Scanning microscope employing improved scanning mechanism

• US 5,225,923 A
• Filed: 07/09/1992
• Issued: 07/06/1993
• Est. Priority Date: 07/09/1992
• Status: Expired due to Fees

• Current Assignee: GSI Lumonics Corporation (Novanta Inc.)
• Original Assignee: General Scanning, Inc. (KOCH Industries Incorporated)
• Inventors: Montagu, Jean I.
• Primary Examiner(s): Bovernick, Rodney B.
• Assistant Examiner(s): Phan, James
• Application Number:
  US07/911,192
• Time in Patent Office: 362 Days
• Field of Search: 359/198-199, 359/201-202, 359/212-217, 359/223-224, 359/368, 359/221, 250/234-236
• US Class Current: 359/199.1
• CPC Class Codes: G02B 21/002 Scanning microscopes scanning near field optical microscopes G01Q60/18
• CPC Class Codes: G02B 26/101 with both horizontal and vertical deflecting means, e.g. raster or XY scanners colour television using laser beams scanning a display screen H04N9/3129

Abstract

A confocal microscope (10) includes a scanner assembly (38) in which the x-axis deflector assembly includes two resonant scanners (50 and 52) that oscillate about parallel axes at different frequencies, one of which is a harmonic of the other. As a consequence, the x-axis scan can be nearly linear even though it is provided resonantly and thus benefits from the high-speed capabilities of resonant systems. A galvanometer (64) pivots the housing of one of the resonant scanners (50) about its axis so as to provide x-axis panning.

Claims

1. An optical instrument comprising:

A) at least one of a light source and a light detector,

B) means defining a light path between a target spot in an object region and the source or detector, and

C) a scanner assembly disposed in the light path and including;

i) at least one deflector assembly associated with a deflection axis and resonant at both a first, fundamental resonant frequency and an additional, harmonic resonant frequency, which is a harmonic of the fundamental resonant frequency, and

ii) a drive mechanism for varying the position of the target spot in directions generally parallel to the associated deflection axis by simultaneously both driving the deflector assembly nonresonantly and driving it resonantly at the fundamental and harmonic resonant frequencies, the drive mechanism including a control system for maintaining a predetermined phase relationship between the target spot'"'"'s motion components at the two resonant frequencies.

2. The optical instrument as defined in claim 1 wherein the scanner assembly includes:

A) a pivotably mounted resonant scanner whose mirror is positioned to reflect light traveling in the light path; and

B) a motor for non-resonantly pivoting the resonant scanner.

3. The optical instrument as defined in claim 2 wherein the deflector assembly includes a resilient motion reducer that couples the motor to the resonant scanner.

4. The optical instrument as defined in claim 3 wherein the resonant scanner is a reactionless scanner.

5. The optical instrument as defined in claim 2 wherein the resonant scanner is a reactionless scanner.

6. The optical instrument as defined in claim 2 wherein:

A) the deflector assembly includes a second resonant scanner separate from the first-mentioned resonant scanner, the resonant frequency of the first resonant scanner being one of the fundamental and harmonic resonant frequencies, the resonant frequency of the second resonant scanner being the other of the fundamental and harmonic resonant frequencies; and

B) the drive mechanism includes separate first and second drivers for driving the first and second resonant scanners, respectively, substantially at their resonant frequencies, and a third driver for driving the motor nonresonantly.

7. The optical instrument as defined in claim 1 wherein:

A) the deflector assembly includes both a resonant scanner and a nonresonant scanner, both of whose separate respective mirrors vary the position of the target spot in directions substantially parallel to the deflection axis; and

B) the drive mechanism respectively drives the resonant and non-resonant scanners resonantly and non-resonantly.

8. The optical instrument as defined in claim 1 further including a microscope objective lens disposed in the light path and focused on the object region.

9. The optical instrument as defined in claim 8 wherein:

A) the optical instrument includes both a light source and a light detector;

B) the means defining the light path defines source and detector light paths between the target spot and the source and detector, respectively, such that the source and detector light paths have a common path segment; and

C) the scanner assembly and objective are disposed in the common path segment.

10. A confocal microscope comprising:

A) a light source,

B) a light detector,

C) a microscope objective lens for viewing an object region,

D) means defining source and detector light paths between a target spot in the object region and the source and detector, respectively, such that the source and detector light paths have a common path segment, and

E) a scanner assembly disposed in the common path segment and including;

i) at least one deflector assembly associated with a deflection axis and resonant at both a first, fundamental resonant frequency and an additional, harmonic resonant frequency, which is a harmonic of the fundamental resonant frequency, and

ii) a drive mechanism for driving the deflector assembly to vary the position of the target spot in directions generally parallel to the associated axis at the fundamental and harmonic resonant frequencies simultaneously, the drive mechanism including a control system for maintaining a predetermined phase relationship between the target spot'"'"'s motion components at the two resonant frequencies.

11. The confocal microscope as defined in claim 10 wherein:

A) the deflector assembly includes a first scanner, whose resonant frequency is the fundamental resonant frequency, and a second scanner, whose resonant frequency is the harmonic resonant frequency; and

B) the drive mechanism includes first and second drivers for driving the first and second scanners, respectively, substantially at their resonant frequencies.

12. A confocal microscope as defined in claim 11 wherein the control system includes:

A) a phase comparator for comparing the phases of the components of the deflector assembly'"'"'s motion at the two resonant frequencies; and

B) a resonant-frequency controller responsive to the phase comparator for so controlling one of the resonant frequencies as to maintain a predetermined phase relationship between the two resonant-frequency components.

13. The confocal microscope as defined in claim 12 wherein the resonant-frequency controller includes a heating element for heating the deflector assembly and adjusts said one of the resonant frequencies by using the heating element to heat the deflector assembly.

14. The confocal microscope as defined in claim 12 wherein the resonant-frequency controller includes a magnetic spring acting in the deflector assembly and adjusts said one of the resonant frequencies by varying the current that flows through the magnetic spring.

15. A confocal microscope as defined in claim 10 wherein the control system includes:

A) a phase detector for generating an output representative of the phase difference between the components of the deflector assembly'"'"'s motion at the two resonant frequencies; and

B) a resonant-frequency controller responsive to the phase detector for so controlling one of the resonant frequencies as to maintain a predetermined phase relationship between the two resonant-frequency components.

16. The confocal microscope as defined in claim 15 wherein the drive mechanism is responsive to at least one resonant-frequency component of the deflector assembly'"'"'s motion to cause the drive mechanism and deflector assembly to self-oscillate at that frequency.

17. The confocal microscope as defined in claim 15 wherein the resonant-frequency controller includes a heating element for heating the deflector assembly and adjusts said one resonant frequency by using the heating element to heat the deflector assembly.

18. The confocal microscope as defined in claim 17 wherein the drive mechanism is responsive to at least one resonant-frequency component of the deflector assembly'"'"'s motion to cause the drive mechanism and deflector assembly to self-oscillate at that frequency.

19. The microscope as defined in claim 10 wherein the scanner assembly further includes a second deflector assembly for varying the target-spot position in directions generally parallel to a second deflection axis substantially orthogonal to the first-mentioned deflection axis.