632.8nm / 633nm Bandpass Filters

632.8nm / 633nm bandpass filters are designed to transmit a selected red wavelength band around the He-Ne laser line while reducing unwanted out-of-band light.

Applications:
- 632.8nm He-Ne laser line cleanup
- Optical interferometry, alignment, and metrology systems
- Detector-side red laser signal isolation before cameras, photodiodes, or spectrometers
- Laser-based measurement and calibration setups
- Red-region optical sensing where the target signal is near 632–633nm

Bandwidth options:
- 2.9nm and 3nm FWHM for tighter He-Ne laser-line isolation
- 10nm FWHM for practical 632nm, 632.8nm, or 633nm laser signal cleanup with more passband margin

Select the bandwidth based on the laser wavelength, wavelength tolerance, detector sensitivity, blocking range, and required signal level.

632.8nm He-Ne laser line cleanup

Use CWL 632.8nm with 2.9–10nm FWHM for He-Ne laser line cleanup, source isolation, or detector-side laser signal selection.

632.8nm is the standard red helium-neon laser line. For He-Ne laser systems, key specs include CWL match near 632.8nm, FWHM, transmission at the laser line, and OD blocking across the unwanted wavelength range.

Optical interferometry, alignment, and metrology

Use CWL 632.8nm or 633nm with 2.9–10nm FWHM for interferometry, alignment, metrology, and laser-based measurement paths.

For these systems, the filter helps isolate the red laser line and reduce unwanted source background or stray light reaching the optical path or detector. Use 2.9–3nm FWHM for stronger laser-line isolation, or 10nm FWHM when more passband margin is preferred.

Detector-side red signal isolation

Use CWL 632.8nm or 633nm with 2.9–10nm FWHM before a silicon photodiode, CMOS/CCD camera, PMT, or spectrometer input when the target signal is near the He-Ne red line.

For detector-side filtering, the filter improves signal-to-background ratio by passing the red laser signal and reducing unwanted visible or broadband background. Use 2.9–3nm FWHM for stronger wavelength isolation, or 10nm FWHM when more signal level and alignment tolerance are needed.

$US4678324A - Range Finding by Diffraction$

US4678324A - Range Finding by Diffraction

Context: This patent describes a 3D range-finding system (often used in microscopy or machine vision) that projects a diffraction pattern onto an object to measure its surface profile and depth.

Usage of Filter: A 632.8 nm bandpass filter is placed in front of the detection system (camera or photodetector).

Function: The system typically uses a Helium-Neon (HeNe) laser source to project the diffraction grating. The filter is used to block all ambient light (sunlight, room lighting) while allowing the specific 632.8 nm laser light reflected from the object to pass through to the detector.

Result: This achieves a high signal-to-noise ratio, ensuring the system calculates the distance based only on the projected laser pattern and not on shadows or background illumination, resulting in precise sub-micron depth measurement.

US6809859B2 - Optical Filter and Fluorescence Spectroscopy System

Context: This patent details the construction of high-performance thin-film optical filters for use in fluorescence spectroscopy systems, where biological samples are excited by lasers to emit light.

Usage of Filter: A 632 nm bandpass filter acts as an excitation filter.

Function: It cleans up the output of a red laser source (like a HeNe or red diode laser), stripping away any spectral "noise" or sidebands, ensuring that only pure 632 nm light hits the sample to excite red-fluorescent dyes (such as Alexa Fluor 633 or Cy5).

Result: This minimizes "background noise" in the fluorescence signal. By ensuring the sample is struck only by the excitation wavelength, the detector can distinguish the faint emitted fluorescence signal (which is shifted to a higher wavelength) much more clearly, creating high-contrast biological images.

US5726805A - Optical Filter Including a Sub-wavelength Periodic Structure

Context: This patent covers "Guided-Mode Resonance" (GMR) filters, which use nano-scale grating structures to reflect or transmit extremely narrow wavelengths of light, often used in chemical sensors.

Usage of Filter: The patent describes a 632.8 nm bandpass filter functionality created by the sub-wavelength structure itself, designed to act as a narrowband probe filter.

Function: In a chemical sensing setup, this filter is tuned to reflect virtually 100% of the 632.8 nm probe beam while transmitting other wavelengths. When a chemical binds to the filter surface, the resonance shifts, and the 632.8 nm light suddenly transmits (or stops reflecting).

Result: This converts a chemical presence into a readable optical signal. The result is a highly sensitive, label-free chemical detector that can identify minute changes in refractive index (caused by gas or biological matter) by monitoring the intensity of the 632 nm beam.

Need Help Choosing a Product?

Share your requirement of spectral or your application goal.We will review and provide product recommendation to you.