Stray light compensating unitary light tube for mounting optical sensor components on an ink-jet printer carriage

• US 6,172,690 B1
• Filed: 03/02/1999
• Issued: 01/09/2001
• Est. Priority Date: 10/31/1995
• Status: Expired due to Term

• Current Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Original Assignee: Hewlett-Packard Company (HP Inc.)
• Inventors: Gros, Xavier, Angulo, Emilio, Beauchamp, Robert W.
• Primary Examiner(s): Dang, Hung Xuan
• Application Number:
  US09/261,015
• Time in Patent Office: 679 Days
• Field of Search: 250/216, 250/226, 250/208.2, 250/578.1, 347/19, 347/37, 347/40, 347/43, 356/372, 356/402, 356/445, 356/448
• US Class Current: 347/19
• CPC Class Codes: B41J 11/008 Controlling printhead for accurately positioning print image on printing material, e.g. with the intention to control the width of margins
• CPC Class Codes: B41J 2/2135 Alignment of dots

Abstract

A carriage-mounted optical sensor for an ink-jet hard copy apparatus includes a unitary light tube member which holds the optical components in fixed positions relative to each other as well as relative to an outer protective casing which attaches to the carriage. The light tube member serves as a cap to capture two LEDs between itself and a protective casing, to capture an optical lens between itself and a photocell holder, and to directly engage the casing. An inner wall having light redirecting features provides an improved light path cylinder and the device obtains a more accurate representation of the test pattern mark shape, reflectance value, and position.

Claims

1. An ink-jet hard copy apparatus having a carriage for carrying an optical sensor across print media, comprising:

a photocell;

a light tube having a first passageway facing toward the media;

a light source positioned by said light tube to transmit emitted light through said first passageway, said light tube having an inner wall portion for directing said emitted light toward a predetermined portion of the media; and

a second passageway in said light tube facing toward said photocell and in optical communication with said predetermined portion of the media for allowing said emitted light to be reflected from said predetermined portion of the media to said photocell, wherein the second passageway has means for redirecting light not reflected in an angularly normal path from said portion of the media toward said photocell away from said photocell.

2. The apparatus as set forth in claim 1, wherein said means for redirecting light further comprises:

an inner wall of said second passageway, said wall having a contour for redirecting non-perpendicular light away from said photocell.

3. The apparatus as set forth in claim 1, wherein said means for redirecting light further comprises:

a plurality of protrusions extending inwardly toward said second passageway.

4. The apparatus as set forth in claim 3, further comprising:

said passageway is a cylindrical tube construct and said protrusions are circumferential ribs.

5. The apparatus as set forth in claim 3, further comprising:

said passageway is a cylindrical tube construct and said protrusions are a continuous helical rib.

6. The apparatus as set forth in claim 3, further comprising:

said passageway is a cylindrical tube construct and said protrusions are formed by a thread within at least a portion of an inner wall of said tube construct.

7. The apparatus as set forth in claim 1, wherein said means for redirecting light further comprises:

an inner wall of said second passageway, said wall having a surface for absorbing non-perpendicular light within said passageway.

8. The apparatus as set forth in claim 7, comprising:

said surface is a matte black finish.

9. An optical sensor device on a moveable carriage of an ink-jet hard copy apparatus in which said carriage carries printheads across media, comprising:

a photodetection element;

a holder for supporting said photodetection element, said holder having an elongated enclosed light passage in optical communication with said photodetection element and having internal walls including reflectors for diverting light not parallel to said walls away from said photodetection element;

a lens in said light passage;

a unitary light tube connected with said holder; and

at least one light source which is in optical communication with said light tube for transmitting light to a portion of said media, said light tube also allowing reflected light from said portion of said media to pass through both said lens and said light passage to said photodetection element.

10. An optical sensor system on a carriage of an ink-jet hard copy apparatus, comprising:

at least one light source on the carriage;

a photocell device on the carriage;

a lens on the carriage; and

a unitary light tube for positioning said photocell device, said lens and said light source in predetermined positions relative to each other as well as relative to print media passing through said apparatus such that light is transmitted from said at least one light source through said light tube to the print media and then reflected from the print media through said lens to said photocell device, said light tube including an inner wall structured for diverting light that is not reflected in a straight line from said print media to said photocell away from said photocell device.