A quantitative test method for striae in optical materials, comprising:
- (1) establishing an index “striae value” for the quantitative expression of the striae in the optical materials;
- and establishing an algorithm of the striae value according to expression forms of the striae in optical materials and influencing factors of optical performance of the striae in optical materials;
- wherein the algorithm is shown as follows:
- S
- =
- ∑
- j
- =
- 1
- m
-
- ∑
- i
- =
- 1
-
- Δ
-
-
- g
- ji
- n
- ×
- ∑
- j
- =
- 1
- m
-
- a
- j
- Ad
- =
- Δ
-
-
- g
- m
-
- ∑
- j
- =
- 1
- m
-
- a
- j
- Ad
- ;
- wherein S is the striae value;
- i is a sequence number of gray pixel cells in a striae image of a measurement sample;
- Δgi is a gray value of the ith gray pixel cell in the striae image of the measurement sample;
- Δgm is an average gray value of the gray pixel cells in the striae image of the measurement sample;
- n is a total number of the gray pixel cells in the striae image of the measurement sample;
- j is a sequence number of striae in the striae image of the measurement sample;
- aj is an area of the jth striae in the striae image of the measurement sample;
- m is a total number of striae in the striae image of the measurement sample;
- A is a total area of the striae image of the measurement sample;
- and
- d is a thickness of the measurement sample;
- the stria value is a product of an average gray level of the striae and a percentage of the total area of the striae per thickness of the measurement sample;
- (2) constructing a photoelectric projection measurement apparatus which comprises a parallel light source system, the measurement sample, a first positive lens, a second positive lens and an image sensor successively along the direction of an optical axis;
- wherein a sample stage is provided to carry the measurement sample;
- (3) setting a gray ruler of light energy response for detection elements within a dynamic range of the image sensor of the photoelectric projection measurement apparatus, wherein the number of gray levels of the gray ruler is determined according to an expected measurement accuracy, there are 32 gray levels for a low accuracy, 64 gray levels for a medium accuracy and 128 or 256 gray levels for a high accuracy;
- and the range of each gray levels is a preset value, which can be changed according to measurement accuracy requirements;
- (4) making standard proof samples for calibrating the photoelectric projection measurement apparatus, wherein the standard proof samples are respectively a zero-gray standard proof sample, a medium-gray standard proof sample, a 25%-gray standard proof sample and a 75%-gray standard proof sample;
- the zero-gray standard proof sample is a standard proof sample without any striae defects inside;
- the medium-gray standard proof sample is a standard proof sample with a medium-gray (a 50% gray standard proof sample) in relation to the possible maximum-gray of the striae, and the medium-gray standard proof sample is used to calibrate the photoelectric projection measurement apparatus based on 50% gray value;
- all the standard proof samples share the same thickness, and are the same as the measurement sample in material mark or glass mark;
- (5) manufacturing the measurement sample to have the same thickness as the standard proof samples;
- and
- (6) calibrating the photoelectric projection measurement apparatus with the standard proof samples prepared in step (4);
- imaging the measurement sample with the calibrated photoelectric projection measurement apparatus to measure parameters of the area and gray of the striae image mentioned in step (1);
- and calculating the measured results with the formula established in step (1) to obtain the striae value of the measurement sample.