Hidekazu Sekizawa

Defect-type discriminating optical system

Novel coherent optical defect detecting methods, which can distinguish between opaque defects and transparent defects, are proposed. One of these novel methods makes use of a holographylike polarity reference signal and is suited to automatic detection systems. The other employs two independent light sources, and suitable for visual detection systems. Realizing these novel methods using omnidirectional spatial filters, simple but effective periodic pattern defect-detecting systems are formed, which can be easily accommodated with defect touching-up stages.

Rotation-, shift-, and magnification-insensitive periodic-pattern-defects optical detection system

Defects in rectangular x-y axis decomposable periodic patterns are found to be detected by an omnidirectional (r-theta axis decomposable) spatial filter optical system, where use is made of the spectral difference between periodic patterns and defects. A novel omnidirectional spatial filter, which has bandpass characteristics, is designed to block all the repetitive periodic regular pattern spectra and pass the defect information carrying spectra. According to a computer simulation, the minimum detectable defect size using this optical system is about one-twentieth that of the periodic pattern pitch. This novel optical system is characterized by its ability to detect defects at any location and rotation (shift and rotation immunity of the optical system) and also to be insensitive to object magnification by the frequency domain operation characteristics. This filter application is not limited to 2-D rectangular periodic-pattern-defects detection, but defects in 1-D or skew periodic patterns are also detected by the same filter.

Disk-memory pregroove inspection.

An optical inspection system has been developed that detects parameter fluctuations in an optical disk pregroove structure (groove pitch, depth, and width). This optical system was devised using a laser diffraction phenomenon. Groove parameters are measured and calculated from diffracted-light intensity ratios; the groove width is calculated from the second-order diffracted-light intensity ratio to that for the first order. The groove depth is given from the first-order ratio to the zeroth-order light intensity. In addition to this groove parameter inspection, this system is capable of groove defect detection using a spatial filter whose passband is designed to be between the zeroth- and the first-order diffracted-light areas.

Periodic aperture size measurement with submicron accuracy: application to nonuniform detection in color CRT shadow masks

A novel periodic aperture size measurement optical system, which makes use of a coherent light beam/lens 2-D Fourier-transform property, is proposed. Measuring gain and errors is discussed. This optical system is able to produce aperture widths on a 3-D formed surface with the same accuracy as those on a flat surface and is well suited for measuring small aperture size variations in shadow masks for color TV tubes. These variations in shadow masks are considered to cause luminous and color nonuniformities and have been detected heretofore only by visual inspection. The minimum detectable size variation for this new measuring method is ~0.1 microm.

Scalable resolution transformation by outlining with approximated B-spline curve

This paper presents a developed resolution transformation method which achieves scaleable resolution transformation of bi-level images with high image quality, real-time processing and small circuitry. The progress of networked multi- functional hard-copy products for printing images from various sources such as facsimile machines, PCs, scanners and digital cameras, which have various resolutions, has created an urgent need for scaleable resolution transformation with high image quality. The proposed method applies outlining and rendering to scaleable resolution transformation. Furthermore, it minimizes the size of the circuitry by modifying their algorithms. Outlines are generated from the bi-level bit map of the source image by fitting approximated B-spline curve upon edge pixels. The bi-level bit map image which has a different resolution is generated from the outlines with local rendering. Curve fitting of approximated B-spline curve and local rendering makes it possible to reduce the circuitry. As a result, real-time scaleable resolution transformation of high quality is achieved with small circuitry. The quality of images transformed from 200 dpi to 600 dpi by the proposed method is almost equivalent to a genuine 600 dpi image.