JPH04231930A - Ophthalmic image pickup device - Google Patents

Abstract

PURPOSE:To obtain the ophthalmic image pickup device capable of simply correcting color shading by storing a specific correction coefficient of an area at every prescribed area of an image pickup image, and correcting a video signal outputted from each image pickup element by its correction coefficient. CONSTITUTION:Each color light subjected to color resolution by a color resolution optical system is made incident on CCDs 101-103, respectively, and converted to an electric potential at every picture element of the CCDs 101-103. This electric potential of every picture element of the CCDs 101-103 is read out successively by a clock pulse supplied from an arithmetic control circuit 114, amplified by amplifiers 104-106, respectively, and converted to a digital signal by A/D converters 107-109. On the other hand, from a memory 115, a correction coefficient of every area of each color signal of an image pickup image is called by the arithmetic control circuit 114 and supplied to correcting circuits 110-112, outputted from the A/D converters 107-109, and a digital video signal is corrected at every color signal and at every area.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ophthalmological photographing apparatus capable of avoiding color shading.

0002

2. Description of the Related Art Conventionally, as shown in FIG. 6, an ophthalmological photographing apparatus using a three-plate color separation optical system has been known. In FIG. 6, 1 is a color separation optical system. This color separation optical system 1 has three prisms 2, 3, and 4. Part 3
The prisms 2, 3, and 4 are pasted together. There is a slight air layer between prisms 3 and 4. An interference film 5 is formed on the bonding surfaces of the prisms 2 and 3. An interference film 6 is formed on the surface of the prism 4 on which the prisms 3 and 4 are bonded together. This interference film 5,
6 plays the role of a dichroic filter,
The light beam incident on this color separation optical system 1 is transmitted through its interference film 5,
The light beams are separated into red (R), green (G), and blue (B) light rays by the transmission/reflection characteristics of 6, and are guided to the imaging surfaces of CCDs 7, 8, and 9 as image sensors to form images. . C.C.
D7, 8, and 9 output R, G, and B signals according to the amount of light received.

However, in general, the reflection and transmittance of the interference films 5 and 6 change when the inclination of the light rays incident on the color separation optical system 1 with respect to the interference film changes, and the light rays incident on the color separation optical system 1 change in reflection and transmittance. The greater the inclination of the light beam with respect to the interference film, the more the transmittance characteristics shift toward shorter wavelengths.

[0004] Here, assuming that the image output by the light beam formed at the center of the CCDs 7, 8, and 9 is balanced, the CCDs 7, 8 at oblique incidence (for example, at an angle θ) with respect to the photographing optical axis 10. , 9, since the transmission/reflectance characteristics of the interference films 5, 6 are different from the reflection/transmittance characteristics for the light rays forming images at the center of the CCDs 7, 8, 9. , for the light rays that form the peripheral image, the CCD
The output balance of 7, 8, and 9 is disrupted, and a so-called color shading phenomenon occurs in which color unevenness appears at the periphery of the television screen.

That is, when focusing on the chief ray, the inclination angles of the interference films 5 and 6 with respect to the chief ray are as follows:
This is because the conditions are different between the central part and the peripheral part of 9.

Therefore, in color television cameras and the like having this three-plate color separation optical system 1, a color shading correction circuit is incorporated into the signal processing unit, and the position of the exit pupil is adjusted based on various conditions such as the magnification of the optical system and the aperture diaphragm. decide,
The angle of incidence of the chief ray with respect to the photographing optical axis 10 among the light rays incident on the color separation optical system 1 is calculated, and this calculated value is converted into R, G,
Color shading correction is performed using this as the correction amount for each pixel of each CCD 7, 8, and 9 corresponding to B.

[0007]

However, the former color television camera has the disadvantage that its signal processing unit is large and that the color balance must be set again every time the photographing conditions are changed. On the other hand, the latter color television camera requires an arithmetic circuit, and therefore has the disadvantage of being expensive.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an ophthalmologic photographing apparatus that can easily perform color shading correction by providing a simple correction means.

[0009]

[Means for Solving the Problems] In order to achieve the above object, the ophthalmological photographing apparatus according to the present invention is characterized in that the ophthalmological photographing apparatus uses a three-panel color camera having three imaging elements as an imaging means. a storage means that stores correction coefficients specific to each predetermined region of an image; a correction means that corrects a video signal output from each of the image pickup devices using the correction coefficients stored in the storage means; The present invention is characterized by comprising a reproducing means for reproducing the video signal corrected by the means.

