CN102608074B - 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 by six axis robot and vertical rotary motion, in conjunction with vertical or horizontal fixed light source incident, realize the device that in hemisphere spatial dimension, object bidirectional reflectance distribution function is measured.

Background technology

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

It is in half spherical 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 to measure the reflection condition of object in 2 π spaces of body surface reflection.

As 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 body surface scattering properties---the bi-directional distributed function (BRDF) that proposes of professor Nicodemus.It is defined as: body surface is at a direction (φ _r, θ _r) reflection spoke brightness dL in 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 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 _i; λ) for being incident on the irradiance on object, dL _r(θ _i, φ _i; θ _r, φ; E _i; Be λ) the spoke brightness of object reflection, λ is monochromatic wavelength.

Known according to the measuring principle of BRDF, if will setting up a covering device, we have come the BRDF of paired samples to measure, light source and detector all must move to any specified point on certain hemisphere face of certain radius above reflecting surface so.From the definition of BRDF, can find out, in theory, light source and detector are a bit, and illumination solid angle and detection solid angle are infinitesimal, dL _rand dE _ibe dimensionless.Therefore,, for the data that BRDF proving installation is measured approach theoretical value, must make to throw light on solid angle and detection solid angle are as far as possible little, are to make to measure hemisphere face radius should try one's best greatly.

Employing (is defined as and specifies under 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) by calculating, obtain the BRDF optical characteristics of material surface.

Current existing BRDF measurement mechanism be level and vertically two arc orbits realize the change of directional bearing and zenith angle within the scope of hemisphere, the limitation of equipment is embodied in arc orbit shading to be affected its measurement result and is subject to arc orbit machining precision to affect the positioning precision of design factors not high, and then causes measuring system uncertainty of measurement higher.Therefore existing measuring method and means can not meet the demand that current body surface scattering properties is measured, and need a kind of novel measurement mechanism of further exploitation to meet 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 to be realized in half spherical space BRDF and measures and design, the device that first Application and BRDF measure mainly comprises two parts, one is for supporting sample and realizing the six axis robot that fixed point three dimensions rotates, and it is two for driving the band probe rotary unit of realize in vertical plane ± 180 ° of rotations of detector fibres probe.

Summary of the invention

The technical problem to be solved in the present invention is to provide 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, thus realize be equivalent to sample when motionless position angle and the zenith angle of incident ray within the scope of hemisphere change.

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, realizing bidirectional reflectance distribution function in half spherical space (BRDF) measures, described fixed light source throws light on downwards, light source below is provided with six axis robot, sample support parts are installed on six axis robot, clamping test sample on sample support parts, six axis robot one side is provided with the probe rotary unit of doing ± 180 ° of rotations in vertical plane, probe rotary unit is provided with detector, and detector points to sample center; Operation six axis robot, by changing the mode of the sensing of illuminated sample normal and position angle and rotation probe rotary unit, and keeps the centre coordinate of sample constant, carries out bidirectional reflectance distribution function measurement.

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

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

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

Rectilinear motion and roll α, driftage β, pitching γ attitude that six axis robot is realized its working sections X/Y/Z direction in the certain limit of space by axle rotating unit 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 combining with sample and detector designs, for realizing detector, in all directions, survey the reflected signal of various angle incident optical signals, by occurring in nature, be that the mode that incident direction and detection direction change is designed to realize by changing the mode of the sensing of illuminated sample normal and position angle and the sensing of change detection probe originally, the incident illumination of package unit and detector and sample position relation are as shown in Figure 2.

Advantage of the present invention is:

Existing BRDF measurement mechanism be level and vertically two arc orbits realize the change of directional bearing and zenith angle within the scope of hemisphere, the limitation of equipment is embodied in arc orbit shading to be affected its measurement result and is subject to arc orbit machining precision to affect the positioning precision of design factors not high, and then causes measuring system uncertainty of measurement higher.

Rectilinear motion and roll α, driftage β, pitching γ attitude that six axis robot axle rotating unit is realized its working sections X/Y/Z direction in the certain limit of space change, be that working sections central point has six-freedom degree (X, Y, Z, α, β, γ), for BRDF, measure, need to keep working sections center XYZ constant, write BRDF and measure control program, by controller, automatically calculate surveying work path, realize working sections central authorities normal at the Angulation changes of angle, hemisphere scope interior orientation, space and zenith angle.Coordinate vertical rotary travelling mechanism to meet 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, thus realize be equivalent to sample when motionless position angle and the zenith angle of incident ray within the scope of hemisphere change.

Accompanying drawing explanation

Below in conjunction with accompanying drawing, specific embodiments of the present invention are further described in detail.

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

Fig. 2 is that illumination and detector and sample position are related to schematic diagram.

Fig. 3 is six axis robot.

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

Embodiment

This novel bidirectional reflectance distribution function (BRDF) measurement mechanism comprises a fixed light source 1, detector 2 and sample support parts, realizing bidirectional reflectance distribution function in half spherical space (BRDF) measures, it is characterized in that, described fixed light source throws light on downwards, light source below is provided with six axis robot 3, sample support parts are installed on six axis robot, clamping test sample 4 on sample support parts, six axis robot one side is provided with the probe rotary unit 5 of doing ± 180 ° of rotations in vertical plane, probe rotary unit is provided with detector, and detector points to sample center; Operation six axis robot, by changing the mode of the sensing of illuminated sample normal and position angle and rotation probe rotary unit, rectilinear motion and roll α, driftage β, pitching γ attitude that six axis robot is realized its working sections X/Y/Z direction in the certain limit of space by axle rotating unit change, need to keep working sections center XYZ constant, to keep the centre coordinate of sample constant, carry out bidirectional reflectance distribution function measurement.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 bearing, and the detector 2 that probe orientation is vertically pointed to sample center is installed on the cross bar of L shaped bar.

Claims (1)

1. a novel bidirectional reflectance distribution function measurement mechanism, comprise a fixed light source, detector and sample support parts, realizing bidirectional reflectance distribution function in half spherical space (BRDF) measures, it is characterized in that, described fixed light source throws light on downwards, light source below is provided with six axis robot 3, sample support parts are installed on six axis robot, clamping test sample 4 on sample support parts, six axis robot one side is provided with the probe rotary unit 5 of doing ± 180 ° of rotations in vertical plane, probe rotary unit is provided with detector, and detector points to sample center; Operation six axis robot, by changing the mode of the sensing of illuminated sample normal and position angle and rotation probe rotary unit, rectilinear motion and roll α, driftage β, pitching γ attitude that six axis robot is realized its working sections X/Y/Z direction in the certain limit of space by axle rotating unit change, need to keep working sections center XYZ constant, to keep the centre coordinate of sample constant, carry out bidirectional reflectance distribution function measurement; 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 bearing, and the detector 2 that probe orientation is vertically pointed to sample center is installed on the cross bar of L shaped bar.