Browse Prior Art Database

Optical Character Recognition Scanner

IP.com Disclosure Number: IPCOM000076861D
Original Publication Date: 1972-May-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 34K

Publishing Venue

IBM

Related People

Dickson, LD: AUTHOR

Abstract

A variable-wavelength laser can be combined with a Fresnel zone plate to provide an optical scanning system.

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Optical Character Recognition Scanner

A variable-wavelength laser can be combined with a Fresnel zone plate to provide an optical scanning system.

The embodiment shown in Fig. 1 utilizes a laser 1 having an output wavelength variable over a range of 20 nm. The output beam is directed through an optical grating 2. The beam is brought to a focus by lens 3. When the laser is operating at wavelength lambda 1, the beam is brought to a focus at point P1. If the operating wavelength of laser 1 is decreased to lambda 2, the beam is brought to a focus at point P2. Because the beam is diffracted by grating 2, a change in wavelength from lambda 1 to lambda 2 has the effect of decreasing the angle of deflection.

The embodiment shown in Fig. 2 also utilizes a laser 1 having an output wavelength variable over a range of 20 nm. The output beam is directed through a high-efficiency zone plate 4. The focal length of zone plate 4 is defined

(Image Omitted)

f = r2 over n lambda where r = radius to the outermost zone n = number of zones lambda = wavelength of incident radiation.

Although this zone plate is centered on the optical axis of the system, the zones themselves are offset as shown in 2a. The effect of the offset zones is to bring the output beam having a wavelength lambda 1 to a focus at point P1. As the output wavelength is changed from lambda 1 to lambda 2 the point of focus changes from P1 to P2, where lambda 2 > lambda 1. The line 5 connects the points of focus P1 and P...