Further, the correction means of the ophthalmologic photographing apparatus of the present invention is characterized in that it is a multiplication means for multiplying the video signal output from each image sensor by a correction coefficient.

[0011]

[Operation] According to the ophthalmological photographing apparatus according to the present invention, a correction coefficient specific to each predetermined region of a captured image is stored, and the video signal output from each image sensor is corrected using the correction coefficient. Therefore, the video signal can be circuit-corrected for each region of the captured image, and the color shading phenomenon can be avoided with a simple configuration.

Furthermore, if the correction means is a multiplication circuit, the level of the video signal can be corrected simply by multiplying the video signal by a correction coefficient, and a reproduced image with good color balance without color shading can be obtained.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the circuit configuration of this embodiment, and FIG. 2 is a diagram showing a state in which an imaging screen is divided into a plurality of areas and correction coefficients are set. 3 to 5 show the optical system of this example, FIG. 3 is a diagram showing its configuration, FIG.
FIG. 5 is a diagram for explaining the effect.

In FIG. 1, 101 to 103 are CCDs used as image pickup devices.
The video signals outputted from the amplifiers 104 to 106 are inputted to amplifiers 104 to 106, respectively. The output signals of amplifiers 104-106 are
A/D converter 1 that converts analog signals to digital signals
Input from 07 to 109. The output signal of the A/D converter is corrected for each area of the captured image by correction circuits 110 to 110.
112. Correction coefficients for each area of the captured image are stored in a memory 115, and data stored in the memory 115 is read out from the arithmetic control circuit 114 and supplied to each correction circuit 110-112.

The memory 115 stores an image capture screen at 20 in FIG.
It is divided into regions such as 1 to 205, and correction coefficients are stored in advance for each divided region and for each color signal. That is, the correction coefficients are the same within each image area for the same color signals 201 to 205.

The video signals corrected by each of the correction circuits 110 to 112 are input to an image reproduction circuit 113 that converts the digital video signal into an analog video signal, synthesizes each color signal, and outputs the signal as a full-color video signal. . The output signal of the image reproduction circuit 113 is displayed on a monitor 116 such as a CRT.

Although not shown, the arithmetic control circuit 1
14, read clock pulses for CCDs 101 to 103, clock pulses for A/D conversion of A/D converters 107 to 109, clock pulses for D/A conversion of image reproduction circuit 113, video synchronization signals, etc. signals are supplied to each circuit.

Further, when the magnitude of color shading for each color signal is not much different, the correction circuits 110 to 110
Only one signal 112 may be provided, and the correction may be performed after combining each color signal. Next, the operation of this embodiment will be explained.

Each color light separated by the color separation optical system shown in FIG. 6 enters the CCDs 101 to 103,
Each pixel from 01 to 103 is converted into an electric potential. The electric potential of each pixel of the CCDs 101 to 103 is sequentially read out by clock pulses supplied from the arithmetic control circuit 114, and
The signals are each amplified by A/D converters 107 to 109 and converted into digital signals.

On the other hand, the correction coefficients for each area (areas 201 to 205 in FIG. 2) of each color signal of the captured image are called out from the memory 115 by the arithmetic control circuit 114 and supplied to the correction circuits 110 to 112, and the A/ D converter 107-1
The digital video signal output from 09 is corrected for each color signal and for each region.

When a multiplication circuit is used as this correction circuit, the voltage level of each region of each color signal is multiplied by a correction coefficient for correction.

The digital video signals corrected by the correction circuits 107 to 109 are converted into analog signals by the image reproduction circuit 113 and then synthesized, and horizontal and vertical synchronization signals, color burst signals, etc. The signal is converted into a video signal and displayed on the monitor 116.

When only one correction circuit is used, the image reproduction circuit 113 combines each color signal as a digital signal, and then corrects each area as a combined color signal.

FIGS. 3 to 6 show an example of an optical system when the ophthalmologic photographing apparatus of this embodiment is attached to a fundus camera.

In FIG. 3, A is an illumination optical system, and B is a photographing optical system. The illumination optical system A is roughly composed of a concave mirror 11, a halogen lamp 12 for observation illumination, a relay lens 13, a xenon tube 14 for photography illumination, a condenser lens 15, a reflection mirror 16, a ring-shaped slit 17, and a relay lens 18. The light is guided to the fundus R of the eye 21 to be examined via the perforated mirror 19 and the objective lens 20, and the fundus R is illuminated.

