Athermal optical assembly
This disclosure describes optical assemblies that generate output with substantial stability over a wide variation in temperature. The optical assemblies can be integrated, for example, as part of array generators arranged to project an array or other pattern of dots onto an object or projection plane.
1. A hybrid optical assembly comprising:
a first transmissive substrate;
a first aspherical lens on a first side of the first transmissive substrate;
a second hybrid diffractive/refractive lens on a second side of the first transmissive substrate;
a second transmissive substrate separated from the first transmissive substrate;
a third aspherical lens on a first side of the second transmissive substrate; and
a fourth aspherical lens on a second side of the second transmissive substrate;
wherein the third aspherical lens faces the second hybrid diffractive/refractive lens,
wherein the output of the hybrid optical assembly exhibits substantial stability over a temperature range of 20° C.-100° C., and
wherein the first and second transmissive substrates are separated from one another by a distance in a range of 4 mm-10 mm.
2. The hybrid optical assembly of claim 1 , further comprising an array of light emitting elements, wherein the light emitting elements are vertical cavity surface-emitting lasers (VCSELs).
3. The hybrid optical assembly according to claim 1 , wherein the first aspheric lens, the second hybrid diffractive/refractive lens, the third aspheric lens, and the fourth aspheric lens have focal-length-normalized diameters of 0.49, 0.49, 0.35, and 0.29, respectively.
4. The hybrid optical assembly according to claim 1 , wherein the first aspheric lens, the second hybrid diffractive/refractive lens, the third aspheric lens, and the fourth aspheric lens have focal-length-normalized thicknesses of 0.0044, 1.048, 0.067, and 0.067, respectively.
5. The hybrid optical assembly according to claim 1 , wherein the first aspheric lens has a focal-length-normalized curvature of 9.21, the second hybrid diffractive/refractive lens has a focal-length-normalized curvature of 2.85, the third aspheric lens has a focal-length-normalized curvature of 0.34, and the fourth aspheric lens has a focal-length-normalized curvature of 0.78.
6. The hybrid optical assembly according to claim 5 having an aspect ratio of 0.356.
7. The hybrid optical assembly according to claim 5 , the first, third and fourth aspherical lenses have the following coefficients, respectively:
1 st aspheric
3 rd aspheric
4 th aspheric
Coefficient (r)
lens
lens
lens
Fourth-order
−0.103
0.114
0.382
Sixth-order
0
2.4032
3.544
Eighth-order
0
−41.19
−62.281
Tenth-order
0
324.92
523.773
Twelfth-order
0
−1203.11
−1930.264
Fourteenth-order
0
1694.44
2348.243
and wherein the second hybrid diffractive/refractive lens has the following coefficients:
2 nd hybrid
diffractive/refractive
Coefficient (□)
lens
Aspheric Fourth-order
−0.115
Aspheric Sixth-order
−0.859
Aspheric Eighth-order
5.705
Aspheric Tenth-order
−17.849
Aspheric Twelfth-order
28.092
Aspheric Fourteenth-order
−17.554
Diffractive-phase Second-order
−525.287
Diffractive-phase Fourth-order
71.546
Diffractive-phase Sixth-order
−30.983.
8. The hybrid optical assembly according to claim 5 having an aspect ratio of 0.224.
9. The hybrid optical assembly according to claim 5 , wherein the first, third and fourth aspheric lenses have the following coefficients, respectively:
1 st aspheric
3 rd aspheric
4 th aspheric
Coefficient (r)
lens
lens
lens
Fourth-order
−0.026
0.028
0.095
Sixth-order
0
0.237
0.350
Eighth-order
0
−1.611
−2.436
Tenth-order
0
5.034
8.115
Twelfth-order
0
−7.384
−11.847
Fourteenth-order
0
4.119
5.709
and wherein the second hybrid diffractive/refractive lens has the following coefficients:
2 nd hybrid
diffractive/refractive
Coefficient (□)
lens
Aspheric Fourth-order
−0.027
Aspheric Sixth-order
−0.085
Aspheric Eighth-order
0.223
Aspheric Tenth-order
−0.277
Aspheric Twelfth-order
0.172
Aspheric Fourteenth-order
−0.043
Diffractive-phase Second-order
−834.621
Diffractive-phase Fourth-order
113.678
Diffractive-phase Sixth-order
−49.228.
10. A hybrid optical assembly comprising:
a first transmissive substrate;
a first aspherical lens on a first side of the first transmissive substrate;
a second hybrid diffractive/refractive lens on a second side of the first transmissive substrate;
a second transmissive substrate separated from the first transmissive substrate;
a third aspherical lens on a first side of the second transmissive substrate;
a fourth aspherical lens on a second side of the second transmissive substrate; and
an array of light emitting elements, wherein the light emitting elements are vertical cavity surface-emitting lasers (VCSELs);
wherein the third aspherical lens faces the second hybrid diffractive/refractive lens,
wherein the output of the hybrid optical assembly exhibits substantial stability over a temperature range of 20° C.-100° C., and
wherein the first and second transmissive substrates are composed of clear borosilicate glass and the first, second, third and fourth lenses are composed of epoxy.
11. An optical pattern generator comprising:
an array of light emitting elements; and
a hybrid optical assembly including
a first transmissive substrate,
a first aspherical lens on a first side of the first transmissive substrate,
a second hybrid diffractive/refractive lens on a second side of the first transmissive substrate,
a second transmissive substrate separated from the first transmissive substrate,
a third aspherical lens on a first side of the second transmissive substrate, and
a fourth aspherical lens on a second side of the second transmissive substrate,
wherein the third aspherical lens faces the second hybrid diffractive/refractive lens, and
wherein the output of the hybrid optical assembly exhibits substantial stability over a temperature range of 20° C.-100° C.; and
wherein the array of light emitting elements is disposed such that light generated by the light emitting elements passes through the fourth lens, the third lens, the second lens and the first lens of the hybrid optical assembly, in that order, so as to project a pattern of optical dots corresponding to the arrangement of the light emitting elements.
12. The optical array generator of claim 11 wherein the light emitting elements are vertical cavity surface-emitting lasers (VCSELs).