Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
  • G01B9/00—Measuring instruments characterised by the use of optical techniques
  • G01B9/02—Interferometers
  • G01B9/02015—Interferometers characterised by the beam path configuration
  • G01B9/02017—Interferometers characterised by the beam path configuration with multiple interactions between the target object and light beams, e.g. beam reflections occurring from different locations
  • G01B9/02019—Interferometers characterised by the beam path configuration with multiple interactions between the target object and light beams, e.g. beam reflections occurring from different locations contacting different points on same face of object
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B3/00—Apparatus for testing the eyes; Instruments for examining the eyes
  • A61B3/10—Objective types, i.e. instruments for examining the eyes independent of the patients' perceptions or reactions
  • A61B3/102—Objective types, i.e. instruments for examining the eyes independent of the patients' perceptions or reactions for optical coherence tomography [OCT]
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B5/00—Measuring for diagnostic purposes; Identification of persons
  • A61B5/0059—Measuring for diagnostic purposes; Identification of persons using light, e.g. diagnosis by transillumination, diascopy, fluorescence
  • A61B5/0062—Arrangements for scanning
  • A61B5/0066—Optical coherence imaging
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
  • G01B9/00—Measuring instruments characterised by the use of optical techniques
  • G01B9/02—Interferometers
  • G01B9/02001—Interferometers characterised by controlling or generating intrinsic radiation properties
  • G01B9/02007—Two or more frequencies or sources used for interferometric measurement
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
  • G01B9/00—Measuring instruments characterised by the use of optical techniques
  • G01B9/02—Interferometers
  • G01B9/02015—Interferometers characterised by the beam path configuration
  • G01B9/02027—Two or more interferometric channels or interferometers
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
  • G01B9/00—Measuring instruments characterised by the use of optical techniques
  • G01B9/02—Interferometers
  • G01B9/02083—Interferometers characterised by particular signal processing and presentation
  • G01B9/02089—Displaying the signal, e.g. for user interaction

Definitions

• the present invention relates to an imaging apparatus, and an optical coherence tomography system including an adjustable member within the imaging apparatus.
• OCT Optical Coherence Tomography
• a measurement light and a reference light are generated by dividing a light beam from a light source, and an imaging target is irradiated with the measurement light.
• a return light of the measurement light with which the subject's eye is irradiated, and the reference light are combined by a beam splitter to form an interference light, which enters a diffraction grating.
• the light is divided, and is converted into an electric signal by a sensor.
• a tomographic image of the imaging target can be obtained according to the signal of the interference light.
• Patent Document 1 discusses a technique for performing alignment of the interference light relative to a line sensor by moving the mirror and the diffraction grating by a piezoelectric element.
• Patent Document 2 discusses a technique for adjusting a position of a fiber end relative to the diffraction grating based on an irradiated state of the sensor with light.
• an optical coherence tomographic apparatus includes an interference light generation unit configured to generate an interference light in which a measurement light routed via a imaging target and a reference light routed via a reference object are combined, a light dividing unit configured to divide a light routed via the interference light generation unit for each wavelength, an imaging unit configured to receive the divided lights and convert the divided lights into an electric signal, an image forming unit configured to form a tomographic image of the imaging target according to the electric signal, and a display control unit configured to display a spectrum of a test light incident on an optical path expended from the interference light generation unit to the imaging unit, based on the electric signal which the imaging unit outputs.
• the user can check exactly whether an alignment between a light-receiving surface of the imaging unit and a light flux which reaches the imaging unit is properly performed.
• Fig. 1 is a configuration diagram of an OCT imaging apparatus according to an exemplary embodiment of the present invention.
• Fig. 2A illustrates a relationship between a fundus image and a scanning range by each measurement light.
• Fig. 2B illustrates an example of a tomographic image obtained in a first scanning range 505.
• Fig. 2C illustrates an example of a tomographic image obtained in a second scanning range 506.
• Fig. 2D illustrates an example of a tomographic image obtained in a third scanning range 507.
• Fig. 3A illustrates a display example indicating a light-receiving state of a line sensor 139.
• Fig. 3B illustrates a display example indicating a light-receiving state of the line sensor 139.
• Fig. 3A illustrates a display example indicating a light-receiving state of a line sensor 139.
• Fig. 3B illustrates a display example indicating a light-receiving state
• FIG. 3C illustrates a display example indicating a light-receiving state of the line sensor 139.
