Optical Design for Automatic Identification

(1)

Optical Design

for Auto ID

and Portable

Systems

Luisa De

Marco

Introduction

Research aim Research results

Imaging

System

SAFARILAB OLOM SLALOM

Non Imaging

System

Freeform lens design tool Pattern generator design tool

Conclusions

Optical Design for

Automatic Identification

and Portable Systems

Luisa De Marco

tutors:

Prof. Paolo Bassi, eng. Federico Canini

cotutors:

eng. Marco Gnan, eng. Bassam Hallal

(2)

Optical Design

for Auto ID

and Portable

Systems

Luisa De

Marco

Introduction

Imaging

System

Non Imaging

System

Conclusions

Outline

1 Introduction

Research aim

Research results

2 Imaging System

S

A

F

A

R

I

LAB

OLO

M

SLA

L

O

M

3 Non Imaging System

Freeform lens design tool

Pattern generator design tool

(3)

Optical Design

for Auto ID

and Portable

Systems

Luisa De

Marco

Introduction

Imaging

System

Non Imaging

System

Conclusions

Outline

1 Introduction

Research aim

Research results

2 Imaging System

S

A

F

A

R

I

LAB

OLO

M

SLA

L

O

M

3 Non Imaging System

Freeform lens design tool

Pattern generator design tool

(4)

Optical Design

for Auto ID

and Portable

Systems

Luisa De

Marco

Introduction

Imaging

System

Non Imaging

System

Conclusions

Research aim

: new

Optical Design Techniques

to improve Auto ID and Portable systems Performance

Possible applications

:

(5)

Optical Design

for Auto ID

and Portable

Systems

Luisa De

Marco

Introduction

Imaging

System

Non Imaging

System

Conclusions

Research results

Imaging Systems

Characterization tool

(

SAFARILAB

)

to measure the system Spatial

Frequency Response, SFR

Optical Level Optimization

tool (

OLOM

)

to optimize the optical part of

the imaging system (lens)

System Level Analysis and

Optimization tool (

SLALOM

)

to analyze and optimize the

whole imaging system (lens,

electronics, detector)

Non Imaging Systems

Freeform lens design tool

to optimize a freeform lens

that used with a LED produces

a custom illumination

Pattern generator design tool

to optimize a diffractive optics

that used with a LASER

produces the desired pattern

(6)

Optical Design

for Auto ID

and Portable

Systems

Luisa De

Marco

Introduction

Imaging

System

Non Imaging

System

Conclusions

Outline

1 Introduction

Research aim

Research results

2 Imaging System

S

A

F

A

R

I

LAB

OLO

M

SLA

L

O

M

3 Non Imaging System

Freeform lens design tool

Pattern generator design tool

(7)

Optical Design

for Auto ID

and Portable

Systems

Luisa De

Marco

Introduction

Imaging

System

Non Imaging

System

Conclusions

S

A

F

A

R

I

LAB

Imaging System characterization

: Spatial Frequency

Response measurement (SFR =

F

[PSF])

Edge Source

: Slanted edge to avoid sampling effect

(dependency on pixel array alignment wrt the edge)

(8)

Optical Design

for Auto ID

and Portable

Systems

Luisa De

Marco

Introduction

Imaging

System

Non Imaging

System

Conclusions

S

A

F

A

R

I

LAB

Software:

calculates SFR from a slanted edge image

follows the ISO 12233 standard

reduces the noise that affects the measurement

(9)

Optical Design

for Auto ID

and Portable

Systems

Luisa De

Marco

Introduction

Imaging

System

Non Imaging

System

Conclusions

S

A

F

A

R

I

LAB

SaFaRiLAB vs Imatest and ImageJ:

(10)

Optical Design

for Auto ID

and Portable

Systems

Luisa De

Marco

Introduction

Imaging

System

Non Imaging

System

Conclusions

S

A

F

A

R

I

LAB

Noise reduction:

0

0.5

1

1.5

2

0

0.2

0.4

0.6

0.8

1 Normalized spatial frequency

SFR

(11)

Optical Design

for Auto ID

and Portable

Systems

Luisa De

Marco

Introduction

Imaging

System

Non Imaging

System

Conclusions

OLO

M

Optical Level Optimization

(OLOM) tool: able to optimize

at Optical Level (just lens) an imaging system with SFR

invariance as

Cubic Phase Mask

(CPM) System

SFR

(12)

Optical Design

for Auto ID

and Portable

Systems

Luisa De

Marco

Introduction

Imaging

System

Non Imaging

System

Conclusions

OLO

M

Optical imaging system design (in ZEMAX):

already designed lens

optimization of

α

in cubic phase mask using OLO

M

(

CPM

=

f

(

x

,

y

) =

α

(

x

3 +

y

3 )

)

S

T

O

P

C

P

M

C

D

S

E

N

S

O

R

S

T

O

P

ORIGINAL LENS

(13)

Optical Design

for Auto ID

and Portable

Systems

Luisa De

Marco

Introduction

Imaging

System

Non Imaging

System

Conclusions

OLO

M

Performance design evaluation:

minimum resolving power [Mils]

0 0.25 0.5 0.75 1 0 0.25 0.5 0.75 1

Normalized spatial frequency

SF R

threshold (th)

frequency limit (f

th

)

R =minimum resolution

M = magnification

(14)

Optical Design

for Auto ID

and Portable

Systems

Luisa De

Marco

Introduction

Imaging

System

Non Imaging

System

Conclusions

OLO

M

Performance without CPM vs with CPM and

MEASURED vs DESIGNED:

the CPM extends the Depth Of Field (DoF);

measured and designed results are comparable.

0

200

400

600

800 1000

1200

1400

13 mils

20 mils

40 mils

Object Distance [mm]

826

886

386

392

443

445

227

234

284

292

168

178 NOCPM−DESIGNED

NOCPM−MEASURED

CPM−DESIGNED

CPM−MEASURED

(15)

Optical Design

for Auto ID

and Portable

Systems

Luisa De

Marco

Introduction

Imaging

System

Non Imaging

System

Conclusions

SLA

L

O

M

System Level Analysis and Optimization

(SLA

L

O

M

) tool:

able to optimize and analyze at System Level (lens,

electronics decoder) an imaging system with SFR

invariance

(16)

Optical Design

for Auto ID

and Portable

Systems

Luisa De

Marco

Introduction

Imaging

System

Non Imaging

System

Conclusions

SLA

L

O

M

System Level Analysis and Optimization

(SLA

L

O

M

) tool:

(17)

Optical Design

for Auto ID

and Portable

Systems

Luisa De

Marco

Introduction

Imaging

System

Non Imaging

System

Conclusions

SLA

L

O

M

Optical imaging system design (in ZEMAX):

Two possible design for adding a quartic contribution to

an original lens:

First Design

: change of a surface of the original lens

Second Design

: addition of a lens with a quartic

surface

starting design optimized by OLO

M

optimization of the quartic surface using SLA

L

OM

S T O P

C

D

S

E

N

S

O

R

S T O P

ORIGINAL LENS

Second Design First Design

(18)

Optical Design

for Auto ID

and Portable

Systems

Luisa De

Marco

Introduction

Imaging

System

Non Imaging

System

Conclusions

SLA

L

O

M

First Design

: before and after using SLA

L

OM

DEC FAIL Object Distance [mm] DEC FAIL Object Distance [mm]

Second Design

: before and after using SLA

L

OM

DEC FAIL Object Distance [mm] DEC FAIL Object Distance [mm]

(19)

Optical Design

for Auto ID

and Portable

Systems

Luisa De

Marco

Introduction

Imaging

System

Non Imaging

System

Conclusions

Outline

1 Introduction

Research aim

Research results

2 Imaging System

S

A

F

A

R

I

LAB

OLO

M

SLA

L

O

M

3 Non Imaging System

Freeform lens design tool

Pattern generator design tool

(20)

Optical Design

for Auto ID

and Portable

Systems

Luisa De

Marco

Introduction

Imaging

System

Non Imaging

System

Conclusions

Freeform lens design tool

Freeform lens design for a

Custom Illumination

:

limited into a desired area and with more light along the

area edges (compensation for sensor light losses)

implementation (in MATLAB) of a software for

optimization of the free-form lens coefficients

z

=

f

(

x

,

y

) =

c

1 x

2 +

c

2 y

2 +

c

3 x

4 +

c

4 x

2 y

2 +

c

5 y

4 · · ·

(21)

