532nm 대역통과 필터

Context: This patent application describes a flow cytometer, a device used to count and analyze microscopic particles (like cells) by suspending them in a stream of fluid and passing them through an electronic detection apparatus.

Usage of Filter: The 532nm bandpass filter is placed specifically in front of a photodiode detector.

Function: It is used to isolate the scattered light or fluorescence that matches the 532nm excitation source. When a particle passes through the 532nm laser beam, it scatters light. The filter ensures the detector only sees this specific wavelength, blocking ambient light or signals from other lasers (like red or blue lasers used simultaneously in the system).

Result: The filter allows the system to accurately trigger a detection event. "When the photodiode with the 532 nm bandpass filter detects a response, the particle is [confirmed to be] in front of the 532 nm laser," allowing for precise timing and sequencing of data acquisition.

Context: These patent documents often relate to measuring Second Harmonic Generation (SHG), a nonlinear optical process where two photons interact to form a new photon with twice the energy (half the wavelength).

Usage of Filter: A 532nm bandpass filter is placed in front of a Photomultiplier Tube (PMT) detector.

Function: In this setup, an infrared laser (1064nm) hits a sample. The sample generates a weak "second harmonic" signal at exactly half the wavelength—532nm. The bandpass filter is crucial here because it blocks the intense 1064nm pump laser light while allowing only the faint 532nm signal to pass to the detector.

Result: It achieves a high Signal-to-Noise Ratio (SNR), enabling the detection of molecular orientation in materials like zeolites or biological tissues without blinding the sensitive PMT with the original infrared laser beam.

Context: This patent, assigned to NASA, describes a compact Raman sensor designed for planetary exploration (e.g., lunar rovers) to identify unknown minerals and substances remotely ("standoff" detection) without needing to collect a sample physically.

The Bandpass Filter is used as: A Laser Line Clean-Up Filter in the excitation path.

In this optical setup, a 532nm pulsed laser is used to illuminate the target. The 532nm bandpass filter is placed immediately after the laser source but before the beam expander or the target.

Its specific job is to transmit only the narrow 532nm laser line while blocking any unwanted "spectral noise," such as plasma glow or spontaneous emission (fluorescence) generated by the laser hardware itself.

Achieving this result:

High Signal Purity: By stripping away non-532nm wavelengths before they hit the sample, the filter prevents "false peaks" from appearing in the data.

Improved Sensitivity: Since Raman signals are incredibly weak (1 photon in a million), even faint background noise from the laser source can drown them out. The bandpass filter ensures that any light detected at wavelengths other than 532nm is genuinely from the sample (Raman scattering), not leakage from the laser.