Compressive scanning lidar

Patent metadata

Field	Value
Publication number	US-9575162-B2
Application number	US-201414317753-A
Country	US
Kind code	B2
Filing date	Jun 27, 2014
Priority date	Jun 27, 2014
Publication date	Feb 21, 2017
Grant date	Feb 21, 2017

Abstract

A method for increasing resolution of an image formed of received light from an illuminated spot includes measuring a y vector for measurement kernels A 1 to A M , where M is a number of the measurement kernels, measuring the y vector including programming a programmable N-pixel micromirror or mask located in a return path of a received reflected scene spot with a jth measurement kernel A j of the measurement kernels A 1 to A M , measuring y, wherein y is an inner product of a scene reflectivity f(α,β) with the measurement kernel A j for each range bin r i , wherein α and β are azimuth and elevation angles, respectively, repeating programming the programmable N-pixel micromirror or mask and measuring y for each measurement kernel A 1 to A M , and forming a reconstructed image using the measured y vector, wherein forming the reconstructed image includes using compressive sensing or Moore-Penrose reconstruction.

First claim

What is claimed is:

1. A method for increasing resolution of an image formed of received light from an illuminated spot comprising:
measuring a y vector for measurement kernels A 1 to A M , where M is a number of the measurement kernels, measuring the y vector comprising:
programming a programmable N-pixel micromirror or mask located in a return path of a received reflected scene spot with a jth measurement kernel A j of the measurement kernels A 1 to A M ;
measuring y, wherein y is an inner product of a scene reflectivity f(α,β) with the measurement kernel A j for each range bin r i , wherein α and β are azimuth and elevation angles, respectively;
repeating programming the programmable N-pixel micromirror or mask and measuring y for each measurement kernel A 1 to A M ; and

forming a reconstructed image using the measured y vector, wherein forming the reconstructed image comprises using compressive sensing or Moore-Penrose reconstruction.

2. The method of claim 1 wherein measuring y comprises:
illuminating the spot using a light source with frequency modulation continuous wave (FMCW) modulation;
using FMCW coherent detection; and
using Fourier analysis.

3. The method of claim 1 wherein forming a reconstructed image comprises:
using compressive sensing if M is less than N, and if θ is sufficiently sparse to reconstruct f using an L 1 norm:

θ
^

=

arg
⁢

⁢
min

θ

⁢

(



y
-

AD
⁢

⁢
θ



2
2

+

α
⁢


θ


1

)

f
^

=

D
⁢

⁢
θ

^

;

wherein D comprises a dictionary D and θ comprise corresponding coefficients.

4. The method of claim 1 wherein forming a reconstructed image comprises:
if M is greater than or equal to N, using a Moore-Penrose inverse of matrix A to reconstruct f
{circumflex over (f)}=A + y
where
A + =( A H A ) −1 A H .

5. The method of claim 1 wherein the illuminated spot is illuminated by a scanning laser and wherein the method further comprises:
scanning the laser; and
repeating forming the reconstructed image for each spot illuminated by the laser;
wherein measuring y further comprises:
emitting a laser beam having triangular frequency modulation continuous wave (FMCW) from the scanning laser;
mixing a portion of the emitted laser beam with the received light at a photodiode detector for coherent detection;
wherein the scanning laser comprises a scanning micromirror; and
wherein the programmable N-pixel micromirror is synchronized with the scanning micromirror to maintain the received light focused on a photodiode detector.

6. The method of claim 1 further comprising:
illuminating the illuminated spot using a laser; and
detecting the received light using a photodiode detector;
wherein a photodiode output current is
i ( t )= S (Φ lo +yΦ o +2√{square root over ( yΦ lo Φ o )} cos(ω b t +φ))+ i b

where y is an inner product of the scene reflectivity f(α,β) with a measurement kernel A j , Φ o is an output laser power, Φ lo is an local oscillator power, ω b is a beat between the laser and the received light, φ is a phase difference between the laser and the return light, S is a diode responsivity, i b is a diode bias current, and t is time.

7. The method of claim 2 further comprising:
determining parameters for target components of the illuminated spot, including a range R a , a range uncertainty ΔR a , and a velocity v t for each target component using equations

f
R

=

f
1

+

f
2

2

=

4
⁢

R
a

⁢
Δ
⁢

⁢
f

cT
mod

f
D

=

f
2

-

f
1

2

=

2
⁢

v
t

λ

Δ
⁢

⁢

R
a

=

c

2
⁢
Δ
⁢

⁢
f

Assignees

• Hrl Lab Llc
• Hrl Lab Llc

Inventors

• Owechko Yuri

Classifications

• G01S7/4808

  Evaluating distance, position or velocity data · CPC title

• G01S17/34

  using transmission of continuous, frequency-modulated waves while heterodyning the received signal, or a signal derived therefrom, with a locally-generated signal related to the contemporaneously transmitted signal · CPC title

• G01S7/4817 Primary

  relating to scanning · CPC title

• G01S17/89

  for mapping or imaging · CPC title

• H01S5/0262

  Photo-diodes, e.g. transceiver devices, bidirectional devices (H01S5/0265 takes precedence) · CPC title