• Fig. 3D illustrates a display example indicating a light-receiving state of the line sensor 139.
• Fig. 4A illustrates a positional relationship between a line sensor and spectra.
• Fig. 4B illustrates a positional relationship between a line sensor and spectra.
• Fig. 4C illustrates a positional relationship between a line sensor and spectra.
• Fig. 5 illustrates a display screen example for adjustment.
• Fig. 6 illustrates another display screen example for adjustment.
• Fig. 7 illustrates another display screen example for adjustment.
• Fig. 8 is a flowchart illustrating a flow of processing for adjusting the light dividing device.
• Fig. 8 is a flowchart illustrating a flow of processing for adjusting the light dividing device.
• FIG. 9 is a flowchart illustrating a flow of automatic adjustment processing of the light dividing device.
• Fig. 10A illustrates a light-receiving state of the line sensor and spectra displayed on the display screen.
• Fig. 10B illustrates a light-receiving state of the line sensor and spectra displayed on the display screen.
• Fig. 10C illustrates a light-receiving state of the line sensor and spectra displayed on the display screen.
• Fig. 10D illustrates a light-receiving state of the line sensor and spectra displayed on the display screen.
• Fig. 11 illustrates a light-receiving state of another line sensor and spectra displayed on the display screen.
• Fig. 1 is a block diagram illustrating a basic configuration of an OCT imaging apparatus (hereinafter referred to as OCT apparatus) according to an exemplary embodiment of the present invention.
• An OCT apparatus 100 constitutes, as illustrated in Fig. 1, a Michelson interferometer as a whole, and is a Spectral Domain scheme OCT (herein after referred to as SD-OCT) or an optical coherence tomographic apparatus. Further, the OCT apparatus 100 is a multi-beam type OCT apparatus that causes a signal light emitted from a low-coherence light source to be simultaneously incident on a plurality of positions of an imaging target, and forms a tomographic image based on a return light from the imaging target of the light caused to be incident.
• SD-OCT Spectral Domain scheme OCT
• An emission light 104 as a low-coherence light emitted from a light source 101 is guided by a single mode fiber 110 to be incident on an optical coupler 156, and is divided by the optical coupler 156 into the emission lights 104-1 to 104-3 which pass through three optical paths consisting of a first optical path and a second optical path and a third optical path, respectively.
• these three emission lights 104-1 to 104-3 each pass through optical fibers which form the optical paths, pass through polarization controllers 153-1, and are divided into the reference lights 105-1 to 105-3 and the measurement lights 106-1 to 106-3 at the optical couplers 131-1 to 131-3 as an interference light generation unit.
• Three measurement lights 106-1 to 106-3 thus divided are returned as return lights 108-1 to 108-3 reflected or scattered by respective measurement areas of a retina 127 in a subject's eye 107 as an imaging target.
• the returned lights 108-1 to 108-3 are mixed with the reference lights 105-1 to 105-3 which have been routed through the reference light paths by the optical couplers 131-1 to 131-3 as the interference light generation unit, and are interfered with each other depending on differences of optical path lengths between the measurement lights and the reference lights, thus generating the interference lights 142-1 to 142-3.
• the optical coupler 131-1 functions as the interference light generation unit which divides a low-coherence light from the light source 101 into the measurement lights and the reference lights, and combines the measurement lights routed through the imaging target and the reference lights routed through the reference object, thus generating the interference lights.
• the interference lights 142-1 to 142-3 pass through the polarization controllers 153-3, and exit from an optical fiber end.
• the exit light is divided by a transmission type diffraction grating 141 as a light dividing unit for each wavelength, and is caused to be incident on a line sensor 139 as an imaging unit via a lens 143, and the line sensor 139 receives the light.
• An optical system and the line sensor 139 of the light dividing device are arranged so that the interference lights 142-1 to 142-3 each reach different positions of an image-receiving surface of the line sensor 139. Therefore, the line sensor 139 will have thereon a region which receives the interference light 141-1, a region which receives the interference light 141-2, a region which receives the interference light 141-3, in the order from edge.
• the line sensor 139 as the imaging unit receives lights with respective wavelengths for each sensor element (pixel) and converts a light intensity into an electric signal.
• the computer 125 acting as an image formation unit forms a tomographic image of the subject's eye 107 according to the electric signal.
• Light intensity herein used is quantity of light which enters the sensor per unit time.
