A narrowband optical filter improves LiDAR signal-to-noise ratio primarily by reducing the amount of broadband ambient light that reaches the receiver detector while preserving the wavelength of the returned laser pulse. The principle is straightforward, but the engineering trade-off is not: making the passband narrower…
An ambient light rejection filter for a time-of-flight sensor is a narrow bandpass interference filter placed in the receive path that transmits the illuminator wavelength, normally 850 nm or 940 nm, and blocks everything else across the detector’s spectral response. It matters because time-of-flight (ToF)…
Choosing between 905 nm vs 1550 nm LiDAR optical filters is not simply a matter of moving the center wavelength of the same bandpass filter. The two wavelengths are associated with different laser sources, detector materials, eye-safety constraints, ambient-light conditions and receiver architectures. Those differences…
1550 nm Narrow Bandpass Filter for LiDAR: How to Specify the Receiver Filter A 1550 nm narrow bandpass filter for LiDAR (Light Detection and Ranging) sits directly in front of the InGaAs (indium gallium arsenide) detector, and it has exactly one job: discard solar photons…
Telecentric F-Theta Lens vs Standard F-Theta Lens: Engineering Differences and Selection A telecentric F-theta lens vs standard F-theta lens comparison is mainly a question of beam geometry at the workpiece. Both lens types can be designed for a substantially flat scanning field and approximately linear…
F-theta distortion and field curvature are both field-dependent errors in a laser scan lens, but they fail in completely different ways. F-theta distortion is a position error: the focused spot lands somewhere other than where the scan angle says it should, while staying sharp. Field…
The relationship behind F theta lens focal length vs scan field is straightforward at first order: for an ideal F-theta mapping, the displacement of the focused spot is approximately proportional to effective focal length and optical scan angle. A longer focal length therefore produces a…
Choose zinc selenide (ZnSe) when the optic sits in a CO2 laser beam or has to transmit past about 14 µm. Choose zinc sulfide (ZnS) when the optic faces weather, sand, or rain, or when visible light and thermal infrared have to share one aperture.…
To specify the OD blocking range for a bandpass filter you need two independent numbers, not one: the depth of rejection, given as optical density (OD), and the wavelength interval over which that rejection is guaranteed. The interval is set by your system rather than…
Engineers usually reach the question of how to calculate F-theta scan field size at one of two moments: when a marking field has to cover a part of known dimensions, or when a calculated field does not agree with the number printed on a lens…
Thermal lensing in germanium optics is the change in optical power that occurs when absorbed radiation heats a germanium element non-uniformly, creating a radial temperature gradient that is converted into a refractive index gradient through the material’s thermo-optic coefficient. The heated element behaves as if…
Choose a Raman edge filter when you only need Stokes signal and you want to measure as close to the laser line as physically possible. Choose a notch filter when you need Stokes and anti-Stokes in the same acquisition, or when your excitation wavelength moves…
