JP2007007044A - Ophtalmic photographing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a sufficient sensitivity and a high-quality image without undermining operability. <P>SOLUTION: A position adjustment of an optical system is started at timing A and a movable section starts to move. When a travel distance reaches a threshold L or higher at timing B, a frame rate of an image signal is switched into a high speed in order to make it easy to observe a moving image. Next, a rough position adjustment is completed at timing C, and the travel distance of the movable section falls to the threshold L or lower. At this point, by switching the frame rate into a low speed, a further fine adjustment of a fundus camera and a detailed observation of a lesion can be performed at high sensitivity. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an ophthalmologic photographing apparatus used in an ophthalmic hospital or the like.

  Conventionally, fluorescent fundus imaging (ICG imaging) using indocyanine green has been known as an imaging method using an ophthalmologic imaging apparatus, particularly a fundus imaging apparatus. Since this ICG imaging is performed in the infrared region, alignment and observation imaging are performed using a camera having sensitivity in the infrared region. In ICG photography, reflected light is very weak, and the sensitivity is often insufficient with a normal camera, and devices such as using an expensive high-sensitivity camera or illuminating with a high amount of light have been devised. As for ICG photographing, Patent Document 1 discloses a method of photographing a still image using a strobe light source after completion of alignment and a method of recording an observation image as it is without using a strobe light source.

  On the other hand, as one of camera-related technologies, a method of reducing the frame rate is known as a method of improving sensitivity while relatively suppressing noise. This is a method of improving the visual sensitivity by extending the charge accumulation time of the image sensor by lowering the frequency of the charge reading cycle from the image sensor.

  Also, based on the same concept, a process called frame addition is known. This is a method of creating video data for one frame by adding a plurality of frames of frame data corresponding to data for one screen read from the image sensor. Even with this method, it is possible to increase sensitivity while relatively suppressing noise.

Japanese Patent No. 3591947

  However, illuminating the subject's eye with a large amount of light is not preferable because it increases the burden on the patient. As a method for improving the visual sensitivity of the camera, it is known to increase the amplification factor, but if it is excessively increased, noise may increase, which may hinder alignment and observation. In addition, when moving image recording is performed, there is a possibility of causing trouble in direct diagnosis.

  For this reason, there is a need for a method for improving sensitivity while relatively suppressing noise. However, the above-described methods for reducing the frame rate and performing frame addition reduce the number of frames generated per unit time, and naturally In addition, the number of frames per unit time displayed on the display device is reduced. When the number of displayed frames is reduced, the display is uncomfortable and awkward for a subject with large movement. This awkward image is a major obstacle to the alignment operation of the ophthalmologic photographing apparatus.

  An object of the present invention is to provide an ophthalmologic photographing apparatus that solves the above-mentioned problems, reduces the burden on the subject, obtains a high-quality image with less noise, and is excellent in operability.

  The technical features of the ophthalmologic photographing apparatus according to the present invention for achieving the above object are optical means for guiding an eye image to be examined, imaging means for photoelectrically converting the guided eye image, and an image from the output of the imaging means. In an ophthalmologic photographing apparatus having a signal processing means for generating data and a movable part for aligning the optical means with respect to the eye to be examined, a state detecting means for detecting the state of the movable part, and the state detecting means And an accumulation variable means for varying the accumulation time in the photoelectric conversion of the imaging means in accordance with the output of the image pickup means.

  The technical features of the ophthalmologic photographing apparatus according to the present invention include: an optical unit that guides an eye image to be examined; an imaging unit that photoelectrically converts the guided eye image; and a signal that generates video data from an output of the imaging unit In an ophthalmologic photographing apparatus having a processing unit and a movable unit that aligns the optical unit with respect to an eye to be examined, a state detection unit that detects a state of the movable unit, and an output from the state detection unit The signal processing means includes processing control means for controlling addition processing.