• a motor-driven stage 210 as an adjustment unit adjusts relative positional relationship between a light-receiving surface of the line sensor 139 which receives the interference lights 142-1 to 142-3, and light fluxes of the interference lights by moving a position of the line sensor 139.
• Light flux herein used means a bundle of light rays.
• relative position between the light-receiving surface and the light fluxes means geometrical positional relationship between the light-receiving surface and the light fluxes, and means an incidence angle relative to the light-receiving surface of the light fluxes directed toward the line sensor 139, and an incidence position or range.
• This adjustment is implemented by the motor-driven stage 210 causing the line sensor 139 to translate or rotate.
• the motor-driven stage 210 is controlled by the computer 125 acting as a control unit.
• the computer 125 issues a control command of the motor-driven stage 210, according to an instruction of adjustment input at an operation unit (not illustrated) of the computer 125, and the motor-driven stage 210 can change a position of the sensor according to the control command.
• the test light reaches the line sensor 139 as three light fluxes corresponding to three emission lights.
• a spectrum of the test light obtained according to an electric signal which the line sensor 139 outputs is displayed on the monitor 130 by the computer 125 acting as the control unit. Accordingly, a user or a person who performs maintenance of the apparatus can check whether the test light properly reaches the line sensor 139 due to arrangement of the optical system or the line sensor 139.
• Test reach herein used means a case where the test light is incident on the light-receiving surface of the line sensor 139 or a case where the test light is not incident on the light-receiving surface but within a range of the permissible value.
• each of the spectra of the test light is displayed on the monitor 130.
• the test light is caused to be entered into the optical paths (the optical paths from the optical couplers 131-1 to 131-3 to the line sensor 139) through which a plurality of light fluxes of the measurement light (the return light) routed via the imaging target through the optical couplers 131-1 to 131-3 reach the imaging unit.
• the light-receiving state of the test light (the measurement light, the reference light or the interference light) which the line sensor 139 receives can be changed. Then, display of the light-receiving state to be displayed on a display unit (not illustrated) will be switched by a display control of the computer 125, according to such adjustment.
• a display example of the light-receiving state will be described below.
• Each of three reference lights 105-1 to 105-3 divided by the optical couplers 131-1 to 131-3 passes through the polarization controllers 153-2, and is rendered to be substantially parallel by the lens 135 and exits therefrom.
• the reference lights 105-1 to 105-3 pass through a dispersion compensation glass 115, and are collected on mirrors 114-1 to 114-3 as an example of a reference object, by the lenses 135-2.
• the reference lights 105-1 to 105-3 are changed in their directions by the mirrors 114-1 to 114-3 as the example of the reference object, and are again directed toward the optical couplers 131-1 to 131-3.
• the dispersion compensation glass 115 is used to compensate for dispersion generated when the measurement light 106 has travelled between the subject's eye 107 and a scanning optical system, to the reference light 105.
• an optical path length of the reference light 105 can be changed by moving motor-driven stages 117-1 to 117-3 in a direction indicated by an arrow.
• the motor-driven stages 117-1 to 117-3 are controlled by the computer 125, and the optical path lengths of the reference lights 105-1 to 105-3 can be changed each independently, or simultaneously.
• the XY scanner 119 is described as one mirror, but in practice, two mirrors including a mirror for X scanning and a mirror for Y scanning are arranged in proximity to each other, and perform raster scanning in a direction normal to an optical axis on the retina 127.
• the lenses 120-1 and 120-3 are adjusted so that a center of each of the measurement lights 106-1 to 106-3 substantially agrees with a center of rotation of a mirror of the XY scanner 119.
• the lenses 120-1 and 120-2 are an optical system for scanning the retina 127 with the measurement lights 106-1 to 106-3, and is used to scan the retina 127 with the measurement light 106 by causing an area near a cornea 126 to serve as a fulcrum or pivot point.
• the measurement lights 106-1 to 106-3 each form an image on an arbitrary position on the retina 127.
• the motor-driven stage 117-4 can move in a direction indicated by an arrow, and can adjust and control a position of the lens 120-2 attached thereto. By adjusting the position of the lens 120-2, each of the measurement lights 106-1 to 106-3 can be collected onto a desired layer of the retina 127 of the subject's eye 107 and can be observed.
