Surgery – Endoscope – Having imaging and illumination means
Reexamination Certificate
1999-02-24
2001-12-11
Leubecker, John P. (Department: 3739)
Surgery
Endoscope
Having imaging and illumination means
C600S178000
Reexamination Certificate
active
06328692
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is related to a device for controlling an amount of light transmitted from a light source of a video processor which functions as a lighting unit for an endoscope.
2. Background of the Invention
In an endoscope, light is transmitted from a light source using a light wave guide, such as an optical fiber cable, in order to illuminate an object to be observed. In order to adjust the brightness of the observed image, a device for controlling an amount of light transmitted from a light source to an incident surface of the light wave guide, is employed. In a conventional endoscope, the light amount controlling device has a light shield which is rotated about an axis by a stepping motor. The rotation of the light shield controls the amount of light from the light source that is incident on the incident surface of the optical fiber cable. With this type of light amount controlling device, the brightness of the observed image is detected periodically. Then, the position of the light shield is adjusted such that the brightness of the observed image is within an allowed brightness range.
Conventionally, the amount of light transmitted from the light source to the endoscope is controlled by applying the same number of pulses to the input of the stepping motor during each interrupt procedure (see FIG.
11
A). Therefore, the stepping motor and the light shield are rotated by the same angular amount during each interrupt procedure. The process of detecting the brightness level, and driving the stepping motor to rotate the light shield is repeated until the detected brightness is again within the allowed brightness range.
However, in the conventional endoscope, since the number of driving pulses sent to the motor is constant during the execution of each interrupt procedure, if the number of pulses is set to a relatively small value, then the light shield will be moved slowly. This results in an increase in the response time of the light amount controlling device.
As shown in
FIG. 11A
, for example, each drive pulse rotates the motor 0.5 degrees, three drive pulses are sent during each interrupt. The interrupts are executed every 50 ms. Thus, in order to rotate the stepping motor 10 degrees, seven interruption procedures are required for a total time of 0.35 seconds. Further, since the number of pulses must be in multiples of three, the number of drive pulses cannot be 20, the optimum number, but must be 18 or 21. Therefore, the light shield cannot be moved to the optimum position.
In order to decrease the response time of the light amount controlling device, the number of driving pulses sent to the stepping motor can be increased. However, in this case, the light shield will be moved through a large angle of rotation and thus it may not be possible to adjust the amount of light such that the brightness level falls within the allowed brightness range. This will result in the control system becoming unstable with unwanted back-and-forth oscillations (hereinafter referred to as hunting) occurring.
Further, as different types of endoscopes have different allowed brightness ranges, different numbers of driving pulses are required in order to properly adjust the amount of light transmitted from the light source.
Furthermore, for one type of endoscope, if the sending of a predetermined number of pulses to the stepping motor does not cause hunting, in another endoscope, the predetermined number of pulses may not be sufficiently low, and hunting may occur. Therefore, since the light source may be connected with various types of endoscopes, the number of pulses may be set to the minimum number required for all types of endoscopes in order to avoid the hunting problem. As a result, the speed at which the brightness level can be adjusted for the types of endoscopes is reduced.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a device for controlling the amount of light produced by a lighting unit for use in an endoscope, in which the amount of light can be adjusted quickly and accurately without causing hunting.
According to one aspect of the present invention, there is provided a device for controlling an amount of light of a lighting unit for use in an endoscope, the endoscope being used to view an image of an object. The device includes a mechanism for shielding light generated by a light source and transmitted to the endoscope. A stepping motor drives the light shielding means for a plurality of predetermined time intervals. A mechanism detects a brightness of the image during each of the predetermined time intervals. Pulses are generated during each of the predetermined time intervals. The number of the pulses generated control an amount of driving of the stepping motor in each of the plurality of predetermined time intervals. The number of pulses generated by the pulse generating mechanism is determined in accordance with a difference between the brightness of the image detected during each of the predetermined time intervals and a desired brightness of the image.
Therefore, a different number of pulses is generated when the difference in brightness of the detected image and the desired brightness changes. Preferably, when the brightness difference is large, a large number of pulses is generated, and therefore the light shielding means is moved quickly. Then when the brightness difference is small, and the detected brightness if almost within an allowed brightness range, the number of pulses generated is small. Therefore, the light shielding means is moved in smaller steps and hunting can be prevented.
In a preferred embodiment, a memory stores a first table of numbers of pulses to be generated corresponding to a plurality of brightness ranges. Each of the brightness ranges are a range of differences between the detected brightness of the image and the desired brightness of the image. The memory can be a ROM or other static memory. Further, there is a unique number of pulses stored for each brightness range. Therefore, depending on the difference in brightness between the detected image and an input brightness level set by an operator, the number of pulses sent to the stepping motor will be different.
Since many types of endoscopes may be used with the lighting unit, the memory of the preferred embodiment stores a second table of numbers of pulses to be generated which correspond to the plurality of brightness ranges. The second table of numbers of pulses is different from the first table of numbers of pulses, and corresponds to another type of endoscope.
Further, the device includes a selector for selecting one of the first and second tables.
In another preferred embodiment, the endoscope has a memory for storing the type of the endoscope. The selector selects either the first or second table in response to the type of the endoscope stored in the memory.
This allows for easy selectability of the endoscope and facilitates operation of the device when used with the respective endoscope. Furthermore, the device is optimized for each endoscope that is attached thereto.
In another preferred embodiment, the selector is manually actuable for selecting the type of endoscope.
According to a second aspect of the present invention, there is provided a device for controlling a device for controlling an amount of light of a lighting unit for an endoscope, the endoscope being used to view an image of an object. The device includes a mechanism for shielding light generated by a light source and transmitted to the endoscope. A stepping motor drives the light shielding mechanism by a predetermined driving amount for a plurality of time intervals. A mechanism sets a duration of the time interval to have one of a plurality of time values.
Therefore, by changing the time interval for driving the light shielding means, the time required for adjusting the amount of light can be reduced, even if the amount of driving of the stepping motor is made small to prevent hunting.
In a preferred embodiment, the end
Honda Ryoji
Takada Makoto
Takahashi Tadashi
Asahi Kogaku Kogyo Kabushiki Kaisha
Greenblum & Bernstein P.L.C.
Leubecker John P.
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