Opticscan arrangement for optical character recognition systems

Claim 2

In an optical character reading machine of the type intended to read plural characters arranged in at least one line extending along the width of a flat document by examining successive vertical slices of each character in turn while said document is motionless relative to said machine, apparatus including: source means for generating a light beam having a height in cross-section approximately the size of the maximum height of each of said characters and having a width in cross-section which is considerably narrower than the width of each of said characters; means for projecting said light beam along a first axis; a first optical path extending between said means for projecting and said characters and partially along said first axis, said first optical path including a single-surface scanning mirror positioned to reflect said light beam onto said characters; means for cyclically rotating said scanning mirror about a second axis to sweep said projected beam width-wise across said document such that successive vertical slices of each character in said line are successively illuminated, said second axis being positioned to define an imaginary plane with the longitudinal center line of said document, which plane has a substantially perpendicular intersection with said document, thereby centering said second axis relative to the document so that variations in distance between the mirror and an illuminated slice are minimized during cycles of said mirror; optical image sensing means; and a second optical path extending from said characters and terminating at said optical image sensing means, said second optical path including said scanning mirror and said first optical path and further comprising means for accurately imaging each illuminated character slice onto said optical image sensing means.

Claim 3

In an optical character reading machine of the type intended to read plural characters arranged in at least one line extending along the width of a flat document by examining successive vertical slices of each character in turn, apparatus including: source means for generating a light beam having a height in cross-section approximately the size of the maximum height of each of said characters and having a width in cross-section which is considerably narrower than the width of each of said characters; means for projecting said light beam along a first axis; a first optical path extending between said means for projecting and said characters and partially along said first axis, said first optical path including a single-surface scanning mirror positioned to reflect said light beam onto said characters; means for cyclically rotating said scanning mirror about a second axis to sweep said projected beam width-wise across said document such that successive verticAl slices of each character in said line are successively illuminated, said second axis being positioned to define an imaginary plane with the longitudinal center line of said document, which plane has a substantially perpendicular intersection with said document; optical image sensing means; and a second optical path extending from said characters and terminating at said optical image sensing means, said second optical path including said scanning mirror and said first optical path and further comprising means for accurately imaging each illuminated character slice onto said optical image sensing means; wherein said means for accurately imaging includes a lens arrangement and means synchronized to said drive means for varying the focal distance of said lens arrangement as a function of the mirror scan angle to focus each illuminated character slice on said optical image sensing means.

Claim 4

In an optical character reading machine of the type intended to read plural characters arranged in at least one line extending along the width of a flat document by examining successive vertical slices of each character in turn, apparatus including: source means for generating a light beam having a height in cross-section approximately the size of the maximum height of each of said characters and having a width in cross-section which is considerably narrower than the width of each of said characters; means for projecting said light beam along a first axis; a first optical path extending between said means for projecting and said characters and partially along said first axis, said first optical path including a single-surface scanning mirror positioned to reflect said light beam onto said characters; means for cyclically rotating said scanning mirror about a second axis to sweep said projected beam width-wise across said document such that successive verticAl slices of each character in said line are successively illuminated, said second axis being positioned to define an imaginary plane with the longitudinal center line of said document, which plane has a substantially perpendicular intersection with said document; optical image sensing means; and a second optical path extending from said characters and terminating at said optical image sensing means, said second optical path including said scanning mirror and said first optical path and further comprising means for accurately imaging each illuminated character slice onto said optical image sensing means; wherein said means for accurately imaging includes a lens arrangement and means synchronized to said drive means for varying the focal distance of said lens arrangement as a function of the mirror scan angle to focus each illuminated character slice on said optical image sensing means.

Claim 5

The apparatus according to claim 2 wherein the plane of said document is disposed at an angle of approximately 10* relative to said second axis to eliminate specular reflection from said character slices along said second optical path.

Claim 6

The apparatus according to claim 3 wherein said apparatus further comprises means synchronized to said drive means for rotating said optical image sensing means about said second optical path as a function of mirror scan angle to at least partially compensate for skewing of character images at said optical image sensing means resulting from the angle formed between said second axis and said document.

Claim 7

The apparatus according to claim 4 wherein said means for rotating said optical image sensing means includes means for limiting such rotation to assure that the illuminated image reflected along said second optical path always extends over the entire optical image sensing means.

Claim 8

The apparatus according to claim 5 wherein said source means includes a relatively low power laser for generating said light beam, and beam-forming means to configure the cross-section of said light beam to the configuration necessary to illuminate a vertical character slice.

