Frequently Asked Questions (All)

What driver is faster -- PCI board or USB unit?

Electronics
Currently, PCI board is our fastest option. The speed of the USB DAC unit is limited by the restrictions of the USB bus, which updates the values once per 1 ms (all 40 channels are updated at once). For the PCI boards, every channel is updated sequentially, with 1 µs delay (measured value; the data sheet for the chip used on the boards says 5 µs).

How good is the initial figure of OKO deformable mirrors?

General

The surface quality of all OKO mirrors is similar to any other solid reflective optics produced by leading manufacturers. It is good enough to work with very low scattering in the whole visible spectrum.

The initial figure of MMDM is flat with RMS deviation from the nearest reference plane better than 400nm. OKO mirror with 37 channels and a diameter of 15mm will have less than 1 fringe of astigmatism averaged over a number of devices. Larger MMDM have 8 adjustment screws that allow to set the initial figure of the mirror. The initial optical quality is very good.

The initial figure of PDM is flat with RMS deviation from the nearest sphere better than 500 nm. The initial surface may have some irregularity due to random hysteresis state of different actuators. These irregularities are always formed as combinations of the mirror influence functions and they are completely correctable by the mirror.

What is "biased operation"?

MMDMs

The MMDM membrane can be deflected only in the direction of the electrode structure because the electrostatic force can be only attractive. This means the deflected membrane can produce only concave optical shapes with a reference to a flat surface. To achieve bi-directional operation the membrane should be initially deflected towards the actuators and made perfectly spherical by adjusting the actuator voltages. From this state the membrane can be moved to both positive (from the electrode structure) and negative (to the actuator structure) directions by controlling the actuators voltage.

How to use FrontSurfer wavefront sensor for optical shop testing?

Wavefront sensors
Setup for testing of optical components should provide optical conjugation between the component under test and the wavefront sensor with proper scaling. See section our Product Guide for general recommendations and typical measurement schemes.

What is the closed-loop correction speed in FrontSurfer?

Adaptive optical systems

The correction speed is mainly limited by the camera's frame rate. However, it is also dependent on other factors, including the speed of the deformable mirror and its controller, number of spots in the Shack-Hartmann pattern, number of DM actuators and available light level.

With Basler A602f camera we achieved correction rates up to 90 Hz at a full frame and up to 380 Hz at an area of interest of 128x128 pixels. Correction rates up to 440 Hz were achieved with Andor DU-860 fast EMCCD camera.

Using of multiprocessor and multiple-core PCs is recommended for highest performance.

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Flexible Optical B.V. (OKO Technologies)