# US 9,753,241 B2 · Laser autocollimator using optical parasitic interference > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,753,241 B2 - Document ID: US9753241B2 - Status: Granted - Kind: B2 - Application number: 14/847,550 - Filed: 2015-09-08 - Published: 2017-03-09 - Granted: 2017-09-05 - Earliest claimed: 2015-09-08 - Assignees: Lockheed Martin Corporation - Applicants: Lockheed Martin Corporation - Inventors: Vincent P. Benischek; Mark S. Hinrichs; Francesco Pellegrino - Web page: https://patentgrep.com/patent/US9753241B2 ## CPC - G02B 7/003: {Alignment of optical elements (G02B7/001, G02B7/002 take precedence; for mirrors G02B7/1822)} - G01J 1/0266: {Field-of-view determination; Aiming or pointing of a photometer; Adjusting alignment; Encoding angular position; Size of the measurement area; Position tracking; Photodetection involving different fields of view for a single detector} - G01J 1/4257: {applied to monitoring the characteristics of a beam, e.g. laser beam, headlamp beam (monitoring arrangements for lasers in general H01S3/0014)} - G02B 27/14: operating by reflection only - H01S 3/0014: {Monitoring arrangements not otherwise provided for (photometry G01J1/00, e.g. G01J1/4257; radiation pyrometry G01J5/00; measuring coherence of light G01J9/00; measuring wavelength of light G01J9/00, e.g. G01J9/0246; measuring optical pulses G01J11/00; calorimetrically measuring power of laser beams G01K17/003)} - G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS - G01J: MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY (light sources F21, H01J, H01K, H05B; investigating properties of materials by optical means G01N) - H01S: DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL ## Abstract A laser autocollimator assembly that provides an objective, unambiguous, and simple means to achieve precise (for example, arc second or sub arc-second) alignment between the laser autocollimator assembly and a reference surface. The laser autocollimator assembly relies on optical parasitic interference between a reflected beam from the reference surface and the laser beam in the laser cavity that, when alignment is achieved, results in a disruption of the action of the laser, resulting in a reduction in the output power level of the laser beam. By monitoring the power level of the laser beam, for example monitoring the power level of the reflected beam, it can be determined that alignment has been achieved when the power level of the laser beam has been reduced to a minimum level. The power level can be automatically monitored, thereby eliminating the need for user interpretation. ## Claims ### Claim 1 A method comprising: a) providing a laser assembly that includes a laser transmitter, a beam splitter and a power detector; b) directing a laser beam from the laser transmitter through the beam splitter onto a reference surface; c) using the power detector, detecting a power level of a return reflected beam resulting from the laser beam impacting on the reference surface; d) adjusting the laser assembly and the reference surface relative to one another to cause the return reflected beam to interfere with the laser beam transmitted from the laser transmitter; e) repeating c) and d) until the power level of the return reflected beam detected by the power detector reaches a minimized power level. ### Claim 2 (depends on 1) The method of claim 1, wherein d) comprises adjusting the laser assembly relative to the reference surface. ### Claim 3 (depends on 1) The method of claim 1, after completing e), automatically adjusting the laser assembly relative to the reference surface so that the detected power level of the return reflected beam is maintained at the minimized power level. ### Claim 4 (depends on 1) The method of claim 1, after completing e), determining a magnitude of a deflection of the reference surface relative to the laser assembly. ### Claim 5 (depends on 1) The method of claim 1, wherein the power detector is connected to a digital readout device, and displaying on the digital readout device the power level detected by the power detector and positional deviation of the return reflected beam from the laser beam in a two-dimensional coordinate system established by the power detector. ### Claim 6 (depends on 5) The method of claim 5, wherein the two-dimensional coordinate system comprises a y-axis displacement and an x-axis displacement relative to an origin. ### Claim 7 A method of aligning a laser transmitter with a reference surface, comprising: directing a laser beam from the laser transmitter through a beam splitter and onto the reference surface; using a power detector, detecting a power level of a return reflected beam resulting from the laser beam impacting on the reference surface; and adjusting the laser transmitter and the reference surface relative to one another to cause the return reflected beam to interfere with the laser beam transmitted from the laser transmitter and until the detected power level of the return reflected beam reaches a minimized power level. ### Claim 8 (depends on 7) The method of claim 7, comprising adjusting the orientation of the laser transmitter relative to the reference surface. ### Claim 9 (depends on 8) The method of claim 8, comprising adjusting the orientation of the beam splitter and the power detector in unison with adjusting the orientation of the laser transmitter. ### Claim 10 (depends on 8) The method of claim 8, comprising automatically adjusting the orientation of the laser transmitter relative to the reference surface so that the power level of the return reflected laser beam is maintained at the minimized power level. ### Claim 11 (depends on 7) The method of claim 7, further comprising determining a magnitude of a deflection of the reference surface relative to the laser assembly. ### Claim 12 (depends on 7) The method of claim 7, wherein the power detector is connected to a digital readout device, and displaying on the digital readout device the power level detected by the power detector and positional deviation of the return reflected beam from the laser beam in a two-dimensional coordinate system established by the power detector. ### Claim 13 (depends on 12) The method of claim 12, wherein the two-dimensional coordinate system comprises a y-axis displacement and an x-axis displacement relative to an origin.