Confocal scanning laser microscope having no moving parts

• US 4,827,125 A
• Filed: 04/29/1987
• Issued: 05/02/1989
• Est. Priority Date: 04/29/1987
• Status: Expired due to Fees

• Current Assignee: United States Department Of Health And Human Services (Government of the United States of America)
• Original Assignee: United States Department Of Health And Human Services (Government of the United States of America)
• Inventors: Goldstein, Seth R.
• Primary Examiner(s): Nelms, David C.
• Application Number:
  US07/044,021
• Time in Patent Office: 734 Days
• Field of Search: 250/234, 250/235, 250/213 VT, 250/310, 250/397, 250/216, 358/209, 350/507, 350/484, 356/434
• US Class Current: 250/234
• CPC Class Codes: G02B 21/0036 Scanning details, e.g. scanning stages

Abstract

A confocal scanning laser microscope has no moving parts and displays real time video images. The image of the scanned laser spot on the specimen is focused on the photocathode of an image dissector tube having an electron image deflection that is synchronized and aligned with the laser scan. This permits the confocal pinhole to be scanned at video rates. Acousto-optic deflectors are responsive to the frequencies of respective scan control signals to effect horizontal and vertical laser beam deflection.

Claims

1. The method of providing a real time video image of a specimen comprising the steps of:

(a) focusing a laser beam as an illuminated spot on a prescribed specimen plane;

(b) scanning the laser beam to move the focused illuminated spot in a predetermined scan pattern on said specimen plane;

(c) focusing an image of the moving focused illuminated spot onto a photocathode of an image dissector tube; and

(d) converting the image focused on said photocathode to a displayed video image.

2. The method according to claim 1 wherein step (d) includes the steps of:

(e) sampling successive locations of said photocathode in a sampling pattern configured to match said predetermined scan pattern and time-synchronized with said scan pattern; and

(f) transducing the intensity of the image at each sampled photocathode location to an electron current having an amplitude proportional to the image intensity of the sampled photocathode location at each instant of time.

3. The method according to claim 2 wherein step (b) includes scanning the laser beam to move the illuminated spot in a raster pattern comprising successive frames, each frame having multiple scan lines extending in a first direction in said specimen plane and arranged in a positional sequence extending in a second direction in said specimen plane, said second direction being orthogonally-oriented to said first direction, each line comprising a linear array of successive pixels.

4. The method according to claim 3 wherein said successive locations on said photocathode correspond to respective pixels in said raster pattern.

5. The method according to claim 4 wherein step (b) further includes the steps of:

(g) generating first and second control signals, each control signal having a repetitively variable frequency wherein the rate of frequency variation of said first control signal is much greater than the rate of variation of the frequency of said second control signal;

(h) deflecting said laser beam to move said illuminated spot in said first direction in which the spot position is a direct function of the frequency of said first control signal; and

(i) deflecting said laser beam to move said illuminated spot in said second direction in which the spot position is a direct function of the frequency of said second control signal.

6. The method according to claim 5 wherein step (c) comprises reflecting the image of the illuminated spot from the specimen plane to the photocathode of the image dissector tube.

7. The method according to claim 5 wherein step (c) comprises transmitting the image of the illuminated spot through the specimen plane to the photocathode of the image dissector tube.

8. The method according to claim 1 wherein step (b) includes scanning the laser beam to move the illuminated spot in a raster pattern comprising successive frames, each frame having multiple scan lines extending in a first direction in said specimen plane and arranged in a positional sequence extending in a second direction in said specimen plane, said second direction being orthogonally-oriented to said first direction, each line comprising a linear array of successive pixels.

9. The method according to claim 8 wherein step (b) further includes the steps of:

(g) generating first and second control signals, each control signal having a repetitively variable frequency wherein the rate of frequency variation of said first control signal is much greater than the rate of variation of the frequency of said second control signal;

(h) deflecting said laser beam to move said illuminated spot in said first direction in which the spot position is a direct function of the frequency of said first control signal; and

(i) deflecting said laser beam to move said illuminated spot in said second direction in which the spot position is a direct function of the frequency of said second control signal.

10. The method according to claim 8 wherein said frames are repeated at a rate at least equal to twenty-four frames per second.

11. The method according to claim 1 wherein step (c) comprises reflecting the image of the illuminated spot from the specimen plane to the photocathode of the image dissector tube.

12. The method according to claim 1 wherein step (c) comprises transmitting the image of the illuminated spot through the specimen plane to the photocathode of the image dissector tube.

