Moritoshi Ando

Aberration corrections for a POS hologram scanner

Use of an optically generated IZP (interferometric zone plate) hologram scanner enables highly accurate reading in a supermarket point-of-sale (POS) label reader with a simple optical arrangement. The laser beam spots on the scanning plane which construct the lattice scan pattern designed for the POS label reader cause severe aberrations when a conventional IZP hologram is used. A simple and effective method for removing the aberration is discussed from both the theoretical and experimental aspects, and the feasibility of the method is demonstrated. This method employs oblique-angle coherent plane-wave illumination in the IZP hologram recording process.

Automatic opitcal through hole inspection method for printed wiring boards using leakage light detection

New automatic through hole inspection techniques for printed wiring boards (PWBs) were developed. The new method called Leakage Light Detection can detect defects such as cracks and breaks in plating of through holes with aspect ratio as large as ten. A prototype system for automatic through hole inspection is constructed, based on these techniques. This system detects defects in a 250 mm × 250 mm area of a PWB in 8 minutes.

Automated high-throughput micro-injection system for floating cells

We have developed an automated microinjection system that captures many floating cells and controls capillary positions precisely. To capture many cells simultaneously, we constructed an array of holes on a 10 x 10 mm silicon-based substrate. The hole diameter is 3 μm because our target cells are 10 - 20 μm in diameter. A suction pump connected to the bottom of the multi-hole silicon chip draws the medium into the holes using a slight vacuum, so cells are caught there. Using an initial prototype chip having 121 holes, we captured over 90 cells in a single sweep. Automated microinjection requires precise control of the capillary positions, so images of the capillary and holes on the chip are observed using a microscope with a CCD camera located above the biological medium. The 3D positions of these elements are accurately measured by processing these images. The capillary and the chip are mounted on automatic stages individually controlled with this position data. Using these techniques, this system can microinject about one cell per second. Its success rate for microinjection is 61% for PC12 cells.

High-speed solder bump inspection system using a laser scanner and CCD camera

We have developed technologies which inspect the shape of solder bumps. The bumps are used to solder an LSI to a printed wiring board in high-speed workstations. The inspection system developed can measure the height, diameter, and brightness of bumps at very high speed. The bump height is measured using triangulation, in which a laser beam scans the bumps, and reflected light is detected with a position sensitive detector (PSD). The diameter and the brightness are measured using a microscope and a CCD camera. The detected results are compared with CAD data. A height measurement accuracy of ±3 μm and a diameter measurement accuracy of ±5 μm were obtained. Practical inspection systems using these techniques have been created and they can inspect 2000 bumps in 60 seconds.

High-speed 3D inspection system for solder bumps

This paper discusses a high-speed 3-D inspection system for solder-bumps. The system uses a high-speed 3-D sensor system and an accurate measurement algorithm. Solder-bumps have recently been used for flip-chip bonding. Before bonding all bumps need their height and diameter inspected and if bumps are too big or too small, there is a danger of short or open circuits occurring after bonding on the substrate electrodes. Thus, a 100% inspection is required to assure high flip-chip bonding process yields. We developed a laser-based high- speed bump height capture system and an accurate bump height and diameter measurement algorithm. The inspection system takes 20 milliseconds to measure the height and diameter of a bump. It measures the bump height to an accuracy of plus or minus 3 micrometer, and the bump diameter to plus or minus 5 micrometer. Thus, this system is suitable for performing a 100% inspection of solder-bumps.

Automatic optical inspection of plated through-holes for ultrahigh density printed wiring boards

An automatic optical through-hole inspection system for ultrahigh density printed wiring boards (PWBs) using leakage light detection has been developed. To detect the dim leakage light emitted from the through-hole defect, we enhanced the sensitivity of the light detector 150 times using a microchannel plate tube. However, the tube caused two problems: stray light sensing and image distortion. To solve these problems, we optically isolated the sensing optics and developed a distortion correction method. We have developed a prototype system that can detect a defect as small as 100 μm.

Automated microinjection system for adherent cells

We have developed an automated microinjection system that can handle more than 500 cells an hour. Microinjection injects foreign agents directly into cells using a micro-capillary. It can randomly introduce agents such as DNA, proteins and drugs into various types of cells. However, conventional methods require a skilled operator and suffer from low throughput. The new automated microinjection techniques we have developed consist of a Petri dish height measuring method and a capillary apex position measuring method. The dish surface height is measured by analyzing the images of cells that adhere to the dish surface. The contrast between the cell images is minimized when the focus plane of an object lens coincides with the dish surface. We have developed an optimized focus searching method with a height accuracy of ±0.2 um. The capillary apex position detection method consists of three steps: rough, middle, and precise. These steps are employed sequentially to cover capillary displacements of up to ±2 mm, and to ultimately accomplish an alignment accuracy of less than one micron. Experimental results using this system we developed show that it can introduce fluorescent material (Alexa488) into adherent cells, HEK293, with a success rate of 88.5%.

Advanced pattern inspection using Macroview

The new pattern inspection algorithm we developed detects fatal defects on printed wiring boards. The algorithm determines whether patterns identified by an automated pattern inspection (AOI) system are actually defective by considering the electrical malfunction that the defect will cause. A macroscopic model based on the pattern design rules and their tolerances to pattern violations is needed to evaluate defects. The algorithm classifies features around a defective pattern into 50 categories and compares the defect distribution with preset check rules. The automated optical verification system we developed captures pattern images with a CCD camera and uses verification software to evaluate defects. The process takes 10 seconds per image. We tested the system on the factory floor, and it detected all defects with less than 4.8 percent of false alarms.

I/O pin solder-point inspection system

We have developed an automated inspection system that features perpendicular and variable- intensity lighting for image contrast enhancement and improved sensing accuracy, a high- resolution camera with reflection-adaptive binarization for improved image processing, and an adaptive inspection algorithm that modifies its defect definition criteria according to target position quickly, accurately, and reliably inspects highly dense arrays of perpendicular I/O pins soldered onto a ceramic printed wiring board (PWB). The systems Mega-Scope, a high- resolution, eight-bit gray-scale CCD camera, images a 2048 X 2048-pixel area with a 10 micrometers resolution in 4 seconds, taking 60 I/O pin images at a time. The total time to inspect the position and solder fillet condition of more than eight thousand I/O pins is just 30 minutes.

Automated Optical Pattern Inspection For High-Density Printed Wiring Boards

A new technique for automated optical inspection of printed wiring boards (PWBs) has been developed. It uses black line sensing and a radial matching algorithm. The sensing method uses black line illumination and a CCD line sensor. The PWB is brightly illuminated except for the area under observation. Because the PWB substrate is translucent, copper patterns are sensed as shadows and their color and roughness do not affect the sensing. The inspection algorithm describes the copper pattern with binary codes. The pattern width is measured radially in four directions from the pattern centers. A combination of length and direction is encoded in a 12-bit binary code. Codes are assembled and make up a dictionary. The method can be used to inspect many kinds of patterns by changing the contents of the dictionary. An inspection system using this technique has a 5-μm resolution and can inspect a 490 x 540 mm area in 5 minutes.