  According to the ophthalmologic photographing apparatus according to the present invention, there is an advantage that a high-sensitivity and high-quality image sufficient for observation and diagnosis can be obtained without impairing operability such as positioning, noise is reduced, and the patient burden can be reduced. is there.

  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 present embodiment, and a movable unit 2 that can move is placed on a base 1. An objective lens 3 is provided in the movable portion 2 so as to face the eye E to be examined. Behind the objective lens 3, a perforated mirror 4, a focusing lens 5, a photographing lens 6, and an optical path are detachably disposed. An infrared fluorescence barrier filter 7 that blocks excitation light and transmits only fluorescence and an image sensor 8 are sequentially arranged to constitute a fundus photographing optical system.

  In the incident direction of the illumination light with respect to the perforated mirror 4, a relay lens 9, an infrared fluorescent exciter filter 10 that can be inserted into and removed from the optical path, a diaphragm 11 having a ring-shaped opening, a mirror 12, a photographing light source 13, and a condenser lens 14. The observation light source 15 is arranged to constitute a fundus illumination optical system.

  The output of the image sensor 8 is connected to a system control unit 18 provided in the base 1 via an accumulated charge reading unit 16 and a video signal processing unit 17. Further, the output of the video signal processing unit 17 is connected to a display unit 19 provided on the side surface of the movable unit 2 in order to observe the fundus Er of the eye E and display a captured image. The movable portion 2 is a movable mechanism for moving and aligning the above-described optical system with respect to the eye E, and the base 1 has a movable portion state detecting means for detecting the movement of the movable portion 2. 20 is provided, and its output is connected to the system controller 18.

  In the present embodiment, it is assumed that the movable part state detecting means 20 detects the position information of the movable part 2. For example, the moving part state detecting means 20 outputs a pulse by outputting the movement amount of the movable part 2 using a three-axis encoder or the like. Is measured and output to the system control unit 18. The system control unit 18 can detect the relative change amount by periodically reading the count value.

  The light beam emitted from the observation light source 15 passes through the condenser lens 14 and the photographing light source 13, is reflected by the mirror 12, and passes through the aperture 11 having a ring-shaped opening, the infrared fluorescent exciter filter 10, and the relay lens 9. The light is reflected around the perforated mirror 4 and passes through the objective lens 3 and the pupil Ep of the eye E to illuminate the fundus Er. The fundus image illuminated by the illumination light from the observation light source 15 passes through the pupil Ep of the eye E, the objective lens 3, and the aperture of the perforated mirror 4, the focusing lens 5, the imaging lens 6, and the infrared fluorescent barrier filter 7. And imaged on the image sensor 8.

  The image sensor 8 holds the accumulated charge after photoelectric conversion, and the accumulated charge reading unit 16 outputs the read signal to the video signal processing unit 17 while continuously reading the accumulated charge accumulated in the image sensor 8. . The video signal processing unit 17 has a timing generator (not shown), and is configured to be able to change the reading frequency of the stored charge reading unit 16. It is displayed on the display unit 19. When recording a moving image, the output of the video signal processing unit 17 is recorded in a recording unit (not shown).

  2A shows a waveform of a normal analog video signal output generated by the video signal processing unit 17, and FIG. 2B shows an analog video signal waveform when the frequency is halved. The signal has a double cycle, the charge accumulation time in the image sensor 8 is almost doubled, and the output of the video signal is also almost doubled. By performing such processing, it is possible to improve the sensitivity of the image pickup device 8 by a factor of 2 and to obtain substantially the same output. The video signal processing unit 17 can perform the same timing control on the display unit 19 to display both videos shown in FIG.

  FIG. 3 is an explanatory diagram of a control method for switching the frame rate of the video signal in accordance with the amount of movement of the movable unit 2. The horizontal axis represents timing, and the vertical axis represents the relative movement amount of the movable unit 2, and the value of the vertical axis increases as the relative movement amount increases. An alternate long and short dash line indicates a threshold value L for switching the frame rate.

