Notes on the hardware including 1550nm response

README.md

@@ -1,4 +1,4 @@
-# Point Grey / FLIR SWIR camera on Ubuntu 24.04 / Linux Mint 22
+# Point Grey / FLIR USB2 camera on Ubuntu 24.04 / Linux Mint 22
 
 Setup for a legacy **Point Grey Research USB 2.0 camera** (USB vendor `1e10`) on a modern Debian/Ubuntu-family machine. Tested against the camera that reports:
 
@@ -10,6 +10,27 @@ Manufacturer: Point Grey Research
 
 These cameras predate FLIR's Spinnaker SDK and are supported only by the older **FlyCapture2 SDK** (here, version 2.13.3.31). Spinnaker will not see them.
 
+## What this camera actually is
+
+The reference unit was handed over as a "SWIR camera," but it is a standard visible/near-IR machine-vision camera with a wavelength converter fitted in front of the sensor. Worth knowing before you trust it for anything quantitative.
+
+`FlyCapture2Test` reports:
+
+```
+Camera model - Chameleon CMLN-13S2M
+Sensor       - Sony ICX445AL (1/3" 1296x964 CCD)
+```
+
+That is a plain silicon CCD, which physically cannot detect 1550 nm on its own (silicon's band edge sits near 1050 nm). It images 1550 nm because someone fitted an **anti-Stokes upconversion phosphor** over the sensor together with a visible-blocking filter. The phosphor absorbs roughly 1495–1595 nm and re-emits around 532 nm green, which the silicon CCD detects normally. The modification is entirely optical, so the camera still identifies itself as a stock Chameleon and there is nothing to configure for it in software.
+
+In practice:
+
+- **Band-limited to about 1495–1595 nm.** It will not see 1310 nm, 1064 nm or 2 µm. It responds to incandescent bulbs (blackbody emission reaches into that band) but not to visible LEDs.
+- **Direct sources only.** It needs roughly 1–2 mW imaged onto the array (a laser spot, or a hot filament). It cannot image reflected or diffuse SWIR scenes.
+- **Resolution is phosphor-limited.** The phosphor point-spread is around 70 µm, so 1550 nm images are much softer than the 1296×964 sensor implies, and dynamic range is only about 30 dB.
+
+It is a cheap 1550 nm beam/source viewer, not a SWIR scene camera. Genuine quantitative or reflected-scene SWIR imaging needs an InGaAs sensor. The FlyCapture2 setup below is the same either way, since the camera electronics are unmodified.
+
 ## What gets installed
 
 The FlyCapture2 SDK was built for Ubuntu 18.04. Its GUI applications (`FlyCap2`, `UpdatorGUI`) depend on GTK2-era libraries (`libgtkmm-2.4`, `libglademm-2.4`, `libgtkglextmm`) that no longer exist in Ubuntu 24.04, so we do not install them. The **core** libraries only need `libusb` and `libraw1394`, which are still present, so this setup installs:
@@ -34,7 +55,7 @@ The vendor GUI itself is the only thing lost by not being on 18.04, and `fc2view
 fc2view
 ```
 
-It connects to the first camera, prints its model and serial, and opens a live window. Keys: **`s`** saves a snapshot to the current directory as `fc2-<serial>-<timestamp>.png` (saved from the raw frame, so a Mono16 SWIR sensor keeps its full bit depth); **`q`** or **Esc** quits. It converts each frame to BGR for display, so it works on mono/SWIR and colour sensors alike.
+It connects to the first camera, prints its model and serial, and opens a live window. Keys: **`s`** saves a snapshot to the current directory as `fc2-<serial>-<timestamp>.png` (saved from the raw frame, so a 16-bit sensor keeps its full bit depth); **`q`** or **Esc** quits. It converts each frame to BGR for display, so it works on mono and colour sensors alike.
 
 It's about 130 lines and depends only on OpenCV and the FlyCapture2 core library. Treat it as a starting point for your own acquisition code. Rebuild by hand with: