JP2010057547A - Fundus camera - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To dispense with a dedicated signal processing means and to have simple structure when observing an object with a near-infrared light and generating a color still image. <P>SOLUTION: This fundus camera includes a near-infrared light generation means for observing an object with a near-infrared light, a visible light generation means for capturing an image with a visible light, an observation/imaging optical system receiving a reflected light from the fundus oculi and focusing a fundus image, a capturing means having three color filters of R, B and G disposed into a mosaic shape in front of respective pixels and capturing a fundus image, and a computing means calculating virtual pixel values of a tricolor image from adjoining pixel values and generating color image data. The color filter R is defined as a color filter transmitting the near-infrared light and the number of the filters R is defined to be more than the numbers of the color filters B and G. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a fundus camera for observing and photographing the fundus of a subject's eye.

  As Conventional Example 1, a fundus camera including an imaging unit for near-infrared observation for alignment and an imaging unit for color still image shooting has been put into practical use.

  Further, as Conventional Example 2, a fundus camera that performs position alignment with near-infrared light using one imaging unit and performs imaging with visible light is disclosed in Patent Documents 1 and 2 and put into practical use.

  Furthermore, as a third conventional example, Patent Document 3 discloses an electronic endoscope in which a color filter for three-color separation and a dedicated filter that transmits infrared rays are configured by a single-plate image sensor.

Japanese Patent Laid-Open No. 7-79926 JP 2002-369802 A JP 2006-6922 A

  The fundus camera as in Conventional Example 1 includes a near-infrared observation imaging unit for alignment and a color still image imaging unit. At the time of shooting, an optical path switching mechanism such as a quick return mirror for instantaneously switching the imaging means from observation to shooting is required, which makes the mechanism complicated and expensive.

  The fundus camera as in Conventional Example 2 does not require an optical path switching mechanism, but requires a three-plate type imaging means having an expensive three-color separation prism.

  Further, in the image pickup device as in Conventional Example 3, since the configuration of the color filter is different from a general Bayer pattern, a dedicated signal processing circuit is required.

  An object of the present invention is to solve the above-mentioned problems and provide a fundus camera having a simple configuration without requiring a dedicated signal processing means when observing with near infrared light and generating a color still image. There is.

  In order to achieve the above object, a fundus camera according to the present invention includes a near-infrared light generating means for irradiating the fundus of a subject's eye with near-infrared light for observation with near-infrared light, and imaging with visible light. Visible light generation means that irradiates the fundus with visible light region, observation imaging optical system that receives the reflected light from the fundus and forms a fundus image, and a mosaic pattern for three-color separation in front of each pixel An image pickup means for picking up a fundus image formed by the observation photographing optical system, and calculating a virtual pixel value of the three-color separation image from the adjacent pixel values, and a color image In the fundus camera having a computing unit for generating data, the imaging unit is composed of a single-plate imaging device that outputs a moving image and a still image, and the color filter of at least one of the three color filters is Color pass that transmits near-infrared light And filter, characterized in that the number of the color filter was greater than the number of color filters of other colors.

  The fundus camera according to the present invention does not require dedicated signal processing means for observation and photographing, and can be configured simply. Also, the sensitivity (S / N) of near-infrared light can be increased by increasing the allocation of color filters that are most sensitive to near-infrared light, such as CCDs and CMOS sensors, which generally decrease in sensitivity. .

  The present invention will be described in detail based on the embodiments shown in the drawings.

  FIG. 1 is a configuration diagram of a fundus camera in the first embodiment. A diaphragm 3 having a ring-shaped opening and a dichroic mirror 4 are arranged on an optical path O1 from the observation light source 1 which is a near infrared light generation means to the objective lens 2. In the incident direction of the dichroic mirror 4, a diaphragm 5 having a ring-shaped opening and a photographing light source 6 which is a visible light generating means are arranged. On the optical path O1 in the emission direction of the dichroic mirror 4, a relay lens 7, a mirror 8, a relay lens 9, and a perforated mirror 10 are sequentially arranged to constitute a fundus illumination optical system.

