Application Cases

Experiment Title: Performance Testing of Low-Order Large-Stroke Aberration Compensation Devices

Testing Purpose:Based on the design scheme and research results, a deformable mirror with 3 units and a single piezoelectric plate for low-order aberrations was prepared as a low-order large-stroke aberration compensation device. An experimental system was set up to test its relevant performance and compare the results with the simulation.

Testing Equipment:High Voltage Amplifier, Hartmann Sensor, Bimorph Deformable Mirror, Computer, etc.

Experiment Process:

Figure 1: Structural Flowchart of the Deformable Mirror Influence Function Testing System

Figure 2: Experimental Optical Layout

The beam emitted from the built-in light source of the Hartmann wavefront sensor is incident on the surface of the deformable mirror after passing through the collimating and expanding system and the beam splitter reflector inside the sensor. After reflection from the deformable mirror, the beam carrying the surface information of the deformable mirror is incident on the detector target surface inside the Hartmann sensor. The wavefront reconstruction is completed by the control computer of the Hartmann sensor, thus completing the testing of the deformable mirror surface.

The wavefront detection device is a Hartmann sensor with a built-in collimating light source and an aperture of 30mm. The detection results and image acquisition are completed by the wavefront acquisition control center. The driving voltage is generated by the control center as a voltage signal and amplified and output through a 47-channel high voltage amplifier.

Experimental Results:

Figure 3: Initial Surface Shape Measured by Laser Interferometer

From the results in the figure, the full-aperture surface shape PV of the deformable mirror is approximately 3.35 wavelengths, and the surface shape PV within the 15mm effective aperture is approximately 1.12 wavelengths. The test laser wavelength of the interferometer is 650nm, and the initial surface shape PV value within the effective aperture is 0.73μm. The polishing process of the silicon mirror and the bonding process of the deformable mirror can both lead to the initial surface shape being uneven. In the closed-loop correction process, the deformable mirror can correct its own initial surface shape.

Figure 4: Initial Surface Shape Measured by Hartmann Sensor

The initial surface shape within the effective aperture measured by the Hartmann sensor is shown in the figure above, with an initial surface shape PV value of 0.79μm, which is roughly the same as the result measured by the interferometer.

The influence function reflects the surface deformation capability of the deformable mirror under the driving voltage. The surface characteristics of the influence function directly determine the compensation accuracy of the deformable mirror for wavefront distortion. The magnitude of its amplitude also determines the correction stroke of the deformable mirror. The larger the stroke, the stronger the ability of the deformable mirror to correct aberrations in a single correction, and the faster the closed-loop correction speed.

High Voltage Amplifier Recommendation: ATA-7010

Figure: Specifications of the ATA-7010 High Voltage Amplifier

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