Anti-drift and auto-alignment mechanism for an astigmatic atomic force microscope system based on a digital versatile disk optical head

Abstract

In this work, an anti-drift and auto-alignment mechanism is applied to an astigmatic detection system (ADS)-based atomic force microscope (AFM) for drift compensation and cantilever alignment. The optical path of the ADS adopts a commercial digital versatile disc (DVD) optical head using the astigmatic focus error signal. The ADS-based astigmatic AFM is lightweight, compact size, low priced, and easy to use. Furthermore, the optical head is capable of measuring sub-atomic displacements of high-frequency AFM probes with a sub-micron laser spot (~570 nm, FWHM) and a high-working bandwidth (80 MHz). Nevertheless, conventional DVD optical heads suffer from signal drift problems. In a previous setup, signal drifts of even thousands of nanometers had been measured. With the anti-drift and auto-alignment mechanism, the signal drift is compensated by actuating a voice coil motor of the DVD optical head. A nearly zero signal drift was achieved. Additional benefits of this mechanism are automatic cantilever alignment and simplified design.

Hacking CD/DVD/Blu-ray for Biosensing

“…Consequently, the optical path difference could reduce in more than 20% the reflected laser intensity. 17 …”

Open-source force analyzer with broad sensing range based on an optical pickup unit

“…Furthermore, the low-cost OPU can achieve nano-meter displacement sensitivity from 0.1 Hz to MHz signal bandwidth. OPUs have been successfully utilized for various applications, such as AFMs [14] , [15] , [16] , stereolithography 3D printing [17] , photolithography [18] , and biosensing [19] .…”

Micro and nanoscale 3D printing using optical pickup unit from a gaming console

“…The mass produced OPU (costs less than five USD) provides not only a light source but also diffraction-limited optics in a compact size, similar to a car key. Given its high-precision measurements and multiple wavelength laser modes, the OPU has been used for various other applications, such as atomic force microscopy [26][27][28] , biosensing 29,30 , and photolithography 31 . The HD-DVD OPU equips an aspherical objective lens with a numerical aperture of 0.65, aperture diameter of 3 mm, and assumed laser beam quality of 1.…”