A compact and cost-effective illumination platform was developed for a versatile optical inspection system to improve the detection accuracy of defects in glass substrates. The illumination device was developed in two phases, initially to demonstrate its feasibility for surface defect inspection in glass based on dark field images, and subsequently to optimize the design so it can provide multi-directional lighting and increase light scattering from defects on the substrate. Three LED arrays were installed above the substrate carrier and projected at an angle onto the glass substrate for the phase-I illumination device. Surface defects on the glass substrate were successfully reconstructed from images acquired by a line scanned CCD camera, but non-uniformity of defects intensity distribution on images was revealed. To optimize the illumination, two sets of tightly arrayed 3-watt LEDs were symmetrically installed at the entrance slit of the lens-camera module for phase-II illumination device. The inspection data were able to show clearer images of surface defects. The design issues such as poor contrast and sharpness of acquired images due to low scattering efficiency and non-uniform illumination were addressed as well. PCBs for the installation of the LED arrays and their power supply were also optimized. These were manufactured on aluminum substrate to help regulate heating of the inspection platform. This feature makes the system more compact, operable at low power, and easy for modification.
In the manufacturing process of flip chip packaging, the IC chip would be subjected to a temperature increase to roughly
150°C. With the rise of temperature, the chip is induced to a series of deformations which lead to possible malfunction of
the IC unit. Therefore, the investigation of in-line thermal deformation of the flip chip substrates in chip packaging
process is important. In this study the thermal deformation and surface profile of flip chip substrates under thermal stress
are simultaneously measured with a system composed of digital image correlation (DIC) and projection fringe
techniques. DIC technique is implemented to measure the in-plane deformation distribution and strain tendencies of flip
chip substrates while projection fringe method is used to grab the out-of-plane deformation and surface profile of the
substrates. Experimental results show that the warpage effect of the substrates is obvious when subjected to thermal
loading. Since the measurement system is very easy to be implemented, this combination of DIC and projection fringe
technologies maybe one of the most possible techniques for the growing need of in-line thermal deformation monitoring
in the production line of flip-chip packaging.
This paper presents a rapid inspection technique used for the evaluation of structures with line-width below
sub-wavelength and diffraction limit. Inspections are carried out with an optical microscope via a vertical scanning and
through-focus measurement, where the intensities of reflection light from different focal positions of the specimen are
transferred into a series of numeric data through the use of an Entropy algorithm. A through-focus focus metric (TFFM)
profile is then obtained for the inspection of line-width. The secondary peak in TFFM profile is related to the distance of
180° phase difference of the grating image according to the Talbot effect. This characteristic can be used to determine
the pitch of grating specimen. Based on the variance of the secondary peak for different line-width, the line-width of a
grating can be obtained from the comparison of simulated and measured data. Experimental results show that the
Entropy algorithm can be used to achieve more reliable and fast evaluation in line-width inspection. Furthermore, as
through-focus measurement is a non-destructive inspection method, it can be used as another positive element which
equals to a traditional nano-scale inspection methods, such as AFM and SEM.
With the rapid development of semiconductor technology the demand for high resolution measuring system is evolving
at an ever-increasing pace. Microscope was initially used to detect the defect by connecting charge couple device (CCD)
as an auxiliary device. In general, for microscopic measurement human eyes are used to focus on the sample. The
adjustment depends on the operator's astute measurement ability, which affected the repeatability and accuracy of the
readings. There is a need of high-speed microscope auto focusing system for industrial applications. The present
investigation describes about the development of an autofocus system to carry out microscopic measurement more
precisely and accurately with less time.
The measurement system consists of a light source, two beam splitters, a movable sample stage and a Mirau's
interferometer, a photo-detector and 8051 microcontroller (MCU89C51). The light reflected from the sample surface
interferes with the light reflected from the reference and produce an interference pattern, which is imaged onto a CCD
array. In the setup developed for the autofocus one extra beam splitter is placed in the path of interfered beam to the
CCD. The beam splitter is placed at equal distances from the CCD and the photodetector. The focus position is
determined from the voltage developed in the photo-detector due to the movement of sample stage of the microscope.
