A meter for measuring UV light having wavelengths, preferably between 205 nm and 237 nm. The meter includes at least one UV sensitive photo diode adapted for detecting the wavelengths of UV light between a lower end and an upper end; a first filter that blocks the UV light having wavelengths below 237 nm down to at least the lower end that the UV sensitive photo diode can detect; a second filter that blocks the UV light having wavelengths above 230 nm up to at least 205 nm; at least one amplifier for amplifying a signal from the UV sensitive photo diode; an analog to digital converter; a microprocessor; a battery in electrical communication with the microprocessor. The microprocessor preferably being in communication with the amplifier and the analog to digital converter. The microprocessor provides a result for the UV light that the UV sensitive photo diode is exposed to.

FIELD OF THE INVENTION

The inventive system is in the field of Ultraviolet Light sterilization, specifically metering in the C band of ultraviolet wavelengths (UV-C). Such sterilization is presently used in hospital surgery rooms, burn wards, and similar areas that require a high degree of sterilization. The primary difference with these existing uses is the inventive system will be used to measure safety because of the presence of people and living tissues.

BACKGROUND OF THE INVENTION

The Corona Virus pandemic has changed many aspects of human life in every country. Even after the virus has been tamed by vaccines and antibodies the changes will remain. People are no longer comfortable being in close quarters with others in public settings. The contagion of regular flu and colds are now being treated with many of the same techniques as were used during the pandemic.

UV has 3 different bands, A, B, and C. UV-A is what we would generally associate with “black lights” and black light fluorescence. It is the longest wavelength of the 3 and has the least ability to kill viruses, bacteria and similar pathogens. Its wavelengths are from 315 nm to 400 nm.

UV-B has been the most preferred wavelength to be used by tanning salons. It is dangerous to use in excess around living things because it is both powerful enough to burn and has a long enough wavelength to penetrate cells, causing irreparable genetic damage. Its wavelengths are from 280 nm to 315 nm.

UV-C is recognized as one of the most effective wavelengths at killing the small pathogens because the shorter the wavelength the more powerful it is. Only recently was it discovered that some of the wavelengths in this band are long enough to kill pathogens and short enough to not be able to penetrate living cells. Living cells are many times larger than the tiny pathogens (including viruses) that we want to kill (or render inactive). UV-C is from 100 nm to 280 m, and the wavelengths that are generally being considered safe for exposure to human tissue are from 200 nm to 230 nm. UV-C does generate undesirable ozone, especially at wave lengths shorter than 200 nm.

Several studies have shown that hairless mice can be subjected to over 20 times the amount of 200 nm to 230 nm UV-C as is suggested for humans, 8 hours a day, with no adverse effect. These studies have been performed in Japan at University and in the US at Columbia University. These studies are extending in time for up to 6 months, still with no adverse effects.

There are several technologies that can generate UV light in the germicidal wavelengths, gas-discharge lamps have been around a long time and depending on the gases used can kill pathogens. Low pressure mercury generates 254 nm and has been the standard for decades, it is basically a fluorescent light without the phosphors on the inside that convert the UV to visible light. LEDs have recently been commercialized in the UV-A and UV-B spectrums, but they are very inefficient. There are a few in the longer wavelengths of the UV-C spectrum. A research project in Japan recently made an LED that was in low 200 nm's, the safer portion of the UV-C spectrum, but it was very inefficient and not practical for commercialization at this time.

Work places are protected by regulations, one of which is the internationally recognized Threshold Limit Values (TLV) which determines how much of particular UV wavelengths that workers can be exposed to in an 8 hour work day. This important protection is currently in a state of revision with the limits expected to being raised in the near future. Regardless of the timing of these changes the TLV limit it is important for workers safety and accurately measuring this level is equally important.

There are very few meters or technologies capable of measuring in the 222 nm range because it has only recently become a widely used wavelength. Most meters work at 254 nm as it has been the standard wavelength for decades. Some 222 nm fixtures have filters and are safe and some don't have filters and are unsafe because they transmit wavelengths other than just 222 nm. The filter material would ideally be very pure hafnium oxide deposited 2-3 um building a cutoff filter 234-400 nm with a depth of 0.0001. The few meters that do measure 222 nm are in the hundreds or thousands of dollars and are simply out of the budget for most users, besides not telling if there are harmful wavelengths present. This problem will continue once LEDs can make strong light at 200-234 nm.

There are portable electronic spectrometers available for the UV spectrum, but their prices start at $6,000 and up. No meter, dosimeter, or spectrometer presently show current TLV levels or TLV percentages present along with unsafe wavelengths present.