  First, when the alignment of the optical system is started at timing A, the movable unit 2 starts to move, and when the moving amount is equal to or greater than the threshold L at timing B, the frame rate is switched at a high speed so that the moving image can be easily observed. This corresponds to the waveform of FIG. Next, rough alignment is completed at timing C, and the amount of movement of the movable part 2 becomes the threshold value L or less. Here, by switching the frame rate to a low speed corresponding to FIG. 2B, the subsequent fine adjustment and detailed observation of the lesion can be performed with high sensitivity.

  In FIG. 3, an example in which the frame rate is switched in two stages according to the amount of movement of the movable part 2 has been shown. However, by increasing the number of stages for switching the frame rate, the inspector does not feel uncomfortable and smoother. Control becomes possible.

  FIG. 4 shows an explanatory diagram of a second embodiment which is a control method for performing smooth control without any sense of incongruity. The video signal processing unit 17 has means for amplifying the accumulated charge obtained from the image sensor 8 and is amplified between timings B to C in order to compensate for visually dark images by switching the frame rate at high speed. The rate is increasing. As a result, it is possible to compensate for the apparent luminance change of the video signal, and it is possible to obtain a good image quality with less noise during fine adjustment and detailed observation of the lesioned part by reducing the unnaturalness of the luminance difference.

  Similarly, the system control unit 18 may increase the light amount of the observation light source 15 between the timings B to C. By increasing the amount of light, the apparent luminance change of the video signal due to the frame rate switching is compensated, and by reducing the amount of light when the alignment is almost completed, observation with a low amount of light that is easy on the patient becomes possible.

  FIG. 5 shows an explanatory diagram of Embodiment 3 of the control method when the frame rate is made constant. The video signal processing unit 17 adds the signals obtained from the image sensor 8 at timings A and B, and continuously outputs the addition result at timings C and D. Further, the signals obtained from the image sensor 8 at timings C and D are added and output at timings D and F. By repeating this, it is possible to obtain a double video signal. Further, this method has an advantage that the control method of the display unit 19 is not changed.

  FIG. 6 is an explanatory diagram for controlling whether or not to perform frame addition in accordance with the amount of movement of the movable unit 2. By switching whether or not to perform frame addition at the threshold value L of the movement amount at timings B and C, when the movement amount is large, it is easy to see an image with intense movement and select no frame addition that is easy to align, When the amount of movement is small, “with frame addition” is selected so that a video output sufficient for detailed observation can be obtained.

  In this method as well, the apparent luminance on the display unit 19 changes greatly with the threshold value L as a boundary. In order to compensate for the uncomfortable feeling of the luminance difference, it can be similarly solved by combining with the control of the amplification factor and the amount of observation light described above.

  FIG. 7 shows a fourth embodiment in which all of the frame rate, the amplification factor, and the light amount control are combined. The frame rate uses three types of high, medium, and low, and the amplification rate and light amount use two types of medium and low.

  First, at the timing A, when the movement amount exceeds the threshold L1, the frame rate is changed from low speed to medium speed, and the amplification factor is changed from low level to medium level in order to compensate for the luminance change with respect to the display unit 19. Then, when the alignment is started at the timing B and the moving amount of the movable part 2 exceeds the threshold value L2, the frame rate is set to a high speed optimum for rough alignment and the light amount is set to the medium level.

  Next, at timing C when the rough alignment falls below the threshold value L2 toward convergence, the frame rate is changed to medium speed to facilitate fine adjustment of alignment, and in order to compensate for the luminance change with respect to the display unit 19, amplification is performed. By reducing the rate to a low level, fine adjustment is facilitated by improving the image quality. Furthermore, the frame rate is lowered to a low speed at the timing D when it becomes the threshold value L1 or less for entering the detailed observation of the lesioned part. Again, in order to compensate for the luminance change on the display unit 19, the load on the patient is reduced by changing the amount of light from medium to low.

