A laser rangefinder module datasheet gives you one number that matters more than all the others: the maximum range. And that number is almost always measured under conditions your product will not have.
Here is what actually changes between the two wavelengths you will be quoted for most single-point ranging work — 905 nm and 1535 nm — and where the decision really gets made.
The detector decides the cost, not the laser
905 nm modules almost always pair with silicon avalanche photodiodes. Silicon is cheap, fast, and made in enormous volume, which is why the 905 nm family is the volume family: many variants, wide price spread, short lead times.
1535 nm modules need InGaAs detectors. The material is harder, the parts are fewer, and the module costs more per unit — typically several times the 905 nm equivalent for the same nominal range class.
That single fact explains most of the price difference people notice when they compare quotes. It is not marketing. It is materials.
Range at night is not range in daylight
A 905 nm module is quoted at its best case: dark target, good reflectivity, clean air, cooperative surface. Put the same module outdoors in daylight against a low-reflectivity target and the usable range drops — sometimes by half.
The three variables that actually decide your real number:
- Target reflectivity. A white wall and matte black rubber are not the same problem. Vendors who publish only one range figure are telling you the best case and nothing else.
- Ambient light. Sunlight in the receiver band raises the noise floor. This is where 1535 nm has a structural advantage: the solar background at that wavelength is far lower.
- Atmospheric transmission. Haze, dust, and rain scatter short wavelengths more. Long range outdoors in poor visibility favours 1535 nm.
If your application runs at night against cooperative targets, 905 nm will do the job at a fraction of the cost. If it runs in daylight, in dust, or against dark surfaces at distance, the cheaper module's effective range may not be cheaper at all.
Eye safety is not a marketing claim, it is a physics boundary
1535 nm sits in a band where the light is absorbed before it reaches the retina. That is why 1.5 µm systems can emit far more power at the same eye-safety classification, and it is the second structural reason they reach further: more permitted power means more returned signal.
905 nm light passes through the eye's optics and focuses on the retina. That constrains the permitted output power, which constrains range. Anyone selling you a very long range at 905 nm is either using a large aperture, a very cooperative target, or a number you should ask them to define.
This is also why the integration rules differ: a 905 nm module used near people needs a proper hazard assessment, and the aperture and beam geometry matter as much as the class label.
What this means for your BOM
| Your situation | Sensible starting point |
|---|---|
| Short range, indoor, cooperative targets, cost-sensitive | 905 nm, silicon detector |
| Long range outdoors, daylight, haze or dust | 1535 nm |
| Very high volume consumer product | 905 nm — the detector economics dominate |
| Long range but tight power budget and small aperture | 1535 nm, because permitted power per unit aperture is higher |
| Needing an eye-safe emitter near operators at distance | 1535 nm |
The reverse question is the one people forget: if you are being quoted 1535 nm for a 50 m indoor application, ask why. You are paying for physics you are not using.
The numbers you should demand from any supplier
Before comparing quotes across vendors, force every supplier onto the same worksheet:
- Maximum range at 10% reflectivity, not the best case.
- Maximum range at the reflectivity your actual target has.
- Ambient light condition during that measurement.
- Whether the number is a single-shot or an averaged result.
- Divergence and aperture, because range follows from them.
- Interface: UART, SPI, or a protocol with documented framing and checksums.
If a supplier cannot give you items 1 through 4, the range figure on their datasheet is a decoration.
Where to look at the actual variants
Our own catalogue publishes both families with per-model figures, including the measuring condition behind each range number, and every model has its own page with the interface and mechanical data:
- 905 nm family: https://erdilrf.com/905nm-laser-rangefinder-module/
- 1535 nm family: https://erdilrf.com/1535nm-laser-rangefinder-module/
- All 59 models with published unit prices: https://erdilrf.com/models/
- How we price them, and what volume actually changes: https://erdilrf.com/laser-rangefinder-module-wholesale/
If you tell us the target, the distance, and the conditions, we will name two models and the measurement condition behind each range figure — that is a cheaper conversation than a quote you cannot compare.
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