Optical unit with attenuating portion and method of producing the same

A method of producing an optical unit of plastic provided with a surface for incident light, a surface for outgoing light and an attenuating portion therein, wherein the surface for incident light is designed to face a light source and the surface for outgoing light is designed to face an element for receiving light so as to optically connect the light source and the element for receiving light, the light coming from the light source, the method comprising:

• shaping the optical unit in such a way that light that comes from the light source and is incident on the surface for incident light forms a first image of the light source within the optical unit and a second image of the light source after having gone through the surface for outgoing light and
• making plastic in the vicinity of the position where the first image is formed undergo a change in at least one of a value of refractive index and a value of transmittance, using laser that is made to come through the surface for incident light or the surface for outgoing light so as to form the attenuating portion with a desired attenuation factor in the vicinity of the position where the first image is formed.