GB/T 2831-1981 Test method for surface deviation of optical parts (aperture identification)
Some standard content:
UDC681.4.084：621.753.1
National Standard of the People's Republic of China
GB2831—81
Surface form deviation of optical elements--Inspection methods
Published on December 25, 1981
Implemented on October 1, 1982
Approved by the General Administration of Standards
National Standard of the People's Republic of China
Inspection methods for surface form deviation of optical elements
(Aperture identification)
Surface form deviation of optical elements-Inspection methods
UDC 681.4.084
:621.753.1
GB 2831 81
This standard is applicable to the surface deviation of spherical (including flat) optical components tested by the principle of equal-thickness light wave interference. 1. Terms, symbols, and codes
1.1 Surface deviation
The deviation of the optical surface under test relative to the reference optical surface is called surface deviation. The surface deviation is determined by the number, shape, change and color of the interference fringes (commonly known as aperture) observed at a vertical position within the circular test range.
Surface deviation includes the following three items:
a: The deviation of the radius of curvature of the optical surface under test relative to the radius of curvature of the reference optical surface is called radius deviation. The aperture number corresponding to this deviation is represented by N.
b. The deviation corresponding to the unequal aperture numbers generated by the optical surface under test and the reference optical surface in two mutually perpendicular directions is called astigmatism deviation. The aperture number corresponding to this deviation is represented by △,N. C. The local irregularity of the interference fringes produced by the optical surface under test and the reference optical surface in any direction is called the local deviation. The aperture number corresponding to this deviation is represented by △2N. 1.2 Aperture positive and negative signs
Regulations: high aperture (convex) is positive (corresponding to middle contact); low aperture (concave) is negative (corresponding to edge contact). 2 Identification of high and low apertures
2.1 Identification of high and low apertures in general
Low aperture: When the air gap is reduced, the fringes move from the edge to the center as shown in Figure 1a. High aperture: When the air gap is reduced, the fringes move from the center to the edge as shown in Figure 1b. Issued by the General Administration of Standardization of the People's Republic of China on December 25, 1981
Implemented on October 1, 1982
2.2 Identification of high and low apertures when the aperture number is small
GB2.831-81
Figure 1 Identification of high and low apertures
Low aperture: When the air gap is reduced, the bending direction and movement direction of the stripes are shown in Figure 2a. High aperture: When the air gap is reduced, the bending direction and movement direction of the stripes are shown in Figure 2b. Figure 2 Identification of high and low apertures when the aperture number is small
Note: In Figures 1 and 2, P is the force direction and force point, and d represents the movement direction of the stripes. 2
GB2831—81
2.3·When observing under white light, high and low apertures can also be identified according to the sequence of aperture colors. Low aperture: The color sequence from the center to the edge is "blue, red, yellow", etc., as shown in Figure 3a. High aperture: The color sequence from the center to the edge is "yellow, red, blue", etc. as shown in Figure 3b. a
Figure 3 Identification of high and low apertures by the sequence of aperture colors 3 Measurement of aperture
3.1 Measurement of light pattern number N
3.1.1 In the case of a large number of apertures, half of the maximum number of fringes in the diameter direction within the effective inspection range is used for measurement as shown in Figure 4. N= 3
Figure 4 Measurement of aperture number N
GB2831-81
Figure 4 shows the measurement method of aperture number N when there is only a radius deviation between the optical surface under test and the reference optical surface, as well as the error curve indicating the size and direction of the deviation. Among them, the dotted line represents the reference optical surface, and the curve represents the size and direction of the deviation of the sphere (or plane) relative to the reference optical surface. The distance between parallel lines represents 1/2. 3.1.2 When the aperture number is small, the aperture number N is measured by the ratio (N) of the bending amount (h) of the interference fringes in the diameter direction to the distance (H) between the fringes as shown in Figure 5. Figure 5 Measurement of the aperture number when N<1
In the figure: a. The distance between the centers of two adjacent dark (or bright) fringes is taken as the distance between the fringes (H). b. The number of fringes is generally 3 to 5.
c. Calculate as shown in the figure: N=
3.2 Measurement of the astigmatic aperture number A,N
△,N is measured by the absolute value of the maximum algebraic difference of the aperture number N in two mutually perpendicular directions. 3.2.1 Measurement of the elliptical astigmatic aperture number △,N is shown in Figure 6. N=3
A,N= 1
Figure 6 Measurement of the ellipse image astigmatism number A,NFigure 6 shows that the aperture numbers N and N of the optical surface under test in the X-X and Y-Y directions are not equal, and the deviation directions are the same. In the legend, N=-2, Nu=-3, then the aperture number of the tested surface N=3, and the astigmatism aperture number A,N=N-Ny=1. GB 283181
3.2.2 Measurement of the saddle image astigmatism number △,N is shown in Figure 7. N=2
A,N= 3
Figure 7 Measurement of saddle-shaped astigmatism circle number △, N Figure 7 shows that the deviation directions of the inspected optical surface in the XX and YY directions are opposite. In the legend, N=-1, N=+2, then the aperture number of the inspected surface is N=+2, and the saddle-shaped astigmatism circle number △, N=Nx-NI=3. 3.2.3 The measurement of cylindrical astigmatism circle number A, N is shown in Figure 8. N=
Figure 8 Measurement of cylindrical astigmatism circle number A, N
Figure 8 shows that the aperture numbers N and Ny of the inspected optical surface in the XX and YY directions are not equal. Among them, the aperture number N in a certain direction is 0, in the legend, Nz=-1, Nu=0, then the aperture number of the inspected surface is N=-1, and the cylindrical astigmatism circle number △, N=Nz-Nl=1. GB 2831 --81
3.2.4 When the aperture number is small, the measurement of the astigmatism aperture number A, N is shown in Figure 9. Ng=0.4
A, N= 0.2
Figure 9 Measurement of astigmatic aperture number △,N when N<1 Figure 9 shows that the aperture numbers of the optical surface under test in the XX direction and the YY direction are not equal, while Nr and Nu are both less than 1. N. and Nu can be determined based on the curvature of the interference fringes in the two directions. In the example, Nz=-0.2, N=-0.4, then the aperture number N=-0.4 of the tested surface, and the astigmatic aperture number A,N=|NN=0.2. 3.3 Measurement of local aperture number △N
△,N is measured by the ratio of the deviation (e) of the local irregular interference fringes from the ideal smooth interference fringes to the spacing (H) between two adjacent fringes.
