500nm Bandpass Filter

ositioned in the green region of the visible spectrum, 500nm light possesses specific photon energy and wavelength concentration, enabling selective interaction with target materials and penetration through specific media.

  • Application 1: (Fluorescence Microscopy) In fluorescence microscopy, the 500nm bandpass filter precisely isolates target emission signals (e.g., green fluorescent protein, GFP) by blocking stray excitation light, significantly enhancing imaging contrast and resolution for detailed cellular observation.
  • Application 2: (Water Quality Monitoring) Used in environmental monitoring devices, this filter separates the characteristic absorption/emission light of chlorophyll-a around 500nm in water samples, facilitating accurate quantification of algae concentration by eliminating interference from irrelevant wavelengths.
  • Application 3: (Spectroscopic and Industrial Inspection) When integrated with optical instruments such as fiber optic spectrometers, the 500nm bandpass filter extracts targeted wavelength signals from complex light sources, enabling critical applications including semiconductor surface defect detection and biomolecular recognition in biosensor technologies.

Technical Guide for 500nm Filter Selection in Targeted Applications

1. Biological Fluorescence Imaging Systems

Application Scenario

Used in fluorescence microscopy or flow cytometry to detect emission signals from markers like green fluorescent protein (GFP) and sodium fluorescein, such as monitoring intracellular ion concentrations (e.g., detection of sodium ion probe SBFI AM).

Filter Configuration Scheme

a. Excitation Filter:

Center wavelength 488nm (±2 nm), full width at half maximum (FWHM) 20 nm, transmittance > 90%, cut-off region OD>4 (200–460 nm and above 500 nm).

b. Dichroic Mirror:

Reflects 400–490 nm, transmits 500–700 nm, transition band <5 nm, reflectance > 95%.

c. Emission Filter:

Center wavelength 500nm (±2 nm), FWHM 30 nm, transmittance > 85%, cut-off region OD>4 (200–480 nm and above 550 nm).

Selection Logic

  • Excitation End: The 488nm narrow-band filter precisely matches GFP's excitation peak (488nm), eliminating interference from other wavelengths. High transmittance ensures excitation light intensity, while the OD>4 cut-off region blocks stray light effectively.
  • Dichroic Mirror: A steep transition band (<5 nm) physically separates excitation and emission light, reducing crosstalk. It reflects excitation light below 490 nm and transmits fluorescence signals above 500 nm, enhancing system efficiency.
  • Emission End: The 500nm bandpass filter selectively transmits GFP's main emission peak (509nm), with a 30nm bandwidth accommodating signal fluctuations. The OD>4 cut-off region suppresses residual excitation light and background noise, improving the signal-to-noise ratio by over 3 times.

Core Problem Solved

  • Signal Purity: The three-layer filtering structure (excitation-dichroic-emission) limits excitation light leakage to <0.01%, ensuring authentic fluorescence signal acquisition.
  • Detection Sensitivity: The 30nm bandwidth balances signal capture range and background suppression, reducing fluorescence intensity detection error to ±2% compared to traditional 50nm bandwidth filters.

2. Retinal Angiography

Application Scenario

In ophthalmic diagnosis, enhancing retinal vessel contrast through red-free angiography (RFA) to detect diseases like diabetic retinopathy and macular degeneration.

Filter Configuration Scheme

a. Excitation Filter:

Center wavelength 488nm (±2 nm), FWHM 10 nm, transmittance > 85%, cut-off region OD>3 (200–460 nm and above 500 nm).

b. Emission Filter:

Center wavelength 500nm (±2 nm), FWHM 20 nm, transmittance > 80%, cut-off region OD>3 (200–480 nm and above 550 nm).

Selection Logic

  • Excitation End: The 10nm ultra-narrow bandwidth filter precisely isolates argon blue laser (488nm), minimizing retinal photodamage. The OD>3 cut-off region eliminates visible light interference, enhancing vascular imaging contrast.
  • Emission End: The 500nm bandpass filter leverages hemoglobin's strong green light absorption (absorption coefficient 0.8 mm⁻¹ at 500nm) to enhance differences between blood vessels and background tissues. The 20nm bandwidth design maintains signal intensity while suppressing autofluorescence (e.g., lipofuscin emission under 350nm excitation).

Core Problem Solved

  • Structural Resolution: Wavelength selection via the 500nm filter improves retinal vessel boundary clarity by 40%, enabling detection of microaneurysms with diameter <50μm.
  • Multimodal Compatibility: This configuration supports both sodium fluorescein angiography (488nm excitation, 500nm emission) and red-free mode (filter removal), allowing functional switching on the same device and reducing clinical operation complexity.

3. Extended Industrial Inspection Applications

Potential Scenarios

  • Food sorting: Detecting chlorophyll content on fruit surfaces using 500nm filters to determine ripeness.
  • Semiconductor manufacturing: Monitoring photoresist fluorescence characteristics at 500nm during lithography processes.

Configuration Recommendations

  • Bandpass Filter: Center wavelength 500nm (±5 nm), FWHM 40 nm, transmittance > 80%, cut-off region OD>2 (200–480 nm and above 550 nm).
  • Long-Pass Filter: Cut-off wavelength 500nm, transition band <10 nm, transmittance > 90% (500–700 nm), OD>3 (200–480 nm).

Technical Value Proposition

  • Spectral Specificity: The 40nm bandwidth differentiates chlorophyll a (680nm emission) from chlorophyll b (730nm emission), achieving a ripeness misjudgment rate <1% in food sorting.
  • Process Compatibility: The long-pass filter integrates into online inspection systems for real-time monitoring of photoresist exposure uniformity, with a response time <10 ms.

Key Selection Parameters by Application

Core Parameter Configurations for Each Scenario:

a. Biological Fluorescence Imaging

  • Center Wavelength: 500±2 nm
  • Bandwidth (FWHM): 30 nm
  • Transmittance: >85%
  • Cut-off Depth: OD>4 (200–480 nm)
  • Core Requirements: High signal-to-noise ratio, minimal excitation light leakage

b. Retinal Angiography

  • Center Wavelength: 500±2 nm
  • Bandwidth (FWHM): 20 nm
  • Transmittance: >80%
  • Cut-off Depth: OD>3 (200–480 nm)
  • Core Requirements: High contrast, resistance to photodamage

c. Industrial Inspection

  • Center Wavelength: 500±5 nm
  • Bandwidth (FWHM): 40 nm
  • Transmittance: >80%
  • Cut-off Depth: OD>2 (200–480 nm)
  • Core Requirements: Broad applicability, rapid response

These configurations enable 500nm filters to efficiently extract target signals and suppress interference across diverse scenarios. The selection logic hinges on balancing spectral matching and system compatibility, ensuring optimal performance in scientific research, medical diagnosis, and industrial automation.

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