Filter, illumination device and illumination method

An illumination device comprising:

• a light source for emitting light;
• an optical member for receiving the light emitted from the light source;
• a rotatable wheel having multiple optical color filters which are arranged between said light source and said optical member, the rotatable wheel having at least two filters evenly positioned about the the center of the rotatable wheel for each color of filter on the rotatable wheel, and
• a drive mechanism for driving said rotatable wheel such that the multiple optical color filters sequentially pass across a light path from said light source to said optical member;
• wherein each respective one of the optical color filters affects the light emitted by said light source while the respective one optical color filter passes across the light path, and
• a boundary is provided between one of said multiple optical color filters and another one of said multiple optical color filters, said boundary extending in a direction, and said optical member includes an inlet for receiving light from said optical color filters,
• wherein said inlet extends in a first direction, corresponding to the direction of said boundary when the boundary crosses the light path, for a greater distance than said inlet extends in a second direction.