JP2006158547A - Spectrum ocular fundus image data measuring apparatus and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve positional deviation of the same section between respective spectrum images even in occurrence of change in the alignment of the eye and an apparatus due to time change. <P>SOLUTION: This spectrum ocular fundus image data measuring apparatus is provided with: an illumination optical system 10 for illuminating the ocular fundus F of the eye to be examined E; a light-receiving optical system 20 which receives a reflected beam from the illuminated eye fundus F for forming an eye fundus image on the light-receiving surface of an imaging part 4; and a data measurement part 7 which compares a plurality of pieces of ocular fundus image original data obtained at different times based on a signal from the light-receiving surface with each other and carries out positional correction of the image for generating a series of ocular fundus image data to which positional correction is carried out. In a desirable mode, the data measurement part 7 compares the pieces of ocular fundus image original data different for variation which is not larger than a threshold with each other and carries out the positional correction of the image for generating the series of spectrum ocular fundus image data in a prescribed wavelength range. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a spectral fundus image data measurement apparatus and measurement method. In particular, the present invention relates to a spectral fundus image data measuring apparatus and a measuring method for uniforming spectral characteristics in a predetermined wavelength range. The present invention also relates to a spectroscopic fundus image data measuring apparatus and a measuring method that perform high-precision matching between a large number of image data having different acquisition times over a predetermined wavelength range.

Needless to say, the importance of fundus observation in eye diagnosis is unquestionable. Currently, abnormal findings are found by diagnosing the fundus using color fundus images, fluorescence contrast images, etc. of the fundus camera. If the oxygen saturation at the fundus and the components of the substance distributed in the retina can be measured quantitatively by image analysis, the function of the retinal details can be understood, and it is thought that it will be very useful clinically. Further, if the spectral distribution of the substance in the retina is known by spectral analysis, there is a possibility that component analysis in the retina can be performed from the spectral image.

However, many studies that have been conducted so far cannot be said to be full-scale spectral image measurement. With full-scale image measurement, it is necessary to satisfy the requirements that (a) high-quality images can be obtained, and (b) spectral images can be measured over a wide wavelength band with high wavelength resolution. . Such an image measurement method is sometimes referred to as hyperspectral imaging. With the advent of liquid crystal wavelength tunable filters, spectral images can be acquired relatively easily. By using a large number of spectral images having different wavelengths, the spectral characteristics of the substance can be examined in detail, and components having various known spectral distributions can also be extracted.

Although full-scale measurement of living organisms is a topic for the future, as a measurement to confirm that this technology is compatible with human eye measurement, previous studies have been conducted with about 2 to 4 wavelengths using animals as models. Has been done. (For example, see Non-Patent Document 1)
Further, as an apparatus for acquiring a fundus spectral image that can be applied to the human eye, it has been studied to perform spectroscopy using a diffraction grating and scan the fundus to acquire a spectral image. (For example, see Patent Document 1)

Japanese translation of PCT publication No. 2002-507445 (paragraphs 0019 to 0053, FIGS. 1 to 9) “Hyperspectral Imaging for Measurement of Oxygen Saturation in the Optical Nerve Head”, Bahrham Khobehi, James M. Beach, and Hiroyuki Kawano1, Investigative Ophthalmology and Visual Science, Vol. 45, no. 5, p1464-1472, May 2004,

  Hyperspectral imaging is a notable technology that can also acquire spectroscopic images of the fundus, but the amount of light in the acquired spectroscopic image varies greatly for each wavelength, making accurate analysis difficult. It was. In addition, hyperspectral spectroscopy with a light quantity that can be applied without burden on humans has not been realized so far, and an apparatus capable of doing so has not yet been realized.

  Main spectroscopic devices include a diffraction grating, a prism, an etalon, and a filter. Conventionally, diffraction gratings and prisms were often used for variable wavelength spectroscopic measurement, but recently, a liquid crystal wavelength tunable filter has appeared, and spectral images can be taken at any wavelength, making it easy to perform spectroscopic image measurement. It became possible. Since the liquid crystal wavelength tunable filter is basically a plane-parallel plate, it can be easily incorporated into an optical system, and the optical performance can be easily maintained. For this reason, it is often used for spectral image acquisition using a microscope, and is also used in research for acquiring a spectral image and synthesizing it to create a natural image.

  However, it takes about 20 seconds to photograph every 10 nm from the wavelength range of 510 nm to 720 nm due to restrictions such as the wavelength variable time of the liquid crystal wavelength variable filter and the exposure time of the camera. During this time, since the alignment between the eye and the apparatus changes, there is a problem in that a positional shift occurs in the same imaged portion between the spectral images.

  An object of the present invention is to provide a spectral fundus image data measurement apparatus and measurement method capable of eliminating the positional shift of the same part between the respective spectral images even when the alignment of the eye and the apparatus changes due to a change in time.

  Furthermore, the present invention provides a spectral fundus image data measuring apparatus capable of correcting image positions almost automatically by a program using image correlation and automating comparison between spectral images and displaying spectral characteristics of feature points on the retina and An object is to provide a measurement method.

  In order to solve the above problem, a spectral fundus image data measuring apparatus 1 according to claim 1 includes an illumination optical system 10 that illuminates the fundus F of the eye E and an illuminated fundus as shown in FIG. The light receiving optical system 20 that receives the reflected light beam from F and forms a fundus image on the light receiving surface of the imaging unit 4 and a plurality of fundus image original data acquired at different times based on signals from the light receiving surface are compared and collated And a data measuring unit 7 that corrects the position of the image and generates a series of fundus image data corrected in position.

  Here, the light receiving surface is preferably a CCD, but may be a CMOS. If comprised in this way, the change of the alignment of the eye and apparatus by a time change will be correct | amended, and the position shift of the same site | part between each spectral image can be eliminated.

Further, in the spectral fundus image data measuring apparatus 1 according to claim 1, for example, as shown in FIG. 13, the position correction of the image is performed between a plurality of spectral fundus image original data. A feature point is selected and alignment is performed using correlation processing and affine transformation or Helmart transformation.
Here, the feature points may be linear. If comprised in this way, the correction | amendment of the change of the alignment of the eye and an apparatus by a time change can be performed with high precision. In addition, correction can be performed almost automatically by a program using image correlation.

Further, according to a third aspect of the present invention, in the spectral fundus image data measuring apparatus 1 according to the first or second aspect, for example, as shown in FIG. 1, the illumination optical system 10 has a luminous flux in a predetermined wavelength range. Illuminating light source 11, and disposed in either illumination optical system 10 or light receiving optical system 20, and equipped with a tunable filter 32 capable of selecting the wavelength of the transmitted light beam in a predetermined wavelength range, and performing data measurement The unit 7 acquires a plurality of original fundus image data by changing the wavelength of the transmitted light beam of the wavelength tunable filter 32.
If comprised in this way, the change of the alignment of the eye and apparatus by a time change will be correct | amended, and the position shift of the same site | part between each spectral image can be eliminated. Further, by using a wavelength tunable filter, a spectral image can be acquired at an arbitrary wavelength, and spectral image measurement can be performed for a fundus image. In addition, by adopting the spectral characteristic correction filter, it is easy for the subject's eyes and corrects the variation due to the frequency of the received light intensity to obtain good spectral characteristics.

