Imaging apparatus and imaging method using optical coherence tomography

Abstract

Provided is an imaging apparatus using Fourier-domain optical coherence tomography, the imaging apparatus removing noises caused by the autocorrelation component of returning light to obtain a high-resolution tomographic image. A first switching unit 17 switches a first state in which returning light 12 is combined with reference light (a state in which the returning light 12 is conducted to a combining unit 22 ) and a second state different from the first state (a state in which the light path of the returning light 12 is blocked or changed). A controlling unit 18 controls the switching unit 17 to change the first and the second state. A interferometric information acquiring unit 19 acquires interferometric information on the returning light 12 and the reference light 14 using the reference light 14 or the returning light 12 detected by the detecting unit 16 in the second state and the combined light 15.

1 - 16 . (canceled) 
     
     
         17 . An imaging apparatus for imaging an object using Fourier domain optical coherence tomography, the imaging apparatus comprising:
 a detecting unit for detecting combined light comprising a returning light from the object and a reference light;   a switching unit for switching between a first state in which the detecting unit can detect the combined light and a second state in which the detecting unit can detect the reference light;   an acquiring unit for acquiring interferometric information on the returning light and the reference light by using the combined light detected by the detecting unit in the first state and the reference light detected by the detecting unit in the second state; and   a controlling unit for controlling the switching unit such that the reference light is detected in the second state after processing for acquiring the interferometric information is started and the second state is switched to the first state after the reference light is detected in the second state.   
     
     
         18 . The imaging apparatus according to  claim 17 , wherein the object is an eye, and
 wherein the imaging apparatus further comprises a scanning unit for scanning a measuring light in the retina of the eye with a vicinity of the cornea of the eye as a fulcrum.   
     
     
         19 . The imaging apparatus according to  claim 17 , wherein the switching unit is configured such that one of a light path of a measuring light to be irradiated on the object and a light path of the returning light can be blocked, and
 wherein the second state is in the blocked state.   
     
     
         20 . The imaging apparatus according to  claim 17 , wherein the switching unit is configured such that the transmittance of one of a measuring light to be irradiated on the object and the returning light can be controlled. 
     
     
         21 . The imaging apparatus according to  claim 17 , further comprising:
 a light quantity detecting unit for detecting the light quantity of a measuring light to be irradiated on the object; and   a comparing unit for comparing the detected light quantity with a predetermined value,   wherein when the detected light quantity is different from the predetermined value, the switching unit switches to the second state by blocking the measuring light.   
     
     
         22 . The imaging apparatus according to  claim 17 , wherein the switching unit is configured such that one of the light path of a measuring light to be irradiated on the object and the light path of the returning light can be changed, and
 wherein the second state is the changed state.   
     
     
         23 . The imaging apparatus according to  claim 17 , wherein the controlling unit controls the switching unit based on a predetermined timing, and the combined light is detected by the detecting unit at the timing of the first state. 
     
     
         24 . The imaging apparatus according to  claim 17 , further comprising a light quantity detecting unit for detecting the quantity of a measuring light to be irradiated on the object,
 wherein the controlling unit is configured such that the quantity of the measuring light is detected after processing for acquiring the interferometric information is started, the reference light is detected in the second state after the quantity of the measuring light is detected, and the second state is switched to the first state after the reference light is detected in the second state.   
     
     
         25 . The imaging apparatus according to  claim 17 , further comprising:
 a light source for emitting light;   a splitting unit for splitting light from the light source into the reference light and a measuring light to be irradiated on the object;   a subtracting unit for subtracting the autocorrelation component of the reference light and the autocorrelation component of the returning light from the combined light detected by the detecting unit;   a standardizing unit for standardizing the subtraction result by the autocorrelation component of the reference light;   a transforming unit for Fourier transforming the standardization result; and   an image acquiring unit for obtaining a tomographic image of the object to be detected.   
     
     
         26 . An imaging method for imaging an object using a Fourier domain optical coherence tomography, the imaging method comprising:
 detecting combined light comprising a returning light from the object and a reference light;   switching between a first state in which the combined light can be detected and a second state in which the reference light can be detected; and   acquiring interferometric information on the returning light and the reference light by using the combined light detected in the first state and the reference light detected in the second state,   wherein the reference light is detected in the second state after processing for acquiring the interferometric information is started and the second state is switched to the first state after the reference light is detected in the second state.   
     
