Today there are a myriad of off-the-shelf test targets and charts on various substrate materials and in a wide range of sizes from a multitude of companies for general or specific applications. To help narrow your chose of the best target/chart for your application it requires some forethought and answers to some basic questions. The following seven general questions will aid in choosing that ideal test target/chart.

1. Will a Reflective or Transmissive method of illumination be used for viewing the target/chart?

  • For Reflective illumination, either photographic style paper or Opal substrate material will be required.
    • The best Photographic style paper has a silver halide compound that is chemically processed for maximum quality and resolution rather than produced through an ink jet or laser printer process. It is a flexible material that can be used on a flat surface or conform around a cylinder holder.
    • Opal is a milky white reflective glass material with chrome or other coating to form the imaged features.
  • For Transmissive illumination, either photographic style Film or Glass substrate material will be required.
    • photographic style Film is flexible transmissive material with a silver halide compound that is chemically processed for maximum quality and resolution.
    • Glass is a rigid breakable material with chrome or other coating to form the imaged features. There are various types of glass materials used to manufacture targets and charts, such as Sodalime, BK-7, B270, Quartz, Fused Silica, and UV glass to name a few.

Each substrate material has different characteristics and limitations.

2. Are there specific light wavelength requirements to illuminate the target/chart?Such as –

  • visible light, 400 to 750 nanometer illumination
  • UltraViolet (UV) light, 400 nanometers or below illumination
  • Near-IR (InfraRed) light, 750 nanometer to 3 micron illumination
  • Mid-IR (InfraRed) light, 3 to 30 micron illumination
  • Far-IR (InfraRed) light, 30 micron or higher illumination
  • Laser illumination
  • Fluorescence illumination, with various excitation & barrier filters and dichroic mirrors
  • or various illumination intensities (i.e. low to extremely bright illumination light levels)

Three interrelated questions:

3. What is the maximum resolution of your viewing system?

4. What will be the smallest feature size required on the target/chart?

5. What is the tolerance requirements for the smallest feature?

These will help further define what substrate material will be required. For example:

  • For Reflective illumination,
    • Photographic paper minimum feature size is 20 microns with a tolerance of +/- 5 microns.
    • Opal has a greater range than photographic paper, its minimum feature size is 2 micron with a tolerance 0f +/- 1 micron.
  • For Transmissive illumination,
    • photographic Film minimum feature size is 5 microns with a tolerance of +/- 2 microns.
    • Glass has a greater range than Film, its minimum feature size is 1 micron with a tolerance of +/- 0.5 micron.

Please note: the above minimum feature size and tolerances are general specifications and maybe greater or lesser for each material type depending on other extraneous factors.

6. Are there environmental consideration for the target/chart?

  • humidity, temperature, or liquid contact a consideration

7. Will multiple features be required on the target/chart and what are their sizes?

  • Defining the number of features and their sizes as well as the maximum viewing area or area of interest within the viewing system can and will determine the overall target/chart size required.

Answering these seven simple questions will begin to narrow down the choices for your ideal target/chart for your specific application:

Further consideration –

There are two basic classifications for targets and charts. They are defined as a single featured target or multi-featured chart.

  • An example of a single featured target would be similar to the USAF-1951 target, a Ronchi grating or a Siemens Star target. While these charts can be used for multiple types of analysis, they consists of one design style repeated multiple times in varying sizes.
  • An example of a multiple featured chart would be similar to the ISO-12233 Digital Still Camera Resolution chart or the AIIM X113 Rotary Test chart. These charts have multiple/various features within the chart which can be used to analyze for different parameters……

These two basic classifications are applicable to all substrate materials.

Targets and Charts can be used for various analysis, such as calibration, alignment, measurement, distortion, resolution or image quality, to name a few.

Calibration. X Scale or X & Y Scale.

Alignment. Pick ’n’ Place, Checkerboard or Dot target.

Measurement. Reticle & X&Y Scale.

Distortion. Ronchi grating, dot pattern target, checkerboard target

Resolution. Ronchi grating, Siemens Star target, RIT Target

Image Quality. ISO-12233, Sinusoidal target array