Self Calibrating Measurement System

Abstract

A measurement system that can self calibrate is disclosed. The measurement system comprising a first light source directed along a first axis and configured to illuminate a sample volume. The measurement system has a sensor aligned along a second axis and is configured to detect scattered light in the sample volume. The measurement system has a second light source aligned along the second axis that is configured to illuminate the sensor during a calibration procedure.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1—is a sectional view of the optical layout of a particulate measurement system in an example embodiment of the invention.

FIG. 2—is a first side view of particulate measurement system in an example embodiment of the invention.

FIG. 3—is a second side view, with the meniscus lens removed, of a particulate measurement system in an example embodiment of the invention.

FIG. 4—is a sectional view of the flow path of a particulate measurement system in an example embodiment of the invention.

FIG. 5—is a block diagram of the optical layout of the detection path in an example embodiment of the invention.

FIG. 6—is a block diagram of the optical layout when utilizing more than one detection path in an example embodiment of the invention.

FIG. 7—is a block diagram of the optical layout of the light source path in an example embodiment of the invention.

FIG. 7 a to 7g—are block diagrams of various arrangements and constructions of an aperture masks used to discriminate angle of scatter from particles in suspension in an example embodiment of the invention.

FIG. 8—is a block diagram of the optical layout of the view area of the suspension media in an example embodiment of the invention.

FIG. 9—is a block diagram of a particulate measurement system utilizing a plurality of light source paths in an example embodiment of the invention.

FIG. 10—is a block diagram of the optical layout of a particulate measurement system with an annulus virtual source and second light source in an example embodiment of the invention.

FIG. 11—is a block diagram of the optical layout of a particulate measurement system with an uncoated area of the convex lens surface and a second light source in an example embodiment of the invention.

FIG. 12—is a block diagram of the optical detail of an in situ calibration and verification means utilizing light from the primary light source and optical switching means to divert a portion of the primary source to the calibration and verification means in an example embodiment of the invention.

Claims

1. A measurement system comprising: a first light source directed along a first axis and configured to illuminate a sample volume;a sensor aligned along a second axis and configured to detect scattered light in the sample volume;a second light source aligned along the second axis and configured to illuminate the sensor, where the second light source only illuminates the sensor during a calibration procedure.

2. The measurement system of claim 1, where the second light source is an image of the first light source and a shutter placed between the second light source and the first sensor is used to switch the second light source on during the calibration procedure.

3. The measurement system of claim 1, where the second light source is in the shape of an annular ring.

4. The measurement system of claim 1, further comprising: a field lens located on the second axis and configured to uniformly spread the light from the second light source across the first sensor.

5. The measurement system of claim 1, further comprising: a reflecting lens aligned along the second axis where the reflecting lens has a first focus on the second axis and a second focus on the second axis where the second focus is between the first focus and the reflecting lens and where the second focus is positioned in the sample volume;a field lens located on the second axis and positioned such that the second focus of the reflecting lens occurs inside the field lens;a relay lens system aligned to the second axis where the relay lens system forms a first focus at the second focus of the reflecting lens and a second focus at the first sensor and where the first sensor is configured to detect scattered light near the second focus of the reflecting lens.

6. The measurement system of claim 5 where the second light source is in the shape of an annular ring located at an outer diameter of the reflecting lens.

7. The measurement system of claim 5 where a center section of the reflecting lens is uncoated and the second light source projects light through the center section of the reflecting lens.

8. The measurement system of claim 1, where the second axis is perpendicular to the first axis.

9. A method of calibrating a measurement system, comprising: illuminating a sample volume along a first axis with a first light source;detecting scattered light in the sample volume with a sensor aligned along a second axis;illuminating the sensor with a second light source aligned along the second axis when the measurement system is in a calibration mode.

10. The method of calibrating a measurement system of claim 9, where the second light source is an image of the first light source and a shutter placed between the second light source and the first sensor is used to switch the second light source on during the calibration procedure.

11. The method of calibrating a measurement system of claim 9, where the second light source is in the shape of an annular ring.

12. The method of calibrating a measurement system of claim 9, further comprising: locating a field lens on the second axis where the field lens uniformly spreads the light from the second light source across the first sensor.

13. The method of calibrating a measurement system of claim 9, further comprising: aligning a reflecting lens along the second axis where the reflecting lens has a first focus on the second axis and a second focus on the second axis where the second focus is between the first focus and the reflecting lens and where the second focus is positioned in the sample volume;locating a field lens on the second axis and positioned such that the second focus of the reflecting lens occurs inside the field lens;aligning a relay lens system to the second axis where the relay lens system forms a first focus at the second focus of the reflecting lens and a second focus at the first sensor and where the first sensor is configured to detect scattered light near the second focus of the reflecting lens.

14. The method of calibrating a measurement system of claim 13 where the second light source is in the shape of an annular ring located at an outer diameter of the reflecting lens.

15. The method of calibrating a measurement system of claim 13 where a center section of the reflecting lens is uncoated and the second light source projects light through the center section of the reflecting lens.