Multiplexing image detector based digital sun sensors for ...

@mail.

Multiplexing image detector based

digital sun sensors for high precision

and large field of view

Minsong Wei, Fei Xing, Geng Wang, Zheng You

Department of Precision Instrument, Tsinghua University, Beijing, China

June 10,2014

Tsinghua University

Outline

1 Introduction

2 Multiplexing image detector method

3 The digital sun sensor with high performance

4 The wireless digital sun sensor

5 Summary

2

Tsinghua University

1 Introduction




5 Summary

3

Outline

Tsinghua University

Introduction

4

hy

z

txo

ty

Incident

sunray

Mask

Image detector

x

Sun spot

XO

Y

β

α

l

h

y

h

x

t

t

arctan

arctan

Sun

sensor

The sun sensors

Typical application of the sun sensors

Bentum M J, Leijtens J, Verhoeven C, et al. Measurements on an

autonomous wireless payload at 635 km distance using a sensitive radio

telescope//The 33rd ESA Antenna Workshop on Challenges for Space

Antenna Systems 2011

Principle of the Digital Sun Sensor(DSS)

Tsinghua University 5

Development of the sun sensors in Tsinghua Univ.

Feature FOV Accuracy Size/ mm3 MassPower

consumption

Analogue Sun Sensors

Wireless

(2013) 120°×120° 0.12°(1σ) 30×30×15 21g Self-powered

Digital Sun Sensors

Multiple

pinholes

(2009)

128°×128° 0.02°(3σ) not available 350g 2.5W

N-slit mask

(2011)120°×120° 0.06°(3σ) 80×60×30 130g 300mW

Introduction

FOV

Res

Tsinghua University

Introduction

6

Accuracy VS FOVh

y

z

o

Mask

Image detector

x

XO

Y

xs

ys

FOVx

FOVy

2cos ( )Res ( )dd l

h

2arctan2

sx

xFOV

h

2arctan2

sy

yFOV

h

h

d2arctan2

lFOV

h

Trade off between FOV and Resolution

Smaller FOV

Better Resolution

Larger FOV

Worse Resolution

h

2cos ( )( )dd d l

h

2cos ( )( )dd d l

h

Field of View（FOV）Accuracy ∝ Resolution（Res）

Tsinghua University

Outline

1 Introduction




5 Summary

7


Principle

Multiplexing image detector method

• Each pattern determines acorresponding sub-FOV

• The whole FOV is composedof all sub-FOVs

Advantages：

Extend the system FOV without decrease in resolution

Application of planar mask, no optical lens needed

Mask pattern is fabricated by MEMS procedures with high machining accuracy

Image detector

Mask

Sub-FOV1 Sub-FOV2Sub-FOV3

Image detector

Mask

FOV FOV

Conventional design – single pattern Multiplexing image detector method

hh

ldld

#3 #1 #2Pattern


Modeling

Multiplexing image detector method

0

- -arctan ,arctan

2 2

d m d ml l l lFOV

h h

：

1

2 + - - +2arctan ,arctan

2 2

m m d d m md l l l l dFOV

h h

：

2 + - - +2arctan ,arctan

2 2

m m d d m mn

nd l l l l ndFOV

h h

：

+ -- +2=2arctan =2arctan

2 2

d pattern md m ml l ll l nd

FOVh h

- +2( 1) 2 + -arctan arctan

2 2

d m m m m dl l n d nd l l

h h

The whole FOV

Continuous coverage requirement

m m dd l l

At least one pattern completely imaged on the detector at any incident angle

No gap between sub-FOVs

Image detector

Pattern

FOV0

FOV1

h

ld

lpattern

lm

dmlmlm lmlm

FOV-n

FOV-1

FOVn

Tsinghua University

Outline

1 Introduction




5 Summary

10

Tsinghua University

DSS with high performance

11

Implementation of multiplexing image detector

Resolution simulation result

Mask patternNs：the clearance between two adjacent apertures

N： the pixel size

1 0N

s

LLx N 2 0

Ns

LLy N

Group distinction

h=17.2mm is required to achieve arc-sec level resolution

h=17.2mm results in a FOV of 20°× 20°, approximately

CMOS image detector

1.3 million (1280×1024) pixels,

5.3 μm square pixels

FOV is broaden by multiplexing image detector method

A group of positioning apertures contains

three identical apertures

Every group is distinguished from each

other through the unique set of (Lx, Ly)

