Longpass Filters — High Transmission & Precise Cut-on Wavelengths
At Bote Optics, we manufacture high-performance longpass filters that are engineered to transmit wavelengths longer than a specific cutoff point. Ideal for use in fluorescence imaging, machine vision, laser protection, and UV/IR detection, our filters offer sharp cut-on edges, high transmission, and excellent blocking in the stopband.
With production capabilities in Nanjing, China and local assembly/testing in Singapore, we provide global customers with custom longpass optical filters in a range of materials and coatings—delivered fast, with exceptional quality control.
📘 What Is a Longpass Filter?
A longpass filter is an optical filter that allows light with wavelengths longer than a specific cutoff wavelength to pass through, while blocking shorter wavelengths. The cutoff point is typically defined at 50% transmission, and the slope determines how sharp the transition is.
Longpass filters are used across industries, including:
- Biomedical fluorescence imaging
- UV photography and IR observation
- Spectroscopy
- Laser safety and beam shaping
- Optical instrumentation
🧪 Bote’s Longpass Filter Selection
| Product Type | Cut-on Wavelength (nm) | Material | Applications |
|---|---|---|---|
| UV Longpass Filter 320nm | 320+ | UV Fused Silica | UV photography, fluorescence imaging |
| Longpass Filter 400nm | 400+ | Optical Glass | Blocking UV for general applications |
| Longpass Filter 495nm | 495+ | BK7 / Quartz | Green fluorescence imaging |
| IR Longpass Filter 850nm | 850+ | Germanium / Silicon | NIR imaging, IR sensors |
| Custom Longpass Filter | Any cut-on 200–5000nm | Glass, IR crystals | OEM, research, spectroscopy |
We offer hard-coated filters, glass absorption filters, and thin-film coated substrates, depending on your transmission and durability needs.
🔍 Longpass vs Bandpass Filter — What’s the Difference?
| Feature | Longpass Filter | Bandpass Filter |
|---|---|---|
| Passband | All wavelengths longer than cutoff | A defined narrow wavelength range |
| Blocking Range | Shorter wavelengths | Outside the selected narrow band |
| Common Use | Blocking UV, isolating NIR/IR light | Fluorescence, spectroscopy, color filtering |
| Example | 400nm longpass (passes >400nm) | 550±10nm bandpass |
Longpass filters are simpler and often used for general spectral isolation, while bandpass filters are more selective and suited for applications needing narrow wavelength control.
☀️ UV Longpass Filters for Imaging & Detection
UV longpass filters are specialized to block deep UV light while transmitting longer wavelengths such as visible or near-IR. They’re frequently used in:
- UV fluorescence photography
- UV light blocking in vision systems
- Skin imaging & biological stain enhancement
Bote’s UV longpass filters are made from UV-grade fused silica or quartz, ensuring high transmission in the near-UV to visible range and exceptional durability under intense light exposure.
🎯 Precision Coating & Substrate Options
We offer a wide range of substrates and coatings to match your optical requirements:
Substrate Materials:
- BK7 / Borosilicate Glass: For visible applications
- Fused Silica / Quartz: For UV and laser use
- Germanium / Silicon: For IR filtering
- Colored Glass: Absorptive longpass options
Coating Types:
- Hard Dielectric Coatings: High damage threshold
- Metallic Coatings: Broad range but lower transmission
- Hybrid Coatings: Enhanced slope with durability
Learn more about our custom coatings →
📸 Example Use Case: Longpass Filter in Fluorescence Microscopy
A 495nm longpass filter is often used to isolate green or red fluorescence emission in biological samples after excitation by a 488nm laser. It blocks residual excitation light and passes emitted signal for clear imaging.
(Insert image: microscope fluorescence imaging with a diagram showing blocked & passed wavelengths.)
💬 FAQ – Frequently Asked Questions
Q1: What is the difference between a UV longpass filter and a UV bandpass filter?
A: A UV longpass filter blocks deep UV and transmits longer wavelengths, while a UV bandpass filter allows only a narrow UV range to pass and blocks both shorter and longer wavelengths.
Q2: Can I use longpass filters for IR photography?
A: Yes. For example, an 850nm longpass filter blocks visible light and transmits IR, making it ideal for near-infrared imaging with modified cameras.
Q3: What defines the “cut-on wavelength”?
A: It’s the wavelength where transmission reaches 50%. Steep-edge coatings ensure a sharp transition from blocking to passing regions.
Q4: Can Bote customize longpass filters for OEM projects?
A: Absolutely. We support custom sizes, shapes, coatings, and even private labeling for industrial or academic OEM clients.
🌐 Why Choose Bote Longpass Filters?
✅ Custom Fabrication Available
✅ High Optical Density in Blocking Range
✅ Stable Hard-Coated Performance
✅ Rapid Prototyping & Scalable Volume Production
✅ Precision Metrology with ISO QC Standards
From prototyping to volume production, Bote ensures precision and consistency across all longpass filter batches.
📦 Ordering & Customization
We stock standard options and offer fast delivery for ASEAN, EU, and North American customers. Typical lead times:
| Quantity | Lead Time |
|---|---|
| Standard models | 3–7 days |
| Custom sizes/coating | 2–3 weeks |
| OEM Volume Orders | Negotiable |
📨 Contact us via bote.com.sg/contact or
📧 Email: [email protected]