525nm Bandpass Filter

The 525nm bandpass filter is precisely engineered to transmit green light at 525 nanometers while blocking unwanted wavelengths. This wavelength sits in the optimal green region of the visible spectrum, offering excellent balance between penetration depth and minimal optical interference.

Technical Specifications:

  • Center wavelength: 525nm ± 2nm
  • Peak transmission: >90% at center wavelength
  • Blocking: OD 4-6 outside passband
  • Available bandwidths: 10nm, 25nm, 40nm FWHM
  • Substrate: High-quality optical glass
  • Coating: Hard dielectric multilayer

Key Applications:

Fluorescence Microscopy:

  • Isolates emission signals from Green Fluorescent Proteins (GFPs)
  • Enhances cellular imaging clarity and contrast
  • Reduces background fluorescence for cleaner images

Environmental Monitoring:

  • Measures chlorophyll-a concentrations in water samples
  • Targets specific absorption/emission at 525nm
  • Enables accurate spectrophotometric analysis

Industrial Laser Systems:

  • Ensures precise 525nm wavelength transmission
  • Improves accuracy in distance sensing applications
  • Enhances machine calibration and alignment systems

Additional Applications:

  • Flow cytometry: Cell sorting and analysis
  • Confocal microscopy: High-resolution imaging
  • Machine vision: Color-specific inspection systems
  • Phototherapy: Medical light treatment devices
  • Optical instrumentation: Spectral analysis equipment

Why Choose 525nm Filters:

  • Optimal wavelength for green fluorophore detection
  • Excellent signal-to-noise ratio
  • Minimal tissue autofluorescence interference
  • High quantum efficiency with common detectors
  • Stable performance across temperature ranges

Our 525nm bandpass filters deliver exceptional performance for applications requiring precise green light transmission with superior blocking characteristics.

525nm Filter Application and Selection Guide

I. Fluorescence Detection in Flow Cytometry

Application Scenario

In flow cytometry, the goal is to detect fluorescently labeled cell surface antigens or intracellular components. For example, when using FITC (Fluorescein Isothiocyanate) - conjugated antibodies, the excitation wavelength is 488nm, and the emission spectrum peaks at approximately 525nm. Filters are required to separate the excitation light from the fluorescent signal, ensuring detection specificity.

Filter Configuration

1. Emission Filter
  • Central Wavelength: 525nm
  • Full Width at Half Maximum (FWHM): 30nm (e.g., 530/30nm filter)
  • Type: Interference-based bandpass filter
  • Transmittance: ≥90%
  • Stopband Optical Density (OD): ≥4 (in the 488nm excitation band)
2. Dichroic Mirror
  • Reflection Band: 480–500nm (reflects excitation light)
  • Transmission Band: 520–550nm (transmits fluorescent signal)
  • Type: Long-pass dichroic mirror (e.g., R488 T525 design)

Selection Rationale

  • Narrowband Bandpass Filter: The 30nm FWHM precisely matches the emission spectrum of FITC (515–545nm), effectively excluding interference from other fluorescent dyes (e.g., PE, APC) and improving the signal-to-noise ratio. For instance, using a filter with excessive bandwidth (e.g., 50nm) may introduce signal overlap from adjacent channels, leading to detection errors.
  • High Stopband OD: An OD ≥4 blocks 99.99% of excitation light leakage, preventing strong excitation light from masking weak fluorescent signals. As an example, when the excitation light intensity is 10,000 photons per second, an OD4 filter allows only 1 photon per second to pass, significantly reducing background noise.
  • Long-Pass Dichroic Mirror: This component reflects excitation light and transmits fluorescent signals, enabling optical path separation. The R488 T525 dichroic mirror, for example, reflects 488nm laser light to the sample while allowing 525nm fluorescence to pass through to the detector, avoiding direct excitation light entry into the detection channel.

