ICCD: Advantages and Disadvantages of Intensified CCD Cameras

This page explores the advantages and disadvantages of ICCD (Intensified Charge Coupled Device).

What is ICCD?

Introduction: ICCD technology was developed to overcome the limitations of standard CCD (Charge Coupled Device) sensors. It utilizes the optical amplification provided by an image intensifier to enhance the capabilities of the basic CCD sensor.

ICCD employs an image intensifier tube to achieve high optical gain and gateable operation.

ICCD-based devices are used in various applications, including spectroscopy, scientific and industrial imaging, and medical diagnostics. Its widespread adoption is largely due to advancements in image intensifier tube technology. The image intensifier acts as a very fast optical switch, capable of capturing optical signals in billionths of a second.

ICCD structure

ICCD consists of an image intensifier tube coupled with a traditional CCD sensor. The light output from the tube is coupled with the CCD in two primary ways: via a fiber optic coupler or a lens. These represent the two main types of ICCD construction. Lens-coupled types use a lens between the image intensifier output and the CCD, instead of a fiber coupler.

The figure above shows a fiber-coupled ICCD type. A critical component in the ICCD design is the power supply. It generates a DC voltage (approximately 600-900 volts) for the MCP (Microchannel Plate) to achieve the desired gain. It also generates a DC voltage (around 4KV-8KV) for the phosphor screen and voltage pulses (about 200 Volts) for gated operation of the photocathode.

Key characteristics of ICCD include spectral response, spatial resolution, gating time, repetition rate, sensitivity, noise, dynamic range, and frame rate. The spectral response of an ICCD camera is determined by the input window, photocathode materials, and photocathode size used within the image intensifier tube.

Let’s delve into the merits and demerits of ICCD based on the two main types: fiber-coupled ICCD and lens-coupled ICCD.

Benefits or Advantages of ICCD

The following are the benefits or advantages of ICCD:

• Fiber-coupled ICCD systems are physically compact and offer low optical distortion levels.
• Highly efficient fiber optic coupled ICCDs enable operation of the image intensifier tube at lower gains, resulting in a better dynamic range and overall performance.
• Lens-coupled ICCDs offer greater flexibility by allowing the device to be used in non-intensified mode.
• ICCDs can be considered cameras with effectively no read noise. This is because the image intensifier amplifies the signal, preventing the CCD section from dominating the camera’s overall noise profile.
• They possess optical shuttering properties, which is a significant advantage over CCD and EMCCD types.

Drawbacks or Disadvantages of ICCD

The following are the drawbacks or disadvantages of ICCD:

• Lens-coupled ICCDs are large in physical size, have low coupling efficiencies, and exhibit increased scatter.
• ICCD cameras have lower resolution compared to CCD cameras.
• Recent developments in finer phosphor deposition, reducing gaps, and reducing the bore of the Microchannel plates have resulted in much better performance, but the resolution is still limited to less than 60 line pairs/mm.