Systems and methods for selecting light emitters for emitting light

Patent metadata

Field	Value
Publication number	US-10797698-B1
Application number	US-201916699438-A
Country	US
Kind code	B1
Filing date	Nov 29, 2019
Priority date	Nov 29, 2019
Publication date	Oct 6, 2020
Grant date	Oct 6, 2020

Abstract

An example circuit includes a plurality of light emitters connected in parallel between a first node and a second node. The circuit also includes a plurality of capacitors, with each capacitor corresponding to one of the light emitters, and a plurality of discharge-control switches, with each discharge-control switches corresponding to one of the capacitors. The circuit further includes a pulse-control switch connected to the plurality of light emitters. During a first period, the pulse-control switch restricts current flow, and each of the plurality of capacitors is charged via the first node. During a second period, one or more of the plurality of discharge-control switches allows current flow that discharges one or more corresponding capacitors. During a third period, the pulse-control switch allows current flow that discharges one or more undischarged capacitors of the plurality of capacitors through one or more corresponding light emitters.

First claim

What is claimed is:

1. A circuit comprising:
a plurality of light emitters connected between a first node and a second node;
a plurality of capacitors, wherein each capacitor in the plurality of capacitors corresponds to a respective light emitter in the plurality of light emitters;
a plurality of discharge-control switches, wherein each discharge-control switch corresponds to a respective capacitor in the plurality of capacitors; and
a pulse-control switch connected to the plurality of light emitters,
wherein, during a first period, the pulse-control switch restricts current flow and each capacitor in the plurality of capacitors is charged via the first node,
wherein, during a second period, one or more of the plurality of discharge-control switches allows current flow that discharges one or more corresponding capacitors of the plurality of capacitors, and
wherein, during a third period, the pulse-control switch allows current flow that discharges one or more undischarged capacitors of the plurality of capacitors through one or more corresponding light emitters of the plurality of light emitters, thereby causing the one or more corresponding light emitters to emit respective pulses of light.

2. The circuit of claim 1 , wherein the pulse-control switch comprises a field-effect transistor.

3. The circuit of claim 1 , wherein the plurality of light emitters comprises a plurality of laser diodes sharing a common cathode, and wherein the common cathode is connected to the pulse-control switch at the second node.

4. The circuit of claim 1 , further comprising a shift register configured to select individual capacitors from the plurality of capacitors, via corresponding discharge-control switches in the plurality of discharge-control switches, for discharging.

5. The circuit of claim 4 , wherein the shift register is configured to receive a digital input comprising a plurality of bits, wherein each bit in the plurality of bits indicates whether a corresponding capacitor in the plurality of capacitors is discharged or undischarged during the second period.

6. The circuit of claim 1 , further comprising a plurality of diodes connected between the first node and the plurality of capacitors, wherein each capacitor of the plurality of capacitors is charged via a corresponding diode of the plurality of diodes.

7. The circuit of claim 1 , further comprising a driver circuit connected to the pulse-control switch and configured to bias the pulse-control switch to allow current flow during the third period.

8. The circuit of claim 1 , wherein the first period, the second period, and the third period, occur within a repeating pulse period associated with the plurality of light emitters.

9. The circuit of claim 1 , further comprising a single inductor connected to the first node, wherein the single inductor is configured to charge the plurality of capacitors during the first period.

10. The circuit of claim 1 , further comprising an adjustable voltage source connected to the first node, wherein the plurality of capacitors are charged during the first period in accordance with a voltage level of the adjustable voltage source, and wherein the respective pulses of light emitted during the third period have a peak power level that is based on the voltage level.

11. A method comprising:
during a first period,
(i) using a pulse-control switch to restrict current flow through a plurality of light emitters, and
(ii) charging a plurality of capacitors via a first node;

during a second period,
using one or more discharge-control switches to allow current flow that discharges one or more corresponding capacitors of the plurality of capacitors; and

during a third period,
using the pulse-control switch to allow current flow and thereby discharge one or more undischarged capacitors of the plurality of capacitors through one or more corresponding light emitters of the plurality of light emitters, thereby causing the one or more corresponding light emitters to emit respective pulses of light.

12. The method of claim 11 , further comprising:
determining a portion of an environment to illuminate using the light emitters and a remaining portion; and
determining one or more light emitters corresponding to the remaining portion of the environment at an emission time,
wherein using the one or more discharge-control switches to allow current flow and thereby discharge the one or more of the plurality of capacitors comprises using the one or more discharge-control switches to allow current flow and thereby discharge the one or more light emitters corresponding to the remaining portion of the environment.

13. The method of claim 12 , wherein determining the portion of an environment to illuminate using the light emitters and the remaining portion comprises:
emitting light using the light emitters during a first scan of the environment;
receiving reflected portions of the emitted light corresponding to the first scan;
determining, based on the received reflected portions of emitted light, not to emit light towards the remaining portion of the environment during a second scan of the environment.

14. The method of claim 13 , further comprising:
identifying, based on the received reflected portions of emitted light, a type of object in the environment,
wherein determining not to emit light towards the remaining portion of the environment during a second scan of the environment comprises determining not to emit light towards the type of object in the environment.

15. The method of claim 14 , wherein the type of object is a retroreflector.

16. The method of claim 11 , wherein the one or more discharge-control switches correspond to outputs from a shift register, and
wherein using the one or more discharge-control switches to allow current flow and thereby discharge one or more of the plurality of capacitors, comprises using a plurality of bits input into the shift register to designate which of the plurality of capacitors is discharged during the second period and which of the plurality of capacitors are undischarged during the second period.

17. The method of claim 11 , wherein the method is implemented using a LIDAR device, the method further comprising:
determining an expected change in pose of the LIDAR device from a first scan of the LIDAR device to a second scan of the LIDAR device,
wherein using the one or more discharge-control switches to allow current flow and thereby discharge one or more of the plurality of capacitors, comprises:
selecting the one or more of the plurality of capacitors for discharging based on the expected change in pose of the LIDAR device from the first scan of the LIDAR device to the second scan of the LIDAR device.

18. The method of claim 11 , wherein the first period, the second period, and the third period are comprised within a first pulse period of a plurality of repeating pulse periods associated with the plurality of light emitters, the method further comprising:
during a second pulse period of the plurality of pulse periods;
during the first period of the second pulse period,
(i) using the pulse-control switch to restrict current flow through a plurality of light emitters, and
(ii) charging the plurality of capacitors via a first node;

during the second period of the second pulse period,
using the one or more discharge-control switches to allow current flow that discharges one or more different capacitors of the plurality of capacitors; and

during the third period of the second pulse period,
using the pulse-control s

Assignees

• Waymo Llc

Inventors

• Droz Pierre-Yves
• Tazzoli Augusto
• Marx Michael

Classifications

• Y02B20/40

  Control techniques providing energy savings, e.g. smart controller or presence detection · CPC title

• H05B45/00

  Circuit arrangements for operating light-emitting diodes [LED] · CPC title

• H05B47/115 Primary

  by determining the presence or movement of objects or living beings · CPC title

• H03K17/04123

  in field-effect transistor switches · CPC title

• H03K17/969 Primary

  having a plurality of control members, e.g. keyboard · CPC title