Electron-bombarded active pixel sensors (EBAPS, also termed EB-CMOS or EBCMOS) combine the quantum sensitivity and selectable spectral response of a vacuum photocathode with the spatial sampling, frame rate and digital output of a CMOS imager. Photoelectrons are accelerated through a proximity-focused vacuum gap and strike an electron-sensitive CMOS anode directly. This removes the microchannel plate (MCP), phosphor screen and fibre-optic relay used in conventional intensified cameras, shortening the conversion chain and reducing size, weight, power, persistence and coupling losses. For the Center, this direct vacuum-to-digital architecture is among the most promising routes to compact digital night vision and multispectral low-light modules.
At acceleration potentials of roughly 1–3 kV, each incident photoelectron deposits sufficient energy in silicon to generate hundreds of electron–hole pairs. When this electron-bombarded semiconductor gain exceeds CMOS read noise, the input-referred noise can fall below one photoelectron and individual photon events become detectable. Research is now moving beyond sensitivity demonstrations toward high-resolution anodes, controlled multiplication noise, high dynamic range and longer lifetime. Recent work includes fully frontside-thinned EBAPS structures that reduce backscatter and electrical crosstalk, real-time suppression of mixed and scintillation noise, and Monte Carlo models linking passivation, doping, multiplication-layer thickness and incident energy to gain and signal-to-noise ratio. ISIE19-class development also demonstrates the value of high-frame-rate, HDR CMOS anodes for operation from high-starlight toward overcast-starlight conditions. [1–4]
Our hybrid-sensor programme treats EBAPS as a coupled vacuum–photocathode–semiconductor–processing system rather than a stand-alone detector. We investigate photocathode-to-CMOS proximity focusing, electron-bombarded gain and spatial uniformity, entrance-layer and backscatter losses, anode degradation under cumulative dose, high-voltage gating and synchronisation of high-frame-rate readout with local tone mapping, image fusion and edge AI. Because the same vacuum-photocathode physics underpins our intensifier research, analogue tubes, intensified CMOS cameras and EB-CMOS devices can be tested on common low-light benches. This produces directly comparable sensitivity, noise, MTF, dynamic-range, latency and power data for European sensor integrators.
Key challenges include radiation hardness of the electron-sensitive anode surface, stable miniature high-voltage and vacuum packaging, dynamic-range management under bright-source exposure and gated operation and limited European supply-chain depth for specialised back-thinned CMOS. Band-specific photocathodes can extend the concept beyond passive visible/NIR imaging toward UV-C and gated ~1.06 µm applications, but each spectral variant requires its own optimisation of quantum efficiency, dark emission, packaging and illumination. Our outlook is that deployable EBAPS modules will be defined not by maximum gain alone, but by co-optimised photocathodes, durable anode surfaces, HDR pixels, calibration and low-latency processing. The Center is aligning its validation roadmap with European sensors and CMOS partners to mature these modules toward prototypes for dismounted soldiers, vehicles and unmanned platforms. [3–5]
REFERENCES
[1] Chen, W., Chen, Y., Li, Y., Jiao, G., & Song, D. (2024). A universal gain theory of the multiplying layer in EBCMOS based on elastic and inelastic scattering. Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 551, 165352. https://doi.org/10.1016/j.nimb.2024.165352
[2] Zhang, J., Qian, Y., Zhang, Y., & Liu, J. (2025). High-resolution low-light electron-bombarded active pixel sensor with a fully frontside-thinned structure and its noise characteristics. IEEE Transactions on Electron Devices. https://doi.org/10.1109/TED.2025.3570662
[3] Wang, Y., Qian, Y., Lin, J., & Chen, Y. (2025). Real-time noise suppression algorithm for electron bombarded active pixel sensor via adaptive spatiotemporal side window filter. Proceedings of SPIE, 13511. https://doi.org/10.1117/12.3057137
[4] Jiao, G., Liang, R., Liu, Y., Wang, C., Yan, L., Chen, W., & Li, Y. (2026). Characteristics and influencing factors of multiplication noise in EBCMOS. Photonics, 13(6), 511. https://doi.org/10.3390/photonics13060511
[5] Liang, R., et al. (2026). The degradation mechanism of charge collection efficiency in electron multiplication layer of EBAPS. Proceedings of SPIE, 14177, 141773C. https://doi.org/10.1117/12.3108057