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Ink Mist Contamination Robust Optical Encoder

IP.com Disclosure Number: IPCOM000214950D
Publication Date: 2012-Feb-15
Document File: 4 page(s) / 393K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a detector design within transmissive encoders that addresses premature encoder failure by strategically placing the photodiode arrays (PDA) in multiple areas to prolong the life of the encoder in a printer application with a high concentration of aerosol.

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Avago Technologies                                                        

Ink Mist Contamination Robust Optical Encoder

Abstract

Disclosed is a detector design within transmissive encoders that addresses premature encoder failure by strategically placing the photodiode arrays (PDA) in multiple areas to prolong the life of the encoder in a printer application with a high concentration of aerosol.

Description

A.           Prior solutions and their disadvantages

Aerosols are byproducts produced during the printing process where unwanted ink mists are ejected along with the main droplets. These tiny droplets deposit and contaminate the codestips/codewheels as well as the active components (emitter and detector) of the encoders. A typical transmissive encoder has the photodiode arrays (PDA) arranged in a single array, with the detector aligned to the Light-Emitting Diode (LED) whereby the PDA are located in the middle of the beam spot created by the LED illuminations (Figure 1). This design subjects the encoder to a higher risk of failure when aerosol deposition is concentrated within the optical path of the encoder.

Figure 1: Typical construction of a transmissive encoder

Strategic placement of the PDA enables an increase in the performance and robustness of an encoder in an aerosol-contaminated environment.

B.           Problems solved by the invention

Current detectors are designed to be at the nominal position of an encoder (i.e., PDA are aligned to the center of bar/window of codestrip/wheel). During the printing process, aerosols accumulate and become the most concentrated in the center/middle region of the codestrip/wheel. (Figure 2)

Figure 2: Aerosol accumulates on codewheel/codestrip

In this case, the performance of the encoder degrades and eventually fails as most of the lights from the LED are blocked.

This invention solves the problem of premature encoder failure by strategically placing the PDA in multiple areas to prolong the life of the encoder in a printer application with a high concentration of aerosol.

C.           Advantages of the invention over what has been done before

The proposed designs have the following advantages:

·         Avoid areas with high aerosol concentrations

·         Enhance encoder performances with more PDA (or increase effective active are...