The photographing optical system B includes a focusing lens 22, an imaging lens 23, a variable magnification lens 24, and a quick return mirror 25.
, a field lens 26, a reflecting mirror 27, a relay lens 28 for TV, and a color separation optical system 1. The perforated mirror 19 and the objective lens 20 are the illumination optical system A and the photographic optical system B.
It is shared by The quick return mirror 25 is connected to the photographing optical system B when forming the fundus image on the film 29.
evacuated from the optical path. The variable magnification lens 24 has an angle of view of 2
It is inserted into the optical path of the photographing optical system B when 0° is selected.

The photographing optical system B of this fundus camera is shown in FIG.
This is simplified as shown in FIG. In FIGS. 4 and 5, the same components as the optical elements shown in FIG. 3 are given the same reference numerals. FIG. 4 is an optical path diagram when the angle of view is 45 degrees, and FIG. 5 is an optical path diagram when the angle of view is 20 degrees.

FIG. 4 shows principal rays when photographing the fundus R at an angle of view of 45°, and the fundus R is once formed as an aerial image 30 by the objective lens 20. The chief ray forming the aerial image 30 passes through the center 31' of the hole 31 of the perforated mirror 19, which functions as an aperture stop, is guided to the focusing lens 22 and the imaging lens 23, and returns before the field lens 26. The image is formed as an aerial image 32 and guided to the color separation optical system 1.

At this time, for example, the inclination angle of the principal ray 33 contributing to image formation in the peripheral area of the screen with respect to the interference film 5 and the principal ray 34 (coinciding with the photographing optical axis 10) contributing to image formation in the central area of the screen are determined. The inclination angle with respect to the interference film 5 is different, for example, C
The transmission/reflectance characteristics of the interference film for the light beam that forms an image at the center of the CD 8 are different from the transmission/reflectance characteristics of the interference film for the light beam that forms an image around the CCD 8, resulting in color shading. Become.

The light beam guided to the color separation optical system 1 passes through the interference film 5.
, 6, and is guided to CCDs 7, 8, and 9. When photographing the fundus R at an angle of view of 20°, the variable magnification lens 24
is inserted into the optical path of the photographing optical system 2.

In addition, in FIGS. 4 and 5, 35, 3
5' is the exit pupil of each optical system. Therefore, depending on whether or not the variable magnification lens 24 is inserted into the optical path, the positions of the exit pupils 35 and 35' change, and the angle of incidence on the CCD 8 changes, so the degree of color shading also changes.

Therefore, the correction coefficients stored in the memory 115 are appropriately selected depending on the presence or absence of the variable magnification lens 24.
The data is transferred to the arithmetic control circuit 114.

Color shading also occurs when the focusing lens 22 moves. Therefore, as shown in FIGS. 4 and 5, a position detection sensor 36 for detecting the position of the focusing lens 22 is provided near the focusing lens 22, and color shading is performed by detecting changes in the position of the focusing lens 22. The correction coefficient may be changed.

[0035]

[Effects of the Invention] Since the ophthalmological imaging device of the present invention is configured as described above, color shading correction can be easily performed with a simple circuit configuration, and there is no need to readjust it even when imaging conditions differ. Easy to handle.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a circuit configuration of an embodiment of the present invention.

FIG. 2 is a diagram showing a state of region division of a captured image according to an embodiment of the present invention.

FIG. 3 is a diagram showing an optical configuration of an embodiment of the present invention.

FIG. 4 is an optical path diagram for explaining a color shading phenomenon.

FIG. 5 is an optical path diagram for explaining a color shading phenomenon.

FIG. 6 is a diagram showing a three-plate color separation optical system.

[Explanation of symbols]

101-103, 7, 8, 9 CCD107-109
A/D converters 110 to 112 Correction circuit 113 Image reproduction circuit 114 Arithmetic control circuit 115 Memory 1 Color separation optical system 5, 6 Interference film 10 Photographing optical axis 26 Field lenses 33, 33', 34 Chief ray

Claims (2)

[Claims] Claims: 1. An ophthalmological photographing apparatus using a three-panel color camera having three imaging elements as an imaging means, comprising: a storage means for storing a correction coefficient specific to each predetermined region of a captured image; Ophthalmologic photography characterized by comprising a correction means for correcting the video signal output from each of the image pickup devices using a correction coefficient stored in the means, and a reproduction means for reproducing the video signal corrected by the correction means. Device. 2. The ophthalmologic photographing apparatus according to claim 1, wherein the correction means is a multiplication means that multiplies the video signal output from each image sensor by a correction coefficient.