• the measurement lights 106-1 to 106-3 When the measurement lights 106-1 to 106-3 are incident on the subject's eye 107, they become the return lights 108-1 to 108-3 due to reflection or scatter from the retina 127, and the return lights 108-1 to 108-3 pass through the optical couplers 131-1 to 131-3, and are guided to the line sensor 139.
• the motor-driven stage 117-4 is controlled by the computer 125. Through the above-described configuration, three measurement lights can scan the target object simultaneously.
• the return lights 108-1 to 108-3 reflected or scattered at the retina 127 as the imaging target are mixed with the reference lights 105-1 to 105-3 by the optical coupler 131-1 to 131-3, and the mixed interference lights 142-1 to 141-3 are incident on the light dividing device, and then the spectra are obtained.
• the computer 125 acting as the image formation unit performs formation processing of tomograms on these spectra, and thereby the tomograms can be obtained.
• reconfiguration processing a generation process of general OCT images can be employed, and the tomograms can be generated by performing fixed pattern noise removal, wavelength-to-wave number conversion, Fourier transformation.
• Fig. 2A illustrates an example of regions on the retina in the fundus and tomograms captured by the above-described OCT apparatus.
• a fundus 501 as illustrated in a fundus image in Fig. 2A and a tomographic image in Fig. 2B, a macula flava 502, an optic disk 503 and blood vessels 504 and the like exist.
• Three measurement lights 106-1 to 106-3 scan a first scanning range 505, a second scanning range 506, and a third scanning range 507, respectively, and examples of tomographic images obtained by respective scanning operations are given in Figs. 2B, 2C, 2D, respectively.
• Respective regions are overlapped by about 20%, as illustrated in Fig. 2A as an overlap 508 between the first scanning range and the second scanning range, and an overlap 509 between the second scanning range and the third scanning range.
• Coordinate axes are set as illustrated in Figs. 2B to 2D, and scanning in an x-direction is called fast-scan, scanning in a y-direction is called slow-scan, and a z-direction extends from back surface side to front surface side to the drawing surface of Figs. 2A to 2D.
• a near-infrared light 190 emitted from a near-infrared light source 180 is irradiated onto the fundus 127 via a half mirror 200, an illumination optical system 150, and a dichroic mirror 220 that is inserted within the measurement light path.
• the near-infrared light reflected at the fundus returns again through the same optical path, forms an image on two-dimensional area sensor 170 via the half mirror 200, and an image-formation optical system 160.
• Two-dimensional image of the fundus which has been captured in this way is input into the computer 125. This two-dimensional image is used to observe the region of OCT imaging.
• a shutter 230 arranged in the measurement light path can block incidences of the measurement lights 106-1 to -3 on the fundus 127 by a driving device (not illustrated) under control of the computer 125.
• Figs. 3A to 3D illustrate display examples of spectra of respective reference lights projected on the line sensor 139.
• Figs. 3A to 3D three spectra 144-1 to -3 are projected on the line sensor 139, and signals read out from the line sensor 139 are subjected to reconstruction processing for each of the regions illustrated in SR1 to SR3, thus generating the tomograms. Then, image data for display is generated by the computer 125 as a display control unit based on the tomographic images, and is displayed on a display unit (not illustrated).
• FIG. 4 illustrates positional a relationship between light fluxes which the line sensor 139 receives and the light-receiving surface of the line sensor 139.
• the light-receiving surface of the line sensor 139 is illustrated, and spectra of lights, which are incident on the light-receiving surface in a direction extended from front surface side to back surface side to the drawing surface of Fig. 4A to 4C are indicated by oblique lines.
• Fig. 3A is an example of display, which is an example in which values of electric signals according to light quantity which the line sensor 139 receives on the light-receiving surface are directly displayed as they are.
• horizontal axis is a position of the line sensor and at the same time corresponds to wavelength, and vertical axis corresponds to signal intensity for each wavelength.
• the horizontal axis may represent frequency to display intensity with respect to the frequency.
• Fig. 4A Light-receiving state corresponding to the state illustrated in Fig. 3A is illustrated in Fig. 4A.
• spectra 144-1 to 144-3 corresponding to respective measurement lights are properly incident on the light-receiving surface of the line sensor 139.
• peaks of the spectra illustrated in Fig. 3A are large, and variation between the spectra is small. In this way, a light-receiving state of the line sensor can be presented in a visually easy-to-understand manner to the user, by displaying shapes of the spectra.