  On the optical path O2 in the direction of incidence on the mirror 8, a two-hole stop 11, a lens 12, a focusing index 13, and a focusing index light source 14 are arranged to configure a focusing index projection optical system.

  On the optical path O3 behind the perforated mirror 10, a focusing lens 15, a photographing lens 16, and an imaging means 17 are arranged to constitute an observation photographing optical system. In the imaging means 17, a three-color wavelength separating means 18 is provided. An image sensor 19 is provided. An alignment index light source 21 is disposed in the hole of the perforated mirror 10 through the optical fiber 20.

  The focusing index projection optical system moves in the direction A parallel to the optical path O1 in conjunction with the focusing lens 15, projects the focusing index 13 on the fundus Er of the eye E, and the optical path O1 when shooting a still image. Is moved away from the fundus illumination optical system.

  The output of the imaging means 17 is connected to the arithmetic control unit 32 and the display 33 via the image signal processing unit 31. The output of the arithmetic control unit 32 is connected to the observation light source 1 via the observation light source driving circuit 34 and to the imaging light source 6 via the imaging light source driving circuit 35. Further, it is connected to the focusing index light source 14 via the focusing index light source driving circuit 36, and to the positioning index light source 21 via the positioning index light source driving circuit 37. Further, an input unit 38 and a recording unit 39 are connected to the arithmetic control unit 32.

  At the time of fundus observation, the calculation control unit 32 drives the observation light source drive circuit 34 to turn on and dim the observation light source 1. The light beam emitted from the observation light source 1 passes through the diaphragm 3 and the dichroic mirror 4. Here, the observation light source 1 is composed of a near-infrared LED having a center wavelength at 850 nm, and the dichroic mirror 4 transmits near-infrared light and reflects visible light. Therefore, the light emitted from the observation light source 1 Reaches the dichroic mirror 4. Near-infrared light that has passed through the dichroic mirror 4 passes through the relay lens 7, the mirror 8, and the relay lens 9, is reflected around the perforated mirror 10, and passes through the objective lens 2, the cornea Ec and the pupil Ep of the eye E to be examined. Illuminates the fundus Er.

  At the same time, the arithmetic control unit 32 drives the focusing index light source driving circuit 36 to turn on the focusing index light source 14. The focusing index light source 14 is composed of a near-infrared LED having a center wavelength of 850 nm. The light beam from the focusing index light source 14 illuminates the focusing index 13, and the image of the focusing index 13 passes through the lens 12, the two-hole aperture 11, is reflected by the mirror 8, and is reflected from the observation light source 1. It is superimposed on the light beam and projected onto the fundus Er of the eye E to be examined.

  The fundus image and the focus index image on the fundus Er pass through the pupil Ep of the eye E, the cornea Ec, the objective lens 2 and the hole of the perforated mirror 10, pass through the focusing lens 15 and the photographing lens 16, and are imaged. An image is formed on the image sensor 19 through the three-color wavelength resolving means 18 in the means 17.

  At the time of alignment, that is, alignment in this state, the calculation control unit 32 drives the alignment index light source driving circuit 37 to turn on the alignment index light source 21. The alignment index light source 21 is composed of a near infrared LED having a center wavelength of 850 nm. Near-infrared light from the alignment index light source 21 irradiates the cornea Ec of the eye E through the optical fiber 20 and the objective lens 2, and reflected light from the observation light source 1 and the focusing index light source 14. An image is formed on the image sensor 19 by being superimposed on the reflected light from the fundus Er.

  In the image sensor 19, photoelectric conversion is performed on the formed fundus image, focus index image, and alignment index image, and the image signal processing unit 31 reads and amplifies data from the image sensor 19. Digital image data that is a moving image is generated and displayed on the display 33.

  FIG. 2 shows the state displayed on the display device 33. The central wavelengths of the observation light source 1, the focusing index light source 14, and the alignment index light source 21 are in the near-infrared light region, and operate as a non-mydriatic mode. is doing. FIG. 2A shows a state in which the position and the focus are deviated, and the operator moves the apparatus back and forth, right and left, and up and down by an operation unit (not shown) while looking at the alignment index. Align the image. Next, focusing is performed by moving the focusing index projection optical system in the direction A in FIG. 1 in conjunction with the focusing lens 15 while viewing the focusing index image.

