# US 5,926,281 A · Device to measure the alignment of a laser amplification system

> Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt

- Number: US 5,926,281 A
- Document ID: US5926281A
- Status: Granted
- Kind: A
- Application number: 08/893,180
- Filed: 1997-07-15
- Granted: 1999-07-20
- Earliest claimed: 1996-07-23
- Assignees: Thomas-CSF
- Inventors: Jacques Rioland; Michel Delon; Fran.cedilla.ois-Hugues Gauthier; Patrice Jano
- Web page: https://patentgrep.com/patent/US5926281A

## CPC

- H01S 3/2341: {Four pass amplifiers}
- 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)}
- H01S 3/005: {Optical devices external to the laser cavity, specially adapted for lasers, e.g. for homogenisation of the beam or for manipulating laser pulses, e.g. pulse shaping (shaping laser beam for working metal or other materials B23K26/06; optical elements, systems or apparatus in general G02B)}
- H01S 3/2316: {Cascaded amplifiers}
- 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 device for the alignment of a laser beam amplification system comprises at least measuring means and alignment templates positioned instead of filtering hole plates of the amplification system, the alignment templates having holes whose centers have substantially the same spatial positions as the centers of the filtering holes, certain template holes being provided with reference sights offset in an angular way with respect to one another, the tips of these sights being pointed towards the center of the holes, the measuring means defining, by sighting at the end of the amplification system, the divergences between the focusing points of the beam in the holes, merged at a single point, and the tips of the sights, their angular positions enabling them to be assigned to their respective holes, the positions of elements of the amplification system being then controlled as a function of the measurements of divergences. Application to the automating setting of alignment, especially in the case of large numbers of parallel amplification systems.

## Claims

### Claim 1

A device to measure the alignment of a laser beam amplification system including removable filtering hole plates defining filtering holes, comprising:
alignment templates positioned at locations corresponding to locations of removed filtering hole plates of the amplification system, the alignment templates having template holes whose centers have substantially the same spatial positions as centers of the filtering holes, a plurality of said template holes being provided with reference sights offset in an angular way with respect to one another, tips of said reference sights being pointed towards the center of the template holes,
at least one measuring device configured to measure, at an end of the amplification system, divergences between focusing points of the laser beam in the template holes, merged at a single point at a location of the measuring device, and the tips of the reference sights, and
a control device configured to control elements of the amplification system based the divergences measured by the measuring device;
wherein angular positions of said reference sights enable the reference sights to be assigned to their respective template holes.

### Claim 2 (depends on 1)

A device according to claim 1, wherein:
the amplification system is modelled by a linear system of n equations, the total number of reference sights being equal to n, and the measurement device performing n measurements of divergence.

### Claim 3 (depends on 1)

A device according to claim 1, wherein the measurement device comprises:
a camera configured to observe the laser beam at a last focusing point,
a semi-reflecting plate configured to reflect the laser beam at an output of the amplification system, and
a spherical mirror configured to reflect the laser beam reflected from the semi-reflecting plate and to focus the laser beam onto the camera at the last focusing point.

### Claim 4 (depends on 1)

A device according to claim 1, further comprising:
reticles placed in planes of pupils of the amplification system, and
a camera configured to display positions of the pupils of the amplification system, the camera having an optical system focused at infinity and placed in a position facing a last focusing point of the amplification system,
wherein the display by the camera of the pupils positions enables a centering of the pupils.

### Claim 5 (depends on 4)

A device according to claim 4, further comprising:
a semi-reflecting mirror configured to reflect the laser beam at an output of the amplification system,
a spherical mirror configured to reflect the laser beam reflected from said semi-reflecting mirror, and
a lens configured to focus the laser beam reflected from the spherical mirror and onto the camera.

### Claim 6 (depends on 1)

A device according to claim 1, further comprising:
a semi-reflecting plate positioned at an output of the amplification system and configured to reflect at least part of the laser beam, and
a spherical mirror configured to focus the beam reflected from said semi-reflecting plate onto infrared detectors,
wherein the infrared detectors are configured to identify a direction of an optical axes of the laser beam so as to orient by self-collimation an angle at which the laser beam enters at least one of a plurality of conversion crystals included in the amplification system.

### Claim 7

A method of controlling an alignment of a laser beam amplification system having removable filtering hole plates defining filtering holes, comprising the steps of:
placing alignment templates having template holes so that each center of said template holes is positioned at substantially a same spatial position as a center of the filtering holes defined by the removed filtering hole plates;
providing reference sights to said template holes, said reference sights being offset in an angular way with respect to one another;
illuminating said alignment templates with the laser beam;
measuring divergences between focusing points of the laser beam in the template holes and tips of the reference sights;
assigning the reference sights to their respective template holes using the reference sights angular offsets; and
controlling positions of elements of the amplification system as a function of measurements of divergences performed in the measuring step.

### Claim 8 (depends on 7)

The method according to claim 7, further comprising:
modeling the amplification system with a linear system of n equations;
repeating the measuring step n times so as to obtain n measurements of divergence; and
solving the linear system of n equations based on said n measurements.

### Claim 9 (depends on 7)

A method according to claim 7, further comprising:
focusing at infinity an optical system of a camera; and
placing the optical system in a position facing a last focusing point on the amplification system;
centering pupils of the amplification system based on information received by the optical system.