• Fig. 3B is another display example, and is a display in the case where positional relationship between the line sensor 139 and the light flux of the reference light is deviated.
• the spectrum 144-1 and the spectrum 144-2 are smaller than the spectrum 144-3. This is a phenomenon that occurs since lights received at the portions corresponding to the regions SR1 and SR2 of the line sensor 139 become weak.
• Fig. 4B This light-receiving state corresponding to the state illustrated in Fig. 3B is illustrated in Fig. 4B.
• the line sensor 139 has been inclined relative to the light fluxes of the respective measurement lights. Then, especially the spectrum 144-1 is not properly incident on the line sensor 139. Accordingly, a peak of the spectrum 144-1 is small in Fig. 3B.
• the effect described for the above-described displays in Fig. 3A and Fig. 3B, is not limited to especially multi-beam type OCT apparatus, but similar effect is obtained for single beam type OCT apparatus as well.
• the multi-beam type apparatus since a plurality of spectra are displayed, the light-receiving state can be displayed in an easy-to-understand manner, and the shift of relative position between the line sensor and the light can be presented to the user, by displaying so that shapes of the respective spectra can be compared with one another.
• the light-receiving state will be determined based on a shape of one spectrum. Compared to this, in multi-beam type, since a plurality of shapes can be compared, the effect of the display according to the present exemplary embodiment can be expected.
• the respective interference lights need to be properly aligned relative to the line sensor, so that image quality may not vary for each of the measurement regions by the respective measurement lights.
• Fig. 3C illustrates another display example, and magnitudes of the respective spectra are smaller, in comparison with those in Fig. 3A.
• the reason is considered that because, although the line sensor 139 and the light flux of the reference light are not rotated relative to each other, they are translated relative to each other, and the lights which respective areas of the line sensor 139 receive have become weak as a whole.
• the light-receiving state corresponding to the state illustrated in Fig. 3C is illustrated in Fig. 4C.
• the line sensor 139 is shifted in a direction orthogonal to the longitudinal direction relative to the light flux.
• Fig. 3D is yet another display example, and is an example in which magnitudes of peaks of spectra of the test lights are displayed as numerical values corresponding to the respective spectra 144-1 to 144-3.
• the magnitudes of peaks are used as feature quantity indicating light quantity or light intensity of each reference light. In this way, there is an advantage that quantities to be adjusted can be presented to the user as not only shapes of spectra, but also numerical values of the peaks, by displaying the magnitudes of peaks as numerical values.
• examples of displaying spectra of the lights have been illustrated as a display of the light-receiving state of lights by the line sensor. However, it is not limited thereto, and peak values or areas of the spectra may be also displayed as values indicating light quantities. Further, a display indicating whether each of the regions SR1 to SR3 of the line sensor which receive the reference lights or the interference lights corresponding to the respective measurement lights is illuminated with a light equal or greater than a threshold value may be performed
• the optical coherence tomographic apparatus may have a plurality of light sources.
• a plurality of light sources with relatively small light intensity can be also used, without using a single light source with a high light intensity.
• a line sensor may be provided independently for each of the measurement lights.
• the need to independently adjust each sensor arises, but positional relationship between light fluxes of lights which the respective sensors receive, and the sensors can be adjusted more precisely.
• a position of a fiber end of an optical fiber or orientation of a light exiting from the fiber end may be adjusted, a position of a lens disposed between the fiber end and a light dividing unit may be adjusted, a position of a diffraction grating may be adjusted, or a position of the lens disposed between the diffraction grating and the line sensor may be adjusted.
• a display of spectra illustrated in a display example according to the first exemplary embodiment, and "A" scan image or a profile of "A" scan and "B” scan image and the like are displayed. Further, the display screen where adjustment and its confirmation are possible by scanning icons on the display screen is provided.
• the computer 125 acquires outputs of the line sensor 139, and generates spectrum information and "A" scan image, "B" scan image to be used for the display screen.
• Setting information such as images of icons and arrangement of the display is stored in the computer 125 in advance.
• Image data of the display screen is generated according to the acquired information and the setting information, and the computer 125 executes processing of performing display control.
• the user can click buttons and other icons using a mouse or keyboard (not illustrated) connected to the computer 125.
• the computer 125 acquires the operation information, and executes a control of the motor-driven stage 210 according to the operation information.
