The measurement of diffuse reflection factor can be used to obtain the following optical properties: blue light diffuse reflection factor (blue light whiteness) of pulp, paper and board; paper opacity; light scattering and light absorption coefficient of pulp, paper and board; paper and board color wait.
1 definition
(1) Reflection factor R is the ratio of the radiant flux reflected by an object to the radiant flux reflected by a fully reflective diffuser under the same conditions, expressed as a percentage.
(2 ) The internal reflection factor R is the reflection factor when the thickness of the sample layer reaches the point where the diffuse reflection factor does not increase with the increase in thickness. (3) The primary reference standard is a satisfactory uniform and completely reflective diffuser with a reflectance value equal to 1 in the full spectral range. Achieved by standardized laboratories with instruments that measure the absolute diffuse reflectance factor. For the first-level reference standard of fluorescence whiteness and brightness calibration and transmission, it is realized with a reference instrument that strictly complies with the national standards.
(4) Secondary reference standardization laboratories measure and calibrate transfer standards based on primary reference standards. Authorized laboratories use this standard to calibrate their reference instruments.
(5) Laboratories authorized by the third-level reference standard test the calibrated standard with the reference instrument calibrated by the second-level reference standard. T. Laboratories use these standards to calibrate their instruments and working standards.
2 Basic conditions for the transfer of standard values
2.1 Reference instrument
Authorized laboratories are required to keep the reference instruments used in proper working order. --It is necessary to regularly exchange the tertiary reference standards to calibrate the reference instruments in various places. The performance parameters of the benchmark instrument are as follows.
(1) Geometric conditions
The sample is diffusely illuminated by an integrating sphere, and the diameter of the integrating sphere is not less than 100 nm. The sum of the pore areas in the ball does not exceed 10% of the ball area. The diameter of the sample hole is not less than 20 mm.
The angle between the normal of the sample surface and the axis of the observation beam is 8°, and the maximum angle between the observation axis and the observation light is 2.5°±0.2°.
A gloss absorber that can be opened or closed is provided in the direction corresponding to the observation hole at an angle of 8° to the normal of the sample surface.
(2) Spectral characteristics
Simulates D65 light source lighting, especially with the same rich UV content as D65 light source. Regularly calibrate the spectral characteristics of the instrument light source with a fluorescent standard plate.
The instrument is equipped with an ultraviolet cut-off filter, the cut-off range is less than 400 nm.
The spectral characteristics of the instrument receiver, integrating sphere and optical filter shall comply with the provisions of various methods for measuring optical properties.
The linearity error of the instrument is not more than 0.3%.
2.2 Secondary reference standard
①为标定授权实验室基准仪器刻度的上限，要用二级参比标准，这些标准可使用硫酸钡或氧化镁压片。压制硫酸钡和氧化镁片的方法如下。
a、设备及材料
1.硫酸钡或氧化镁应具有最高纯度．其反射因数应在标准化实验室之间校准。
2.压粉器将适量毓酸钡或氧化镁粉末压成直径不小于40 mm、厚5 mm的压片，其表面平直而无光泽。
3.瓷匙。
4.合成纤维软刷。
5.无荧光成分的合成洗涤剂。
6.丙酮·分析纯。
b．硫酸钡或氧化镁压片的制备，仔细地清洗并干燥压粉器的各个部件，用瓷匙将适量硫酸钡或氧化镁粉移入组合好的压粉器内，按操作说明书规定把粉末压成压片。从压粉器中取出压片，在低角度照射和观察条件下检查表面质量。其表面应平直，无光洋部分，无凹陷或凸起情况。
制备2~-3片压片，制备完压片需要仔细清洗压片器的各个部件。特别是毛玻璃表面、要用蒸馏水和合成洗涤剂刷洗，然后在蒸馏水中有效清洗，最后用丙酮冲洗，风干。合成洗涤剂软刷应专用，不用时保仔好以防污染。
硫酸钡或氧化镁贮存瓶一定要密封，从瓶中取出的粉末不许再放回瓶内。
肉眼检查合格的压片再用仪器枪查其反射因数的均一性，各片的反射因数之差应在0.1%之内，相差较大表明制备不当。
c．硫酸钡或氧化镁的性质。同一贮存瓶的硫酸钡或氧化镁正.确制成的压片反射因数之差不大于0.1%。同一贮存瓶硫酸钡或氧化镁制片的反射因数同瓶上标记的值应一致。在无灰尘污染（保存在干燥器内〉的情况下，压片在制成两周内反射因数应无变化。在空气相对湿度适当变化的条件下压片的反射因数无变化。
②为标定基准仪器的荧光白度量值，要用含荧光增白剂和相同材料不含荧光增白剂的两块二级参比标准。
2.3三级参比标准
授权的实验室应定期标定和发放三级参比标准，并附有基准仪器的精确标定值，以适应不同被测项目的要求。三级参比标准应具有以下特点。
不同反射因数的纸样或毛面陶瓷板（不含荧光增白剂)。加有荧光增白剂的白板和相同材料不加荧光增白剂的白板。不同颜色的色板。
Under careful protection, within the specified time limit and specified instrument accuracy. Its reflection factor does not change. Clean, opaque and have a uniform reflective factor.
The surface is flat and will not have a high gloss except for special applications.
2.4 Working Standards
Matte ceramic plates, opal glass plates, etc. can be used for routine calibration of working laboratory instruments.
2.5 A black plate with an absolute reflection factor not greater than 0.1%% is used to calibrate the zero point of the instrument.
3 Calibration methods of working laboratory instruments and working standards
① The reflectance photometer used in the working laboratory has basically the same geometrical optical characteristics as the reference instrument introduced in (8.22.2).
②Two rough-faced ceramic plates or milky white glass plates, one as the working standard plate and one as the control plate as T. To ensure high accuracy of the test. Calibration is performed using tertiary reference standards with different diffuse reflectance factors. The average value of the calibration values corresponding to the three grades of reference standards is used as the calibration value, and the difference between the calibration values corresponding to each blue-level standard shall not exceed 0.3%.
a, Calibration of the working standard plate. Calibrate with the third-level standard, insert the optical filter for measurement into the light beam, and operate according to the instructions provided by the instrument and the factory. Determine the reflection factor of the working standard against the secondary standard to the nearest 0.1%, and repeat the procedure for the .T. standard control panel.
When removing the barium sulfate or magnesium oxide standard from the sample hole, use a clean cloth to remove any powder adhering to the contact surface. I:. To prevent sticking to the work standard applied later.
b. The working laboratory obtains the third-level standard from the authorized laboratory every two months. Use the three-level standard to calibrate the working standard and the control standard of the working standard once a month. Wipe the upper standard once a week, and then calibrate it once with the control standard. If there is any change in the diffuse reflection factor of the working standard, clean it according to the procedure. If there is still a change after washing, use the third-level reference standard to calibrate .
c, Cleaning of working standards. Scrub the surface with distilled water, a soft synthetic bristle brush, and a non-fluorescent detergent. After effectively cleaning with distilled water, wash with ethanol, and dry until the measured diffuse reflection factor does not change.
4 test steps
Take samples, test, calculate and report the measurement results according to the specific provisions of the standard method for measuring the diffuse reflection factor related to the test item.
