Projection system and illumination device

An illumination device comprising:

• a projection system comprising a first lens, a second lens, and a third lens arranged in sequence from a projection surface to an image source surface;
• and
• a cover accommodating the projection system;
• wherein:
• a maximal field-of-view angle DFOV of the projection system satisfies:
• 10°<DFOV<14°;
• a chief ray angle CRA of the projection system satisfies:
• CRA<0.52°;
• a throw ratio TR of the projection system satisfies:
• 4.2<TR<5.9;
• a focal length of the first lens f1 of the projection system and a combined focal length of the second lens and the third lens f23 of the projection system satisfy:
• 0.29<f1/f23<0.75;
• a focal length of the third lens f3 of the projection system and a combined focal length of the second lens and the first lens f12 of the projection system satisfy:
• 0.67<f3/f12<1.73;
• an optical total length OTL of the projection system and a maximum image height UH on the image source surface of the projection system satisfy:
• 12<OTL/IH<15;
• a center thickness CT3 of the third lens and an edge thickness ET3 of the third lens of the projection system satisfy:
• 1.1<CT3/ET3<1.3.