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Integrated Infrared Filter in Photosensor housing

IP.com Disclosure Number: IPCOM000009988D
Original Publication Date: 2002-Nov-25
Included in the Prior Art Database: 2002-Nov-25
Document File: 1 page(s) / 40K

Publishing Venue

Siemens

Related People

Juergen Carstens: CONTACT

Abstract

Most common used photosensors are showing dependency to infrared light, so the sensors will give different results depending on the light source (daylight, artificial light, …). If such a sensor is imple-mented in the mobile devices to control backlight illumination, the customer will see a not intended varying behaviour of the light control. That’s why two components would be necessary. A photosensor and an infrared (IR) sensor have to be combined in one circuit to gain the difference between both signals, which would be the expected value for daylight without infrared radiation. An external IR-Filter in the device housing could be an expensive and difficult solution. Mechanical assembly may cause problems due to small dimensions and unequal materials. It is suggested to integrate the IR-Filter in the photosensor housing. This could be done by IR-resistive materials, special foils or coated glasses. Concerning the soldering ability the filter should be respec-tively heat resistant. At least the infrared part of the light does not influence the measurement result and the sensor will work properly within different light conditions.

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© SIEMENS AG 2002 file: 2001J19985.doc page: 1

Integrated Infrared Filter in Photosensor housing

Idea: Uwe Haessel, DE-Muenchen; Andreas Wipper, DE-Muenchen

Most common used photosensors are showing dependency to infrared light, so the sensors will give different results depending on the light source (daylight, artificial light, ...). If such a sensor is imple- mented in the mobile devices to control backlight illumination, the customer will see a not intended varying behaviour of the light control.

That's why two components would be necessary. A photosensor and an infrared (IR) sensor have to be combined in one circuit to gain the difference between both signals, which would be the expected value for daylight without infrared radiation. An external IR-Filter in the device housing could be an expensive and difficult solution. Mechanical assembly may cause problems due to small dimensions and unequal materials.

It is suggested to integrate the IR-Filter in the photosensor housing. This could be done by IR-resistive materials, special foils or coated glasses. Concerning the soldering ability the filter should be respec- tively heat resistant. At least the infrared part of the light does not influence the measurement result and the sensor will work properly within different light conditions.