Further, the invention according to claim 4 is arranged in either the illumination optical system 10 or the light receiving optical system 20 in the spectral fundus image data measuring apparatus 1 according to claim 3, for example as shown in FIG. A spectral characteristic correction filter 13 having a wavelength characteristic that corrects the wavelength characteristic of the luminous intensity of the illumination light source 11 and the transmission wavelength characteristic of the wavelength variable filter 32 and keeps the received light intensity on the light receiving surface within a predetermined range is provided.
If comprised in this way, by arrange | positioning a spectral characteristic correction filter in an illumination optical system, a to-be-examined eye can be illuminated with the light of a comparatively uniform and few light quantity, and a measurement kind to a subject's eyes can be performed. Further, by arranging the wavelength tunable filter in the light receiving optical system, it is possible to reduce the color change and the light quantity change of the light entering the eye.

Further, in the spectral fundus image data measuring apparatus 1 according to the third or fourth aspect, the change amount of the selected wavelength in the wavelength tunable filter 32 can be set to be equal to or less than the threshold value. The data measuring unit 7 corrects the position of the image while comparing and collating original fundus image data different in wavelength by a change amount equal to or less than a threshold value.
With this configuration, when the amount of wavelength change is small, the light intensity of the light fundus image original data is small, and the same part of the two fundus image original data can be easily associated with each other, so that position correction can be easily performed. Can do. Therefore, by limiting the amount of wavelength change as described above, position correction can be performed easily and with high accuracy, and by sequentially applying to a large number of images, a series of images where the image positions match with high accuracy. Fundus image data can be acquired.

According to a sixth aspect of the present invention, in the spectral fundus image data measuring apparatus 1 according to the fifth aspect, the predetermined wavelength range is 540 to 610 nm, and the amount of change below the threshold is 10 nm.
If comprised in this way, data useful for the spectroscopic analysis of the substance in a retina can be provided.

According to a seventh aspect of the present invention, in the spectral fundus image data measuring apparatus 1 according to any one of the third to sixth aspects, the wavelength variable filter 32 is a liquid crystal wavelength variable filter.
If comprised in this way, arbitrary wavelengths can be easily selected in visible region using a liquid crystal wavelength variable filter.

The invention according to claim 8 is the spectral fundus image data measurement apparatus 1 according to any one of claims 2 to 7, wherein the data measurement unit 7 is configured such that the blood vessel portion is long on the short wavelength side. On the wavelength side, the choroidal blood vessel portion is selected as the feature point, and the position of the image is corrected.
If comprised in this way, the feature point used as the reference | standard of position correction can be discriminate | determined comparatively easily, and a highly accurate position correction will be attained.

The invention according to claim 9 is the spectral fundus image data measuring apparatus 1 according to any one of claims 3 to 8, wherein the data measuring unit 7 includes the received light intensity and optical density of arteries and veins. (Optical Density is also referred to as OD in this specification).
If comprised in this way, data useful for the spectroscopic analysis of the substance in a retina can be provided via OD data.

According to a tenth aspect of the present invention, in the spectroscopic fundus image data measurement apparatus 1 according to the ninth aspect, the data measurement unit 7 performs correction based on the diameter of the blood vessel at the site where the strength of the artery and vein is calculated. Calculate the OD at each position on the retina, perform factor analysis of OD at each position based on the spectral distribution of OD of arteries and veins, calculate the ratio of oxyhemoglobin at each position, and calculate the ratio of oxyhemoglobin To map.
With this configuration, it becomes possible to automate the analysis of the oxygen saturation.

  In order to solve the above-mentioned problem, a spectral fundus image data measurement method according to an eleventh aspect of the present invention includes, as shown in FIG. 10, for example, an animal subject by a light beam from an illumination light source 11 that emits a light beam in a predetermined wavelength range. A step of illuminating the fundus F of the optometry E (S001), a step of receiving a reflected light beam from the fundus F and forming a fundus image of the animal on the light receiving surface of the imaging unit 4 (S002), and a predetermined wavelength range A liquid crystal wavelength tunable filter 32 capable of selecting the wavelength of the transmitted light beam is arranged in either the illumination optical system 10 or the light receiving optical system 20, and the signal from the light receiving surface is changed by changing the wavelength of the transmitted light beam of the liquid crystal wavelength tunable filter 32. Step (S003) for acquiring spectral fundus image original data based on the above, and in the data measurement unit 7, the spectral fundus image original data different in wavelength by a change amount equal to or less than a threshold value are compared and collated to perform image position correction. And a step (S004) for generating a sequence of spectral fundus image data in the wavelength range of the constant.

  If comprised in this way, the change of the alignment of the eye and apparatus by a time change will be correct | amended, and the position shift of the same site | part between each spectral image can be eliminated. Further, by using the liquid crystal wavelength tunable filter, a spectral image can be acquired at an arbitrary wavelength, and spectral image measurement can be performed for a fundus image. In addition, by adopting the spectral characteristic correction filter, it is easy for the subject's eyes and corrects the variation due to the frequency of the received light intensity to obtain good spectral characteristics.

  According to a twelfth aspect of the present invention, in the spectral fundus image data measuring method according to the eleventh aspect, when the position correction of the image is performed, the original data having the lowest wavelength among the spectral fundus image original data is used as the reference image. , Position correction is performed using the original data with the second lowest wavelength as the pre-correction image, and then the position correction is performed with the corrected pre-correction image as the new reference image and the original data with the third lowest wavelength as the pre-correction image. In the following, position correction is performed sequentially from the lower wavelength to the higher wavelength, or the original data with the highest wavelength among the spectral fundus image original data is used as the reference image and the original data with the second highest wavelength. Is then corrected using the corrected pre-correction image as the new reference image and the original data with the third highest wavelength as the pre-correction image. Or Performing sequential position corrected to lower wavelengths.

Here, with reference to an image near the median value of the measurement wavelength range, position correction is performed using the next highest wavelength original data as an uncorrected image, and then the corrected uncorrected image is used as a new reference image. , Position correction is performed using the original data with the next highest wavelength as the pre-correction image.Hereafter, position correction is performed sequentially from the lower wavelength to the higher wavelength. Using the image near the median as a reference, position correction is performed using the original data with the next lowest wavelength as the pre-correction image, and then the corrected pre-correction image is used as a new reference image, and the wavelength is the next lowest. In the case where the position correction is performed using the original data as the pre-correction image, and the position correction is performed sequentially from the higher wavelength to the lower wavelength, the above method is performed separately for two wavelength ranges. The same applies to the case where the position correction is performed sequentially from the wavelength near the median to the higher wavelength first, and the position correction is performed sequentially from the wavelength near the median to the higher wavelength.
With this configuration, when the amount of wavelength change is small, the light intensity of the light fundus image original data is small, and the same part of the two fundus image original data can be easily associated with each other, so that position correction can be easily performed. Can do. Therefore, a series of fundus image data in which the image positions match with high accuracy can be acquired by reducing the wavelength change amount and sequentially performing position correction.