There are a plethora of companies that make UV dosimeter strips of paper. These strips are protected in opaque sleeves and once removed are exposed to a UV source, much like photographic films. They use colorimetric inks that change color when exposed to UV with a time/intensity factor, a dosimeter. The biggest problems are that the various wavelengths that are detected overlap too much, so it is impossible for these dosimeter strips to determine good exposure of safe wavelengths while in the simultaneous presence of bad wavelengths. These dosimeter strips also take a considerable amount of time to work, especially in the presence of dim but dangerous wavelengths.

What is needed is an affordable 200-234 nm (Safe UV-C) dosimeter that also indicates the percentage of TLV and the presence of unsafe wavelengths.

SUMMARY OF THE INVENTION

The inventive device provides a Safe UV-C (200 nm-234 nm) dosimeter that indicates the level of both safe and unsafe UV light. Ideally this dosimeter will be inexpensive and easy to use by laymen. Filters are the main reason that 222 nm based fixtures can be safe. 222 nm is generated by bulbs with the gasses krypton (Kr) and chloride (Cl) but there are several spikes of wavelengths other than 222 nm generated and these are what need to be filtered as they are unsafe. The inventive device will use one of these filters to block all unsafe wavelengths that strike the colorimetric paper or photo diode sensor to measure the safe levels. Because the photo diodes are small, the associated filters could also be very small, further lowering costs of the inventive device. The inventive device will also use a filter that blocks the safe and visible light from the second photodiode sensor or second area of colorimetric paper to measure only unsafe light levels. There are different types of paper strips, permanent and temporary. The permanent type is like what is currently being used in hotel rooms, the hotel sanitizes the room with UV and leaves the strip for the customer to see later. The temporary strips are similar to eyeglasses that change darkness when exposed to light, they darken quickly in bright light and then take about a minute to change back to clear once they are in darkness.

The combination of these same two filters in a quartz print frame and using existing UV dosimeter strips would be able to show dosing and the presence of unsafe wavelengths without using electronics. The unused colorimetric paper could be stored in a light tight drawer under the picture frame. The “safe” filter would cover one portion of the colorimetric material and the second “unsafe” filter would cover an adjacent portion of the colorimetric material. This would be a slow process in use but very inexpensive for single or occasional use, as the filters are subtractive and would add to the exposure time required by the colorimetric material. The electronically metered version would be for fast, constant use.

The inventive electronic device that uses photo diodes would read to light levels and ideally be connected by Bluetooth or other wireless means to a cell phone, tablet, or other such device (preferably portable but not necessarily) for display and logging functions. Without a display the sensor device could shrink to a very small size that would easily fit on a key chain FOB for constant access.

The present disclosure, therefore, includes a meter for measuring UV light having wavelengths, preferably between 205 nm and 237 nm. The meter includes at least one UV sensitive photo diode adapted for detecting the wavelengths of UV light between a lower end and an upper end; a first filter that blocks the UV light having wavelengths below 237 nm down to at least the lower end that the UV sensitive photo diode can detect; a second filter that blocks the UV light having wavelengths above 230 nm up to at least 205 nm; at least one amplifier for amplifying a signal from the UV sensitive photo diode; an analog to digital converter; a microprocessor; a battery in electrical communication with the microprocessor. The microprocessor preferably being in communication with the amplifier and the analog to digital converter. In an alternate embodiment, the meter may include two UV sensitive photo diodes

The microprocessor provides a result for the UV light that the UV sensitive photo diode is exposed to. The result may be a numerical result. The result may be intensity provided in watts per cm2or it may be expressed in smaller units of watts. The meter may be adapted for providing results of the unsafe light outside of 205-234 nm. The result may be provided as a percentage of TLV levels. The meter may include an output device in communication with the microprocessor such that the result is provided to the output device. The output device may include a display and wherein the result is displayed on the display. The display could be a smartphone in communication (Bluetooth) with the microprocessor.

The foregoing has outlined in broad terms the more important features of the invention disclosed herein so that the detailed description that follows may be more clearly understood, and so that the contribution of the instant inventors to the art may be better appreciated. The instant invention is not limited in its application to the details of the construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. Rather the invention is capable of other embodiments and of being practiced and carried out in various other ways not specifically enumerated herein. Additionally, the disclosure that follows is intended to apply to all alternatives, modifications and equivalents as may be included within the spirit and the scope of the invention as defined by the appended claims. Further, it should be understood that the phraseology and terminology employed herein are for the purpose of description and should not be regarded as limiting, unless the specification specifically so limits the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Before explaining the present invention in detail, it is important to understand that the invention is not limited in its application to the details of the construction illustrated and the steps described herein. The invention is capable of other embodiments and of being practiced or carried out in a variety of ways. It is to be understood that the phraseology and terminology employed herein is for the purpose of description and not of limitation.

