Hybrid surface measuring system for motion-blur compensation and focus adjustment using a deformable mirror.

The recent growth in automation and microfabrication has led to a need for faster, more accurate inspections. This in turn requires fast and accurate image capture methods. A system has previously been proposed to obtain images without motion blur by controlling the line of sight to follow a moving object with a mirror, thereby decreasing inspection time. However, as this system follows only the line of sight, it corresponds only to the plane parallel to the direction of movement. Here, we propose a system for measuring non-planar surfaces by simultaneously controlling the line of sight and focus using a deformable mirror. In addition, the proposed system requires only one deformable mirror, whereas those from previous studies require multiple devices to control the line of sight and focus. Therefore, our proposed system can be downsized and applied to various measurement systems. We tested our system by measuring surface images of objects with curved and uneven surfaces under movement at 20 mm/s, at a distance of about 140 mm in front of the mirror. The system successfully obtained motion-blur-free, all-in-focus images. Moreover, we validated the effectiveness of the proposed system by comparing the captured images to those obtained using existing methods.

Optimal Material Search for Infrared Markers under Non-Heating and Heating Conditions.

Research on optimal markers for infrared imaging and differences in their characteristics in the presence of heat sources has not yet been performed. This study investigates optimal material combinations for developing an accurate and detachable infrared marker for multiple conditions in the medium wave infrared (MWIR) region. Based on four requirements, 11 material combinations are systematically evaluated. Consequently, the optimal marker differs in relation to the presence of specular reflection components. Metal-insulator markers are suitable under non-heating and hot-air heating conditions without reflection components, although a printed marker made of copier paper is captured more clearly than metal-insulator markers during heating, using an optical radiation heating source with reflection components. Our findings can be applied in structural health monitoring and multi-modal projection involving heat sources.

Dynamic perceptive compensation for the rotating snakes illusion with eye tracking.

This study developed a dynamic perceptive compensation system for the rotating snakes illusion (RSI) with eye tracking. Large eye movements, such as saccades and blinks, were detected with an eye tracker, and perceptive compensation was dynamically performed based on the characteristics of RSI perception. The proposed compensation system considered three properties: spatial dependence, temporal dependence, and individual dependence. Several psychophysical experiments were performed to confirm the effectiveness of the proposed system. After the preliminary verification and determination of the temporal-dependent function for RSI perception, the effects of gaze information on RSI control were investigated. Five algorithms were compared using paired comparison. This confirmed that the compensation system that took gaze information into account reduced the RSI effect better than compensation without gaze information at a significance threshold of p < 0.01, calculated with Bonferroni correction. Some algorithms that are dependent on gaze information reduced the RSI effects more stably than still RSI images, whereas spatially and temporally dependent compensation had a lower score than other compensation algorithms based on gaze information. The developed system and algorithm successfully controlled RSI perception in relation to gaze information. This study systematically handled gaze measurement, image manipulation, and compensation of illusory image, and can be utilized as a standard framework for the study of optical illusions in engineering fields.

Dielectric-elastomer-based fabrication method for varifocal microlens array.

We report on a method to fabricate a varifocal microlens array that employs a dielectric elastomer (DE) sandwiched between two electrodes as the lens material. The microlens array is patterned on the electrode plates, and when the electrodes are subjected to a controllable operating voltage, the DE material is "squeezed" by the Maxwell force to deform the lens array pattern, thus resulting in curvature deformation yielding a tunable lens profile. The tunable focal length performance ranges from 950 mm to infinity. When compared with liquid-filled lenses, solid-based varifocal lenses are more robust to thermal expansion, gravity, and vibrational motion. Our approach can be utilized in applications such as machine vision systems.

Gain-compensation Methodology for a Sinusoidal Scan of a Galvanometer Mirror in Proportional-Integral-Differential Control Using Pre-emphasis Techniques.

Galvanometer mirrors are used for optical applications such as target tracking, drawing, and scanning control because of their high speed and accuracy. However, the responsiveness of a galvanometer mirror is limited by its inertia; hence, the gain of a galvanometer mirror is reduced when the control path is steep. In this research, we propose a method to extend the corresponding frequency using a pre-emphasis technique to compensate for the gain reduction of galvanometer mirrors in sine-wave path tracking using proportional-integral-differential (PID) control. The pre-emphasis technique obtains an input value for a desired output value in advance. Applying this method to control the galvanometer mirror, the raw gain of a galvanometer mirror in each frequency and amplitude for sine-wave path tracking using a PID controller was calculated. Where PID control is not effective, maintaining a gain of 0 dB to improve the trajectory tracking accuracy, it is possible to expand the speed range in which a gain of 0 dB can be obtained without tuning the PID control parameters. However, if there is only one frequency, amplification is possible with a single pre-emphasis coefficient. Therefore, a sine wave is suitable for this technique, unlike triangular and sawtooth waves. Hence, we can adopt a pre-emphasis technique to configure the parameters in advance, and we need not prepare additional active control models and hardware. The parameters are updated immediately within the next cycle because of the open loop after the pre-emphasis coefficients are set. In other words, to regard the controller as a black box, we need to know only the input-to-output ratio, and detailed modeling is not required. This simplicity allows our system to be easily embedded in applications. Our method using the pre-emphasis technique for a motion-blur compensation system and the experiment conducted to evaluate the method are explained.

Gain-compensated sinusoidal scanning of a galvanometer mirror in proportional-integral-differential control using the pre-emphasis technique for motion-blur compensation.

We propose a method to achieve precise sine-wave path tracking for real-time motion-blur compensation to extend the corresponding frequency spectrum in proportional-integral-differential (PID) control by using a pre-emphasis technique. We calculate pre-emphasis coefficients in advance to follow a sine wave with a gain of 0 dB and multiply the input signal by these pre-emphasis coefficients. In experiments, we were thus able to extend the greatest frequency from 100 to 500 Hz and achieve gain improvement of approximately 3 dB at 400 and 500 Hz. For the application of inspection, we confirmed that motion blur is significantly reduced when the system operates at high frequency, and we achieved a responsiveness 3.3 times higher than that of our previous system.

Real-time high-speed motion blur compensation system based on back-and-forth motion control of galvanometer mirror.

We developed a novel real-time motion blur compensation system for the blur caused by high-speed one-dimensional motion between a camera and a target. The system consists of a galvanometer mirror and a high-speed color camera, without the need for any additional sensors. We controlled the galvanometer mirror with continuous back-and-forth oscillating motion synchronized to a high-speed camera. The angular speed of the mirror is given in real time within 10 ms based on the concept of background tracking and rapid raw Bayer block matching. Experiments demonstrated that our system captures motion-invariant images of objects moving at speeds up to 30 km/h.