Optical filter with light source

A display apparatus comprising:

• a display;
• and
• a switchable optical filter comprising a layer of switchable material, the switchable material comprising:
• a photochromic and thermochromic compound configured to cause the switchable material to transition from a first state to a second state in response to light of a wavelength within a first range of wavelengths, and from the second state to the first state in response to heat;
• or a photochromic and thermochromic compound configured to cause the switchable material to transition from the first state to the second state in response to light of a wavelength within the first range of wavelengths, and from the second state to the first state in response to application of a voltage, wherein a light transmittance of the switchable optical filter in the first state is greater than a light transmittance of the switchable optical filter in the second state.

An apparatus comprising:

• a switchable optical filter comprising a layer of switchable material, the switchable material comprising a photochromic compound configured to cause the switchable material to transition from a first state to a second state in response to light of a wavelength within a first range of wavelengths, and from the second state to the first state in response to light of a wavelength within a second range of wavelengths, wherein a light transmittance of the switchable optical filter in the first state is greater than a light transmittance of the switchable optical filter in the second state;
• a light dispersing layer;
• a light source providing light of a wavelength within the first range of wavelengths or the second range of wavelengths, wherein the light source is adjacent to one or more edges of the switchable optical filter such that the light of a wavelength within the first range of wavelengths or the second range of wavelengths is transmitted across the switchable optical filter and is dispersed onto the switchable optical filter by the light dispersing layer;
• and
• a switch for controlling activation of the first light source.