ERDI LASER
1535nm Eye-Safe Laser Source for Rangefinders, 10uJ to 10mJ
1535nm eye-safe laser sources for rangefinder modules: 10uJ to 10mJ pulse energy, 1 to 100Hz, compact OEM packages, datasheets and integration data.
What a laser rangefinder asks of its source
A rangefinder is a timing instrument: it measures how long a pulse takes to travel out and back. The laser decides three things that no downstream signal processing can recover — how much energy leaves the aperture, how often a measurement can be repeated, and how tightly that energy can be kept inside the receiver's field of view.
That is why the model is chosen from the requirement, not from a catalogue page. The ERDI range runs from a 14.5 × 6.3 × 4.37 mm micro package at 100 µJ to a 10 mJ transmitter, all at 1535 nm, all pulsed by the same Er:Yb glass microchip principle.
Models used in rangefinding work
Every figure below is the published minimum for that model. Pulse width is fixed by the microchip resonator, not adjustable in software.
| Model | Pulse energy | Repetition rate | Pulse width | Package (mm) | Weight | Supply / peak current |
|---|---|---|---|---|---|---|
| MINI-100 | ≥100 µJ | 1–10 Hz | 3.5 ns | 14.5×6.3×4.37 | 2.5 g | 2 V / 12 A |
| ER100 | ≥100 µJ | 1–10 Hz | 6 ns | 21×8×6.8 | 7 g | 2 V / 8 A |
| ER200 | ≥200 µJ | 1–10 Hz | 5 ns | 21×8×6.8 | 7 g | 2 V / 10 A |
| ER300 | ≥300 µJ | 1–10 Hz | 5 ns | 25×8×6.8 | 8.5 g | 2 V / 12 A |
| ER400 | ≥400 µJ | 1–10 Hz | 6 ns | 35×8×6.8 | 12 g | 2 V / 15 A |
| ER500 | ≥500 µJ | 1–10 Hz | 6 ns | 35×8×6.8 | 12 g | 2 V / 20 A |
| ER900 | ≥900 µJ | 1–5 Hz | 7 ns | 40×8×7.5 | 18 g | 2 V / 30 A |
Energy is set by the target, not by the distance alone
"Three kilometres" is not a specification. A retro-reflective road sign at three kilometres and a matte vehicle at the same distance are different problems, separated by more than an order of magnitude in returned energy. The five things that actually set the energy budget are:
- Target reflectivity and size — what fraction of the beam the target intercepts and how much of it comes back.
- Divergence the aperture allows — a wider beam spends energy illuminating background; a narrower one demands better pointing stability.
- Receiver aperture and sensitivity — a larger receive optic recovers energy that a wider transmit beam would have wasted.
- Atmospheric path — haze, fog and rain scatter the pulse before it returns.
- Required probability of detection — a single-shot design and a design that can average ten returns need different energies for the same range.
Selecting on energy and then checking the repetition rate is quicker than the reverse, because the rate only has to match how often the system measures, while energy has to close the link.
The electrical budget usually decides first
Microchip lasers are pumped by a diode and driven by a short, high-current pulse. The peak current in the table above is not a housekeeping figure: a 20 A rail cannot drive a 100 A transmitter, and this constraint rules models out earlier than the optics do. The compact family runs from a 2 V rail at 8–30 A; the millijoule transmitters need 5 V or 14 V at 80–100 A.
If the existing board provides 2 V and 15 A, the choice is already between ER100 and ER400 — the larger models are not a commercial question but a power-supply redesign.
Beam divergence and the aperture you already have
Divergence is published per model as a maximum, from ≤4 mrad on the millijoule units to <15 mrad on the high-repetition micro models. The window your optics allow sets the floor: a 10 mm aperture has a diffraction limit around 0.15 mrad before any aberration is added, so a design that assumes a tighter beam than its window allows will fall short on range regardless of the laser chosen.
Where the aperture is fixed by the product envelope — a monocular, a sight, a gimbal — send the aperture and the receiver with the enquiry. Beam expanders change the divergence but also the alignment budget, and it is cheaper to size the laser around the optic than to redesign the optic around the laser.
What is fixed and what can change
The pulse width is set by the resonator: 3.5–7 ns across the rangefinding models. It cannot be shortened or lengthened on request without changing the design, and it is not a tuning parameter in the driver. What can be adapted in an OEM programme is the package, the connector and the mechanical interface — see the custom and OEM programme for what is realistically variable.
Eye safety in the field
At 1535 nm the pulse is absorbed by the cornea and the lens before it reaches the retina, so the permissible exposure is orders of magnitude higher than at 905 nm. That is the reason a rangefinder can put a useful amount of energy into the air in a place where people are present. It does not remove the requirement to classify the finished product and to keep the beam path controlled; the physics is explained on the 1535 nm technology page.
Narrowing it down
Two questions reduce the range to one or two models:
- What energy do you need at the target, and against what kind of target?
- What supply voltage and peak current can the board provide?
Everything else — package, connector, temperature screening — is a variant question once those two are fixed. If the numbers are not settled yet, the five-item RFQ guide describes what to send so the first reply is a model rather than a question.
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