The invention according to claim 13 is the spectral fundus image data measurement method according to claim 11 or claim 12, wherein, for example, as shown in FIG. 18, the predetermined wavelength range is 540 to 610 nm, and the liquid crystal wavelength tunable filter is used. Spectral fundus image original data image is acquired by setting the change amount of the selected wavelength in 32 to 10 nm (S502), and the position correction of the image is performed between the spectral fundus image original data different in the change amount of the wavelength equal to or less than the threshold value. A point is selected and alignment is performed using correlation processing and affine transformation or Helmat transformation (S503), and arteries and veins are selected as feature points, and the received light intensity and OD of the arteries and veins are calculated (S505). Correction is performed based on the diameter of the blood vessel at the site where the strength of the artery and vein is calculated (S506), and the OD at each position on the retina is calculated (S507). Factor analysis of OD at each position on the retina is performed based on the light distribution (S508), the ratio of oxyhemoglobin at each position on the retina is calculated, and the ratio of oxyhemoglobin in the spectral fundus image is mapped ( S509).
If comprised in this way, data useful for the spectroscopic analysis of the substance in a retina can be provided, and the analysis of oxygen saturation can be automated.

  According to the present invention, it is possible to provide a spectral fundus image data measurement device and a measurement method that can correct a change in alignment between the eye and the device due to a change in time and eliminate a positional shift of the same part between the spectral images.

  Furthermore, according to the present invention, spectral fundus image data measurement can be performed almost completely automatically by a program using image correlation, and comparison between spectral images and display of spectral characteristics of feature points on the retina can be automated. An apparatus and a measurement method can be provided.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 shows a schematic example of an optical system of a spectral fundus image data measuring apparatus 1 according to an embodiment of the present invention. In the figure, the spectral fundus image data measuring device 1 is roughly divided into a fundus camera unit 2, a top housing unit 3, a data measuring unit 7, and a control unit 8. The fundus camera unit 2 is a front stage of an illumination optical system 10 for illuminating the fundus F of the eye E to be examined, and a light receiving optical system 20 that receives a reflected light beam from the fundus F and forms a fundus image on the light receiving surface of the imaging unit 4. And a viewfinder optical system 60 for observing the fundus F by the examiner. The top housing unit 3 includes an imaging unit 4 that captures a spectral fundus image, an alignment optical system 50 for aligning the irradiation position of the irradiation light onto the fundus F (the light source 51 is provided in the fundus camera unit 2), and The relay optical system 5 that tunes the reflected light beam received from the fundus camera unit 2 and guides it to the camera relay unit 6, and the camera relay that transmits the reflected light beam after passing through the relay optical system 5 to various light receiving means such as the imaging unit 4. And a rear stage portion of the light receiving optical system 20 extending from the relay optical system 5, the camera relay unit 6, and the imaging unit 4. An extension unit 9 at the top of the camera relay unit 6 is a part that can be used in an expanded manner by connecting various light receiving means such as a monitor TV and a hard copy to the light receiving optical system 20.

  In the fundus camera unit 2, the illumination optical system 10 includes a halogen lamp 11 as an illumination light source, a condenser lens 12, a spectral characteristic correction filter 13, a diaphragm plate 14, a reflector 15, a relay lens 16, and a beam splitter 41 on the irradiation optical axis. Are arranged sequentially. Here, the halogen lamp 11 emits a light beam in a wide wavelength range and is disposed near the front focal position of the condenser lens 12. The diaphragm plate 14 is arranged so as to be conjugate with the beam splitter 41.

The illumination optical system 10 further illuminates the fundus F of the eye E through the objective lens 42 with the reflected light beam from the beam splitter 41. A common optical system 40 of the illumination optical system 10 and the light receiving optical system 20 is formed between the beam splitter 41 and the eye E to be examined.
The light receiving optical system 20 includes an objective lens 42, a beam splitter 41, an iris diaphragm plate 21, a focusing lens 22, an imaging lens 23, and a reflecting mirror 24 on the reflection optical axis passing through the eye E within the fundus camera unit 2. The switching mirror 25 is sequentially arranged and connected to the light receiving optical system of the top housing portion 3. The iris diaphragm plate 21 is disposed at a position conjugate with the anterior segment of the eye E. When acquiring the spectral image, the switching mirror 25 is removed from the optical path like a solenoid, for example.

  The alignment optical system 50 is for aligning the irradiation position of the irradiation light onto the fundus F, and includes a dichroic mirror 52, an imaging lens 53, and a monitor camera 54, and includes an alignment light source 51 (on the fundus camera unit 2). See the reflected light when the light from (provided) is projected onto the eye. By setting the wavelength of the alignment light source 51 to near infrared (for example, 940 nm), alignment can be performed even during acquisition of a spectral image without affecting the spectral image in the visible region. The dichroic mirror 52 transmits visible light (for example, 750 nm or less) and reflects the long wavelength side. By using the dichroic mirror 52 as a switching mirror and removing it from the optical path, for example, as a solenoid, except for when a spectral image is acquired, color fundus observation can be performed at the extended portion. As the monitor camera 54, for example, a CCD camera can be used. The viewfinder optical system 60 is used by the eye examiner to observe the fundus F with the naked eye.

  In the top housing portion 3, the light receiving optical system 20 has the relay optical system 5 disposed on the reflection optical axis from the eye E, and a reflected light beam is introduced from the fundus F into the camera relay portion 6 by the relay optical system 5. In the camera relay unit 6, a dichroic mirror 31 is disposed on the reflection optical axis, and the dichroic mirror 31 reflects visible light (for example, 750 nm or less) and transmits the long wavelength side. The reflected light beam from the dichroic mirror 31 is guided to the imaging unit 4. In the imaging unit 4, a liquid crystal wavelength tunable filter 32, an imaging lens 33, and a CCD camera 34 having a light receiving surface are arranged on the reflected optical axis from the dichroic mirror 31. In addition, the light receiving surface is disposed so as to be conjugate with the fundus F of the eye E so that a fundus image is formed. The imaging lens 33 is a lens for relaying light emitted from the liquid crystal wavelength tunable filter 32 to the CCD camera. If the liquid crystal wavelength tunable filter 32 is used, an arbitrary wavelength can be easily selected in the visible light region, so that the spectral characteristics can be easily analyzed.

  The data measurement unit 7 includes a data acquisition unit 71 that acquires spectral fundus image data based on a signal from the light receiving surface of the CCD camera 34, an image correction unit 72 that performs image alignment, and an image analysis unit that performs spectral retinal image analysis. 73, a map creation unit 74 that maps the ratio of oxyhemoglobin and the like, and stores programs for an image alignment flow and a spectral retinal image analysis flow. The image analysis unit 73 performs correction based on the blood vessel diameter of the site where the strength of the artery and vein is calculated, calculates the OD at each position on the retina, and based on the spectral distribution of the OD of the artery and vein on the retina Factor analysis of OD at each position is performed, and the ratio of oxyhemoglobin at each position on the retina is calculated.

  In order to measure spectral fundus image data, the control unit 8 controls the entire spectral fundus image data measurement apparatus 1, such as the operation of the fundus camera unit 2, the top housing unit 3, and the data measurement unit 7 and the flow of data and signals. . Further, it has an exposure control unit 81 for controlling the exposure of the CCD camera and a wavelength control unit 82 for controlling the wavelength of the liquid crystal wavelength tunable filter and the like, and stores programs for the spectral fundus image acquisition flow and the CCD camera exposure time setting flow. The control unit 8 can be realized by a normal personal computer.

  Next, spectral characteristics of the optical system of the spectral fundus image data measurement apparatus according to the present embodiment will be described. For analysis of spectral characteristics, a wavelength region of 430 to 950 nm is mainly used, and spectral characteristics that are as uniform as possible within this range are desired. Factors that greatly affect the spectral characteristics are considered to be the CCD camera 34, the liquid crystal wavelength tunable filter 32, and the halogen lamp 11. The spectral characteristics of each device will be described below.

