# STEMPix: A Phase-Transition-Material-Based Pixel Sensor for Resolving Edge-Movement Direction

arXiv: https://arxiv.org/abs/2609.04435 · HTML: https://mlsanity.com/paper/2609.04435/

## Key facts

- No citing papers in the map yet (data through 14 Oct 2026).
- Builds on 8 of its 47 references that are in the map.
- First posted on arXiv 3 Sep 2026.

## Builds on (most cited first, 8 of 8)

- [Learning to Detect Objects with a 1 Megapixel Event Camera](https://mlsanity.com/paper/2009.13436/) (2020)
- [Occlusions, Motion and Depth Boundaries with a Generic Network for Disparity, Optical Flow or Scene Flow Estimation](https://mlsanity.com/paper/1808.01838/) (2018)
- [P2M: A Processing-in-Pixel-in-Memory Paradigm for Resource-Constrained TinyML Applications](https://mlsanity.com/paper/2203.04737/) (2022)
- [A direct time-of-flight image sensor with in-pixel surface detection and dynamic vision](https://mlsanity.com/paper/2209.11772/) (2022)
- [A Review on Digital Pixel Sensors](https://mlsanity.com/paper/2402.04507/) (2024)
- [In-Pixel Foreground and Contrast Enhancement Circuits with Customizable Mapping](https://mlsanity.com/paper/2410.18052/) (2024)
- [Multi-Domain FeFET-Based Pixel for In-Sensor Multiply-and-Accumulate Operations](https://mlsanity.com/paper/2506.22596/) (2025)
- [Lightweight True In-Pixel Encryption with FeFET Enabled Pixel Design for Secure Imaging](https://mlsanity.com/paper/2604.05147/) (2026)

## Abstract (arXiv)

This paper proposes a spatio-temporal edge-movement direction pixel (STEMPix) for generating compact direction-aware edge movement information inside a CMOS-compatible image sensor array. The proposed design targets specialized sensing applications where local boundary movement is more important than full-frame intensity reconstruction. Instead of transferring full multi-bit frames for external processing, STEMPix generates a 3-bit local edge direction code (LEDC) by combining pixel-level temporal change information with neighboring-pixel spatial edge information. We design the architecture using a two-tier organization, where the photodiode layer is separated from the computation layer to preserve light-collection area while accommodating the additional in-array processing circuitry. The proposed circuit is evaluated through HSPICE transient simulations. The estimated implementation achieves a horizontal pitch of 1.73 μm, a vertical pitch of 2.36 μm, and a geometric fill factor of 95.47%. The average active switching energy is 0.465 fJ per LEDC operation across representative edge-movement cases. The proposed STEMPix operation also supports global-shutter capture and dynamic thresholding. These results indicate that STEMPix can provide a compact and scalable front-end representation for edge-movement-aware sensing systems.