Method and apparatus for providing high contrast imaging

• US 6,438,396 B1
• Filed: 09/22/1999
• Issued: 08/20/2002
• Est. Priority Date: 11/05/1998
• Status: Expired due to Term

• Current Assignee: Intellectual Property MVM B.V.
• Original Assignee: Cytometrics, Inc.
• Inventors: Meyers, Mark M., Cook, Christopher A.
• Primary Examiner(s): Winakur, Eric F.
• Assistant Examiner(s): KREMER, MATTHEW J
• Application Number:
  US09/401,859
• Time in Patent Office: 1,063 Days
• Field of Search: 600/310, 600/322, 600/365, 600/473, 600/250, 600/330, 600/162, 600/476, 356/39-42, 356/364, 356/369, 382/128, 382/130, 382/134, 382/274
• US Class Current: 600/310
• CPC Class Codes: A61B 5/0059 using light, e.g. diagnosis by transillumination, diascopy, fluorescence A61B5/0093, A61B5/1455, A61B5/02416 and A61B5/0261 take precedence
• CPC Class Codes: A61B 5/14535 for measuring haematocrit
• CPC Class Codes: G01N 15/0211 Investigating a scatter or diffraction pattern

Abstract

An in vivo imaging device having an illumination system that creates a virtual source within a tissue region of a subject in a non-invasive manner. The illumination system transforms a maximum amount of illumination energy from a light source into a high contrast illumination pattern. The illumination pattern is projected onto the object plane in a manner that maximizes the depth to which clear images of sub-surface features can be obtained. The high intensity portion of the illumination pattern is directed onto the object plane outside the field of view of an image capturing device that detects the image. In this configuration, scattered light from within the tissue region interacts with the object being imaged. This illumination technique provides for a high contrast image of sub-surface phenomena such as vein structure, blood flow within veins, gland structure, etc.

Claims

1. An apparatus for detecting optical characteristics of a sub-surface object located at an object plane, comprising:

a light source for providing an illumination beam that propagates along an illumination path defined by said light source and the object;

an illumination system that transforms said illumination beam into a high contrast illumination pattern having a high intensity region and a low intensity region and projects said illumination pattern onto the sub-surface object substantially outside a desired portion of the sub-surface object to be imaged; and

an imaging system that includes an image capturing device for detecting an image of the desired portion of the sub-surface object, said image being formed by scattered illumination from said high contrast illumination pattern that is transmitted through the sub-surface object and propagates along an image path to said image capturing device, said image path defined by the object and said image capturing device,

wherein said illumination system projects said high intensity region outside a field of view of said image capturing device at the object plane and said illumination system projects said low intensity region within the field of view of said image capturing device.

2. The apparatus of claim 1, further comprising:

a condenser disposed between said light source and said object plane to collimate said illumination beam, said collimated illumination beam propagating to said illumination system.

3. The apparatus of claim 1, said illumination system comprising:

a folding mirror disposed between said light source and the object plane, said folding mirror including a surface having a substantially reflective outer portion and a substantially transmissive inner portion, wherein said folding mirror transforms said illumination beam into said high contrast illumination pattern and directs said high contrast illumination pattern onto the object plane, and wherein said image is substantially transmitted through said inner portion along said image path towards said image capturing device.

4. The apparatus of claim 1, further comprising:

an objective disposed between the object plane and said image capturing device along said image path, said objective further directing said high contrast illumination pattern onto the object plane and said objective magnifying said image onto said image capturing device.

5. The apparatus of claim 4, wherein said illumination system comprises:

an illumination pattern generator disposed between said light source and the object plane to transform said illumination beam into said high contrast illumination pattern;

a projection lens disposed between said illumination pattern generator and the object plane that projects said high contrast illumination pattern onto the object plane; and

a folding mirror, disposed between said light source and the object plane and disposed between the object plane and the image capturing device, to direct said projected high contrast illumination pattern along said image path onto the object plane.

6. The apparatus of claim 5, wherein said illumination pattern generator comprises:

an obscuration disposed between said light source and said optical elements, said obscuration blocking a first portion of said illumination beam, said first portion corresponding to said low intensity region of said illumination pattern, and wherein a second portion of said illumination beam corresponds to said high intensity portion of said illumination pattern.

7. The apparatus of claim 6, wherein said obscuration is disposed along said illumination path substantially in the plane of a first aperture, wherein an outer diameter of said obscuration corresponds to said field of view of said image capturing device, and wherein said projection lens and said objective images said obscuration onto the object plane.

8. The apparatus of claim 5, wherein said illumination pattern generator comprises:

a conical lens disposed between said light source and said projection lens, said conical lens redistributing said illumination beam into an annular pattern, said annular pattern projected onto the object plane by said projection lens, wherein said annular pattern has a low intensity central region.

9. The apparatus of claim 8, wherein said conical lens is an axicon.

10. The apparatus of claim 5, wherein said illumination pattern generator comprises:

a conical grating disposed between said light source and said projection lens, said conical grating redistributing said illumination beam into an annular pattern, said annular pattern projected onto the object plane by said projection lens, wherein said annular pattern has a low intensity central region.

