An optical measuring machine, comprising: - an optical detection unit equipped with lighting means configured to generate a light beam along a predetermined optical path, and video capturing means at least partly aligned with the lighting means along the optical path in order to receive the light beam; the video capturing means having a predetermined focal length and a preset visual field; - a support, interposed between the lighting means and the video capturing means, comprising a transparent panel defining a supporting stage for a workpiece to be measured and positioned along the optical path to be crossed by the light beam; - movement means (10, 30) configured to produce a relative movement between the transparent panel and the optical detection unit along a direction of movement at right angles to the optical path in order to allow a plurality of frames to be captured of the visual field along the direction of movement defining a measuring area of the machine; a check master connected to the support, extending along at least one direction transversal to the direction of movement and positioned within the measuring area of the machine in a plane located at a distance from the video capturing means equal to the focal length, in order to define an element of comparison for correcting a measuring error wherein the check master comprises at least one segment equipped with a plurality of elements of comparison located in succession along a direction of extension of the segment itself; characterized in that said optical measuring machine comprises a processina unit having a correction module configured to compare a value representing the position of each element of comparison in the image captured by the video capturing means with a corresponding stored reference value, and programmed to calculate the image correction factor for each of the elements of comparison, so as to provide different corrections for each zone of the captured image. - an optical detection unit equipped with lighting means configured to generate a light beam along a predetermined optical path, and video capturing means at least partly aligned with the lighting means along the optical path in order to receive the light beam; the video capturing means having a predetermined focal length and a preset visual field; - a support, interposed between the lighting means and the video capturing means, comprising a transparent panel defining a supporting stage for a workpiece to be measured and positioned along the optical path to be crossed by the light beam; - movement means (10, 30) configured to produce a relative movement between the transparent panel and the optical detection unit along a direction of movement at right angles to the optical path in order to allow a plurality of frames to be captured of the visual field along the direction of movement defining a measuring area of the machine; a check master connected to the support, extending along at least one direction transversal to the direction of movement and positioned within the measuring area of the machine in a plane located at a distance from the video capturing means equal to the focal length, in order to define an element of comparison for correcting a measuring error