13. A confocal scanning laser imaging system comprising:

laser source means for emitting a collimated beam of light;

lens means for focusing said beam to illuminate a spot in a plane of a specimen to be imaged;

scanning means for scanning said beam to move said illuminated spot in a predetermined pattern in said plane;

an image dissector tube having a photocathode with addressable locations and means for providing an output current proportional to the intensity of light impinging on the addressed location of the photocathode;

focusing means for focusing an image of said illuminated spot onto said photocathode; and

control means for addressing successive locations on said photocathode in synchronization with movement of said illuminated spot in said plane such that the addressed location is always at a portion of the focused image corresponding to the spot in said specimen plane illuminated by said laser beam.

14. The confocal scanning laser imaging system according to claim 13 wherein said scanning means includes means for forming said predetermined pattern as a television raster pattern having successive frames, each frame comprising multiple scan lines extending in a first direction in said plane and arranged in a positional sequence extending in a second direction in said plane, said second direction being orthogonally oriented to said first direction, each line comprising a linear array of successive pixels.

15. The confocal scanning laser imaging system according to claim 14 wherein said scanning means includes means for repeating said frames at a rate at least equal to twenty-four frames per second.

16. The confocal scanning laser imaging system according to claim 14 wherein the addressable locations on said photocathode correspond to respective pixels in said raster pattern.

17. The confocal scanning laser imaging system according to claim 14 further comprising:

synchronization means for generating first and second control signals, each control signal having a continuously repetitively variable frequency wherein the rate of frequency variation of said first control signal is much greater than the rate of variation of the frequency of said second control signal and;

wherein said scanning means includes;

acoustic-optic deflector means for deflecting said laser beam to move said illuminated spot in said first direction in which the spot position is a direct function of the frequency of said first control signal and;

further acoustic-optic deflection means for deflecting said laser beam to move said illuminated spot in said second direction in which the spot position is a direct function of the frequency of said second control signal.

18. The confocal scanning laser imaging system according to claim 13 wherein said focusing means comprises means for reflecting the image of the illuminated spot from the specimen to the photocathode of the image dissector tube.

19. The confocal scanning laser imaging system according to claim 13 wherein said focusing means comprises means for transmitting the image of the illuminated spot through the specimen to the photocathode of said image dissector tube.

20. The confocal scanning laser imaging system according to claim 13 wherein said scanning means includes no moving parts.

21. A method of providing a real time video image of a specimen, comprising the steps of:

(a) focusing a laser beam into an illuminated spot on a prescribed specimen plane;

(b) scanning the focused laser beam to move the illuminated spot in a predetermined scan pattern in said specimen plane;

(c) focusing an image of the moving illuminated spot onto an electo-optic imaging means having an array of plural individually addressable light sensor devices which light sensor devices may be each selectively addressed, enabled and read-out for providing an output signal corresponding to the incident light intensity impinging thereon;

(d) selectively addressing, enabling and reading-out individual light sensor devices in said array of said electro-optic imaging means in synchronization with scanned movement of said illuminated spot in said specimen plane to match said predetermined scan pattern such that the light sensor device currently being addressed, enabled and read-out is at a location in said array on which is incident a portion of the focused image of the moving illuminated spot, and outputting a signal from the light sensor device currently being addressed, enabled and read-out corresponding to the light intensity impinging thereon while so enabled; and

(e) converting signals output from said electro-optic imaging means into a displayed video image of said speciman plane.

22. A confocal scanning laser imaging system, comprising:

laser source means for emitting a collimated beam of light;

lens means for focusing said beam to illuminate a spot in a plane of a specimen to be imaged;

scanning means for scanning said beam to move said illuminated in a predetermined scan pattern in said specimen plane;

electro-optic imaging means having an array of plural individually addressable light sensor devices which light sensor devices may be each selectively individually addressed, enabled and read-out for providing an output signal corresponding to the incident light intensity impinging thereon;

focusing means for focusing an image of said moving illuminated spot onto said electro-optic imaging means; and

control means for selectively addressing, enabling and reading-out individual ones of said plural light sensor devices of said electro-optic imaging means in synchronization with scanned movement of said illuminated spot in said specimen plane, to match said predetermined scan pattern such that the one of said plurality light sensor devices being currently addressed, enable and read-out is always at a location in said array on which is incidentally impinging a portion of the focused image of the moving illuminated spot in said specimen plane.