Marked card reader employing afocal spatial filtering
AssigneeDelaware Capital Formation, Inc.
InventorsDavid R. Howland, Henry W. Cassady
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Abstract
A marked card reader having a lensless optical detection system with fixed angle illumination and detection, the sensitivity of which is independent of the frequency response associated therewith. The optical detection system includes a radiation source to produce radiation and a radiation detector. A target plane is positioned so that the radiation source directs radiation toward the target plane. The detection source is positioned to sense radiation reflected from the target plane. An optically opaque body is positioned between the optical detector and the radiation source to prevent incident radiation from be sensed by the optical detector.
Claims20
A marked card reader for reading a data entry card of the type having a first surface with predefined regions thereof containing related areas of contrasting optical reflectivity encoding preselected data, and a second opposite surface, comprising:
- a slot adapted to slideably receive said data entry card to be read by the marked card reader, a portion of said slot comprising a fixed optical target plane adjacent said second opposite surface of said card;
- a first optical radiation source to produce incident optical radiation on said first surface of said card in said predefined regions, said optical radiation source having a fixed first optical axis extending toward said target plane at a preselected first oblique angle with respect to said target plane;
- a second optical radiation source to produce incident optical radiation on said first surface of said card in said predefined regions, said second optical radiation source having a fixed second optical axis extending toward said target plane at a preselected oblique angle with respect to said target plane;
- an optical radiation detector to detect said incident optical radiation reflected from said first surface of said card, said optical radiation detector having a fixed third optical axis extending toward said target plane at a preselected third angle with respect to said target plane, said third angle not equal to said first or second oblique angles;
- an optically opaque body interposed between said optical radiation detector and said target plane, said optically opaque body having a first aperture disposed along said second optical axis to facilitate communication of said incident optical radiation directly reflected from a selected area of said first surface of said card including at least a portion of said predefined regions to said optical radiation detector and to reduce communication of non-reflected optical radiation to said optical radiation detector;
- and
- an a focal spatial filter internal to said optically opaque body positioned between said first aperture and said optical radiation detector, said a focal spatial filter disposed along said third optical axis and sized and positioned to improve the resolution of the optical radiation detector.
A marked card reader for reading data optically encoded as marks on a data entry card, comprising:
- a first optical radiation source for producing incident optical radiation on a portion of said card at a first fixed angle;
- a second optical radiation source for producing additional incident optical radiation on said portion of said card at a second fixed angle;
- an optical radiation detector for detecting incident optical radiation directly reflected from said portion of said card at a third fixed angle and converting the same to corresponding electrical signals;
- an optical body interposed between said card and said optical radiation detector having optical characteristics to selectively communicate incident optical radiation directly reflected from said portion of said card along said third angle to said optical radiation detector, and to selectively inhibit communication of other optical radiation to said optical radiation detector;
- and
- an a focal spatial filter interposed between said card and said optical radiation detector, said a focal spatial filter cooperating with said optical body to direct said incident optical radiation directly reflected from said portion of said card on said optical radiation detector.
Dependencies are inferred from the claim text.