Laser Speckle Reducer

  • Update:Sep 06, 2017
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Our laser speckle reducers are nothing other than moving diffusers. But the way they are actuated is absolutely unique. Two innovative technologies are offered, each with its own advantages.

Product Introduction

Our laser speckle reducers are nothing other than moving diffusers. But the way they are actuated is absolutely unique. Two innovative technologies are offered, each with its own advantages.

Electro-active polymer STOT-LSR

With its launch in 2011, we are the first to commercialize electro-active polymers (EAPs) in the field of optics. The basis of this approach is a thin, elastic membrane that carries a lightweight diffuser in its center and four electrodes surrounding it. Actuated at a 90° phase shift, the electrodes induce a circular oscillation of the diffuser in x- and y-direction. The ultra-compact form factor, minimal weight and the absence of noise and vibrations make this technology particularly attractive for hand-held devices.

Reluctance Force STOT-LSR

Launched in 2016, the reluctance force STOT-LSR is particularly suitable for applications that require large format glass diffusers. The basis of this approach is a single thin steel structure that is brought into resonance by pulsing an actuating coil with current, which generates a strong reluctance force. Thanks to a high q-factor large amplitudes in the range of 800um are achieved at low power consumption even for heavy glass diffusers.

 

Electroactive polymer STOT-LSR

Reluctance force STOT-LSR

Specifications

Clear aperture

5 or 10mm

18.5x18.5mm

Diffuser

Optotune polymer

Glass or polycarbonate

Transmission

Up to 93%

Up to 98%

Oscillation type

2D (circular)

1D (linear)

Oscillation amplitude

300-400um

800um

Resonant frequency

300 or 180Hz

~120Hz (depends on diffuser weight)

Weight

3g

11g

Vibrations

None

Low (depends on mechanical mount)

Cover glasses

Required

None

Electronics

5 VDC (EAP is pulsed with 300V)

5 VDC (coils are pulsed with current)

Applications

Customization

Our laser speckle reducers can be taylored to your specific demands in terms of size, oscillation frequency or transmission range. Tell us your requirements and we will be happy to assess the feasibility.

Electroactive Polymer STOT-LSR

Within a height of less than 1mm, electroactive polymers are used to bring a polymer diffuser into resonant oscillation with e.g. 400µm travel at several 100 Hz. This electrostatic principle is very power-efficient, completely silent and free of vibrations, an ideal choice for hand-held devices.

The following table summarizes the main specifications of currently available laser speckle reducers:

Specifications

STOT-LSR-3005

 STOT-LSR-3010

STOT-LSR-5-17

STOT-LSR-10-22

 

 

Product description

Scientific standard

Scientific standard

OEM standard

OEM standard

Size (Ø or L x H)

 41mm x 8.8mm

 48mm x 8.8mm

 17mm x 3.8mm

22mm x 3.8mm 

Clear aperture

5mm

10mm

 5mm

 10mm

Oscillation frequency

300Hz

180Hz

300Hz

 180Hz

Oscillation amplitude

300um

400um

300um

400um 

Electronics

Integrated, CE certified

Integrated, CE certified

Optional, not certified

Optional, not certified

Results

The following figure shows typical images of the speckle contrast measured on a reference setup with and without STOT-LSR. The colored lines show the cut planes that correspond to the intensity plot.

Speckle reduction measured with a CCD camera

Applications

Transmissive Laser Speckle Reducer STOT-LSR-3005

The STOT-LSR-3005 is designed for practical use on your optics table and integrates certified drive electronics powered through a single micro-USB connector (5VDC). Four standard diffuser configurations are available ranging from 6° (highest optical efficiency) to 24° (best speckle reduction). Most models combine an oscillating diffuser with a static diffuser to reduce the correlation length of the random patterns that are generated. This provides more effective speckle reduction yet minimizing the increase in beam divergence. The 17° model, which consists of a dynamic diffuser only, is particularly suitable when the diffuser needs to be in the image plane as is the case e.g. with holographic LCOS or in fiber coupling setups.

With an oscillation frequency of 300Hz and an amplitude of about 300um, the 5mm aperture model is the preferred choice for applications with high frame rates. VIS and NIR coated cover glasses are provided as a standard. Other coating options as well as diffuser combinations are available upon request.

The following table summarizes the main specifications of the standard STOT-LSR-3005 series:

Standard products

Total diffusion angle

Diffuser configuration

Cover glass coating

STOT-LSR-3005-6D-VIS

4.2° oscillating,  4.2° static

400 - 700nm

STOT-LSR-3005-12D-VIS

12°

8.5° oscillating,  8.5° static

400 - 700nm

STOT-LSR-3005-24D-VIS

24°

17° oscillating,  17° static

400 - 700nm

STOT-LSR-3005-17S-VIS

17°

17° oscillating,  no static

400 - 700nm

STOT-LSR-3005-6D-NIR

4.2° oscillating,  4.2° static

700 - 1100nm

STOT-LSR-3005-12D-NIR

12°

8.5° oscillating,  8.5° static

700 - 1100nm


 Finding an appropriate system layout is key to effective and efficient speckle reduction. Our application note contains several suggestions, suitable for a variety of applications.