The maximum voltage that obtained at the focus position is confirmed with the CCD image. Microcontroller is used to
stop the controller at the focus position immediately once the sample stage reaches it. Software is developed to locate the
maximum intensity position. The design may autofocus the interferometer within 4mm distance in 1 second. The auto-focusing
not only provides enhanced repeatability and accuracy of the results at a faster rate but also minimizes operator
Rapid mixing is essential in biochemical analysis, drug delivery, biomedical inspection, as well as RNA and DNA synthesis and testing. A suitable evaluation method is required for mixing effect comparison in the stage of research and development of mixers. Until now, no satisfactory method was developed to quantitatively evaluate the mixing performance of micromixers. We describe an inspection algorithm that uses image gray level to evaluate the mixing effect in micromixers. Computer simulation results show that the mixed range and the mixing concentration can be recognized. Experiments are implemented in a self-designed two-channel micromixer, in which the diameter of the mixing chamber is 1 mm and height is 200 µm. Experimental results show that the proposed algorithm can clearly display the full-field mixing state in the mixer, so that it is helpful to evaluate the performance of a micromixer. In addition, a mixing efficiency over 90% is obtained within 0.35 s at a flux of 7.81 µl/s in the self-designed mixer. Since the purpose of rapid and uniform mixing is obviously achieved, this mixer can be applied to the field of biomedical diagnosis.
Rapid mixing is essential in many of the micro-fluidic systems targeted for use in the testing of biochip analysis, drug delivery, and analysis or synthesis of blood, among others. A design of a passive micro-mixer is presented in this paper. The mixing is based on the vortex phenomenon of fluid stirring and diffusion. The size of the mixer chip is 10mm×10mm, with a width of the channel of 200μm and a depth of 50μm. This mixer allows fast mixing of small amounts of liquids. A mathematical model that uses gray level contrast to evaluate the mixing efficiency is also proposed. The measurement principle is based on the statistical concept via a quadratic weighting distribution. Experimental results show that the mixing efficiency is over 80% for mixing two liquids with the same polarization and roughly 90% for the mixing of two inks. Thus a new type of biochip can be easily implemented with this system for the application in biomedical diagnostic technology.
Images of light distribution in biological soft tissue we used to study the optical characteristics of tissue. The light distribution image was taken under a microscope with light injected through a pinhole close to the edge of the top surface. Images taken on skin, fat, and muscle tissues were compared to study the effect of cellular structure and temperature on the light intensity distribution. Monte Carlo simulation with the same conditions was also performed to simulate the light intensity distribution in tissue for comparison. The anisotropy scattering of light in tissue is affected by the tissue microscopic structure, such as the direction of muscle tissue fibers. The change in optical properties of fat and muscle tissue with temperature was observed. The two-dimensional light distribution images offer more information than general reflectance and transmission measurements. By matching the simulated light intensity distribution with the light distribution image, the optical properties of biological tissue could be estimated. This method might be applied in tissue engineering as an economic way for evaluating the microscopic structure of tissue.
A new approach to automatic 3-D shape measurement is presented and verified by experiments. This approach, based on neural network theory, can automatically and accurately obtain the profile of diffuse 3-D objects by using a projected laser stripe. When the laser stripe is projected on an object, the line image of the laser light is grasped by a CCD camera. Using neural network theory, a relationship between the laser stripe image in the CCD camera and the related absolute position in space can be established. Thus the spatial coordinates of a measured line image in a CCD camera can be obtained according to the output value of the neural network. By processing a series of laser line images from the discrete angular positions of an object, a complete 3-D profile can be reconstructed. Theoretical analysis and experimental systems are presented. Experimental results show that this approach can determine the 360-deg profile of an object with an accuracy of 0.4 mm.