Importance

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Abstract

An apparatus including a source for producing a concentrated light beam, such as a laser, a background element spaced from the source against which the light beam is directed, and a transport arrangement for moving translucent bodies, such as French cut potatoes, through the light beam. When light from the source impinges upon a pure translucent body, the light is scattered or diffused within the body around the point of impingement so as to illuminate a surface area of the body larger than the cross-sectional area of the light beam, but light from the source impinging upon an impurity in the translucent body is scattered or diffused to a lesser extent. The background element is formed of a material which causes light from the source which impinges on it to be diffused within the material in a manner similar to the diffusion of the light in the translucent bodies. A receiver having a field of view larger than the cross-sectional area of the light beam receives light reflected from the background and from translucent bodies moving through the light beam. The receiver is insensitive to light in the part of its field of view which is operatively aligned with the point of impingement of the light beam on the translucent bodies or on the background element. The receiver produces an output signal which changes when an impurity enters the concentrated light beam, and this changed signal is used to operate a device which removes the impurity from the remainder of the translucent bodies.

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First Claim