定位孔

L1 L2

lmx

dmx

dmy

Positioning apertures

Tsinghua University


12

Optimization design

Aperture size

169.6μm× 169.6μm

Incident angle θ =0°

Illustrated pixel number /number of pixels

Aperture size /×5.3um15 20 25 30 35

300

350

100

150

450

200

250

400

d=20pixels d=25pixels

d=30pixels d=35pixels

100μm 定位孔

L1 L2

lmx


d

d

Tsinghua University


13

Optimization design定位孔

L1 L2

lmx


≥Ns ≥Ns

Position/ ×5.3μm

1

0.9

0.4

0.2

0

Inte

nsi

ty

0.3

0.5

7550250-75 -50 -25

0 10 20 30 40 50 600.002

0.004

0.006

0.008

0.01

0.012

0.014

data1

data2

0.1

0.7

0.6

0.8

y directionx direction

Incident angle θ =50°

Clearance

Ns=100pixels

θ=0°

100μm

θ=20°

θ=35° θ=50°

d=169.6μm

Tsinghua University


14

Pattern parameters

Mapping code of (Lx, Ly)

1 0N

s

LLx N 2 0

Ns

LLy N

Group mapping design

Pattern size

lx×ly = 47.5 mm × 48.8 mm

Distance between adjacent groups

dmx×dmy = 3.392mm×3.816mm

Groups arrangement

13 × 13 groups

Mask pattern

定位孔

L1 L2

lmx

dmx

dmy


ly

lx

Groups in the same line are coded

with the same Lx and disparate Ly

Groups in the same column are coded

with the same Ly and disparate Lx

Each group has a unique (Lx, Ly)

Tsinghua University


15

Lab tests

Random error Measurement error

Performance

Accuracy--6.1″(3σ)

NO gapbetween sub-FOVs

Characteristics Performance

FOV 105° × 105°

Resolution 0.72″

Size 96×80×41.5mm3

Mass 182 g

Power consumption

500 mW

0 10 20 30 40 50 60 70 80 90 100-4

-3

-2

-1

0

1

2

3

4Error/″

Test #

0 20 40 60 80 100

0

2

-3

-4

3

4

-2

10 30 50 70 90

1

-1

0 10 20 30 40 50-8

-6

-4

-2

0

2

4

6

8

10

Yerror

Xerror

Error/″

Incident angle/°

0 10 20 30 40 50

0

4

2

-4

-8

β

-6

8

6

10

-2

α

0 10 20 30 40 50-8

-6

-4

-2

0

2

4

6

8

10

Yerror

Xerror

DSS prototype

Sun Simulator

Rotary table

Tsinghua University

Outline

1 Introduction




5 Summary

16

Tsinghua University

Wireless DSS

17

Multiplexing image detector method for profile sensor

Mask pattern

Lx, Ly：the clearance between two adjacent groups

256×256 pixels,

projection data output

A group of positioning apertures contains two identical apertures

The two apertures in one group arrange diagonally

Every group is distinguished from each other through the unique parameter Sx (Sy)

Sx

Sy

Lx

Ly

CMOS profile sensor

Sx Sy S 1i iS S

Safe distance limit — in case of misjudgment of groups

min max2Lx S min max2Ly S


Apertures locating

Wireless DSS

p2 p4

p1

p5

p6

p7

p3

Lxmin

Lymin

S4

S4

Aperture size 46.8μm×46.8μm

Group parameter S

S1=156μm Si+1= (Si+7.8)μm

Safe distance limit

Lxmin=686.4μm > 2Smax=405.6μm

Lymin=686.4μm > 2Smax=405.6μm

1. Get multiple peaks from X/Y direction output

Mask pattern

2. Pack the peaks by the safe distance limit

3. Group the packed peaks through the same S

4. Determine the group# and the location info.

Pixel number in X direction

0

Inte

nsi

ty

50 100 150 200 2500

50

100

150

200

250

Pix

el n

um

be

r in Y

dire

ctio

n0

Intensity

50

10

01

50

20

02

50

0 50

10

0

15

0

20

0

25

0

?


0

Inte

nsi

ty

50 100 150 200 2500

50

100

150

200

250

Pix

el n

um

be

r in Y

dire

ctio

n0

Intensity

50

100

150

200

250

0 50

100

150

200

250

Safe distance

Safe distance?


0

Inte

nsi

ty

50 100 150 200 2500

50

100

150

200

250

Pix

el n

um

be

r in Y

dire

ctio

n0

Intensity

50

100

150

200

250

0 50

100

150

200

250

Sx

Sy

Sx=Sy=S5

Safe distance

Safe distance

Tsinghua University

Wireless DSS

19

Electrical and mechanical design

Electrics

sketch map

Wireless DSS prototype

PCB board

with profile sensor

PCB board

with RF MCU

Mask

Bottom cover

Connecting partPCB board

with profile sensor

PCB board

with RF MCU

HousingSize 45×40×20mm3

Mass 38 g

Solar

cell

Power

management

AntennaRF MCU

Profile

DataSPI

S9132

3.3V

5V

3.3V

2.6V


Lab tests

Wireless DSS

Random error Measurement error

Prototype of the wireless DSS has an accuracy of 0.07°(3σ) within the whole FOV

System FOV is 100°×100° and there is no gap between sub-FOVs

Function of self-power is achieved during the whole FOV

under a sun simulator with the

brightness of 1 sun constant

Performance test

Results

Self-power test

0 10 20 30 40 50 60 70 80 90 100-0.06

-0.04

-0.02

0

0.02

0.04

0.06Error/°

Test #

0 20 40 60 80 100

0

0.02

-0.04

-0.06

0.04

0.06

-0.02

10 30 50 70 90 -50 -40 -30 -20 -10 0 10 20 30 40 50-0.025

-0.02

-0.015

-0.01

-0.005

0

0.005

0.01

0.015

0.02

Error/°

Incident angle/°

0 10 20 30 40 50

-0.005

0.005

0

-0.015

-0.025

-0.02

0.015

0.01

0.02

-0.01

-50 -40 -30 -20 -10

0 10 20 30 40 50-8

-6

-4

-2

0

2

4

6

8

10

Yerror

Xerrorβ α

Tsinghua University

Outline

1 Introduction




5 Summary

21

Tsinghua University

Summary

22

10 times more precise than traditional

DSS

FOV is increased by 25 times with the

employment of the multiplexing

image detector method

self-powered wireless DSS

5 times lower in size and weight

than traditional DSS

FOV and accuracy are improved by

the multiplexing image detector

method

Multiplexing image detector method can be applied

for FOV and accuracy improvement of DSS

FOV 105° × 105°

Accuracy 6.1″(3σ)

Size 96×80×41.5mm3

Mass 182 g

Power consumption

500 mW

FOV 100° × 100°

Accuracy 0.07°(3σ)

Size 45×40×20mm3

Mass 38 g

Power consumption

Self-powered

Thank you！Contact information：

Minsong Wei

Room 1306 Building 9003, Department of Precision Instrument, Tsinghua University

Beijing, China 100084

Email: [email protected]

Multiplexing image detector based digital sun sensors for ...

Documents