Systems, devices, and methods for focusing laser projectors

• US 10,365,550 B2
• Filed: 12/11/2017
• Issued: 07/30/2019
• Est. Priority Date: 04/13/2016
• Status: Active Grant

• Current Assignee: Google LLC (Alphabet Inc.)
• Original Assignee: North Inc.
• Inventors: Holland, Lloyd Frederick, Morrison, Vance R.
• Primary Examiner(s): Carruth, Jennifer D.
• Application Number:
  US15/837,264
• Publication Number:
  US 20180107103A1
• Time in Patent Office: 596 Days
• CPC Class Codes: G02B 2027/0174 holographic
• CPC Class Codes: G02B 2027/0178 Eyeglass type eyeglass details G02C
• CPC Class Codes: G02B 26/10 Scanning systems
• CPC Class Codes: G02B 27/0172 characterised by optical features
• CPC Class Codes: G02B 27/106 for splitting or combining a plurality of identical beams or images, e.g. image replication
• CPC Class Codes: G02B 27/14 operating by reflection only
• CPC Class Codes: G02B 27/146 with a tree or branched structure
• CPC Class Codes: G02B 27/30 Collimators
• CPC Class Codes: G02C 11/10 Electronic devices other than hearing aids
• CPC Class Codes: G03B 21/2033 LED or laser light sources
• CPC Class Codes: G03B 21/62 Translucent screens
• CPC Class Codes: H01S 5/005 Optical components external to the laser cavity, specially adapted therefor, e.g. for homogenisation or merging of the beams or for manipulating laser pulses, e.g. pulse shaping H01S5/026, H01S5/18388 take precedence
• CPC Class Codes: H01S 5/0071 for beam steering, e.g. using a mirror outside the cavity to change the beam direction
• CPC Class Codes: H01S 5/02 Structural details or components not essential to laser action
• CPC Class Codes: H01S 5/02212 Can-type, e.g. TO-CAN housings with emission along or parallel to symmetry axis
• CPC Class Codes: H01S 5/4012 Beam combining, e.g. by the use of fibres, gratings, polarisers, prisms
• CPC Class Codes: H01S 5/4087 emitting more than one wavelength
• CPC Class Codes: H01S 5/4093 Red, green and blue [RGB] generated directly by laser action or by a combination of laser action with nonlinear frequency conversion

Abstract

Systems, devices, and methods for focusing laser projectors are described. A laser projector includes N≥1 laser diodes, each of which emits laser light having a divergence. Each laser diode is paired with a respective primary or collimation lens to at least reduce a divergence of the laser light that the laser diode produces. Downstream from the primary lens(es) in the optical path(s) of the laser light, a single dedicated secondary or convergence lens converges the laser light to a focus. By initiating the convergence of the laser light at the secondary or convergence lens as opposed to at the primary or collimation lens(es), numerous benefits that are particularly advantageous in laser projection-based wearable heads-up displays are realized.

Claims

1. A method of focusing a laser light provided by a laser projector, wherein the laser projector includes a laser module having at least one laser diode, the method comprising:

providing the laser light by the laser module of the laser projector, wherein the laser light has a divergence;

at least reducing the divergence of the laser light by at least one collimation lens;

converging the laser light to a focus by a convergence lens positioned downstream from the at least one collimation lens in an optical path of the laser light, wherein the focus is positioned outside of the laser projector; and

receiving the laser light by at least one scan mirror positioned in the optical path of the laser light in between the convergence lens and the focus of the laser light, wherein a spot size of the laser light at the at least one scan mirror is greater than a spot size of the laser light at the focus of the laser light.

2. The method of claim 1 wherein:

the laser module of the laser projector includes N laser diodes, where N≥

1, and providing the laser light by the laser module of the laser projector includes providing a respective laser light by each respective one of the N laser diodes, each respective laser light having a divergence; and

the at least one collimation lens includes N collimation lenses and at least reducing the divergence of the laser light by at least one collimation lens includes at least reducing the divergence of each respective laser light by a respective one of N collimation lenses.

3. The method of claim 2, further comprising:

combining each respective laser light from the N laser diodes into an aggregate laser light, and wherein converging the laser light to a focus by a convergence lens includes converging the aggregate laser light to the focus by the convergence lens.

4. The method of claim 1 wherein at least reducing the divergence of the laser light by at least one collimation lens includes collimating the laser light by at least one collimation lens.

5. The method of claim 1, further comprising controllably rotating a reflective area of the at least one scan mirror about a first axis.

6. The method of claim 5 wherein receiving the laser light by at least one scan mirror positioned in the optical path of the laser light in between the convergence lens and the focus of the laser light, wherein a spot size of the laser light at the at least one scan mirror is greater than a spot size of the laser light at the focus of the laser light includes receiving the laser light by the reflective area of the at least one scan mirror, wherein a dimension of the spot size of the laser light at the reflective area of the at least one scan mirror is less than or equal to a dimension of the reflective area of the at least one scan mirror along the first axis.