JP5084077B2 - Ophthalmic imaging equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an ophthalmologic photographing apparatus used in an ophthalmic clinic or a mass examination.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, for example, a fundus camera that captures an eye to be examined by connecting a CCD camera to an ophthalmologic photographing apparatus is known. In the fundus camera, when performing color photography or fluorescence photography, the electrical signal of the fundus image received by the CCD camera is A / D converted to, for example, 10 bits, and 8 by image processing by setting a lookup table (LUT). A method of converting the gradation into bits and displaying or recording them is generally known.
[0003]
6A and 6B are histograms of the luminance of the entire fundus image. FIG. 6A shows the case of color photography, and FIG. 6B shows the case of fluorescence photography. The horizontal axis represents luminance, and the vertical axis represents frequency, and A, B, and C correspond to the aperture portion, the macula portion, and the nipple, respectively.
[0004]
In normal gradation conversion, the range of L in FIG. 6 is converted into 8-bit digital data to acquire image data.
[0005]
[Problems to be solved by the invention]
However, in the above-described conventional example, the characteristics of the image are different between the color photographed image and the fluorescence photographed image. In the case of a color image, color information is required in addition to the grayscale information. In the case of images, emphasis is placed on shading information.
[0006]
Therefore, when these images are digitally converted (8-bit conversion), for example, a color image is applied with a look-up table that emphasizes the density resolution of the H and I portions in FIG. In the early to middle stages after intravenous injection, the frequency of dark areas is high. Therefore, when the color image look-up table is applied, the image information in the dark portion is lost, which hinders diagnosis. For this reason, an image that is easier to diagnose can be obtained by setting a lookup table suitable for the density resolution of the H ′ and I portions in FIG. 6B. Furthermore, entrusting the photographer with these image processing selections is troublesome because it takes time and effort to the photographer.
[0007]
An object of the present invention is to improve the above-described conventional example, and one of the more specific objects is to generate a more preferable image and improve diagnostic efficiency by setting gradation conversion suitable for the shooting mode. Another object of the present invention is to provide an ophthalmologic photographing apparatus that can be made to operate.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, an ophthalmologic photographing apparatus according to the present invention includes an acquisition unit that acquires an image signal representing a still image of an eye to be examined in any one of fluorescent photographing and color photographing, and the fluorescent photographing In this case, the image signal is converted by a first look-up table showing the first gradation conversion characteristic for fluorescence photography, while the selection means has a characteristic different from the first gradation conversion characteristic. Conversion means for converting the image signal with a second look-up table showing a second gradation conversion characteristic for color photographing, and each of the first look-up table and the second look-up table. Are associated with the pre-conversion luminance value, which is the luminance value of the image signal before conversion by the conversion means, and the post-conversion luminance value, which is the luminance value of the image signal after conversion by the conversion means. In the first look-up table, the range of the luminance value before conversion is a first range from a minimum luminance value to a first luminance value, and a luminance value from the first luminance value to the first luminance value. A second range up to a high second luminance value and a third range from the second luminance value to a maximum luminance value, wherein the first look-up table includes the second range in the second range. The change of the post-conversion luminance value with respect to the change of the pre-conversion luminance value is larger than the change of the post-conversion luminance value with respect to the change of the pre-conversion luminance value in each of the first range and the third range. While the pre-conversion luminance value and the post-conversion luminance value are associated, the range of the pre-conversion luminance value in the second look-up table is the range from the minimum luminance value to the third luminance value. 4 range and the above A fifth range from a luminance value to a fourth luminance value having a luminance value higher than the third luminance value, and a sixth range from the fourth luminance value to the maximum luminance value. 2 shows that the change in the post-conversion luminance value with respect to the change in the pre-conversion luminance value in the fifth range is the change in the pre-conversion luminance value in each of the fourth range and the sixth range. The pre-conversion luminance value and the post-conversion luminance value are associated with each other so as to be larger than the change of the post-conversion luminance value with respect to a change,
The fifth range is a range included in the second range .
[0013]
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be described in detail based on the embodiment shown in FIGS.
FIG. 1 is a configuration diagram of a fundus camera. The objective lens 1 is disposed in front of the eye E, a perforated mirror 2 is disposed on the optical path behind the eye E, the photographing lens 3 is movable for focusing, and is removable from the optical path in the direction of the arrow for fluorescent photographing. An imaging means 6 such as a barrier filter 4, a movable mirror 5, and a television camera is disposed.
[0014]
A half mirror 7 and a fixation lamp 8 conjugated with the fundus Er are arranged in the reflection direction of the movable mirror 5, and in the reflection direction of the half mirror 7, a relay lens 9 and a TV camera 10 having sensitivity in the infrared wavelength region are arranged. Place.
