Method for inspecting a soft contact lens for the presence of an orange peel defect

Method for inspecting a soft contact lens (3) for the presence of an unacceptable orange peel defect at the surface of the soft contact lens (3), the method comprising the steps of:

• providing an inspection receptacle (2) having a transparent bottom (20) and containing a liquid (23);
• immersing the soft contact lens (3) to be inspected in the liquid (23);
• illuminating the whole soft contact lens (3) immersed in the liquid through the transparent bottom (20) of the inspection receptacle (2) with incoherent white illumination light (40);
• capturing an image (7) of the soft contact lens (3) at an image capturing location arranged in an image capturing direction (61) which is different from a transmission direction (60) in which a first portion of the illumination light is transmitted through the soft contact lens without being scattered by the soft contact lens (3);
• detecting in the image (7) of the soft contact lens (3) the intensity of white light contained in a second portion of the illumination light which is scattered by the soft contact lens (3) in the image capturing direction (61);
• comparing the detected intensity of the white light contained in the scattered second portion with a predetermined threshold intensity;
• determining whether the image (7) of the soft contact lens (3) comprises at least one coherent area (70, 71, 72) at the surface of the soft contact lens in which the detected intensity of the white light contained in the scattered second portion is higher than the predetermined threshold intensity, the at least one coherent area (70, 71, 72) at the surface of the soft contact lens having a size larger than a predetermined threshold size;
• and
• rejecting the soft contact lens (3) as comprising an unacceptable orange peel defect at the surface of the soft contact lens in case the size of the at least one coherent area (70, 71, 72) is larger than the predetermined threshold size,
• wherein the soft contact lens (3) comprises pigment particles giving the soft contact lens (3) a pale color, and wherein the scattered second portion of the illumination light causes the image (7) of the soft contact lens to have a background color which is complementary to the pale color of the soft contact lens (3), and wherein the at least one coherent area (70, 71, 72) at the surface of the soft contact lens is an area of white color mixing with the background color.