• the computer 125 generates image data of a new display screen based on newly acquired outputs from the line sensor 139, and performs display control for causing the display unit to display the image data. Through this control, the display screen will be switched.
• Fig. 5 is an example of the display screen for adjustment.
• a spectrum display region 600 three spectra are displayed as illustrated in the exemplary embodiment previously described referring to Figs. 3A to 3D.
• the display of the spectra is updated sequentially by continuously processing outputs of the line sensor 139, and performing display control by the computer 125.
• Signals obtained by subjecting three spectra 144-1 to 144-3 to reconstruction processing are displayed in tomogram signal display regions 603-1 to 603-3. In the present exemplary embodiment, they are to be called "A" scan image or a profile of "A" scan line.
• a tomogram display region 605 is a region where a plurality of "A" scans obtained by driving a mirror for X scanning are displayed as two-dimensional images by well-known interpolation processing.
• a tomogram composed of the plurality of "A" scans is called "B" scan image.
• the "A" scan image or the "B" scan image are not displayed in the tomogram signal display regions 603-1 to 603-3, and the tomogram display region 605.
• Region select buttons 606-1 to 606-3 are icons for selecting a display of any one of the tomograms by three measurement lights.
• a tomographic image corresponding to A-A' cross-section illustrated in Fig. 2A is displayed in the tomogram display region 605 by an operator of the apparatus by pressing a switch displayed as a region "A”.
• B-B' cross-section will be displayed by pressing a display of a region "B”
• C-C' cross-section will be displayed by pressing a display of a region "C”.
• the reference light is displayed as a spectrum display, displays of the spectrum display region 600 or the tomogram signal display regions 603-1 to 603-3 will not be changed.
• a slider 604-1 and a slider 604-2 in Fig. 5 are sliders for adjusting the position of the line sensor 139 relative to the spectra by driving the motor-driven stage 210.
• the height and rotation of each line sensor can be adjusted relative to the spectrum by operating these sliders by an operator.
• Height herein used refers to a displacement or an amount of movement in a direction orthogonal to a longitudinal direction of the line sensor.
• “Rotation” refers to a rotation around an axis which passes through a center point with respect to the longitudinal direction of the line sensor 139, and is orthogonal to a plane including the light-receiving surface. The center of rotation is not limited to a midpoint with respect to the longitudinal direction of the line sensor 139.
• the line sensor may be configured to be able to perform translational or rotational movement out of the plane including the light-receiving surface.
• the line sensor may be movable in three axes directions using a motor and a feed screw. Since the display of the spectrum display region 600 will be switched by operation of these sliders, the user can adjust a position of the line sensor by the operation on the screen, and check a result of the adjustment on the display screen.
• Light source buttons 607-1 and 607-2 are used to turn ON or OFF the power source of the light source 101, thereby emission of the low-coherence light from the light source 101 is stopped, and the spectra cease to be displayed in the spectrum display region 600.
• the optical paths of the measurement lights 106-1 to 106-3 can be blocked or opened by driving a shutter 230.
• the optical path is opened by the shutter 230, the interference light containing tomogram information of the retina will be obtained, and spectra of the interference light will be displayed in the spectrum display region 600, in a case where an objective lens is arranged ahead of the subject's eye.
• the light-dividing device is adjusted using only the reference light in a state where the measurement light is blocked by operating the shutter 230.
• this is not essential for the present exemplary embodiment, and the light-dividing device may be adjusted using a stable standard object such as a model eye. In this case, adjustment is performed in a state where the shutter button 608-1 is pressed by the operator, and the shutter 230 is opened.
• an adjustment screen becomes the one as illustrated by an example in Fig. 6. That is, a tomogram of the model eye is displayed in the tomogram display region 605, and tomogram signals ("A" scan profiles) generated from the respective spectra are displayed in the tomogram signal display regions 603-1 to 603-3.
• both of light-receiving state and "A" scan profile of the respective measurement lights based on such display, information can be presented, so that the user can check magnitude of signal components with regard to a certain "A" scan profile, and determine based thereon whether adjustment is necessary.
• the reference light can be displayed by shielding the optical path by pressing the shutter button 608-2.
• the display of the tomogram display region 605 can be switched by the region select buttons 606-1 to 606-3 provided above the display region 605.
• Fig. 6 illustrates a state where the region "A" in the middle is selected, and B scanned image by the measurement light of the region "A” is displayed in the tomogram display region 605.
