure along an optical shaft direction of the light outlet hole of the integrating sphere; the double-dick filtering component comprises an optical filter and an attenuation sheet; the optical power meter is positioned between the double-dick filtering component and the camera to be tested and is far away from the optical shaft; the optical filter, the attenuation sheet, the optical power meter and the camera to be tested are arranged on the bracket and are connected with the computer control system; the computer control system calculates and processes attenuation values of light intensity and brightness, and the light power data monitored in real time so as to obtain the performance parameters of the camera to be tested specified in the EMVA1288 standard. The testing platform can test all the parameters specified in the EMVA1288 standard, and is simple in structure and low in cost.

Description

Camera properties test platform based on the EMVA1288 standard

Technical field

The present invention relates to a kind of camera properties technical field of measurement and test, particularly a kind of camera properties test platform based on the EMVA1288 standard.

Background technology

EMVA1288 is No. 1288 standardized product catalogue listings that EMVA (EMVA) announces, and is a cover standard of demarcating for the imageing sensor of machine vision applications and camera characteristics and performance data.

Before EMVA1288 occurred, imageing sensor and camera properties test never had unified standard.If large manufacturer KODAK, DALSA, SONY respectively have the cover assessment testing standard of oneself, the index definition that has is identical, also has a lot of index definitions different simultaneously, therefore is difficult to imageing sensor and the camera of different vendor are carried out horizontal performance comparison.In order to carry out horizontal performance comparison in the different stages to imageing sensor and the camera of different manufacturers, be necessary to develop standard set testing apparatus and flow process, and form unified and standard test report, its index definition and method of testing also need unified and standard, and EMVA has announced the EMVA1288 standard for this reason.The advantage of EMVA1288 is that it is a whole set of imageing sensor and the digital camera evaluating standard of setting up on strict physical simulation and mathematical model basis, detailed clear and definite regulation has all been done in its output to testing apparatus, method of testing, index definition and test report, and having obtained more and more important imageing sensors and approval and the support of camera manufacturer, is the generally acknowledged testing standard of a present unique machine vision class sensor and camera.The characteristics of this standard are the mathematical models of having set up the CCD area array cameras, and set up method of testing take mathematical model as instructing, and therefore test is more rigorous.

Along with the appearance of EMVA1288, the well-known camera in many worlds manufacturer all begins progressively to carry out the method for testing with unified standard that this cover is generally acknowledged.U.S. SARNOFF company in 2009 has has researched and developed a cover camera properties test macro by the EMVA1288 standard and has come public offering as product, become in the world first hand sale and satisfy the business men of the product of EMVA1288 test macro, it can test whole parameters of EMVA1288 standard code.Test macro mainly is comprised of six integrating spheres, darkroom, computing machine and software systems, and six integrating spheres are arranged in the camera bellows as light source, and the method for overlapping each integrating sphere of employing is regulated the brightness of light source, takes to carry out the camera properties test by camera again.This test macro causes the camera bellows volume bigger than normal owing to be provided with a plurality of integrating spheres in the darkroom, and the camera bellows inner structure is complicated, and whole camera properties testing cost is also higher.

Summary of the invention

The present invention is directed to based on the camera properties test platform of EMVA1288 standard rare, and the problem of existing test system structure complexity, a kind of novel camera properties test platform based on the EMVA1288 standard is provided, this test platform can be tested whole parameters of EMVA1288 standard code, also has advantage simple in structure, with low cost.

Technical scheme of the present invention is as follows:

A kind of camera properties test platform based on the EMVA1288 standard, be used for tested camera is carried out performance test, it is characterized in that, comprise integrating sphere, camera bellows, be arranged at the light power meter in the camera bellows, computer control system and support, be provided with incidence hole on the described camera bellows, the light hole of described incidence hole and integrating sphere is complementary, optical axis direction along the light hole of integrating sphere in the described camera bellows is disposed with double plate filter part and tested camera, described double plate filter part comprises optical filter and the attenuator that arranges along optical axis direction, described light power meter is between double plate filter part and tested camera and avoid the optical axis setting, described optical filter, attenuator, light power meter and tested camera all are arranged on the support and all link to each other with computer control system, and described computer control system obtains the luminous power data computing of the pad value of light intensity and brightness and Real-Time Monitoring the parameter of the tested camera properties of EMVA1288 standard code.