[0015]
Further, in the incident direction of the illumination light to the perforated mirror 2, from the observation light source 11 side that emits visible light such as a halogen lamp, a condenser lens 12, a visible light cut filter 13, an imaging light source 14 that emits visible light flash, An exciter filter 15 that can be inserted and removed from the optical path in the direction of the arrow, a diaphragm 16 having a ring-shaped opening, and a lens 17 are arranged for fluorescent imaging.
[0016]
Thus, the fundus observation imaging optical system is configured by the objective lens 1 and the imaging lens 3, and the fundus imaging optical system that images the fundus Er of the eye E together with the imaging unit 6 is configured. Further, an observation optical system that presents a fundus image to the photographer is configured by the movable mirror 5, the half mirror 7, the relay lens 9, and the television camera 10, and an illumination optical system is configured by the optical path of the perforated mirror 2 from the observation light source 11.
[0017]
The output of the imaging means 6 is connected to the frame memory 21 via the A / D converter 20. The output of the frame memory 21 is connected to the lookup table 22 and the lookup table setting unit 23, and the output of the lookup table 22 is connected to the display memory 24 and the recording medium 25.
[0018]
The image control unit 26 connected to the lookup table setting unit 23 is connected to the control circuit 27, the information input unit 28, the display memory 24, and the recording medium 25. The control circuit 27 is connected to the fixation lamp 8 and a selection switch 29 for performing color photographing or fluorescent photographing. The output of the television camera 10 is connected to the television monitor 30, and the output of the display memory 24 is connected to the television monitor 32 via the D / A converter 31.
[0019]
FIG. 2 is a flowchart showing an image data output procedure.
The photographer inputs patient information such as a subject's ID number, name, birth date, and sex, and a file format for outputting a photographed image from the information input means 28 to the image controller 26 before photographing. Next, the photographer positions the eye E in front of the objective lens 1 and performs alignment for fundus photography.
[0020]
When the observation light source 11 is turned on, the light is condensed by the condenser lens 12, and the observation light that has become only infrared light by the visible light cut filter 13 passes through the photographing light source 14, the diaphragm 16 , and the lens 17, and is a perforated mirror. 2 is reflected leftward and passes through the objective lens 1 to illuminate the fundus Er through the pupil Ep of the eye E to be examined. Then, the fundus image illuminated with the observation light passes through the holes of the objective lens 1 and the perforated mirror 2 again, is reflected upward by the movable mirror 5 through the photographing lens 3, and further leftward by the half mirror 7. And reaches the TV camera 10 through the relay lens 9. The television camera 10 having sensitivity to infrared light converts the received fundus image into a television signal and outputs the television signal to the television monitor 30. While viewing the fundus image presented on the television monitor 30, the photographer performs precise positioning, focusing, and confirmation of the photographing range between the eye E and the fundus camera.
[0021]
After confirming that the shooting range, position, and focus are good, the photographer operates a shooting switch (not shown) to take a still image. The control circuit 27 that has detected the input of the photographing switch flips up the movable mirror 5 to retreat from the optical path and emits the photographing light source 14. The light beam emitted from the imaging light source 14 passes through the ring-shaped opening of the diaphragm 16 like the observation light, passes through the lens 17, is reflected to the left by the mirror part around the perforated mirror 2, and passes through the objective lens 1. To illuminate the fundus Er. The illuminated fundus image passes through the hole of the objective lens 1 and the perforated mirror 2 again, forms an image on the imaging surface of the imaging means 6 through the imaging lens 3, and the imaging means 6 converts the TV signal into A. / D conversion unit 20 for output.
[0022]
The image control unit 26 synchronizes the television signal output from the imaging unit 6 with the light emission of the imaging light source 14, converts it into digital data by the A / D conversion unit 20, and then captures it in the frame memory 21. At this time, since the S / N ratio of the camera is usually 60 dB or more, the number of bits at the time of A / D conversion is converted with 10 bits, which is a bit number larger than 8 bits when output as a final file. .
[0023]
Here, in the case of color photography, the barrier filter 4 and exciter filter 15 are retracted out of the optical path, and in the case of fluorescence photography, the barrier filter 4 and exciter filter 15 are inserted into the optical path. These selections are made by the selection switch 29.
[0024]
Next, the image data is output by setting the lookup table 22 for the image data obtained as described above. 3A shows the entire color fundus image, FIG. 3B shows the entire fluorescent fundus image, Er ′ shows the fundus image, Eo shows the macula part, and Ea shows the aperture part. Each histogram diagram corresponds to FIGS. 6A and 6B, the horizontal axis represents luminance, and the vertical axis represents frequency.
