Keigo Iizuka

Step-frequency radar

The step‐frequency radar is proposed as a means of detecting targets imbedded in high loss media. The radar derives information on target distance by exploiting the phase and amplitude characteristics of the returned signal. With a given frequency change, the phase angle change from a faroff target is larger, and therefore its phasor rotates faster, than that from a closeby target. Distance information is conveniently derived by applying the Fast Fourier Transform algorithm. The radar is able to offset an arbitrary distance and zoom to the targets, thereby obtaining fine resolution. With Wiener filtering, the resolution of the radar is high enough to identify the type, as well as the orientation, of the buried targets. A subtraction feature has also been incorporated which allows scattering from unwanted targets to be cancelled out from that of the wanted targets. The radar was successfully demonstrated for the detection and identification of various targets buried in sand, moist clay soils, underwater, a...

Axi-Vision Camera (real-time distance-mapping camera)

The camera described here makes color TV images that include information about the distance between the camera and the objects in the images. This range information is obtained from two images of the same scene taken under different illumination conditions. The camera does not require scanning, multiple camera units, or complicated computation. Range information for each pixel is acquired fast enough to keep up with the video rate of a TV camera. We describe various operational features and technical specifications such as ranging errors as well as the results of experimental investigations of the dependence on the color and reflectivity of the objects, of the sensitivity to interference from external light, and of the effects of the movement of the objects.

Welcome to the Wonderful World of 3D: Introduction, Principles and History

First article of a four-part series. You are invited to explore the wonderful world of three-dimensional imaging. The tour begins with this article, which explains how optics can be used to create 3D illusions.

Detection of nonmetallic buried objects by a step frequency radar

An attempt was made to detect nonmetallic buried objects by means of a stepped frequency radar which uses the phase information of the returned UHF signal. After a brief discussion concerning the attenuation of the signal in the soil and the principle of operation it was demonstrated that the two 3-in ABS plastic drain pipes buried 35 cm deep in soil can be detected. The horizontal and vertical resolutions are 7 cm and 12.5 cm, respectively. The penetration is 70-90 cm.

High-definition real-time depth-mapping TV camera: HDTV Axi-Vision Camera.

We have developed a field-worthy, high-definition, real-time depth-mapping television camera called the HDTV Axi-Vision Camera. The camera can simultaneously capture both an ordinary HDTV color image and a depth image of objects on more than 1280 x 720 pixels at a frame rate of 29.97 Hz, or on 853 x 480 pixels at a frame rate of 59.94 Hz. The number of detectable pixels per unit time was increased by about 5 times that of the prototype camera by improving the sensitivity and resolution of the depthmapping camera. Short video clips demonstrate how depth information from the camera can be used to create a virtual image in actual television program production.

Optical step frequency reflectometer

The carrier generated by a solid‐state laser can be frequency shifted by a significant amount. This fact was exploited to implement a high‐resolution optical‐fiber fault locator. A resolution of 4 mm was achieved. Compared to the resolution of a frequency‐domain reflectometer that shifts the frequency of the AM modulation of the light, the proposed fault locator has a resolution about 1000 times better. The potential of developing the proposed reflectometer into an ultrahigh‐resolution integrated optics fault locator is also discussed. UFaipxr

A hologram matrix radar

The concept of hologram matrix is proposed. This concept was incorporated into the design of a novel radar which, unlike conventional radars, determines the distance by the spatial distribution of the scattered wave rather than by the lapse of time. The radar based upon this principle was developed and built for the purpose of mapping ice thickness in the range of 0.5 ∼ 5 m, but it has potential applications in other fields. Such a radar has real-time processing capability, resulting from an amalgamation of the antenna and computer subsytems. The programability of the radiation pattern by software of the processing simplifies the construction of the radar. Capability of dual focussig of the transmitter and receiver eliminates the necessity of either pulsing, or frequency modulation of the transmitting signal. Superior performance in the short range, with high resolution, is particularly advantageous for measuring lossy ice. These features were substantiated by experimental results obtained from the field operation of the system.

Divergence-ratio axi-vision camera (Divcam): A distance mapping camera

A novel distance mapping camera, the divergence-ratio axi-vision camera (Divcam), is proposed. The decay rate of the illuminating light with distance due to the divergence of the light is used as a means of mapping the distance. Resolutions of 10 mm over a range of meters and 0.5 mm over a range of decimeters were achieved. Special features of this camera are its high resolution, real time operation, simplicity, compactness, light weight, portability, and yet low fabrication cost.

Gain-modulated Axi-Vision Camera (high speed high-accuracy depth-mapping camera)

We describe a novel real-time depth-mapping camera, the Gainmodulated Axi-Vision Camera, where pulsed laser light is combined with a gain-modulated camera. Depth resolution of 2.4 mm was obtained, which is higher than the resolution of the previously reported depth-mapping Axi- Vision Camera. Pixel-by-pixel depth information of 768 x 493 pixels is obtainable at one half of the video frame rate (15 Hz). A short movie clip is attached that illustrates the depth measurement operation. The merits of the Gain-modulated Axi-Vision Camera are high-resolution, real-time operation, and a relatively simple optical system. These merits primarily arise from the ultra-fast exposure time using a pulsed laser diode.

Optical fiber fault locator by the step frequency method.

A step frequency method (SFM) is proposed as a new scheme for an optical fiber fault locator. The principle of operation and significant features of the method are described. The feasibility was demonstrated by detecting the discontinuities in a 10-km long multimode fiber using the 830-nm wavelength. The results demonstrate the feasibility of using the SFM in practical fiber optical networks.