THORLABS FELH1500 Longpass Camera Filter 25MM 1500NM

( Brand: Thorlabs ), ( Manufacturer Part Number: FELH1500 ), ( Part Type: Circular Camera Filter ), ( Filter Shape: Circular ), ( Filter Color: Orange ), ( Filter Effects: Longpass ), ( To Fit: Camera ), ( Filter Size: 25 Mm )

Review THORLABS 25mm Circular 1500nm Longpass Camera Filter Lot Of

The **Thorlabs FELH1500-25 1500 nm Longpass Filter** is a precision-engineered optical component designed for high-performance applications requiring strict spectral separation in the near-infrared and visible light spectrums. Crafted from high-quality optical glass, this filter employs a proprietary multilayer dielectric coating to deliver exceptional transmission characteristics beyond 1500 nm while effectively blocking wavelengths below this threshold. With a central wavelength cutoff at 1500 nm, the filter ensures minimal absorption and scattering, maintaining optical clarity and minimizing signal degradation in sensitive imaging, spectroscopy, or laser-based systems. Its 25 mm diameter provides ample clear aperture, making it ideal for use with standard camera sensors, microscopes, or other optical setups where space and compatibility are critical. The filter s robust construction ensures durability under varying environmental conditions, while its precise optical performance guarantees consistent results across a wide range of applications, from biomedical imaging and fluorescence microscopy to laser diagnostics and optical communications. Whether integrated into a scientific instrument or a custom optical assembly, the FELH1500-25 filter offers a reliable solution for isolating infrared light while rejecting unwanted visible and near-infrared interference, enhancing the accuracy and efficiency of optical measurements.

The Thorlabs FELH1500-25 1500 nm longpass filter is a specialized optical component used to block wavelengths shorter than 1500 nm while allowing longer wavelengths to pass through. Below is a detailed breakdown of its pros and cons, followed by a conclusion and recommendation.

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### **Pros of the Thorlabs FELH1500-25 1500 nm Longpass Filter**

1. **High Optical Quality and Precision**

Thorlabs is a well-established manufacturer known for producing high-precision optical components. This filter is designed with tight tolerances, ensuring consistent performance across the specified wavelength range. The coating is optimized for minimal reflection and absorption losses, which is critical for applications requiring high transmission efficiency.

2. **Broadband Transmission**

The filter allows wavelengths longer than 1500 nm to pass through with minimal attenuation, making it suitable for applications in the near-infrared (NIR) and infrared (IR) regions. This is particularly useful in spectroscopy, imaging, and laser-based systems where longer wavelengths are the primary focus.

3. **Durable and Stable Coating**

Thorlabs uses robust coating technologies that are resistant to environmental factors such as humidity and temperature fluctuations. This ensures long-term stability and reliability, reducing the risk of degradation over time.

4. **Compatibility with Common Optical Systems**

The 25 mm diameter is a standard size that fits many optical mounts, filter wheels, and imaging systems. This makes it easy to integrate into existing setups without requiring custom modifications.

5. **Low Reflection and Scatter**

The anti-reflection coating on the uncoated side minimizes back reflections and stray light, which is beneficial for reducing noise in imaging and detection systems.

6. **Well-Specified Cutoff Wavelength**

The cutoff at 1500 nm is sharply defined, providing a clear demarcation between blocked and transmitted wavelengths. This precision is essential for applications where exact spectral separation is required.

7. **Thoroughly Tested and Calibrated**

Thorlabs subjects its filters to rigorous testing to ensure they meet or exceed specified performance metrics. This reduces the risk of unexpected failures or inconsistencies in the field.

8. **Good Thermal Stability**

The filter maintains its optical properties across a range of operating temperatures, which is important for applications in varying environmental conditions or those involving heating elements.

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### **Cons of the Thorlabs FELH1500-25 1500 nm Longpass Filter**

1. **Limited Useful Wavelength Range**

While the filter excels at blocking wavelengths below 1500 nm, it may not be ideal for applications requiring transmission in the visible or shorter NIR ranges. If your application involves wavelengths significantly shorter than 1500 nm, this filter will not be effective.

2. **Potential Cost**

Thorlabs filters are generally more expensive than generic or lower-quality alternatives. For applications where cost is a critical factor, this could be a significant drawback, especially if bulk purchases are not feasible.

