Measurement method of thickness of subsurface damaged layer of bucky optical material

[0031] Example 1

[0032] figure 2 , image 3 A processing example of a flat sample of optical glass is shown. Measurement of subsurface damage layer thickness of a K9 optical glass flat sample: in image 3 Step1: Perform sub-surface damage detection on the optical surface after grinding with W20 abrasive grains for 20 minutes: such as image 3 As shown in Step 2, a tiny slope with an inclination angle of θ=6' is processed by the magnetorheological polishing process ( figure 2 ), along the direction of magnetorheological polishing indicated by the arrow, the profile information at different depths from the original plane can be reflected on the inclined plane. The inclined surface after magnetorheological polishing is treated with HF acid etching agent to clean the surface and further expose and enlarge the cracks on the inclined surface. Use the roughness profiler to scan from the dashed line near the start boundary of the slope ( figure 2 , image 3 Step3), feed along the inclined plane in the direction of the arrow according to the set interval, and continuously measure the roughness at the dotted line ( figure 2 , image 3 Step 4), measure the line roughness values ​​of the dotted lines at different positions on the slope in turn. Get the relationship curve between slope feed and roughness, such as Figure 4 shown. During the measurement, record the starting boundary scan point coordinate X of the inclined plane 1 =80. Then, the curve is processed by S-spline to obtain the coordinate X of the scanning point where the roughness value tends to be stable. 2 = 240. In this way, the length of the crack layer on the slope is L 1 =(X 2 -X1 )×0.01mm=1.2mm. The width of the internal stress layer on the slope measured by the X-ray internal stress is very small, and the width of the relative crack layer is negligible, so the width of the subsurface damage layer on the slope is about 1.2mm. From the known polishing slope angle θ, according to d = Lsinθ=1.2sin6', and the thickness of the subsurface damage layer on the surface of the optical glass is 2.09 μm.

[0033] Further, it can also be accurately obtained by scanning the profile of the inclined plane with the roughness profiler: the inclination angle of the inclined plane is 6 minutes and 49 seconds ( Figure 5 ), so according to d=Lsinθ=1.2sin6’49″, the thickness of the subsurface damage layer on the optical surface of the optical glass can be accurately corrected to 2.37 μm.

[0034] Example 2

[0035] like Image 6 A specific measurement example of the thickness of the subsurface damage layer of an optical ceramic spherical mirror is shown in Image 6 In Step 1, the optical surface after 20min grinding with W40 abrasive grains is subjected to sub-surface damage detection: such as Image 6 As shown in Step 2: Using the magnetorheological polishing process, a detection circular plane is thrown on a spherical sample with a radius of curvature R, and its horizontal radius is r. The cutting plane and the original spherical surface form a spherical crown ( Image 6 Step2), the circumference of the plane is shallow from the original surface, and the center of the circle is deep from the original surface. The cutting plane is treated with corrosive chemical reagents to amplify the exposure of subsurface cracks on the cutting plane; Image 6 In Step3 and Step4: use the white light interferometer to scan the point P at the circumference of the cut-out circular plane 1 (X 1 , Y 1 ,Z 1 ) to the center of the circle in turn along the radial direction, and measure the change curve of the roughness at different positions along the horizontal radius of the circular plane with the feed ( Figure 7 ). The composition of optical ceramics and optical glass is different, and the measured roughness curve is also different, such as Figure 7 As shown, the sample in this example uses optical ceramics, and the roughness change curve will have a pole. Find the coordinate P at the circular scanning point on the change curve 1 (X 1 , Y 1 ,Z 1 ) and the coordinate P of the pole on the change curve 2 (X 2 , Y 2 ,Z 1 ), by the spherical equation X 2 +Y 2 +Z 2 =R 2 and polishing depth h to get the original spherical surface and P 2 (X 2 , Y 2 ,Z 1 ) vertically corresponds to the point P 3 (X 2 , Y 2 ,Z 2 ) of the Z coordinate Z 2; Calculate the difference between the two points, that is, the thickness value of the subsurface damage layer d=|Z 1 -Z 2 |. In this example, the broad band of the subsurface internal stress layer on the inclined plane obtained by the X-ray internal stress measurement is also very small, and if it is ignored, the thickness of the subsurface damage layer on the spherical optical element is obtained as d=|Z 2 -Z 1 |. Specific measurement data: the pole position is 0.08mm ( Figure 7 ), radius R=100mm, polishing depth h=0.1mm, r=3.1mm, by the spherical equation X 2 +Y 2 +Z 2 = 10000 and polishing depth h = 0.1 mm, d = 0.0443 mm.