Portable reader system having an adjustable optical focusing means for reading optical information over a substantial range of distances

• US 5,811,828 A
• Filed: 06/05/1997
• Issued: 09/22/1998
• Est. Priority Date: 09/17/1991
• Status: Expired due to Term

• Current Assignee: Intermec IP Corporation (Honeywell International Inc.)
• Original Assignee: Norand Corporation (Baker Hughes Company)
• Inventors: Laser, Vadim
• Primary Examiner(s): LE, QUE TAN
• Application Number:
  US08/869,475
• Time in Patent Office: 474 Days
• Field of Search: 250/566, 250/201.4, 250/234, 250/235
• US Class Current: 250/566
• CPC Class Codes: G06K 2207/1013 Multi-focal
• CPC Class Codes: G06K 7/10722 Photodetector array or CCD scanning
• CPC Class Codes: G06K 7/10811 Focalisation
• CPC Class Codes: G06K 7/10881 constructional details of hand-held scanners

Abstract

A portable optical reader system for reading optical information over a substantial range of distances includes a casing having a light receiving opening for alignment with optical information. Further included is a reading sensor for converting a reflected light image of optical information into an information signal and reflected light optical elements for forming a reflected light image. The optical system is adjustable to tend to focus a reflected light image of optical information, located within a substantial range of distances, onto the reading sensor. A light beam generator is associated with the casing and directed relative to the optical elements and the light receiving opening such that a light beam generated thereby will impinge on an information carrier, having optical information to be read, and will be reflected therefrom through the light receiving opening and via the optical elements to the reading sensor. Since the position of impingement of the reflected light beam on the reading sensor is a function of the range of the information carrier from the image sensor, the optical system may be adjusted to focus a reflected light image of optical information associated with the information carrier, at least in part, according to the position of impingement of the reflected light beam on the reading sensor.

Claims

1. A portable optical reader system for reading optical information over a substantial range of distances, comprising:

(a) a casing having a light receiving opening for alignment with optical information to be read;

(b) optical means comprising reflected light collecting means for forming a reflected light image and reading sensor means for converting a reflected image of optical information into an information signal, said optical means being adjustable such that said collection means tends to focus a reflected light image of optical information located within said substantial range of distances onto said reading sensor means;

(c) light beam generating means associated with said casing and directed relative to said optical means and said light receiving opening such that a light beam generated thereby will impinge on an information carrier having optical information to be read and will be reflected therefrom through said light receiving opening and via said collecting means to said reading sensor means, the position of impingement of the reflected light beam on said reading sensor means being a function of the range of the information carrier from said image sensor; and

(d) control means for adjusting said optical means to tend to focus a reflected light image of optical information associated with the information carrier at least in part in accordance with the position of impingement of the reflected light beam on said reading sensor means.

2. The portable optical reader system of claim 1, wherein said reading sensor means comprises a solid state photoelectric sensor array capable of resolving elements of optically readable information simultaneously incident thereon.

3. The portable optical reader system of claim 1, wherein said optical means includes at least one lens.

4. The portable optical reader system of claim 3, wherein said optical means further includes a first mirror for collecting light from said lens and reflecting said light.

5. The portable optical reader system of claim 4, wherein said optical means further includes a movable mirror for effecting focusing of light reflected from said first mirror onto said sensor means.

6. The portable optical reader system of claim 5, wherein said optical means further includes means for adjustable moving said movable mirror in relation to said sensor means without changing the aiming axis of the optical means which is to be aligned with the optical information.

7. The portable optical reader system of claim 6, wherein said movable mirror is adjustably movable about at least one axis.

8. The portable optical reader system of claim 6, wherein said movable mirror is adjustably movable about at least two axes.

9. The portable optical reader system of claim 1, wherein said control means controls movement of said sensor means to effect focusing of the reflected light image.

10. The portable optical reader system of claim 1, wherein said lens means comprises a lens, and a lens system component, and said control means controls movement of at least one of said lens and said lens system component to effect focusing of the reflected light image.

11. The portable optical reader system of claim 1, wherein said optical means comprises:

a lens associated with said casing; and

a mirror mounted within said casing such that light entering said light

receiving opening passes twice through said lens.

