Reference laser beam sampling apparatus

• US 5,844,685 A
• Filed: 07/30/1996
• Issued: 12/01/1998
• Est. Priority Date: 07/30/1996
• Status: Expired due to Term

• Current Assignee: Siemens Healthcare Diagnostics Incorporated (Siemens AG)
• Original Assignee: Bayer Corporation (Bayer AG)
• Inventors: Gontin, Richard
• Primary Examiner(s): Font, Frank G.
• Assistant Examiner(s): STAFIRA, MICHAEL PATRICK
• Application Number:
  US08/692,933
• Time in Patent Office: 854 Days
• Field of Search: 356/442, 356/336, 356/337, 356/338, 356/339, 356/343, 356/400, 356/441, 356/72, 356/73, 356/39, 356/318, 356/417, 356/38, 356/433, 356/436, 356/432, 356/434, 422/82.05, 436/534, 436/536, 436/538, 436/541, 436/805, 436/63, 436/172, 250/458.1, 250/222.2, 250/961.2
• US Class Current: 356/433
• CPC Class Codes: G01N 15/1436 the optical arrangement forming an integrated apparatus with the sample container, e.g. a flow cell
• CPC Class Codes: G01N 15/1459 the analysis being performed on a sample stream
• CPC Class Codes: G01N 2015/1447 Spatial selection
• CPC Class Codes: G01N 2201/0633 Directed, collimated illumination

Abstract

Apparatus for sampling a laser beam used in an analytical instrument, e.g., a clinical hematology or flow cytometer instrument, for measuring absorption by particles suspended in a stream moving through a flow cell. The laser beam is typically passed through a mask, e.g., a beam shaping aperture, to shape the beam. The shaped beam is then passed through a beam splitter, located downstream of the beam shaping aperture, so that one part of the shaped beam strikes the flow cell (e.g., is focused onto the moving stream of particles), and a second part is diverted to obtain a reference measurement of the beam about to strike the flow cell. An absorption measurement is obtained of the light passing through the flow cell, and a difference circuit is used to obtain a difference signal relating the differences between the measured absorption and the unabsorbed reference sample of the initial beam intensity. The laser source may be a laser diode and a spatial filter may be used to produce the laser beam to be passed through the beam shaping aperture.

Claims

1. An instrument for measuring absorption of a laser beam by particles suspended in a moving fluid, the instrument comprising:

a laser beam source having a laser beam output;

a mask having an aperture, the mask being positioned in optical alignment with the laser beam to shape the laser beam;

a flow cell having a channel through which a thin stream of suspended particles is passed, the flow cell channel being positioned to intersect an axis of the laser beam, such that the suspended particles absorb a portion of the laser beam and permit an unabsorbed portion to exit the flow cell;

a detector positioned relative to said laser beam to measure an intensity of said unabsorbed laser beam portion;

a beam sampler interposed between said mask and said flow cell having an output corresponding to an initial beam intensity; and

a difference circuit having as inputs said initial beam intensity and said unabsorbed beam intensity from said flow cell, and having a beam absorption output corresponding to a difference between said unabsorbed beam intensity from said flow cell and said initial beam intensity.

2. The instrument of claim 1, wherein said laser source is a laser diode.

3. The instrument of claim 2, wherein said beam sampler comprises a beam sampling mirror positioned in a path of the laser beam, said mirror having a partially reflective surface to reflect a sample of said beam in a second path, and a detector positioned in said second path having an output corresponding to an intensity of said sample of said beam.

4. The instrument of claim 2 further comprising a spatial filter interposed between said laser diode and said beam sampler.

5. A method of measuring absorption of a laser beam by particles suspending in a moving fluid in a flow cell, comprising the steps of:

a) generating a laser beam;

b) passing the laser beam through an aperture in a mask, thereby shaping the laser beam;

c) passing the shaped laser beam through a beam sampler interposed between said mask and said flow cell, thereby providing a shaped beam sample and a remaining shaped beam;

d) passing the remaining shaped beam through the flow cell to impinge on said suspended particles in a moving stream in said flow cell;

e) detecting a first signal corresponding to an intensity of the remaining shaped beam passing through said moving stream of particles;

f) detecting a second signal corresponding to an intensity of said shaped beam sample passing through said flow cell; and

g) determining a difference between said first and second signals, said difference corresponding to the absorption of the laser beam by said moving suspended particles.

6. The method of claim 5 wherein step a) further comprises i) generating a beam output from a laser diode, and ii) spatially filtering said laser diode output to form said laser beam.