Classifications

• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
  • H10F77/00—Constructional details of devices covered by this subclass
  • H10F77/50—Encapsulations or containers
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J40/00—Photoelectric discharge tubes not involving the ionisation of a gas

Definitions

• the present invention relates generally to photo- detectors for sensing and measuring radiant energy, and 5 particularly visible, invisible and near light wavelength energy, and more particularly to a photodetector including an electrically conductive window which is transparent to the desired light and near light wavelengths while pre ⁇ cluding interference in such desired measurements by other
• electromagnetic radiation such as radio frequency inter ⁇ ference, power line emissions and other spurious sources.
• Photodetectors are generally available in the form of devices that sense illumination falling thereon. Meas-
• 15 urements may be qualitative, i.e., the presence or absence of illumination, o.r quantitative, i.e., a measurement of • the intensity of illumination thereon.
• photo- detectors take the form of a sensitive area which varies as to electrical properties as a function of light or re-
• photovaristors commonly cadmium sul ⁇ phide and lead telluride devices
• phototransistors typi ⁇ cally junction transistors with the base exposed to a light source in order to modulate the collector current as a func-
• photodiodes solid state diode devices in which PN junctions are sensi ⁇ tive ' to light incident thereon to alter current
• photo- resistor materials photoconductive materials, photovoltaic cells, etc.
• photo- resistor materials photoconductive materials, photovoltaic cells, etc.
• phototransistors and photodiodes are considered the more sensitive of the photodetec ⁇ tor devices.
• Photodetectors are often employed in very demanding and sensitive measurement processes. Typical of the de and-
• the photodetector is placed adjacent a thin section of living tissue in order to measure the light passing through the- tissue and, as a function of the light measured, determine the oxygenation of blood within such tissue.
• the determination may be, in some instances a life and death measurement.
• the subjects of such determination may be patients exposed to a number of sources of interfering radiation.
• Surgical patients for example, are often monitored by a number of devices, i.e., electrocardiograms, electroencephalograms, and other body function measuring electronic devices, as well as being subject to radio frequency currents utilized in electro- surgery.
• the patient's body is a significant source of static electricity and various electromagnetic radiation including radio frequency interference and 60 Hz AC emissions.
• Such radiation is fully capable of regis ⁇ tering spurious signals in photodetectors, and particularly solid state photodetectors.
• the photosensitive material in the case of solid state photodetectors, may produce a current.
• conductance of the photodetector may be induced by a "field effect" caused by such interference.
• the present invention which provides a heretofore unavailable improvement over previous photodetectors for selected light and near light wavelength energy detection and/or measurement, comprises a photosensitive material car ⁇ ried within a conductive case having defined therein a win ⁇ dow transparent to the desired light and near light wave- lengths and also conductive to isolate the photosensitive material from various interferences such as static electri ⁇ city, radio frequency, AC power line couplings, and other such electromagnetic radiation.
• the window is formed of glass or similar vitrious materials, or crystal ⁇ line substances such as quartz, and includes an electri ⁇ cally conductive thin coating of metal or metal oxide thereon with the metal oxide being sufficiently thin to be transparent to the desired wavelengths.
• the window may be of a conductive vitrious, or other homogenous, material.
• an object of the present: invention is to provide a new and improved photodetector for selective wavelengths of energy which is insensitive to non-selected wavelengths of electromagnetic energy to preclude or reduce spurious signals induced by the non-selected wavelengths of energy.
• Another object of the present invention is to provide a new and improved photodetector which may be conveniently and economically produced utilizing conventional photode ⁇ tector structures.
• FIGURE 1 is a partially cut away and sectioned view of a photodiode photodetector in accord with a preferred embodiment of the invention.
• FIGURE 2 is a side view of a preferred embodiment of the window employed in the photodetector of FIGURE 1. Best Mode for Carrying Out the Invention.