12. The portable optical reader system of claim 1, further comprising:

a carriage having a focus adjusting mirror movable therewith to effect focusing;

pivot means for pivotably connecting said carriage to said casing;

drive linkage means associated with said carriage; and

electric motor means for drivingly moving said carriage about at least two axes via said drive linkage means.

13. The portable optical reader system of claim 1, further comprising:

a carriage having a focus adjusting mirror movable therewith to effect focusing;

drive means for movably adjusting said carriage relative to casing; and

cam means associated with said carriage such that said carriage moves said focus adjusting mirror about at least two axes during movable adjustment of said carriage.

14. A portable optical reader system for reading optical information over a substantial range of distances, comprising:

(a) a casing having an opening for facing optical information;

(b) adjustable optical means, disposed in said casing, for imaging at a predetermined reading position in said casing an image of optically readable information facing said opening by light reflected therefrom, said information located on the surface of an optically readable information carrier;

(c) reading sensor means, disposed at said predetermined reading position and having a light receiving plane, for converting an image into an electric signal;

(d) means for emitting a light beam, positioned in said casing, such that said light beam is reflected from a surface of an optically readable information carrier without being refracted by said optical means, said carrier at an unknown distance from the plane of said reading sensor means, such that said reflected light beam is refracted by said optical means onto the plane of said reading sensor means such that the optically refracted and reflected light beam is converted into an electric signal;

(e) means for obtaining a measure of any needed focus adjustment based in part on said electric signal produced by said reading sensor means from the refracted light beam reflected from said carrier surface, said measure of any needed focus adjustment including an indication of the direction and the distance to adjust said optical means;

(f) means for adjusting said optical means in accordance with said measure of needed focus adjustment such that said optical means focuses the image of optically readable information, located on the surface adjacent said information carrier, at said predetermined reading position; and

(g) means for producing a digital information set corresponding to the image of said optically readable information focused at said predetermined reading position.

15. A method of determining focusing quality according to a contrast gradient, comprising:

(a) reflecting a light beam from an object having an image to be focused;

(b) optically directing the image of said reflected light beam such that said light beam impinges on the surface of a photosensitive array;

(c) processing the output of said photosensitive array such that an image contrast gradient is determined; and

(d) focusing said image with said contrast gradient wherein focus quality is a function of the slope rate of the contrast gradient.

18. The method of determining focusing quality of claims 15, 16, or 17, further comprising the step of controlling the signal level of said array output such that said signal is maintained within a dynamic range.

16. A method of determining focusing quality according to a distribution of modulations, comprising:

(a) optically directing the image of an object to be focused such that the reflected light image of said object impinges on the surface of a photosensitive array;

(b) determining the modulation transfer function of at least certain areas of the image of said object from the output of said array;

(c) sorting the pulse modulations of said at least certain areas of the image of said object by pulse width;

(d) separating the sorted pulse modulations into a group of narrow pulse widths and a group of wide pulse widths;

(e) calculating the average pulse modulation of each group; and

(f) focusing said image with said average pulse modulation for each group wherein focus quality is a function of the ratio of the narrow pulse width group and wide pulse width group.

17. A method of determining the focusing quality of an image of pulses of various widths, comprising:

(a) optically directing the image of an object to be focused such that the reflected light image of said object impinges on the surface of a photosensitive array;

(b) determining the extreme values of bright pulses (B_i) and dark pulses (D_i) of the image of said object from the output of said array;

(c) determining the average values of bright extremes (B_o) and dark extremes (D_o);

(d) determining the number of pulse pairs (n);

(e) statistically evaluating said pulse data according to the following expression;

space="preserve" listing-type="equation">Q.sub.a =Σ

(A.sub.i -A.sub.o)/nA.sub.o +Σ

(B.sub.i -B.sub.o)/nB.sub.o

wherein;

Q_a is a measure of focus quality,

A_i is a current extreme value of a bright pulse,

A_o is an average value of bright extremes ((1/n)Σ

A_i),

B_i is a current extreme value of a dark pulse,

B_o is an average value of dark extremes ((1/n)Σ

B_i), and

n is the number of pulse pairs.