Three-dimensional shape measurement using focus method by using liquid crystal grating and liquid varifocus lens

Mizutani, Yasuhiro; Kuwano, Ryoichi; Otani, Yukitoshi; Umeda, Norihiro; Yoshizawa, Tôru

doi:10.1117/12.633147

Cited by 10 publications

(3 citation statements)

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“…Another way to extract depth information from optical focusing characteristics is to indirectly measure the size of defocus blur at each pixel [9][10][11][12][13][14][15][16][17][18][19]. Unlike focus which is a binary property (a point is either in-focus or not), defocus is related to amount of light spot spread on the detector which is a measurable scalar.…”

Section: Depth From Defocusmentioning

confidence: 99%

“…A computational algorithm then shifts through the elemental image set and calculates/estimates the depth information for each pixel given the image acquisition model for each elemental image. Among the methods in this category are stereo imaging, depth-from-focus/defocus [6][7][8][9][10][11][12][13][14][15][16][17][18][19], shape from silhouette [20] and integral imaging profilometry [21], to name a few.…”

Section: Introductionmentioning

confidence: 99%

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Application issues in the use of depth from (de)focus analysis methods

et al. 2011

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Recovering 3D object information through analyzing image focus (or defocus) has been shown to be a potential tool in situations where only a single viewing point is possible. Precise modeling and manipulation of imaging system parameters, e.g. depth of field, modulation transfer function and sensor characteristics, as well as lighting condition and object surface characteristics are critical for effectiveness of such methods. Sub-optimal performance is achieved when one or more of these parameters are dictated by other factors. In this paper, we will discuss the implicit requirements imposed by most common depth from focus/defocus (DFF/DFD) analysis methods and offer related application considerations. We also describe how a priori information about the objects of interest can be used to improve performance in realistic applications of this technology.

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Section: Depth From Defocusmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Application issues in the use of depth from (de)focus analysis methods

et al. 2011

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“…Su et al [ 5 ] proposed a method to shift the projector along the projection axis and calculate the modulation of all the pixels on the object with phase-shifting. Y. Mizutani et al [ 7 ] used a varifocus lens, whose focus length can be continuously varied from a concave to a convex shape by changing the liquid pressure. Jing et al [ 8 ] combined an EF projection lens and DMD grating to realize a high flexible focus change process, which is also used in the recent work [ 9 ].…”

Section: Introductionmentioning

confidence: 99%

Uniaxial 3D Measurement with Auto-Synchronous Phase-Shifting and Defocusing Based on a Tilted Grating

Hui

Liu

Wang

et al. 2021

Sensors

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Conventional uniaxial techniques generally require shifting objects or projection grating with the assistance of a high-precision mechanical moving component. To overcome this limitation, we propose a novel uniaxial 3-D shape measurement system with auto-synchronous phase-shifting and defocusing by using a tilted and fixed projection grating. The tilted focused image plane (FIP), which is reflected by a mirror at about 90 degrees, could be shifted across the measured surface by slightly rotating the mirror within a small angle range. This procedure will simultaneously introduce the change in defocusing and phase-shifting of the fringe. The modulation curve of each point can be deciphered by Fourier fringe analysis after a sequence of fringe intensities is acquired. Since both the measured object and projection grating are fixed, the proposed method could make the measurement system more compact and flexible. Both computer simulation and experiments are carried out to demonstrate the validity of this proposed system.

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