  As described above, by controlling the frame rate, amplification factor, and amount of light together, it is possible to obtain images that are easy to see even in the case of rough alignment with intense movements. Further, the amplification factor control improves image quality and reduces the burden on patients. It becomes possible to do.

  In FIG. 7, if the frame rate control is replaced with the frame addition processing described in FIG. 5 and replaced with no frame addition, two frame addition, and three frame addition, the same effect can be obtained without changing the control method to the display unit 19. Obtainable.

  In the present embodiment, the movement amount is detected by the movable portion state detection means 20, but the same effect can be obtained even if an acceleration sensor or the like is used.

  In addition, the charge accumulation time of the image sensor 8 is controlled by changing the frame rate. However, if the sensitivity is originally sufficient, if the charge accumulation time is controlled within one frame by the shutter function or the like, the movement is further increased. A high-quality image with little shake can be obtained even in severe cases.

  In this embodiment, the video signal output is described as an analog signal for convenience, but the same effect can be obtained even if the output of the image sensor 8 is A / D converted and subjected to amplification processing or frame addition processing. Needless to say.

  Further, although preferred embodiments have been described, it goes without saying that the present invention is not limited to these embodiments, and various modifications and changes can be made within the scope of the gist thereof.

1 is a configuration diagram of a fundus camera in Embodiment 1. FIG. It is explanatory drawing of the video signal process of Example 1. FIG. It is explanatory drawing of the control method of Example 1. FIG. It is explanatory drawing of the control method of Example 2. FIG. It is explanatory drawing of the video signal process of Example 3. FIG. It is explanatory drawing of the control method of Example 3. FIG. It is explanatory drawing of the control method of Example 4. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Base 2 Movable part 3 Objective lens 4 Perforated mirror 7 Infrared fluorescent barrier filter 8 Imaging element 10 Infrared fluorescent exciter filter 13 Imaging light source 15 Observation light source 16 Accumulated charge reading part 17 Video signal processing part 18 System control part 18 System control part 19 Display part 20 Movable part state detection means

Claims (7)

  Optical means for guiding the eye image to be examined, imaging means for photoelectrically converting the guided eye image, signal processing means for generating video data from the output of the imaging means, and alignment of the optical means with respect to the eye to be examined In an ophthalmologic photographing apparatus having a movable part that performs the above, a state detection unit that detects a state of the movable part, and a storage variable that varies a storage time in photoelectric conversion of the imaging unit according to an output from the state detection unit And an ophthalmologic photographing apparatus.   Optical means for guiding the eye image to be examined, imaging means for photoelectrically converting the guided eye image, signal processing means for generating video data from the output of the imaging means, and alignment of the optical means with respect to the eye to be examined In an ophthalmologic photographing apparatus having a movable part that performs the above, a state detection unit that detects a state of the movable part, and a process control unit that performs addition processing control in the signal processing unit according to an output from the state detection unit An ophthalmologic photographing apparatus characterized by comprising.   The ophthalmologic photographing apparatus according to claim 1, further comprising an illuminating unit that illuminates the eye to be examined, and controlling an illumination light amount of the illuminating unit in accordance with an output from the state detecting unit.   3. The signal processing means according to claim 1, wherein the signal processing means has amplification means for amplifying a signal from the imaging means, and changes an amplification factor of the amplification means in accordance with an output from the state detection means. The ophthalmic imaging apparatus described.   Illuminating means for illuminating the eye to be examined, and the signal processing means has amplification means for amplifying the signal from the imaging means, and the amount of illumination light from the illuminating means is adjusted according to the output from the state detecting means. The ophthalmologic photographing apparatus according to claim 1, wherein the ophthalmic imaging apparatus is controlled to change an amplification factor of the amplification unit.   The ophthalmologic photographing apparatus according to claim 1, wherein the state detection unit detects position information of the movable part.   The ophthalmologic photographing apparatus according to any one of claims 1 to 5, wherein the state detection unit detects acceleration information of the movable part.

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