Described optical filter comprise the first disk and on the first disk around the center of circle along the monochromatic filter of the different wave length more than two or two that circumferentially distributes successively, described attenuator comprise the second disk and on the second disk around the center of circle along the neutral filter of the different light intensity attenuation degree more than two or two that circumferentially distributes successively, described optical filter and attenuator under the control of computer control system around the rotation of the center of circle separately, the diameter of described monochromatic filter and neutral filter all greater than the light hole diameter of integrating sphere with the light source by described light hole.

Optical axis direction along the light hole of integrating sphere in the described camera bellows sets gradually optical filter and attenuator, or the optical axis direction along the light hole of integrating sphere sets gradually attenuator and optical filter in the described camera bellows.

Described support comprises the first support wheel, the second support wheel, luminous power support and camera support, the center of the first disk of described optical filter is arranged at the first support wheel, the center of the second disk of described attenuator is arranged at the second support wheel, described light power meter is arranged on the light power meter support, tested camera is arranged on the camera support, described the first support wheel, the second support wheel, light power meter support and camera support are all highly adjustable and all be arranged on the horizontal guide rail, and described integrating sphere is arranged on the adjustable for height integrating sphere support bar.

Described the first support wheel and the second support wheel are two parts of double plate support wheel, and described double plate support wheel height is adjustable and be arranged on the horizontal guide rail.

Also comprise thermometer with contacts, an end of described thermometer with contacts stretches into the inside of camera bellows, and thermometer with contacts links to each other with computer control system.

Monochromatic filter plate in the described filter plate is eight and evenly distributes along circumferential around the center of circle on the first disk; And/or the neutral filter in the described attenuator is eight and evenly distributes along circumferential around the center of circle on the second disk.

The light hole of described integrating sphere sends the uniform source of light that colour temperature is 3200K.

Described computer control system comprises control box, computing machine and the oscillograph that links to each other successively, and described optical filter, attenuator, light power meter and tested camera all link to each other with control box.

Technique effect of the present invention is as follows:

The camera properties test platform that the present invention relates to, meet the EMVA1288 standard, can be used for tested camera (face battle array, linear array CCD camera all can) carry out performance test, comprise integrating sphere, camera bellows, computer control system and support, be provided with incidence hole on the camera bellows, the light hole of described incidence hole and integrating sphere is complementary, the uniform source of light that the integrating sphere light hole sends enters camera bellows through the incidence hole of camera bellows, carry out respectively the decay of the intensity of light source and brightness through the double plate filter part, and carry out the Real-Time Monitoring of luminous power through light power meter in tested camera front, luminous power data transmission to the computer control system of each pad value and monitoring is carried out the parameter that computing finally draws the tested camera properties of EMVA1288 standard code.The present invention has created a kind of camera properties test platform based on the EMVA1288 standard, adopt an integrating sphere and double plate filter part can finish the adjusting of the intensity of light source and brightness, avoided existing test platform that a plurality of integrating spheres are arranged in the camera bellows as light source, bigger than normal and the complex structure of camera bellows volume that the brightness of adopting the method for overlapping each integrating sphere to regulate light source causes, the problem that testing cost is high has advantage simple in structure, with low cost.

Optical filter comprises the first disk and at the monochromatic filter of the different wave length more than two or two that distributes successively around the center of circle on the first disk, attenuator comprises the second disk and at the neutral filter of the different light intensity attenuation degree more than two or two that distributes successively around the center of circle on the second disk, the unique texture of optical filter and attenuator is set, so that filter plate and attenuator under the control of computer control system around the rotation of the center of circle separately, the light source that the integrating sphere light hole sends, can be all by the monochromatic filter of a certain specific wavelength and the neutral filter of a certain light intensity attenuation degree, independent assortment through each monochromatic filter and each neutral filter, obtain light source in the attenuation change effect of varying strength and different brightness degrees, directly control filter plate and attenuator rotation, need not to change separately optical filter and attenuator, use very convenient.

