A laser collimator module installed on a mobile device for a camera program installed in the mobile device to operate photo-taking. A microprocessor on the mobile device activates a camera unit to record an image with an image data. The image data includes a plurality of pixel values for further retrieving of a set of pixel values horizontally and a pixel value of a dot within the set of pixel values. When the microprocessor matches the set of pixel values with a horizontal distance in the image, the microprocessor renders a point of collimated light projected by the laser collimator module as a reference point for further measurement.