DN125 Vacuum Sight Glass (DN-125 Vacuum Viewport)
DN 125 vacuum sight glass for compact high-vacuum systems. Available in borosilicate, fused silica & sapphire. Quick-fit DN/KF flange with optional AR coatings.
Description
The DN125 vacuum sight glass (DN-125 viewport) is an ultra-compact vacuum optical port designed for small chambers, sample holders and tight-space process equipment. It provides repeatable, reliable optical access for inspection, alignment, laser entry and basic spectroscopy without compromising vacuum integrity.
Constructed with a stainless-steel flange and a vacuum-grade window (borosilicate / fused silica / sapphire), the DN125 viewport is ideal where space is limited but visual or optical access is required.
Key Benefits
- Very compact footprint — fits into extremely small ports and cramped vacuum assemblies.
- Quick to install — compatible with standard small KF/DN clamping hardware for fast assembly and maintenance.
- Vacuum capable sealing — O-ring or metal sealed options provide low leak rates suitable for high-vacuum service.
- Multiple optical materials — choose borosilicate (visible), fused silica (UV), or sapphire (high temp / rugged) to match your application.
- Customisable — available with AR coatings, custom visible apertures, special flatness or marking on request.
Why choose the DN 125 viewport？
The DN125 viewport is the best choice when you need optical access but cannot accommodate larger ports. It’s commonly used for monitoring, alignment and laser coupling in compact vacuum systems. For applications requiring higher bakeout temperatures or UV/laser transmission, we recommend fused silica or sapphire variants — tell us your operating pressure, bakeout temperature and working wavelength and our engineers will recommend the optimal window material and seal.
By specifying your operating pressure, temperature, and optical wavelength, our engineering team can recommend the optim al window material and sealing configuration.
Typical Technical Specifications
| Product model | DN150 |
|---|---|
| Product vacuum degree | 1E*10-12 pa·m³/s |
| Flange material | 304/316 |
| Glass material | Borosilicate / Quartz (Fused Silica) / Sapphire / Barium Fluoride / Calcium Fluoride / Zinc Selenide |
| Surface quality | 60/40, 50/20, 20/10 |
| Optical surface type | 1/2 – 1/10 |
| Visible diameter (mm) | 130 |
| Heat resistance range | 150 ～ 230℃ |
| Surface treatment | Electrolytic polishing |
| Transmittance | 1.45 ～ 1.57 |
| Outer diameter (mm) | 250 |
| Inner diameter (mm) | 135 |
| Thickness(mm) | 22 |
| Number of through holes | 8 |
| Through hole specifications(mm) | M6 |
| Glass thickness | 10 |
Applications & industries
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Small vacuum chambers & load-locks (visual inspection & alignment)
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Research & lab vacuum setups (optical probes, spectroscopy)
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Semiconductor load locks and handling tools
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Laser coupling ports and alignment windows
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Analytical instruments and small vacuum process tools
