# US 10,873,686 B2 · Explosion-proof thermal imaging system > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,873,686 B2 - Document ID: US10873686B2 - Status: Granted - Kind: B2 - Application number: 14/755,107 - Filed: 2015-06-30 - Published: 2017-01-05 - Granted: 2020-12-22 - Earliest claimed: 2015-06-30 - Assignees: Rosmeount Inc. - Applicants: Rosemount Inc. - Inventors: Jason H. Rud; Andrew J. Kitzman; Sascha Ulrich Kienitz; Ulrich Kienitz; Johannes Gentz - Web page: https://patentgrep.com/patent/US10873686B2 ## CPC - H04N 23/51: Housings - G01J 5/044: {Environment with strong vibrations or shocks} - G01J 5/048: {Protective parts} - G01J 5/0806: Focusing or collimating elements, e.g. lenses or concave mirrors - G01J 5/0808: Convex mirrors - G01J 5/0816: {using attenuators} - G02B 7/007: {Pressure-resistant sight glasses} - H04N 23/23: from thermal infrared radiation - G01J 2005/0077: {Imaging} - H04N 23/555: {for picking-up images in sites, inaccessible due to their dimensions or hazardous conditions, e.g. endoscopes or borescopes} - H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION - G01J: MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY (light sources F21, H01J, H01K, H05B; investigating properties of materials by optical means G01N) - G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS ## Abstract A thermal imaging system is provided. The thermal imaging system includes an explosion-proof housing with an optical window configured to contain an explosive pressure. The optical window allows electromagnetic thermal energy to pass. A thermal imaging sensor is disposed within the explosion-proof housing. Thermal imaging electronics are coupled to the thermal imaging sensor and configured to provide at least one thermal image based on a signal from the thermal imaging sensor. A lens assembly is disposed at least in front of the optical window external to the explosion-proof housing. A composite optical window for thermal imaging is also provided. In another embodiment, a thermal imaging system includes an explosion-proof housing having an optical window configured to contain an explosive pressure. An infrared (IR) camera is disposed within the explosion-proof housing. A reflector reflects electromagnetic thermal energy to the IR camera, but prevent an object from impacting the optical window. ## Claims ### Claim 1 A thermal imaging system comprising: a metallic explosion-proof housing including an optical window, wherein the explosion-proof housing complies with at least one explosion-proof rating, the optical window allowing electromagnetic thermal energy to pass through; a thermal imaging sensor disposed within the explosion-proof housing; thermal imaging electronics coupled to the thermal imaging sensor and configured to provide at least one thermal image based on a signal from the thermal imaging sensor; at least one lens disposed at least in front of the optical window and external to the explosion-proof housing; and wherein the IR transparent optical window is formed of an IR transparent, impact resistant layer comprised of a first material sandwiched between a first and a second IR transparent layer comprised of a second material. ### Claim 2 (depends on 1) The thermal imaging system of claim 1, wherein the at least one lens includes a first and second lens disposed in front of the IR transparent optical window, wherein the first lens is external to the explosion proof housing. ### Claim 3 (depends on 2) The thermal imaging system of claim 2, wherein the at least one lens further includes a third lens disposed within the explosion-proof housing and configured to focus the electromagnetic thermal energy on the thermal imaging sensor. ### Claim 4 (depends on 1) The thermal imaging system of claim 1, wherein the IR transparent optical window comprises of zinc selenide. ### Claim 5 (depends on 1) The thermal imaging system of claim 1, wherein the lens assembly includes a housing having a diameter less than 1 inch. ### Claim 6 (depends on 1) The thermal imaging system of claim 1, wherein the thermal imaging electronics are disposed within the explosion-proof housing. ### Claim 7 (depends on 4) The thermal imaging system of claim 4, wherein the thermal imaging sensor obtains the at least one thermal image substantially completely through a reflector, wherein the reflector is disposed to prevent an object from impacting the optical window. ### Claim 8 (depends on 1) The thermal imaging system of claim 1 wherein the at least one lens comprises a lens assembly, the lens assembly comprising: a first forward-facing convex lens disposed in front of the optical window and external to the explosion-proof housing; a second forward-facing convex lens disposed behind the first lens and in front of the optical window; a third forward-facing convex lens disposed behind the optical window and within the explosion-proof housing; and a fourth rearward-facing convex lens disposed behind the third lens and within the explosion-proof housing. ### Claim 9 (depends on 7) The thermal imaging system of claim 7 wherein the reflector is external to the explosion-proof housing. ### Claim 10 (depends on 9) The thermal imaging system of claim 9 wherein the reflector comprises a parabolic mirror. ### Claim 11 (depends on 10) The thermal imaging system of claim 10 wherein the reflector is within a point of view of the thermal imaging sensor and reflects light, received from a surface outside of the point of view of the thermal imaging sensor, towards the thermal imaging sensor. ### Claim 12 (depends on 1) The thermal imaging system of claim 1 and further comprising a shroud disposed in front of the IR transparent optical window and having a diameter of less than 1 inch. ### Claim 13 (depends on 6) The thermal imaging system of claim 6, wherein the electronics are further configured to detect damage to the at least one lens based on the at least one thermal image. ### Claim 14 (depends on 13) The thermal imaging system of claim 13, wherein the electronics are further configured to generate an alert based on the detection of damage to the at least one lens. ### Claim 15 (depends on 1) The thermal imaging system of claim 1, wherein the first material comprises polyamide. ### Claim 16 (depends on 15) The thermal imaging system of claim 15, wherein the second material comprises zinc selenide. ### Claim 17 A composite optical window for thermal imaging, the composite optical window including: a first layer of material that passes thermal imaging electromagnetic radiation, but is subject to fracture; a second layer of material that passes thermal imaging electromagnetic radiation, but is also subject to fracture; and an IR-transparent, impact resistant, layer disposed between the first and second layers and, wherein each of the first and second layers contain an explosive pressure in accordance with at least one explosion-proof rating; and wherein each layer of the composite optical window is composed of only IR transparent materials. ### Claim 18 (depends on 17) The composite optical window of claim 17, wherein the first and second layers are formed of zinc selenide. ### Claim 19 (depends on 18) The composite optical window of claim 18, wherein the IR-transparent impact resistant layer comprises polyamide. ### Claim 20 (depends on 17) The composite optical window of claim 17 wherein the first layer is disposed in front of both the IR-transparent impact resistant layer and the second layer and can absorb a force from an impact of an object, such that the IR-transparent impact resistant layer can maintain a pressure bearing seal of an interior of an explosion proof housing in which the composite optical window is disposed, wherein the force being exerted upon impact by the object is at least 4 joules.