Illumination – Light fiber – rod – or pipe – Medical
Reexamination Certificate
1999-11-15
2002-06-11
Cariaso, Alan (Department: 2875)
Illumination
Light fiber, rod, or pipe
Medical
C362S011000, C362S228000, C362S552000
Reexamination Certificate
active
06402358
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the field of photographic illuminators, and more particularly to the field of microphotographic illumination systems including a pilot light and strobe light.
BACKGROUND OF THE INVENTION
It is well known to employ illumination systems for microphotography. Typically, these take two forms: ring lights and fiber optic illuminators. In addition, illumination systems are well known for microscopy, and long exposures for photographic purposes have often been employed to make use of a single illumination mode light source. A combined pilot lamp and strobe single head fiber optic illuminator for photomicroscopy is described in Allen, U.S. Pat. No. 4,006,487, expressly incorporated herein by reference. A ring light is a device that encircles a camera lens to provide radially uniform illumination, generally producing a shadowless image. A ringlight setup is unsuitable for many types of work, and is generally unavailable for microscopy, for example due to spatial constraints. Further, ring lights do not provide for rear illumination of transparent or translucent samples.
Fiber optic illuminators serve three essential functions. First, they may filter infrared and ultraviolet rays and thus avoid heat load and UV degradation of the subject. Second, they allow versatile positioning of multiple, e.g., three, illumination heads, which may be positioned arbitrarily with respect to the subject, including behind it. Third, fiber optic illuminators are known which integrate both pilot lamp and flash lamp, allowing the same optical fibers to carry flash illumination for photographic exposure and pilot light illumination for modeling and light source positioning. A pilot light is thus a lower intensity illuminator designed for composing the image visually, using a different, lower intensity continuous output light source than the strobe flash. Thus, it is known to align the pilot lamp and flash lamp within an aperture of al fiber optic collector, so that both sets of rays impinge upon the same optical fibers, thus assuring illumination along the same axis. However, such known systems generally suffer from a deficiency in that the ratio of pilot lamp to flash illumination may vary between fiber optic pickups, and that the flash illumination itself may vary in color balance between pickups at various locations.
Existing fiber optic illuminators thus suffer from poor homogeneity of the light output, and variations in relative light intensity between the pilot illuminator and the flash, as well as between different color of illumination by heads within the system. Thus, significant experimentation is necessary for high quality images to compensate for the inconsistencies.
Traditional designs of studio or professional-type illuminators do not necessarily seek high optical efficiency. Thus, in order to provide a robust, flexible, reliable and consistent system, light output may be wasted. Thus, the cost of power, equipment, and replacement parts (e.g., bulbs) are considered secondary to functionality. In production environments, i.e., those where the task is cataloging, data acquisition, documentation, or otherwise taking a large number of images, pilot lighting is important to avoid loss of productivity due to multiple exposures in order to properly compose the image prior to final image acquisition. Further, for transient, unstable or moving subjects, flash illumination is essential to freeze the image. Thus, a dual illumination mode illuminator is essential in such environments.
In production environments, the illumination system typically provides substantial excess illumination capacity, anticipating waste. In fact, this waste is generally acceptable in many environments, but limits the use of the systems to studios and other controlled environments with sufficient resources. For example, with a 250 Watt halogen pilot lamp, the fiber optic illuminator system requires substantial air flow and cooling, and an insulated case or other barrier to prevent human burn hazard and overheating. The fan provided for cooling produces a steady noise, and with the required air flow passages it is difficult to muffle the noise made by strobe triggering. Portable battery operation is typically restricted because of the high power draw.
A known design for a fiber optic illumination system provides an attachment to a standard studio strobe with modeling lamp, described in Baliozian, U.S. Pat. No. 4,428,029, expressly incorporated herein by reference, wherein a set of fiber optic pickups are arrayed in front of the strobe with each pickup aligned facing toward both the strobe and modeling lamp. A mechanical barrier or shutter allows modulation of light to the set of pickups, while traditional optical components may be placed at each fiber optic head. Prior fiber optic illuminators with both pilot and strobe modes, including the aforementioned type, suffered low optical efficiency due to poor utilization of the light output both illumination sources. In other words, the fiber optic bundles were not arranged to capture a large percentage of the available light output, but rather to provide modular arrangement and simple design. Further, each fiber optic bundle was independent, and therefore critically dependent on the positioning and local variations in lamp output. Therefore, while the fiber optic bundles indeed carried both pilot and flash illumination, the efficiency was low, and the illumination intensity and color balance were non-uniform and unregulated.
Strobe light output is generally governed by the time-intensity product of the flash. The intensity, in turn, is governed by the voltage and current (power) delivered to the flash lamp. Typically, the energy for the flash lamp is stored in a capacitor prior to triggering. The static voltage across the capacitor is insufficient to ionize the xenon gas within the tube, so a substantially higher potential trigger pulse is provided to commence the flash cycle. The flash cycle can be terminated in two ways. First, the energy stored in the capacitor can be fully discharged, down to a voltage insufficient to maintain ionization of the gas in the flash tube, and thus until the flash lamp no longer sustains conduction, or a high voltage semiconductor or switch can terminate the current flow in advance of full discharge.
The color temperature of the flash lamp depends on a number of factors, but for a given lamp, the current flow generally correlates with the color temperature over the course of a flash cycle. Thus, using a switch to prematurely terminate the flash cycle at an arbitrary time before complete discharge to control intensity will also have the undesired effect of changing the average color temperature of the lamp output over the flash cycle, since as the capacitor discharges, the voltage will drop and therefore the current through the lamp will drop over time. Using a single capacitor, complete discharge does not provide an efficient control over intensity, and therefore, a controllable shutter, iris or neutral density filter would be necessary to modulate output without changing color balance. This problem is compounded by known strobe drive systems that employ a rheostat (variable resistor) to control flash output; with each different setting of the rheostat, a different color temperature output would be expected due to the change in current through the lamp.
Therefore, advanced designs were developed to provide a plurality of capacitors within the strobe power pack, which are selected based on the desired output intensity. Thus, instead of seeking to drive the flash lamp over one or more orders of magnitude using pulse width intensity modulation, by cutoff timing alone, an appropriate capacitance and charge voltage is selected to normalize the starting and ending voltage on the flash lamp over the course of the cycle, and therefore impliedly normalizing the current and color temperature. So-called studio strobe power pack systems may therefore provide one or more capacitors (e.g., two), each of which m
Cariaso Alan
Milde & Hoffberg LLP
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