• the interference light acquired based on the measurement light, which is irradiated on a certain position of the imaging target is to be displayed is determined in advance according to the selection of a region.
• the interference light at central position may be used, or the interference light at edge may be used, for the respective measurement lights. Further, averaging of the spectra of the interference lights corresponding to a plurality of "A" scan positions may be displayed.
• the optical interference imaging apparatus has a mode for automatically executing adjustment of the light dividing device, in addition to a mode in which the user manually adjusts the light dividing device.
• FIG. 7 An example of the display screen which is display-controlled by the computer 125 is illustrated in Fig. 7.
• automatic adjustment will be executed by displaying a button 602 for instructing an execution of the automatic adjustment as an icon, and by pressing the button on the screen via the operation unit (not illustrated) by the user.
• step S100 the computer 125 displays a screen for adjustment of the light dividing device on the monitor 130.
• the display screen is similar to that in the previously described second exemplary embodiment, except that an automatic adjustment button 602 is arranged. Therefore, description thereof will not be repeated.
• step S200 the computer 125 detects whether the automatic adjustment button 602 has been pressed by the operator. If not pressed (NO in step S200), the computer 125 shifts the mode to a manual mode in step S300. If pressed (YES in step S200), the computer 125 shifts the mode to an automatic mode in step S400.
• step S300 the computer 125 monitors whether each operation button illustrated in Fig. 7 is pressed, and shifts the mode to the manual mode in which adjustment is performed under the operation of the operator.
• the manual mode is a mode in which a position of the line sensor 139 is manually adjusted under the operation of the operator.
• adjustment is assumed to be performed in a state where the shutter 230 blocks the measurement lights 106-1 to 106-3. More specifically, the shutter button 608-2 is pressed by the operator, thereby the shutter 230 blocks the measurement light, and as a result, only the spectra of the reference lights 105-1 to 105-3 are assumed to be incident on the line sensor 139.
• shapes of the spectra displayed in the spectrum display region 600 immediately after start of adjustment may be in a state as illustrated in Fig. 3B.
• the computer 125 drives the motor-driven stage 210 to rotate the line sensor 139.
• the operator By further operating the slider 604-1, the operator, while monitoring the shapes of the spectra 144-1 to 144-3 displayed in the spectrum display region 600, adjusts a position of the line sensor 139 so that these heights are uniform, and become highest.
• the spectra detected by the line sensor correspond to the state in Fig. 3C.
• the computer 125 drives and rotates the line sensor 139, which becomes the state in Fig. 4B.
• the computer 125 causes the line sensor 139 to perform translational movement, and finally the line sensor 139 becomes the state in Fig. 4A.
• the line sensor is properly aligned relative to the respective spectra.
• the computer 125 computes areas or peak values of respective spectra which are input sequentially, and the computed numerical values may be displayed near the spectra within the spectrum display region 600. In this way, it is favorable since to the user can check the heights and balance of the respective spectra more easily.
• Fig. 3D is an example of a form of the display, where peak values which the computer 125 has computed on the respective spectra are displayed together with arrows. Although peak values of the spectra are displayed in this example, as a matter of course, areas or other numerical values may be displayed, and a position of the display may be anywhere on the display screen illustrated in Fig. 7.
• step S400 when an automatic adjustment button 602 is pressed by the operator in step S200, the computer 125 shifts to the automatic mode. In this mode, adjustment described in step S300 is automatically performed.
• step S410 the computer 125 turns ON the power source of the light source 101, and causes the shutter 230 to be operated, thus the measurement lights 106-1 to 106-3 are blocked. Accordingly, only the spectra of the reference light 105-1 to 105-3 will be incident on the line sensor 139.
• step S420 the computer 125 moves the position of the line sensor 139 to a state where any of three spectra is not incident.
• Fig. 10A illustrates a positional relationship at this time between the line sensor and the spectra and intensities of the spectra detected by the line sensor, and no spectra are detected in this step.
• step S430 the computer 125 inputs sequentially the detection results of the spectra from the line sensor 139, while causing the line sensor 139 to perform parallel movement in a direction indicated by an upward arrow in Fig. 10A.
• the computer 125 monitors a height of the spectrum 144-2 positioned in the middle, and stops the movement at a position where it becomes maximal. The state at this time is illustrated in Fig. 10B.
