Development of a Resonant Scanner to Improve the Imaging Rate of Astigmatic Optical Profilometers

Liao, Hsien-Shun; Cheng, Shih-Han; Hwu, En‐Te

doi:10.1109/tmech.2020.3011465

Cited by 4 publications

(5 citation statements)

References 24 publications

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“…We used the previously designed astigmatic optical profilometer featuring a resonant scanner for high-speed z-axis modulation [28]. The system configuration and mechanical design of the astigmatic optical profilometer are presented in Figure 3a,b, respectively.…”

Section: Astigmatic Optical Profilometermentioning

confidence: 99%

“…We previously developed a z-axis modulation method to decouple surface morphology and reflectivity, enabling the quantitative height measurement of surfaces consisting of complex materials [27]. In [28], we developed a resonant z-axis scanner to improve the imaging rate of astigmatic optical profilometers. In the present study, we developed a novel method for film thickness measurement using an astigmatic optical profilometer.…”

Section: Introductionmentioning

confidence: 99%

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Method for Film Thickness Mapping with an Astigmatic Optical Profilometer

Liao

Cheng

Hwu

2022

Sensors

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An astigmatic optical profilometer is a precision instrument with advantages such as high resolution, high bandwidth, a compact size, and low cost. However, current astigmatic optical profilometers measure only surface morphology, and their potential for capturing subsurface information remains underutilized. In this study, we developed a method for measuring the thickness of transparent thin films with an astigmatic optical profilometer. Experimental results demonstrate that the thickness of transparent films tens of micrometers thick can be accurately measured. The maximum thickness measurable through our system is approximately 100 μm, which may be increased to 1.2 mm through the use of a scanner with a greater travel range. A coupling problem occurs for films <25 μm in thickness. However, to solve this problem, we devised a decoupling method, which was experimentally implemented to successfully measure a 18-μm-thick film. Moreover, the ability to obtain 3D images, including of both the upper and lower surfaces, was demonstrated.

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Section: Astigmatic Optical Profilometermentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Method for Film Thickness Mapping with an Astigmatic Optical Profilometer

Liao

Cheng

Hwu

2022

Sensors

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“…A commercial DVD pickup head (TOP1100s, TopRay Technologies, Hsinchu City, Taiwan) was installed on a manual XYZ stage (XC2-60SMW and ZA-60MBW, Twin Nines, Saitama, Japan) to adjust the measurement location of the sample. We used a previously designed resonant scanner to oscillate the objective lens in the z-axis direction [23]. The resonant scanner was operated at a resonant frequency of 1.6 kHz, which can achieve a travel range of >87 μm.…”

Section: Astigmatic Optical Profilometermentioning

confidence: 99%

“…Previous studies have demonstrated that the astigmatic profilometer can measure not only the surface morphology but also the film thickness [21]. Moreover, the z-axis modulation mode of the astigmatic profilometer enables measurement of the S curve at each image pixel [22,23]. The slope of the S-curve linear region was positively correlated with the surface reflectance.…”

Section: Introductionmentioning

confidence: 97%

Real-Time Reflectance Measurement Using an Astigmatic Optical Profilometer

Liao

Huang

Syu-Gu

et al. 2022

Sensors

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An astigmatic optical profilometer with a commercial optical pickup head provides benefits, such as high resolution, compact size, and low cost. To eliminate artifacts caused by complex materials with different reflectances, a z-axis modulation mode is proposed to obtain quantitative surface morphology by measuring S curves on all image pixels. Moreover, the slope of the linear region in the S curve shows a positive relationship with the surface reflectance. However, the slope was calculated using an offline curve fitting method, which did not allow real-time reflectance imaging. Furthermore, quantitative reflectance data were unavailable because of the lack of calibration. In this study, we propose a novel method for real-time reflectance imaging by measuring the amplitude of a focus error signal (FES). The calibration results displayed a linear relationship between the FES amplitude and reflectance. The reflectance image of a grating sample with chrome patterns on a glass substrate demonstrates accurate reflectance measurements with a micrometer spatial resolution.

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“…In applications of precise optical systems [1][2][3], micromanufacturing systems [4][5][6], micro-manipulation systems [7][8][9][10], and so on, rotary piezoelectric actuators (RPAs) are widely used, due to their advantages of high resolution, ultrasonic-type RPA usually drives its rotor by the regular resonant vibration of its stator with a frequency above 20 kHz. The high frequency leads to severe wear and heat problems, which reduce its stability and resolution.…”

Section: Introductionmentioning

confidence: 99%

A large-step stick-slip rotary piezoelectric actuator with high velocity under low frequency and small backward motion

Xun

Zhang

et al. 2023

Smart Mater. Struct.

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Stick-slip rotary piezoelectric actuators (SRPAs) are commonly used nowadays. However, most of them achieve high velocity by high exciting frequency, which causes the problems of wide power-source passband requirement and the wear of actuators. Moreover, their further applications are limited, due to the poor motion stability caused by the backward motion. To solve the problems, the stick-slip process is analyzed with kinematics, indicating that the large step contributes greatly to SRPAs for achieving high velocity under low operating frequency and backward motion elimination. Then a large-step SRPA is proposed, fabricated, and tested. The experiments show that under the sawtooth signal with 100 V and 400 Hz, the prototype can reach a maximum velocity of 1.854 rad/s, benefiting from the large step (above 4.636 mrad). While other works require the exciting frequency of several kilohertz to reach the same level of velocity. Additionally, by increasing the step, the backward ratio decreases from 14.43% to 8.89% at the frequency of 1 Hz, and the minimum no-backward frequency decreases from 120 Hz to 60 Hz. The results indicate the effectiveness of the large step for solving the problems, which is significant for the design of SRPA.

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Development of a Resonant Scanner to Improve the Imaging Rate of Astigmatic Optical Profilometers

Cited by 4 publications

References 24 publications

Method for Film Thickness Mapping with an Astigmatic Optical Profilometer

Method for Film Thickness Mapping with an Astigmatic Optical Profilometer

Real-Time Reflectance Measurement Using an Astigmatic Optical Profilometer

A large-step stick-slip rotary piezoelectric actuator with high velocity under low frequency and small backward motion

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