Description of drawings

Fig. 1 is the perspective view that the present invention is based on the camera properties test platform of EMVA1288 standard.

Fig. 2 is the plan structure synoptic diagram of camera properties test platform shown in Figure 1.

Fig. 3 is the forward sight structural representation of camera properties test platform shown in Figure 1.

Fig. 4 is optical filter preferred structure synoptic diagram.

Fig. 5 is attenuator preferred structure synoptic diagram.

Each label lists as follows among the figure:

The 1-integrating sphere; The 2-light hole; The 3-optical filter; The 4-attenuator; The 5-light power meter; The 6-CCD area array cameras; The 7-camera support; 8-light power meter support; 9-double plate support wheel; 10-integrating sphere support bar; The 11-camera bellows; 12-the first disk; The 13-monochromatic filter; 14-the second disk; The 15-neutral filter.

Embodiment

The present invention will be described below in conjunction with accompanying drawing.

The invention discloses a kind of camera properties test platform based on the EMVA1288 standard, be used for tested camera (CCD area array cameras 6) is carried out performance test, Fig. 1, Fig. 2 and Fig. 3 be respectively this test platform solid, overlook and the forward sight structural representation.This test platform meets the EMVA1288 standard, this test platform comprises integrating sphere 1, camera bellows 11 and computer control system (Fig. 1 does not draw), integrating sphere 1 comprises light hole 2, be provided with incidence hole on the camera bellows 11, incidence hole and light hole 2 are complementary, present embodiment integrating sphere 1 is arranged at the outside of camera bellows 11, also integrating sphere 1 can be arranged at the inside of camera bellows 11, the optical axis direction of the interior light hole 2 along integrating sphere 1 of camera bellows 11 is disposed with optical filter 3, attenuator 4 and tested CCD area array cameras 6, light power meter 5 between attenuator 4 and CCD area array cameras 6 and its highly be lower than optical axis (this set-up mode is in order to avoid optical axis, thereby does not affect the imaging of CCD area array cameras 6).Integrating sphere 1 is arranged on the adjustable for height integrating sphere support bar 10, optical filter 3 and attenuator 4 all are arranged on the double plate support wheel 9, the lower end of described double plate support wheel 9 is adjustable for height support, the upper end is symmetrically set with bearing, be respectively applied to install filter plate 3 and attenuator 4, the center that namely connects respectively the second disk 14 of the center of the first disk 12 of optical filter 3 and attenuator 4 by bearing, light power meter 5 is arranged on the light power meter support 8, tested CCD area array cameras 6 is arranged on the camera support 7, double plate support wheel 9, light power meter support 8 and camera support 7 are all highly adjustable, and are arranged on the horizontal guide rail with the distance of the uniform source of light distance of carrying out sending with integrating sphere 1 and regulate.

