In conventional Adaptive optics (AO) system, wavefront aberration is measured by wavefront sensor. However, a point
source is usually not available in most imaging systems. Therefore development of deformable mirror control scheme in
adaptive optics system based on vision information will extend the application area of AO technique. A focus measure
(FM) is a measure of image quality and can be calculated from image data obtained from the image sensor. It can be
used to find the optimal shape of the deformable mirror that compensates the wavefront aberration. In this paper, we
analyze the performance of focus measures under different types of wavefront aberrations. The relation of FM vs. the
aberration strength is analyzed systematically for different aberration modes and different FM functions. The FM
performance under combination of aberrations is also investigated. This research supplies a guide for selection of the
suitable FM function and strategy for control of deformable mirror in the AO system.
There exists a trade-off between the depth of field and the image resolution when the depth of field is extended by the
wave-front coding method. The trade-off originates from the extension method and the inevitable detector noise. An
adaptive imaging system can resolve this by minimizing extension of the depth of field to get the image of the highest
resolution. In this paper, a focal plane shift method to minimize the depth extension is introduced and the trade-off
relationship and the proposed concept are investigated by simulation. The trade-off is characterized by applying a set of
focus measures to depth-extended images, and the proposed concept is verified by some test images.
Deflectometry is widely used to measure three-dimensional profile of a specular free-form surface because of its high
accuracy and short inspection time. With phase data obtained by observing the fringe patterns reflected via the surface,
we can measure the shape, specifically normal vector of the surface. In order to obtain the shape of specular free-form
surfaces, two different phases have to be computed for a single area. Two phases are calculated by using two sets of the
phase-shifting patterns with different direction, and usually eight images are needed. In this paper, we propose a two
dimensional phase-shifting method, called 2D phase-shifting method, to compute two phases with different direction
with a single set of 2D phase with only five images. Therefore, the proposed method is expected to have a strong impact
on measurement industry where reducing the number of acquired images is desirable for increasing measurement speed.
The proposed method is verified by both simulation and experiments, in which phase information is successfully
extracted with 2D phase-shifting method.
Insufficient vision information such as occlusion, low resolvability, and a small field of view (FOV) represent important
issues in microassembly and micromanipulation. In previous research, an active optical system was designed to supply a
compact flexible view. However the complex kinematics makes the system operation and calibration much difficult. In
this paper, a decoupling design for the variable view image system with a telecentric lens group is proposed to decouple
the view angle and scanning mirror angle. The proposed design increases the range of zenith angle. The forward
kinematics is analyzed with the help of vector diffraction theory. The singularity of Jacobin is analysis and the
singularity configurations are identified. In order to verify the proposed system, a prototype system is built up. A series
of experiments on the prototype system shows the validity of the new design.
Nowadays, a number of 3D measurement methods have been developed such as stereo vision, laser structured light and PMP (Phase Measuring Profilometry) method. However, they have its own limitations : 2π ambiguity, correspondence problem, long estimation time. To solve these problems, in our previous researches [9,13], we introduced a novel sensing method adopting stereo vision and PMP technique (stereo PMP algorithm). One other difficult problem is occlusion problem needed to tackle by the stereo PMP algorithm which uses the principle of stereo vision and two cameras. The occlusion problem cannot be solved by using the principle of typical stereo vision, because there is no correspondence point in occlusion area. In our previous research based on stereo PMP algorithm, however, phase information related to the projector's position is additionally used which gives more additional information. By using this additional information, we can solve the occlusion problem effectively. In order to detect occlusion area, we adopt the principle of Dynamic Programming, while to measure the depth the principle of typical PMP algorithm and the geometrical relationship of detected depth area. To verify the efficiency of the proposed method, a series of experimental tests were performed.
Application of visual servoing in microassembly area is being developed but still limited by small depth of field of
optical microscopes. There have been several research efforts to resolve this problem in robotics and optics area, but they
are still insufficient to be directly applied. In this paper, the concept of flexible depth of field extension, which is to use
an LC-SLM to alleviate the computational cost of the wave-front coding method and obtain the best image for a given
defocus of the object, and how to implement the system are explained, and it is applied to a microassembly setup for
target detection experiments. The results imply that a good microassembly strategy can be devised for fast and robust
performance in micro world.
Insufficient vision information such as occlusion and low resolvability is one of the important issues that limit the micromanipulation and microassembly. In this paper, we proposed the active vision system that can interact with the environment by changing optical system parameters such as spatial position, orientation and focus plane. As an optomechatronic system, the proposed system integrates a pair of wedge prism, a scanning mirror, a deformable mirror and off-the-shelf optics. The compact double wedge prisms can change the view direction, however the aberration induced by wedge prisms can be corrected by deformable mirror. Combining with a scanning mirror, active optical system can observe the micro object in different view. Owing to the orthogonality of the Zernike polynomials, the proposed deformable mirror control algorithm can correct the aberration in each Zernike mode instead of controlling each actuator, which simplifies the control issue of deformable mirror. The preliminary experiment setup was built, and initial experiments were demonstrated to investigate the validity of the concept of the proposed system.
Proportional control based visual controller is the main method used in the visual serving, but small proportional gain results in the slowly response and large proportional gain will result in large overshoot or make the system instable. A PD visual controller for microassembly system is presented to acquire better dynamic response. The fuzzy logic is applied to tuning the controller gains which is a model free method. Thus, the difficulty in obtaining precise and detailed system model is avoided and we can get satisfactory performance which is robust to modeling error and external disturbances. Furthermore, image moments are selected as visual features to avoid image singularities and the Jacobian matrix is full rank and upper triangular, thus it has the maximal decoupled structure and simplified the controller. A series of simulations are performed on peg and hole assembly to investigate the feasibility and effectiveness of this method.
In this paper, we propose an active vision system which has variable PSF. The system consists of a deformable mirror, an aperture stop and four lenses. The deformable mirror is placed at the pupil plane and its effective size is determined by the aperture stop at the conjugate position of the mirror. We try to enhance the image resolution using this system. We make four different mirror surface shapes to take four regularly shifted images and use super-resolution algorithm to synthesize higher resolution image from the low resolution observations. It is demonstrated that our method can be used to enhance image resolution which is limited by CCD cell size. We compare the result with the real image and some discussion about algorithmic parameters follows.
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