We present a fast method for measuring a curved specular surface defect, which is the temporal modulated deflectometry. The system uses correlation image sensor, which is developed by us. The correlation image sensor(CIS) outputs temporal correlation between intensity signal and reference signal. We moves rectangular pattern to generate temporal signal. There is no need to use sinusoidal intensity pattern for phase measuring deflectometry(PMD) because CIS captures only fundamental frequency component of rectangular wave projected on the screen. Hence, the methodology we proposed has a potential for fast inspection system using only single frame.
These days there are many real-time 3D measurement systems. Those method has finite exposure time, therefore
the motion blur is inevitable in principle. We developed a motion deblurring technique in surface orientation
images using a correlation image sensor for 1D movement by belt conveyor. This imaging system consists of
two components; one is ring-shaped modulation illumination for encoding surface orientation into the amplitude
and phase of the reflected light intensity, and the other is the three-phase correlation image sensor (3PCIS) for
demodulating the amplitude and phase of reflected light. The higher spatial frequency components which is lost
by motion are captured by modulation imaging using correlation image sensor. The reconstruction algorithm
is proposed for modulation imaging picture which is complex value image representing surface orientation. We
applied wiener filtering method, and then still normal vector image is successfully reconstructed.
KEYWORDS: 3D metrology, Image sensors, Projection systems, Spatial frequencies, 3D image processing, Signal attenuation, Imaging systems, 3D modeling, Modulation, Cameras
We propose 3D profilometry based on depth from defocus of the projection system with the same axis of imaging
system. In this system, the stripe pattern generated by DLP Light commander is projected on the object,
and it moves on object's surface generating temporal variation of the light intensity. The projected stripe
pattern is defocused depending on its distance from the focal plane. By moving the stripe pattern, defocused
spatial frequency component is captured by temporal frequency analysis. We use correlation image sensor
(CIS) to capture the temporal frequency component in a single frame. CIS outputs the Fourier coefficients of
incident light in each pixel for every frames, and therefore it enables single frame 3D measurement. Evaluation
experiments show that projection defocus depends on the distance from the focal plane, and it can be used for
3D measurement.
We propose a novel and extremely efficient scheme of 3D-Particle Image Velocimetry (3D-PIV), simultaneous
time-stamped and depth-stamped imaging, using correlation image sensor (CIS) and a structured illumination.
In conventional PIV measurements, 3-D positions of numerous tiny particles inserted in a fluid field must be
detected using multiple high-speed cameras. Resultant huge amount of data volume increases the computational
cost and reduces the reliability of velocity field estimation. These problems can be solved if a single-frame 4D (3D
position and time) trajectory imaging can be realized. The CIS developed by us is the device which outputs the
temporal correlation between incident light intensity and two sets of three-phase (3P) reference signal common for
whole pixels. When particles are imaged in a frame using a 3P reference signal, CIS records the time information
as a phase distribution along their trajectories. CIS can also capture the depth information by exploiting the
structured illumination and another 3P reference signal. Combination of these methods provides the time- and
depth-stamped imaging. We describe the principle, theoretical foundations, and analysis algorithms. Several
experimental results for evaluating accuracy and resolution are shown.
We propose a new out-of-plane vibration imaging technique for
micro-structured solid-state devices such as MEMS (microelectro mechanical systems) microphones and resonators. This technique is based on the longitudinally scanning optical interferometry and an integrated image sensor device which we call the correlation image sensor (CIS). The CIS is able to extract an arbitrary frequency component from time-varying incident light and produce a complex correlation image including amplitude and phase in addition to a conventional intensity image. In heterodyne interferometry of vibrating objects, the vibration information is encoded in several frequency components generated by mutual modulation of longitudinal scan and vibration. In this paper, the combination of newly developed multi-channel CIS and the scanning heterodyne technique enable us to obtain the multiple frequency components simultaneously and reconstruct the vibration amplitude and phase distributions in real time. As an example, vibration modes of a MEMS acoustic sensor are shown to be rconstructed at video rate. A theoretical possiblitiy for the imaging of higher than GHz vibration combining other optical heterodyne techniques is also discussed.
The optical flow computation has been widely studied motivated by a broad range of applications. We proposed a solution base on optical identity (OFI) using Correlation image sensor (CIS). If the frequency of the CIS' reference signals is ill-chosen, the SNR of the amplitude of the complex correlation image is small, and it is difficult to solve OFI stably. When we choose the frequency of the sinusoidal reference signals "w" satisfies "wT=2n Pi" the optical flow identity (OFI) holds, where "n" is an integer, "T" is the frame time of the CIS, and "Pi" is the circle ratio. We define "G(w)" satisfying "wT=2nPi" by the sum of the amplitude of the complex sinusoidally modulated image over all pixels, and maximize it to give a solution of the frequency-tuned problem.
