505nm Bandpass Filter

505nm light falls in the green visible spectrum, offering a balance between penetration depth and minimal interference from ambient light, with high sensitivity to human vision and specific biological/chemical interactions.

  • Application 1: In fluorescence microscopy, to isolate the emission signal from green fluorescent proteins (GFPs) by blocking unwanted wavelengths and enhancing the clarity of cellular imaging.
  • Application 2: In environmental spectroscopy, to accurately measure chlorophyll fluorescence in plants or algae by filtering out background light and isolating the 505nm spectral band indicative of photosynthetic activity.
  • Application 3: In optical sensing systems, to enable precise detection of specific dyes or biomarkers in medical diagnostics that emit or reflect strongly at 505nm, ensuring high signal-to-noise ratio for reliable results.

505nm Filter Selection Guide: Application-Specific Configuration Strategies for Biological Fluorescence Imaging and Industrial Vision Inspection

I. Biological Fluorescence Imaging Systems

Application Scenario

In fluorescence microscopes or flow cytometers, 505nm filters are used to isolate emission signals from fluorescent markers (e.g., GFP green fluorescent protein) for high-contrast imaging. For example, GFP emits light around 505nm when excited by 488nm light, requiring precise signal extraction through filter combinations.

Filter Configuration and Parameter Requirements

1. Excitation Filter

  • Type: 488nm Narrowband Bandpass Filter
  • Key Parameters:
  • Central Wavelength: 488nm ±2nm
  • Full Width at Half Maximum (FWHM): 10–20nm
  • Passband Transmission: ≥90%
  • Blocking Optical Density (OD): ≥4 (at 505nm)
  • Function: Permits only 488nm excitation light to pass through, suppressing interference from other wavelengths.

2. Dichroic Mirror

  • Type: 490nm Longpass Dichroic Mirror
  • Key Parameters:
  • Cutoff Wavelength: 490nm
  • Reflectance: ≥98% (400–490nm)
  • Transmittance: ≥85% (500–700nm)
  • Function: Reflects 488nm excitation light onto the sample while transmitting 505nm fluorescence signals to the detector.

3. Emission Filter

  • Type: 505nm Narrowband Bandpass Filter
  • Key Parameters:
  • Central Wavelength: 505nm ±2nm
  • Full Width at Half Maximum (FWHM): 8–20nm
  • Passband Transmission: ≥90%
  • Blocking Optical Density (OD): ≥6 (at 488nm)
  • Function: Allows only 505nm fluorescence to pass through, completely blocking residual excitation light and avoiding background noise.

Selection Logic and Problem Solving

  • Bandwidth Control: The narrow bandwidth (10–20nm) of the excitation filter ensures pure excitation light, minimizing non-specific fluorescence; the even narrower bandwidth (8–20nm) of the emission filter further suppresses excitation light leakage, enhancing the signal-to-noise ratio.
  • Blocking Depth: The high blocking OD (≥6 at 488nm) of the emission filter attenuates excitation light intensity to below 0.0001%, resolving image blur caused by residual excitation light.
  • Dichroic Mirror Matching: The 490nm cutoff wavelength seamlessly aligns with excitation/emission spectra, ensuring efficient reflection of excitation light and lossless transmission of fluorescence signals to avoid signal attenuation from insufficient beam splitting.

II. Industrial Vision Inspection Systems

Application Scenario

In defect detection for transparent materials (e.g., glass, plastic), 505nm green light enhances the contrast of surface scratches, bubbles, and other defects. Using 505nm LED light sources with filters can suppress surface reflection and highlight defect features.

Filter Configuration and Parameter Requirements

1. Light Source Filter

  • Type: 505nm Bandpass Filter
  • Key Parameters:
  • Central Wavelength: 505nm ±5nm
  • Full Width at Half Maximum (FWHM): 20–50nm
  • Passband Transmission: ≥85%
  • Blocking Optical Density (OD): ≥3 (at 400–480nm and 530–1100nm)
  • Function: Restricts the LED light source spectrum to ensure only 505nm green light illuminates the sample, reducing ambient light interference.

2. Camera Filter

  • Type: 505nm Bandpass Filter
  • Key Parameters:
  • Central Wavelength: 505nm ±5nm
  • Full Width at Half Maximum (FWHM): 20–50nm
  • Passband Transmission: ≥85%
  • Anti-Reflective Coating: Reflectance ≤0.2% (400–700nm)
  • Function: Ensures the camera only receives 505nm signals, eliminating surface reflections and stray light to improve defect recognition accuracy.

Selection Logic and Problem Solving

  • Bandwidth Selection: The wider FWHM (20–50nm) improves light source energy utilization while retaining sufficient spectral range for different material fluorescence characteristics, avoiding signal weakness from overly narrow bandwidths.
  • Anti-Reflective Design: The AR coating on the camera filter reduces surface reflectance from 4% to below 0.2%, solving overexposure issues caused by specular reflection on transparent materials.
  • Blocking Depth: A blocking OD ≥3 effectively excludes UV and IR interference (e.g., fluorescence from plastic additives or IR radiation from equipment heat), ensuring stable detection results.

III. Key Parameter Comparison and Selection Recommendations

Biological Fluorescence Imaging vs. Industrial Vision Inspection

  • Central Wavelength Precision
  • Biological Imaging: ±2nm (high spectral matching)
  • Industrial Inspection: ±5nm (balanced versatility)
  • Full Width at Half Maximum (FWHM)
  • Biological Imaging: 8–20nm (high resolution)
  • Industrial Inspection: 20–50nm (high energy efficiency)
  • Blocking Optical Density (OD)
  • Biological Imaging: OD≥6 (excitation light suppression)
  • Industrial Inspection: OD≥3 (ambient light suppression)
  • Anti-Reflective Coating
  • Biological Imaging: Optional (dependent on optical design)
  • Industrial Inspection: Essential (reduces surface reflection)
  • Damage Threshold
  • Biological Imaging: Medium-low (for normal light intensity)
  • Industrial Inspection: Medium-high (adapts to high-power LEDs)

Conclusion

Selecting 505nm filters requires focusing on two core principles: spectral matching and interference suppression. Biological fluorescence imaging prioritizes narrow bandwidths and high blocking depths for signal purification, while industrial inspection emphasizes energy efficiency and anti-reflective designs for defect contrast enhancement. By configuring filter parameters rationally, key issues such as background noise and signal attenuation in specific applications can be addressed, maximizing system performance.

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