Tetsuo Koezuka

Defect inspection technology for a gloss-coated surface using patterned illumination

In this paper, we discuss the development of an inspection system for a gloss-coated surface using patterned illumination. The convex defect on a gloss-coated surface is caused by top-coating paint on a primary coating with minute particles such as dust remaining. Since the convex defect is transparent, it is difficult to observe it in conventional illumination. Thus, we developed an optical system with patterned illumination and an inspection system using imaging technology with a phase-shifting method given the behavior of specular reflection on a gloss surface. The inspected surface is illuminated with the patterned illumination by shifting the phase of a stripe pattern, and a camera takes multiple images of the specular reflection. By calculating the amplitude of the luminance modulation according to a phase-shifting method, the amplitude image can be obtained from the multiple images. The amplitude image means the distribution of the reflectance. The scratch and dirt as well as small convex defects on a gloss surface can be observed in the amplitude image. This inspection system can make an image of the shape and specular reflectance on a gloss surface and allows inspection of gloss coating, which was difficult in the conventional method.

Automated optical passive alignment technique for PLC modules

We have developed an automated optical passive alignment technique for planar lightwave circuit (PLC) modules. Our technique is based on aligning a laser diode (LD) on a PLC module, and can be used to create an optical network unit. The PLC module we propose consists of a LD and a photodiode, which are mounted on the surface of the PLC platform without a lens. Because these elements send light directly to the waveguide on the PLC platform and receive light from the waveguide, a precise alignment technique is required. We therefore developed the mirror image alignment method in order to automatically align the LD on the PLC with extreme accuracy. The method is effective regardless of the position of the LD and the thickness of the solder. The mirror image method uses the markers on the PLC and their images, which are reflected on the front wall of the LD. The achieved accuracy for positioning was within 1 micron in the lateral direction and within 0.5 degrees in the rotational direction. These systems are now being used at a Fujitsu factory.

Automatic Pattern Recognition System With Self-Learning Algorithm Based On Feature Template Matching

A new self-learning technique has been developed to increase recognition efficiency and improve operability of an automatic pattern recognition system. The new algorithm can automatically make feature templates that emphasize the difference between similar patterns. This algorithm compares all the templates with each other by cross-correlating and picks out similar pattern pairs. The differences between similar patterns are extracted as the feature templates. This system can automatically carry out this procedure for 100 template patterns in 5 minutes.

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.

Visual inspection system using multidirectional 3-D imager

This paper describes a visual inspection system for factory automation. The system is based on a multi-directional 3-D imager. Three dimensional object recognition has become increasingly important in factory automation. For example, automatic assembly of printed circuit (PC) boards can use a 3-D visual inspection system to detect incorrectly assembled devices. To be effective, measurement should be done from more than one angle. A visual inspection system has been developed based on a multi-directional 3-D imager and laser cross scanning. It can obtain range and intensity information of objects simultaneously. Range measurement is based on laser triangulation using a position sensitive detector. The system features: (1) Multi-directional 3-D measurement. The quad 3-D imager and X-Y laser scanner enable multi-directional 3-D measuremenL (2) High-speed. Measurement speed is 1 million pixels per second. Each pixel contains data for 256-height-level range and 256-gray-level intensity. One quad flat package with 160 leads can be measured in 4 seconds. (3) High-resolution. The inspection resolution is 25 jim in the X and Y directions and 30 pm in the Z direction. The visual inspection system uses the 32-bit MC68030 and 12 megabytes of image memory. The system was capable of detecting missing, shifting, and floating leads, and solderjoint defects.

Wide-Area, High Dynamic Range 3-D Imager

This paper describes a 3-D laser scanning imager for visual inspection of mounted devices on printed circuit boards (PCB). A 3-D imager for this application must satisfy the following requirements: (1) It must be fast enough to sense a 250 by 330 mm area in 14 seconds; (2) It must have a measurement resolution of at least 125 gm; (3) It must be capable of measuring height and light intensity simultaneously; and (4) It must have an optical dynamic range of at least 10 4. We developed a wide-area telecentric scanning optical system which meets these requirements. It uses retroreflective triangulation optics and digital signal processing hardware. Our system scans a laser beam over a 256 mm length with a resolution of 125 μm, without scanning distortion. The retroreflection triangulation optics collect light reflected from objects on a printed circuit board and focus the image on a position-sensitive detector (PSD). This system measures the profile of objects with a vertical resolution of 30 μm, within a range of 7.6 mm. The digital signal processing hardware has a dynamic range of 10 4 and obtains range data from the output signals of the PSD. Its processing speed is 1M pixels/s. This hardware enables profile measurement of objects having a wide range of light reflectance (about 3000 times), from black devices to glossy metal, with an accuracy of 0.1 mm. This 3-D imager was used in an automated inspection system for PC board-mounted devices. This system detects missing, misplaced, and incorrectly installed devices with an inspection speed of 0.1 s/device.

