Microscope system for observing moving particles

• US 4,136,950 A
• Filed: 11/08/1976
• Issued: 01/30/1979
• Est. Priority Date: 11/08/1976
• Status: Expired due to Term

• Current Assignee: Labrum Engineering Incorporated
• Original Assignee: Labrum Engineering Incorporated
• Inventors: Labrum, Joseph H., Stewart, Donald R.
• Primary Examiner(s): Buczinski, S. C.
• Application Number:
  US05/739,426
• Time in Patent Office: 813 Days
• Field of Search: 356/28, 356/5, 358/105, 358/107, 250/222 PC
• US Class Current: 356/28
• CPC Class Codes: G01N 15/0205 by optical means

Abstract

A microscope system for observing moving particles makes use of a television camera for producing a continuing series of images of such particles. A source of light pulses illuminate the particles with each pulse for a period short enough to stop their movement for the camera. The light source and camera are synchronized so that the light pulses occur only between times that the camera produces image-information signals. For obtaining particle size measurements, a single light pulse during a time that the camera is not producing image-information signals is sufficient. For obtaining paticle velocity measurements, two light pulses are required so that a "double exposure" occurs at the camera during a time that the camera is not producing image-information signals.

Claims

1. A microscope system for observing and determining the velocity of moving particles, comprising a television camera which includes an image sensitive device, having short term storage capability, and a scan system for producing electrical, image-information signals representative of the image sensed by said device, the scan system being adapted to successively scan said device, with blank periods interposed between successive scans, no such signals being produced during the blank periods, and the storage capability of said image-sensitive device being such that an image is stored until said device is scanned and the image is converted to electrical, image-information signals;

a light source adapted to produce a series of light pulse pairs, the second pulse of each pair occurring a present time interval after the first pulse of that pair, and each pulse pair having a duration less than the duration of a blank period of the camera;

means for synchronizing the light source and the camera, so that any light pulse pairs occur during a blank period of the camera;

magnifying means for focusing the camera on an object plane between the light source and the camera, so that the camera sees a magnified image of anything placed in the object plane; and

means for monitoring the camera picture to obtain desired information.

2. A microscope system according to claim 1, wherein the synchronizing means is adapted to cause light pulse pairs to occur during blank periods of the camera which immediately follow a predetermined number of blank periods without light pulse pairs.

3. A microscope system according to claim 2, wherein the synchronizing means is adapted to cause light pulse pairs during every fourth blank period.

4. A microscope system according to claim 1, wherein shading corrector means is located between the camera and the magnifying means, so that the camera sees a field of substantially uniform brightness.

5. A microscope system according to claim 4, wherein the shading corrector is a piece of film that has been exposed in position between the camera lens and magnifying means and has been developed as a negative.

6. A microscope system according to claim 5, wherein the film is a glass photographic plate.

7. A microscope system according to claim 5, wherein the lasers are nitrogen lasers.

8. A microscope system according to claim 1, wherein a collimator and spatial filter is positioned between the light source and the object plane, so that the light reaching the object plane is collimated light with substantially all but zero order diffraction patterns removed therefrom.

9. A microscope system according to claim 8, wherein the spatial filter and collimator includes a focusing lens, a plate having an aperture and arranged so that the aperture passes the light contained in the center spot of a diffraction pattern but so that the plate blocks the remainder of the diffraction pattern when such pattern is focused on the plate by the focusing lens, and a collimating lens which collimates the light passed by the aperture.

10. A microscope system according to claim 1, wherein the light source is a laser.

11. A microscope system according to Claim 10, wherein the laser is a nitrogen laser.

12. A microscope system according to claim 7, wherein each of the two light pulse sources is a laser.

13. A microscope system for observing and determining the velocity of moving particles, comprising a television camera which includes an image sensitive device, having short term storage capability, and a scan system for producing electrical, image-information signals representatives of the image sensed by said device, the scan system being adapted to successively scan said device, with blank periods interposed between successive scans, no such signals being produced during the blank periods, and the storage capability of said image-sensitive device being such that an image is stored until said device is scanned and the image is converted to electrical, image-information signals;

two laser light sources each adapted to produce a series of light pulses, one of said laser light sources being connected to produce a light pulse a preset time interval after the other laser light source produces a light pulse, the total duration of both pulses and the time interval between the pulses being less than the duration of a blank period of the camera;

means for synchronizing the laser light sources and the camera, so that any light pulses occur during a blank period of the camera;

magnifying means for focusing the camera on an object plane between the light source and the camera, so that the camera sees a magnified image of anything placed in the object plane;

a collimator and spatial filter positioned between the light source and the object plane so that the light reaching the object plane is collimated light with substantially all but zero order diffraction patterns removed therefrom; and

means for monitoring the camera picture to obtain desired information.

14. A microscope system according to claim 1, wherein the light source includes two light pulse sources arranged so that one source produces the first light pulse of the light pulse pair and a second source produces the second light pulse of the light pulse pair, and means are included for aligning the light from the two pulse sources so that it travels the same path through the object plane and into the camera.

15. A microscope system according to claim 7, wherein the aligning means causes the light from the two pulse sources to travel the same path through collimator and spatial filter.

16. A method of measuring the velocity of moving particles, comprising the steps of directing the particles through an object plane of a television camera, whereby they are focused on the image-sensitive device of the television camera;

illuminating the particles in said object plane by a pulse of light short enough to stop the action of the particles, thereby creating an image of the particles on the image-sensitive device;

illuminating the particles by a second pulse of light short enough to stop the action of the particles at a time after the first light pulse, so that some of the particles in the object plane at the time of the first pulse are still in the object plane at the time of the second pulse, said second pulse creating a second image of the particles on the image-sensitive device;

causing a scan system to scan the image-sensitive device only after both light pulses have occurred and to convert the images on the image-sensitive device to electrical image-information signals;

converting the electrical signals into information from which the distances traveled by a particle between the two images of said particle can be determined;

determining the distance such a particle has traveled between the two images, and dividing the distance obtained by the time between the two light pulses to determine the velocity of the particle.

17. A method according to claim 16, including the step of storing the electrical image-information signals produced by the scan system;

and repeating the several enumerated steps prior to converting the electrical signals into information from which the distance traveled is determined, more than once each second during the time particles are in the object plane.