Light Source/LED (for optical encoders): Optical Power 1-5mW

Q: Why are infrared LEDs commonly used in optical encoders?

Infrared LEDs (850-950nm) minimize interference from ambient visible light, provide better signal-to-noise ratios, and have superior aging characteristics compared to visible LEDs, ensuring long-term measurement stability.

Q: How does LED quality affect encoder accuracy?

LED intensity stability, wavelength consistency, thermal characteristics, and beam collimation directly impact encoder resolution, repeatability, and temperature performance. High-quality LEDs maintain consistent output over temperature variations and operational life.

Q: Can visible red LEDs be used instead of infrared?

Yes, red LEDs (650-670nm) are used in some applications where visual alignment is helpful or specific material responses are required, but they generally have shorter lifetimes and greater sensitivity to ambient light interference than infrared options.

Component Specifications

Definition

A specialized LED component engineered to emit consistent, collimated infrared or visible light for optical encoder systems. It provides the illumination source that interacts with encoder discs or scales to generate position feedback signals through photodetectors. These LEDs are optimized for minimal thermal drift, long-term intensity stability, and precise wavelength characteristics required for accurate displacement measurement.

Working Principle

Operates by converting electrical current into photons through semiconductor electroluminescence. When forward-biased, electrons recombine with holes in the active region, emitting light at specific wavelengths (typically 850-950nm infrared or 650-670nm red). This light passes through or reflects off encoder patterns, creating modulated signals detected by photodiodes or phototransistors to determine position, speed, or direction.

Materials

AlGaAs/GaAs semiconductor chips for infrared (850-950nm), InGaAlP for red (650-670nm), ceramic or metal-ceramic substrates, gold wire bonding, silicone or epoxy encapsulation with precise optical windows, Kovar or copper alloy leads

Technical Parameters

Parameter	Typical range	Notes & selection driver
Package	3mm/5mm radial, surface mount (SMD)
Lifetime	>50,000 hours
Wavelength	850nm ±10nm (typical)
Optical Power	1-5mW
Viewing Angle	15-30° (collimated)
Rise/Fall Time	<100ns
Forward Voltage	1.8-2.2V @ 20mA
Operating Temperature	-40°C to +85°C

Ranges are indicative industry figures for RFQ preparation, not a supplier commitment. Confirm every value and standard with the legal manufacturer before ordering.

Standards

ISO 16063-21, IEC 60747-5-5, JEDEC JESD22

Parent Products

This component is used in the following industrial products

Encoder/Feedback Device

A device that converts mechanical motion into electrical signals to provide position, speed, or direction feedback in motion control systems.

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Engineering Analysis

Risks & Mitigation

Thermal drift affecting accuracy
Intensity degradation over time
Wavelength shift with temperature
Contamination of optical surfaces
ESD damage during handling

FMEA Triads

Trigger: Thermal expansion mismatches in packaging
Failure: Wavelength drift and intensity variation
Mitigation: Use matched CTE materials, thermal management design, temperature compensation circuits

Trigger: Semiconductor aging and defect migration
Failure: Gradual light output degradation
Mitigation: Burn-in testing, derated operation, quality semiconductor processes

Trigger: Moisture ingress or chemical contamination
Failure: Optical surface fogging or corrosion
Mitigation: Hermetic sealing, conformal coatings, clean manufacturing environments

Industrial Ecosystem

Compatible With

Typical Suppliers & Equivalents

Compliance & Inspection

Tolerance

Wavelength tolerance ±5nm, intensity variation <10% over temperature range, angular alignment ±2°

Test Method

Spectroradiometry for wavelength/spectral distribution, integrating sphere for total flux, L-I-V characterization, accelerated life testing per IESNA LM-80

Procurement Evaluation Criteria

A practical evidence checklist for RFQ preparation and supplier evaluation.

Technical documentation

Request current drawings, revision history, and a signed specification sheet.

Manufacturing capability

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Inspection readiness

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Supplier transparency

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Frequently Asked Questions

Why are infrared LEDs commonly used in optical encoders?