An illuminating module includes a light source assembly which includes a first lens unit. The light source assembly is configured to produce an illuminating beam, wherein the optical apparatus includes an optical modulation module and a light guiding module, the optical modulation module is parallel corresponding to the first lens unit, the illuminating beam passes through the optical modulation module to be an image beam having an image, and the image beam travels in the light guiding module, and leaves the light guiding module. The illuminating beam obliquely enters the optical modulation module.