Patent ID: 6299066
Filing Date: 2001-10-09
Classification: G05B

Abstract:
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; andan 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.