JP2006158546A - Spectrum ocular fundus image data measuring apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To be gentle to the eyes of a subject and to obtain satisfactory spectrum characteristic by reducing fluctuation of light-receiving intensity due to a frequency. <P>SOLUTION: This spectrum ocular fundus image data measuring apparatus 1 is provided with: an illumination optical system 10 having a light source 11 for illumination which emits a beam in a prescribed wavelength range; a light-receiving optical system 20 for forming an eye fundus image on the light-receiving surface of an imaging part 4; a liquid crystal wavelength variable filter 32 by which a wavelength of a translucent beam is selectable in the prescribed wavelength range; a spectrum characteristic correction filter 13 which corrects the wavelength characteristic of light-emitting intensity of the light source 11 and the translucent wavelength characteristic of the filter 32 and which has such wavelength characteristic where the light-receiving intensity on the light-receiving surface is within the prescribed range; and a data measurement part which obtains spectrum ocular fundus image data from the light-receiving surface by varying the wavelength of the translucent beam of the filter 32. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a spectral fundus image data measurement apparatus. 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, refer nonpatent literature 1) Moreover, as an apparatus which acquires the spectroscopic image of the fundus applicable to a human eye, it has been examined to acquire a spectroscopic image by performing spectroscopy using a diffraction grating and scanning the fundus. . (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, due to the spectral characteristics of the light source (halogen lamp, etc.), CCD, and liquid crystal wavelength tunable filter, there is a problem that the light amount is insufficient on the short wavelength side and the light amount is excessive on the long wavelength side (range from 500 nm to 700 nm).

  The present invention is a spectral fundus image that reduces fluctuations of the received light intensity due to the frequency, keeps the received light intensity on the light receiving surface within a predetermined range, is easy on the subject's eyes, and can provide good spectral characteristics. An object is to provide a data measurement device.

  In order to solve the above-described problem, the spectral fundus image data measuring apparatus 1 according to claim 1 includes an illumination light source 11 that emits a light beam in a predetermined wavelength range as shown in FIG. An illumination optical system 10 that illuminates the fundus F of the eye E with a light beam from the light source 11, and a light receiving optical system that receives a reflected light beam from the illuminated fundus F and forms a fundus image on the light receiving surface of the imaging unit 4. 20, a wavelength variable filter 32 that is arranged in either the illumination optical system 10 or the light receiving optical system 20 and can select the wavelength of the transmitted light beam in a predetermined wavelength range, and either the illumination optical system 10 or the light receiving optical system 20. A spectral characteristic correction filter 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 tunable filter 32 so that the received light intensity on the light receiving surface falls within a predetermined range. 13 and Upon changing the wavelength of the transmitted light beam of length variable filter 32, and a data measurement section 7 for acquiring spectral fundus image data on the basis of a signal from the light receiving surface.

  Here, the light receiving surface is preferably a CCD, but may be a CMOS. If comprised in this way, a spectral image can be acquired by arbitrary wavelengths by using a wavelength variable filter, and spectral image measurement is also possible about a fundus image. In addition, by adopting a spectral characteristic correction filter, it is easy on the subject's eyes and can correct fluctuations due to the frequency of received light intensity to keep the received light intensity on the light receiving surface within a predetermined range. Spectral characteristics can be obtained.

Further, according to a second aspect of the present invention, in the spectral fundus image data measuring apparatus 1 according to the first aspect, for example, as shown in FIG. 1, the wavelength variable filter 32 is provided in the light receiving optical system 20, and the spectral characteristic correction filter 13. Is disposed in the illumination optical system 10.
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, 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 FIGS. 5 and 8, the wavelength tunable filter 32 is a liquid crystal wavelength tunable filter. The spectral characteristic correction filter 13 is configured such that the transmittance is higher on the short wavelength side than on the long wavelength side in the predetermined wavelength range.
With this configuration, it is possible to easily select an arbitrary wavelength in the visible light region using the liquid crystal wavelength tunable filter, and to correct the spectral characteristics of the halogen lamp and the liquid crystal wavelength tunable filter with the spectral characteristic correction filter to achieve uniformity. Excellent spectral characteristics can be realized.

