CERN Accelerating science

European Organization for Nuclear Research




The Medipix2 ASIC is a high spatial, high contrast resolving CMOS pixel read-out chip working in single photon counting mode. It can be combined with different semiconductor sensors which convert the X-rays directly into detectable electric signals. This represents a new solution for various X-ray and gamma-ray imaging applications.
The core concept of the Medipix2 chip was originally invented for pattern recognition in tracing of particles in the LHC. Since then the technological platform has evolved and is being developed in different application specific directions.

Area of expertise



  • Life Sciences
  • Digital Autoradiography
  • Astrophysics
  • Various X-ray and gamma-ray imaging applications
  • Neutron imaging
  • Diffraction analysis

Innovative features

  • The chip is designed to accept either positive or negative charge input
  • A window of energy can be selected through the pixelwise adjustment of upper and lower threshold
  • Pixel size reduced to 55 microns


  • Pixel size: 55 micro meter
  • Chip size: 256x256 pixels
  • Active area: 1.4x1.4 cm
  • Counting rate: 1Mhz
  • Energy range: from 3keV upwards
  • Imaging rate: 20 frames per second


  • Count of photons within a given energy region
  • High maximum count rates, allowing for high intensity illumination up to the order of 0.4 GHz/mm²
  • High sensitivity, large dynamic range and low contrast detectability, exceeding present charge integrating techniques; dose reduction is a consequence of these features
  • Noise-free
  • No sensitivity to dark currents, allowing for long exposure times under very low intensity illumination
  • High speed imaging and readout - 20 frames per second


The chip is limited to 256x256 pixels (1.4x1.4 cm). However, the chip is 3-side buttable so an array of 2*n chips is feasible. For instance, a detector comprising four Medipix2 chips gives an active area of 2.8x2.8 cm.

Intellectual Property status

This technology developed by the Medipix Collaboration, comes with side-technologies like read-out electronics, dedicated chip-boards, data acquisition systems, software... The technology is ready for licensing with or without the side-technologies. Partnerships for further application specific developments are also possible.

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