     
         27 . The imaging method according to  claim 26 , wherein the object is an eye, and
 wherein the method further comprises scanning a measuring light in the retina of the eye with a vicinity of the cornea of the eye as a fulcrum.   
     
     
         28 . The imaging method according to  claim 26 , further comprising:
 emitting light from a light source;   splitting the light from the light source into the reference light and a measuring light to be irradiated on the object;   subtracting the autocorrelation component of the reference light and the autocorrelation component of the returning light from the combined light;   standardizing the subtraction result by the autocorrelation component of the reference light;   Fourier-transforming the standardization result; and   obtaining a tomographic image of the object to be detected.   
     
     
         29 . The imaging method according to  claim 26 , further comprising:
 detecting the light quantity of a measuring light to be irradiated on the object;   comparing the detected light quantity with a predetermined value; and   switching to the second state by blocking the measuring light when the detected light quantity is different from the predetermined value.   
     
     
         30 . A non-transitory computer-readable storage medium storing a program for causing a computer to execute the imaging method according to  claim 26 . 
     
     
         31 . The imaging method according to  claim 26 , further comprising detecting the light quantity of a measuring light to be irradiated on the object,
 wherein the light quantity of the measuring light is detected after processing for acquiring the interferometric information is started, the reference light is detected in the second state after the light quantity of the measuring light is detected, and the second state is switched to the first state after the reference light is detected in the second state.   
     
     
         32 . The imaging apparatus according to  claim 17 , further comprising:
 an image acquiring unit which acquires, from information of a tomography image of the object based on the intensity of the combined light, a tomography image in which information based on the intensity of the reference light is reduced.   
     
     
         33 . The imaging apparatus according to  claim 32 , further comprising:
 a subtracting unit which subtracts the information which is based on the intensity of the autocorrelation component of the reference light, from the information of the tomography image of the object which is based on the intensity of the combined light,   wherein the image acquiring unit acquires the reduced tomography image based on the subtraction result of the subtracting unit.   
     
     
         34 . An imaging apparatus for imaging an object a retina of an eye using Fourier-domain optical coherence tomography, the imaging apparatus comprising:
 a scanning unit for scanning a measuring light on the retina, with a cornea of the eye as a fulcrum;   a detecting unit for detecting combined light comprising a returning light from the retina and a reference light;   a first switching unit for switching between a first state in which the detecting unit can detect the combined light and a second state in which the detecting unit can detect the reference light;   an interferometric information acquiring unit for acquiring interferometric information on the returning light and the reference light by using the combined light detected by the detecting unit in the first state and the reference light detected in the second state;   a light quantity detecting unit for detecting the quantity of a measuring light to be irradiated on the retina; and   a comparing unit for comparing the detected light quantity with a predetermined value,   wherein when a measuring light quantity is different from the predetermined value, the first switching unit switches to the second state by blocking the measuring light.   
     
     
         35 . An imaging method for imaging a retina of an eye using a Fourier domain optical coherence tomography, the imaging method comprising:
 scanning a measuring light on the retina, with a cornea of the eye as a fulcrum;   switching between (a) a first state in which combined light comprising a returning light from the retina and a reference light can be detected and (b) a second state in which the reference light can be detected;   obtaining interferometric information on the returning light and the reference light by using the combined light detected in the first state and the reference light detected in the second state;   detecting the light quantity of the measuring light to be irradiated on the retina; and   changing to the second state by blocking the measuring light when the light quantity is different from a predetermined light quantity.   
     
