Fresnel lens

A Fresnel lens comprising an incident surface that is flat, and a prism-forming surface that has a plurality of prisms, the prism-forming surface being provided on a side of the Fresnel lens opposite to the incident surface, wherein:

• each of the prisms has a converging surface that is located on a side away from an optical axis of the Fresnel lens;
• when a distance away from the optical axis in a radial direction of the Fresnel lens is defined as r, and predetermined values R1, R2, and R3 in the radial direction are set so as to satisfy R1<R2<R3,
• a region that satisfies 0≦r≦R2 forms a refractive region where light that passes through an interior of the Fresnel lens is refracted at the converging surface, and
• a region that satisfies R2<r≦R3 forms a reflective region where the light is reflected at the converging surface;
• and
• in a range of 0≦r<R1, a relationship θ2=f(r) holds, and
• in a range of R1≦r<R2, a relationship f(R1)≦θ2<f(r) holds,
• where θ2 represents an angle formed between the incident surface and the converging surface, and f(x) represents a monotonically increasing function with x as a variable.