  In FIG. 2B, the alignment index image by the alignment index light source 21 coincides with the index circle, the alignment is completed, and the two focusing index images are aligned, and the focusing is completed. It shows a state.

  The image pickup device 19 in the image pickup means 17 includes red (R), green (G), and blue (B) arranged in a mosaic pattern for three-color separation so as to match each pixel of the image pickup device 19. A three-color wavelength resolving means 18 comprising a filter is disposed. The image signal processing unit 31 reads out and amplifies data of each pixel from the image sensor 19 and calculates a virtual pixel value of the three-color separation image to generate an image.

FIG. 3 is an arrangement diagram of a normal three-color filter constituting the three-color wavelength decomposing means 18, and the calculation of the virtual pixel P00 is generally performed as follows by the color dither method. The RGB color values of the virtual pixel P00 are the light reception data of the adjacent pixels R00, R02, B11, G12, B13, R20, G21, R22, B31, and B33 among the pixels surrounded by the solid line around the virtual pixel P00. Is used. If the RGB values of the virtual pixel P00 are P00r, P00g, and P00b, respectively, the calculation is performed as follows.
P00g = (G12 + G21) / 2
P00r = (9 · R22 + 3 · R02 + 3 · R20 + R00) / 16
P00b = (9 · B11 + 3 · B13 + 3 · B31 + B33) / 16

In the case of the virtual pixel P01 on the right side, light reception of pixels R02, R04, B11, G12, B13, R22, G23, R24, B31, and B33 among the pixels surrounded by a dotted line around the virtual pixel P01. From the data, it is calculated as follows:
P01g = (G12 + G23) / 2
P01r = (9 · R22 + 3 · R02 + 3 · R24 + R04) / 16
P01b = (9 · B13 + 3 · B11 + 3 · B33 + B31) / 16

  In the same manner, the virtual pixel value is calculated from the received light data in the range of 4 and 4 pixels adjacent to each virtual pixel P to generate one piece of color image data.

  FIG. 4 is a layout diagram of the color filters of the three-color wavelength separation means 18 used in this embodiment, and the number of R filters that transmit near-infrared light is larger than the number of G and B filters. . Thereby, the sensitivity at the time of observation by near-infrared light is improved.

The RGB color values of the virtual pixel P00 by this color filter are the G00, G02, B11, R12, B13, G20, R21, G22, B31, and B33 pixels among the pixels surrounded by the solid line around the virtual pixel P00. The received light data is used. If the RGB values of the virtual pixel P00 are P00r, P00g, and P00b, respectively, the calculation is performed as follows.
P00r = (R12 + R21) / 2
P00g = (9 · G22 + 3 · G02 + 3 · G20 + G00) / 16
P00b = (9 · B11 + 3 · B13 + 3 · B31 + B33) / 16

In the case of the virtual pixel P01 on the right side, of the pixels surrounded by dotted lines around the virtual pixel P01, the pixels G02, G04, B11, R12, B13, G22, R23, G24, B31, and B33 It is calculated from the received light data as follows.
P01r = (R12 + R23) / 2
P01g = (9 · G22 + 3 · G02 + 3 · G24 + G04) / 16
P01b = (9 · B13 + 3 · B11 + 3 · B33 + B31) / 16

  In the same manner, the virtual pixel value is calculated from the received light data in the range of 4 and 4 pixels adjacent to each virtual pixel P to generate one piece of color image data.

  By using the color filter having the configuration shown in FIG. 4, the virtual pixel is calculated using the general color filter calculation formula shown in FIG. In this configuration, the expressions r and g in FIG. Therefore, no special calculation means is required.

  FIG. 5 shows the spectral sensitivity characteristics of the image pickup means 17 in which the three-color wavelength resolving means 18 and the image pickup device 19 in FIG. 4 are combined. The focusing index light source 14, the alignment index light source 21, and the observation light source 1 centered on near-infrared light have only the red (R) component that transmits near-infrared light due to this spectral sensitivity characteristic. It can be seen that there is sensitivity.

  Accordingly, at the time of fundus observation, the image fundus image, the focus index image, and the alignment index image formed on the image sensor 19 are sensitive only to R pixels that transmit near-infrared light. By 31, only the data of r virtual pixels is displayed on the display 33 as a monochrome image.

  At the time of fundus photographing using a color image, the operator performs alignment and focusing while viewing the image shown in FIG. 2A displayed on the display device 33, and the position and focus as shown in FIG. 2B. When the right position is met, the photographing switch configured in the input unit 38 is pressed. The arithmetic control unit 32 detects this and drives the photographing light source drive circuit 35 to emit visible light from the photographing light source 6. Further, the alignment index light source 21 is turned off by the alignment index light source driving circuit 37, and the focusing index projection optical system is driven in the B direction to be retracted from the optical path.

  The light beam emitted from the imaging light source 6 passes through the diaphragm 5, is reflected by the dichroic mirror 4 that reflects the light beam in the visible light region, and illuminates the fundus Er of the eye E to be examined through the same path as the observation light source 1. The fundus image, which is light, is formed on the image sensor 19 via the three-color wavelength resolving means 18.

  The fundus image is photoelectrically converted by the image sensor 19 and photographed with visible light, read by the image signal processing unit 31, digital color image data that is a still image is generated, and displayed on the display 33. The At the same time, the color image data is recorded in the recording unit 39 via the arithmetic control unit 32.

  Since the imaging light source 6 outputs light having a wavelength in the entire visible light range, the color image data of the fundus is obtained using the r, g, and b data of the virtual pixel P obtained by the same calculation as in fundus observation. Generated.

  In the second embodiment, the three-color filter of the three-color wavelength separating means 18 having the same arrangement as that of the first embodiment shown in FIG. 4 is used. As in FIG. 5, the spectral sensitivity characteristics of the imaging means 17 are such that the focus index light source 14, the alignment index light source 21, and the observation light source 1 are sensitive only to the red (R) component that transmits near-infrared light. The sensitivity is low compared to the visible light region.

  If the virtual pixel P00ir of the near-infrared image of the virtual pixel P00 shown in FIG. 4, among the pixels surrounded by the surrounding solid line, the pixel values of R01, R03, R10, R12, R21, R23, R30, R32 It can be calculated as:

P00ir = R01 + R03 + R10 + R12 + R21 + R23 + R30 + R32
Also, assuming that the virtual pixel P01ir of the near-infrared image of the virtual pixel P01 on the right is the pixels R01, R03, R12, R14, R21, R23, R32, and R34 among the pixels surrounded by the dotted lines around P01. From the value, it is calculated as follows:

P01ir = R01 + R03 + R12 + R14 + R21 + R23 + R32 + R34
At the time of fundus observation, the image fundus image, the focus index image, and the alignment index image formed on the image sensor 19 are sensitive only to pixels having an R filter that transmits near-infrared light. Accordingly, the image signal processing unit 31 uses the near-infrared light of the virtual pixel P to produce a monochrome moving image, thereby increasing the sensitivity (S / N) even with near-infrared light with low sensitivity and displaying it on the display 33. can do. Note that, except for the calculation of a monochrome moving image, such as calculation of a color image and shooting, the same as in the first embodiment.

  In the second embodiment, the R pixel value is simply added. However, depending on the required sensitivity and frequency band, each pixel value may be weighted by a coefficient when adding.

  In the third embodiment, a general three-color filter arrangement similar to that in FIG. 3 is used, and the G filter is a filter that transmits near-infrared light, and the number thereof is larger than the number of R and B filters. .

  FIG. 6 shows the spectral sensitivity characteristics of the image pickup means 17 combining the three-color wavelength resolving means 18 and the image pickup device 19 in the third embodiment. The wavelengths of the focusing index light source 14, the alignment index light source 21, and the observation light source 1 are sensitive only to the green (G) component that transmits near-infrared light according to the spectral sensitivity characteristics shown in FIG. I understand. The calculation of the virtual pixel P00 of the color filter is expressed as follows regardless of whether or not near-infrared light passes through green (G) as follows.

