Optical Observation

A night-vision monocular or a thermal clip-on has already spent most of its mass and volume budget before ranging is even discussed — on the image intensifier tube or the microbolometer array, the objective, and the sealed housing that keeps both alive outdoors. Adding distance means fitting a complete direct-time-of-flight system into what is left: emitter, receive optics, avalanche photodiode, timing electronics.

SPD1200N0 is built for that leftover volume. It is a Ø15.7 × 21.3 mm cylinder with a sealing groove, weighing about 5 grams, and it is not a cut-down part: it has a catalog range of 0.2–1,200 m and measures to ±0.3 m below 100 m and ±0.3 m + d·0.7‰ from 100 to 1,200 m. Supply is 3.3–5 V, average draw about 0.45 W with a maximum of 0.75 W, start-up ≤ 200 ms.

The integration argument that matters here is what the module does not ask of you. It does not sit in the imaging chain. It does not share a lens stack, a boresight adjustment or a coating specification with the intensifier tube or the bolometer. It mounts beside or behind the objective, roughly co-axial with the sight’s optical axis, and reports distance independently over its own UART-TTL line at 115200 bps. Your host MCU reads the frame and decides what to do with the number — render it on the display, or feed it into a reticle or ballistic calculation. The ranging module’s job ends at handing over a validated reading.

That independence is also mechanical freedom: the aperture needs an unobstructed, roughly co-axial view out of the front of the device, and beyond that the designer can put the module beside the objective, above it, or in the same housing wall as the battery compartment.

Field duty cycle is the other half. The lens cavity is IP67 — the cavity, not your finished enclosure — operating range is −20 to +60 °C with storage to −30/+70 °C, shock is rated 1000 g/ms at 10 events per second along the optical axis, vibration 5–50–5 Hz at 2.5 g, and reliability is stated as MTBF ≥ 1,500 h. Optics are PMMA with a Ø6.5 mm receiving aperture and < 4.5 mrad divergence, and the valid measurement rate is ≥ 98% with a false-alarm rate ≤ 1% under the reference conditions.

On the laser class: SPD1200N0’s field reads IEC Class 1, declared in the model manual rather than certified by a laboratory. For a device an operator points at people and animals in low light, that distinction belongs in your compliance file, not in a marketing line — and it is why we never write “eye-safe” about a 905 nm product.

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