Filters

The General guidelines section on the How it works? page mentions that for the interactive projection device to work properly, care must be taken to so that all elements (especially the camera) work in the infrared light range. To ensure this, it may be necessary to use appropriately selected optical filters that allow a specific band of light to pass through.

In simple terms, optical filters can be divided into two groups of filters due to their scope of use in interactive systems:

• filters blocking visible light that pass infrared,
• infrared blocking filters that let visible light through.

The first type of filter is required to ensure proper operation of interaction detectors (especially the motion detector and IR pens). The second type of filter can be useful to take advantage of Motioncube's automatic projection area calibration.

Recommended filter models

• Use a gel filter or other flexible filter if you plan to use a CCTV camera whose lens is difficult to remove. These types of filters can be easily adapted (i.e. cut to specific sizes) to the CCTV camera housing and mounted between the housing and the lens (read our how to).

  Examples of filter models that can work:

  • Highest quality:

    • Lee 87c
    • Kodak Wratten 87c

  • Economic variant; lower quality. Combine 2 filters together:

    • "Congo Blue" (LEE (C181) or Rosco (#382))
    • "Primary Red" (LEE (106) or Rosco (#27)).

  • Experimental variant (medium or low quality):

    • dark fragment from an old photographic film,
    • 3.5 inch floppy disc
    • foil used to observe a solar eclipse (search in astronomy stores).

• Use a glass optical filter if you plan to use a usb board camera for easy lens removal. Such filters can be glued directly on the lens (from the side of the camera matrix).

  Examples of filter models that can work:

  • https://www.megapixellenses.com/supplier-131856-infrared-filter-ir-cut-filter

• Use a plastic or acrylic filter to mask the infrared diodes if you plan to build an infrared illuminator in the device.

  Examples of filter models that can work:

  • https://www.edmundoptics.com/f/optical-cast-infrared-ir-longpass-filters/12259
  • https://www.instrumentplastics.co.uk/products/optolite-ir-acrylic-infrared-pass-filters