Beam Steering Mirror (Voice-coil Mirror)

Beam Steering Mirror (Voice-coil Mirror)

Keywords: beam steering, steered mirror, optics, scanning
Jun 10, 2020 View: 3897 Data Sheet

We are developing 2D beam steering solutions that can be used in reflection mode (2D mirror) or in transmission mode (tunable prism).

Whether in R&D or in product development, our disruptive 2D beam steering solutions offer completely new design and integration possibilities. They can be used in reflection mode (2D mirror) or in transmission mode (tunable prism).

beam steering mirror beam steered mirror

Main features:

  1. 2D beam deflection with a single optical element
  2. Large clear apertures and beam angles
  3. Compact & lightweight

Dual axis vector scan mirror with position feedback

Our dual axis mirrors (called as voice-coil mirror, scan mirror, beam steering mirror) offer the benefit of large deflections and large mirror size in a compact package. The actuator is based on proven technologies. A built-in position feedback allows it to be accurately controlled with a standard PID controller. The virtual rotation point of our 2D mirrors is close to the mirror surface which makes 2D scanning straight forward. Applications range from automotive (LiDAR, dynamic headlights, ADAS) and vision (field-of-view expansion, zoom) to biometric (eye-tracking), diagnostics and 3D printing.

Tunable prism for laser alignment and image stabilization

Our tunable prism (TP) is suitable for optical alignment and beam-steering in transmission. The core element can be combined with your preferred actuation method and achieve a compact form factor. The low absorption makes it suitable for high-power applications. Thanks to the low dispersion liquid it can also be used for polychromatic applications.

3D beam steering

Combining a 2D mirror for x/y with an electrically focus tunable lens allows you to direct your laser beam spot precisely and fast at any point within the addressable volume. This can be of interest for dynamic headlights, diagnostic and spectroscopic devices and 3D printing.

beam steering

1. Dual axis vector scan mirrors with position feedback

STOT-MR-15-30, STOT-MR-10-30

Compact, fast and precise beam steering

Our dual axis mirror series (called as beam steering mirror, scan mirror, voice-coil mirror) is the ideal choice for applications that require a large field of view combined with a compact form factor. With a package size of 30 x 14.5 mm it achieves up to ±25° mechanical tilt, corresponding to ± 50° optical deflection. The mirrors contain a position feedback system enabling accurate control of deflection angle within ±100 mrad using a standard PID controller.

In addition to the popular quasi-static version, two resonant versions are available: First, a single axis resonant mirror. Second, a linear axis combined with a perpendicular resonant axis. In contrast to galvo mirror heads, the rotation point is very close to the mirror surface. The mirrors are available for use with light in different wavelength ranges such as UV, VIS, and NIR.

Advantages

  • Large 2D scan angle
  • Compact
  • Precise

Applications

  • Automotive (LiDAR, dynamic headlights, ADAS)
  • Vision (field-of-view expansion, zoom)
  • Biometric (eye-tracking) , diagnostic equipment & 3D printing
Specifications STOT-MR-15-30 STOT-MR-10-30
Scan direction bi-axial bi-axial
Mechanical tilt angle ±25° X axis; ±25° Y axis ±25° (slow) X axis; ±12.5° (fast) Y axis
Mirror diameter 15 mm 10 mm
Resolution (closed loop) <5 mrad <5 mrad
Repeatability RMS (typical) 30 - 100 mrad 30 - 100 mrad (slow) X axis
Full scale bandwidth 20 Hz 20 Hz (slow) X axis; 280 Hz (fast) Y axis
Mirror coating gold, protected silver gold, protected silver
Mirror reflectivity (gold coating) avg >97% for NIR avg >97% for NIR
Mirror flatness (P-V) l/2 l/2

2. Tunable prism for laser alignment and image stabilization STOT-TP-12-16

The tunable prism is a tunable wedge that allows to tilt two optically flat and AR coated glass windows with respect to each other. The two glass windows are held together by a bellow structure that is filled with a low dispersion clear optical fluid. The core element can be integrated with a large variety of actuation principles such as mechanical or motorized lead screws, voice-coil and piezo actuators.

