Camera-style lidar setup

• US 20100165322A1
• Filed: 12/29/2008
• Published: 07/01/2010
• Est. Priority Date: 06/27/2006
• Status: Active Grant

• Current Assignee: Arete Associates
• Original Assignee: Arete Associates
• Inventors: Daiker, Jeff T., Murray, James T., Kane, David M.
• Granted Patent: US 8,958,057 B2
• Time in Patent Office: Days
• US Class Current: 356/4.10
• CPC Class Codes: G01S 17/42 Simultaneous measurement of distance and other co-ordinates indirect measurement G01S17/46
• CPC Class Codes: G01S 7/481 Constructional features, e.g. arrangements of optical elements

Abstract

Separate reception/transmission apertures enhance pointing: reception is more efficient than transmission (kept smaller for MEMS steering). Apparatus aspects of the invention include lidar transmitters emitting laser beams, and scan mirrors (or assemblies) angularly adjustable to deflect the beams in orthogonal directions. In one aspect, afocal optics magnify deflection; a transmitter aperture transmits the beam; a lidar receiver doesn'"'"'t share the transmitter aperture. In another aspect, auxiliary optics calibrate the deflection.

A method aspect of the invention notices and responds to a remote source—using a similar local laser, adjustable scan mirror or assembly, afocal deflection magnifier, transmission aperture and separate receiver. Method steps include operating the receiver to notice and determine location of the remote source; and controlling the transmitter to direct laser light back toward that location.

Among preferences: receiver aperture exceeds five times transmitter aperture; receiver is segmented; beam expander between laser and mirror(s) controls waist or divergence, for selecting Gaussian or Rayleigh divergence and “zoom”.

Claims

1. A lidar apparatus comprising:

a lidar transmitter that includes a laser source that produces a laser beam, a scan mirror or scan-mirror assembly angularly adjustable to deflect the beam in at least two orthogonal directions, and an afocal optical unit for magnifying the beam deflection;

said transmitter having an aperture for transmitting the beam; and

a lidar receiver that does not share the transmitter aperture;

wherein;

the receiver comprises plural separate discrete receiver modules, each having an aperture whose area is individually smaller than the area of the transmitter aperture, and each being either;

a CCD array, or

an individual photodetector not integrated with other photodetectors into an array; and

aggregate aperture area of the plural receiver modules is larger than the area of the transmitter aperture.

2. The apparatus of claim 1, further comprising:

a beam expander, disposed between the laser and the mirror or mirrors, for controlling the beam waist or divergence, or both, particularly at the mirror or mirrors; and

wherein;

means for effectively providing a “

zoom”

function;

wherein the effectively-providing means in turn comprise;

means for causing the expander to be adjustable, and

means, controlled by adjusting the expander, for enabling selection of Gaussian or Rayleigh divergence.

3. The apparatus of claim 1, further comprising:

an auxiliary optical system for calibrating the deflection produced by the mirror or mirror assembly;

wherein;

the laser beam follows a particular optical path at the mirror or mirrors; and

the auxiliary optical system comprises;

means for causing an auxiliary radiation beam to follow, at the mirror or mirrors, an optical path identical or similar to the particular path, and

means for monitoring deflection of the auxiliary beam by the mirror or mirrors; and

the causing means comprise a beamsplitter for at least roughly aligning the auxiliary beam with the laser beam in approaching the mirror or mirrors.

4. The apparatus of claim 3, further comprising:

means for separating the auxiliary beam from the laser beam after leaving the mirror or mirrors;

an auxiliary detector for determining deflection of the separated auxiliary beam by the mirror or mirrors; and

means for correlating the determined deflection with control signals that operate the mirror or mirrors; and

wherein;

the separating means comprise means for passing the auxiliary beam through the same beamsplitter again or through another beamsplitter.

5. The apparatus of claim 4, wherein:

the auxiliary detector is a position-sensing detector (“

PSD”

).

6. The apparatus of claim 3, wherein:

the beamsplitter is wavelength sensitive; and

the auxiliary beam and laser beam are of different wavelengths; and

the beamsplitter is a dichroic element or holographic element.

7. The apparatus of claim 3, further comprising:

means for at least roughly synchronizing pulses of the laser beam with sensitive times or dispositions, or both, of the receiver.

8. The apparatus of claim 1, further comprising one or both of:

calculating means for determining time delay between transmission of a pulse of the laser beam and receipt of a reflected return of the pulse from an object; and

comparison means for determining Doppler shift in the laser beam; and

wherein the calculating or comparison means further comprise, respectively;

means for calculating object distance from the determined time delay, or

means for deriving relative speed from the shift; and

further comprising means for incorporating information about the apparatus orientation or location, or both, together with information that the apparatus has noticed a return from an object, or distance of such an object, or both.

9. The apparatus of claim 1, wherein:

the receiver has a detector of particular overall dimensions, and is controlled actively to select operation as either;

a single unit having said particular overall dimensions, or

multiple subsections of the detector, each having dimensions smaller than said particular overall dimensions; and

a sampled region is selected based on knowledge of where the scan mirror is pointing the laser beam, to facilitate sampling of smaller units.

10. The apparatus of claim 1, further comprising:

means for measuring the angles of beam deflection by the scan mirror or mirror assembly;

said measuring means comprising a capacitive sensor responsive to an individual mirror or mirrors.

11. The apparatus of claim 1, further comprising:

means for measuring the angles of beam deflection by the scan mirror or mirror assembly;

said measuring means comprising a magnetic sensor responsive to an individual mirror or mirrors.

12. The apparatus of claim 1, further comprising:

means for measuring the angles of beam deflection by the scan mirror or mirror assembly;

said measuring means comprising a lookup table calibrated in drive voltage or current supplied to an individual mirror or mirrors.

13. A method for noticing and responding to a remote light source, said method utilizing a transmitter which includes a local radiation source that produces a laser beam, a scan mirror or scan-mirror assembly angularly adjustable to deflect the beam in at least two orthogonal directions, and an afocal optical unit for magnifying the beam deflection, said transmitter having an aperture for transmitting the beam;

and a radiation receiver that does not share the transmitter aperture;

said method comprising the steps of;

operating the receiver to notice and determine a location of the remote source; and

controlling the transmitter to direct the laser beam back toward the determined location.

14. The method of claim 13, further comprising the step of:

activating the receiver to collect and interpret reflected radiation of the back-directed laser beam, received from the location.

15. The method of claim 13, further utilizing an additional receiver;

and further comprising the steps of;

activating the additional receiver to collect and interpret reflected radiation of the back-directed laser beam, received from the location.

16. The method of claim 15, wherein:

the first-mentioned receiver and the additional receiver are sensitive in respective different wavelength bands, namely;

a first spectral waveband encompassing emissions of expected remote sources including but not necessarily limited to said remote light source; and

a second spectral waveband encompassing said laser beam.

17. The method of claim 15, wherein:

the activating step comprises using the additional receiver in a lidar operating mode to determine return time of the laser beam and thereby distance of a reflecting object at the location.

18. The method of claim 13, wherein the operating step comprises:

fitting the centroid of an incoming radiation pattern to an expected shape, when the laser-beam divergence exceeds the per-pixel FOV.