This standard specifies the geometric conditions for photographic reflection density measurement. This standard applies to the measurement of reflection density of photographic and printed materials, and also to the measurement of reflection of other materials. GB/T 12822-1991 Geometric conditions for photographic reflection density measurement GB/T12822-1991 Standard download decompression password: www.bzxz.net
This standard specifies the geometric conditions for photographic reflection density measurement. This standard applies to the measurement of reflection density of photographic and printed materials, and also to the measurement of reflection of other materials.

National Standard of the People's Republic of China
Geometric conditions for photographic reflection density measuremcnt
GB/T 12822 91
This standard refers to and adopts the international standard IS05/4-1983 Photographic-density measurement-Part 4: Geometric conditions for reflection density. 1 Subject content and scope of application
This standard specifies the geometric conditions for photographic reflection density measurement: This standard is only applicable to the measurement of reflection density of photographic and printed materials, and is also applicable to the measurement of reflection of other materials. 2 Referenced standardsbZxz.net
GB/T12823 Terminology, symbols, coordinate system and function representation for photographic density measurement GB11501 Spectral conditions for photographic density measurement 3 Definitions
3.1 Reflection factor R; reflection flux 4. The ratio of the absolute reflection flux is expressed by formula (1): R
3.2 Reflection density (or reflection factor density) DR: The reciprocal of the reflection factor is taken as the logarithm with base 10, which is expressed by formula (2): DR=
4 Standard reflection density
4.1 Incidence and exit geometry
The annular reflection measurement mode can be completed with an annular illumination and a vertically oriented detector or an illumination-detection system with this arrangement. This optical arrangement is called "annular incidence mode" or "annular exit mode" respectively. The annular incidence mode is illustrated in the figure below. If the arrow indicating the flux direction is reversed, the figure represents the "annular exit mode". Its geometric conditions are described by annular angular distribution and vertical angular distribution respectively. Depending on the mode, the angular distribution can be divided into two types: brightness distribution and responsivity distribution, and the responsivity distribution should include the influence of all optical components in the detection system. State Administration of Technology Supervision 1991-04-30 Approved for implementation on March 1, 1992
4.2 Sampling hole
CB/T12822—91
Geometry of annular incidence mode
The geometry of the optical system of the instrument determines the measurement area of ​​the sample, and this determined area is called the sampling hole. The sampling hole should be determined by the angle range detected by the detector. If a mechanical hole is placed on the plane of the sample, its area should be larger than the sampling hole, and its boundary should be at least 2 mm outside the boundary of the sampling hole. The detector's response to each point in the sampling hole should be the same, and the response to points outside the sampling hole should be the same. This can be achieved by a small and stable A certain radiation source is placed at different points in and around the sampling hole, and the change in the detector's responsivity is measured. The area of ​​the light source should be equal to 1/10 of the area of ​​the sampling hole. When the light source is located at any point in the sampling hole, the detector's responsivity should not be less than 90% of the maximum value. When the light source is located at any point around the sampling hole, the detector's responsivity should not be greater than 0.1% of the maximum value of the light source in the sampling hole. The maximum and minimum value of the sampling hole depends on the size of the optical system of the detector used to measure the reflection factor or reflection density. As long as each point in the sampling hole meets the conditions specified in 4.4 and 1.5, any size of sampling hole can be used. However, it cannot Small enough that the particle size, sample surface structure and diffraction effects have to be considered. For samples with poor uniformity, the size of the sampling hole should be specified (determined by the production and application departments).
4.3 Illumination area
The area of ​​the sample to be illuminated should be larger than the sampling hole diameter, and its boundary should be at least 2mm outside the sampling hole boundary. Ideally, the illumination on the illuminated area should be uniform. The uniformity of the illumination is measured by a photoelectric detector, which requires the aperture shape of the detector to be similar to the sampling hole, and the size to be 1/4 of the sampling hole. The illumination at any point on the illuminated area should be at least 90% of the maximum value. 4. 4 Annular distribution
The angular distribution of the incident beam brightness or the angular distribution of the detector responsivity shall take the maximum value when the angle with the normal line at the center of the sampling hole is 45°, and the value at any point on the circle with an angle less than 40° or greater than 50° with the normal line shall be so small that it can be ignored. The annular distribution of incident beam brightness or the angular distribution of the detector responsivity shall be expressed by the function expression method specified in Article 5.2 of GB/T12823-91. The angular distribution of the detector responsivity can be measured by the following method: a small hole light bar is placed on the sample plane, and a stable light source of suitable size is used to illuminate it at a given distance. The light source is moved to change the illumination angle of the detector, and the corresponding response value is recorded. For materials molded to simulate the fiber surface structure, if the annular illumination or annular detection is uneven along the azimuth angle, the measured density value is related to the orientation of the azimuth angle of the sample surface structure. If the sample is rotated around the Z axis in its body plane (XY half plane), the annular distribution is sufficiently uniform along the azimuth angle for this sample if the measured value of GB/T 12822-91 varies within the allowable range. 4.5 Normal direction distribution
The angular distribution of the incident beam brightness or the angular distribution of the detector's responsivity should reach a maximum value in the direction perpendicular to the sampling hole at the center of the sampling hole. The distribution at any point on the sampling hole that deviates from the normal by 5° should be small to a negligible degree. This angular distribution can be measured by the method described in 4.4. 4.6 Stray pass
Use clear optical elements, suitable screens and appropriate blackening of the surfaces facing the sample to reduce the stray pass to a negligible degree.
4.7 Substrate material
This standard stipulates that the sample should be in contact with the film substrate material. The substrate should be made of a diffuse reflective material without spectral selectivity and should have a standard reflection density value of more than 1.50. 4.8 Reference Standard
The standard reflection density is defined by a perfect diffuse reflector as a reference standard. The standard reflection density is defined by a perfect diffuse reflector as a reference standard. Since such a perfect diffuse reflector does not exist, a standard reflection plate (such as a sulfuric acid plate) is often used for calibration. The density relationship between this material and the perfect diffuse reflector should be known and used to determine the standard reflection density. The national computer laboratory can generally provide the standard reflection density of this reflective material. 4.9 Standard
The density value obtained using the above technical specifications can be called "standard reflection density" or simply "reflection density". In the function representation, this density can be expressed as D (40°～50; S: 5; 8) or % (5S: 40°～~50°), where 8 and 8 are defined as the spectral characteristics of the human radiation and the light detector, respectively. Additional Notes:
This standard was proposed and managed by the China National Institute of Metrology. The China National Institute of Metrology was responsible for drafting this standard, and the China Film Science and Technology Research Institute and the First Film Factory of the Ministry of Chemical Industry participated in the drafting. The main drafters of this standard were Jiang Changgui, Li Zaiqing, Jin Jiadong, Ji Jiaqi, and Tang Zhijian.
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