Using the bench
Measurement & detectors
This is the panel that makes Photonica an instrument rather than a picture. Every row is a real measurement of the bench as it stands.
Focus
| Row | Means |
|---|---|
| Beam angle | How far the main beam has been deviated from the direction it started in |
| Focal distance | Distance from the last lens to best focus for the whole spectrum |
| Red / green / blue focus | The same, at 640, 532 and 450 nm. The grey number beside it is the paraxial prediction |
| Best-focus spot | RMS radius of the smallest spot the system can form, in mm |
| RGB separation | A visual bar showing how far apart the three colours focus |
| Blue − red focus | Longitudinal chromatic aberration, in mm. Negative means blue focuses closer |
A focus marked virtual is behind the optics — a diverging system, where the light only appears to come from that point.
On the screen
| Row | Means |
|---|---|
| Screen distance | From the last lens to the screen face |
| Green spot | RMS spot radius at 532 nm where the light lands |
| Spot (all colours) | The same including every wavelength — bigger, because colour spreads it |
| R−B lateral | Sideways colour separation on the screen (lateral chromatic aberration) |
Detector
Below that, the screen is treated as a real photodetector. These numbers come from a Monte-Carlo run of 200,000 photons following every reflection branch, so they include ghosts, splitter arms and losses.
| Row | Means |
|---|---|
| Power | Milliwatts actually landing on the screen |
| Peak irradiance | W/cm² at the brightest point |
| FWHM u × v | Width of the spot at half its peak, in two directions |
| Spot RMS | Root-mean-square radius of the energy distribution |
| Centroid | Where the middle of the light actually is on the screen |
| Spectral peak | The strongest wavelength arriving, or "broadband" |
| Pulse arrival | Mean time of flight in picoseconds, with the earliest arrival and the spread |
| Blue − red delay | How much later one colour arrives than the other, from dispersion |
| Polarisation | Degree of polarisation and the Stokes vector |
All light paths
The Monte-Carlo section breaks the arriving light down by how many bounces it took — direct, one bounce, two, three or more. It is the honest accounting of where the light in your system actually goes.
For gems there is a second readout: light return within 30° of the source direction, which is the "face-up brightness" gem graders measure, plus how much escapes out the back.
Autofocus and export
- AUTO FOCUS: screen (or F) slides the measured screen to best focus.
- AUTO FOCUS: lens moves the selected lens instead, to make the smallest spot on a fixed screen.
- Copy raw data (Ctrl + Shift + C) puts the entire report on your clipboard as JSON — every property, measurement and traced ray path. Paste it into a notebook or hand it to an assistant.