Advanced wavefront / waveform modulation technology

Wavefront modulation technology

Typical devices that control light are lenses, mirrors, shutters, etc., which change or block the direction of light. The liquid crystal display can display images by controlling the light intensity. Focusing on the feature of light called “phase distribution” or “wavefront”, we have researched spatial light modulators for many years and developed LCOS-SLM as an optical wavefront control device. When the light propagates, the place where the phases are aligned at a certain time is said to be in the same phase θ, and the surface formed by connecting these consecutive points is called the wavefront.

LCOS-SLM is a device that controls the wavefront of light and can be easily controlled by a personal computer. By changing the refractive index of the liquid crystal in the plane, the wavefront shape of light can be freely controlled, and optical devices and functions such as lenses and diffraction gratings can be realized.

When the phase hologram derived by calculation is displayed on to the LCOS-SLM and irradiated with laser light, arbitrary beam pattern can be reproduced. By changing the optical arrangement of this phase hologram, light can be controlled in the same way as lenses, mirrors and shutters. Taking advantages of the fact that this device can control the phase in two dimensions dynamically (30 frames per second) with high precision, we have applied LCOS-SLM to laser processing, adaptive optics (fundus measurement), microscopes and optical tweezers. As a basic research, we also generate holograms of light beams with orbital angular momentum called Laguerre Gaussian beams. We conduct research and development of new devices and aim to improve technologies such as more advanced control and software.



High speed sensing

As for a light detecting device, we have developed an intelligent vision sensor (IVS) and conducting applied research. IVS is an imaging system with a small high-speed image processing function that performs image acquisition, image processing and signal output in 1 millisecond. The feature of this camera is that it can acquire images at a frame rate in the order of kHz and perform image processing such as bright spot centroid calculation in real time. This device can be used for robot vision systems, we used IVS measurement results to control LCOS-SLM. Observation of the fundus is achieved by incident laser from the pupil, performing a raster scan, and measurement and reconstruction from the intensity of the return light. However, the scattered return light will be distorted due to the cornea, the crystalline lens and the vitreous. To correct this distortion, it is necessary to perform wavefront measurement. By using IVS, high-speed wavefront measurement has been realized under conditions that are susceptible to disturbances such as the microscope viewing angle.

Optical designing

It is important to make in-house optical materials such as crystals and optical thin films that would become key parts in optical devices, and we aimed to create such optical materials. At present, we are developing new devices from the creation of materials and to provide the materials technology we have cultivated to other prototype research. Particularly in the development of optical thin films, we are developing prototypes of mirrors, filters, and AR coatings for LCOS-SLM application research, contributing to device fabrication that cannot be achieved by SLM competitors.

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