Golf rangefinder teardown
Anatomy of a golf laser rangefinder
A golf rangefinder is the four subsystems the other ranging products carry - the emitter, the detector, the optics between them and the electronics that time the round trip - plus a fifth one they do not have: the tilt sensor and the display that turn a distance into a number the player can hit. Pick a part from the bill of materials and drop it on the unit; every parameter comes with the catalogue parts that carry it.
- 1Pick a part from the bill of materials.
- 2Drop it on the module, or just click the card.
- 3Read its job, its parameters and the part numbers behind them.
Bill of materials
Every part, one optical budget. Drag a card onto the photo, or click it - the panel beside it fills in with that part's parameters.
Drag a part here or click a card in the bill of materials
A handheld golf rangefinder, three-quarter view. The two apertures at the front left are the transmit and receive windows, the ocular is at the right, and the control ridge runs along the top.
Component positions are a teaching diagram, not an assembly drawing: the placement and the exploded view are indicative. Parameter values are those of the linked specification.
Every part, parameter by parameter
The same numbers the interactive view shows, in tables you can read, search and quote.
905 nm laser diode Transmitter
Emits the ranging pulse. On a golf unit peak power, pulse width and divergence are chosen for a few hundred metres and for thousands of measurements on one battery, so the compact end of the family is where the design starts - not the highest peak power on the list.
| Peak wavelength | 905 nm (895 - 915 nm) |
|---|---|
| Peak output power | 15 - 600 W |
| Pulse energy @ 100 ns | 1.5 - 30 uJ |
| Beam divergence, FWHM | 9 x 25 deg bare | 9 x 6 deg FAC |
| Pulse width | 1 - 100 ns (max 100 ns) |
| Duty cycle, max | 0.1 % |
| Repetition rate | up to 10 kHz |
| Package | TO56 | bare die | VCSEL array |
| Est. range, retro-reflective (40 W) | 755 m |
| Est. range, diffuse target (40 W) | 250 m |
Avalanche photodiode Receiver
Sets how weak a return the product can still trust. On a short-range unit the small-area packages are the right choice: less dark current and less capacitance than a large area, which is what keeps the timing edge sharp.
| Response spectrum | 400 - 1100 nm |
|---|---|
| Wavelength | 905 nm |
| Active area | 230 um TO-46 | 500 um LCC ceramic |
| Responsivity | 80 A/W @ M=100 |
| Response time | 0.5 ns |
| Dark current | 0.4 nA @ M=100 |
| Total capacitance | 1.0 pF @ M=100 |
| Optimum gain | 100 |
| Reverse breakdown voltage | 100 - 200 V |
| Optical filter | 905 nm spike filter |
| Package | TO-46 | LCC1 / LCC2 ceramic |
Emit / receive optics Optical path
Splits the light: the transmit aperture has to get the pulse out inside the receive aperture's field of view, and the receive aperture has to collect enough of the return without also collecting the transmitter's own glare.
| Optical channels | 2 ranging (transmit + receive) + observation path |
|---|---|
| Windows on the front face | 2 |
| Transmit beam, bare | 25 deg |
| Transmit beam, FAC | 6 deg |
| Receive aperture / focal length | Set by your optical design Set by your design |
| Transmission | To be confirmed against the drawing and a test band Set by your design |
| Receive filtering | 905 nm spike filter at the detector |
Drive and timing Electronics
Turns a stored capacitor into a nanosecond current pulse and turns the detector's edge back into a number. On a golf unit it also has to hold calibration across temperature, because the whole product is judged on repeatability.
| Peak pulse current | 70 A |
|---|---|
| Pulse width | 50 ns - 1 us adjustable |
| Repetition rate | 1 kHz - 30 kHz adjustable |
| Rise time | 7.5 ns typical |
| Fall time | 12 ns typical |
| Supply voltage | 12 V DC |
| Laser drive voltage | 1 - 50 V DC |
| Control interface | Internal trigger / external TTL |
| Factory default | 100 ns @ 3 kHz, internal trigger |
| Detector bias | 100 - 200 V reverse, temperature compensated Set by your design |
Tilt and display Interface
Adds the two things a plain rangefinder does not have - an angle, and a readable number. Which of the straight-line distance, the angle and a compensated distance the unit shows is a product decision, and a regulated one in some competitions.
| Tilt measurement range | To be confirmed: product specification Set by your design |
|---|---|
| Angle accuracy / resolution | To be confirmed: specification and calibration conditions Set by your design |
| Slope compensation | To be confirmed: whether this model supports it and how it is switched Set by your design |
| Display type / readout | To be confirmed: LCD, OLED or a projected reticle Set by your design |
| Buttons and modes | To be confirmed: product definition Set by your design |
| Indicator channel | Optional visible laser - see the parts below |
Every parameter value on this page is pulled from the catalogue record that renders the linked product page, so the two cannot disagree.
Parts behind these parameters
Every figure below is read from the same catalogue record that renders the product page. Nothing on this page is retyped.
Handheld 905 nm transmit chain
A flag is a cooperative target a few hundred metres away, so the design starts at the bottom of the power range and spends the budget on repetition rate and battery life instead.
What the emitter is built from
Two ways to build the transmit source for a sealed handheld: take the bare stacked die and package it yourself, or take a VCSEL array that is already low-profile and rugged.
Receive chain
Short range means a small active area is not a compromise - it is the better choice: less dark current, less capacitance, a sharper timing edge.
Drive and timing
One board with the pulse generator and the driver on it, at a repetition rate a golf unit can actually use.
Indicator and aiming optics
For a unit that adds a visible aiming dot or an illuminated indicator next to the invisible ranging path.
This unit is the 905 nm / pulsed / short-range scenario
Run the selector with application = rangefinder, wavelength = 905 nm and output = pulsed, then keep the peak power low: a flag is a cooperative target a few hundred metres away, so the transmit chain below is taken from the compact end of the family. The catalogue carries the same four subsystems up to 1.6 km and 2.1 km if the product has to grow, and an eye-safe 1535 nm chain if it has to.
Tell us the range, the target and the size limit
A golf rangefinder is the tightest package in the ranging family: one battery, a few hundred metres and a number on a screen. Send us the range you need and the space you have, and we come back with the transmit chain, the receiver and the optics between them.