Flow cytometer and laser optics assembly thereof
A flow cytometer of a blood analyzer including a transverse-electric (TE) laser diode, a flow cell, a quarter wave plate (QWP), a plurality of lenses, and a side scatter detector. The TE laser diode is configured to output a laser beam along an optical axis and has a fast axis full width at half maximum (FWHM) divergence of from about 16 degrees to about 25 degrees. The QWP is disposed along the optical axis between the TE laser diode and the flow cell and configured to circularly polarize the laser beam. The plurality of lenses is disposed between the TE laser diode and the flow cell and configured to focus the laser beam at the flow cell.
1. A method of detecting cells in a blood sample, comprising:
flowing a blood sample, together with a sheath fluid, through a flow cell;
emitting, from a laser diode, a laser beam along an optical axis;
passing the laser beam through a quarter wave plate (QWP) disposed along the optical axis between the laser diode and the flow cell to circularly polarize the laser beam as it passes therethrough;
passing the laser beam through a plurality of lenses disposed between the laser diode and the flow cell to focus the laser beam at the flow cell; and
detecting side-scattered light from the flow cell.
2. The method according to claim 1 , wherein emitting the laser beam from the laser diode includes emitting the laser beam from a transverse-electric (TE) laser diode.
3. The method according to claim 1 , wherein emitting the laser beam includes emitting the laser beam having a fast axis full width at half maximum (FWHM) divergence of from about 16 degrees to about 25 degrees.
4. The method according to claim 1 , wherein detecting the side-scattered light includes detecting the side-scattered light at angles of about 50 degrees to about 120 degrees relative to the optical axis.
5. The method according to claim 4 , further comprising detecting scattered light from the flow cell at least at angles less than about 30 degrees relative to the optical axis.
6. The method according to claim 5 , wherein scattered light from the flow cell is detected at least at angles of about 11.5 degrees to about 15.5 degrees relative to the optical axis.
7. The method according to claim 5 , wherein scattered light from the flow cell is detected at least at angles of about 2.0 degrees to about 2.4 degrees relative to the optical axis.
8. The method according to claim 4 , wherein the side-scattered light intensity detected from the flow cell is detected at angles of from about 67 degrees to about 89 degrees relative to the optical axis.
9. The method according to claim 4 , wherein a maximum sensitivity to side-scattered light intensity is set at about 78 degrees relative to the optical axis.
10. The method according to claim 1 , wherein the QWP is positioned relative to the laser diode such that a centroid angle of incidence of the laser beam on the QWP is equal to or less than about 7 degrees.
11. The method according to claim 1 , wherein the laser beam passing through the QWP is right-handedly or left-handedly circularly polarized by the QWP.
12. The method according to claim 1 , wherein the plurality of lenses includes a collimating lens and wherein the laser beam passes through the collimating lens before the QWP.
13. The method according to claim 12 , wherein the plurality of lenses further includes an objective lens and wherein the laser beam passes through the objective lens after the QWP.
14. The method according to claim 1 , wherein the laser beam, at a core stream of the flow cell, defines a beam 1/e 2 diameter in a direction parallel to the flowing of about 6.7 μm to about 9 μm.
15. The method according to claim 14 , wherein the laser beam, at the core stream of the flow cell, defines a beam 1/e 2 diameter in a direction perpendicular to the flowing of up to about 210 μm.
16. The method according to claim 1 , wherein a power output of the laser diode for emitting the laser beam is at least 10 mW.
17. The method according to claim 1 , wherein a power output of the laser diode for emitting the laser beam is at least 20 mW.
18. The method according to claim 1 , wherein the detected side-scattered light is utilized to detect at least one of reticulocytes or granulocytes in the blood sample.
19. The method according to claim 1 , wherein the detected side-scattered light is utilized to detect reticulocytes and granulocytes in the blood sample.