Three dimensional dimmer

Details Three dimensional dimmer Three dimensional dimmer

2000-03-29

2002-04-09

O'Shea, Sandra (Department: 2875)

Illumination

Light fiber, rod, or pipe

With intensity control

C359S892000

Reexamination Certificate

active

06367958

ABSTRACT:

FIELD OF THE INVENTION
The invention relates to a device for adjusting light intensity provided by a lamp to a fiberoptic light transmission system. Particularly, the invention relates to a dimmer controllably intercepting a beam of light to regulate light flux impinging on the entrance of a fiberoptic conductor. More particular, the invention relates to a three dimensional dimmer controllably adjusting light which is transmitted through it to a fiberoptic conductor from a light source used for illuminating a bodily cavity during an endoscopic surgical operation.
BACKGROUND OF THE INVENTION
Fiberoptic systems used in endoscopic surgery for illuminating an interior of a cavity have become practically indispensable in various surgical procedures. One of the primary reasons for such widespread use of a fiberoptic system is its flexibility allowing a surgeon to illuminate and, thus, to observe inside regions of the bodily cavity that are not easily accessible. Typically, a fiberoptic conductor includes a multiplicity of light conducting fibers, e.g. glass fibers, in the form of a bundle or strand, and extends between an entrance plane and an exit plane which is placed near the site that is to be illuminated.
Fiberoptic systems typically utilize a high intensity lamp as a light source in endoscopic procedures. Too high or too low an intensity of light can detrimentally affect the vision of a surgeon or imaging device. As a consequence, control of the luminous intensity at the exit plane of a fiber conductor has gained a particular significance in the endoscopic surgical procedures. Particularly, the ability to adjust intensity of the light without its distortion becomes critically important.
Numerous attempts have been made to vary the luminous intensity or light-flux from the lamp's output. Typically, these attempts have involved changing the feeding current or voltage or phase of the light source. This control, however, is typically accompanied with changes in the color temperature of the light source and, thus, the color of the illuminated object. The latter is particularly disadvantageous if the image is to be photographed or transmitted or recorded by video techniques, as well as making tissue color determination essential in disease diagnosis, difficult or impossible.
To solve the color change problem, attempts have been redirected to influence illumination of a cavity by introducing a mechanical dimming device or dimmer which is arranged in the optical path between a light source and the entrance plane of a fiberoptic conductor. Utilization of mechanical control devices basically obviates the necessity for interference with the power supply of the light source and eliminates the color temperature change of the emitted light.
Typically, a dimmer is a two-dimensional disk-shaped element which is controllably displaceable along the optical path to alter the light flux impinging upon the entrance plane of a fiber conductor. Displacement, which can be rotational and/or linear, leads to dimming the intensity of light provided to an optical fiber conductor by covering at least a portion of its entrance plane.
The conventional dimmer assembly suffers, however, from the problem that the control of the incident luminous flux causes a change in the course of passage of illuminating light entering the fiber conductor. This, in turn, leads to considerable variation in the light-distribution characteristics of illuminating light emanating from the conductor.
Still another problem characteristic of the conventional mechanical dimmer is that it may be impossible to avoid a change of the course of passage of illuminating light caused by a change in the luminous flux of light which enters a fiberoptic conductor. Therefore, when the luminous flux of illuminating light changes to a considerable extent upon entering a fiber conductor, a distinct change occurs in the light distribution and spectral characteristics of light at its exit plane.
Several attempts have been made to overcome these problems. Typically, a circular disk is placed perpendicular to the light axis and between a lamp and a fiber conductor. The disk may be perforated and have different arrangements of perforations designed to gradually block the light upon the disk's displacement. Basically, this type of the mechanical dimmer is directed at a change in the aperture and has been favorably accepted in the endoscopic medical field.
U.S. Pat. No. 5,006,965 to Jones discloses a disk including an outer peripheral imperforate band and an inner perforate band which is provided with differently sized and variably spaced apart slots. The disk further has a part of its active length open so as when this open portion is in the path of the light beam, 100% of the latter is transmitted to an optical conductor. It is clear that the outer beam stops 50% of the beam, whereas the slots of the inner beam control the rest of the beam.
One of the problems this structure may pose is that a small amount of movement of the disk between its fully open and partly closed regions causes an abrupt and large change of the quantity of illuminating light. This is largely due to the fact that typically the disc may be quite large in proportion to the optical beam diameter.
Another problem associated with many types of planar circular dimmers including the one described above is that using such a disk may cause the outer edges of an output circle of the optical fiber to become smeared and later become dark, a phenomenon known as “ringing”.
Still another problem of such structure is that a distribution of the output light is not monotonically variable throughout a substantial range of light-to-dark. Dimming the light incident on a fiberoptic light guide aperture requires that on the average all rays from all acceptance angles must be dimmed the same amount, as well described by Walter P. Siegmund (Walter P. Seigmund,
Handbook of Optics
(1978)). There are many ways to get a single perfect distribution of the output rays, however this “perfect” distribution is not monotonically variable negatively affecting illumination of a bodily cavity during an endoscopic surgical operation.
U.S. Pat. No. 4,233,650 to Hagner discloses a dimmer comprised of three diaphragms controllably displaceable with respect to one another to asymmetrically and unilaterally reduce the cross section of an entrance plane of a fiber conductor.
One of the obvious problems of this structure may be that a part of the entrance plane is always dimmed because the light beam is invariably blocked by inwardly extending vanes. In practical terms, however, a situation when a surgeon needs unhindered illumination of a cavity is quite frequent. Another problem associated with this structure is that a control mechanism regulating displacement of the three rings may be complicated. Still another problem is that the ringing phenomenon still may not be fully eradicated.
Many attempts have been made to use conventional optical diaphragms, such as an iris diaphragm. A problem common to many of these diaphragms is that they typically change the average entrance angle of the light into a fiberoptic conductor and the exit angle at its exit plane.
Referring to
FIGS. 1
a
-
1
e
, the results of various dimming schemes known in the prior art are shown.
FIG. 1
a
shows the unblocked normal profile of a source of light.
FIG. 1
b
shows a diaphragm
12
crossing the center of the entrance plane of a fiberoptic conductor. It is clear that the light intensity is reduced all over a surgical area, and, particularly, a central region is totally dark
FIG. 1
c
illustrates a segment of the entrance plane being blocked. This structure imposes an upper limit on the light transmission, defined by the blocked sector.
Referring to
FIG. 1
c
, disadvantages of an iris diaphragm mentioned above become clearer. Particularly, a beam width is reduced, thereby darkening peripheral regions of an illuminated surgical area while its central region may be disproportionately illuminated.
Finally,
FIG. 1
d
illustrates a screen

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