Transmissive Laser Speckle Reducer STOT-LSR-3010

The STOT-LSR-3010 is designed for practical use on your optics table and integrates certified drive electronics powered through a single micro-USB connector (5VDC). Two standard diffuser configurations are available: 6° for highest optical efficiency and 12° for best speckle reduction. Both models combine an oscillating diffuser with a static diffuser to reduce the correlation length of the random patterns that are generated. This provides more effective speckle reduction yet minimizing the increase in beam divergence.

With an oscillation frequency of 180Hz and an amplitude of about 400um, the 10mm aperture model is the preferred choice for applications with frame rates below 180Hz or for the human eye. For the STOT-LSR-3010 series only VIS coated cover glasses are provided as a standard. Other coating options as well as diffuser combinations are available upon request.

The following table summarizes the main specifications of the standard STOT-LSR-3010 series:

Standard products

Total diffusion angle

Diffuser configuration

Cover glass coating

STOT-LSR-3010-6D-VIS

4.2° oscillating, 4.3° static

400 - 700nm

STOT-LSR-3010-12D-VIS

12°

8.5° oscillating, 8.5° static

400 - 700nm

Finding an appropriate system layout is key to effective and efficient speckle reduction. Our application note contains several suggestions, suitable for a variety of applications.

Transmissive Laser Speckle Reducer STOT-LSR-5-17

The OEM version of our laser speckle reducer comes with a minimal housing and is available with or without drive electronics.

The most important parameter is the choice of diffuser angles. Standard diffuser angles of 1°, 4.3°, 8.5° and 17° are available. The STOT-LSR consists of a dynamic diffuser and optionally a subsequent static diffuser. The latter is recommended when no homogenizing optics follow the STOT-LSR to increase the speckle reduction factor. Finding an appropriate system layout is key to effective and efficient speckle reduction. Our application note contains several suggestions, suitable for a variety of applications.

Our standard diffusers are made of a proprietary polymer, which offers a transmission range of 240 to 2500nm at a typical transmission of 93% and damage threshold of 300W/cm2. The diffuser itself is not coated, however VIS and NIR coated cover glasses are available as a standard. It is also possible to work with glass diffusers if they are similar in size and weight.

With an oscillation frequency of 300Hz and an amplitude of about 300um, the 5mm aperture model is the preferred choice for applications with high frame rates.

Design possibilities

We has custom designed speckle reducers to suit diverse requirements. On the large side, diffusors of 50x20mm size have been actuated at >60Hz for head-up displays. On the small side, an STOT-LSR as tiny as 9x6x1mm has been prototyped for pico-projectors.

Transmissive Laser Speckle Reducer STOT-LSR-10-22

The OEM version of our laser speckle reducer comes with a minimal housing and is available with or without drive electronics.

The most important parameter is the choice of diffuser angles. Standard diffuser angles of 1°, 4.3°, 8.5° and 17° are available. The STOT-LSR consists of a dynamic diffuser and optionally a subsequent static diffuser. The latter is recommended when no homogenizing optics follow the STOT-LSR to increase the speckle reduction factor. Finding an appropriate system layout is key to effective and efficient speckle reduction. Our application note contains several suggestions, suitable for a variety of applications.

Our standard diffusers are made of a proprietary polymer, which offers a transmission range of 240 to 2500nm at a typical transmission of 93% and damage threshold of 300W/cm2. The diffuser itself is not coated, however VIS and NIR coated cover glasses are available as a standard. It is also possible to work with glass diffusers if they are similar in size and weight.

With an oscillation frequency of 180 Hz and an amplitude of about 400um, the 10mm aperture model is the preferred choice for applications with frame rates below 180Hz or for the human eye.

Design possibilities

Optotune has custom designed speckle reducers to suit diverse requirements. On the large side, diffusors of 50x20mm size have been actuated at >60Hz for head-up displays. On the small side, an STOT-LSR as tiny as 9x6x1mm has been prototyped for pico-projectors. 

Transmissive Laser Speckle Reducer STOT-LSR-4C

Our STOT-LSR-4C speckle reducer has an aperture of 18.5x18.5 mm and is especially suitable for applications where high laser powers and large beam diameters are used. The diffusor is mounted in a thin steel frame. As part of a larger metallic structure the frame is set into motion by the reluctance force, generated by the oscillating magnetic field of a driving coil. If required, the STOT-LSR-4C can combine two oscillating diffusors rotated by 90°, realizing optimized despeckling in both directions. The compact driving electronics, assembled on a flexible plastic substrate, stabilizes the resonance frequency in closed-loop mode and includes an error signal.

STOT-LSR-4C-L
(single linear oscillation)

STOT-LSR-4C-LL
(double linear oscillation)

 

 

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