650nm Bandpass Filter

650nm light is a specific wavelength in the red spectral region, characterized by high monochromaticity and good coherence, making it suitable for applications requiring precise wavelength control.

  • Application 1: In optical spectroscopy, a 650nm Bandpass Filter is used to isolate and transmit only the 650nm wavelength, enabling accurate measurement of samples that absorb or emit light at this specific frequency, such as in chemical analysis or material characterization.
  • Application 2: In laser alignment systems for industrial machinery, the filter blocks unwanted wavelengths, ensuring that only the 650nm laser light is used for precise positioning and alignment, enhancing the reliability and accuracy of the equipment.
  • Application 3: In biomedical applications like fluorescence microscopy, a 650nm Bandpass Filter helps to detect and filter specific fluorescent signals emitted by biomarkers labeled to emit at this wavelength, allowing for clear visualization and analysis of biological samples with minimal background noise.
650nm Bandpass Filter
Red Filter Illustration

How a 650nm Filter Works

This illustration demonstrates how a 650nm filter interacts with white light. White light is composed of all colors of the visible spectrum. The 650nm filter selectively transmits red light while absorbing or blocking other colors.

Light Source White Light (All Colors) 650nm Filter Other colors absorbed Transmitted Red Light

Explanation:

  • Light Source: Emits white light, which is a combination of all visible colors (represented by different colored rays).
  • 650nm Filter: This transparent material is designed to transmit light primarily in the red part of the spectrum (around 650nm wavelength).
  • Absorption: When the white light hits the 650nm filter, the filter absorbs most of the non-red wavelengths (like orange, yellow, green, blue).
  • Transmission: Only the red light passes through the filter, resulting in a red-colored light emerging on the other side.

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650nm Filter Selection Guide for Applications

This guide focuses on two core application scenarios: retinal ophthalmology diagnosis & treatment and optical beauty device phototherapy. It deduces filter configuration requirements from practical needs, analyzing selection logic and key technical specifications.

I. 650nm Filter Selection for Retinal Ophthalmology Applications

Scenario 1: Choroidal Imaging (Penetration Priority)

Key Technical Parameters
  • Type: Long-pass filter
  • Cut-off Wavelength: ≤620nm (at 50% transmittance)
  • Short-Wave Suppression: Transmittance in 500-600nm band < 1%
  • Substrate Material: Quartz glass (low absorption, high transmittance)
Selection Rationale & Application Value

The choroid lies deep beneath the retina, requiring the penetration advantage of 650nm red light (biological tissue penetration depth ~1-2mm).

  • Long-pass Characteristic: Only allows light ≥650nm to pass through, effectively filtering short-wavelength scatter (e.g., 400-500nm blue light) from the cornea/lens to reduce tissue interference.
  • Stringent Cut-off Requirement: <1% transmittance in 500-600nm band prevents chromatic noise from mid-wavelength light (e.g., 550nm green light) that could distort choroidal vascular imaging.Typical Application: In indocyanine green (ICG) angiography, this filter enables clear visualization of choroidal neovascular networks, assisting in diagnosing age-related macular degeneration.

Scenario 2: Retinal Photocoagulation (Precision Energy Control)

Key Technical Parameters
  • Type: Narrow-band pass filter
  • Central Wavelength: 650nm ±1nm
  • Full Width at Half Maximum (FWHM): 5-10nm
  • Peak Transmittance: ≥90%
  • Out-of-Band Suppression: ≥OD4 (transmittance < 0.01%)
Selection Rationale & Application Value

Retinal photocoagulation utilizes the thermal effect of 650nm laser to precisely ablate pathological tissues (e.g., abnormal vessels in diabetic retinopathy).

  • Ultra-Narrow Bandwidth: FWHM ≤10nm concentrates energy on the therapeutic wavelength, avoiding off-target damage to retinal nerve layers from adjacent wavelengths (e.g., 630nm red light).
  • High Transmittance + Deep Cut-off: ≥90% peak transmittance ensures sufficient treatment energy, while ≥OD4 suppression blocks stray light, reducing phototoxic risks to healthy retinal cells.Clinical Value: In retinal tear sealing, the narrow-band filter directs laser energy precisely to tear margins, promoting thermal coagulation of retinal pigment epithelium and accelerating tissue healing.

II. 650nm Filter Selection for Optical Beauty Device Applications

Scenario: Dermal Layer Phototherapy (Wavelength Matching & Energy Balance)

Key Technical Parameters
  • Type: Band-pass filter
  • Central Wavelength: 650nm ±2nm
  • Full Width at Half Maximum (FWHM): 20-30nm
  • Peak Transmittance: ≥85%
  • Edge Cut-off Steepness: Transmittance drops from 80% to <5% within 30nm
Selection Rationale & Application Value

650nm light penetrates to the mid-dermis (0.5-1mm), activating fibroblasts and promoting collagen synthesis.

  • Optimal Bandwidth Design: 20-30nm balances energy and specificity—narrower (<10nm) reduces energy output, while wider (>40nm) may include 600-620nm melanin-stimulating wavelengths that exacerbate pigmentation risks.
  • Steep Cut-off Characteristic: Rapid short-wavelength cut-off within 30nm avoids stimulating epidermal melanocytes with 580-600nm yellow light and blocks deep thermal damage from >700nm near-infrared light.Practical Application: In acne scar repair and stretch mark improvement, filtered 650nm light targets dermal collagen fibers, stimulating type I collagen regeneration while protecting epidermal barrier integrity.

Key Selection Criteria Summary

Core Selection Points (List Format)

1. Choroidal Imaging

  • Filter Type: Long-pass filter
  • Critical Parameters: Cut-off ≤620nm, 500-600nm transmittance <1%
  • Key Advantages: Deep penetration + stray light suppression
  • Typical Use: Ophthalmic angiography equipment

2. Retinal Photocoagulation

  • Filter Type: Narrow-band pass filter
  • Critical Parameters: Central 650nm ±1nm, FWHM 5-10nm
  • Key Advantages: Wavelength precision + high-energy efficiency
  • Typical Use: Laser ophthalmic treatment machines

3. Dermal Layer Phototherapy

  • Filter Type: Band-pass filter
  • Critical Parameters: Central 650nm ±2nm, FWHM 20-30nm
  • Key Advantages: Depth matching + safe energy window
  • Typical Use: Home/medical optical beauty devices

Core Selection Logic

1. Penetration Depth Dictates Spectral Range: Deep tissue imaging/treatment requires long-pass or narrow-band filters; shallow applications prioritize balanced band-pass filters.

2. Biological Effect Dictates Bandwidth Precision: Therapeutic scenarios (photocoagulation/phototherapy) need narrow bandwidths (≤30nm) for specificity; imaging applications allow broader cut-off ranges.

3. Safety Margins Precede Energy Parameters: All scenarios require clear out-of-band suppression (e.g., <1% or OD4) to avoid biological risks from unintended wavelengths.

By precisely matching optical properties and biosafety requirements of target applications, 650nm filters enable high-efficiency, low-risk light energy control in medical and aesthetic fields.

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