JPH04289833A - Strobo photographing device - Google Patents

Abstract

PURPOSE:To fixedly hold an object injection light amount even in the case of changing driving voltage of a strobo photographing light source. CONSTITUTION:At photographing time, the eyeground image is recorded in a film 15 by emitting light of a photographing light source 3. In the photographing light source 3, light is emitted by discharging light emitting energy, with which a main capacitor in the inside of a light emitting power supply 21 is charged, to the photographing light source 3 through a light emitting circuit 19. Since charge voltage is decreased in the case of an extremely short light emitting interval, the charge voltage is detected by a voltage detecting circuit 23 to change light emitting time so that the light emitting energy, discharged to the photgraphing light source 3, is always fixedly generated, and the light emitting circuit 19 and a light emission stopping circuit 20 are controlled by an arithmetic circuit 22.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a strobe photographing apparatus such as a fundus camera used, for example, in an ophthalmological clinic.

0002

2. Description of the Related Art Some conventional strobe photographing devices manually adjust the amount of photographing light by considering only the sensitivity of the film used and the photographing magnification. However, for example, in the case of a fundus camera, the amount of pigment contained in the fundus varies depending on racial differences.
The reflectance of the fundus, which is the object to be photographed, changes, and the amount of reflected light from the fundus may change depending on the degree of mydriasis, etc.
Furthermore, there are other causes such as a decrease in the amount of light emitted by the photographing light source over time, so it is very difficult to manually adjust the exposure to take photographs with an appropriate amount, and the operation is also troublesome.

[0003] Therefore, for example, Special Publication No. 54-158093
As disclosed in Japanese Patent Application Publication No. 2003-110023, there has been proposed a device that incorporates a control means that measures the amount of light reflected from the subject and automatically adjusts the amount of exposure to be an appropriate amount. When photographing with this strobe photographing device, the papilla, macula, blood vessels, and other parts of the subject's eye can be observed in detail, greatly contributing to diagnosis.

On the other hand, for example, when photographing the fundus of the eye using fluorescence, the permeation speed and concentration change of the fluorescent agent are also important information, so information on the reflectance and brightness of the subject may be required. To achieve this, it is sufficient to shoot with a constant amount of light emitted from the objective.
Normally, the amount of light is controlled by the flash time of the strobe tube, the capacity of the main capacitor that stores the flash energy, and the charging voltage.

[0005]

Generally, the charging voltage of the main capacitor of a power source for strobe light emission tends to fluctuate due to factors such as voltage fluctuations of the commercial power source and charging time. However, the above-mentioned conventional method for controlling the amount of light emitted from an object cannot cope with this problem. In addition, for example, when taking fluorescence images with a fundus camera, the light is emitted at a high frequency of one frame per second or more, but in order to reduce the charging time constant, the energy supplied per unit time of the power supply is increased, which complicates the power supply structure. The disadvantage is that it becomes large and the manufacturing cost is high.

SUMMARY OF THE INVENTION An object of the present invention is to provide a strobe photographing device that can maintain a constant amount of light emitted from an object with a simple configuration even when the charging voltage of a strobe light source fluctuates.

[0007]

[Means for Solving the Problems] A strobe photographing device according to the present invention for achieving the above-mentioned object includes a photographing light source for photographing a subject, a light emitting power source for causing the photographing light source to emit light, and a light emitting power source for causing the photographing light source to emit light. The present invention is characterized in that it includes a voltage detection circuit that detects the voltage of a power source for light emission, and a control circuit that changes the light emission time of the photographing light source based on an output signal of the voltage detection circuit.

[0008]

[Operation] The strobe photographing apparatus having the above-described structure detects the charging voltage of the light emitting power source that causes the photographing light source to emit light, and changes the light emission time of the photographing light source according to the detected voltage to maintain a constant amount of light emitted from the object.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained in detail based on the illustrated embodiments.

FIG. 1 shows an embodiment in which the present invention is applied to a fundus camera, in which a condenser lens 2, a photography light source 3 consisting of a strobe tube, a condenser lens 4, and a mirror are placed on the optical path O1 of an observation light source 1 consisting of a halogen lamp. 5, a ring slit plate 6, relay lenses 7 and 8, and a perforated mirror 9 are installed in this order. An objective lens 10 is arranged between the perforated mirror 9 and the subject's eye E, and a focus lens 11, a photographing lens 12, a movable mirror 13, a shutter 14, and a film 15 are sequentially arranged in the optical path O2 behind the perforated mirror 9. When the movable mirror 13 is inserted into the optical path O2, the field lens 16 and the mirror 1 are placed in the reflection direction.
7 is provided, and an eyepiece 18 is provided in the reflection direction of the mirror 17.
is installed.