The following table outlines the specifications of our standard tunable prism core element for a particular fluid. Cover glass coatings and fluids can be adapted on demand.

Applications:

  • Intuitive beam-steering in transmission configuration
  • Alignment between source and detector
  • Laser range finder
  • Image stabilization

Customization:

Our tunable prism can be taylored to your specific requirements. Contact us with your requirements and we would be happy to assess the feasibility of your project.

The following table summarizes the main specifications of the STOT-TP-12-16:

Clear aperture Outer diameter Max mech. tilt angle Max. optical deflection
STOT-TP-12-16 12mm 16mm +/- 20° 8.2°

Mechanical Specifications:

  • Clear aperture: 12mm
  • External diameter: 16mm
  • Thickness: 12 ± 0.5mm
  • Weight: 3.4g
  • Max. mechanical tilt angle (center pivot point)1: 20degree

Optical Specifications:

  • Max optical deflection @ 525nm: 8.2degree
  • Refractive index (25°C, @525nm): 1.38
  • Abbe number V (at 25°C): 63
  • Flatness of windows @525nm: 0.5 lambda
  • Refractive index vs temperature (dn/dT): -3.3e-4 1/°C
  • Transmission spectrum: 420-950 nm
  • Optical damage threshold @ 525nm: Depends on selected coating
  • Absorption:<0.1%
  • Polarization change: preserving
  • Storage temperature: [-40,+85] °C
  • Operating temperature: [-40,+85] °C
  • Mechnical dimension: dia. 16mm, height 12mm

Beam deflection

The beam deflection of a ray passing through the wedge with an apex angle

Where n is the refractive index of the optical fluid inside the wedge.

beam steering

Optical layout

The following figure contains the information needed to model the STOT-TP-12-16 for simulations.

beam steering

Transmission range

The optical fluid and the two glass windows are highly transparent and hardly absorbing in the range of 250 – 2500nm. The figures below show the transmission spectrum for the standard extended VIS coating (420- 950 nm) assuming normal incidence. By request cover glasses can be coated as desired.

beam steering

3. Mirror Driver STOT-MR-E-2

The STOT-MR-E-2 driver is an ideal solution for driving the MR-series 2D beam steering mirrors. It consists of a base unit containing control electronics and an integrated head unit with mirror and driving electronics. The driver in the standard version with housings can be used for testing and proof of concept work. The boards without housing are available as OEM version for integration with system electronics.

The driver is compatible only with our mirrors and allows various operation modes. The driver can be controlled from a host PC via our user interface. In addition, the driver offers the following communication interfaces:

  • USB, UART
  • SPI (I2C available as customization)
  • Analog input (± 5 V)
  • Software SDKs for Python and C# are available. The driver is RoHS, REACH and CE certified.
Standard products Mirror type included Components included
STOT-MR-E-2 Base unit N/A STOT-MR-E-2 Base unit controller box, power supply, USB cable
STOT-MR-E-2 Mirror head gold MR-15-30-G-25x25D Mirror head (incl. mirror and cable) protection cap, heatsink
STOT-MR-E-2 Mirror head silver MR-15-30-PS-25x25D Mirror head (incl. mirror and cable), protection cap, heatsink
STOT-MR-E-2 Mirror head custom MR-C-15-30 (custom mirror), or resonant mirror MR-10-30-G/MR-10-30-PS Mirror head (incl. mirror and cable), protection cap, heatsink
STOT-MR-E-2 OEM version N/A Carrier board (without housing), CPU board (without housing), proxy board (without mirror head), connection cable

4. Comparison of Scanning Technologies

Tilt vs Mirror Size-competing technologies

voice coil mirror

Voice-coil Mirror (VCM, beam steering mirror) in Comparison to MEMS and Galvo

beam steering mirror

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