Optical: systems and elements – Deflection using a moving element – Using a periodically moving element
Patent
1991-05-24
1993-09-28
Lerner, Martin
Optical: systems and elements
Deflection using a moving element
Using a periodically moving element
356349, 359193, 359561, H04B 1006, G01B 902
Patent
active
052490726
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a heterodyne receptor system capable of detecting with high resolution information light buried in scattered light and an arrangement capable of visualizing optical transmission images.
BACKGROUND TECHNIQUE
When light scatterers like biological tissues are illuminated with light, the resulting, rectilinearly propagating light could be extracted to some extent in a 180.degree. face-to-face system. As yet, however, the spatial resolving power is not good enough.
A difference in the spatial resolving power between light and X-rays cannot be made up for as yet. The use of light, esp. near infrared rays, however, will be able to construct images of tissue's oxygen concentrations from hemoglobin in the blood. These will provide information different from that obtained with other techniques such as
Now let us assume an object 0 shown in FIG. 22 does not contain too much scatterers and is relatively close to transparency. Then, light having a specific wavelength component selected through a filter 340 is directed onto the object 0 from a ring type of slit 341 placed at the focal position of a lens L.sub.1, so that the enlarged image can be focused onto a plane P through an objective L.sub.2 for observation. The use of the ring type of slit 341 located at the focal point of the lens L.sub.1 is tantamount to irradiating the object 0 with light in every direction, as shown in FIG. 23, so that images I.sub.1, I.sub.2, and so on, of the object 0 in the respective directions can be observed at once.
Given a 3 to 5-cm thick tissue, we can detect light transmitted through it. This means that "opto-radiography" can be used for diagnosis. The mammas are relatively uniform in tissue and easy to transmit light, and the transmitted light is easily detectable (at a thickness up to about 3 cm) because of their form. Thus, this technique has long been used for the diagnosis of breast cancer under the name of "Diaphanography" or "Lightscanning". One such conventional diagnostic system will now be explained with reference to FIG. 24.
The construction of a conventional system for obtaining a light absorption distribution image is illustrated in FIG. 24, wherein reference numeral 401 stands for a scan head, 403 the human body, 405 a video camera, 407 an A/D converter, 409 a near infrared light frame memory, 411 a red light frame memory, 413 a processor, 415 a color conversion processor, 417 an encoder keyboard, 419 a D/A converter, 412 a printer, 423 a TV monitor and 425 a video tape recorder. The spot of the human body to be inspected, e.g. the mamma is irradiated and scanned alternately with red light (strongly absorbed in hemoglobin in the blood in particular) and near infrared light (absorbed in the blood, fluids, fat, etc.) by the scan head 401 through a light guide. As shown, the spot is illuminated with light from below. As a result, the mamma glows brightly, and the transmission image is picked up by the video camera 401. That image is converted through the A/D convertor 407 into digital signals, and the near infrared light and red light are fed in the frame memories 409 and 411, respectively, through a digital switch. The ratio of intensities of near infrared light and red light is then computed in the processor 413, and is further converted into analog signals by color conversion processing. The resulting light absorption distribution image is finally observed through a printer, a TV monitor or a video tape.
This system's resolving power is not good enough, because the light leaving the scan head 401, which is not parallel light, diverges through the tissue (the mamma), as much it would be illuminated with the light from a flashlight, and is received by such a two-dimensional receptor as a video camera.
An example of conventional illuminator/receptor systems collimated so as to make improvement in this regard will now be explained with reference to FIG. 25.
FIG. 25 is a diagrammatic sketch illustrating the construction of a conventional unit for obtaining light absorption distri
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Ichimura Tsutomu
Inaba Fumio
Toida Masahiro
Lerner Martin
Research Development Corporation of Japan
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