JPS6350011B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a light amount correction device when a photographing light source (for example, a strobe tube) used in a fundus camera or the like deteriorates due to clouding or the like.

For example, a strobe tube used when photographing an object with an ophthalmological optical device such as a fundus camera becomes cloudy after being emitted thousands of times. When taking photographs with a fundus camera or the like, if the strobe tube becomes cloudy, there will be insufficient light, but even if the insufficient light becomes clear after taking a photograph, it will not be possible to take another photograph. When the amount of light emitted from a strobe tube becomes insufficient due to deterioration such as clouding, conventionally, in order to correct this, the amount of light is increased based on intuition or the tube itself is replaced. However, replacing the tube is not only dangerous due to high pressure, but also requires aligning the optical axes after replacement, which is cumbersome.

In the present invention, a light-receiving element is placed near the strobe tube, and the light-receiving element detects light transmitted through the strobe tube or light reflected by the strobe tube, and activates an auxiliary condenser etc. when the strobe tube deteriorates. The present invention provides a light amount correction device for a photographing light source that corrects insufficient light amount.

The specific contents of the present invention will be explained below based on the illustrated embodiments. FIG. 1 shows an example in which the light amount correction device of the present invention is applied to a fundus camera, in which illumination light emitted from an observation light source 1 is reflected by a half mirror 4 by a condensing lens 2, the optical path is bent, and is projected onto a ring slit 5. Ru. The optical path of the light passing through the ring slit 5 is bent by a reflecting mirror 6, and a ring image is formed near a perforated reflecting mirror 8 by a relay lens 7.
Further, an image is formed near the cornea of the eye to be examined by the objective lens 9, and the fundus of the eye to be examined is illuminated. The thus illuminated fundus is observed using a well-known method. On the other hand, when a photographic light source 3 such as a strobe tube emits flash light instantaneously, it is projected onto a ring slit 5 after being transmitted through a half mirror 4 by a condensing lens 2'. Thereafter, the photographing light passing through the ring slit 5 illuminates the fundus of the eye to be examined in exactly the same manner as the observation light.
In this way, the fundus of the eye is photographed.

The above is the optical system of a general fundus camera. In the light amount correction device of the present invention, a light emitting element 13 and a light receiving element 14 are further arranged with the photographing light source 3 in between.

FIG. 5 is a detailed view of the vicinity of the photographing light source 3 in the optical system of FIG. As mentioned above, near the photographic light source 3, there are light emitting elements 1 at almost symmetrical positions on both sides thereof.
3 and a light receiving element 14 are arranged, and a light emitting element 1
3, visible light or near-infrared light is emitted. This light passes through the photographing light source 3 and is received by the light receiving element 13. Here, it is converted into an electric signal, amplified by an amplifier circuit 16, and calculated by a comparison amplifier 17, and a reference voltage 18
compared to This reference voltage E _S is set to a value that requires light amount correction when the voltage E _S of the detected electric signal is less than this value. Therefore, if the photographing light source 3 is not cloudy, the amplified electric signal E _S and the reference voltage E _R have a relationship of E _R ≦E _S , and the switch control 19 is not activated and the switch 20 remains open. Therefore, the auxiliary capacitor 22 is not charged, but only the capacitor 21 is charged. On the other hand, if the photographing light source 3 becomes cloudy and the amount of transmitted light decreases, the output of the light receiving element decreases and E _S <E _R. In this case, switch control 19 operates and switch 20
closes. Therefore, the auxiliary capacitor 22 is also charged.

In this way, when the photographing light source 3 is not cloudy, only the capacitor 21 is charged, and the light emission control circuit 23 emits light at the normal amount of light. Further, when the photographing light source 3 becomes cloudy, the switch 20 is closed as described above, the auxiliary capacitor 22 is also charged, and light is emitted with the amount of light corrected by the light emission control circuit 23. Therefore, the influence of cloudiness and the like is corrected, and photography is performed under correct exposure conditions.

FIG. 2 shows a case where the present invention is applied to another fundus camera that is a modification of the optical system shown in FIG.
and the photographing light beam 3 are arranged in a straight line, and the light from the observation light source 1 is condensed at the position of the photographing light source 3 by a condenser lens 10 and then further condensed onto the ring slit 5 by a condenser lens 11. It differs from FIG. 1 in that it has been changed to 1, but is substantially the same in other respects. A light emitting element 13 and a light receiving element 14 are arranged near the photographing light source 3, and the photographing light source (stroboscopic tube)
The degree of cloudiness is detected, and if it is necessary to correct the amount of light based on it, the amount of light is automatically corrected by the circuit shown in FIG. 5 as described above.

In the examples shown in FIGS. 1 and 2, clouding was detected by detecting light transmitted through a strobe tube. However, as shown in FIG. 3, even if the light emitting element 13 and the light receiving element 14 are arranged on the same side of the photographing light source 3, the reflected light from the photographing light source 3 is detected, cloudiness is detected, and the light amount is corrected. good.

FIG. 4 shows a system in which white turbidity is detected using only a light-receiving element without using a light-emitting element. In other words, in place of the reflecting mirror 6 used in the optical system shown in FIG. 1, a dichroic mirror 12 or the like that transmits infrared rays and reflects visible rays is used, and a light receiving element 14 is placed near it. It is. According to such an optical system, the light emitted from the photographing light source 3 is reflected by the mirror 12, but the infrared light is reflected by the mirror 12.
2 and detected by the light-receiving element 14, the cloudy state at that time can be detected, and the amount of light can be corrected based on this.

As explained above, according to the present invention, even if the photographing light source becomes cloudy, the light amount is automatically increased to correct the insufficient light amount, so that photography can always be performed with the correct exposure amount. Furthermore, even if the photographing light source deteriorates, it does not need to be replaced immediately, and the replacement period becomes longer, thereby eliminating the need for dangerous and troublesome replacement work.

[Brief explanation of drawings]

1 and 2 are diagrams showing the optical system of a fundus camera to which the device of the present invention is applied, and FIG. 3 is a diagram showing another example of the arrangement of the light emitting element and light receiving element used in the device of the present invention, FIG. 4 is a diagram showing an example in which only a light receiving element is used in the device of the present invention, and FIG. 5 is a diagram showing the entire configuration including the circuit used in the present invention. 3...Photography light source, 13...Light emitting element, 14...
Light receiving element, 16...Amplification circuit, 17...Comparison amplifier, 18...Reference voltage, 19...Switch control, 20...Switch, 21...Capacitor, 22...Auxiliary capacitor, 23...Light emission control circuit.

Claims (1)

[Claims] 1. In ophthalmological optical instruments that have a photographic light source such as a fundus camera or a slit lamp, detect deterioration of the photographic light source such as cloudiness based on the amount detected by a light-receiving element placed near the photographic light source, and based on this detection. A light amount correction device for a photographing light source, characterized in that the light amount of the photographing light source is increased by operating an auxiliary condenser or the like.