In this paper, we propose a new measurement scheme,
called phase-stamp imaging using correlation image sensor(CIS).
The correlation image sensor,
developed by us, is the device which outputs the temporal
correlation between incident light intensity and
three reference signals which is common among whole pixel.
By using the correlation image sensor
with the single frequency reference signals,
the time at which light spot is getting through
is embedded in the form of the phase of the reference signals in each pixel.
It provides single frame high resolution measurement of the 2D velocity field,
and also good time resolution for transient phenomenon.
We apply this scheme to fluid flow measurement.
We show some experimental results and confirmed its performance.
Multi-axis displacement sensing technique with a single optical beam is proposed. Our system consists of propagating optical vortex beam and its imaging system. Since optical vortex beam have feature points known as zero-points or phase singularities in its beam profile,
we can detect lateral and rotational displacement of the beam precisely by imaging and tracking the points. Unlike conventional laser displacement sensing techniques, our measurement scheme can be applied for the deformation sensing of civil infrastructures such as bridges and highways where triangulations can not be applied.
The basic optical setup is presented and the results of the fundamental experiments are shown.
In this paper,we study optical flow determination with Complex Sinusoidally Modulated Imaging (CSMI) using a novel imaging device, the correlation image sensor (CIS). The proposed method is based on a newly obtained relation what we call the optical flow identity (OFI) between intensity image and complex inusoidally-modulated image captured simultaneously by the CIS. This equation is complex-valued and the optical flow is a 2-dimensional vector for each pixel. Therefore, it is possible to compute the optical flow from one pixel value and its spatial gradient. Since the OFI does not involve time derivative, information on a single frame is sufficient. Moreover, the velocity limitation due to the spatio-temporal aliasing and approximate frame differentials used in conventionalt methods is avoided.
We propose a new method of the surface orientation (normal vector) imager being independent upon non-Lambertian reflectance components.
It consists of six light sources at vertices of a hexagon and the three-phase correlation image sensor (3PCIS) for demodulating the amplitude and phase of reflected light at two illumination modes. To separate the Lambertial and the specular reflectance components, the light sources first illuminate the object in six phases being different in 2π/6 between the neighbors (the dipole modulation mode) and then in three phases being different in 4π/6 each other
(the quadrapole modulation mode). In the dipole modulation mode,
the amplitude and phase depend both on the Lambertian reflectance (surface orientation) and on the non-Lambertian reflectance (specular strength). In the quadrapole modulation mode, the former component is eliminated and only the latter component remains. Subtracting it from the dipole modulation result, we obtain the surface orientation map based on the photometric stereo principle. We implemented the method using CMOS 64x64 pixel 3PCIS and successfully reconstructed the normal vector maps for various non-Lambertian object.
We propose a novel system for real-time three-dimensional surface orientation measurement. The advantages of our method are: (1) single frame capture of normal vector distribution, (2) dense, pixel-wise capture of normal vectors, and (3) independence on surface reflectance and background illumination. This system consists of two components; one is the sinusoidally amplitude-modulated three-phase (3P) light sources at vertices of a triangle and another is the three-phase correlation image sensor (3PCIS) for demodulating the amplitude and phase of reflected light from the surface. Based on the photometric stereo principle, the phase and amplitude can be easily converted to the azimuth and inclination, respectively, of the normal vector of the surface. We implemented this system using our CMOS 64 × 64 pixel 3PCIS developed by us and successfully reconstructed the normal vector map in its frame rate (30Hz).
This paper proposes a 3D measurement principle for the correlation image sensor (CIS), which generates temporal correlation between light intensity and an external reference signal at each pixel. Another key of our system besides the CIS is amplitude-modulation of the scanning sheet beam, the phase of which relative to a reference signal is varied according to the scanning angle. After a scan within a frame, the phase is demodulated with a quadrature pair of reference signals and output by the CIS to compute the individual angle of the sheet bam at each pixel. By virtue of lock-in detection principle, the effects of background illumination and/or surface reflectance nonuniformity of the object are thoroughly removed. We implemented this system using our CMOS 64 by 64 pixel CIS, and successfully reconstructed a depth map under its frame rate.
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