Browsing by Author "Weng, Chun-Jen"

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Auto-focus pathology microscope using sub-array sampling
(2019-01-01)
Wu, Po-Hsun
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Weng, Chun-Jen
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Chen, Pi-Ying
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機械工程學系
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Department of Mechanical Engineering
this study compared the focusing results of binning and sub-array methods with the aim of balancing speed and accuracy. Analysis was conducted using an autofocus system comprising a microscope, CCD, PZT actuator, LED light source, and two focus algorithms. Our results showed that by selecting an image sub-array of appropriate size and shape, it was possible to reduce the time required for autofocus operations to only 1 second, while maintaining the focusing accuracy of full-field analysis techniques.
Broadband Microspectrophotometer with Tablet PC Control
(2012)
Weng, Chun-Jen
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Hsu, Ken-Yuh
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Chen, Yung-Fu
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Chang, Shian-Wen
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Cho, Wen-Hao
This study investigated the design, fabrication, and performance characterizations of a broadband microspectrophotometer with tablet PC wireless control. The microspectrophotometer system performed rapid measurements, was highly accurate, and was easy to operate. The calibrations for two measurement modes for transmittance and reflectance spectra were performed with bulk and multilayer thin-film samples. Objective lenses with various magnifications were introduced to verify the possibility of microscopic spectra measurements in the system. A polarization identification capability was also included in the system.
Compact motorized circular wheel of polarization optics for ultra-broadband polarization state generation
(2012)
Weng, Chun-Jen
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Liu, Da-Ren
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Hsu, Ken-Yuh
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Chen, Yung-Fu
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光電工程學系
This study proposes an innovative optical mechanism with a miniature motorized circular wheel for polarization optics for an ultra-broadband polarization state generator. The proposed apparatus can be suitable for a polarimetric microspectrophotometer for measurements of micro optics and metamaterials with circular dichroism and linear dichroism. Different types of micro optics have their own wavelength dependence, meaning different curves in the broadband range of light. This study presents an ultra-broadband platform for measuring and identifying micro optics such as chiral metamaterials, plasmonics, micro polarizers, and patterned retarders. The key component of a polarimetric microspectrophotometer is a polarization state generator (PSG). A simple PSG consists of a polarizer and a waveplate. An arbitrary polarization state can be created by rotating either the polarizer or the waveplate. Sheet polarizers and achromatic waveplates have a limited bandwidth range. For the ultra-broadband measurement range of 400 nm to 1700 nm, the PSG needs at least three sheet polarizers and three achromatic waveplates: 400 nm-700 nm, 700 nm-1000 nm, and 1000 nm-1700 nm. This optical mechanism, which consists of only one control motor and two high precision unidirectional bearings, includes several polarizers and waveplates arranged in a matrix on a circular wheel. This apparatus can shift one of the polarizers and waveplates to a predetermined position and rotate all the polarizers to change the polarization status. An ultra-broadband polarimetric microspectrophotometer with a compact motorized wheel is an advanced polarization optical instrument for research on chiral metamaterials, plasmonics, micro polarization optics, green optics, and bio optics.
Confocal displacement sensor with varifocal lens
(2015)
Weng, Chun-Jen
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Lan, Tzu-Hsien
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Hwang, Chi-Hung
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Liu, Da-Ren
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Chen, Chih-Yen
a confocal displacement sensor with a varifocal lens and a multi-wavelength rainbow laser was established in this study. The surface curvature of varifocal lens was varied by different current driving so that the focal length can be easily changed. Thus, we can quickly measure the distance between the sensor head and targets by detecting the reflective power according to the principle of confocal laser. This rainbow laser can operate at four different wavelengths. The laser beams with different colors can be used to measure the dispersion of varifocal lens. The range of measuring displacement with 20X objective lens in this displacement sensor is from 4.9mm to 5.9mm. The FWHM resolution of displacement is about 70 mu m. The step-height aluminate plate was measured by this system and the error of measuring distance is less than 35 mu m (0.75%).