  A dispersive spectroscopic method was adopted as the spectroscopic method. As a spectral system other than the dispersion type, the Fourier spectroscopic type can be mentioned. However, the Fourier spectroscopic type using the interference method is concerned with the noise of the image of the retina, and the dispersive spectroscopic method is adopted. The Fourier spectroscopic type is capable of instantaneous spectroscopy and may be advantageous in terms of the amount of light.

  The use of a halogen lamp as the illumination light source 11 emits light in a wide wavelength range including the visible light region to the near infrared region, and continuous lighting for about 10 seconds is necessary to perform spectroscopy in time series. This is because an image can be acquired without using a flash due to the advance of CCD.

  FIG. 2 shows an example of spectral characteristics of a halogen lamp as the illumination light source 11. The horizontal axis represents wavelength (μm), and the vertical axis represents relative intensity (%). The spectral characteristics at a color temperature of 2200 to 3400 ° K. are shown with the maximum intensity at 3000 ° K being 100%. From the figure, the irradiation light of the halogen lamp continuously covers the wavelength range from the visible light to the infrared region, which is useful for spectroscopic analysis, and the intensity of the illumination light source 11 increases monotonously with the increase of the wavelength in the visible light region. is doing.

  FIG. 3 shows an example of the spectral sensitivity characteristic of the CCD camera 34. The horizontal axis represents wavelength (nm) and the vertical axis represents quantum efficiency (%). The CCD camera 34 is sensitive to a wide range of wavelengths from visible light to the near infrared region. For example, a high-definition image of 1.3 million pixels (1344 × 1024) can be obtained, and high-speed (about 8 frames / second) and low-noise readout are possible. Is possible. There is a substantially uniform sensitivity peak at 450 to 600 nm, and the sensitivity decreases on both sides.

  FIG. 4 shows an example of bandpass characteristics of the liquid crystal wavelength tunable filter 32. The horizontal axis represents wavelength (nm), and the vertical axis represents transmittance (%). The liquid crystal wavelength tunable filter 32 can select the transmission wavelength in the range of 400 to 720 nm by changing the voltage applied to the liquid crystal. The figure shows how the transmitted light changes when the transmission center wavelength is changed by 10 nm. The wavelength width of the transmitted light is about 20 nm, and the peak value of the amount of transmitted light increases almost monotonously with the increase in wavelength.

  FIG. 5 shows a configuration example of the liquid crystal wavelength tunable filter 32. The liquid crystal wavelength tunable filter selects a wavelength by combining several stages of liquid crystal tunable filters (LCTF: Liquid Crystal Tunable Filter). As shown in FIG. 5, one LCTF is configured by sandwiching a fixed wavelength plate and a liquid crystal variable wavelength plate with a polarizing plate, and the angle between the fixed wavelength plate and the polarizing plate of the liquid crystal variable wavelength plate is an ordinary ray and an extraordinary ray generated. The optical path length difference is fixed at 45 degrees so that it can be controlled by the liquid crystal variable wavelength plate.

When the thickness of one wave plate is d, the optical path length difference R between the ordinary ray and the extraordinary ray is expressed by (Equation 1).

n (e) is the refractive index for ordinary light, and n (o) is the refractive index for extraordinary light. The optical path length difference R is changed by combining the fixed wavelength plate and the liquid crystal variable wavelength plate and changing the voltage applied to the liquid crystal variable wavelength plate. Light having an optical path length difference R is extracted by a polarizing plate in the direction of 45 degrees to form an interference filter.
The overall transmittance T is as shown in (Equation 2), where the wavelength is λ, and varies with the optical path length difference R.

FIG. 6 shows an example of the wavelength selection method of the liquid crystal wavelength tunable filter 32. In order to reduce the wavelength width to be output, a combination of wave plates having different thicknesses are stacked in several stages (six stages in the example in the figure) to realize a wavelength width of 20 nm. FIG. 6A shows the filter characteristics of each of the six stages of LCTFs. FIG. 6B shows the filter characteristics of the liquid crystal wavelength tunable filter 32 in which six stages of LCTFs are superimposed. By changing the voltage applied to the liquid crystal variable wavelength plate of each LCTF, the transmission center wavelength can be arbitrarily changed at high speed, and light having an arbitrary wavelength component can be extracted.
Since the liquid crystal wavelength tunable filter 32 is affected by the polarization direction of the incident light, when using polarized light, alignment corresponding to the polarization angle of the incident light is necessary. Even in this case, the light emitted from the liquid crystal wavelength tunable filter 32 is maintained in the same polarization direction as the incident light.

  FIG. 7 shows an example of spectral characteristics taking into account the spectral characteristics of the halogen lamp 11, the liquid crystal wavelength tunable filter 32, and the CCD camera 34. The horizontal axis represents wavelength (nm), and the vertical axis represents relative intensity (the intensity of light having a wavelength of 700 nm is 1). It can be seen that the relative intensity increases almost monotonically in the range of 450 to 700 nm. As described above, the total characteristic of each optical component has a low light amount on the short wavelength side and abruptly increases as the wavelength becomes longer, so a spectral characteristic correction filter 13 that cancels this is required.

  FIG. 8 shows an example of spectral characteristics of the spectral characteristic correction filter 13. The horizontal axis represents wavelength (nm), and the vertical axis represents transmittance (%). In the present embodiment, a filter having a transmission center wavelength of about 460 nm is selected in order to perform correction at 450 to 700 nm.

  FIG. 9 shows an example of spectral characteristics of an optical system in which the spectral characteristic correction filter 13 is inserted. The horizontal axis indicates the wavelength (nm), and the vertical axis indicates the maximum intensity acquired at 34 by the CCD camera. In this example, the maximum value is 12 bits 4096. The data is obtained by obtaining a spectral image of a standard white plate and normal eyes with a constant exposure time (for example, 200 ms) after the spectral characteristic correction filter 13 is inserted, and measuring the maximum intensity. ◆ indicates the maximum intensity of reflected light from normal eyes, and ■ indicates the maximum intensity of reflected light from a standard white plate. Prior to correction, it was impossible to acquire a spectral image with the same light amount and the same wavelength band. Although the standard white plate has a difference between the minimum value of 829 and the maximum value of 3532, it was confirmed that images could be acquired without causing saturation with the same amount of illumination. With normal eyes, a flattened image with minimum value 416 and maximum value 2217 could be obtained. Such a difference in the amount of light is sufficiently within the dynamic range of the CCD, facilitating imaging with a CCD camera, and automating exposure.

