Systems, devices, and methods for focusing laser projectors

• US 10,365,548 B2
• Filed: 04/13/2017
• 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:
  US15/487,232
• Publication Number:
  US 20170299956A1
• Time in Patent Office: 838 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 laser projector comprising:

a laser module to provide laser light, the laser module comprising;

a first laser diode to provide a first laser light, wherein the laser light provided by the laser module includes at least the first laser light; and

a first collimation lens positioned in an optical path of the first laser light, the first collimation lens to receive the first laser light and at least reduce a divergence of the first laser light;

a convergence lens positioned downstream from the laser module in an optical path of the laser light, the convergence lens to receive the laser light from the laser module and converge the laser light to a focus outside of the projector; and

a first 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 first scan mirror is greater than a spot size of the laser light at the focus of the laser light, and wherein the first scan mirror includes a two dimensional reflective area and the spot size of the laser light at the first scan mirror is less than or equal to the reflective area of the first scan mirror.

2. The laser projector of claim 1 wherein the reflective area of the first scan mirror is controllably rotatable about a first axis and a dimension of the spot size of the laser light at the reflective area of the first scan mirror is less than or equal to a dimension of the reflective area of the first scan mirror along the first axis.

3. The laser projector of claim 2, further comprising:

a second scan mirror positioned in the optical path of the laser light in between the first scan mirror and the focus of the laser light, wherein;

the second scan mirror includes a two dimensional reflective area;

the reflective area of the second scan mirror is controllably rotatable about a second axis that is orthogonal to the first axis of the reflective area of the first scan mirror; and

a dimension of the spot size of the laser light at the reflective area of the second scan mirror is less than or equal to a dimension of the reflective area of the second scan mirror along the second axis.

4. The laser projector of claim 1 wherein the laser module further comprises:

a second laser diode to provide a second laser light, wherein the laser light provided by the laser module includes the second laser light; and

a second collimation lens positioned in an optical path of the second laser light, the second collimation lens to receive the second laser light and at least reduce a divergence of the second laser light.

5. The laser projector of claim 4 wherein a wavelength of the first laser light is different from a wavelength of the second laser light.

6. The laser projector of claim 4 wherein the laser module further comprises:

at least a third laser diode to provide at least a third laser light, wherein the laser light provided by the laser module includes the at least a third laser light; and

at least a third collimation lens positioned in an optical path of the at least a third laser light, the at least a third collimation lens to receive the at least a third laser light and at least reduce a divergence of the at least a third laser light.

7. The laser projector of claim 4, further comprising:

a combiner positioned and oriented to receive the first laser light and the second laser light and to combine the first laser light and the second laser light into the laser light.

8. The laser projector of claim 7 wherein a wavelength of the first laser light is different from a wavelength of the second laser light, and wherein the combiner comprises:

a first mirror formed of a material that is reflective of the first laser light, the first mirror positioned in the optical path of the first laser light and oriented to redirect the first laser light towards the convergence lens; and

a second mirror formed of a dichroic material that is reflective of the first laser light and transmissive of the second laser light, the second mirror positioned in the optical path of the first laser light in between the first mirror and the convergence lens, and the second mirror also positioned in the optical path of the second laser light and oriented to;

redirect the second laser light towards the convergence lens, and

combine the optical path of the second laser light with the optical path of the first laser light for a portion of the optical path of the first laser light that is downstream from the second mirror.

9. A laser projector comprising:

a set of N laser diodes, where N≥

1, each laser diode in the set of N laser diodes to provide a respective laser light having a divergence;

a set of N primary lenses, each primary lens in the set of N primary lenses positioned and oriented to receive a respective laser light from a respective one of the N laser diodes and each primary lens in the set of N primary lenses positioned and oriented to at least reduce the divergence of a respective laser light from a respective one of the N laser diodes;

a combiner positioned and oriented to receive each respective laser light having at least reduced divergence from each respective one of the N primary lenses and combine each respective laser light having at least reduced divergence from each respective one of the N primary lenses into an aggregate laser light;

a secondary lens positioned and oriented to receive the aggregate laser light from the combiner and converge the aggregate laser light to a focus outside of the laser projector; and

a first scan mirror positioned and oriented to receive the aggregate laser light from the secondary lens, wherein a spot size of the aggregate laser light at the first scan mirror is greater than a spot size of the aggregate laser light at the focus of the aggregate laser light, and wherein the first scan mirror includes a two dimensional reflective area and the spot size of the aggregate laser light at the first scan mirror is less than or equal to the reflective area of the first scan mirror.

10. The laser projector of claim 9 wherein the reflective area of the first scan mirror is controllably rotatable about a first axis and a dimension of the spot size of the aggregate laser light at the reflective area of the first scan mirror is less than or equal to a dimension of the reflective area of the first scan mirror along the first axis.

11. The laser projector of claim 10, further comprising:

a second scan mirror positioned and oriented to receive the aggregate laser light from the first scan mirror, wherein;

the second scan mirror includes a two dimensional reflective area;

the reflective area of the second scan mirror is controllably rotatable about a second axis that is orthogonal to the first axis of the reflective area of the first scan mirror; and

a dimension of the spot size of the aggregate laser light at the reflective area of the second scan mirror is less than or equal to a dimension of the reflective area of the second scan mirror along the second axis.

12. The laser projector of claim 9 wherein the set of N laser diodes includes a first laser diode to provide laser light of a first wavelength and at least a second laser diode to provide laser light of at least a second wavelength.