632nm Bandpass Filter

632nm light is a visible red light with high monochromaticity and coherence, commonly emitted by helium-neon lasers.

  • Application 1: In optical interferometry, to isolate the 632nm laser light for precise distance or surface profile measurements by blocking unwanted wavelengths.
  • Application 2: In biomedical fluorescence microscopy, to filter out the 632nm excitation light and allow only the specific fluorescence signals within the desired band to pass for accurate cellular imaging.
  • Application 3: In laser alignment systems, to ensure pure 632nm laser beam transmission for guiding industrial machinery or construction equipment by eliminating stray light interference.
  • 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

    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

    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.

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