Problem Solved

  1. Signal Confusion: In traditional broad-spectrum detection, excitation and fluorescent signals often mix, causing false positives. The combination of a 525nm bandpass filter and dichroic mirror boosts fluorescent signal purity to over 95%.
  2. Insufficient Sensitivity: The narrowband filter, paired with high transmittance (≥90%), increases fluorescent signal intensity by 30%, making it suitable for detecting low-expression antigens (e.g., rare cell subpopulation analysis).

II. Green Object Detection in Machine Vision

Application Scenario

In industrial automation, machine vision systems are used to identify green components or defects. Examples include detecting green-marked resistors and capacitors on electronic component production lines or assessing the ripeness of green fruits and vegetables in food sorting.

Filter Configuration

1. Bandpass Filter (Detection end)
  • Central Wavelength: 525nm
  • FWHM: 50nm
  • Type: Interference-based bandpass filter
  • Transmittance: ≥85%
  • Stopband Depth: OD ≥3 (in the 450–500nm and 550–650nm bands)
2. Illumination Filter
  • Central Wavelength: 525nm
  • FWHM: 80nm
  • Type: Absorptive or interference-based bandpass filter
  • Transmittance: ≥70%

Selection Rationale

  • Broad FWHM Design: The 50nm bandwidth covers the reflection spectrum of green objects (500–550nm) while excluding red (600–700nm) and blue (400–480nm) background interference. For example, using a 20nm narrowband filter during green plastic particle detection may cause missed detections due to color deviation.
  • High Stopband Depth: An OD ≥3 suppresses 99.9% of non-green light, increasing the contrast between green objects and the background by over 5 times. In a white background scenario, the signal-to-noise ratio of green marks improves from 2:1 to 10:1.
  • Synergy Between Illumination and Detection: The illumination filter (80nm bandwidth) provides monochromatic green light, enhancing the uniformity of object surface reflection. The detection-end 50nm filter further purifies the signal, reducing interference from ambient light (e.g., blue light in daylight).

Problem Solved

  1. Color Misjudgment: Traditional RGB cameras are prone to light fluctuations, leading to confusion between green, cyan, and yellow. The 525nm filter improves color recognition accuracy from 85% to 98% through spectral screening.
  2. Complex Background Interference: In multi-color environments (e.g., green components and red soldering points on circuit boards), the filter doubles the brightness of green areas, significantly reducing algorithm processing complexity and increasing recognition speed by 40%.

III. Key Parameter Comparison and Selection Tips

Parameter Comparison

  • Central Wavelength

- Flow Cytometry: 525nm (precisely matches fluorescent emission)

- Machine Vision: 525nm (covers green reflection spectrum)

  • FWHM

- Flow Cytometry: 30nm (narrowband for high specificity)

- Machine Vision: 50nm (broadband to balance sensitivity and coverage)

  • Transmittance

- Flow Cytometry: ≥90% (minimal signal loss)

- Machine Vision: ≥85% (balance between SNR and brightness)

  • Stopband OD

- Flow Cytometry: OD ≥4 (strong suppression of excitation light)

- Machine Vision: OD ≥3 (suppression of non-green light)

  • Filter Type

- Flow Cytometry: Interference-based (high-precision spectral control)

- Machine Vision: Interference-based or absorptive (cost optimization)

Selection Decision-Making

  1. Prioritize Spectral Matching: For applications involving fluorescent labeling (e.g., biological detection), choose narrowband interference filters. For color recognition (e.g., industrial detection), expand the bandwidth to 50nm for broader applicability.
  2. Balance Stopband and Transmittance: In high-sensitivity scenarios (e.g., weak fluorescent signals), require an OD ≥4 stopband. In strong-reflection scenarios (e.g., industrial illumination), moderately reduce stopband requirements to enhance overall brightness.
  3. Consider Environmental Factors: In outdoor or complex lighting environments, select filters with anti-reflective (AR) coatings to minimize stray light interference. For high-temperature or high-humidity environments, choose hard-coated filters (e.g., ion-assisted deposition technology) to ensure long-term stability.

By following these configurations, 525nm filters enable high-specificity signal extraction in fluorescence detection and enhance color recognition accuracy in machine vision, providing reliable spectral regulation solutions for cross-disciplinary applications.

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