OPTICAL IMAGE MEASURING DEVICE AND CONTROL METHOD THEREOF

• US 20110267583A1
• Filed: 12/07/2009
• Published: 11/03/2011
• Est. Priority Date: 01/06/2009
• Status: Active Grant

• Current Assignee: Kabushiki Kaisha Topcon
• Original Assignee: Kabushiki Kaisha Topcon
• Inventors: Hayashi, Takefumi
• Granted Patent: US 8,646,913 B2
• Time in Patent Office: Days
• US Class Current: 351/206
• CPC Class Codes: A61B 3/102 for optical coherence tomography [OCT]
• CPC Class Codes: A61B 3/117 for examining the anterior chamber or the anterior chamber angle, e.g. gonioscopes
• CPC Class Codes: A61B 3/12 for looking at the eye fundus, e.g. ophthalmoscopes A61B3/13 takes precedence
• CPC Class Codes: A61B 3/14 Arrangements specially adapted for eye photography apparatus or arrangements for taking photographs per se G03B
• CPC Class Codes: G01B 9/02028 Two or more reference or object arms in one interferometer
• CPC Class Codes: G01B 9/02029 Combination with non-interferometric systems, i.e. for measuring the object
• CPC Class Codes: G01B 9/02044 Imaging in the frequency domain, e.g. by using a spectrometer
• CPC Class Codes: G01B 9/02063 by particular alignment of focus position, e.g. dynamic focussing in optical coherence tomography
• CPC Class Codes: G01B 9/02091 Tomographic interferometers, e.g. based on optical coherence

Abstract

A low-coherence light is split into a signal light and a reference light. The optical path length of the reference light is switched to optical path lengths that correspond to a first depth zone and a second depth zone. When forming a tomographic image of the second depth zone, in an optical system that condenses the signal light to the first depth zone when a measured object and an objective lens are located at a predetermined working distance, while being positioned at the working distance, a depth zone switching lens that transitions the depth at which the signal light is condensed to the second depth zone is inserted.

Claims

1. An optical image measuring device that forms tomographic images of at least a first depth zone and a second depth zone of a measured object, respectively, comprising:

a splitting part configured to split a low-coherence light into a signal light and a reference light;

a switching part configured to switch an optical path length of said reference light to optical path lengths that correspond to at least said first depth zone and said second depth zone;

an optical system comprising an objective lens and a focusing lens, and configured to condense said signal light into said first depth zone;

a depth zone switching lens configured to be placed in a way that allows it to be inserted into and removed from said optical system, and condense said signal light into said second depth zone when it inserted into said optical system with said measured object and said objective lens positioned at a predetermined working distance;

a control part configured to insert said depth zone switching lens into said optical system when the optical path length is switched to the optical path length that corresponds to said second depth zone by said switching part;

an interference light generation part configured to generate an interference light by causing interference with said signal light via said optical system after being reflected from said measured object and said reference light via a light path of the optical path length that has been switched by said switching part;

a detecting part configured to detect each of said interference lights in accordance with the control by said control part; and

an image forming part configured to form tomographic images of said first depth zone and said second depth zone, respectively, based on the detection by said detecting part.

2. The optical image measuring device according to claim 1, wherein:

said measured object is a living eye;

said switching part is configured to switch to optical path lengths that correspond to a fundus oculi as said first depth zone and an anterior segment as said second depth zone;

said focusing lens is configured to be changed in the placement position depending on the diopter of said living eye when the optical path length is switched to the optical path length that corresponds to said first depth zone by said switching part; and

said control part is configured to change the placement position of said focusing lens to a predetermined position when the light path of said reference light is switched by said switching part to the optical path length that corresponds to said second depth zone.

3. The optical image measuring device according to claim 1, wherein:

said measured object is the living eye;

said switching part is configured to switch to optical path lengths that correspond to a fundus oculi as said first depth zone and an anterior segment as said second depth zone;

said optical system is configured to condense said signal light into said fundus oculi;

said depth zone switching lens is configured to condense said signal light into said anterior segment when it is inserted into said optical system with said living eye and said objective lens positioned in the predetermined working distance; and

said control part is configured to perform;

a first control process that causes said detecting part to detect said interference light that is generated based on the signal light that is reflected from said fundus oculi after a distance between said living eye and said objective lens is matched to said working distance;

a second control process that, after said first control process, switches the light path of said reference light to a optical path length that corresponds to a depth zone of said anterior segment and also inserts said depth zone switching lens into said optical system while maintaining said working distance; and

a third control process that, after said second control process, cause said detecting part to detect said interference light that is generated based on the signal light that is reflected from said anterior segment.

4. The optical image measuring device according to claim 3, wherein:

said first control process is performed after a focus adjustment that changes the placement position of said focusing lens depending on the diopter of said living eye; and

said second control process comprises a control process that changes the placement position of said focusing lens to a predetermined position.

