1. Field of the Invention
The present invention relates to a light source device for an endoscope, which supplies illumination light to a light guide provided in the endoscope.
2. Description of the Related Art
Usually, a light source device for an endoscope is disposed in an optical path of illumination light which is radiated from a light source (or a lamp) and enters the light guide of the endoscope. The light source device has aperture members for blocking part of the illumination light. Namely, the aperture members are moved to adjust the amount of illumination light entering the light guide.
The aperture members are rotatably connected to each other at a rotation axis, like scissors, in such a manner that the optical path of the illumination light is formed between the aperture members. A guide slot is formed in each of the aperture members, which are positioned in such a manner that the guide slots overlap each other. An engaging pin, which is fixed to a stationary plate, is inserted into the overlapped portion of the guide slots. Thus, when the rotation axis is moved by an arm rotated via a stepper motor, for example, the aperture members are opened or closed, so that the amount of the illumination light is adjusted.
A clearance is formed between the engaging pin and each of the guide slots, so that the engaging pin can slide smoothly along each of the guide slots. Accordingly, when the rotation direction of each of the aperture members is reversed, the aperture members do not start to rotate until the engaging pin is engaged with an inner wall of the guide slot, which is opposite to another wall of the guide slot.
Thus, when the movement of the aperture members are changed between the opening and closing directions, the amount of the illumination light is hardly changed regardless of the rotation of the stepper motor, and thus the illumination light cannot be controlled with accuracy.
Therefore, an object of the present invention is to provide a light source device for an endoscope, which can control the illumination light with high accuracy, even when the aperture members are moved from the opening to the closing direction and vice versa.
According to the present invention, there is provided a light source device for an endoscope, with a light guide through which illumination light passes, the light source device comprising a light source, an aperture mechanism, a moving mechanism and an urging member.
The light source radiates the illumination light, which is led to an end portion of the light guide. The aperture mechanism is disposed between the light source and the end portion. The aperture mechanism is movable and has a guide portion with which an engaging pin is engaged. The moving mechanism moves at least one of the aperture mechanism and the engaging pin, so that the aperture mechanism is open or closed to adjust the amount of the illumination light led to the end portion. The urging member always urges the aperture mechanism in a direction in which the aperture mechanism is opened or closed.
Preferably, the aperture mechanism comprises a pair of aperture members to sandwich an optical path through which the illumination light passes. The urging member may urge the pair of aperture members in a direction in which the pair of aperture members is closed, so that play or backlash is eliminated between the engaging pin and the guide portion. In the other example, the urging member may urge the pair of aperture members in an open direction.
Preferably, the urging member comprises a coiled tension spring pulling the pair of aperture members toward each other. The urging member may comprise a coiled compression spring pushing the pair of aperture members away from each other. Due to the coil spring, the structure of the light source device is simple.
The pair of aperture members may be rotatably connected to each other about a common axis and the engaging pin is fixed to a stationary member. In this construction, the moving mechanism moves the common axis, so that the pair of aperture members is rotated about the common axis to the open and close positions. The guide portions of the pair of aperture members are guide slots overlapping each other and the engaging pin is inserted in the overlapped portion of the guide slots.
Further, according to the present invention, there is provided a light source device for an endoscope, in which aperture members are provided in an optical path through which illumination light, radiated from a light source, passes and enters a light guide of the endoscope, the aperture members having guide slots with which an engaging pin is engaged, at least one of the aperture members and the engaging pin being moved so that the aperture members are open or closed to adjust the amount of the illumination light, characterized in that an urging member is provided to always urge the aperture members in a direction in which the aperture members are opened or closed.