Optical Design

for Auto ID

and Portable

Systems

Luisa De

Marco

Introduction

Imaging

System

Non Imaging

System

Conclusions

Freeform lens design tool

Surface measurement of the lens Free-Form prototype:

Good agreement between measured and designed

surface

(22)

Optical Design

for Auto ID

and Portable

Systems

Luisa De

Marco

Introduction

Imaging

System

Non Imaging

System

Conclusions

Freeform lens design tool

Irradiance profile measurement:

Good agreement between irradiance profile of free-form

lens DESIGNED and MEASURED

(23)

Optical Design

for Auto ID

and Portable

Systems

Luisa De

Marco

Introduction

Imaging

System

Non Imaging

System

Conclusions

Pattern generator design tool*

Problem

:

to design a Diffractive Optical Element, DOE that with a

LASER produces a large Field Of View, FoV (not paraxial

hypothesis).

Image

DOE

LASER

F

O

V

= 40°

(24)

Optical Design

for Auto ID

and Portable

Systems

Luisa De

Marco

Introduction

Imaging

System

Non Imaging

System

Conclusions

Pattern generator design tool

Starting point

:

Iterative Fourier Transform Algorithm (IFTA) that assumes

paraxial approximation.

Y

@D

Y

Amplitude

Constraint:

DOE*

(CGH plane)

Projection

(image plane)

DOE

(CGH plane)

Projection*

(image plane)

Amplitude

Constraint:

)

,

(

*

y

x

F

ν

)

,

(

x

y

F

ν

))

arg(

exp(

*

f

j

f

=

*

|

exp(

arg(

))

F

j

F

=

des

)

,

(

*

y

x

f

)

,

(

x

y

f

(25)

Optical Design

for Auto ID

and Portable

Systems

Luisa De

Marco

Introduction

Imaging

System

Non Imaging

System

Conclusions

Pattern generator design tool

Solution

:

predistortion of desired image considering the effects

caused by non paraxial angle assumption.

blue line: desired image (little square at 20

◦

, big square

at 40

◦

);

red line: predistorted desired image

−0.4 −0.3 −0.2 −0.1 0 0.1 0.2 0.3 0.4 −0.4 −0.3 −0.2 −0.1 0 0.1 0.2 0.3 0.4

(26)

Optical Design

for Auto ID

and Portable

Systems

Luisa De

Marco

Introduction

Imaging

System

Non Imaging

System

Conclusions

Pattern generator design tool

Patterns generated by DOEs designed with and without

(27)

Optical Design

for Auto ID

and Portable

Systems

Luisa De

Marco

Introduction

Imaging

System

Non Imaging

System

Conclusions

Pattern generator design tool

FoV measurement

:

100

200

300

400

500 -300

-200

-100

0

100

200

300 z[mm]

x

[mm]

21.2°

21.4°

41.4°

45.2°

CPA

PA

20°

40°

SPEC

(28)

Optical Design

for Auto ID

and Portable

Systems

Luisa De

Marco

Introduction

Imaging

System

Non Imaging

System

Conclusions

Outline

1 Introduction

Research aim

Research results

2 Imaging System

S

A

F

A

R

I

LAB

OLO

M

SLA

L

O

M

3 Non Imaging System

Freeform lens design tool

Pattern generator design tool

4 Conclusions

(29)

Optical Design

for Auto ID

and Portable

Systems

Luisa De

Marco

Introduction

Imaging

System

Non Imaging

System

Conclusions

Imaging Systems

Characterization tool

(

SAFARILAB

)

able to measure imaging

systems performance

Optical Level Optimization

tool (

OLOM

)

provides a starting point optical

design for the whole system

optimization

System Level Analysis and

Optimization tool (

SLALOM

)

provides a whole optimized

system

Non Imaging Systems

Freeform lens design tool

freeform lens optimized to

obtained the desired

illumination

Pattern generator design tool

DOE optimized to obtained the

desired pattern

(30)

Optical Design

for Auto ID

and Portable

Systems

Luisa De

Marco

Introduction

Imaging

System

Non Imaging

System

Conclusions

THANKS

FOR YOUR

ATTENTION!