We are pleased to report recent developments in our project to develop an open source research grade linear CCD instrument. We have now achieved a new level in linearity at 0.2% INL over nearly the full range of the detector wells, with stable baseline and elimination of residual charge ghosting to baseline (dark noise). With this recent upgrade, we finally solve several problems that have been present in commercial instruments for a very long time and which are familiar to many of us.
We undertook the project because we could not find a commercial instrument that really performs at the level of professional instrumentation. Now there is one, and it is 100% open source. Please see our recently updated repository here: Linear CCD detector project.
Following are some highlights from the new and recent results that we present in the README. Please see the repository for more details.
| Metric | Validated Value | Characterization / Methodology |
|---|---|---|
| Integral Non-Linearity (INL) | < 0.2% | Measured to >99% of well capacity in phase-locked pulse loop mode, preserved across high gradient spectral transitions. |
| Quantization | 16-bit (65,536 ADU) | External differential 1MSPS ADC (MCP33131D) with low impedance FDA driving circuit. |
| Read Noise Floor (σ) | 52.2e-, temporal stability σ=6.8e- | Derived from photon transfer curve (PTC) analysis over an 810-frame dark ensemble with pairwise subtraction to isolate Fixed Pattern Noise (FPN). |
| Gain (K) | 0.812e-/ADU, uniformity σ=0.0755e-/ADU | Calculated via the inverse slope from the PTC method. |
| Timing Stability (Jitter) | < 10 ns | Hardware-locked synchronization using i.MX RT1062 FlexPWM and PIT modules. |
| Dynamic Range (Ensemble) | > 140,000:1 | 103 dB ratio of saturation limit to characterized noise floor; validated via PTC. |
| Dynamic Range (Single) | > 5000:1 | Instantaneous range sufficient for high-contrast absorption and fluorescence studies. |
- Integrated Nonlinearity (INL)
- Gain uniformity
- Ghosting (residual charge transfer) without mitigation:
- Residual charge transfer ghosting eliminated:
