CN102608074A - Novel bidirectional reflectance distribution function measuring device - Google Patents

Abstract

The invention discloses a novel bidirectional reflectance distribution function measuring device. A light source 1 is fixed and illuminates perpendicularly and downwards, a sample supporting component is a six-axis manipulator, a probe rotation driving unit 5 drives a detector probe 2 to rotate semi-circularly in a vertical plane above a horizontal plane, the six-axis manipulator 3 is combined with a perpendicular rotating device, a sample 4 and a detector move in a combination manner, the pointing direction and the azimuth angle of a normal line of the illuminated sample and the pointing direction of the detector probe are changed, and incident light and a detection direction in a hemisphere space are accurately positioned relative to the center azimuth angle and the pitch angle of the sample.

Description

A kind of novel bidirectional reflectance distribution function measurement mechanism

Technical field

The invention belongs to a kind of novel bidirectional reflectance distribution function (BRDF) measurement mechanism of optical field; Specifically be through six axis robot and vertical rotational motion mechanism; In conjunction with vertical or the incident of horizontal fixed light source, realize the device that object bidirectional reflectance distribution function is measured in the hemisphere spatial dimension.

Background technology

The bidirectional reflectance distribution function (BRDF) of object is the spectral reflectivity acquisition through different incident directions in the hemisphere of space and detection direction Measuring Object; The object spectra reflectivity has characterized the build-in attribute of object; Through measurement to the object spectra reflectivity; Can extract the many useful informations of object, therefore, all have a wide range of applications in fields such as industrial commerce and trade, remote sensing remote measurement, scientific research, national defense and military.

It is in the hemisphere space of 2 π that the reflection that is radiated at the light beam of body surface is distributed in the plane top solid angle vertical with its normal; Therefore will know the reflection characteristic of body surface, we need measure the reflected by objects situation in 2 π spaces of body surface reflection.

Like Fig. 1 bidirectional reflectance distribution function (BRDF) measuring principle figure, the seventies in last century the U.S. the physical quantity that is used for describing the body surface scattering properties---the bi-directional distributed function (BRDF) that proposes of professor Nicodemus.It is defined as: body surface is at a certain direction (φ _r, θ _r) the interior reflection spoke brightness dL of little solid angle _r(unit: Wm ^-2Sr ^-1Nm ^-1) and incident direction (φ _i, θ _i) the illumination dE of little solid angle _i(unit: Wm ^-2Nm ^-1) ratio, as shown in Figure 1.Can be expressed as like formula (1)

$f_r({\mathrm{\θ}}_i,{\mathrm{\φ}}_i;{\mathrm{\θ}}_r,{\mathrm{\φ}}_r;\mathrm{\λ})=\frac{{\mathrm{dL}}_r({\mathrm{\θ}}_i,{\mathrm{\φ}}_i;{\mathrm{\θ}}_r,{\mathrm{\φ}}_r;\mathrm{\λ})}{{\mathrm{dE}}_i({\mathrm{\θ}}_i,{\mathrm{\φ}}_i;\mathrm{\λ})}---\left(1\right)$

Wherein, dE _i(θ _i, φ _iλ) for being incident on the irradiance on the object, dL _r(θ _i, φ _iθ _r, φ; E _iλ) be the spoke brightness of reflection object, λ is a monochromatic wavelength.

Measuring principle according to BRDF can be known, accomplishes the BRDF measurement to sample if we will set up a covering device, and light source and detector all must move to any specified point on certain hemisphere face of certain radius above the reflecting surface so.Can find out that from the definition of BRDF in theory, light source and detector are a bit, the illumination solid angle is infinitesimal, dL with the detection solid angle _rAnd dE _iBe dimensionless.Therefore, in order to make BRDF proving installation data measured near theoretical value, must make the illumination solid angle as far as possible little with the detection solid angle, promptly be that measurement hemisphere face radius should be tried one's best greatly.

Employing (is defined as and specifies under the lighting condition reflected radiation luminous flux and the ratio of desirable lambert's body at the reflection flux of this direction the measurement of bi-directional reflection factor (BRF).When detector receives solid angle and trends towards zero, BRF=π BRDF) obtains the BRDF optical characteristics of material surface through calculating.

Present existing BRDF measurement mechanism is the change that level and vertically two arc orbits are realized interior directional bearing of hemisphere and zenith angle; The limitation of equipment is embodied in the arc orbit shading to be influenced its measurement result and receives the arc orbit machining precision to influence the bearing accuracy of design factors not high, and then causes the measuring system uncertainty of measurement higher.Therefore existing measuring method and means can not satisfy the demand that current body surface scattering properties is measured, and need a kind of novel measurement mechanism of further exploitation to satisfy existing measurement demand and improve China's optics diffusing characteristic diffuser measurement level simultaneously.

A kind of novel bidirectional reflectance distribution function device is mainly realizes that BRDF measures and designs in the hemisphere space; The device that first Application and BRDF measure mainly comprises two parts; One of which is for supporting sample and realize six axis robot that fixed point three dimensions rotates, and it two realizes in the vertical plane for driving the detector fibres probe ± the band probe rotary unit of 180 ° of rotations.

Summary of the invention

The technical matters that the present invention will solve provides a kind of novel bidirectional reflectance distribution function device; Especially realize sample upper surface central space invariant position; The normal of vertical centre carries out the accurate angular transformation of position angle and zenith angle with respect to central point, thereby realizes being equivalent to sample incident ray position angle in hemisphere and zenith angle variation when motionless.

For solving the problems of the technologies described above technical scheme of the present invention:

A kind of novel bidirectional reflectance distribution function measurement mechanism; Comprise a fixed light source, detector and sample support parts, realize that bidirectional reflectance distribution function (BRDF) is measured in the hemisphere space, said fixed light source throws light on downwards; The light source below is provided with six axis robot; The sample support parts are installed on six axis robot, clamping test sample on the sample support parts, and six axis robot, one side is provided with the probe rotary unit of in vertical plane, doing ± 180 ° of rotations; The probe rotary unit is provided with detector, and detector points to the sample center; Operate six axis robot, through changing the mode of sensing of illuminated sample normal and position angle and rotation probe rotary unit, and keep the centre coordinate of sample constant, carry out the bidirectional reflectance distribution function and measure.

Rotary unit includes the bearing that is arranged at six axis robot, one side, is rotatablely equipped with a L shaped bar on the bearing, and the detection that probe orientation is vertically pointed to the sample center is installed on the cross bar of L shaped bar

The incident illumination of package unit and detector and sample position relation are as shown in Figure 2.Light source is illumination vertically downward, and the angle of detector and light source axis is δ,

$\mathrm{\α}=\arctan \left(\frac{\cos {\mathrm{\θ}}_r-\cos {\mathrm{\θ}}_i\cos \mathrm{\δ}}{\cos {\mathrm{\θ}}_i\sin \mathrm{\δ}}\right)---\left(2\right)$

$\mathrm{\β}=\arcsin \left(\frac{-\sin ({\mathrm{\φ}}_r-{\mathrm{\φ}}_i)\sin {\mathrm{\θ}}_r\sin {\mathrm{\θ}}_i}{\sin \mathrm{\δ}}\right)---\left(3\right)$

$\mathrm{\γ}=\arctan \left(\frac{\sin {\mathrm{\θ}}_i\sin {\mathrm{\φ}}_i\cos {\mathrm{\θ}}_r-\sin {\mathrm{\θ}}_r\sin {\mathrm{\φ}}_r\cos {\mathrm{\θ}}_i}{\sin {\mathrm{\θ}}_r\cos {\mathrm{\φ}}_r\cos {\mathrm{\θ}}_i-\sin {\mathrm{\θ}}_i\cos {\mathrm{\φ}}_i\cos {\mathrm{\θ}}_r}\right)---\left(4\right)$

δ＝arccos(cosθ _icosθ _r+sinθ _isinθ _rcos(φ _r-φ _i)) (5)

δ is the angle of detector probe sensing and lighting source incident direction in the formula.

Six axis robot of clamped sample and the probe rotary unit of clamping detecting head; Sample central point rectilinear motion degree of freedom in space coordinates (x, y, z, α, β, γ) is defined realizes the change of three-dimensional rotational freedom, and then realize that incident ray and detection direction are with respect to the accurate location of the sample central party parallactic angle and the angle of pitch in the hemisphere space.

Six axis robot realize that through the axle rotating unit rectilinear motion of its working sections X/Y/Z direction in the certain limit of space and roll α, driftage β, pitching γ attitude change, and need to keep working sections center XYZ constant.