Optical filter 3 and attenuator 4 belong to the double plate filter part, the preferred structure synoptic diagram of optical filter 3 as shown in Figure 4, comprise the first disk 12 and on the first disk 12 around the center of circle along the circumferential monochromatic filter 13 of equally distributed eight different wave lengths, indicate shown in the A-H, as comprise 400,450,500,550,600,650,700 and eight wavelength points such as 750nm, to obtain respectively the monochromatic area sources such as purple light, blue light, green glow.The preferred structure synoptic diagram of attenuator 4 as shown in Figure 5, the neutral filter 15 of eight the different light intensity attenuation degree that comprises the second disk 14 and on the second disk 14, circumferentially distribute successively around edge, the center of circle, indicate shown in the a-h, as comprise that transmitance is eight light intensity attenuation degree such as 0.1,0.2.Carry out the decay of the different intensities of light source by the monochromatic filter 13 in the optical filter 3, carry out the decay of different light-source brightness by the neutral filter 15 in the attenuator 4, optical filter 3 and attenuator 4 are interchangeable in the position of double plate support wheel 9, be that to send colour temperature be that the uniform source of light of 3200K enters in the camera bellows 11 for the light hole 2 of integrating sphere 1, carry out the decay of different light-source brightness by neutral filter 15 first, carry out the decay of the different intensities of light source by monochromatic filter 13 again.Optical filter 3 and attenuator 4 under the effect of control box around the rotation of the center of circle separately (also can directly control double plate support wheel 9 by control box rotates), the diameter of monochromatic filter 13 and neutral filter 15 all greater than light hole 2 diameters of integrating sphere 1 with farthest by described light hole 2 light source out.Optical filter 3 and attenuator 4 can asynchronously rotate, with optical filter 3 and attenuator 4 different rotation angle, so that each monochromatic filter 13 and each neutral filter 15 carry out independent assortment, carry out the decay of a plurality of brightness degrees of monochromatic area source of integrating sphere area source varying strength and different brightness, and the Real-Time Monitoring that carries out luminous power in CCD area array cameras 6 fronts through light power meter 5 is to obtain CCD area array cameras 6 surperficial incident intensities, Surface Contact point type thermometer also can be set, the one end is stretched into the inside of camera bellows 11 with the shell environment temperature of monitoring CCD area array cameras 6, the surperficial incident intensity data of each pad value and monitoring are transferred to computing machine by control box carry out computing, computing machine finally draws the parameter of the tested camera properties of EMVA1288 standard code by VC or VB or assembly language under the Windows system, such as signal to noise ratio (S/N ratio), quantum effect, response sensitivity, mean value, inequality etc., and with the correlated performance parameter display to oscillograph.

After the basic status of tested camera is fixing, under the different time shutter, gather the image of details in a play not acted out on stage, but told through dialogues and two series of light field (to similarity condition, at least gather two width of cloth images, in order to ask variance), in platform setting and image acquisition, note following some: image acquisition use monochromatic source, optical source wavelength and QE responsiveness peak wavelength are no more than 50nm; The DN value is the bigger the better; (for example: if two kinds of settings of 12bit/8bit are arranged, get 12bit and arrange); The platform gain is more low better; Camera biasing is the smaller the better, but the details in a play not acted out on stage, but told through dialogues noise figure that will guarantee all pixels except defect point is all greater than 1DN; The selection of time shutter guarantees to cover SNR=1 and saturated exposure gamut; The time shutter data will guarantee under minimum detectable exposure and saturation exposure same precision is arranged; Close all kinds of automatic control functions such as automatic gain control of camera.

After gathering image series, calculate μ with following formula _yAnd

The value of (calculating with two width of cloth image A, the B under the same conditions of exposure):

${\mathrm{\&mu;}}_y=\frac{1}{N}\underset{i,j}{\mathrm{\&Sigma;}}{y}_{\mathrm{ij}}$ With ${\mathrm{\&sigma;}}_{y.\mathrm{<figure-callout\; id="2"\; label="temp"\; filenames="HDA0000069977870000012.png"\; state="\{\{state\}\}">temp</figure-callout>}}^2=\frac{1}{2}\left[\frac{1}{N}\underset{i,j}{\mathrm{\&Sigma;}}{(y_{\mathrm{ij}}^A-y_{\mathrm{ij}}^B)}^2\right]$

Based on above computing method, obtain following tables of data or figure, to be used for calculating each parameter value:

To darkfield image, statistics is obtained different exposure time T _Expμ under the condition _Y.darkWith

Tables of data (and curve map).

To the light field image, statistics is obtained different exposure time T _Expμ under the condition _p, μ _yWith

Tables of data (and curve map).

The below introduces partial parameters computing formula among the EMVA1288 and basic account form method.

