A photo-detector based calculating means having a grating wheel with integrated lenses is provided. The photo-detector based calculating means having a grating wheel with integrated lenses includes a light source (1), a grating wheel (2), and a photo-detector (3), with the light emitted from the light source (1) impinging upon an input plane of the grating wheel (2). The photo-detector (3) has a set of photo-sensitive chips (31) to receive the working light beams emitted from the grating wheel (2). The input plane of the grating wheel (2) has a ring-shaped lens (24) to focus the light emitted from the light source (1). The output plane (23) of the grating wheel (2) has a plurality of tooth-shaped lenses (25), each projecting perpendicularly to the ring-shaped lens (24), which can focus the working beams after the working beams pass through the output plane (23), thus minimizing interference.