Method and apparatus for measurement of particle characteristics using light scattering and optical imaging

1. An apparatus which determines a particle size distribution from scattering measurements of particles and imaging of particles comprising:

a) a first light source which illuminates particles for detection of scattered light from particles, wherein said light source is turned on during a first period,

b) a second light source which illuminates particles for imaging of particles, wherein said light source is turned on during a second period,

c) at least one first detector which detects a first signal derived from light scattered from particles, wherein said first detector integrates said first signal over a first detection period,

d) at least one second detector which detects a second signal derived from an image of particles, wherein said second detector detects said second signal over a second detection period, wherein said second detection period and said first detection period do not comprise a common period in time, and wherein said first detection period and said second period do not comprise a common period in time,

e) means which determines a first particle size distribution from said detection of scattered light from particles,

f) means which determines a second particle size distribution from said imaging of particles, and

g) combining means which combines said first particle size distribution and said second particle size distribution to create a third particle size distribution with larger size range, wherein said third particle size distribution comprises three size regions which comprise a small size region, a size overlap region, and a large size region, wherein said third particle size distribution, in said small size region, comprises a portion of said first particle size distribution, wherein said third particle size distribution, in said large size region, comprises a portion of said second particle size distribution, and wherein said third particle size distribution, in said size overlap region, is derived from said first particle size distribution and said second particle size distribution.

2. The apparatus of claim 1 wherein said second detection period and said first period do not comprise a common period in time.

3. The apparatus of claim 1 wherein said second period and said second detection period occur while an integrator of said first detector is being reset, such that said first detector will not detect light originating from said second light source.

4. The apparatus of claim 1 wherein said first period and said first detection period occur while said second detector is not detecting light, such that said second detector will not detect light originating from said first light source.

5. The apparatus of claim 1 , wherein said second detector is the member of a group of detectors, wherein said group comprises a detector array.

6. The apparatus of claim 1 , wherein said first detector is the member of a group of detectors, wherein said group comprises a detector array.

7. The apparatus of claim 1 , wherein said combining means further comprises:

a) means which provides an overlap region of size for said first particle size distribution and said second particle size distribution,

b) means which utilizes a generally monotonic function of particle size to combine said first particle size distribution and said second particle size distribution in said overlap region to create said third particle size distribution in said overlap region.

8. The method of claim 7 wherein said generally monotonic function comprises a linear function.

9. A method which determines a particle size distribution from scattering measurements of particles and imaging of particles comprising:

a) providing a first light source which illuminates particles for detection of scattered light from particles, wherein said light source is turned on during a first period,

b) providing a second light source which illuminates particles for imaging of particles, wherein said light source is turned on during a second period,

c) providing at least one first detector which detects a first signal derived from light scattered from particles, wherein said first detector integrates said first signal over a first detection period,

d) providing at least one second detector which detects a second signal derived from an image of particles, wherein said second detector detects said second signal over a second detection period, wherein said second detection period and said first detection period do not comprise a common period in time, and wherein said first detection period and said second period do not comprise a common period in time,

e) determining a first particle size distribution from said detection of scattered light from particles,

f) determining a second particle size distribution from said imaging of particles, and

g) combining said second particle size distribution and said first particle size distribution to create a third particle size distribution with larger size range, wherein said third particle size distribution comprises three size regions which comprise a small size region, a size overlap region, and a large size region, wherein said third particle size distribution, in said small size region, comprises a portion of said first particle size distribution, wherein said third particle size distribution, in said large size region, comprises a portion of said second particle size distribution, and wherein said third particle size distribution, in said size overlap region, is derived from said first particle size distribution and said second particle size distribution.

10. The method of claim 9 , wherein said second detection period and said first period do not comprise a common period in time.

11. The method of claim 9 wherein said second period and said second detection period occur while an integrator of said first detector is being reset, such that said first detector will not detect light originating from said second light source.

12. The method of claim 9 wherein said first period and said first detection period occur while said second detector is not detecting light, such that said second detector will not detect light originating from said first light source.

13. The method of claim 9 wherein step (g) further comprises:

a) providing an overlap region of size for said first particle size distribution and said second particle size distribution,

b) utilizing a generally monotonic function of particle size to combine said first particle size distribution and said second particle size distribution in said overlap region to create said third particle size distribution in said overlap region.

14. The method of claim 13 wherein said generally monotonic function comprises a linear function.