A color saturation correction method is provided that, by means of a simple circuit configuration, can reduce dissimilarities in picture quality between images that are projected from film and images obtained from video signals, caused by over-saturation of colors in dark scenes. A cap is provided having a closed distal end, being in contact with the outer wall of the cannula, and covering the distal end and the distal end opening of the cannula, the cap being structured to allow the distal end and the distal end opening of the cannula to pass through the cap as the cannula is passed into an eye. The compensating diode is provided in a forward direction with respect to the current supply portion and has a negative temperature characteristic in which a voltage between an anode and a cathode of the compensating diode decreases depending on the increase in temperature.