Why 1535 nm exists at all
At 905 nm the light lands on a silicon detector, which is cheap, fast and everywhere. The catch is the eye: 905 nm focuses on the retina, so the energy you are allowed to emit is limited by eye-safety rules, and that limit caps how far you can range with a small aperture.
At 1535 nm the light is absorbed by water in the front of the eye before it reaches the retina. The permitted pulse energy is far higher, so a 1535 nm module can put more light on a distant target through the same small aperture. That is the entire reason multi-kilometre compact rangefinders are built in this band — and why the 1535 nm line is the one that reaches 8, 12, 18 km in a package that still fits on a gimbal.
The costs follow directly: indium gallium arsenide detectors instead of silicon, erbium-doped laser sources instead of diode stacks, and a higher unit price. ERDI’s 1535 nm / 1.54 µm family starts at $300 and runs to $3,500 for the long-range modules.
The 1.54 µm module line, with published prices
| Model | Published range and condition | Price |
|---|---|---|
| LRF0105C | ≥ 3,000 m to a 2.3 × 2.3 m reference target; human-size target stated separately | $300 |
| LRF0305C | ≥ 4,000 m at 60% reflectivity; building target ≥ 3,000 m at 30% | $300 |
| LRF0306C | ≥ 4,000 m at 60% reflectivity; building target ≥ 3,000 m at 30% | $300 |
| LRF0310C | ≥ 3,000 m against a 2.3 × 2.3 m reference target | $300 |
| LRF0609C | ≥ 6,000 m; measured under visibility ≥ 12 km and ≤ 60% relative humidity | $800 |
| LRF0610C | ≥ 6,000 m to a 2.3 × 2.3 m reference target; human target stated separately | $800 |
| LRF0815C | ≥ 8,000 m to a 2.3 × 2.3 m target at 30% reflectance, visibility ≥ 10 km | $900 |
| LRF0818C | Vehicle (2.3 × 4.6 m) ≥ 8,000 m; human (0.5 × 1.7 m) ≥ 4,500 m | $900 |
| LRF1017C | ≥ 10,000 m against a 2.3 × 2.3 m reference target | $1,300 |
| LRF1221C | ≥ 12,000 m against a 4 × 6 m objective | $1,300 |
| LRF1525C | ≥ 15,000 m against a 4 × 6 m objective | $3,000 |
| LRF1830C | ≥ 18,000 m to a 3 × 3 m object, line of sight, visibility ≥ 26 km | $3,500 |
Read the conditions, not the numbers. An 18,000 m figure against a 3 × 3 m object at 26 km visibility describes a coastal or high-altitude sight line, not a city in haze. This is why every model page carries the exact condition next to the range — a range without its condition is marketing, and the whole published-catalog idea only works if the condition travels with the number.
The 1.54 µm laser source components
Separately from the rangefinder modules, the ER series is the 1.54 µm family of components and instruments, from ER100 at $70 (an erbium-glass laser source, per its catalog record) through ER200 $80, ER300 $100, ER400 $230, ER500 $250, ER800 $1,050, ER900 $1,100, ER2000 $1,500, ER4000 $2,000, ER8000 $3,000 to ER10000 at $5,000. A laser source is an emitter, not a complete rangefinder: if you are building your own receiver chain, this is the part you buy; if you are integrating a complete ranging engine, buy from the C series above.
1535 nm against 905 nm, decision by decision
| Question | 905 nm | 1535 nm / 1.54 µm |
|---|---|---|
| Entry price | From $80 | From $300 |
| Detector | Silicon — cheap, fast, ubiquitous | InGaAs — higher cost, lower noise at long range |
| Eye safety budget | Tight; limits energy per pulse | Far higher permitted energy |
| Range in a small aperture | Hundreds of metres to ~3 km | Kilometres to 18 km |
| Visibility of the beam | Faintly visible to a camera in the dark | Effectively covert to silicon cameras |
| Best fit | Altimetry, industrial sensing, handheld, AGV | Long standoff, gimbal payloads, gated viewing, range-finding at distance |
The engineering comparison in more depth is in 1535 nm vs 905 nm and 905 nm vs 1535 nm for UAV gimbals and payloads.
What to confirm before you design in a 1535 nm module
- The exact condition behind the published range. Target size, reflectivity and visibility. Two models in the same family are often specified against different targets.
- Minimum range. Some long-range modules have a minimum range measured in tens of metres; that is normal and it matters for anything approaching.
- Interface and frame. Request the protocol document, not just “UART”. Drivers and protocol documents are published.
- Packaging. Aperture, mounting, supply and thermal path all change with the model, and the thermal path is not optional at high pulse energy.
Next step
Tell us the target, the distance and the platform, and we will point at the two 1535 nm models that fit — tommy@erdimail.com, or the selection form.
Where two source documents for a model conflict, the model page states the conflict rather than choosing one value, and the current datasheet governs the order.