     
         36 . An imaging apparatus for imaging a retina of an eye using Fourier-domain optical coherence tomography, comprising:
 a scanning unit for scanning a measuring light on the retina, with a cornea of the eye as a fulcrum;   a detecting unit for detecting one of (a) reference light and (b) combined light into which returning light obtained by radiating measuring light to the retina and reference light corresponding to a measuring light are combined;   a first switching unit for switching between a first state in which the detecting unit can detect the combined light and a second state in which the detecting unit can detect the reference light;   a determining unit for determining whether or not a measuring light quantity is no more than a predetermined value;   a controlling unit for controlling the first switching unit such that in a case where the determining unit determines that the measuring light quantity is no more than the predetermined value, the first switching unit switches from the second state to the first state; and   a tomographic image acquiring unit for acquiring, after the detecting unit detects the combined light in the first state, a tomographic image in which information based on an intensity of the reference light is cut down from information of a tomographic image obtained based on an intensity of the combined light.   
     
     
         37 . The imaging apparatus according to  claim 36 , further comprising:
 a subtraction unit for subtracting information based on an intensity of autocorrelation component of the reference light from the information of the tomographic image obtained based on the intensity of the combined light,   wherein the tomographic image acquiring unit acquires the cut down tomographic image based on a subtraction result of the subtraction unit.   
     
     
         38 . The imaging apparatus according to  claim 36 , further comprising:
 a variable transmittance material which is provided on a light path of the reference light and which is capable of changing a transmittance of the reference light,   wherein the tomographic image acquiring unit acquires the tomographic image in which information based on an intensity of the reference light after passing through the variable transmittance material is cut down from information of the tomographic image obtained based on the intensity of the combined light.   
     
     
         39 . The imaging apparatus according to  claim 38 , wherein the variable transmittance material is an ND filter. 
     
     
         40 . The imaging apparatus according to  claim 36 , wherein the controlling unit controls the first switching unit such that the first switching unit changes a light path of the measuring light to switch from the first state to the second state. 
     
     
         41 . The imaging apparatus according to  claim 40 , wherein the controlling unit controls the scanning unit such that the scanning unit can deviate a measuring light from the light path of the measuring light to switch from the first state to the second state. 
     
     
         42 . The imaging apparatus according to  claim 36 , wherein the first switching unit comprises a shutter which is provided on a light path of a measuring light and which is capable of shutting off the measuring light, and
 wherein the controlling unit controls the shutter such that the shutter shuts off the measuring light to switch from the first state to the second state.   
     
     
         43 . The imaging apparatus according to  claim 36 , further comprising:
 a second switching unit for switching, when the first switching unit switches to the state in which the detecting unit can detect the combined light, between the first state and a state in which the detecting unit can detect the returning light,   wherein the tomographic image acquiring unit acquires the tomographic image in which information based on an intensity of autocorrelation component of the reference light and information based on an intensity of autocorrelation component of the returning light are subtracted from information of the tomographic image obtained based on the intensity of the combined light.   
     
     
         44 . The imaging apparatus according to  claim 43 , wherein the second switching unit comprises a variable transmittance unit for changing a transmittance of the reference light, and
 wherein the controlling unit controls the variable transmittance unit such that the variable transmittance unit changes a transmittance of the reference light to switch from the first state i to the state in which the detecting unit can detect the returning light.   
     
     
         45 . The imaging apparatus according to  claim 44 , wherein the variable transmittance unit is an ND filter. 
     
     
         46 . The imaging apparatus according to  claim 37 , further comprising:
 a standardizing unit for standardizing the subtraction result by the information based on the intensity of autocorrelation component of the reference light; and   a transforming unit for Fourier-transforming a standardization result by the standardizing unit,   wherein the tomographic image acquiring unit acquires the cut down tomographic image based on a transforming result of the transforming unit.   
     
     
         47 . The imaging apparatus according to  claim 36 , further comprising:
 a light quantity detecting unit for detecting a quantity of a measuring light,   wherein the controlling unit controls the first switching unit such that the first switching unit switches, when the quantity of light detected by the light quantity detecting unit in the state in which the detecting unit can detect the combined light exceeds the predetermined value, from the first state to the second state.   
     
     
         48 . An imaging method for imaging a retina of an eye using a Fourier-domain optical coherence tomography, the imaging method comprising:
 scanning a measuring light on the retina, with a cornea of the eye as a fulcrum;   detecting, by using a detecting unit, one of (a) reference light and (b) combined light into which returning light obtained by radiating measuring light to the retina and reference light corresponding to a measuring light are combined;   determining whether or not a measuring light quantity is no more than a predetermined value;   switching, in a case where in the determining step it is determined that the measuring light quantity is no more than the predetermined value, to a first state in which the combined light can be detected from a second state in which the reference light can be detected; and   acquiring, after the detecting unit detects the combined light in the first state, a tomographic image in which information based on an intensity of the reference light is cut down from information of a tomographic image obtained based on an intensity of the combined light.   
     