Developing a microspectrophotometer to measure the dependence of broadband refractive indices on Ge-doped concentrations in GRIN rods
(2015-11-30)
Weng, Chun-Jen
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Hsu, Ken-Yuh
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Lee, Cheng-Yeh
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Chen, Yung-Fu
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電子物理學系
A confocal microspectrophotometer is utilized to scan the surface reflectivities of a polished gradient-index (GRIN) rod in the range of 400 to 900 nm. The pure fused silica is used to be a reference standard for deducing the absolute reflectivities of the Ge-doped core. Then, multi-wavelength refractive index profiles of the Ge-doped core can be further determined based on the Fresnel equation. Moreover, this work shows a connection between the material dispersion of the GRIN rod and the Gedoped concentrations measured by an energy dispersive spectrometer. Finally, the dependence of the refractive index of the Ge-doped core on the doping concentrations at a certain wavelength can be easily expressed as a linear form. (c) 2015 Optical Society of America
Exploiting the image of the surface reflectivity to measure refractive index profiling for various optical fibers
(2015-05-04)
Weng, Chun-Jen
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Hsu, Ken-Yuh
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Chen, Yung-Fu
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電子物理學系
;
光電工程學系
A direct image method of surface reflectivities on a cleaved fiber end with a filtered halogen lamp and a TE-cooled CCD with high dynamic range is proposed to measure the multi-wavelength refractive index profiling (RIP). A polished black glass is used to be a reference standard for measuring the absolute reflectivity of the fiber end. With the developed calibration procedures, both the spatially dependent sensitivity and spectral responsivity of the CCD pixels can be eliminated to achieve the high spatial accuracy. Tested fiber is connected with a fiber terminator to prevent errors from the backside return light. With the present method, the RIP can be precisely measured for not only multi-mode fibers but also single-mode fibers. (C) 2015 Optical Society of America
Measuring the thickness of transparent objects using a confocal displacement sensor
(2017-01-01)
Weng, Chun-Jen
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Lu, Bo-Rong
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Cheng, Pi-Ying
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Hwang, Chi-Hung
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Chen, Chih-Yen
this paper reports on a confocal displacement sensor with varifocal lens used to measure the thickness of transparent materials. The focal length of the varifocal lens is adjusted by varying the current. Laser light passing through a transparent target lying within the range of the focal length crosses two interfaces; i.e., first from air to glass and then from glass to air. The signals associated with the interface were of higher intensity than that measure at other points along the z axis. A power meter is used to measure the power and LabVIEW is used to record a power-current graph. The current gap between the two peaks can be translated into values of displacement, indicating the thickness of the material.
Rapid displacement sensor based on fitting scan
(2016)
Ye, Zheng-Jie
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Hwang, Chi-Hung
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Cheng, Pi-Ying
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Chen, Chih-Yen
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Weng, Chun-Jen
A rapid displacement sensor with a varifocal lens based on a method of fitting scan is proposed for 3D surface profiling. The focal length of the varifocal lens can be adjusted by varying the driving current. By detecting the reflective power of the reflected laser, the displacement can be obtained. By integrating a LabVIEW program based on a Levenberg-Marquardt algorithm in this system, the measuring speed can be substantially improved. Finally, the 3D surface profile of a step-height sample was successfully scanned by this displacement sensor.
Real-Time Image-Based Defect Inspection System of Internal Thread for Nut
(2019-08-01)
Lin, Chun-Fu
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Lin, Sheng-Fuu
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Hwang, Chi-Hung
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Tu, Hao-Kai
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Chen, Chih-Yen
The most important components of the internal nut thread inspection process are measuring the pitch and pitch diameter value and comparing these with their respective specifications, as a test nut is considered to be abnormal when its pitch or pitch diameter does not meet specifications. This paper focuses on defects arising when the pitch diameter does not meet its specification. Because conventional contact strategies are not suited to the real-time inspection of internal thread defects, there have been a number of recent attempts to develop noncontact methods for real-time measurement. Some approaches have applied laser triangulation techniques in which reflected light is used to measure the z-axis depth on an object's surface. Although point lasers have been shown to be highly precise in measuring pitch diameter, the optical architecture involved in these approaches is complicated and, as the laser must be scanned in a pointwise manner to derive cross-sectional measurements, the measurement process is too long to be compatible with real-time defect inspection. In this papere, an image-based method employing a line laser projector was used to develop a real-time image-based nut pitch diameter defect inspection system. The proposed method, which improves upon the conventional, widely used template-matching method for rapid defect detection, was shown to be effective through experimental validation.
Surface profiling of object using varifocal lens with image contrast
(2019-10-01)
Chen, Chih-Yen
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Wang, Lijuan
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Fan, Chen-Liang
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Cheng, Pi-Ying
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Weng, Chun-Jen
The measurement of automated and fast focusing on the improvement of speed and accuracy is an important issue in industrial inspection and biomedical microscopy. In this study, we developed a novel optical imaging system in which varifocal lenses are used to characterize the 3D surface topography of samples. The performance of the proposed system was evaluated using twelve focusing algorithms. Experimental results demonstrate the feasibility and effectiveness of the proposed system in the near real-time construction of multi-focus fusion images with large depth of field from which to derive 3D surface profiles.
Tunable fiber confocal sensor with LED
(2015-01-01)
Weng, Chun-Jen
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Lan, Tzu-Hsien
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Hwang, Chi-Hung
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Chu, Nien-Nan
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Huang, Chien-Yao
A novel concept of confocal sensor based on focal lens is proposed to measure the displacement. The light source is a stabilized fiber coupled LED. A 1x2 graded-index multimode fiber optic coupler is used in this sensor. One port is a LED input port via SMA connector, another port is a LED output port connected to a reflective collimator and the other port is a reflective sensor port connected to a photo detector. The focusing sensor head is the cascade of a focal lens and a 20X objective lens. In this confocal displacement sensor, LED passes through a focal lens and an objective lens so that the LED beam focuses at a fixed focal point. A test target is placed after the objective lens. The displacement between the sensor head and a target can be measured quickly by detecting the reflective power according to the confocal principle. The long-term stability of LED is under 0.5%. The effective back focal length is varied from 5.67mm to 6.57mm by 0-290mA current driving so that the measuring range is about 0.9mm. The FWHM resolution of displacement is about 50 mu m. This sensor has the features of low cost, high stability, high precision and compact.