Projection moire with moving gratings for automated 3-D topography

Halioua, Maurice; Krishnamurthy, Ravi S.; Liu, H; Chiang, Fu‐Pen

doi:10.1364/ao.22.000850

Cited by 81 publications

(22 citation statements)

References 15 publications

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“…Halioua et al (Halioua et al 1983) proposed a sensor system with double projection and an integral bucketing method for extracting only moiré patterns free of the inherent pattern noise due to the original gratings. The double projection is used to make the object illumination uniform and to reduce moiré fringe disappearance due to shadows.…”

Section: Previous Research Work Overcoming the Shadow Problemmentioning

confidence: 99%

Shadow-Free Moire Interferometer with Dual Projection for In-Line Inspection of Light Emitting Diodes

Kim

Koh

2007

International Journal of Optomechatronics

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In small-sized liquid crystal display markets, small light-emitting diodes (LEDs) are generally used for the illumination part of backlight units. For their uniform light-emitting, the volumetric size control of each pocket is crucial to the LED manufacturing process because the pocket fills with the transparent encapsulating material which plays a role in focusing the emitted light ray from the LED chip and protecting the LED wafer chip and wire-bonding. A special three-dimensional vision system is presented for volumetric inspection of the LED pocket with concave shape. Conventional measurement techniques of measuring the LED pocket easily produce noisy results due to the shadow probleminduced geometric configuration of the imaging part and pattern projecting part. In order to prevent this effect, the proposed sensor system utilizes a dual projection system. By using two measurement results acquired from pattern projections switching with different incident angles, shadow-free results can be acquired. In this article, we will describe the sensor system's principle and the sensor fusion algorithm combining two measurement results efficiently. A series of experiments is conducted to verify the performance of this proposed system. The measurements results show very satisfactory inspection performance and they are discussed in depth.

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Section: Previous Research Work Overcoming the Shadow Problemmentioning

confidence: 99%

Shadow-Free Moire Interferometer with Dual Projection for In-Line Inspection of Light Emitting Diodes

Kim

Koh

2007

International Journal of Optomechatronics

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“…Examples of such applications would be measuring waviness of sheet metal product or parts, or airfoil shapes. The methods of analyzing such phase step patterns has been well established [24][25][26][27][28][29][30][31][32][33][34] . The methods of dealing with the large amounts of data have not be solved on a global level to date, but specific application packages are becoming more available on the market.…”

Section: Triangulationmentioning

confidence: 99%

Latest optical methods for industrial dimensional metrology

Harding

2005

SPIE Proceedings

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Applying optical methods to a simple inspection problem, such as the presence or absence of an assembly component, is likely the least restrictive of any machine vision application. The setup, alignment, and components can be made very simply by using any feature which appears different if the component of interest is present. Gaging to verify proper construction, however, can be a much more complicated task. To take advantage of the capability of machine vision and other optical technologies, some flexibility in part position, orientation, and speed of presentation may be desired. This paper will review the types of methods available from optical methods for industrial dimensional metrology. The emphasis of the discussion will be 2D and 3D gaging applications.

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“…Another problem being common all to the phase shift methods is its susceptivity to the grating nonlinearity (deviation from sinusoidal cross section of transparency distribution) and phase-stepping error because the phase calculation is based on intensity values of the fringe. In the old moire techniques, this problem was avoided by continuously moving the projecting grating and another reference grating synchronously, and observe the interference fringes between them with long exposure time [7], [8]. With a single exposure of conventional image sensor, use of this technique is impossible or requires additionally an accurate and laborious mechanisms.…”

Section: Introductionmentioning

confidence: 99%

Spatio-temporal phase-encoding profilometry using correlation image sensor

Ando

2008

2008 IEEE International Symposium on Industrial Electronics

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In this paper, we propose a real-time 3-D shape measurement system which consists of 1) a moving fringe projector for spatio-temporal encoding (single frequency in time but different phase in space) of illumination angle, and 2) the three-phase correlation image sensor (3PCIS) which performs the synchronous detection and amplitude/phase demodulation of intensity-modulated light in real time on each pixel. The 3PCIS demodulates amplitude and phase of moving fringes in a scene frame by frame. Then, it is unwrapped in real-time to a sequence of projection angle maps based on an efficient use of spatial and temporal continuity of the phase maps. Compared with the phase-shift method using a color image sensor or a high speed camera, the system is shown to have novel characteristics; pixel by pixel capture of phase map in a single frame, freedom from environmental light sources and grayness nonlinearity of fringes, reduced sensitivity to object motion, etc. We implemented this system using CMOS 200×200 and 320×256 pixel 3PCIS recently developed by us.

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Projection moire with moving gratings for automated 3-D topography

Cited by 81 publications

References 15 publications

Shadow-Free Moire Interferometer with Dual Projection for In-Line Inspection of Light Emitting Diodes

Shadow-Free Moire Interferometer with Dual Projection for In-Line Inspection of Light Emitting Diodes

Latest optical methods for industrial dimensional metrology

Spatio-temporal phase-encoding profilometry using correlation image sensor

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