Optical pickup adjustment system using a passive alignment method

The optical pickup of a magneto-optical drive is constructed of millimeter-size optical components, including a laser diode (LD), a collimating lens (CL), a polarizing beam splitter, some kinds of prisms, and photo detectors (PD). Each component must be assembled with micrometer-order accuracy. In particular, the astigmatism, which is adjusted by changing the position of the CL, must be within 0.65 micrometers in the optical axis direction. To enable the CL position to be adjusted quantitatively, we developed an adjustment method that uses passive alignment. We estimated the astigmatism by analyzing an image of the LD, which is acquired through the CL by illuminating the LD with the polarized light. We developed an optical-pickup adjustment system using the proposed method and tested its effectiveness experimentally. The results showed that this system can be used to adjust the accuracy to within 0.65 micrometers. Because the image of the LD and the PD are acquired clearly by this system, it should be useful for not only adjusting the optical pickup but also for visually inspecting the LD and PD.

An automatic adjustment system for the optical head of a magnetooptical disk drive

The authors developed a fully automatic adjustment system for mass production of the optical head for magnetooptical disk drives. The optical head is composed of small-sized (millimeter-scale) optical components, such as the laser diode, the collimator lens, the object lens, various prisms, and various detectors. In the assembly of the head, the positioning and fixation must be executed with an accuracy on the micrometer order, and the adjustment process is indispensable. Adjustment is a process where the object is iteratively measured and manipulated, and is finally fixed so that the specified performance is realized. A lens, for example, is moved, the shape of the convergence beam is observed, and the lens is then moved and fixed so that the beam takes the specified shape. Such an adjustment requires a considerable amount of time by an experienced worker, and has been one of the bottlenecks in the mass production of optical heads. The adjustment process for the optical head consists of adjustment of the optical axis of the laser diode, adjustment of the beam shape, and adjustment of the servo signal. The authors devised a series of adjustment algorithms composed of measurement, recognition, calculation of manipulation, execution of manipulation, verification, and fixation. They then developed the necessary techniques and installations that realize the algorithms. The key in the adjustment of the optical head is to process the measured value, to recognize the shape of the beam and the waveform, and to determine the manipulation, rather than simply using the measured value itself. Using the developed automatic adjustment system, the adjustment process, which requires approximately 9 minutes for an experienced worker, can be completed in about 6 minutes.

High-Seed 3-D Vision System Using Range And Intensity Images Covering A Wide Area

The 3-D vision system we developed uses laser scanning, and simultaneously produces range and intensity images covering a wide area. 3-D vision is indispensable in image processing for factory automation. Conventional, practical slit-light techniques using a TV camera have a limited narrow measurement area, take too long to accept input images, and cannot produce range and intensity images simultaneously. We developed a camera we call the 3-D imager and a vision system based on it. The 3-D imager uses a laser diode beam to scan the measured area and obtains range and intensity data at all points on the scan line. Range measurement is based on triangulation. The vision system, which consists of a 32-bit CPU (68020) and 12M-byte image memory, has three main features: (1) 3-D measurement covers 2048-by-3076-pixel image formed in one image input sequence. (2) Measurement is fast: The system takes 12 seconds to produce data for an entire 6-million-pixel area. (3) The system processes range and intensity data simultaneously. The 256-height-level range image is used to determine an objects shape, and the 256-gray-level intensity image to determine the surface texture, markings, and other features. When used to inspect PC boards, the system detected missing, shifted, and floating components. The inspection resolution is 125 pm in along the X and Y axes and 30 lam along the Z axis.

Print Quality Inspection System Based On Humar Response For A Wire Dot-Matrix Printer

A print quality evaluation method has been developed and applied to inspection of wire-dot matrix printers. Newly developed algorithms adopt human characteristics such as edge emphasis, logarithmic sensitivity in optic nerves, and progressive weighted total evaluation. Experimental results show that the capability of the print quality evaluation system is on the same level as expert operators and that reproducibility is three times higher.