Retro-reflector assembly and opacity monitor incorporating same

• US 7,429,112 B2
• Filed: 05/08/2006
• Issued: 09/30/2008
• Est. Priority Date: 06/16/2005
• Status: Active Grant

• Current Assignee: Land Instruments International Ltd. (Ametek Incorporated)
• Original Assignee: Land Instruments International Ltd. (Ametek Incorporated)
• Inventors: Metcalfe, Stuart Francis
• Primary Examiner(s): Cherry; Euncha P
• Application Number:
  US11/429,773
• Publication Number:
  US 20060285116A1
• Time in Patent Office: 876 Days
• Field of Search: 359/529, 359831-838, 359/530
• US Class Current: 359/529
• CPC Class Codes: G01N 21/534 by measuring transmission alone, i.e. determining opacity
• CPC Class Codes: G02B 5/124 plural reflecting elements forming part of a unitary plate or sheet
• CPC Class Codes: G02B 7/181 with means for compensating for changes in temperature or for controlling the temperature; thermal stabilisation

Abstract

A retro-reflector assembly (1) for incorporating in an opacity monitor, includes several small corner-cube prisms (2) of cylindrical section. The invention also includes an opacity monitor incorporating a retro-reflector assembly as defined above.

Claims

1. A retro-reflector assembly for incorporation in an opacity monitor, said assembly comprising several corner-cube prisms each of which is of glass and each of which has a cylindrical external surface by which said prisms are embedded in closely spaced relationship in a metal substrate, which metal substrate either imparts, by its high thermal conductivity, compared with the thermal conductivity of said glass prisms, thermal stability to said assembly, and/or which metal substrate is thermally controlled to attain thermal stability.

2. A retro-reflector assembly as claimed in claim 1, wherein the number of prisms is between 2 and 50.

3. A retro-reflector assembly as claimed in claim 1, wherein said prisms each have a diameter between 3 mm and 20 mm.

4. A retro-reflector assembly as claimed in claim 1, wherein said metal substrate is an aluminium block.

5. A retro-reflector assembly as claimed in claim 1, wherein active faces of said prisms are sealed within a chamber inside said metal substrate.

6. A retro-reflector assembly as claimed in claim 5, wherein said chamber is closed off by a cover with an ‘

O’

-ring or similar sealing device.

7. A retro-reflector assembly as claimed in claim 6, wherein said cover is secured to said metal substrate by screws.

8. A retro-reflector assembly as claimed in claim 5, wherein said chamber also contains a desiccant.

9. A retro-reflector assembly as claimed claim 1, wherein said metal substrate is temperature-controlled by means of an embedded, or otherwise attached, heating element.

10. An opacity monitor incorporating a retro-reflector assembly, said assembly comprising several corner-cube prisms each of which is of glass and each of which has a cylindrical external surface by which said prisms are embedded in closely spaced relationship in a metal substrate, which metal substrate either imparts, by its high thermal conductivity, compared with the thermal conductivity of said glass prisms, thermal stability to said assembly, and/or which metal substrate is thermally controlled to attain thermal stability.