Browse Prior Art Database

Speckle-free illumination source with variable divergence and focus-tunable lenses in imaging/vision apllications

IP.com Disclosure Number: IPCOM000246685D
Publication Date: 2016-Jun-28
Document File: 83 page(s) / 5M

Publishing Venue

The IP.com Prior Art Database

Abstract

There is an increasing need for laser-based light sources for various biomedical imaging applications, including fluorescence imaging. Many of these sources have the drawback that the low coherence light creates speckle patterns that lead to hot-spots that decrease the image quality. It is often desirable to vary the divergence of the light that couples into the fiber bundle allowing thus for variable angular light distribution at the exit of the multi-mode fiber or fiber bundle. In this disclosure we demonstrate the concept and possible implementation of a speckle-free illumination source with variable divergence. We show that such an illumination source can be implemented with 2 key components , a laser speckle reducer (LSR) and a focus-tunable lens and a few optical elements. The second part of the disclosure describes the use of focus-tunable lenses in various imaging configurations.

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 17% of the total text.

Page 01 of 83

Speckle-free illumination source with variable divergence and focus-tunable lenses in imaging/vision applications

1


Page 02 of 83

Abstract

There is an increasing need for laser-based light sources for various biomedical imaging applications, including fluorescence imaging. Many of these sources have the drawback that the low coherence light creates speckle patterns that lead to hot-spots that decrease the image quality.

It is often desirable to vary the divergence of the light that couples into the fiber bundle allowing thus for variable angular light distribution at the exit of the multi-mode fiber or fiber bundle.

In this disclosure we demonstrate the concept and possible implementation of a speckle-free illumination source with variable divergence. We show that such an illumination source can be implemented with 2 key components , a laser speckle reducer (LSR) and a focus-tunable lens and a few optical elements.

The second part of the disclosure describes the use of focus-tunable lenses in various imaging configurations.

2


Page 03 of 83

Agenda


Speckle-free illumination source with variable divergence


Focus-tunable lenses in imaging/vision applications

3


Page 04 of 83

SPECKLE-FREE ILLUMINATION SOURCE WITH VARIABLE DIVERGENCE

4


Page 05 of 83

Goal


• For various bio-medical application it is desirable to have a laser based source for illumination:


- Fluorescence imaging


- Multi-wavelength imaging


- High-brightness


• Often these sources shall be coupled into an optical fiber (multimode fiber, fiber bundle) for easier deployment of the light to the sample under investigation.


• In addition to the speckle-reduction it can be desirable to have a mean to adjust the optical divergence at the output of the optical fiber.


• In this study, we use a laser speckle reducer which moves a diffusor in a linear motion in order to reduce the laser speckles and an electrically tunable focus variable polymer lens for divergence control.

5


Page 06 of 83

Configuration 1 - state 1

Focus tunable lens + offset lens(es)

Randomized fiber bundle

From laser source

Laser speckle reducer

6


Page 07 of 83

Configuration 1 - state 2

Focus tunable lens + offset lens(es)

Randomized fiber bundle

From laser source

Laser speckle reducer

7


Page 08 of 83

Configuration 1 with off-the-shelf components

Thorlabs LA1560A F=25

EL-6-18-TC [-20dpt, +20dpt] +
Thorlabs LA1074-A
F=20

Edmund Optics
Stock No. #65-830
4mm Aperture x 25mm L High NA, Fused Silica Light Pipe

Thorlabs LA1560A F=25

Randomized fiber bundle

From laser source

8-9mm

25mm

10mm

25mm

25 mm

Optotune LSR-4C-L
Fused silica diffusor
(8.5° FWHM)

8


Page 09 of 83

  Ray-tracing results: Configuration 1 - state 1

From laser source

Beam homogenizer

Collimation lens

Laser speckle reducer

Collimation lenses

Focus tunable lens

9


Page 10 of 83

  Ray-tracing results: Configuration 1 - state 2

From laser source

Beam homogenizer

Collimation lens

Laser speckle reducer

Collimation lenses

Focus tunable lens

10


Page 11 of 83...