11. The apparatus of claim 5, wherein said illumination pattern generator comprises:

an optical element disposed between said light source and said projection lens, said optical element having a hologram coated onto a surface of said optical element for redistributing said illumination beam into an annular pattern, said annular pattern projected onto the object plane by said projection lens, wherein said annular pattern has a low intensity central region.

12. The apparatus of claim 5, further comprising:

a first polarizer disposed between said light source and said folding mirror for polarizing said illumination beam from said light source;

a second polarizer disposed along said image path between the folding mirror and said image capturing device, wherein a plane of polarization of said second polarizer is 90 degrees relative to a plane of polarization of said first polarizer.

13. A spectral imaging apparatus for non-invasive, in vivo analysis of a subject'"'"'s tissue and blood, comprising:

a light source for illuminating a region of interest, wherein a light path is formed between said light source and said region of interest;

means for transforming light emanating from said light source into a illuminating pattern having a low intensity region and a high intensity region;

means for projecting said low intensity region of said illumination pattern onto an object within said region of interest and beneath a surface of said region of interest and for projecting said high intensity region of said illumination pattern onto the object substantially outside said region of interest; and

image capturing means for capturing an image of said region of interest formed by scattered illumination from said high intensity illumination pattern that is transmitted through the object and said region of interest and propagates along an image path, formed between the object and said image capturing means, to said image capturing device.

14. The apparatus of claim 13, wherein said means for projecting directs said high intensity region of said illumination pattern to a portion of said region of interest outside a field of view of said image capturing means.

15. The apparatus of claim 14, wherein upon said illumination pattern reaching said surface, light from said high intensity region of said illumination pattern interacts with matter within said region of interest and is scattered by one or more scattering events, thereby forming a sub-surface illumination source to illuminate said object.

16. The apparatus of claim 15, wherein said image is formed by a substantial portion of said sub-surface illumination source being transmitted through said object along said image path.

17. A method for creating a source of illumination in a sub-surface tissue region that contains an object of interest, wherein the object is illuminated from all directions about an object plane wherein the object is located, wherein an image of said object is detected by an image capturing device, comprising the steps of:

(a) providing a light source;

(b) transforming light from said light source into an illumination pattern having a high intensity portion and a low intensity portion;

(c) directing said illumination pattern onto a surface of the tissue region such that said high intensity portion of said illumination pattern is incident upon said object plane outside a field of view of the image capturing device and said low intensity portion is incident upon said object plane within the field of view of the image capturing device; and

(d) detecting scattered light that interacts with the object with the image capturing device, wherein said high intensity portion of said illumination pattern undergoes one or more scattering events in the sub-surface tissue region.

18. The method of claim 17, further comprising the step of:

(e) performing a transmission measurement of said sub-surface tissue region.

19. The method of claim 17, wherein step (b) further comprises:

blocking a portion of said light from said source, said blocked portion corresponding to said low intensity portion of said illumination pattern.

20. The method of claim 17, wherein step (b) further comprises:

providing a folding mirror having a first surface, said first surface having a substantially reflective outer portion and a substantially transmissive inner portion, wherein light reflected off said substantially reflective outer portion corresponds to said high intensity portion of said illumination pattern.

21. The method of claim 17, wherein step (b) further comprises:

providing an optical element to redistribute said light into an annular pattern which corresponds to said illumination pattern.

22. An apparatus for optically penetrating an object and detecting subsurface optical characteristics of an object, comprising:

a light source for illuminating the object at a wavelength such that the multiple scattering depth is small compared to the penetration depth of the illuminating light;

a first polarizer for polarizing light from said light source;

means for transforming said illuminating light source into a high contrast illumination pattern which is projected onto the object substantially outside and surrounding a desired portion of the object to be imaged;

imaging means for detecting an image emanating from beneath the surface of the desired portion of the illuminated object, said image being formed by scattered illumination from said high contrast illumination pattern that is transmitted through the subsurface of the object and propagates along an image path to said imaging means; and

a second polarizer disposed in said image path between the object and said imaging means through which the scattered light passes, wherein a plane of polarization of said second polarize is substantially orthogonal relative to a plane of polarization of said first polarizer.

23. An apparatus for quantitatively measuring absorption properties of an imaged object, comprising:

a light source for illuminating an object to be imaged;

a first polarizer for polarizing light from said light source;

an illumination system for transforming said illuminating light source into a high contrast illumination pattern which is projected onto the object substantially outside and surrounding a desired portion of the object to be imaged;

imaging means for detecting an image emanating from beneath a surface of the desired portion of the illuminated object, said image being formed by scattered illumination from said high contrast illumination pattern that is transmitted through the subsurface of the object and propagates along an image path to said imaging means;

a second polarizer disposed in said image path, wherein a plane of polarization of said second polarizer is substantially orthogonal relative to a plane of polarization of said first polarizer; and

measuring means coupled to said imaging means for quantitatively measuring differences in absorption properties between imaged structures using said image.