Distance measuring confocal microscope

• US 5,785,651 A
• Filed: 06/07/1995
• Issued: 07/28/1998
• Est. Priority Date: 06/07/1995
• Status: Expired due to Fees

• Current Assignee: Addition Technology, Inc. (AJL Ophthalmic SA)
• Original Assignee: KeraVision, Inc.
• Inventors: Kuhn, William P., Baker, Phillip C.
• Primary Examiner(s): Kamm, William E.
• Assistant Examiner(s): LAYNO, CARL HERNANDZ
• Application Number:
  US08/484,204
• Time in Patent Office: 1,147 Days
• Field of Search: 128/645, 128/665, 128/745, 606/4, 606/10, 606/11, 250/339.01, 250/339.06, 250/339.07, 33/511, 33/512, 33/274 R, 356/381, 356/382, 600/310, 600/318, 600/398, 600/558
• US Class Current: 600/310
• CPC Class Codes: G01B 11/026 by measuring distance between sensor and object G01B11/0608 takes precedence
• CPC Class Codes: G01B 11/255 for measuring radius of curvature measuring diameter G01B11/08
• CPC Class Codes: G01B 2210/50 Using chromatic effects to achieve wavelength-dependent depth resolution

Abstract

A novel apparatus and method for the quick and accurate determination of surface profile and depth reading within little or no mechanical motion is presented comprising a polychromatic light source; a means for focusing the light onto a point of sample target, said means having a known amount of longitudinal chromatic aberration; and a means for detecting the wavelengths of light reflected from the sample target. The light projected onto the sample target is focused according to wavelength due to the longitudinal chromatic aberration. While light from across the spectrum will be reflected, the light returning from the sample target will be most strongly reflected in a wavelength that is focused on a reflective point in the sample. The means for detecting the light in the present invention passes through a substantially pinhole aperture before the light is detected according to wavelength. The purpose of the pinhole aperture is resolution. The pinhole aperture ensures that those wavelengths that focus onto the pinhole are more strongly detected than wavelengths that do not focus on the aperture. Thus, the resolution of wavelength intensity peaks is greatly increased.

Claims

1. A method for scanning a distance measuring confocal microscope to produce a profile of an object, the steps of said method comprising:

(A) moving the confocal microscope over a known position such that an imaging beam of polychromatic light is approximately normal to the surface of the object at the known position;

(B) imaging the known position on the object with the confocal microscope and correlating the image data with the position data;

(C) repeating steps A and B for a new known position until a suitable profile of the object is complete.

2. The method as recited in claim 1 wherein the step of moving the confocal microscope further includes:

moving the confocal microscope along a radial path across the object.

3. The method as recited in claim 2 wherein the step of moving the confocal microscope further includes choosing a new radial path for the confocal microscope to follow.

4. The method as recited in claim 1 wherein the step of imaging and correlating the image data with position data further includes:

recognizing and transmitting position data concurrently with image data for correlating.

5. An apparatus for measuring the distance of a set of points on an object from said apparatus, said apparatus comprising:

polychromatic light source;

means for focusing light from said source onto said set of points, said means comprising a known amount of longitudinal chromatic aberration such that different wavelengths emitted from said polychromatic light source have different focal lengths in said object, wherein said means for focusing light comprises a substantially achromatic collimator lens; and

a Fresnel zone plate of known chromatic aberration, said collimator lens providing collimated polychromatic light from said source as input into said zone plate;

means for filtering the spectrum of light reflected from said set of points; and

means for measuring the spectrum of the light reflected from said object.

6. The apparatus as recited in claim 5 wherein the means for focusing further comprises a first fiber optic cable and the means for filtering further comprises a second fiber optic cable.

7. The apparatus as recited in claim 5 wherein said means for focusing light from said source comprises a singlet lens having a known amount of longitudinal chromatic aberration.

8. The apparatus as recited in claim 5 wherein said means for focusing light from said source comprises the use of doublet lens having a known amount of longitudinal chromatic aberration.

9. A method for determining the depth of a first object embedded in a substantially transparent second object, said substantially transparent second object having a substantially reflective surface, the steps of said method comprising:

(A) focusing light from a polychromatic light source onto said substantially transparent second object such that each wavelength of light has a distinct focal point;

(B) filtering the light reflected from said substantially reflective surface, yielding a first reflected wavelength, and from said first object embedded in said substantially transparent second object, yielding a second reflected wavelength;

(C) measuring the spectrum of the light filtered in step (B);

(D) correlating throughput intensity peaks from said first reflected wavelength and said second reflected wavelength measured in step (C) to determine the depth of said first object embedded in said substantially transparent second object.

10. The method as recited in claim 9 wherein said first object comprises a ring adapted to be placed inside a cornea.

11. The method as recited in claim 9 wherein said first reflected wavelength is reflected from the back surface of the cornea and said second reflective wavelength is reflected from the front surface of the cornea.

12. An apparatus for measuring the distance of a set of points on an object from said apparatus, said apparatus comprising:

polychromatic light source;

means for focusing light from said source onto said set of points, said means comprising a known amount of longitudinal chromatic aberration such that different wavelengths emitted from said polychromatic light source have different focal lengths in said object, wherein said means for focusing light further comprises a first fiber optic cable;

means for filtering the spectrum of light reflected from said set of points wherein said means for filtering further comprises a second fiber optic cable; and

means for measuring the spectrum of the light reflected from said object; and

a collimator lens wherein said first fiber optic cable and said second fiber optic cable are positioned slightly off-axis from said collimator lens.