Speckle reduction within nanosecond-order pulse widths for flash - - PowerPoint PPT Presentation

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Mar 24, 2023 275 likes •643 views

Speckle reduction within nanosecond-order pulse widths for flash lidar applications Fergal Shevlin, Ph.D. DYOPTYKA, Ireland. Laser Display and Lighting Conference 2020 Yokohama, Japan. 2020-04-21 1 / 18 Direct time-of-flight systems Dark

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Speckle reduction within nanosecond-order pulse widths for flash lidar applications

Fergal Shevlin, Ph.D. DYOPTYKA, Ireland.

Laser Display and Lighting Conference 2020 Yokohama, Japan.

2020-04-21

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SLIDE 2

Direct time-of-flight systems

Dark speckle causes non-detection of Rx pulse at some pixels.

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SLIDE 3

VCSEL array sources

Array dimensions similar to camera pupil diameter.

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SLIDE 4

Speckle with insufficient angular separation of sources

Single 22 ns pulse image, CS ≈ 24%. Mean of 100 different 22 ns pulse images, CS ≈ 24%.

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SLIDE 5

Speckle with insufficient angular separation of sources

Single 14 ns pulse image, CS ≈ 24%. Mean of 100 different 14 ns pulse images, CS ≈ 24%.

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SLIDE 6

Speckle with insufficient angular separation of sources

Single 6 ns pulse image, CS ≈ 20%. Mean of 100 different 6 ns pulse images, CS ≈ 20%.

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SLIDE 7

Speckle with insufficient angular separation of sources

CS for 100 different pulse images of each duration.

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SLIDE 8

Alternative source configuration

Source separation greater than camera pupil diameter.

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SLIDE 9

Speckle with sufficient angular separation of sources

Different 22 ns pulse images, CS ≈ 24%. Mean of 100 different 22 ns pulse images, CS ≈ 3%.

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SLIDE 10

Speckle with sufficient angular separation of sources

Different 14 ns pulse images, CS ≈ 24%. Mean of 100 different 14 ns pulse images, CS ≈ 4%.

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SLIDE 11

Speckle with sufficient angular separation of sources

Different 6 ns pulse images, CS ≈ 20%. Mean of 100 different 6 ns pulse images, CS ≈ 3%.

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SLIDE 12

Speckle reduction within single pulse durations

Randomize TX pulse wavefronts so that RX wavefronts less correlated.

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SLIDE 13

Speckle reduction within single pulse durations

Randomize TX pulse wavefronts so that RX wavefronts less correlated. RX pulse wavefronts highly correlated to rough surface.

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SLIDE 14

DYOPTYKA deformable mirror

Randomly-distributed surface deformations at frequencies up to tens of MHz.

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SLIDE 15

DYOPTYKA deformable mirror

Randomly-distributed surface deformations at frequencies up to tens of MHz. Microscope interferometer fringes resulting from convex and concave surface deformations.

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SLIDE 16

Apparatus configuration #1

LD, DM, BP.

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SLIDE 17

Apparatus configuration #1

LD, DM, BP. LD emission, DM inactive.

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SLIDE 18

Apparatus configuration #1

LD, DM, BP. LD emission, DM inactive. LD 6 ns pulse, DM active.

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SLIDE 19

Apparatus configuration #1

LD, DM, BP. LD emission, DM inactive. LD 6 ns pulse, DM active. LD 6 ns pulse, DM active.

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SLIDE 20

Apparatus configuration #2

LD, DM, ED, BP.

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SLIDE 21

Apparatus configuration #2

LD, DM, ED, BP. ED pattern, DM inactive.

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SLIDE 22

Apparatus configuration #2

LD, DM, ED, BP. ED pattern, DM inactive. Region, 6 ns pulse, DM inactive.

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SLIDE 23

Apparatus configuration #2

LD, DM, ED, BP. ED pattern, DM inactive. Region, 6 ns pulse, DM inactive. Region, 6 ns pulse, DM active.

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SLIDE 24

Apparatus configuration #3

LD, DM, ED, GG, BP.

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SLIDE 25

Apparatus configuration #3

LD, DM, ED, GG, BP. GG pattern, DM inactive.

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SLIDE 26

Apparatus configuration #3

LD, DM, ED, GG, BP. GG pattern, DM inactive. LD 6 ns pulse, DM inactive.

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SLIDE 27

Apparatus configuration #3

LD, DM, ED, GG, BP. GG pattern, DM inactive. LD 6 ns pulse, DM inactive. LD 6 ns pulse, DM active.

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SLIDE 28

Speckle reduction within single pulse durations

For 100 different pulse images for each duration.

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SLIDE 29

Verification for sensor sensitivity*

For 100 different pulse images for each duration.

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SLIDE 30

Verification for sensor gain*

For 100 different 6 ns pulse images for each gain factor.

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SLIDE 31

Verification for DM wave amplitudes**

For 100 different pulse image pairs for each duration.

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SLIDE 32

Conclusions

Relative improvement of > 20% to speckle contrast ratio demonstrated and verified for ≥ 6 ns pulse durations. Should improve spatial resolution . . . by reducing the need for averaging within a range image. Should improve temporal resolution . . . by reducing the need for averaging across multiple images.

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SLIDE 33

Conclusions

Relative improvement of > 20% to speckle contrast ratio demonstrated and verified for ≥ 6 ns pulse durations. Should improve spatial resolution . . . by reducing the need for averaging within a range image. Should improve temporal resolution . . . by reducing the need for averaging across multiple images.

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SLIDE 34

Conclusions

Relative improvement of > 20% to speckle contrast ratio demonstrated and verified for ≥ 6 ns pulse durations. Should improve spatial resolution . . . by reducing the need for averaging within a range image. Should improve temporal resolution . . . by reducing the need for averaging across multiple images.

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SLIDE 35

Conclusions

Relative improvement of > 20% to speckle contrast ratio demonstrated and verified for ≥ 6 ns pulse durations. Should improve spatial resolution . . . by reducing the need for averaging within a range image. Should improve temporal resolution . . . by reducing the need for averaging across multiple images.

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SLIDE 36

Thank You!

Please contact me to discuss: fshevlin@dyoptyka.com

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