The RGB color values of the virtual pixel P00 are the R00, R02, B11, G12, B13, R20, G21, R22, B31, and B33 pixels among the pixels surrounded by the solid line around the virtual pixel P00 shown in FIG. It is calculated from the received light data as follows. If the RGB values of the virtual pixel P00 are P00r, P00g, and P00b, respectively, the following equation is obtained.
P00g = (G12 + G21) / 2
P00r = (9 · R22 + 3 · R02 + 3 · R20 + R00) / 16
P00b = (9 · B11 + 3 · B13 + 3 · B31 + B33) / 16

In the case of the virtual pixel P01 on the right side, light reception of pixels R02, R04, B11, G12, B13, R22, G23, R24, B31, and B33 among the pixels surrounded by a dotted line around the virtual pixel P01. From the data, it is calculated as follows:
P01g = (G12 + G23) / 2
P01r = (9 · R22 + 3 · R02 + 3 · R24 + R04) / 16
P01b = (9 · B13 + 3 · B11 + 3 · B33 + B31) / 16

  In the same manner, the virtual pixel value is calculated from the received light data in the range of 4 and 4 pixels adjacent to each virtual pixel P to generate one piece of color image data.

  At the time of fundus observation, the image fundus image, the focus index image, and the alignment index image formed on the image sensor 19 are sensitive only to G pixels that transmit near infrared light. Therefore, the image signal processing unit 31 displays only the virtual pixel data of the virtual pixel P on the display device 33 as a monochrome moving image.

  At the time of fundus photographing, since the photographing light source 6 outputs wavelength light in the entire visible light range, color fundus image data is obtained by using the r, g, and b data of the virtual pixel P obtained by the same calculation as in fundus observation. Is generated.

  In the third embodiment, the G filter is made to transmit near infrared light, but the B filter may be made to transmit near infrared light. Also, with this filter configuration, it is possible to calculate a ir (near infrared light component) of the virtual pixel P from the G filter as in the second embodiment to obtain a monochrome moving image.

1 is a configuration diagram of a fundus camera of Example 1. FIG. It is explanatory drawing of position alignment and a focus adjustment. It is a filter arrangement diagram of a conventional general three-color wavelength resolving means. FIG. 3 is a filter layout diagram of the three-color wavelength resolving means used in the first embodiment. FIG. 6 is a spectral sensitivity characteristic diagram in which the three-color wavelength resolving unit and the image sensor in FIG. 4 of Example 2 are combined. FIG. 6 is a spectral sensitivity characteristic diagram in which the three-color wavelength resolving means of FIG. 3 in Example 3 and an image sensor are combined.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light source for observation 2 Objective lens 4 Dichroic mirror 6 Light source for imaging 8 Mirror 10 Perforated mirror 11 2 hole aperture 13 Focusing index 14 Focusing index light source 15 Focusing lens 16 Shooting lens 17 Imaging means 18 Three-color wavelength separation Means 19 Image pickup device 20 Optical fiber 21 Alignment index light source 31 Image signal processing unit 32 Arithmetic control unit 33 Display unit 38 Input unit 39 Recording unit

Claims (2)

  Near-infrared light generation means for irradiating the fundus of the subject's eye with near-infrared light for observation with near-infrared light, and visible light generation means for irradiating the fundus with light in the visible light region for imaging with visible light An observation imaging optical system that receives reflected light from the fundus and forms a fundus image, and a three-color color filter arranged in a mosaic pattern for three-color separation in front of each pixel. In the fundus camera comprising: an imaging unit that captures a fundus image formed by a system; and an arithmetic unit that calculates a virtual pixel value of a three-color separation image from values of the adjacent pixels and generates color image data The means comprises a single-plate image sensor that outputs a moving image and a still image, and the color filter of at least one of the three-color filters is a color filter that transmits near-infrared light. Number of other colors Fundus camera, characterized in that the more than the number of filter.   The fundus camera according to claim 1, wherein the virtual pixel value when generating monochrome image data using near-infrared light is calculated using adjacent pixels having sensitivity to near-infrared light.