Claim 9

The apparatus according to claim 2 wherein said means for projecting comprises a small light-reflecting element positioned on said first axis to direct said light beam along said first optical path toward said scanning mirror, said element being positioned relative to said lens arrangement so as to intercept an insignificant part of the image reflected along said second optical path.

Claim 10

The apparatus according to claim 2 wherein said lens arrangement comprises a pair of condensing lenses arranged back-to-back along said first axis, and wherein said means for varying the focal length includes means for translating at least one of said lenses along said first axis as a function of the mirror scan angle.

Claim 11

The apparatus according to claim 8 wherein said means for projecting comprises a small light-reflecting element positioned on said first axis to direct said light beam along said first optical path toward said scanning mirror, said element being positioned between said two lenses at a location in which it intercepts an insignificantly small portion of the illuminated image reflected along said second optical path.

Claim 12

In an optical character reading machine of the type intended to read characters arranged in at least one line by examining successive vertical slices of each character in turn, apparatus including: source means for generating a light beam having a height in cross-section approximately the size of the maximum height of each of said characters and having a width in cross-section which is considerably narrower than the width of each of said characters; means for projecting said light beam along a first axis; a first optical path extending between said means for projecting and said characters and partially along said first axis, said first optical path including a single-surface scanning mirror positioned to reflect sAid light beam onto said characters; drive means for rotating said scanning mirror about a specified axis to sweep said projected beam width-wise across said document and said line of characters such that successive vertical slices of each character in said line are successively illuminated, said scanning mirror being positioned such that said second axis forms an angle of approximately 10* with said document; optical image sensing means; a second optical path extending from said characters and terminating at said optical image sensing means, said second optical path including said scanning mirror and said first optical path and further comprising means for accurately imaging each illuminated character slice onto said optical image sensing means; and means synchronized to said drive means for rotating said optical image sensing means about said second optical path as a function of mirror scan angle to at least partially compensate for skewing of character slice images at said optical image sensing means resulting from the angle formed between said second axis and said document.

Claim 13

In an optical character reading machine of the type intended to read characters arranged in at least one line by examining successive vertical slices of each character in turn, apparatus including: source means for generating a light beam having a height in cross-section approximately the size of the maximum height of each of said characters and having a width in cross-section which is considerably narrower than the width of each of said characters; means for projecting said light beam along a first axis; a first optical path extending between said means for projecting and said characters and partially along said first axis, said first optical path including a single-surface scanning mirror positioned to reflect sAid light beam onto said characters; drive means for rotating said scanning mirror about a specified axis to sweep said projected beam width-wise across said document and said line of characters such that successive vertical slices of each character in said line are successively illuminated, said scanning mirror being positioned such that said second axis forms an angle of approximately 10* with said document; optical image sensing means; a second optical path extending from said characters and terminating at said optical image sensing means, said second optical path including said scanning mirror and said first optical path and further comprising means for accurately imaging each illuminated character slice onto said optical image sensing means; and means synchronized to said drive means for rotating said optical image sensing means about said second optical path as a function of mirror scan angle to at least partially compensate for skewing of character slice images at said optical image sensing means resulting from the angle formed between said second axis and said document.

Claim 14

The apparatus according to claim 10 wherein said means for rotating said optical image sensing means includes means for limiting such rotation to assure that the illuminated image reflected along said second optical path always extends over the entire optical image sensing means.

Claim 15

The apparatus according to claim 10 wherein said means for accurately imaging includes a lens arrangement and means synchronized to said drive means for varying the focal distance of said lens arrangement as a function of the mirror scan angle to focus each illuminated character slice on said optical image sensing means.

Claim 16

The apparatus according to claim 12 wherein said means for projecting comprises a small light-reflecting element positioned on said first axis to direct said light beam along said first optical path toward said scanning mirror, said element being positioned relative to said lens arrangement so as to intercept an insignificant part of the image reflected along said second optical path.

Claim 17

The apparatus according to claim 12 wherein said lens arrangement comprises a pair of condensing lenses arranged back-to-back along said first axis, and wherein said means for varying the focal length includes means for translating at least one of said lenses along said first axis as a function of the mirror scan angle.

Claim 18

The apparatus according to claim 14 wherein said means for projecting comprises a small light-reflecting element positioned on said first axis to direct said light beam along said first optical path toward said scanning mirror, said element being positioned between said two lenses at a location in which it intercepts an insignificantly small portion of the illuminated image reflected along said second optical path.