Linear optical loss probe
View Patent ↗An optical loss probe utilized as a bioreactor process monitor manifesting a substantially linear response in optical loss vs. concentration of scatterers present in an aqueous medium in the range of between about 0 AU and about 4.0 AU, said probe comprising: i) a light source, ii) an optical detector, and iii) an optical gap between said light source and said optical detector, said optical detector having a receiving aperture configured such that the solid angle of acceptance of the light passing through said optical gap and impinging on said optical detector is less than π/50 radians.
1. An optical loss probe manifesting a substantially linear response in optical loss vs. concentration of scatterers in an aqueous medium, said probe comprising:
i) a source of light having a wavelength between about 810 nm and 850 nm
ii) an optical detector,
iii) an optical gap between said light source and said optical detector, said optical detector having a receiving aperture configured such that the solid angle of acceptance of the light passing through said optical gap and impinging on said optical detector is less than π/50 radians.
2. An optical loss probe in accordance with claim 1 wherein said substantially linear response is in the range between about 0 AU and about 4.0 AU.
3. An optical loss probe in accordance with claim 1 wherein said light source is substantially monochromatic.
4. An optical loss probe in accordance with claim 3 wherein said light source is a laser.
5. An optical loss probe in accordance with claim 4 wherein said laser is a continuous wave laser.
6. An optical loss probe in accordance with claim 4 wherein said laser is a vertical cavity surface emitting laser, a fiber coupled laser or an edge emitting laser.
7. An optical loss probe in accordance with claim 4 wherein said laser is collimated such that the diameter of the laser beam is within a factor of 10 of the diameter of the receiving aperture.
8. An optical loss probe in accordance with claim 4 wherein said light is modulated at a frequency in the range of 200 Hz to 20 KHz.
9. An optical loss probe in accordance with claim 1 wherein said light source is substantially spatially coherent.
10. An optical loss probe in accordance with claim 1 wherein said light source emits a beam which is substantially Gaussian.
11. An optical loss probe in accordance with claim 10 wherein said aperture has a radius >2.3 times the radius of said beam.
12. An optical loss probe in accordance with claim 1 wherein said light source emits a beam which is substantially Super-Gaussian or Flat Top.
13. An optical loss probe in accordance with claim 12 wherein said aperture has a diameter <75% of the beam diameter.
14. An optical loss probe in accordance with claim 1 wherein said light has a wavelength of approximately 830 nm.
15. An optical loss probe in accordance with claim 1 wherein said detector comprises a lock in amplifier.
16. An optical loss probe in accordance with claim 1 wherein said detector comprises a photo-detector.
17. An optical loss probe in accordance with claim 16 wherein said detector comprises a photodiode.
18. An optical loss probe in accordance with claim 1 wherein said detector comprises a silicon or avalanche photodiode.
19. The optical loss probe of claim 1 , wherein at least one of the light source and the detector are physically separable from the sample cell which defines the optical gap.
20. A method for determining the concentration of scatterers dispersed in an aqueous medium comprising directing a light beam having a wavelength between about 810 nm and 850 nm across an optical gap containing said dispersed scatterers onto an optical detector having a receiving aperture configured such that the solid angle of acceptance of the light passing through said optical gap and impinging on said optical detector is less than π/50 radians.
21. A method in accordance with claim 20 wherein said optical detector utilizes phase sensitive detection.
22. A method in accordance with claim 20 wherein said light beam has a wavelength of approximately 830 nm.