Image intensifiers: How to make the right choice?

The image intensifier is a key component of each ICCD camera. This section deals with the fundamental characteristics of image intensifiers and their options.

Structure and applied voltages of image intensifiers.

The structure of image intensifiers in a schematic drawing. The main components of image intensifiers are photocathode, multi-channel-plate and phosphor screen.

Characteristics of image intensifiers are adjusted to experimental conditions

Different applications of ICCD cameras and intensified imaging solutions have special demands and requirements to the camera and thus on the image intensifier. This guidance deals with some fundamental characteristics of image intensifiers. The way the image intensifiers will perform does strongly depend on the scenery observed. Therefore, the following questions need to be addressed:

  • How fast need to be the shutter/shortest gating time?
     0.2ns (4 Picos) or 1.2ns (4 Quik E)
  • What are the spectral characteristics of illumination?
    Does determine the suitable photocathode.
  • How much light is there?
    Dual stage multi-channel-plates have better performance at low light environments.
  • High speed or low light imaging?
    Does determine the suitable phosphor screen.

Shutter speed

The shutter speed is limited by the electrical supply of and the electrical properties and connection to the photocathode. Stanford Computer Optics is the only manufacturer that uses coax cables for the photo cathode voltage supply. This enables gate times less than 3ns which are not possible with standard single wire cabling.
However, the shutter speed is mostly limited by the size of the photocathode as the propagation of any electromagnetic signal is limited by the speed of light. Therefore, the electromagnetic signal just need more time to spread over a larger photocathode. Due to this physical constraint, only the 18mm image intensifiers can provide highest shutter speeds with gating times down to 200 picoseconds.

Input Window

The standard input window is made of quartz. This limits the UV spectral range at about 200nm. The optional Magnesium Fluoride (MgF2) window enables measurements below this marge, please ask for detailed information.

Photocathode

Photocathodes define the sensitivity and the spectral response of image intensifiers. More about photocathodes ...

Multi-channel-plate (MCP)

Image intensifiers can be equipped with single or double stage MCP's. The single MCP is standard and fits most of the applications of ultra-high speed ICCD cameras. The V-stacked double MCP's are especially used for extreme low light environments. The increased electron multiplication enables single photon detection and reduces the ion feedback noise. Therefore, the double MCP is mainly used for long exposure measurements, extreme low light applications and single photon counting. More about multi-channel plates ...

Phosphor screen

There are three important considerations in choosing a luminous (phosphor) output screen. First the efficiency, second the phosphor decay time and last the spatial resolution. The two mostly used phosphor screens are P43 and P46. The P43 phosphor screen has a higher efficiency and higher spatial resolution due to smaller grain size. However, it has a long decay time. For fast applications e.g. double frame mode with a interframing time of 500ns the faster decaying P46 phosphor screen is necessary to avoid gost images from the previous exposure. The trade-off of the P46 phosphor screen are lower efficiency and lower spatial resolution. more about phosphor screens ...

Any further questions can be addressed directly to Stanford Computer Optics, Inc or your local distributor.