5. The optical image measuring device according to claim 1, wherein:

said measured object is the living eye;

said switching part is configured to switch to optical path lengths that correspond to a fundus oculi as said first depth zone and an anterior segment as said second depth zone;

said optical system is configured to condense said signal light into said fundus oculi;

said depth zone switching lens is configured to condense said signal light into said anterior segment when it is inserted into said optical system with said living eye and said objective lens positioned in the predetermined working distance; and

said control part is configured to perform;

a first control process that switches the light path of said reference light to the optical path length that corresponds to said anterior segment and also inserts said depth zone switching lens into said optical system;

a second control process that, after the first control process, causes said detecting part to output a detection result of said interference light based on the signal light that is reflected from said anterior segment;

a third Control process that, after matching a distance between said living eye and said objective lens that corresponds to said detection result from said second control process to said working distance, switches the optical path length to the optical path length that corresponds to a depth zone of said fundus oculi and also retracts said depth zone switching lens from said optical system while maintaining said working distance; and

a fourth control process that, after the third control process, causes said detecting part to detect said interference light that is generated based on the signal light that is reflected from said fundus oculi.

6. The optical image measuring device according to claims 1 through 5,

said switching part comprising:

a beam splitter that split a reference light that is split from said low-coherence light into two;

a first light path through which one of said two reference lights goes and that has an optical path length that corresponds to said first depth zone;

a second light path through which the other one of said two reference lights and that has an optical path length that corresponds to said second depth zone; and

a shading plate that shields said first and second light paths selectively, wherein

said control part is configured to insert said depth zone switching lens in synchronization with insertion of said shading plate into said first light path.

7. A control method of the optical image measuring device, having a splitting part that splits a low-coherence light into a signal light and a reference light, an optical system that comprises an objective lens and a focusing lens and that condenses said signal light to a fundus oculi, an interference light generation part that generates an interference light by causing interference with said signal light via said optical system after being reflected from said living eye and said reference light via a light path of the predefined optical path length, and a detecting part that detects said interference light, and forming a tomographic image based on a detection signal that is output from said detecting part, and the method comprising:

a first control process that matches the distance between said living eye and the objective lens to said working distance;

a second control process that switches the optical path length of said reference light to a first optical path length that corresponds to the depth zone of said fundus oculi;

a third control process that, after said first and second control processes, causes said detecting part to detect the interference light of the signal light reflected from said fundus oculi and said reference light via the light path of said first optical path length;

a fourth control process that, after said third control process, switches the optical path length of said reference light to a second optical path length that corresponds to a depth zone of the anterior segment of said living eye;

a fifth control process that, in synchronization with the fourth control process, inserts a depth zone switching lens that condenses said signal light to said anterior segment to said optical system while keeping said living eye and said objective lens positioned at said predetermined working distance;

a sixth control process that, after said fourth and fifth processes, causes said detecting part to detect the interference light of said signal light reflected from said anterior segment and the reference light via a light path of said second optical path length; and

a seventh control process that forms tomographic images of said fundus oculi and anterior segment based on interference lights detected in said third process and said sixth process, respectively.

8. The control method of optical image measuring device according to claim 7, wherein;

said first control process comprises a control process that changes the placement position of said focusing lens depending on the diopter of said living eye; and

the method further comprising

an eighth control process that, in synchronization with said fourth control process and said fifth control process, moves said focusing lens to a predetermined placement position.

9. A control method of the optical image measuring device, having a splitting part that splits a low-coherence light into a signal light and a reference light, an optical system that comprises an objective lens and a focusing lens and that condenses said signal light to a fundus oculi, an interference light generation part that generates an interference light by causing interference with said signal light via said optical system after being reflected from said living eye and said reference light via a light path of the predefined optical path length, and a detecting part that detects said interference light, and forming a tomographic image based on a detection signal that is output from said detecting part, and the method comprising:

a first control process that switches the optical path length of said reference light to a first optical path length that corresponds to the depth zone of an anterior segment of said living eye and also inserts the depth zone switching lens that condenses said signal light to said anterior segment to said optical system;

a second control process that causes said detecting part to detect an interference light of said signal light reflected from said anterior segment and the reference light via the light path of said first optical path length;

a third control process that matches a distance between said living eye and objective lens to a predetermined working distance based on a detection result of said interference light;

a fourth control process that, after said third control process, switches the optical path length of said reference light to a second optical path length that corresponds to the depth zone of said fundus oculi;

a fifth control process that, in synchronization with said fourth control process, retracts said depth zone switching lens from said optical system;

a sixth control process that, after said third and fourth control processes, causes said detecting part to detect an interference light of said signal light reflected from the fundus oculi and said reference light via the light path of said second optical path length; and

a seventh control process that forms a tomographic image of said fundus oculi based on the interference light detected in said sixth control process.