[0025]
The look-up table setting unit 23 selects the look-up table 22 shown in FIGS. 4 and 5. For a color image, the look-up table having an inflection point due to D and E, that is, the luminance shown in FIG. A look-up table that emphasizes the portion of the range H is applied, and at the time of fluorescent photographing, a look-up table having inflection points at D ′ and E ′, that is, the luminance range H ′ in FIG. Apply a look-up table that emphasizes this part.
[0026]
Here, D and E in FIG. 4 correspond to D and E in FIG. 6A, respectively, and similarly D ′ and E ′ correspond to D ′ and E ′ in FIG. 6B, respectively. The tone conversion of the fundus image data in the frame memory 21 is performed via the lookup table 22 set in this way.
[0027]
If necessary, the image control unit 26 performs gradation conversion on the image data in the frame memory using the selected look-up table 22, and then writes the image data in the display memory 24, and performs D / A conversion on the written image data. By outputting to the television monitor 32, the photographer can check the image.
[0028]
Further, the image control unit 26 writes the image data to a recording medium 25 that can store and hold such as MO, MD, DVD-RAM, VTR tape, and hard disk.
[0029]
In this embodiment, the color photographing mode or the fluorescent photographing mode is performed by the selection switch 29 or the like. However, the mode may be detected by inserting the barrier filter 4 or the exciter filter 15 into the optical path.
[0030]
【Effect of the invention】
As described above, the ophthalmologic photographing apparatus according to the present invention converts an image with a setting suitable for the photographing mode, so that a preferable image can be obtained in any photographing mode and a more advanced diagnosis is possible.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of an ophthalmologic photographing apparatus.
FIG. 2 is a flowchart showing a procedure for outputting image data.
FIG. 3 is an explanatory diagram of a fundus image of a subject's eye.
FIG. 4 is a characteristic diagram of a look-up table set for a color photographed image.
FIG. 5 is a characteristic diagram of a look-up table set for a fluorescent photographed image.
FIG. 6 is a characteristic diagram of a histogram of luminance of the entire fundus image.
[Explanation of symbols]
6 Imaging means 10 Television camera 11 Observation light source 14 Imaging light source 20 A / D conversion unit 21 Frame memory 22 Look-up table 23 Look-up table setting unit 25 Recording medium 26 Image control unit 27 Control circuits 30 and 32 TV monitor

Claims (3)

An acquisition means for acquiring an image signal representing a still image of the eye to be examined in any of the imaging modes of fluorescence imaging and color imaging;
In the case of the fluorescent photographing, the image signal is converted by a first look-up table indicating the first gradation conversion characteristic for the fluorescent photographing, while the first gradation is selected when the color photographing is selected. Conversion means for converting the image signal with a second look-up table showing a second gradation conversion characteristic for color photographing, which is a characteristic different from the conversion characteristic ,
Each of the first look-up table and the second look-up table includes a pre-conversion luminance value that is a luminance value of an image signal before conversion by the conversion unit and a luminance value of the image signal after conversion by the conversion unit. Is associated with a certain converted luminance value,
In the first look-up table, the range of the luminance value before conversion is a first range from the minimum luminance value to the first luminance value and a luminance value from the first luminance value to the luminance value that is higher than the first luminance value. A second range up to a high second luminance value and a third range from the second luminance value to a maximum luminance value, wherein the first look-up table is the conversion in the second range. The change in the converted luminance value with respect to the change in the previous luminance value is larger than the change in the converted luminance value with respect to the change in the pre-conversion luminance value in each of the first range and the third range. While the pre-conversion luminance value and the post-conversion luminance value are associated,
In the second look-up table, the range of the pre-conversion luminance value is a fourth range from the minimum luminance value to the third luminance value, and a luminance value from the third luminance value to the third luminance value. And a sixth range from the fourth luminance value to the maximum luminance value, and the second lookup table includes a fifth range up to a fourth luminance value having a high The change in the post-conversion luminance value with respect to the change in the pre-conversion luminance value is larger than the change in the post-conversion luminance value with respect to the change in the pre-conversion luminance value in each of the fourth range and the sixth range. As described above, the luminance value before conversion and the luminance value after conversion are associated with each other,
Said fifth range, ophthalmic photographing equipment, which is a range included in the second range. Wherein the first luminance value is less than the third luminance value, the second luminance value ophthalmologic photographing apparatus according to claim 1, wherein a greater than the brightness value of the fourth. The difference between the first gradation conversion characteristic and the second gradation conversion characteristic is based on a difference between a still image characteristic in the fluorescent photographing and a still image characteristic in the color photographing. The ophthalmologic photographing apparatus according to claim 1 or 2 .