3.3.1 Measurement of central local aperture number △,N is shown in Figure 10. Figure 10 Center The measurement of local aperture number △2N Figure 10a shows low aperture center low A, N:
Figure 10b shows low aperture center high △, N=
GB2831-81
3.3.2 The measurement of edge local aperture number △, N is shown in Figure 11. =0.28
Figure 11 The measurement of edge local aperture number △, N Figure 11a shows low aperture warping A, N=
Figure 11b shows low aperture return A2N=
3.3.3 The measurement of local aperture number △2N with local deviation in both center and edge is shown in Figure 12. Figure 12 The measurement of local aperture number A2N with local deviation in both center and edge
Figure 12a shows low aperture center high, warping. GB 2831-81
Center local aperture number A, N'=www.bzxz.net
Edge local aperture number △, N\=
Then the local aperture number of the inspected surface takes the maximum value of △, N=0.4Figure 12b shows that the low aperture center is low and returns to the edge. e,
Center local aperture number A2N'=-
Edge local aperture number A, N"=
Then the local aperture number of the inspected surface takes the maximum value of △, N=0.35e2
3.4The aperture number N of the arched aperture and the local aperture number △, N are measured in Figure 13.0.3
Figure 13Aperture number N and local aperture number A of the arched aperture,Measurement of N
When the aperture to be tested is an arcuate aperture and there is a dispute over the direction of N, it is stipulated that N and △,N should be determined based on the principle that △,N is the smallest. For example, when the tested surface shows an interference pattern as shown in Figure 13, the determination of N and A,N of the tested surface may cause controversy. In this case, it can be determined according to the following method. In Figure 13, if an extended line is drawn based on the interference fringes of the edge part and considered as a smooth interference fringes, the deviation of its center from the smooth interference fringes is e1,A,N\==0.4. On the contrary, if the interference stripe in the center is used as a reference to draw the H,7.5
extension line, and consider it as a smooth interference stripe, the deviation of its edge from the smooth interference stripe is e2, AN\=%==0.6
Comparing the two, we get △A,N\>△2N', so the aperture number N of the inspected surface: h
=0.53, AzN=0.4.
3.5 There is no requirement for the measurement of the aperture number N of the surface for the astigmatic aperture number △,N and the local aperture number △2N. 3.5.1 When the aperture number is large and the change of the aperture is irregular, the aperture number N is measured by the maximum number of fringes within the radius. As shown in Figure 14, the N of the inspected surface is 6. 8
GB2831-81
Figure 14 Measurement of irregular aperture number N
3.5.2 When the aperture number is small, such as an S-shaped aperture, N is measured according to the method shown in Figure 15. The N of the inspected surface Figure 15 Measurement of S-shaped aperture number N
3.5.3 When the accuracy requirement is not high, the aperture number can also be measured according to the interference color. For details, see Appendix A (reference). 4 Marking method
4.1 The maximum radius deviation allowed by the inspected optical surface is expressed in N apertures. If N=2, it means that the maximum radius deviation allowed between the inspected optical surface and the reference optical surface is 2 apertures. =0.4
Generally, the aperture number does not need to be marked with a positive or negative sign. If necessary, "+" or "" can be added before "N". 4.2 The maximum allowable difference in the aperture number of the optical surface under test in two mutually perpendicular directions (astigmatism deviation) is represented by A, N. 9
GB 2831-81
The maximum allowable value of the irregularity (local deviation) relative to the smooth interference fringes is represented by △, N. For example:
a If △, N=0.1, it means that the maximum allowable astigmatism aperture number is 0.1; if △, N=0.1, it means that the maximum allowable local aperture number is 0.1; b.
If △N=0.1, it means that the maximum allowable astigmatism aperture number and local aperture number are both 0.1. c.
4.3 If necessary, the test value can be marked after the N value. The diameter of the test range, such as N = 2 (60), which means that the maximum aperture number allowed within the Φ60mm test range is 2.
5 Test conditions
5.1 The reference wavelength for calculating the standard aperture number is λ. = 546.1nm. When other monochromatic light sources are used for testing, the N value specified in the technical documents should be corrected as follows.
For example, when testing with a reference wavelength of λ = 632.8nm, the allowed N632.8 is: 546.1
N632.8 = N 546.1 X
Assume: N546.1=2, then N632.8=1.72
=0.86N546.1
5.2 During inspection, it is best to use monochromatic light for illumination. In general, white light can be used for illumination. At this time, the same color should be used to evaluate the aperture.
5.3 When determining the aperture number, if conditions are limited and observation cannot be made in a vertical position, the aperture number N should be corrected according to the following formula. N:
Where: N is the aperture number when observing in a vertical position; N'
N is the aperture number observed when it is inclined at an angle α to the vertical direction. If N=1, cosa=45°,
then N:
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