• Photodetector 10 is specifically configured as a photodiode, since a photodiode is one of the more sensitive of photodetectors, and thus presents a more difficult case. However, it is to.
• Photodetector 10 includes an electrically conductive case 12, which is typically formed of metal, carrying on a wall thereof photosensitive material 14.
• photosensitive material 14 comprises a PN junction which, when a potential is provided across such junction, is sen- sitive to photons and other radiant energy to provide a hole-electron pair, thereby inducing conductance .in photo ⁇ sensitive material 14 as a function of the radiation strik ⁇ ing such material.
• electrode 16 through contact with case 12 is in electrical contact with one portion of photosensitive material 14, while electrode 17 is connected to photosensitive material 14 such that an electrical circuit between electrodes 16 and 17 can be com ⁇ pleted only through photosensitive material 14.
• a transparent window 22 is hermetically sealed therein to permit transmission of photons in the form of visible, invisible and near light wavelength energy.
• conductive layer 24 is provided on at least one surface of window 22, typically at least the outer surface in most instances to act as anti-reflective as well as conductive layer, with conductive layer 24 also electrically in contact with case 12.
• Conductive layer 24, as illustrated in FIGURE 2 may be formed in a number of well known manners.
• a thin layer of metal, preferably a non-oxidizable, noble metal such as gold, may be sputter coated in a very thin layer onto window 22 to provide an electrically conductive layer which is transparent to desired wavelengths of light. While thin, sputter coatings of reduced metal are operable, the process and materials tend to be expensive. The more commonly available metals when sputter coated are subject to oxida ⁇ tion which may compromise the conductivity and transparency required of thin layer 24.
• layer 24 may be more conveniently and economically produced by applying solutions or vapors of metal compounds to window 22, and then pyrolytically decomposing such compounds to form metal oxide coatings which are transparent and electrically con ⁇ ductive.
• Such processes are well known for, as an example, producing transparent, conductive resistance heating coat ⁇ ings on aircraft windshields etc. Vapors of stannic chlo- ride are conveniently pyrolyzed to form a transparent, con ⁇ ductive and stable layer of tin oxide, which is quite suitable as conductive layer 24.
• Various other methods for producing transparent, electrically conductive layers may also be employed.
• the photodetector of the instant inven ⁇ tion provides heretofore unavailable discrimination between light and near light wavelength energy, and interference resulting from static electricity and various radio fre ⁇ quencies and other electromagnetic energy forms. While the preferred embodiment involves a transparent window car ⁇ rying thereon a thin, transparent, electrically conductive layer, it is also contemplated and possible to produce a transparent glass substance .which itself is .electrically conductive as a substantially homogeneous, as opposed to layered, structure. Depending on the wavelenths of visible, invisible and near light wavelengths. Thus, in selective situations, the photodetector of the instant invention not only rejects electromagnetic and radio frequency radiation, but may also reject undesirable ambient or other light.
• the window may be vitrious, crystalline or polycrystalline.

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• Light Receiving Elements (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
• Photometry And Measurement Of Optical Pulse Characteristics (AREA)

Priority Applications (3)

Applications Claiming Priority (2)

Publications (1)

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Citations (4)

• 1981
  • 1981-04-01 US US06/250,955 patent/US4394572A/en not_active Expired - Lifetime
• 1982
  • 1982-03-10 GB GB08225872A patent/GB2109993B/en not_active Expired
  • 1982-03-10 JP JP57501231A patent/JPS58500465A/ja active Pending
  • 1982-03-10 EP EP82901219A patent/EP0075584A1/en not_active Withdrawn
  • 1982-03-10 DE DE823239731T patent/DE3239731T1/de active Granted
  • 1982-03-10 WO PCT/US1982/000283 patent/WO1982003493A1/en not_active Ceased
  • 1982-03-10 NL NLAANVRAGE8220116,A patent/NL185377C/xx not_active IP Right Cessation
  • 1982-03-10 AU AU83316/82A patent/AU8331682A/en not_active Abandoned
  • 1982-03-31 CA CA000400210A patent/CA1177942A/en not_active Expired

Patent Citations (4)

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