  FIG. 10 shows an example of the flow of the spectral fundus image data measurement method according to the embodiment of the present invention. First, the fundus F of a human or animal eye E is illuminated with a light beam from an illumination light source 11 that emits a light beam in a predetermined wavelength range (step S001). Next, the reflected light beam from the fundus F is received on the light receiving surface of the imaging unit 4 to form a fundus image of a human or an animal (step S002). Next, using the liquid crystal wavelength tunable filter 32 capable of selecting the wavelength of the transmitted light beam within a predetermined wavelength range, the wavelength of the transmitted light beam of the liquid crystal wavelength tunable filter 32 is changed, and the spectral fundus image source is based on the signal from the light receiving surface. Data is acquired (step S003). Next, in the data measuring unit 7, the spectral fundus image original data different in wavelength by a change amount equal to or less than a threshold value are compared and collated, the position of the image is corrected, and this is sequentially accumulated to obtain a series of a predetermined wavelength range. Spectral fundus image data is generated (step S004). Since the amount of change in wavelength is small, the change in luminous intensity between the light fundus image original data is small, and the correspondence between the same portions of the two fundus image original data can be easily obtained, so that the position correction can be easily performed. Therefore, by limiting the amount of wavelength change as described above, position correction can be performed easily and with high accuracy, and by sequentially applying to a large number of images, a series of images where the image positions match with high accuracy. Fundus image data can be acquired.

  FIG. 11 shows an example of a spectral fundus image acquisition flow. This corresponds to step S003 in FIG. First, an initial wavelength λs, a final wavelength λe, and a wavelength interval (amount of change in wavelength) λd to be changed at one time are set (step S101). Next, the fundus camera unit 2 and the eye E to be examined are aligned (step S102). Next, the measurement wavelength λ is set to the initial wavelength λs (step S103), the transmission wavelength of the liquid crystal wavelength tunable filter 32 is adjusted to be the measurement wavelength λ (step S104), and the exposure time of the CCD camera 34 is measured. A predetermined value predetermined for each wavelength λ is automatically set (step S105), and a spectral fundus image is acquired by performing automatic exposure with the set exposure time (step S106). If the measurement wavelength λ is equal to or less than the final wavelength λe (NO in step S107), the wavelength interval λd is added to the measurement wavelength λ (step S108), the set wavelength is changed (step S104), and exposure and image acquisition are repeated. . If the measurement wavelength λ is greater than the final wavelength λe (YES in step S107), the acquired fundus image is stored (step S109). In this spectral fundus image acquisition flow, program control including loop processing is possible except for eye alignment (step S002). The program is stored in the control unit 8, the exposure control unit 81 controls the exposure of the CCD camera 34, the wavelength control unit 82 controls the wavelength of the liquid crystal wavelength tunable filter 32, and the control unit 8 controls the data acquisition unit 71. To control data acquisition.

FIG. 12 shows an example of a CCD camera exposure time setting flow. This corresponds to step S105 in FIG. The spectral characteristic flattened by inserting the spectral characteristic correction filter 13 is further supplemented by correcting the exposure time of the CCD camera 34. First, the number of data av to be averaged is arbitrarily set (for example, 5) (step S201), and the allowable maximum luminance value range (maximum allowable value _Ihigh , minimum allowable value _Ilow ) is set (step S202). ). Next, the exposure time _Tex is set to an arbitrary value (step S203), and a spectral fundus image is acquired (step S204). With respect to the obtained spectral fundus image, the luminance value I _k of each pixel of the CCD (the CCD element number is k and the number of elements is k _max ) is obtained (step S205), and av (set) are set in order of the luminance value I _k. The total number M _ALL of these luminance values I _k is obtained (step S206), and the maximum luminance average value M (= M _ALL / av) is calculated (step S207).

If this maximum luminance average value M is larger than the maximum allowable value I _high (YES in step S208), the exposure time is shortened (in this example, 1/2) (step S211), and if it is smaller than the minimum allowable value I _low (YES in step S209) The exposure time is lengthened. If the predetermined value _{I -low} smaller than the two stages in this example (in step S210 NO) exposure time to alpha times (e.g. alpha = 1.2) (step S012), if greater than the predetermined value _{I -low} ( In step S210 YES, the exposure time is doubled (step S213), and the process returns to image acquisition (step S204) again. When the maximum average brightness value M falls within the set range (NO in steps S208 and S209), the exposure time is set appropriately and the exposure time is set to _Tex at that time. A spectral fundus image is acquired (step S204).

For the newly acquired spectral fundus image, as long as the maximum luminance average value M continues to be within the set range (NO in steps S208 and S209), the exposure time set value _Tex is maintained and set when it goes out of range. The value is updated. In fact, when obtaining a spectral fundus image, if the wavelength is acquired sequentially from the shorter wavelength, the change in the spectral fundus image is small, so the exposure time is not updated frequently in the above routine, and is executed efficiently. A good image can be obtained in a short time. By using this CCD camera exposure time setting flow, an image having excellent spectral characteristics can be acquired, and by using the CCD camera in combination with the spectral characteristic correction filter 13, the spectral characteristics can be further improved. The CCD camera exposure time setting flow can be controlled by a program including loop processing. The program is stored in the control unit 8, and the exposure control unit 81 controls the exposure of the CCD camera 34.

  FIG. 13 shows an example of a spectral retinal image alignment flow. This corresponds to step S004 in FIG. Spectral retinal image acquisition currently takes about 20 seconds for imaging every 10 nm from 510 nm to 720 nm due to the wavelength variable time of the liquid crystal variable filter 32 and the exposure time of the CCD camera 34. During this time, misalignment, fixation disparity, etc. between the eye E and the fundus camera unit 10 occur, and the position of the acquired retinal image shifts, and the position on the retina corresponding to the same coordinates on the light receiving surface of the CCD camera 34. Are often different. Therefore, when the oxygen saturation analysis is performed, it is necessary to correct this positional shift, and the correction is performed by image processing in the data measurement unit 7. In addition, the spectral image of the retina changes according to the change of the wavelength, and when the change of the wavelength becomes large, the change of the spectral image can be recognized even by appearance. For this reason, it becomes difficult to take correspondence of the same part on a retina image between distant wavelengths. Therefore, in the present embodiment, the first shortest-wavelength image and the second short-wavelength image acquired are aligned first, and then the second image from the short-wavelength side used for the current alignment and 3 In other words, alignment of the second image is performed by a combination of shiritori formulas, and alignment error correction is performed to reduce errors. This image alignment is performed by the image correction unit 72 of the data measurement unit 7.

First, fundus image original data having an acquisition start wavelength (shortest wavelength) λ ₀ is read and used as a reference image (step S301). Next, the image alignment number n is set to 1 (step S302). The fundus image original data to be aligned (the image with the short wavelength next to the reference image and called the image with the acquisition wavelength λn) is read and used as an uncorrected image (step S303). Next, image alignment between the reference image and the pre-correction image is performed, and the pre-correction image obtained by aligning the image and correcting the position is set as a new reference image (step S304). If an uncorrected image remains (NO in step S305), n is incremented (step S306), the fundus image original data of the next acquisition wavelength λn is read (step S303), and all fundus image original data is read. The image alignment is repeated until correction is performed (YES in step S305). In this flow, the fundus image original data may be read by rereading the data already read from the CCD camera 34 into the data acquisition unit 71 by the data measurement unit 7 into the image correction unit 72. This spectral retinal image alignment flow can be controlled by a program including loop processing. The program is stored in the data measuring unit 7, and image processing such as image alignment is executed by the image correcting unit 72.

  FIG. 14 shows an example of an image alignment flow. This mainly corresponds to step S304 in FIG. Two pieces of spectral fundus image original data (reference image and uncorrected image) of the illuminated fundus acquired at different times based on signals from the light receiving surface of the imaging unit 4 are read (step S401) (steps S301 to S301 in FIG. 13). This corresponds to S303, and the steps after Step S402 correspond to Step S304 in FIG. 13). Next, a plurality of feature points (points that have features and high discriminability, may be linear) are selected from two images as matching points for image matching (step S402). Next, the position of the corresponding matching point is searched (step S403). For the search, for example, a least square method (LSM: Least Squares Matching) is used.