Referring now to the drawings, wherein like reference numerals indicate the same parts throughout the several views, a representative depiction of an (existing art) UV light meter100shown inFIG. 1. where meter100has several parts. The power switch102, the measurement button104, the display106, sensor window108. Not shown are the battery door or any internal parts. One turns on the power switch102to the UV meter100and then they can aim the sensor window108towards the ambient light source and then press the measurement button104whereupon the display106shows the light level, usually in milliwatts per square centimeter, or fractions thereof.

A different (existing art) technology is shown inFIGS. 204, 208 and 210where a colorimetric paper strip200is out of its protected bag202. The colorimetric portions are in the smaller internal confines and are usually adjacent to printed color keys206. These keys206allow one to match the colorimetric portions204,208and210to a key206color which indicates how much exposure occurred. The strip200comes sealed in the bag202and the strip200is only removed for exposure to the ambient light at the last moment. A set period of time or exposure elapses and the colorimetric portions204,208and210either fully changes color indicating a full dose, or it changes slightly indicating less than a full dose.

InFIG. 3we see a chart300of unfiltered 222 nm that has been generated by a krypton and chloride bulb. Notice that the peak is at 222 nm302and the upper toe304on the shorter wavelength side is in the safe zone at about 210 nm and the lower toe306on the other side of the 222 nm peak is about 229 nm in the safe zone but there are other small peaks at 238 nm308and 290 nm310and they are dangerous to humans and living tissues.

InFIG. 4we see a chart400of filtered 222 nm that has been generated by a krypton and chloride bulb. Notice that the peak is at 222 nm402and the toe404on the shorter wavelength side is in the safe zone at about 210 nm and the toe406on the other side of the 222 nm peak is about 229 nm in the safe zone but there are no other small peaks that could be dangerous to humans or other living tissues.

InFIG. 5the inventive electronic Safe UV-C dosimeter500is shown. The dosimeter500ideally has only one button/switch502that is used to turn on the meter500, make measured readings, and by holding it down for 5 or 10 seconds would cause the unit to try and pair it's Bluetooth to a nearby smartphone512. The inventive meter500has a dual sensor window504made of quartz glass. The only other necessary external feature is a charging port506which would ideally be a USB-C type, the battery510is rechargeable permanently mounted inside the plastic case508of meter500and is unseen in this illustration. Also shown is a key ring mounting point514.

InFIG. 6components of the inventive dosimeter are shown as a side view but connected assembly600. On top is the quartz sensor window504, with safe filter602shown just below as well as unsafe filter604next to it. The safe filter602blocks wavelengths longer than lower toe306, somewhere between 228 and 237 nm. The safe filter602should filter down to just above visible light or where the photo diode can no longer sense. The unsafe filter604blocks wavelengths shorter than the lower toe306, somewhere between 228 and 237 nm. The unsafe filter should block all light from there up to beyond the upper toe304, somewhere just shorter than 205 nm.

Below safe filter602is safe photo diode606and next to it is unsafe photo diode608. Both Safe photo diode606and unsafe photo diode608are mounted on a printed circuit board (PCB)610, along with the microprocessor612which has a two-channel internal 12 bit analog to digital converter (ADC)622. An ideal UV photo diode to use would be the SD008-2151-112 from Advanced Photonix of Camarillo Calif. The button/switch502which is a momentary switch is also mounted on the PCB610but comes to the side in order that the light path616not be blocked by the user's fingers. The charging port506is also mounted on the PCB610as is the battery charging circuit614. On the upper side of the PCB610is the Bluetooth module618. Below the PCB610, connected by wires620is the battery510.

The lack of a display allows for a lower cost and a smaller size for the inventive 222 nm dosimeter500. The safe photo diode606is mounted against the safe filter602such that no other light is allowed into the safe diode606other than what comes through the filter602first. The safe photo diode606also has a clear view through the quartz cover window504. The unsafe photo diode608is positioned so that is against the unsafe filter604and receives no light that hasn't first passed through the unsafe filter604. The unsafe photo diode608has a clear view through the quartz cover window504.

InFIG. 7shows a schematic of the inventive electronic Safe UV-C dosimeter500. The battery510feeds a low quiescent current voltage regulator702that then goes to the microprocessor612. The microprocessor612controls a switch704that powers both the Bluetooth wireless module618and the op-amps710,712and photo diodes606,608. The push button614goes to an interrupt pin706on the microprocessor612such that the microprocessor612wakes up when the button/switch502is pushed. The microprocessor612then powers the wireless618and sensors606,608and op-amps710,712and determines if it is going to read and report UV light levels or is it going to pair its Bluetooth wireless module618with a smart phone512. The resistors716of the op-amps710,712are sized to allow the correct amount of gain in the op-amps710,712so that the signal to the ADC622is ideal for a full 12 bits of resolution over the desired brightness range of light detected. The microprocessor612could be separate, or the same microprocessor612used in the Bluetooth wireless module618.

