Laser scanner with integral distance measurement system

• US 5,900,611 A
• Filed: 06/30/1997
• Issued: 05/04/1999
• Est. Priority Date: 06/30/1997
• Status: Expired due to Fees

• Current Assignee: Accu-Sort Systems Incorporated (Datalogic S.p.A.)
• Original Assignee: Accu-Sort Systems Incorporated (Datalogic S.p.A.)
• Inventors: Hecht, Kurt
• Primary Examiner(s): EVANS, FANNIE L
• Application Number:
  US08/884,809
• Time in Patent Office: 673 Days
• Field of Search: 356/375, 250/201.4, 250/201.6, 250/559.44, 250/568, 235/454, 235/462, 235/472
• US Class Current: 235/454
• CPC Class Codes: G06K 7/10861 sensing of data fields affixed to objects or articles, e.g. coded labels postal sorting B07C3/14, conveying articles B65G47/48

Abstract

The present invention relates to a scanner for reading coded symbologies. The invention uses a coherent, visible light source for illuminating the coded symbol during a scan and a detecting means for collecting the reflected light energy from the coded symbol. The invention also employs an invisible light source illuminating the coded symbol during the scan and a one-dimensional position-sensitive detector whose field of view receives images of the illuminating beam. The position-sensitive detector outputs a current which is processed to detect the presence and compute the distance of an object being scanned. Both the visible and invisible light sources from the scanner travel along a shared, coaxial path to and from the object.

Claims

1. An apparatus for reading coded symbologies on an object at an indeterminate distance from the apparatus comprising:

means for generating first and second scan beams that repetitiously move across a common scanning zone of a predetermined depth such that the beams intercept any object disposed within said scanning zone;

first and second detecting means, said first detecting means having a spot field of view of said first scanning beam reflected from an object within said scanning zone, said second detecting means having a line field of view of said second scanning beam reflected from an object within said scanning zone;

said first detecting means receiving reflected images of said first scan beam continuously as said first scan beam moves across an object in said scanning zone and outputting a current proportional to said reflected images;

said second detecting means receives reflected images of said second scan beam continuously as said second scan beam moves across an object in said scanning zone and outputting a signal which varies with the placement of said detection means to the object within the depth of said scanning zone; and

means for calculating the placement of the object within said predetermined scanning zone based on said reflected images of said second beam.

2. The apparatus of claim 1 wherein said first detecting means is a photodiode.

3. The apparatus of claim 2 wherein said photodiode is sensitive only to frequencies in the visible spectrum.

4. The apparatus of claim 1 wherein said second detecting means is a position-sensitive device (PSD).

5. The apparatus of claim 4 wherein said (PSD)is sensitive only to frequencies in the invisible spectrum.

6. The apparatus of claim 1 wherein said means for calculating includes an arithmetic processing unit (APU) which recieves said signal from said second detecting means and continuously calculates distance values as the object travels through said predetermined scanning zone and a logic processor which assembles said distance values into a distance profile after a scan.

7. The apparatus of claim 6 wherein said object distance values between consecutive scan distance profiles include common and non-common distance values;

said common distance values are discarded prior to determining said placement of the object; and

said non-common distance values determine said placement of the object for the next scan.

8. The apparatus of claim 7 further comprising a focusing means for said first scan beam responsive to said non-common distance values.

9. An apparatus for reading coded symbologies on an object at an indeterminate distance from the apparatus traveling on a moving conveyor comprising:

a first light source which generates a visible light beam;

a second light source which generates an invisible light beam;

said visible light beam is directed through a hot mirror and through an aperture in a cold mirror onto a mirrored wheel to create a visible moving beam defining a scanning zone;

said invisible light beam is directed to said hot mirror, said hot mirror positioned at a 45 degree angle with respect to said invisible light beam;

said invisible light beam reflects off of said hot mirror and through said cold mirror onto said mirrored wheel to create an in visible moving beam in said scanning zone;

a first detector having a spot field of view sensitive to visible light;

a second detector having a line field of view sensitive to invisible light;

said first detector directed at said cold mirror at a 45 degree angle with respect to said spot field of view;

said spot field of view redirected to said mirrored wheel continuously viewing said visible moving light beam in said scanning zone;

said second detector directed at said hot mirror at a 45 degree angle with respect to said linear field of view;

said linear field of view redirected through said cold mirror onto said mirrored wheel continuously viewing said invisible moving beam in said scanning zone;

said invisible moving beam is directed at a predetermined angle relative to an object in said scanning zone;

said line field of view is directed at said invisible moving beam in an angular orientation to an object in said scanning zone which is offset from said predetermined angle with said line field of view crossing said invisible moving beam; and

said second detector outputting a signal to a logic processor which computes said offset distance of an invisible moving beam intercept point and an object distance at that point in time.

10. The apparatus of claim 9 wherein said object distance is calculated using the formula ##EQU2## where θ

is a fixed angle and d is said offset distance within said line field of view from an image point to a minimum object distance within said scanning zone.

11. The apparatus of claim 10 wherein said second detector is a position-sensitive detector (PSD) that outputs a photocurrent which represents a distance from the apparatus to an object at each image point during a scan.

12. The apparatus of claim 11 wherein object distances of a prior scan are compared with object distances of a subsequent scan determining common and non-common object distances between said prior and subsequent scans and said non-common object distances determine the object distance.

13. The apparatus of claim 12 further comprising a focusing means responsive to said non-common object distances for focusing said visible light beam.