  The least square method is a method in which the position and shape of the template are fixed, and matching is performed by changing the position and shape of the matching window so that the difference in shading between the matching window and the template is minimized. is there. In order to change the position and shape of the matching window, an affine transformation or a Helmat transformation can be selected. For these, the conversion coefficient is changed to calculate the difference in shading to obtain the most appropriate coefficient (step S404). Next, the pre-correction image is converted using the obtained conversion coefficient (step S405). In this case, a linear interpolation method or a bicubic interpolation method can be selected.

  The bicubic method (bicubic method) is an image interpolation method called a cubic interpolation method. In general scanners, there are many models that use the linear interpolation method (calculated by referring to pixels on a straight line passing through two points) and the nearest neighbor method (nearest neighbor method), but the bicubic method uses information. Loss is the least, and a smooth and natural image can be obtained in a photo. However, it takes a long time to perform a complicated operation. In addition, the linear interpolation method is a method in which the value is determined from only the surrounding four pixels while the nearest neighbor method determines the value from only one surrounding pixel. Interpolation accuracy is high.

  Next, the converted pre-correction image is stored in a file (step S406). The stored image is used for the next image alignment as a new reference image. For example, a BMP format or a JPG format can be used as the storage format, and it may be output as raw data.

FIG. 15 is a diagram for explaining the least square matching. First, a template is created from the reference image, and the initial position of the matching window is determined from the search image. It is assumed that the reference image template is t _ij , the search image matching window is m _ij , and the converted matching window is m _ij (x, y).

The residual F _ij (a1 to a6) represents the difference in gray value between the template t _ij in FIG. 15 and the matching window m _ij (x, y) after geometric transformation. In order to minimize the residual, the matching window _mij is transformed. The deformation must be performed in consideration of the projection method. Here, for example, the deformation is performed by affine transformation (Equation 4), and the affine coefficients a1 to a6 of the matching window for the template are obtained.

First, linearization of (Equation 3) is performed.
Derivatives (partial differential coefficients) for each variable are as shown below.

  Using (Equation 7) as an observation equation, the matching window is converted to reconstruct the image. The convergence calculation and image reconstruction are repeated until the convergence criterion is reached. That is, the calculation is repeated so that Δa1 to Δa6 are minimized. Here, the affine coefficients to be actually obtained are a1 to a6, but the obtained coefficients are Δa1 to Δa6. Therefore, Δa1 to Δa6 are added to the initial values of a1 to a6 to obtain affine coefficients a1 to a6. The position satisfying the convergence criterion is set as the final matching window position. When the position of the matching window is determined for the search image, the corresponding points between the images can be evaluated.

  Next, an example in which the spectral fundus image data measurement method according to the present embodiment is applied to spectral retinal image analysis will be described. First, as an assumption, the influence of oxidized and reduced hemoglobin on spectral fundus image data will be described.

FIG. 16 shows an example of the amount of light absorbed by oxidized and reduced hemoglobin (unit: cm ⁻¹ / moles / liter). FIG. 16A shows the amount of absorbed light in the visible region, and FIG. 16B shows the amount of absorbed light in the near infrared region. Oxygenated hemoglobin is indicated by HbO ₂ , and reduced hemoglobin is indicated by Hb. The retina oxygen saturation analysis utilizes the fact that there is a difference in the amount of absorbed light for each wavelength of oxidized / reduced hemoglobin. By analyzing how much this spectral characteristic pattern is included in the spectral characteristics at each measurement target site, the ratio of the oxidized / reduced hemoglobin contained in the target measurement site can be determined. There is a possibility that oxygen saturation can be obtained from This time, a wavelength region having a large difference in the amount of absorption of oxidized / reduced hemoglobin at 540 to 610 nm was used.

  Various components other than hemoglobin are contained on the fundus and each has different spectral characteristics. The spectroscopic fundus image is thought to have these effects, but this time a very simplified algorithm was adopted and the analysis was performed assuming that there was only the effect of oxidized / reduced hemoglobin.

Next, spectral retinal image analysis will be described.
As the eye E to be examined, (A) normal eye and (B) diseased eye (Branch retinal vein occlusion (BRVO)) were selected as measurement targets.

FIG. 17 shows an example of a spectral retinal image analysis flow. The analysis flow algorithm is as follows.
(A) The eye E and the fundus camera unit 2 are aligned. The alignment light is turned on, and alignment (positioning) is performed while viewing the image acquired by the CCD camera 54 (corresponding to step S501 and step S102 in FIG. 11).
(B) A spectral image is acquired. Focus adjustment is performed, and spectroscopic fundus images are sequentially acquired from the shorter 10 nm wavelength from 540 nm to 610 nm (corresponding to step S502 and step S106 in FIG. 11).
(C) From the acquired image, an image with the shortest wavelength is set as a reference image, an image with the next shortest wavelength is set as an uncorrected image, affine transformation is performed on the image before correction, and distortion of the image is corrected according to the reference image. The converted pre-correction image is used as a new reference image, and the next shortest wavelength image is used as the pre-correction image, and correction is performed sequentially for each wavelength image (corresponding to step S503 and steps S301 to S306 in FIG. 13).

(D) Average intensity of arteries, veins and background at wavelength λ
Is calculated (step S504).

(E) The optical density (( _ODartery ) ′ _λ , ( _ODvein ) ′ _λ ) of the artery and vein at the wavelength λ is calculated (step S505).

(F) The thickness of the artery and vein ( _tartery , _tvein ) at the position where the average intensity is measured is measured, and the optical density of the artery and vein (( _ODartery ) _λ , ( _ODvein ) _λ ) is corrected ( Step S506).

(G) The local intensity corresponding to each coordinate (x, y) such as a feature point on the retina is measured, and the optical density ((OD _{x, y} ) of the artery and vein at each position ( _{x, y} ) _λ ) is calculated (step S507).

(H) The optical density of the artery and vein at each position (x, y) on the retina ((OD) with the optical density of the artery and vein (( _ODartery ) _λ , ( _ODvein ) _λ ) at the _{wavelength λ} as an element. A factor analysis of _{x, y} ) _λ ) is performed (step S508).
(I) The ratio of arterial blood at each position (x, y) on the retina is calculated, and the ratio of oxyhemoglobin is converted into a color code map (step S509).

In the above, when calculating the optical density OD, the ratio of the average intensity of the arteries and veins and the average intensity of the background is taken and the logarithm is taken or minus, or the ratio of the average intensity of each position and the average intensity of the background , Taking the logarithm and multiplying by minus, using absorbance density (AD) instead of OD, subtracting the average intensity of the background from the average intensity of the arteries and veins, and taking that value as the average intensity of the background Or the average intensity of each position is subtracted from the average intensity of the background, and the value divided by the average intensity of the background may be used. Here, the absorbance density (AD) at an arbitrary point is expressed by Equation 11.

  This spectral retinal image analysis flow can be controlled by a program. The program is stored in the data measurement unit 7, the image analysis unit 73 performs image analysis, and the map creation unit 74 maps the ratio of oxyhemoglobin.

