OKU Laboratory

2020-

​HMDs in widespread use today suffer from vergence-accommodation conflict (VAC) and insufficient display frame rate. The former causes eyestrain and VR sickness. The latter causes misalignment between objects and annotations when presenting annotations to the real world through a see-through HMD, due to the slow refresh rate of the display, which causes discomfort for the viewer. To solve these problem, we developed 1000-volume/s high-speed display composed of Tunable Acoustic Gradient index(TAG) lens that can change focal distance rapidly and Digital Micromirror Device that can present image rapidly. This display can present 1000 volumes per second.

2020-

A normal camera can only capture an image at a certain focal length at a time. If it is necessary to take several images with different focal lengths, it is necessary to change the focal length for each image. Conventional methods of image synthesis such as holography and light fields have been used to solve this problem, but these methods require image reconstruction process based on the measured information.In response to this, we have developed Simulfocus Imaging, a technique to capture multiple focal points simultaneously, in collaboration with Professor Shoji Kawahito's group at Shizuoka University. The advantage of this technique is that it can optically capture images at multiple focal lengths and does not require image reconstruction process.

2020-

 In general, the field of view and the focal range of microscopes is narrow. Therefore, when the moving object such as swimming cell is observed, the swimming cell moves not only to planar direction but also to depth direction of the microscope and it is difficult to keep the swimming cells under the microscope. To solve this problem, the high-speed 3D tracking for microscopic objects is demanded. In this study, The high-speed 3D measurement can be achieved by synchronizing the TAG lens and TeCE camera. In our study, the high-speed 3D module which coupling TeCE camera with TAG lens was developed, and it was confirmed that 3D information of swimming cell (Chlamydomonas) can be acquired and the high-speed 3D tracking of the cell can be achieved by using the acquired 3D information.

2017-

The high-speed 3D measurement under a microscope is demanded in biology. One way of the high-speed 3D measurement is to acquire an image of the object to be measured by scanning the focal position of the microscope in the optical axis direction. However, it has been difficult to rapidly measure the 3D information since the drive frequency of existing Z scanners is not high enough. For this problem, Tunable Acoustic Gradient index (TAG) lens was developed. However, the image sensor, which can capture an image at specific focal position, has the limitation since the focus varying cycle of TAG lens is too fast. To solve this problem, a method, which a particular focal planes were captured as color components of the color image by synchronizing the color strobe lights and the focus varying cycle of TAG lens, was proposed. We address a development of high-speed 3D feedback microscope system which 3D information is calculated from captured focal planes and feedbacked, by using a principle of this method.

2017-

Measurement of the 3D position and orientation of objects is essential for VR/AR applications. To satisfy this requirement, an edible AR marker made of the edible retroreflector is proposed. This AR marker, called an Edible AR (E-AR) Marker, works as a fiducial marker of position and orientation, which can be put on food.

2017-

We propose an edible retroreflector made from transparent foodstuffs. We found that kanten, or Japan agar, which is a traditional Japanese cooking ingredient used to form a transparent jelly, was suitable for forming such optical devices. A recipe for an edible retroreflector using kanten was developed.

2015-

The speed of conventional active stereo is slow due to the large amount of calculation.

To achieve high-speed 3D restoration, our group proposed the Structured Light Field (SLF) that can reduce the amount of calculation. The SLF is a light distribution that changes its lateral intensity pattern in accordance with the distance from the source. By projecting SLF to a scene, the projected image on each object in the scene has a particular pattern depending on the depth of the object. This means that the depth information is projected and superimposed on the surface of the objects, and direct estimation of depth is possible by recognizing the projected intensity pattern.

2015-

The high-speed gaze direction controller using two rotational mirrors, named Saccade Mirror has been reported. However, this system has a limited gaze control range, namely, up to 60 degree for each axis. To solve this problem, we developed a new high-speed optical gaze controller with wide range based on three automated rotational mirrors, named "Saccade Mirror 3". 

2013-

Current projection mapping technology projects light on mainly static object. It was difficult to use dynamic object as a screen, since the projection would include large displacement between the screen position and projected image due to the delay in system components, such as a camera to detect object positions and a projector.

A new projection technology based on a high-speed gaze controller (Saccade Mirror) and high-speed image processing (1000 fps) was proposed as "Lumipen" to achieve a stable projection mapping on a dynamic object.

2011-

The "auto pan/tilt" technology automatically control the pan/tilt angle of video cameras, just like the auto focus automatically control the focus of cameras.

A high-speed gaze controller, named "Saccade mirror",  developed by the PI of this  laboratory  combined with a high-speed image processing can track even a pingpong ball in play, and record a "1ms auto pan/tilt" movie. In this movie, the ball is always kept at the center of field of view.

2005-

A tunable lens, or variable-focus lens, is a new optical device that can modify the focal length of the single lens itself. One potential advantage of this lens device is that it could achieve high-speed response. Most current optical systems composed of two or more lenses change their focal length by moving one or several lens(es). However, high-speed focal length control is difficult due to the certain mass of such lens(es). This difficulty could be overcome by the tunable lens, since such lenses can focus by slight deformation of the refractive surface.

We developed a high-speed tunable lens achieving a high-speed response of 3.5 ms by using a piezostack actuator, and practical imaging performance due to the smooth and spherical interface between two immicible liquids.

1999-

There is a big difficulty in observation of a motile microorganism, since suh specimen can swim out of the field of view of the microscope in a fraction of second. 

To overcome this difficulty, a microorganism tracking microscope was developed. This system tracks a freely swimming microorganism by visually recognizing the target position and feedback control of an automated XYZ stage.