This BRDF measurement mechanism adopts the downward lighting source of fixed vertical; The mode of motion that combines with sample and detector designs; On all directions, survey the reflected signal of various angle incident optical signals for realizing detector; With occurring in nature is that the mode that incident direction and detection direction change is designed to realize that through the mode that changes the sensing of sensing of illuminated sample normal and position angle and change detection probe the incident illumination of package unit and detector and sample position relation are as shown in Figure 2 originally.

Advantage of the present invention is:

Existing BRDF measurement mechanism is the change that level and vertically two arc orbits are realized interior directional bearing of hemisphere and zenith angle; The limitation of equipment is embodied in the arc orbit shading to be influenced its measurement result and receives the arc orbit machining precision to influence the bearing accuracy of design factors not high, and then causes the measuring system uncertainty of measurement higher.

Six axis robot axle rotating units realize that the rectilinear motion of its working sections X/Y/Z direction in the certain limit of space and roll α, driftage β, pitching γ attitude change, and promptly the working sections central point has six-freedom degree (X, Y; Z, α, β; γ); Measure for BRDF, need to keep working sections center XYZ constant, write BRDF and measure control program; Automatically calculate the surveying work path through controller, realize the angle change of working sections central authorities normal angle, hemisphere interior orientation and zenith angle in the space.Cooperate vertical rotating operation mechanism to satisfy the BRDF conversion demand that takes measurement of an angle; Can realize sample upper surface central space invariant position; The normal of vertical centre carries out the accurate angular transformation of position angle and zenith angle with respect to central point, thereby realizes being equivalent to sample incident ray position angle in hemisphere and zenith angle variation when motionless.

Description of drawings

Do further detailed explanation below in conjunction with the accompanying drawing specific embodiments of the invention.

Fig. 1 is bidirectional reflectance distribution function of the present invention (BRDF) test philosophy figure.

Fig. 2 concerns synoptic diagram for illumination and detector and sample position.

Fig. 3 is six axis robot.

Fig. 4 is the novel bidirectional reflectance distribution function of the present invention (BRDF) measurement mechanism synoptic diagram.

Embodiment

This novel bidirectional reflectance distribution function (BRDF) measurement mechanism comprises a fixed light source 1, detector 2 and sample support parts; Realize that bidirectional reflectance distribution function (BRDF) is measured in the hemisphere space, it is characterized in that said fixed light source throws light on downwards; The light source below is provided with six axis robot 3; The sample support parts are installed on six axis robot, and clamping test sample 4, six axis robot one side is provided with the probe rotary unit 5 of in vertical plane, doing ± 180 ° of rotations on the sample support parts; The probe rotary unit is provided with detector, and detector points to the sample center; Operate six axis robot; Through changing the mode of sensing of illuminated sample normal and position angle and rotation probe rotary unit; Six axis robot realize that through the axle rotating unit rectilinear motion of its working sections X/Y/Z direction in the certain limit of space and roll α, driftage β, pitching γ attitude change; Need to keep working sections center XYZ constant, constant with the centre coordinate that keeps sample, carry out the bidirectional reflectance distribution function and measure.Probe rotary unit 5 includes the bearing that is arranged at six axis robot, one side, is rotatablely equipped with a L shaped bar on the bearing, and the detector 2 that probe orientation is vertically pointed to the sample center is installed on the cross bar of L shaped bar.

Claims (2)

1. a novel bidirectional reflectance distribution function measurement mechanism comprises a fixed light source, detector and sample support parts, realizes that bidirectional reflectance distribution function (BRDF) is measured in the hemisphere space; It is characterized in that; Said fixed light source throws light on downwards, and the light source below is provided with six axis robot, and the sample support parts are installed on six axis robot; Clamping test sample on the sample support parts; Six axis robot, one side is provided with the probe rotary unit of in vertical plane, doing ± 180 ° of rotations, and the probe rotary unit is provided with detector, and detector points to the sample center; Operate six axis robot, through changing the mode of sensing of illuminated sample normal and position angle and rotation probe rotary unit, and keep the centre coordinate of sample constant, carry out the bidirectional reflectance distribution function and measure.

2. novel bidirectional reflectance distribution function measurement mechanism according to claim 1; The rotary unit that it is characterized in that popping one's head in includes the bearing that is arranged at six axis robot, one side; Be rotatablely equipped with a L shaped bar on the bearing, the detector that probe orientation is vertically pointed to the sample center is installed on the cross bar of L shaped bar.

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