When the battery port506is being charged614it is being monitored by a pin on the microprocessor612, and during charging the dosimeter500is using the Bluetooth wireless module618to search and talk to a calibration computer714. If the calibration computer714is found the computer714produces a known brightness of light and then tells the dosimeter500. The dosimeter500reads the brightness and stores it in EEPROM. The calibration computer714makes the next brighter step of light and the process is repeated until all the light levels have been read and recorded in EEPROM for both safe and unsafe light. The light levels are communicated and stored in the format of microwatts per cm2.

When the button/switch502is pushed the processor612wakes up the dosimeter500connects to its paired smartphone512and then reads the safe606and unsafe photodiodes608and transmits the Bluetooth wireless module618to the smart phone512in microwatts per cm2. The smart phone512then displays the light level of safe light to microwatts per cm2, and then also calculates the percentage of TLV and displays that as a percentage. Lastly the smart phone512takes the unsafe light level and determines which display should be used, “safe”, “unsafe”, or “very unsafe”. “Safe” would be displayed in green. Both “unsafe” and “very unsafe” would be displayed in red. After completing the communication with the smartphone512, the dosimeter500would go into low power sleep, un-powering the photo diodes606,608, op-amps710,712, and Bluetooth wireless modules portions618.

InFIG. 8shows an open inventive print frame dosimeter800that has a safe filter602and an unsafe filter604on the bottom side of a top sheet of quartz glass812that is hinged814to base plate816. The best size for the inventive dosimeter is about the size of a credit card so that it can be carried in one's pocket. Ideally the filters602,604are permanently attached to quartz glass812. Also shown is a sheet of existing colorimetric coated paper802and alignment ridges804to precisely position the colorimetric coated paper802in the print frame dosimeter800. The colorimetric coated paper802has printed areas806, colorimetric coated areas808, and blank areas810. The colorimetric coatings can detect UV down to the UV-A band and up to 200 nm. UV-A could be detected separately by a different colorimetric material818in a different area of the paper that is sensitive only to UV-A and this colorimetric material is available from Rochie Tech.

FIG. 9shows base plate816of the inventive print frame dosimeter800with the drawer902in an opened position with respect to base plate816. Sandwiched between the colorimetric coated paper802and quartz glass812are a safe filter602and an unsafe filter604, side by side. Ideally the location of the filters602,604is aligned with the printed area806on the colorimetric coated paper802. This happens once the colorimetric coated paper802fits over alignment ridges804. Then the colorimetric coated paper802, its printed area806, the colorimetric coating areas808, and the filters602,604are all in place to take an exposure through the two filters602,604onto the colorimetric coated paper802making a dosimeter800that measures and shows safe light and shows the presence of unsafe light.

InFIG. 10we see the colorimetric coated paper802as it would be used in the inventive filtering device800(ofFIGS. 8 and 9). There are 3 distinct areas, the safe dosimeter indicator1002is printed in a graduated stripe and its corresponding reference key1004which is printed at the same darkness and color as would indicate a particular exposure along the stripe. This is a gradual scale from light (low exposure) to a dark indication (heavy exposure). This portion of the dosimeter1002would be sensitive to UV-C and would show maximum allowable exposure at the TLV point1006. The second distinct area is the unsafe dosimeter indicator1008which is printed in a graduated stripe and its corresponding reference key1010. The key1010shows a light indication equals a low exposure to dangerous light, a medium darkness would indicate an unsafe exposure, and a dark indication along the stripe would show a very unsafe exposure to dangerous light. This portion of the dosimeter1008would be sensitive to UV light in general. Lastly the third distinct area would be an optional dosimeter1012that detects UV-A exposure. The dosimeter area1012which is printed as a stripe and is directly adjacent to the reference key1014where the key shows a light color for a mild exposure and is dark in the portion with a heavy exposure to UV-A light along the stripe. This dosimeter area1012would not be covered by any UV filters and would be a different type of colorimetric material than the previous in that it only detects UV-A.

The term “at least” followed by a number is used herein to denote the start of a range beginning with that number (which may be a ranger having an upper limit or no upper limit, depending on the variable being defined). For example, “at least 1” means 1 or more than 1. The term “at most” followed by a number is used herein to denote the end of a range ending with that number (which may be a range having 1 or 0 as its lower limit, or a range having no lower limit, depending upon the variable being defined). For example, “at most 4” means 4 or less than 4, and “at most 40%” means 40% or less than 40%. Terms of approximation (e.g., “about”, “substantially”, “approximately”, etc.) should be interpreted according to their ordinary and customary meanings as used in the associated art unless indicated otherwise. Absent a specific definition and absent ordinary and customary usage in the associated art, such terms should be interpreted to be ±10% of the base value.