Optical module with stray light baffle
An optical device includes a substrate and an optical transmitter, which is mounted on the substrate and includes an optical emitter, which is configured to emit a beam of optical radiation, and a transmission lens assembly, which is configured to direct the beam along a transmit axis toward a target. An optical receiver is mounted on the substrate alongside the optical transmitter and includes an optical sensor and an objective lens assembly, which is configured to focus the optical radiation that is reflected from the target along a receive axis onto the optical sensor. An optical baffle is disposed asymmetrically relative to the transmit axis and has an asymmetrical shape configured to block preferentially stray radiation emitted from the optical transmitter toward the receive axis.
1. An optical device, comprising:
a substrate;
an optical transmitter, which is mounted on the substrate and comprises an optical emitter, which is configured to emit a beam of optical radiation, and a transmission lens assembly, which comprises one or more lenses mounted in a lens barrel and is configured to direct the beam along a transmit axis toward a target;
an optical receiver, which is mounted on the substrate alongside the optical transmitter and comprises an optical sensor and an objective lens assembly, which is configured to focus the optical radiation that is reflected from the target along a receive axis onto the optical sensor; and
an optical baffle protruding asymmetrically relative to the transmit axis from an end surface of the lens barrel that is adjacent to the optical emitter toward the substrate in a location between the transmit axis and the receive axis and having an asymmetrical shape configured to block preferentially stray radiation emitted from the optical transmitter toward the receive axis.
2. The device according to claim 1 , wherein the substrate comprises an electrical circuit substrate on which the optical emitter and the optical sensor are mounted, and the device comprises ancillary electronic components, which are mounted on the electrical circuit substrate and connected to the optical emitter and the optical sensor by electrical circuit traces.
3. The device according to claim 2 , and comprising a case, which contains the transmission lens assembly and the objective lens assembly and is fixed to the substrate so that the transmission lens assembly and the objective lens assembly are positioned respectively over the optical emitter and the optical sensor.
4. The device according to claim 1 , wherein the optical baffle is an integral part of the lens barrel.
5. The device according to claim 1 , wherein the optical baffle comprises a collar mounted on the lens barrel.
6. The device according to claim 1 , wherein the optical baffle comprises an aperture configured to pass a predefined fraction of the emitted beam through the baffle toward the optical sensor.
7. The device according to claim 1 , and comprising a light guide extending through the baffle and configured to pass a predefined fraction of the emitted optical radiation through the baffle toward the optical sensor.
8. The device according to claim 1 , wherein the optical baffle comprises a compressible radiation-absorbing material, which is compressed upon assembly of the device, thereby preventing the stray radiation from reaching the optical sensor.
9. An optical device, comprising:
a substrate;
an optical receiver, which is mounted on the substrate and comprises:
an optical sensor mounted in a chip package;
a gasket comprising a compressible radiation-absorbing material surrounding the optical sensor on an upper side of the chip package; and
an objective lens assembly, which comprises:
one or more lenses configured to focus optical radiation along a receive axis onto the optical sensor; and
a lens barrel, which contains the one or more lenses, and which is mounted in the device so as to compress the radiation-absorbing material, thereby preventing stray radiation from reaching the optical sensor.
10. The device according to claim 9 , and comprising an optical transmitter, which is mounted on the substrate alongside the optical receiver, and which is configured to emit a beam of the optical radiation along a transmit axis toward a target, wherein the one or more lenses are configured to focus the optical radiation that is reflected from the target onto the optical sensor.
11. The device according to claim 10 , wherein the optical transmitter comprises a transmission lens assembly, and wherein the device comprises a case, which contains the transmission lens assembly and the objective lens assembly and is fixed to the substrate so that the transmission lens assembly and the objective lens assembly are positioned respectively over the optical emitter and the optical sensor.
12. The device according to claim 9 , wherein the substrate comprises an electrical circuit substrate on which the optical emitter and the optical sensor are mounted, and the device comprises ancillary electronic components, which are mounted on the electrical circuit substrate and connected to the optical emitter and the optical sensor by electrical circuit traces.
13. A method for optical sensing, comprising:
mounting an optical transmitter on a substrate, the optical transmitter comprising an optical emitter, which is configured to emit a beam of optical radiation, and a transmission lens assembly, which comprises one or more lenses mounted in a lens barrel and is configured to direct the beam along a transmit axis toward a target;
mounting an optical receiver on the substrate alongside the optical transmitter, the optical receiver comprising an optical sensor and an objective lens assembly, which is configured to focus the optical radiation that is reflected from the target along a receive axis onto the optical sensor; and
positioning an optical baffle to protrude asymmetrically relative to the transmit axis from an end surface of the lens barrel that is adjacent to the optical sensor toward the substrate in a location between the transmit axis and the receive axis, the optical baffle having an asymmetrical shape configured to block preferentially stray radiation emitted from the optical transmitter toward the receive axis.
14. The method according to claim 13 , wherein the substrate comprises an electrical circuit substrate on which the optical emitter and the optical sensor are mounted, and the method comprises mounting ancillary electronic components on the electrical circuit substrate for connection to the optical emitter and the optical sensor by electrical circuit traces.
15. The method according to claim 13 , wherein the optical baffle is an integral part of the lens barrel.
16. The method according to claim 13 , wherein positioning the optical baffle comprises mounting a collar comprising the optical baffle on the lens barrel.
17. The method according to claim 13 , wherein the optical baffle comprises an aperture configured to pass a predefined fraction of the emitted beam through the baffle toward the optical sensor.
18. The method according to claim 13 , wherein the optical baffle comprises a compressible radiation-absorbing material.