Monitoring DOE performance using total internal reflection

Patent metadata

Field	Value
Publication number	US-9528906-B1
Application number	US-201414548476-A
Country	US
Kind code	B1
Filing date	Nov 20, 2014
Priority date	Dec 19, 2013
Publication date	Dec 27, 2016
Grant date	Dec 27, 2016

Abstract

Optical apparatus includes a diffractive optical element (DOE), which includes multiple optical surfaces, including at least an entrance surface and an exit surface, and a side surface, which is not parallel to the optical surfaces of the DOE. A grating is formed on at least one of the optical surfaces so as to receive radiation entering the DOE via the entrance surface and to diffract the radiation into a predefined pattern comprising multiple diffraction orders that exit the DOE via the exit surface. An optical detector is positioned in proximity to the side surface so as to receive and sense an intensity of a high order of the radiation diffracted from the grating that passes through the side surface of the DOE.

First claim

The invention claimed is:

1. Optical apparatus, comprising:
a diffractive optical element (DOE), comprising:
multiple optical surfaces, which comprise at least an entrance surface and an exit surface;
a side surface, which is not parallel to the optical surfaces of the DOE; and
a grating, which is formed on at least one of the optical surfaces so as to receive radiation entering the DOE via the entrance surface and to diffract the radiation into a predefined pattern comprising multiple diffraction orders that exit the DOE via the exit surface; and

an optical detector, which is positioned in proximity to the side surface so as to receive and sense an intensity of a high order of the radiation diffracted from the grating that passes through the side surface of the DOE.

2. The apparatus according to claim 1 , wherein the side surface is perpendicular to the optical surfaces of the DOE.

3. The apparatus according to claim 1 , wherein the optical detector comprises a front surface that is in contact with the side surface of the DOE.

4. The apparatus according to claim 1 , wherein the optical surfaces of the DOE are configured so that the high order of the diffracted radiation reaches the side surface after reflecting internally within the DOE.

5. The apparatus according to claim 1 , and comprising a controller, which is coupled to receive a signal from the optical detector that is indicative of the intensity of the high order of the diffracted radiation and to monitor a performance of the DOE responsively to the signal.

6. The apparatus according to claim 5 , and comprising a radiation source, which is configured to direct the radiation toward the entrance surface of the DOE, wherein the controller is coupled to control an operation of the radiation source responsively to the monitored performance.

7. The apparatus according to claim 6 , wherein the controller is configured to inhibit the operation of the radiation source when the signal is outside a predefined range.

8. The apparatus according to claim 7 , wherein the diffraction orders that exit the DOE via the exit surface include a zero order, and wherein a change of the signal is indicative of an increase of an intensity of the zero order, and the controller is configured to inhibit the operation of the radiation source when the change exceeds a predefined threshold.

9. An optical method, comprising:
transmitting radiation through a diffractive optical element (DOE), which comprises multiple optical surfaces, including at least an entrance surface and an exit surface, and which comprises a grating, which is formed on at least one of the optical surfaces so as to receive the radiation entering the DOE via the entrance surface and to diffract the radiation into a predefined pattern comprising multiple diffraction orders that exit the DOE via the exit surface; and
receiving and sensing an intensity of a high order of the radiation diffracted from the grating that passes through a side surface of the DOE, which is not parallel to the optical surfaces of the DOE.

10. The method according to claim 9 , wherein the side surface is perpendicular to the optical surfaces of the DOE.

11. The method according to claim 9 , wherein the intensity is received by an optical detector in proximity to the side surface.

12. The method according to claim 11 , wherein a front surface of the optical detector is in contact with the side surface of the DOE.

13. The method according to claim 9 , wherein the optical surfaces of the DOE are configured so that the high order of the diffracted radiation reaches the side surface after reflecting internally within the DOE.

14. The method according to claim 9 , wherein sensing the intensity of the high order of the diffracted radiation comprises monitoring a performance of the DOE responsively to the sensed intensity.

15. The method according to claim 14 , wherein transmitting the radiation comprises directing the radiation from a radiation source toward the entrance surface of the DOE, and wherein the method comprises controlling an operation of the radiation source responsively to the monitored performance.

16. The method according to claim 15 , wherein controlling the operation comprises inhibiting the operation of the radiation source when the signal is outside a predefined range.

17. The method according to claim 16 , wherein the diffraction orders diffraction orders that exit the DOE via the exit surface include a zero order, and wherein a change of the signal is indicative of an increase of an intensity of the zero order, and wherein inhibiting the operation comprises turning off the radiation source when the change exceeds a predefined threshold.

Assignees

• Apple Inc

Inventors

• Yasovsky Alon
• Pesach Benny

Classifications

• G02B27/4205

  having a diffractive optical element [DOE] contributing to image formation, e.g. whereby modulation transfer function MTF or optical aberrations are relevant · CPC title

• G01J1/0407

  Optical elements not provided otherwise, e.g. manifolds, windows, holograms, gratings · CPC title

• G01M11/0207 Primary

  Details of measuring devices · CPC title

• G01N21/4788

  Diffraction (for sizing particles G01N15/0205) · CPC title

• G02B2005/1804

  Transmission gratings · CPC title