FIG. 18 shows an example of a spectral retinal image obtained by normal eyes.
FIG. 19 shows an example of the acquired spectral retinal image of the BRVO eye.
The images in FIGS. 18 and 19 are acquired images before correction by image alignment. The nipple, blood vessels (arteries, veins), affected area, etc. are photographed so that they can be distinguished. In the figure, the nipple is a bright small circular portion, and the blood vessel is a dark linear portion. Since these images did not use a flash light source, they could be taken with a smaller amount of light than normal fundus camera measurements. When measuring by changing the wavelength range of 510 to 720 nm by 10 nm, it takes a long measurement time of about 20 seconds. However, since a spectral characteristic correction filter is included, the amount of light incident on the eye to be examined is small, The burden on the examiner is not very large. Thus, according to the present embodiment, it is possible to stably acquire a spectral image.

  FIG. 20 shows an example of a color code map of a fundus photograph. FIG. 20A is a color code map representing the oxygen saturation analysis result for normal eyes. FIG. 20B is a color code map representing the oxygen saturation analysis result for the BRVO eye. The map is saturated with oxygen as it becomes lighter. In the BRVO eye, a region not saturated with oxygen spreads in the lower part, which matches the diagnosis result. In the normal eye, a region not saturated with oxygen extends from the fovea to the right, indicating that this region is activated.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made to the embodiments without departing from the spirit of the present invention. It is.

  For example, the configuration of the optical system is not limited to the present embodiment, and includes an illumination optical system that includes an illumination light source that emits a light beam in a predetermined wavelength range, and that illuminates the fundus of the eye to be examined with the light beam from the illumination light source. If a light receiving optical system that receives a reflected light beam from the illuminated fundus and forms a fundus image on the light receiving surface of the imaging unit is provided, the light source, imaging means, and optical path can be arbitrarily selected. In addition, the optical system may include a fixation system that projects a fixation target on the fundus, a compensation optical unit that compensates for the aberration of the irradiation light may be inserted into the illumination optical system, and the luminous intensity of the illumination light source is increased. You may provide the adjustment part to adjust.

  Further, the wavelength variable filter or the spectral characteristic correction filter may be arranged in either the illumination optical system or the light receiving optical system. In this embodiment, an example in which a liquid crystal wavelength tunable filter is used as the wavelength tunable filter has been described. However, a wavelength may be changed using a spectroscope such as a diffraction grating or a prism. The spectral characteristic of the spectral characteristic correction filter changes depending on the spectral characteristics of the light source, imaging means, and wavelength variable filter used, and is not limited to the blue filter. Further, the light source is not limited to the halogen lamp, and any light source that emits a light beam in a predetermined wavelength range may be used. The light receiving surface is not limited to the CCD, and for example, a CMOS may be used. The spectral measurement wavelength range can be selected from the visible region to the near infrared region, and in particular, it is desirable to select an area where the change in the spectral distribution characteristics of the absorbed light quantity of the artery or vein is large.

  In the present embodiment, the example of acquiring the fundus image original data in order from the lowest wavelength has been described. However, the order may be changed.

  FIG. 21 is a diagram for explaining the image acquisition order. FIG. 21A shows a case where the original images are acquired in order from the shorter wavelength, which is an ideal acquisition order, and the correction of the change in the alignment between the eye and the apparatus due to the time change can be performed with high accuracy. In FIG. 21B, the order does not necessarily depend on the order of the wavelengths, but when the adjacent wavelengths are close and the wavelength change amount does not exceed the threshold value (for example, the threshold value is 30 nm and the wavelength change amount is 10 nm), the position of the image can be corrected even in such a case. In FIG. 21C, the order is skipped in the middle, and the position correction becomes difficult. However, the position correction can be performed between the data of the previous group and the data of the subsequent group. Even in this case, in a short wavelength range, it can be said that image position correction is performed while comparing and collating original fundus image original data within a range in which the amount of change in wavelength does not exceed the threshold value. FIG. 21D is an example in which the measurement is resumed by returning to the previous acquired wavelength when position correction becomes impossible due to a problem such as movement of the eye E during measurement. Data of the same wavelength is shared by the two groups before and after, and a series of fundus image data that has been subjected to accurate position correction based on these data can be acquired. FIG. 21E shows a case where the wavelength is acquired in order from the highest wavelength, and correction of the change in the alignment between the eye and the apparatus due to the time change can be performed with high accuracy as in FIG.

  FIG. 21 (f) performs position correction using the original data having the next highest wavelength as the pre-correction image with reference to an image near the median value of the measurement wavelength range where a relatively stable image is obtained, The corrected pre-correction image is used as a new reference image, and the original data with the next highest wavelength is used as the pre-correction image for position correction, and then the position correction is performed sequentially from the lower wavelength to the higher wavelength. After the maximum wavelength is reached, position correction is performed using the original data with the next lowest wavelength as the pre-correction image with reference to the image near the median of the measurement wavelength range, and then the corrected pre-correction image is displayed. This is a case where a new reference image is used to perform position correction using the original data with the next lowest wavelength as the pre-correction image, and the position correction is performed sequentially from the higher wavelength to the lower wavelength. As in FIG. 21 (a), it is possible to correct the change in the alignment between the eye and the apparatus due to a change in time with high accuracy. The same applies to the case where the position correction is performed sequentially from the wavelength near the median to the higher wavelength first, and the position correction is performed sequentially from the wavelength near the median to the higher wavelength.

  In addition, the order of steps in this embodiment can be changed. For example, FIG. 11 illustrates an example in which the fundus image is stored in a lump after acquiring the spectral fundus images of all wavelengths in the spectroscopic measurement wavelength range, but each fundus is acquired immediately after the spectral fundus image of each wavelength is acquired. A loop that preserves the image may be used. In FIG. 14, image positioning may be performed while sequentially reading the fundus image original data (pre-correction image) from the CCD camera, and all the fundus image original data is once acquired from the CCD camera by the data measurement unit. The image positioning may be performed while the fundus image original data (pre-correction image) stored in the data acquisition unit is sequentially read into the image correction unit and re-read into the image correction unit.

  In addition, the spectral fundus image acquisition flow and the CCD camera exposure time setting flow program are stored in the control unit, and the spectral retinal image alignment flow and spectral retinal image analysis flow program are stored in the data measurement unit. The control unit may hold all these programs and control the entire spectral fundus image data measurement apparatus including the data measurement unit, and the control unit may read these programs from an external recording device or a CDROM. The spectral fundus image data measuring device may be controlled.

  In the spectral retinal image analysis in the present embodiment, the influence of components other than hemoglobin is omitted, but an algorithm that takes into account the influence of these components may be used. Also in the image correlation processing, a simple and rough method other than the least square method may be used.

  The present invention is used for measurement of spectral fundus image data.

