MINIATURIZED OPTICAL HEAD WITH HIGH SPATIAL RESOLUTION AND HIGH SENSITIVITY, ESPECIALLY FOR FIBRED CONFOCAL FLUORESCENCE IMAGING

• US 20100296178A1
• Filed: 04/27/2007
• Published: 11/25/2010
• Est. Priority Date: 05/05/2006
• Status: Active Grant

• Current Assignee: Mauna Kea Technologies
• Original Assignee: Mauna Kea Technologies
• Inventors: Lavillonniere, Nicolas, Mathieu, Gilles, Viellerobe, Bertrand, Boularot, Nicolas, Doussoux, Francois, Genet, Magalie
• Granted Patent: US 8,300,326 B2
• Time in Patent Office: Days
• US Class Current: 359/754
• CPC Class Codes: A61B 1/00188 with focusing or zooming features
• CPC Class Codes: G02B 21/0028 specially adapted for specific applications, e.g. for endoscopes, ophthalmoscopes, attachments to conventional microscopes
• CPC Class Codes: G02B 21/0072 details concerning resolution or correction, including general design of CSOM objectives
• CPC Class Codes: G02B 23/243 Objectives for endoscopes
• CPC Class Codes: G02B 27/0025 for optical correction, e.g. distorsion, aberration

Abstract

A miniaturized optical head provided to equip the distal end of a beam of flexible optical fibres scanned by a laser beam, is designed to come in contact with a sample and to excite the sample confocally. This optical head includes elements for correcting spherical aberrations and focusing members. The focusing members include: at least a first lens (L4) of high convergence associated with a spherical or hemispherical lens (L5) arranged at the distal end of the optical head, and elements for correcting the axial and lateral chromatic aberration provided with a single divergent lens (3b) whose curvature is substantially centered on the pupil of the optical fibre beam and arranged at the exact distance for this pupil for which the conditions of lateral achromatization coincide with the conditions of axial achromatization; this divergent lens being associated with a second convergent lens (L3a) in the form of a doublet (L3).

Claims

1. Miniaturized optical head provided to equip the distal end of a bundle of flexible optical fibres scanned by a laser beam, said optical head being intended to come into contact with a sample and excite said sample in a confocal manner;

this optical head comprising means for correcting spherical aberrations and focusing means;

characterized in that the focusing means comprise;

at least a first strongly convergent lens (L4) combined with a spherical or hemispherical lens (L5) arranged at the distal end of the optical head, and

means for correcting axial and lateral chromatism that are provided with a single divergent lens (3b) the curvature of which is substantially centered on the pupil of the bundle of optical fibres and arranged at the correct distance from this pupil for which the lateral achromatization conditions coincide with the axial achromatization conditions;

this divergent lens being combined with a second convergent lens (L3a) in the form of a doublet (L3).

2. Optical head according to claim 1, characterized in that the means for correcting spherical aberrations comprise a third convergent lens (L2);

the thicknesses of the first (L4) and third (L2) convergent lenses being determined so as to correct the cumulative spherical aberration on the convergent diopters.

3. Optical head according to claim 2, characterized in that the thickness of the third convergent lens (L2) is also determined so as to image the pupil on the second convergent lens (L3).

4. Optical head according to claim 1, characterized in that the means for correcting spherical aberrations comprise a third convergent lens (L2);

the thickness, the radius of curvature and the nature of this third lens (L2) are adapted so as to image the pupil in a plane situated as close as possible to said bundle of optical fibres.

5. Optical head according to claim 2, characterized in that the glass of the third lens (L2) is determined with a small enough constringence to minimize the necessary chromatic correction power, and with a large enough refractive index to limit the spherical and coma aberration effect.

6. Optical head according to claim 1, characterized in that said doublet (L3) is placed in a pupillary plane.

7. Optical head according to claim 1, characterized in that said doublet (L3) comprises a pair of glasses with a small index difference but a large chromatic dispersion difference so as to compensate for the chromatic aberrations of the convergent lenses.

8. Optical head according to claim 1, characterized in that the divergent lens is curved so as to obtain a numerical aperture greater than 0.8.

9. Optical head according to claim 2, characterized in that the first (L4) and third (L2) convergent lenses are each obtained from a lens having a small radius and a large radius, said large radius being made plane so as to obtain a plano-convex lens.

10. Optical head according to claim 1, characterized in that the first convergent lens (L4) is designed and arranged so as to eliminate the image of the pupil sufficiently far ahead to minimize the astigmatism generated by the spherical or hemispherical lens (L5) in the imaged field.

11. Optical head according to claim 1, characterized in that the hemispherical lens (L5) is produced in a ball, the plane output face of which is obtained by abrasion on a plane polisher.

12. Optical head according to claim 1, characterized in that the thickness of the hemispherical lens (L5) is adjusted in order to obtain a predetermined frontal area of the optical head.

13. Optical head according to claim 12, characterized in that the axial position of the hemispherical lens (L5) is determined according to the thickness of said hemispherical lens (L5) in order to optimize the optical performances of the optical head for said frontal area.

14. Optical head according to claim 1, characterized in that it also comprises a plate (L1) with plane faces for eliminating the stray reflection occurring at the output of the bundle of optical fibres.

15. Optical head according to claim 1, characterized in that the signal collected by the optical head that originates from the sample is a fluorescence signal.

16. Optical head according to claim 1, characterized in that the signal collected by the optical head that originates from the sample is a reflectance signal.

17. Optical head according to claim 1, characterized in that the bundle of optical fibres is scanned by the laser beam in real time so as to acquire at least twelve images per second.