The full gain K of system computing formula:

$K=\frac{{\mathrm{\&sigma;}}_{y.\mathrm{temp}}^2-{\mathrm{\&sigma;}}_{y.\mathrm{temp}.\mathrm{dark}}^2}{{\mathrm{\&mu;}}_y-{\mathrm{\&mu;}}_{y.\mathrm{dark}}}$

To μ _y-μ _Y.darkCurve in, the linearity range of getting wherein comes the calculating K value.

Saturated output μ _E.sat:

To μ _pWhen linear, μ _pMaximal value μ _P.satBe saturation point.The full trap capacity μ of CCD camera _E.satComputing method be

${\mathrm{\&mu;}}_{e.\mathrm{sat}}={\mathrm{\&eta;\&mu;}}_{p.\mathrm{sat}}=\frac{{\mathrm{\&mu;}}_y-{\mathrm{\&mu;}}_{y.\mathrm{dark}}}{K{\mathrm{\&mu;}}_p}{\mathrm{\&mu;}}_{p.\mathrm{sat}}=\frac{{\mathrm{\&mu;}}_{y.\mathrm{sat}}-{\mathrm{\&mu;}}_{y.\mathrm{dark}}}{K}$

According to μ _yTo T _ExpCurve is found out the wherein maximal value of linearity range, calculates the saturated output of CCD μ based on above formula _E.satDark field signal nonuniformity DSNU ₁₂₈₈:

The first step (when known N value, can skip this process): under equal conditions, several (being assumed to N) images of continuous acquisition are averaging multiple image and obtain new image.Calculate the overall noise σ of time domain low-pass filtering image with spectroscopic methodology (Spectrogram Method) _Y.full(N), make N enough greatly to guarantee to satisfy following condition:

${\mathrm{\&sigma;}}_{y.\mathrm{full}}\left(N\right)\&GreaterEqual;(10\&CenterDot;{\stackrel{\&OverBar;}{\mathrm{\&sigma;}}}_N=10\&CenterDot;\sqrt{\frac{{\mathrm{\&sigma;}}_{y.\mathrm{temp}}^2}{N}})$

Second step: after determining the N value, gather the details in a play not acted out on stage, but told through dialogues of a series of time domain low-pass filtering and light field image, calculate the spatial domain noise with following formula:

${\mathrm{\&sigma;}}_{y.\mathrm{<figure-callout\; id="2"\; label="spat"\; filenames="HDA0000069977870000012.png"\; state="\{\{state\}\}">spat</figure-callout>}}^2=\frac{1}{N}\underset{i,j}{\mathrm{\&Sigma;}}{(y_{\mathrm{ij}}-{\mathrm{\&mu;}}_y)}^2$

Get its average, obtain the spatial noise standard deviation divided by K:

${\mathrm{DSNU}}_{1288}={\mathrm{\&sigma;}}_0=\frac{{\mathrm{\&sigma;}}_{y.\mathrm{spat}.\mathrm{dark}}}{K}$

Photo response nonuniformity PRNU ₁₂₈₈(S _g):

With DSNU ₁₂₈₈Method of testing the same, PRNU ₁₂₈₈Calculating based on following formula

${\mathrm{PRNU}}_{1288}=S_g=\frac{\sqrt{{\mathrm{\&sigma;}}_{y.\mathrm{spat}}^2-{\mathrm{\&sigma;}}_{y.\mathrm{spat}.\mathrm{dark}}^2}}{{\mathrm{\&mu;}}_y-{\mathrm{\&mu;}}_{y.\mathrm{dark}}}$

Get

To μ _y-μ _Y.darkSlope obtain PRNU ₁₂₈₈=S _g

Responsiveness R: adopt the 3200K light source+monochromatic filter of integrating sphere output to produce monochromatic area source, use light power meter to measure CCD camera surface incident intensity E, measure different exposure time T _ExpThe hypograph gray average is based on following formula degree of meeting with a response $R=\frac{{\mathrm{\&mu;}}_y}{E\&CenterDot;T_{\exp }}$

The method of testing of the camera properties test platform based on the EMVA1288 standard of the present invention is open, standard is unified, and the testing process standard can be with the area array cameras product of research and development before delivering to customer, by the performance test of dispatching from the factory of this test platform, so that the client laterally reaches vertical contrast.