     
         49 . The imaging method according to  claim 48 , further comprising:
 subtracting information based on an intensity of autocorrelation component of the reference light from the information of the tomographic image obtained based on the intensity of the combined light,   wherein the tomographic image acquiring acquires the cut down tomographic image based on a result of the subtraction.   
     
     
         50 . A non-transitory computer-readable storage medium storing a program for causing a computer to execute the imaging method according to  claim 48 . 
     
     
         51 . The imaging apparatus according to  claim 36 , wherein when the measuring light quantity exceeds the predetermined value, the controlling unit processes error handling. 
     
     
         52 . The imaging apparatus according to  claim 51 , wherein when the measuring light quantity exceeds the predetermined value, the controlling unit stops detection of light by the detecting unit as the processing of error handling. 
     
     
         53 . The imaging apparatus according to  claim 51 , wherein when the measuring light quantity exceeds the predetermined value, the controlling unit returns the scanning unit to an initial position as the processing of error handling. 
     
     
         54 . The imaging apparatus according to  claim 51 , wherein the first switching unit comprises a reference mirror located on a light path for the reference light, and
 wherein when the measuring light quantity exceeds the predetermined value, the controlling unit returns the reference mirror to an initial position as the processing of error handling.   
     
     
         55 . The imaging apparatus according to  claim 36 , wherein when the measuring light quantity exceeds the predetermined value, the controlling unit outputs an error message on a display unit. 
     
     
         56 . The imaging apparatus according to  claim 36 , wherein the controlling unit controls the first switching unit such that: when the measuring light quantity is within a predetermined range, the first switching unit switches from the second state to the first state, and when, in the state which the detecting unit can detect the combined light, the measuring light quantity is not within a predetermined range, the first switching unit switches from the first state to the second state. 
     
     
         57 . The imaging apparatus according to  claim 56 , wherein the predetermined range is 680 μW to 700 μW. 
     
     
         58 . The imaging apparatus according to  claim 36 , wherein the predetermined value is 700 μW. 
     
     
         59 . (canceled) 
     
     
         60 . The imaging apparatus according to  claim 47 , further comprising a splitting unit for splitting the measuring light into two lights,
 wherein the light quantity detecting unit detects a quantity of one of the lights as the quantity of the measuring light.   
     
     
         61 . The imaging method according to  claim 48 , further comprising switching, when the measuring light quantity exceeds the predetermined value, from the first state to the second state. 
     
     
         62 . The imaging method according to  claim 48 , further comprising processing and error handling when the measuring light quantity exceeds the predetermined value. 
     
     
         63 . The imaging method according to  claim 48 , further comprising outputting an error message on a display unit when the measuring light quantity exceeds the predetermined value. 
     
     
         64 . The imaging method according to  claim 48 , wherein the predetermined value is 700 μW. 
     
     
         65 . (canceled) 
     
     
         66 . A non-transitory computer-readable storage medium storing a program for causing a computer to execute the imaging method according to  claim 35 . 
     
     
         67 . A non-transitory program causing a computer to execute the imaging method according to  claim 35 . 
     
     
         68 . The imaging apparatus according to  claim 17 , wherein the first state, the second state, and a third state are switched such that the first state is followed by the second state and the third state. 
     
     
         69 . The imaging apparatus according to  claim 17 , wherein the first state, the second state, and a third state are switched such that the first state, the second state, and the third state are continuously and repeatedly changed. 
     
     
         70 . The imaging method according to  claim 26 , wherein the controlling unit is configured to control the first switching unit and the second switching unit such that the first state is followed by the second state and a third state. 
     
     
         71 . The imaging method according to  claim 26 , wherein the controlling unit is configured to control the first switching unit and the second switching unit so as to continuously and repeatedly change the first state, the second state, and a third state.