• step S440 the computer 125 checks whether a difference of heights of spectra detected by the line sensor 139 falls within a permissible range. If within a permissible range (YES in step S440), the computer 125 advances the processing to step S460. On the other hand, If not (NO in step S440), the computer 125 advances the processing to step S450.
• This permissible range may be determined based on difference between image qualities due to the difference between the spectra. More specifically, heights of the spectra affect sensitivity for extracting a structure of the object, and sensitivity is lowered as a whole, when the heights of the spectra are low, and as a result, the tomogram obtained by reconstructing become dark.
• step S450 the computer 125 inputs sequentially the detection results of the spectra from the line sensor 139, while rotating the line sensor 139 toward the direction indicated by an arrow in Fig. 10B.
• step S450 heights of the three spectra 144-1 to 144-3 are all monitored, and rotation is stopped at an angle at which three heights become substantially the same. The state at this time is illustrated in Fig. 10C.
• step S460 the computer 125 checks whether heights of three spectra and their differences fall within a specified range. If within a specified range (YES in step S460), the computer 125 terminates adjustment. If not (NO in step S460), the computer 125 advances the processing again to step S430. If the processing proceeds to step S430, the line sensor 139 is moved as illustrated in Fig. 10C, and similar processing will be repeated again.
• positions of the sensor and the interference light can be properly adjusted.
• their heights are used as an index representing characteristics of the spectra detected by the line sensor 139, but the present invention is not limited to this and, for example, areas of spectra may be used.
• adjustment of the light dividing device may be performed using the spectra including interference signals.
• a flow of the processing is basically similar to that in the first exemplary embodiment. However, since interference signals are included in the spectra detected by the line sensor 139, when heights of the spectra are evaluated, in step S440, and step S460, adjustment is performed using heights including the interference signals.
• step S410 when initial setting is performed, first, the computer 125 acquires three spectra 144-1 to 144-3 while the shutter 230 is closed, and stores them in a memory inside the computer 125. Next, subtraction is made from the spectra acquired while the shutter 230 is opened, to obtain only interference signals, and amplitudes of these signals may be used as the index.
• the line sensor 139 is composed of one row of detection elements, a two-dimensional sensor or a line sensor having a plurality of rows of elements can be used in the present exemplary embodiment.
• Fig. 11 illustrates an example of a spectrum in a case where such a sensor is used.
• the line sensor 139 In the line sensor 139, two rows of detection elements 139-1 and 139-2 are arrayed, and the output signals thereof are input into the computer 125.
• a spectrum by a detection element row 139-1 is illustrated by a dashed line
• a spectrum by a detection element row 139-2 is illustrated by a solid line.
• Amounts indicating the light-receiving state include the height of spectrum, average position, variation (standard deviation), and area in wavelength-intensity graph. Adjustment is made so that one or all of these indexes are equal to or greater than a certain value, and a difference between respective rows falls within a predetermined range.
• these two types of spectra are displayed in an identifiable manner in the spectrum display region 600 as illustrated in Fig. 11. Since the light-receiving surface becomes larger in size, by using a two-dimensional sensor or a sensor having a plurality of rows, adjustment becomes easier, and time and work for adjustment can be reduced.
• the processing performed in the image processing apparatus may be distributed among a plurality of apparatuses and implemented as a system, or the processing configured as one functional block may be distributed among a plurality of circuits or apparatuses and implemented.
• the present invention may be realized by the optical coherence tomographic apparatus.
• the present invention is realized by supplying a recording medium which has recorded a program code of software that implements the functions of the above-described exemplary embodiments to system or apparatus, and by executing the program code stored in the recording medium by a CPU in the system or apparatus.
• OS operating system
• a case where operating system (OS) running on the computer performs a part or whole of actual processing, by executing a program code which the computer has read out, and the functions of the above-described exemplary embodiments are implemented by the processing is also included in the present invention.
• the functions may be distributed to a plurality of CPUs to realize the present invention.
• the program code itself read out from the recording medium will implement the functions of the above-described exemplary embodiments, and the recording medium that has recorded the program or program code will constitute the present invention.
• the present invention is realized by circuits mounted by hardware and the functions implemented by the cooperation of software and hardware.
• OCT imaging apparatus 125 computer 139 line sensor 141 diffraction grating 210 motor-driven stage 600 spectrum display region 602 automatic adjustment button 604-1 line sensor height adjustment slider 604-2 line sensor rotation adjustment slider

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