1. Field of the Invention
The present invention relates to a camera provided with a sight line detecting device capable of detecting the line of sight of the photographer and thereby detecting the object to be photographed.
2. Related Background Art
For detecting the line of sight of the photographer, there is already known a method, as disclosed in the Japanese Patent Laid-Open Application No. 2-5, of illuminating the eye of the photographer and detecting the position of the line of sight thereof from the relative position of the reflected image of the illuminating light on the cornea (hereinafter called Purkinje's first image) and the center of the pupil. Also there is known, as disclosed in the Japanese Patent Laid-Open Application No. 2-138673, a method of illuminating the eye with light sources positioned around an optical system for eye observation, in order to facilitate the detection of the boundary between the pupil and the iris.
Though the Purkinje's first image is detectable with a light source of a relatively low illuminating intensity, the detection of the boundary of the pupil and the iris requires illumination with a light source of considerably high illuminating intensity. It has therefore been difficult to efficiently detect both the Purkinje's first image and the boundary between the pupil and the iris by a same light source, particularly a light source providing a substantially parallel light beam formed by an optical system. Also a configuration with light sources positioned around the optical system for observing the eye may form a shadow of the upper eyelid or the eyelashes depending on the position of the light sources, or a shadow depending on the relative position of the observing optical system and the eye, as will be explained in the following with reference to FIG. 32. FIG. 32 indicates the output of a photoelectric converting element in the ordinate and the position of said element in the abscissa, and showing shows an example of the output signal in a detection line A in case the eye is illuminated by a light source positioned at the upper side of the eye. In this example, the shadow of the upper eyelid is formed in the white and the black of the eye, as well as in the pupil, and a signal resulting from said shadow is superposed on the signal of the eye image. For this reason the difference a between the outputs corresponding to the pupil and the iris becomes smaller, and the precise calculation of the center of the pupil becomes difficult.