It is a figure which shows the structural example of the spectral fundus image data measuring apparatus in the embodiment of the present invention. It is a figure which shows the example of the spectral characteristics of a halogen lamp. It is a figure which shows the example of the spectral sensitivity characteristic of a CCD camera. It is a figure which shows the example of the band pass characteristic of a liquid crystal wavelength tunable filter. It is a figure which shows the structural example of a liquid crystal wavelength variable filter. It is a figure which shows the example of the wavelength selection method of a liquid crystal wavelength variable filter. It is a figure which shows the example of the spectral characteristic which considered the spectral characteristic of the halogen lamp, the liquid crystal wavelength variable filter, and the CCD camera. It is a figure which shows the example of the spectral characteristic of a spectral characteristic correction filter. It is a figure which shows the example of the spectral characteristic of the optical system which inserted the spectral characteristic correction filter. It is a figure which shows the example of the flow of the spectral fundus image data measuring method in embodiment of this invention. It is a figure which shows the example of a spectroscopic fundus image acquisition flow. It is a figure which shows the example of a CCD camera exposure time setting flow. It is a figure which shows the example of a spectral retinal image position alignment flow. It is a figure which shows the example of an image position alignment flow. It is a figure for demonstrating the least squares matching. It is a figure which shows the example of the absorbed light quantity of oxidation and reduction | restoration hemoglobin. It is a figure which shows the example of a spectral retinal image analysis flow. It is a figure which shows the example of the acquired spectral retinal image of a normal eye. It is a figure which shows the example of the acquired spectral retinal image of BRVO eyes. It is a figure which shows the example of the color code map of a fundus photograph. It is a figure for demonstrating the image acquisition order.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Spectral fundus image data measuring device 2 Fundus camera part 3 Top housing part 4 Imaging part 5 Relay optical system 6 Camera relay part 7 Data measuring part 8 Control part 9 Expansion part 10 Illumination optical system 11 Halogen lamp 12 Condenser lens 13 Spectral characteristic correction Filter 14 Diaphragm 15 Reflecting mirror 16 Relay lens 20 Light receiving optical system 21 Iris diaphragm plate 22 Focusing lens 23 Imaging lens 24 Reflecting mirror 25 Switching mirror 31 Dichroic mirror 32 Liquid crystal wavelength variable filter 33 Imaging lens 34 CCD camera 40 Common optics System 41 Beam splitter 42 Objective lens 50 Alignment optical system 51 Alignment light source 52 Dichroic mirror 53 Imaging lens 54 Camera for monitor 60 Finder optical system 71 Data acquisition unit 72 Image correction unit 73 Image analysis unit 74 Map creation unit 1 exposure control unit 82 wavelength control unit E subject's eye F fundus

Claims (13)

An illumination optical system for illuminating the fundus of the eye to be examined;
A light receiving optical system that receives a reflected light beam from the illuminated fundus and forms a fundus image on a light receiving surface of an imaging unit;
A data measurement unit that performs a position comparison of an image by comparing and collating a plurality of original fundus image data acquired at different times based on signals from the light receiving surface, and generates a series of fundus image data corrected in position. Prepare;
Spectral fundus image data measurement device. The position correction of the image is performed by selecting feature points between the plurality of spectral fundus image original data and performing correlation using correlation processing and affine transformation or Helmat transformation;
The spectral fundus image data measurement apparatus according to claim 1. The illumination optical system has an illumination light source that emits a light beam in a predetermined wavelength range;
A wavelength tunable filter disposed in either the illumination optical system or the light receiving optical system and capable of selecting a wavelength of a transmitted light beam in the predetermined wavelength range;
The data measurement unit acquires the plurality of fundus image original data by changing a wavelength of a transmitted light beam of the wavelength tunable filter;
The spectral fundus image data measurement apparatus according to claim 1 or 2. Arranged in either the illumination optical system or the light receiving optical system, the wavelength characteristic of the luminous intensity of the illumination light source and the transmission wavelength characteristic of the wavelength variable filter are corrected, and the received light intensity on the light receiving surface is within a predetermined range. A spectral characteristic correction filter having a wavelength characteristic that falls within a range;
The spectral fundus image data measurement apparatus according to claim 3. A change amount of a selected wavelength in the tunable filter can be set to a threshold value or less;
The data measurement unit corrects the position of the image while comparing and comparing the fundus image original data having different wavelengths by a change amount equal to or less than the threshold;
The spectral fundus image data measurement apparatus according to claim 3 or 4. The predetermined wavelength range is 540 to 610 nm, and the amount of change below the threshold is 10 nm;
The spectral fundus image data measurement apparatus according to claim 5. The tunable filter is a liquid crystal tunable filter;
The spectroscopic fundus image data measurement apparatus according to any one of claims 3 to 6. The data measurement unit selects a blood vessel portion on the short wavelength side and a choroidal blood vessel portion on the long wavelength side as the feature point, and corrects the position of the image;
The spectroscopic fundus image data measurement apparatus according to any one of claims 2 to 7. The data measuring unit can calculate the received light intensity and optical density (hereinafter referred to as OD in the claims) of arteries and veins;
The spectral fundus image data measurement apparatus according to any one of claims 3 to 8. The data measurement unit performs correction based on the diameter of the blood vessel at the site where the strength of the artery and vein is calculated, calculates the OD at each position on the retina, and calculates each position based on the spectral distribution of the OD of the artery and vein. OD factor analysis at, calculate the percentage of oxygenated hemoglobin at each position,
Map the proportion of oxyhemoglobin;
The spectral fundus image data measurement apparatus according to claim 9. Illuminating the fundus of an animal eye with a light beam from an illumination light source that emits a light beam in a predetermined wavelength range;
Receiving a reflected light beam from the fundus and forming a fundus image of the animal on the light receiving surface of the imaging unit;
A liquid crystal wavelength tunable filter capable of selecting a wavelength of a transmitted light beam in the predetermined wavelength range is disposed in either an illumination optical system or a light receiving optical system, and the wavelength of the transmitted light beam of the liquid crystal wavelength tunable filter is changed to receive the light Obtaining spectral fundus image original data based on signals from the surface;
In the data measurement unit, a step of comparing and collating original spectral fundus image data different in wavelength by a change amount equal to or less than a threshold value to perform image position correction and generating a series of spectral fundus image data in the predetermined wavelength range. Prepare;
Spectral fundus image data measurement method. In performing the position correction of the image, the position correction is performed by using the original data with the lowest wavelength among the spectral fundus image original data as the reference image and the original data with the second lowest wavelength as the pre-correction image. The position correction is performed using the pre-correction image as a new reference image and the original data with the third lowest wavelength as the pre-correction image, and the position correction is performed sequentially from the lower wavelength to the higher wavelength;
Alternatively, position correction is performed using the original data with the highest wavelength among the spectral fundus image original data as the reference image and the original data with the second highest wavelength as the pre-correction image, and then the corrected pre-correction image is updated. The reference image is subjected to position correction using the original data with the third highest wavelength as the pre-correction image, and thereafter the position correction is sequentially performed from the higher wavelength to the lower wavelength;
The spectral fundus image data measurement method according to claim 11. The spectral fundus image original data image is obtained by setting the predetermined wavelength range to 540 to 610 nm and the change amount of the selected wavelength in the liquid crystal wavelength tunable filter to 10 nm,
The positional correction of the image is performed by using spectral processing and affine transformation or Helmat transformation by selecting feature points between the spectral fundus image original data different from each other by the change amount of the wavelength below the threshold,
Select the artery and vein as the feature points, calculate the received light intensity and OD of the artery and vein,
Correction is performed by the diameter of the blood vessel at the site where the strength of the artery and vein is calculated, and the OD at each position on the retina is calculated.
Perform factor analysis of OD at each position on the retina based on the spectral distribution of OD of arteries and veins, calculate the ratio of oxyhemoglobin at each position on the retina,
Mapping the proportion of oxyhemoglobin in the spectral fundus image;
The spectral fundus image data measurement method according to claim 11 or 12.