High-speed Three-dimensional Measurement Research Articles

Fast Volumetric Feedback under Microscope by Temporally Coded Exposure Camera.

We developed a temporally coded exposure (TeCE) camera that can cope with high-speed focus variations of a tunable acoustic gradient index (TAG) lens. The TeCE camera can execute a very short exposure multiple times at an arbitrary timing during one shot. Furthermore, by accumulating the photoelectrons generated by each exposure, it is possible to maintain the brightness even with a short exposure time. By synchronously driving the TeCE camera and the TAG lens, different focal planes of an observation target can be acquired at high speed. As a result, high-speed three-dimensional measurement becomes possible, and this can be used for feedback of three-dimensional information. In the work described in this paper, we conducted a focus tracking experiment to evaluate the feedback performance of the TeCE camera. From the experimental results, we confirmed the feedback capability of the TeCE camera.

High-speed three-dimensional measurement technique for object surface with a large range of reflectivity variations.

It is a challenge for any optical method to measure object surfaces with a large range of reflectivity variations. Dark or saturated regions on fringe images may lead to phase and measurement errors. At present, the main defect of the existing methods is the low measurement efficiency. This paper presents a high-speed three-dimensional (3D) measurement for object surfaces with a large range of reflectivity variations. First, we set the intensity of the projected fringes to the maximum, which ensures a better signal-to-noise ratio (SNR) of fringe images compared to the traditional methods. Second, in order to achieve high-speed projection, we transform 12 fringes with 256 gray-value cosine variations to binary fringes and defocus the digital light procession to filter out the higher harmonics. Third, since manually adjusting the camera lens or exposure time is much more time-consuming and not conducive to improving the SNR, we use the color light projection of the projector itself to get multiple groups of fringe sequences with different brightnesses. Finally, the final group of fringe images, used for 3D reconstruction, are formed by choosing the brightest but unsaturated corresponding pixels from multiple groups of fringe images. Experiments verified that the proposed method has the advantages of high-speed measurement, low cost in hardware, high measurement accuracy, a simple algorithm, and ease of extending to several applications.

1A1-I03 プロジェクターを用いた構造化ライトフィールドの投影による高速三次元計測

1A1-I03 プロジェクターを用いた構造化ライトフィールドの投影による高速三次元計測

Fabrication and integration of microprism mirrors for high-speed three-dimensional measurement in inertial microfluidic system

Inertial microfluidics utilizes fluid inertia from high flow velocity to manipulate particles and fluids in 3D. Acquiring a 3D information of particle positions and complex flow patterns within microfluidic devices requires 3D imaging techniques such as confocal microscopy, which are often expensive and slow. Here, we report on a prism-mirror-embedded microfluidic device that allows simultaneous imaging of the top and side view of the microchannel for a high-speed, low-cost 3D imaging. The microprism mirrors are fabricated and integrated into a microfluidic system using conventional microfabrication techniques including wet etch and soft lithography. This inexpensive high quality prism mirror provides a highly reflective, smooth mirror surface with precise 45° reflection angle, enabling 3D measurement of inertial migration of microparticles in a rectangular channel at speeds in excess of 10 000 frame/s.

High-speed three-dimensional measurements with a fringe projection-based optical sensor

An optical three-dimensional (3-D) sensor based on a fringe projection technique that realizes the acquisition of the surface geometry of small objects was developed for highly resolved and ultrafast measurements. It realizes a data acquisition rate up to 60 high-resolution 3-D datasets per second. The high measurement velocity was achieved by consequent fringe code reduction and parallel data processing. The reduction of the length of the fringe image sequence was obtained by omission of the Gray code sequence using the geometric restrictions of the measurement objects and the geometric constraints of the sensor arrangement. The sensor covers three different measurement fields between 20 mm×20 mm and 40 mm×40 mm with a spatial resolution between 10 and 20 μm, respectively. In order to obtain a robust and fast recalibration of the sensor after change of the measurement field, a calibration procedure based on single shot analysis of a special test object was applied which works with low effort and time. The sensor may be used, e.g., for quality inspection of conductor boards or plugs in real-time industrial applications.

High-speed three-dimensional measurement using electronically controlled wavelength-tunable ultrashort pulse fiber laser

A high-speed three-dimensional measurement system was demonstrated using an electronically controlled wavelength-tunable ultrashort pulse fiber laser and an all-fiber interferometer. A longitudinal scanning range of 2.8 mm and a scanning speed of 100,000 points/s were achieved without moving parts. For a measurement distance of 0.7 m, the sensitivity and accuracy were 70 dB and +/-8 microm, respectively. A clear three-dimensional image of a 100 yen Japanese coin was obtained using this measurement system.