The photographing light source 3 is connected to a light emitting power source 21 via a light emitting circuit 19 and a light emitting stop circuit 20, and the light emitting power source 21 is connected to an arithmetic circuit 22 and a voltage detection circuit 23, Stop circuit 20, voltage detection circuit 23
is connected to the arithmetic circuit 22. Furthermore, the arithmetic circuit 22
is connected to an input section 24, from which inputs are inputted observation shooting mode selection, shooting conditions such as angle of view, light amount correction, etc., and a shooting start signal.

In such a configuration, during observation, the observation light source 1 emits light, and this observation light is condensed by the condenser lens 2 and transmitted through the photographing light source 3, then condensed again by the condenser lens 4, and then reflected through the mirror 5. ring slit plate 6
The image is formed in the vicinity of . Next, an image of the annular aperture of the ring slit plate 6 is formed near the perforated mirror 9 by the relay lenses 7 and 8, and the observation light is reflected by the perforated mirror 9 and travels to the left toward the eye E. , illuminates the fundus Er of the eye E to be examined through the objective lens 10. The reflected light from the fundus Er travels back along the original optical path, is once imaged by the objective lens 10, passes through the hole of the perforated mirror 9, and is imaged by the focus lens 11 and photographing lens 12. The reflected light is further reflected upward by a movable mirror 13 inserted on the optical path O2, and is then reflected upward by a field lens 16 and a mirror 17.
Since the image is observed by the examiner e through the eyepiece 18, the examiner e performs alignment and focusing before photographing.

Further, during photographing, the light emitting circuit 19 is driven by the arithmetic circuit 22, and a voltage previously charged to the main capacitor inside the light emitting power source 21 is applied, so that the light emitting circuit 19 is placed at a position substantially conjugate with respect to the observation light source 1 and the condenser lens 2. A certain photographic light source 3 is turned on. At this time, the movable mirror 13 rotates and moves out of the optical path O2 as shown by the dotted line, and the reflected light from the fundus Er exposes the film 15 at the same time as the shutter 14 opens.

The arithmetic circuit 22 calculates the appropriate amount of light emission from photographing conditions such as the ISO sensitivity of the film, the angle of view, and light intensity correction, and further calculates the light emission time by adding charging voltage information of the light emission power source 21. The light emission stop circuit 20 is driven by the arithmetic circuit 22 in accordance with the time, and the photographing light source 3 is turned off.

[0015] If the shooting interval is short and shooting is performed continuously at one frame or more per second, the light emitting power source 21 must be capable of supplying the necessary energy within the shooting interval.
The charging voltage of the main capacitor inside the light emitting power source 21 gradually decreases. For example, as shown in Fig. 2(a), when the charging voltage decreases from V1 to V2 (V1>V2), the emission current I flowing through the photographing light source 3 also decreases, and the emission energy is proportional to the square of the charging voltage. Along with this, Figure 2(b)
decreases as shown in . However, if there is a residual charge in the main capacitor inside the light source 21, by extending the light emission time from t1 to t2, it is possible to provide the photographing light source 3 with the light emission energy W0 to obtain an appropriate amount of light emitted from the object. .

Therefore, in this embodiment, the charging voltage of the light emitting power supply 21 is detected by the voltage detection circuit 23, and the light emitting time is calculated by the arithmetic circuit 22 from the charging voltage and the appropriate amount of light emitted from the object, so that the charging voltage does not fluctuate. It becomes possible to obtain a constant amount of light emitted from the objective even when the objective light is emitted.

[0017]

As explained above, the strobe photographing device according to the present invention detects the charging voltage of the light emitting power source that causes the photographing light source to emit light, and changes the light emitting time of the photographing light source according to the detected voltage to adjust the amount of light emitted from the objective. Since the amount of light emitted from the objective is kept constant, even when the charging voltage drops due to short flash intervals of the flash photography light source, or when the voltage of the general commercial power supply fluctuates, the amount of light emitted from the objective can be maintained constant using a small and inexpensive light source. Can be done.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of an embodiment.

FIG. 2 is an explanatory diagram of how light emitting current and light emitting energy change when the charging voltage changes.

[Explanation of symbols] 1 Observation light source 3 Photography light source 15 Film 19 Light emitting circuit 20 Light emission stop circuit 21　Power supply for light emission 22 Arithmetic circuit 23 Voltage detection circuit 24 Input section

Claims (1)

[Claims] [Claim 1] A photographing light source for photographing a subject;
A light emitting power source for causing the photographing light source to emit light, a voltage detection circuit for detecting the voltage of the light emitting power source, and a control circuit that changes the light emission time of the photographing light source based on an output signal of the voltage detection circuit. A strobe photography device featuring: