# US 2021/0239609 A1 · Water content sensor > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2021/0239609 A1 - Document ID: US20210239609A1 - Status: Published application - Kind: A1 - Application number: 17/051,748 - Filed: 2019-07-26 - Published: 2021-08-05 - Earliest claimed: 2018-08-13 - Assignees: Hewlett-Packard Development Company, L.P. - Applicants: Hewlett-Packard Development Company, L.P. - Inventors: Sachiyo YAMADA; Yuichiro TOMISHIMA; Hirokazu YUKAWA - Web page: https://patentgrep.com/patent/US20210239609A1 ## CPC - G01N 21/3559: in sheets, e.g. in paper - G02B 5/208: {for use with infrared or ultraviolet radiation, e.g. for separating visible light from infrared and/or ultraviolet radiation} - G02B 5/26: Reflecting filters (G02B5/28 takes precedence) - G02B 26/0833: {the reflecting element being a micromechanical device, e.g. a MEMS mirror, DMD (G02B26/0825 takes precedence; micromechanical devices in general B81B)} - G02B 27/106: {for splitting or combining a plurality of identical beams or images, e.g. image replication} - G03G 15/5029: {by measuring the copy material characteristics, e.g. weight, thickness} - G03G 21/203: {Humidity} - G03G 2215/00616: Optical detector - G03G 2215/0062: infrared - G03G 2215/00776: of humidity or moisture influencing copy sheet handling - G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q) - G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS - G03G: ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY ## Abstract A water content sensor for a recording medium includes a single light emitting part, a wavelength separation device and a detector device. The single light emitting part emits infrared light in a wavelength range including an absorption wavelength of water along one incident light path toward the recording medium. The wavelength separation device separates infrared light, either reflected from or transmitted through the recording medium, into a first light in a first wavelength range including the absorption wavelength of water and a second light in a second wavelength range excluding the first wavelength range. The detector device receives the first light in the first wavelength range and the second light in the second wavelength range, and generates a first output corresponding to an intensity of the first light received and a second output corresponding to an intensity of the second light received, respectively. ## Claims ### Claim 1 A water content sensor to determine a water content ratio of a recording medium, comprising: a single light emitting part to emit infrared light in a wavelength range including an absorption wavelength of water along one incident light path toward the recording medium; a wavelength separation device to separate one of infrared light reflected from the recording medium along a reflection light path and infrared light transmitted through the recording medium along a transmission light path, into a first light in a first wavelength range including the absorption wavelength of water and a second light in a second wavelength range excluding the first wavelength range; and a detector device to receive the first light in the first wavelength range and the second light in the second wavelength range, and to generate a first output corresponding to an intensity of the first light received and a second output corresponding to an intensity of the second light received, respectively. ### Claim 2 (depends on 1) The water content sensor according to claim 1, wherein the detector device comprises: a first detector to receive the first light in the first wavelength range and to generate the first output corresponding to the intensity of the first light received; and a second detector to receive the second light in the second wavelength range and to generate the second output corresponding to the intensity of the second light received. ### Claim 3 (depends on 1) The water content sensor according to claim 1, wherein the wavelength separation device includes a dichroic mirror. ### Claim 4 (depends on 1) The water content sensor according to claim 1, wherein the wavelength separation device comprises a first optical filter having a passband corresponding to the first wavelength range to generate the first light, and a second optical filter having a passband corresponding to the second wavelength range to generate the second light. ### Claim 5 (depends on 1) The water content sensor according to claim 1, wherein, when the wavelength separation device is disposed to receive the infrared light reflected from the recoding medium along the one reflection light path, the wavelength separation device is disposed in a position to receive substantially no specular reflected light of the infrared light reflected from the recording medium. ### Claim 6 (depends on 1) The water content sensor according to claim 1, comprising a light path-merging member and a plurality of light emitting parts including the single light emitting part, at least one of the plurality of light emitting parts to emit infrared light in a wavelength range including the absorption wavelength of water, and the light path-merging member to merge light from the plurality of light emitting parts into one light path and to emit light merged into the one light path to the recording medium. ### Claim 7 (depends on 1) The water content sensor according to claim 1, comprising a computing part to determine a water content ratio of the recording medium based, at least in part, on the first output and the second output. ### Claim 8 (depends on 1) The water content sensor according to claim 1, wherein the wherein the single light emitting part comprises an LED. ### Claim 9 (depends on 1) The water content sensor according to claim 1, wherein the wavelength separation device comprises: a MEMS mirror to receive either one of the infrared light reflected from the recording medium along the reflection light path and the infrared light transmitted through the recording medium along the transmission light path, wherein the MEMS mirror is operable in a first position and in a second position; and an optical member mounted to the MEMS mirror to emit the first light in the first wavelength range of the infrared light received by the MEMS mirror, along a direction incident on the detector device and to emit the second light in the second wavelength range of the infrared light received by the MEMS mirror, along a direction not incident on the detector device, when the MEMS mirror is in the first position; and to emit the second light in the second wavelength range of the infrared light received by the MEMS mirror toward the detector device and to emit the first light in the first wavelength range of the infrared light received by the MEMS mirror along a direction not incident on the detector device, when the MEMS mirror is in the second position. ### Claim 10 A water content sensor to determine a water content ratio of a recording medium, comprising: a single light emitting part to emit infrared light in a wavelength range including an absorption wavelength of water along one incident light path to the recording medium; a filter switching device comprising: a filter portion having, as a passband, a predetermined wavelength range including the absorption wavelength of water in received infrared light corresponding to one of infrared light reflected from the recording medium along one reflection light path and infrared light transmitted through the recording medium along one transmission light path; and a light transmissive portion to transmit light in an entire wavelength range, including the predetermined wavelength range, of the received infrared light; and a detector to receive light transmitted through the filter portion and the light transmissive portion of the filter switching device to generate an output corresponding to an intensity of the received light, the filter switching device to alternately position the filter portion and the light transmissive portion at a predetermined position to receive the received infrared light, and the filter switching device being disposed relative to the detector so that: when the filter portion is disposed in the predetermined position, light transmitted through the filter portion, of the received infrared light received by the filter portion, is sent to the detector; and when the light transmissive portion is disposed in the predetermined position, light transmitted through the light transmissive portion, of the received infrared light received by the light transmissive portion, is sent to the detector. ### Claim 11 (depends on 10) The water content sensor according to claim 10, wherein, when the filter portion and the light transmissive portion are each disposed in the predetermined position to receive the infrared light reflected from the recording medium along the one reflection light path, the predetermined position is in a position to receive substantially no specular reflected light of the infrared light reflected from the recording medium. ### Claim 12 An image forming device having a sensor to determine a water content ratio of a recording medium, comprising: a single light emitting part to emit infrared light in a wavelength range including an absorption wavelength of water along one incident light path toward the recording medium; a wavelength separation device to separate one of infrared light reflected from the recording medium along one reflection light path and infrared light transmitted through the recording medium along one transmission light path, into a first light in a first wavelength range including the absorption wavelength of water and a second light in a second wavelength range excluding the first wavelength range; and a detector device to receive the first light in the first wavelength range and the second light in the second wavelength range, and to generate a first output corresponding to an intensity of the first light received and a second output corresponding to an intensity of the second light received, respectively. ### Claim 13 (depends on 12) The image forming device according to claim 12, wherein the detector device comprises: a first detector to receive the first light in the first wavelength range and to generate the first output corresponding to the intensity of the first light received; and a second detector to receive the second light in the second wavelength range and to generate the second output corresponding to the intensity of the second light received. ### Claim 14 (depends on 12) The image forming device according to claim 12, comprising a light path-merging member and a plurality of light emitting parts including the single light emitting part, at least one of the plurality of light emitting parts to emit infrared light in a wavelength range including the absorption wavelength of water, and the light path-merging member to merge light from the plurality of light emitting parts into one light path and to emit light merged into the one light path to the recording medium. ### Claim 15 (depends on 12) The image forming device according to claim 12, wherein the wavelength separation device comprises: a MEMS mirror to receive either one of the infrared light reflected from the recording medium along one reflection light path and the infrared light transmitted through the recording medium along one transmission light path, wherein the MEMS mirror is operable in a first position and in a second position; and an optical member mounted to the MEMS mirror to emit the first light in the first wavelength range, of the infrared light received by the MEMS mirror, along a direction incident on the detector device and to emit the second light in the second wavelength range excluding the light in the first wavelength range, of the infrared light received by the MEMS mirror, along a direction not incident on the detector device when the MEMS mirror is in the first position; and to emit the second light in the second wavelength range of the infrared light received by the MEMS mirror toward the detector device and to emit the first light in the first wavelength range of the infrared light received by the MEMS mirror along a direction not incident on the detector device when the MEMS mirror is in the second position.