Optical reader with dual vertically oriented photoemitters

• US 5,034,619 A
• Filed: 09/21/1989
• Issued: 07/23/1991
• Est. Priority Date: 09/21/1989
• Status: Expired due to Term

• Current Assignee: Welch Allyn Incorporated
• Original Assignee: Welch Allyn Incorporated
• Inventors: Hammond, Charles M. Jr.
• Primary Examiner(s): Nelms, David C.
• Application Number:
  US07/411,325
• Time in Patent Office: 670 Days
• Field of Search: 250/566, 250/568, 250/569, 235/454, 235/455, 235/462, 235/472
• US Class Current: 250/569
• CPC Class Codes: G06K 7/14 using light without selection of wavelength, e.g. sensing reflected white light G06K7/10831 - G06K7/1097 take precedence

Abstract

An optical reader is designed to be insensitive to specular reflection, particularly at tapered lead-in areas to the left and right of a coded record on a record member. The optical reader includes a photosensor that is oriented with its optical axis along the reader optical center line so as to be situated substantially perpendicular to the record member passing through a reader slot. There are upper and lower LEDs only, which are disposed respectively on opposite sides of the optical center line in a vertical plane. That is, the LEDs lie in a plane perpendicular to the path of a record member being swiped through the slot. In this way, no specular reflection at the lead-in areas will fall onto the photosensor. In addition, the effect of specular reflection occurring at areas of the record member in a plane perpendicular to its path of travel is reduced by a factor of two over an optical reader using a single LED.

Claims

1. An optical reader with reduced sensitivity to specular reflection from a surface of a record member that contains a coded record and has a substantially transparent lamination overlying said record member to cover the coded record, the surface of said record member having an inclined region;

said optical reader comprising an optical scanner having a center line, the center line being optically aligned with the coded record on said record member;

said optical scanner including a photosensor having an optical axis substantially along the center line of said optical scanner;

said optical scanner further comprising first and second photoemitters respectively situated on opposite sides of the center line of said optical scanner and disposed in a common plane containing the center line of said optical scanner, said common plane being oriented to laterally intersect the inclined region when said region is optically aligned with the center line of said optical scanner;

whereby specular reflection occurring at the inclined region is not coupled into said photosensor.

2. An optical reader according to claim 1 further comprising a one-piece optical housing including mounting plates above and below said optical center line for mounting said photoemitters.

3. An optical reader according to claim 2 wherein said optical housing has an aperture situated on said housing between said mounting plates, a tube extending perpendicular to the plane of said photoemitters, a mirror deflecting light entering said aperture into said tube, and photosensor mounting means within said tube on which said photosensor is mounted.

4. An optical reader according to claim 1 wherein said photoemitters are oriented to have optical axes that are each incident on the record member at about 30°

from normal.

5. A method of reducing the sensitivity of an optical scanner to specular reflection from a surface of a record member that contains a coded record and has a substantially transparent lamination overlying said record member to cover the coded record, the surface of said record member having an inclined region, said method comprising the steps of:

optically aligning a center line of said optical scanner with the coded record on the record member;

reading the coded record on the record member with first and second photoemitters and a photosensor of said optical scanner, said photoemitters being respectively situated on opposite sides of the center line of said optical scanner, and disposed in a common plane containing the center line of said optical scanner, said common plane being oriented to laterally intersect the inclined region when said region is optically aligned with the center line of said optical scanner;

whereby specular reflection occurring at the inclined region is not coupled into said photosensor.

6. A method of reducing the sensitivity of an optical scanner, as recited in claim 5, further comprising the step of orienting said first and said second photoemitters to have optical axes that are each incident on the record member at about 30°

from normal.

7. An optical reader with reduced sensitivity to specular reflection from a surface of a record member that contains a bar code symbol and has a substantially transparent lamination overlying said record member to cover the bar code symbol and lead-in areas at lateral ends of the bar code symbol;

said optical reader comprising a housing having a slot therein defining a planer path of travel for said record member, said record member being drawn past an optical scanner in said housing adjacent said path of travel, and said optical scanner having an optical center line disposed a predetermined distance from a base of said slot to coincide with said bar code symbol on said record member in said slot;

said optical scanner including a photosensor having an optical axis along said optical center line so as to be situated substantially perpendicular to said record member passing through said slot; and

first and second photoemitters respectively situated on opposite sides of said optical center line in a common plane containing the optical center line of said optical scanner, said common plane being perpendicular to the path of travel of said record member as it passes through said slot, so that specular reflection occurring at the lead-in areas is not coupled into said photosensor.

8. An optical reader according to claim 7 further comprising a one-piece optical housing including mounting plates above and below said optical center line for mounting said photoemitters.

9. An optical reader according to claim 8 wherein said optical housing has an aperture situated on said housing between said mounting plates, a tube extending perpendicular to the plane of said photoemitters, a mirror deflecting light entering said aperture into said tube, and photosensor mounting means within said tube on which said photosensor is mounted.

10. An optical reader according to claim 7 wherein said photoemitters are oriented to have optical axes that are each incident on said record member at about 30°

from normal.