3. **Size Constraints**

The 25 mm diameter may be too large for compact or space-constrained systems. If your setup requires a smaller filter, you may need to source a different size or design, which could complicate integration.

4. **Potential Polarization Effects**

Some longpass filters can introduce polarization-dependent effects, though Thorlabs coatings are typically designed to minimize this. If your application is highly sensitive to polarization, you may need to test the filter s performance in your specific setup.

5. **Limited Customization**

Thorlabs offers a range of standard filters, but customization options (e.g., different diameters, edge wavelengths, or coatings) may require additional lead time or higher costs. If your application has unique requirements, you may need to explore non-standard solutions.

6. **Potential for Damage from Improper Handling**

Like all optical components, this filter can be damaged by scratches, dust, or improper cleaning. Thorlabs provides guidelines for handling, but mishandling could reduce the filter s lifespan or performance.

7. **Dependence on Thorlabs Support**

If you encounter issues with the filter, you will need to rely on Thorlabs customer support for replacements or troubleshooting. This could introduce delays if the company s response time is slow.

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### **Conclusion**

The Thorlabs FELH1500-25 1500 nm longpass filter is a high-quality, reliable component ideal for applications requiring precise spectral separation in the near-infrared region. Its strengths lie in its optical precision, durability, and compatibility with standard optical systems. However, its cost, size limitations, and lack of customization may make it less suitable for budget-conscious or highly specialized applications.

If your primary goal is to block wavelengths below 1500 nm while maximizing transmission above this threshold in a stable and high-performance system, this filter is an excellent choice. Conversely, if you are working with shorter wavelengths, need a more compact solution, or have strict budget constraints, you may need to consider alternatives.

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### **Recommendation**

- Your application involves wavelengths primarily above 1500 nm (e.g., NIR spectroscopy, IR imaging, or laser-based systems).

- You require a high-quality, durable filter with minimal reflection and scatter.

- You are working within a system that can accommodate the 25 mm diameter.

- Budget is not a limiting factor, and you value Thorlabs reputation for precision and support.

- You need to work with wavelengths significantly shorter than 1500 nm (e.g., visible or shorter NIR applications).

- Your system has space constraints that make the 25 mm size impractical.

- Cost is a critical factor, and you are open to exploring lower-cost manufacturers or generic filters (though this may compromise performance).

- You require customization options not offered by Thorlabs.

For most professional or research-grade applications in the NIR range, the Thorlabs filter is a strong recommendation due to its reliability and performance. Always verify the filter s specifications against your exact requirements to ensure compatibility.

Details:

Applications: Commonly used in Rama spectroscopy, fluorescence microscopy, and for isolating specific spectral regions experimental setups. Cut-On Wave length : 1500 nm at 90% transmission. Directional Engraving: To minimize unwanted scattering and reflections, the filter edge typically has an engraved arrow indicating recommended direction of transmission. Thorlabs FELH15 a high-performance 25.0mm hard-coated longpass filter designed to selectively transmit light with wave lengths longer than its specified cut-on value.

Rejection/Blocking Region: 200 nm 1482 Optical Density > 5. Key Features, Hard-Coated Sputtered: Provides excellent durability and higher damage thresholds compared to traditional soft-coated filters. Core Specifications, This filter is part of Thorlabs' sputtered edge pass series, offering high transmission and steep rejection transitions. Transmission Region: 1518 nm 2150 Absolute transmittance > 90%.

Substrate: UV Fused Silica.

part #: felh1500 prices

• $16.22-$69.99

specifications filtecam:

• brand: Thorlabs
• mpn: Felh1500
• part type: Circular Camera Filter
• filter shape: Circular
• filter color: Orange
• filter effects: Longpass
• to fit: Camera
• filter size: 25 Mm

returns filtecam:

• policy: No Returns

seller filtecam:

• city: Burnsville, Minnesota
• rating: 100.0%
• # reviews: 208

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• class: Standard
• cost: $5.39

general filtecam:

• condition: New
• Cameras Photo > Lenses Filters > Filters

offer filtecam:

• sold: 0
• options: Ship-to-home
• best offers: True
• started: April 7, 2026
• availability: In Stock
• quantity: 1

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