According to a fourth aspect of the present invention, in the spectral fundus image data measuring apparatus 1 according to any one of the first to third aspects, the predetermined wavelength range is 540 to 610 nm.
If comprised in this way, data useful for the spectroscopic analysis of the substance in a retina can be provided.

According to a fifth aspect of the present invention, in the spectroscopic fundus image data measuring apparatus 1 according to any one of the first to fourth aspects, the light receiving surface is formed of a CCD, and a predetermined range of received light intensity is obtained. It is within the dynamic range of the CCD.
If comprised in this way, by using together a spectral characteristic correction filter and a CCD camera, imaging with a CCD camera will become easy and automation of exposure will become possible.

The invention according to claim 6 is the spectral fundus image data measuring device according to any one of claims 1 to 5, wherein, for example, as shown in FIG. An exposure control unit 81 configured to automatically determine the exposure time according to the response is provided.
If comprised in this way, the exposure time of a camera can be changed in real time according to the light quantity at the time of imaging, the spectral characteristic of an optical system is correct | amended, and the image which was further excellent in the spectral characteristic can be acquired. By using in combination with the spectral characteristic correction filter, an image with further excellent spectral characteristics can be acquired.

  According to the present invention, it is possible to correct fluctuations of the received light intensity due to the frequency and keep the received light intensity on the light receiving surface within a predetermined range, which is easy on the subject's eyes and obtains good spectral characteristics. It is possible to provide a spectroscopic fundus image data measuring apparatus and measuring method that can be used.

  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 the 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 diameter of the blood vessel at the site where the strength of the artery and vein is calculated, calculates the optical density at each position on the retina (hereinafter referred to as OD), and calculates the OD of the artery and vein. Based on the spectral distribution of OD, factor analysis of OD at each position on the retina 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, the data measuring unit 7 sequentially measures spectral fundus image data in a predetermined wavelength range (step S004).

  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 descending 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.

  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 spectroscopic measurement wavelength range can be selected from the visible region to the near-infrared region, and it is particularly 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 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.

  Further, the example in which the program for the spectral fundus image acquisition flow and the CCD camera exposure time setting flow is stored in the control unit has been described, but the control unit holds all these programs and includes the data measurement unit. The control unit may control the spectral fundus image data measurement apparatus by reading these programs from an external recording device or CD ROM.

  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.

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 (6)

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 subject's eye with the light beam from the illumination light source;
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 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;
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 wavelength characteristics that fall within the range;
A data measurement unit that acquires spectral fundus image data based on a signal from the light receiving surface when the wavelength of the transmitted light beam of the wavelength tunable filter is changed;
Spectral fundus image data measurement device. The variable wavelength filter is disposed in the light receiving optical system, and the spectral characteristic correction filter is disposed in the illumination optical system;
The spectral fundus image data measurement apparatus according to claim 1. The wavelength tunable filter is a liquid crystal wavelength tunable filter, and the spectral characteristic correction filter is configured such that the transmittance is higher on the short wavelength side than on the long wavelength side in the predetermined wavelength range;
The spectral fundus image data measurement apparatus according to claim 1 or 2. The predetermined wavelength range is 540 to 610 nm;
The spectroscopic fundus image data measurement apparatus according to any one of claims 1 to 3. The light receiving surface is formed of a CCD, and the range of the predetermined light receiving light intensity is within the dynamic range of the CCD;
The spectral fundus image data measurement apparatus according to any one of claims 1 to 4. An exposure control unit configured to automatically determine an exposure time according to a light reception signal level on the light receiving surface;
The spectral fundus image data measurement apparatus according to any one of claims 1 to 5.