Radiant energy – Invisible radiant energy responsive electric signalling – Ultraviolet light responsive means
Reexamination Certificate
2000-11-30
2003-05-20
Hannaher, Constantine (Department: 2878)
Radiant energy
Invisible radiant energy responsive electric signalling
Ultraviolet light responsive means
Reexamination Certificate
active
06566656
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to probe style radiometers, and more particularly to a high dynamic range, cost effective and safe probe radiometer for measuring ultraviolet (UV) radiation in a production environment.
2. Background Description
Use of ultraviolet light in the printing and coatings industry has grown rapidly over the past several years. Special ink and coating formulations will polymerize, or “cure,” with exposure to light in the ultraviolet (UV) region of the spectrum. Measurement of the amount and intensity of UV exposure a product receives during the manufacturing process is paramount in establishing and maintaining process control. UV radiometers are used to measure the amount of UV light to which a product is exposed. There is much variation in the configuration of UV curing production lines. As a result, many different types of radiometers are used. The different configurations are driven by both physical considerations and by levels of UV irradiance.
One type of radiometer, which is often used to obtain UV readings in hard-to-reach locations, is the “probe” style of radiometer. The “probe” style radiometer typically consists of a long tube, which houses the light-capturing optics at the tip, and is connected to a body containing circuitry which measures the amount of UV light entering the tip of the instrument.
Most probe style radiomenters have their light sensing probes constructed using a quartz rod enclosed in a round stainless steel tube. This design has several problems. The first problem is cost and performance. The quartz rod must be constructed of high purity fused silica in order to provide high transmission to all wavelengths in the UV region. This drives the cost of the quartz rod upward, as the better the transmission the higher the cost. Moreover, a quartz rod may break if struck with a sharp blow. Other probe designs which use quartz fibers are not as susceptible to sharp blows but instead are very susceptible to changes in light output associated with bending of the fibers. Also, the fibers tend to be quite expensive when made of fused silica.
A second problem is related to the metallic surface of the sheath or cladding which encases the quartz rod or fibers. This metallic cladding presents serious electrical shock and arcing hazards when the probe is inserted into an operating UV environment. UV sources utilize high power inductors and capacitors, and high starting voltages and gas plasmas with up to 10 KW power potential. Contact by the operator with these sources is very hazardous. Further, shorting these power sources through a metal conductor to a machine body or other ground potential presents a hazardous arcing potential.
A third problem relates to the cross-sectional shape of the probe. Beacuse of their use of quartz rods and fibers, most probe designs have a round cross-section. This is undesirable since because rotation of the tip of the probe around its longitudinal axis will cause changes in the measured reading. The round cross-section thus makes it difficult for a user to precisely position the probe for properand consistent measurement.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an improved probe-style radiometer for detecting ultraviolet radiation, and more specifically one which is more economical to make and safer to use and demonstrates improved performance compared with conventional probe-style radiometers.
It is another object of the present invention to provide a probe-style radiometer having a probe rod which is made from an economical material that is resistant to breakage and which at the same time reliably captures and transmits all wavelengths in the ultraviolet region for detection.
It is another object of the present invention to provide a probe-style radiometer which is constructed to prevent a user from experiencing an electrical shock.
It is another object of the present invention to provide a probe-style radiometer which uses a probe rod having a cross-section which can be more precisely positioned by a user during UV detection, thereby enabling the invention to obtain a more accurate and consistent radiation reading compared with conventional probes with a round cross-section.
These and other objects of the invention are achieved by providing a radiometer which has a probe having a generally rectangular cross-section attached to a body which serves both as a handle and a housing for holding the probe electronics. A top surface and a bottom surface of the body preferably have larger width dimensions than the side or edge surfaces, and the overall dimensions of the body are selected to provide a comfortable fit in a user's hand.
The radiometer also includes a liquid crystal display (LCD) formed along one surface of the body, and control switches preferably in the form of two membrane pushbuttons along another one of the body surfaces. The pushbuttons may be located for convenient operation by the user's thumb or index finger. The body can be held either with an “over” or “under” hand type grip, so that the membrane switches are easy to operate with either hand. Information indicative of the UV irradiance detected by the probe is displayed on the LCD, as well as other information including modes of operation, units of measure, and other probe functions. The instrument is preferably battery powered and so that it does not require external wiring to a power source.
In use, the operator grasps the body of the probe in one hand and places the end of the measurement probe in the area in which the UV radiance is to be measured, which, for example, may be a UV curing chamber. Light enters the probe through a small aperture in the tip of the probe. The aperture admits all wavelengths into the interior of the probe through a ground quartz or glass diffuser window which seals the probe interior from outside solids, liquids and gases which may contaminate the interior of the probe and interfere with the UV radiation. The ground quartz or glass window also provides diffusion of the incoming rays so that the angular response of the probe is nearly cosine in nature. Light entering the probe window strikes a mirror inclined (e.g., at a 45° angle) to the quartz window, so that light striking the top surface of the probe is reflected down the length of the probe.
Circuitry within the body measures and displays, in numerical form, the UV irradiance collected at the tip. Irradiance, total energy, and time is measured and displayed on the LCD on the body. At the end of the probe, a UV filter eliminates all wavelengths except those of interest and allows the UV wavelengths to strike a silicon photodiode or other photodector. The photodetector converts the UV radiation into electrical current proportional to the UV radiation striking the detector. The current from the detector is preferably received by a very wide dynamic range (22-bit) analog-to-digital (A/D) converter which converts the current to numerical form.
The invention includes several other features which are not used in conventional probe style radiometers. These include:
Very Wide Dynamic Range and Automatic Operation
The radiometer of the present invention has enhanced sensitivity which enables it to detect UV light in a range from several microwatts to ten watts. This wide dynamic range is accomplished automatically with no requirement by the user to switch gain settings of any kind. This is made possible by the integration of 400, filtered, 20-bit A/D samples/coupled with a software-controlled, 60:1 hardware gain range. Those skilled in the art can appreciate that other arrangements may also be used.
In accordance with microcontroller software, the display will automatically adjust itself with a floating decimal point and proper units to present information in either milliwatts or watts. Preferably, the LCD display display values as low as 0.001 mW/cm
2
. If desired, the control software of the radiometer may automatically change UV detection ranges as the irr
Cain Michael Scott
May Joe T.
Raymont James M.
Rogers Christopher S.
Shorter Christopher S.
Electronic Instrumentation & Technology, Inc.
Lee Shun
Whitham Curtis & Christofferson, PC
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