Should be pointed out that the above embodiment can make the invention of those skilled in the art's comprehend, but do not limit the present invention in any way creation.Therefore; although this instructions has been described in detail the invention with reference to drawings and Examples; but; those skilled in the art are to be understood that; still can make amendment or be equal to replacement the invention; in a word, all do not break away from technical scheme and the improvement thereof of the spirit and scope of the invention, and it all should be encompassed in the middle of the protection domain of the invention patent.

Claims (8)

1. camera properties test platform based on the EMVA1288 standard, be used for tested camera is carried out performance test, it is characterized in that, comprise integrating sphere, camera bellows, be arranged at the light power meter in the camera bellows, computer control system and support, be provided with incidence hole on the described camera bellows, the light hole of described incidence hole and integrating sphere is complementary, optical axis direction along the light hole of integrating sphere in the described camera bellows is disposed with double plate filter part and tested camera, described double plate filter part comprises optical filter and the attenuator that arranges along optical axis direction, described light power meter is between double plate filter part and tested camera and avoid the optical axis setting, described optical filter, attenuator, light power meter and tested camera all are arranged on the support and all link to each other with computer control system, and described computer control system obtains the luminous power data computing of the pad value of light intensity and brightness and Real-Time Monitoring the parameter of the tested camera properties of EMVA1288 standard code; Described optical filter comprise the first disk and on the first disk around the center of circle along the monochromatic filter of the different wave length more than two or two that circumferentially distributes successively, described attenuator comprise the second disk and on the second disk around the center of circle along the neutral filter of the different light intensity attenuation degree more than two or two that circumferentially distributes successively, described optical filter and attenuator under the control of computer control system around the rotation of the center of circle separately, the diameter of described monochromatic filter and neutral filter all greater than the light hole diameter of integrating sphere with the light source by described light hole.

2. camera properties test platform according to claim 1, it is characterized in that, optical axis direction along the light hole of integrating sphere in the described camera bellows sets gradually optical filter and attenuator, or the optical axis direction along the light hole of integrating sphere sets gradually attenuator and optical filter in the described camera bellows.

3. camera properties test platform according to claim 2, it is characterized in that, described support comprises the first support wheel, the second support wheel, luminous power support and camera support, the center of the first disk of described optical filter is arranged at the first support wheel, the center of the second disk of described attenuator is arranged at the second support wheel, described light power meter is arranged on the light power meter support, tested camera is arranged on the camera support, described the first support wheel, the second support wheel, light power meter support and camera support are all highly adjustable and all be arranged on the horizontal guide rail, and described integrating sphere is arranged on the adjustable for height integrating sphere support bar.

4. camera properties test platform according to claim 3 is characterized in that, described the first support wheel and the second support wheel are two parts of double plate support wheel, and described double plate support wheel height is adjustable and be arranged on the horizontal guide rail.

5. according to claim 1 to one of 4 described camera properties test platforms, it is characterized in that also comprise thermometer with contacts, an end of described thermometer with contacts stretches into the inside of camera bellows, thermometer with contacts links to each other with computer control system.

6. camera properties test platform according to claim 1 is characterized in that, the monochromatic filter plate in the described filter plate is eight and evenly distributes along circumferential around the center of circle on the first disk; And/or the neutral filter in the described attenuator is eight and evenly distributes along circumferential around the center of circle on the second disk.

7. camera properties test platform according to claim 1 is characterized in that, the light hole of described integrating sphere sends the uniform source of light that colour temperature is 3200K.

8. camera properties test platform according to claim 1 is characterized in that, described computer control system comprises control box, computing machine and the oscillograph that links to each other successively, and described optical filter, attenuator, light power meter and tested camera all link to each other with control box.

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