Apparatus and method for measuring spectrum image data of eyeground

• US 20070002276A1
• Filed: 12/02/2005
• Published: 01/04/2007
• Est. Priority Date: 12/03/2004
• Status: Active Grant

• Current Assignee: Topcon Corporation
• Original Assignee: Topcon Corporation
• Inventors: Aoki, Hiroyuki, Hirohara, Yoko, Tsuruga, Yasuko, Mihashi, Toshifumi, Yamaguchi, Tatsuo
• Granted Patent: US 7,850,305 B2
• Time in Patent Office: Days
• US Class Current: 351/206
• CPC Class Codes: A61B 3/0025 characterised by electronic signal processing, e.g. eye models
• CPC Class Codes: A61B 3/152 for aligning
• CPC Class Codes: A61B 5/14555 specially adapted for the eye fundus

Abstract

The object of the invention is to provide a favorable spectral characteristic that reduces variation depending on the frequency of received light intensity, and that is gentle on a subject eye. It also eliminates displacement between positions of respective spectral images of the same part even if a change in alignment occurs between the eye and apparatus with the lapse of time. An apparatus 1 for measuring spectral fundus image data of this invention comprises: an illumination optical system 10 having an illumination light source 11 that emits a light beam in a specified wavelength range; a light receiving optical system 20 for forming a fundus image on the light receiving surface of a photographing section 4; a liquid crystal wavelength tunable filter 32 capable of choosing a wavelength of a transmitted light beam in a specified wavelength range; a spectral characteristic correction filter 13 having wavelength characteristic for correcting the wavelength characteristic of the emitted light intensity of the illumination light source 11 and the transmission wavelength characteristic of the wavelength tunable filter 32 so that the received light intensity on the light receiving surface is kept within the specified range; and a data measuring section 7 for taking the spectral fundus image data from the light receiving surface while changing the wavelength of the light beam passing through the wavelength tunable filter 32.

Claims

1. An apparatus for measuring spectral fundus image data, comprising:

an illumination optical system having an illumination light source that emits a light beam in a specified wavelength range, for illuminating a fundus of a subject eye with the light beam from the illumination light source;

a light receiving optical system for receiving the light beam reflected from the illuminated fundus and for forming a fundus image on the light receiving surface of a photographing section;

a wavelength tunable filter disposed in either the illumination optical system or the light receiving optical system and capable of choosing a wavelength of a transmitted light beam in the specified wavelength range;

a spectral characteristic correcting filter disposed in either the illumination optical system or the light receiving optical system and having a wavelength characteristic for correcting the wavelength characteristic of the emitted light intensity of the illumination light source and the transmission wavelength characteristic of the wavelength tunable filter to keep the received light intensity on the light receiving surface within a specified range; and

a data measuring section for taking spectral fundus image data based on signals from the light receiving surface when the wavelength of the transmitted light beam of the wavelength tunable filter is changed.

2. The apparatus for measuring spectral fundus image data as recited in claim 1, wherein the wavelength tunable filter is disposed in the light receiving optical system and the spectral characteristic correcting filter is disposed in the illumination optical system.

3. The apparatus for measuring spectral fundus image data as recited in claim 1, wherein the wavelength tunable filter is a liquid crystal wavelength tunable filter and the spectral characteristic correcting filter is constituted that its transmission rate in a specified wavelength range is higher on the shorter wavelength side than on the longer wavelength side.

4. The apparatus for measuring spectral fundus image data as recited in claim 1, wherein the specified wavelength range is 540 to 610 nm.

5. The apparatus for measuring spectral fundus image data as recited in claim 1, wherein the light receiving surface is made of a CCD and the specified range of the received light intensity is within a dynamic range of the CCD.

6. The apparatus for measuring spectral fundus image data as recited in claim 1, further comprising an exposure control section constituted to determine automatically the exposure time according to the received light signal level on the light receiving surface.

7. An apparatus for measuring spectral fundus image data, comprising:

an illumination optical system for illuminating a fundus of a subject eye;

a light receiving optical system for receiving a light beam reflected from the illuminated fundus and for forming a fundus image on a light receiving surface of a photographing section; and

a data measuring section for comparing with each other a plurality of spectral fundus image original data taken at different time points based on signals from the light receiving surface to correct positions of the images, and for producing a series of fundus image data with their positions corrected.

8. The apparatus for measuring spectral fundus image data as recited in claim 7:

wherein the correction of positions of the images is performed as position matching between a plurality of the spectral fundus image original data using correlation processing and affine transformation or Hermert transformation while choosing characteristic points.

9. The apparatus for measuring spectral fundus image data as recited in claim 7, wherein

the illumination optical system includes an illumination light source that emits a light beam in a specified wavelength range;

further comprising a wavelength tunable filter disposed in either the illumination optical system or the light receiving optical system and capable of choosing a wavelength of a transmitted light beam in the specified wavelength range;

wherein the data measuring section takes a plurality of the fundus image original data by changing a wavelength of the light beam transmitted through the wavelength tunable filter.

10. The apparatus for measuring spectral fundus image data as recited in claim 9, further comprising a spectral characteristic correcting filter disposed in either the illumination optical system or the light receiving optical system and having a wavelength characteristic for correcting the wavelength characteristic of emitted light intensity of the illumination light source and the transmission wavelength characteristic of the wavelength tunable filter to keep the received light intensity on the light receiving surface within a specified range.

11. The apparatus for measuring spectral fundus image data as recited in claim 9, wherein the amount of change in the wavelength chosen at the wavelength tunable filter can be set to be equal to or smaller than a threshold value;

and the data measuring section corrects the positions of the images while comparing with each other the fundus images original data different in wavelength by the amount of change equal to or smaller than the threshold value.

12. The apparatus for measuring spectral fundus image data as recited in claim 11, wherein the specified wavelength range is 540 to 610 nm, and the amount of change equal to or smaller than the threshold value is 10 nm.

13. The apparatus for measuring spectral fundus image data as recited in claim 9, wherein the wavelength tunable filter is a liquid crystal wavelength tunable filter.

14. The apparatus for measuring spectral fundus image data as recited in claim 8, wherein the data measuring section chooses, as the characteristic point, a blood vessel part on the shorter wavelength side and the choroid blood vessel part on the longer wavelength side to correct positions of the images.

15. The apparatus for measuring spectral fundus image data as recited in claim 9, wherein the data measuring section is capable of calculating the received light intensity and optical density (referred to as OD within the following claims) of artery and vein.

16. The apparatus for measuring spectral fundus image data as recited in claim 15, wherein the data measuring section makes corrections according to a diameter of a blood vessel of a part where intensities at the artery and vein are calculated, calculates ODs in respective positions on the retina, analyzes factors of ODs in respective positions based on spectral distribution of ODs of the artery and vein, calculates rates of oxygenated hemoglobin in respective positions, and makes the oxygenated hemoglobin rates into a map.

17. A method for measuring spectral fundus image data, comprising the steps of:

illuminating a fundus of a subject eye of an animal with a light beam in a specified wavelength range;

receiving a reflected light beam from the fundus and forming an animal fundus image;

changing a wavelength of the light beam in the specified wavelength range to take spectral fundus image data; and

comparing with each other spectral fundus image original data different in wavelength by an amount of change smaller than a threshold value, and producing a series of spectral fundus image data in the specified wavelength range.

18. The method for measuring spectral fundus image data as recited in claim 17, wherein, when positions of the images are corrected;

an original data the second shortest in wavelength with respect to a reference image the shortest in wavelength, out of the spectral fundus image original data, is used as a pre-correction image, the position of which is corrected;

next, using the position-corrected pre-correction image as a new reference image, another original data the third shortest in wavelength is used as another pre-correction image, the position of which is corrected;

followed by successive correction of positions from shorter wavelength side to longer wavelength side,

or, an original data the second longest in wavelength with respect to a reference image the longest in wavelength, out of the spectral fundus images original data, is used as a pre-correction image, the position of which is corrected;

next, using the position-corrected pre-correction image as a new reference image, another original data the third longest in wavelength is used as another pre-correction image, the position of which is corrected;

followed by successive correction of positions from longer wavelength side to shorter wavelength side.

19. The method for measuring spectral fundus image data as recited in claim 17, wherein the spectral fundus image original data images are taken in the specified wavelength range of 540 to 610 nm and with the amount of change in wavelength being set to 10 nm;

the step of correcting the image positions having the steps of, choosing characteristic points of spectral fundus image original data different in wavelength from each other by an amount corresponding to a change less than a threshold value to match their positions by carrying out correlation processing and affine transformation or Hermert transformation,

choosing artery and vein as characteristic points to calculate received light intensities and ODs of the artery and vein,

calculating ODs in respective positions on the retina by corrections according to the blood vessel diameters in parts where the intensities at the artery and vein are calculated,

calculating the rates of oxygenated hemoglobin in respective positions on the retina by analyzing factors of ODs in respective positions on the retina on the basis of spectral distribution of ODs of the artery and vein, and

making the rates of oxygenated hemoglobin of the spectral fundus images into a map.