Slit lamp incorporating a white light emitting diode or a light emitting diode with adjustable color

The light source 1 in the slit lamp (FIG. 1 ) according to present invention is a white light emitting diode (LED) controlled by a control circuit 8 . The patient's eye is illuminated by an illuminating slit produced as image 7 of the slit 3 by means of Koehler illumination technique. This means that the phosphorescent surface of the LED is projected through the condenser optics 2 onto the rear objective 4 that makes an image of the slit 3 through a prism or a mirror 6 onto the eye. In this way an evenly illuminated image 7 of the slit 3 is formed on the inspected eye. The control circuit 8 ensures a correct ratio between the voltage across the LED and the current flowing through the LED and enables changing of the emitted light intensity. The color of the light does not vary with the intensity of the light. In an embodiment of the invention, the light source of the slit lamp is a LED emitting simultaneously a red, a green, and a blue light. By adjusting the intensity of individual light components, optional color of the slit image 7 can be produced on the eye. So, for colored illumination of the eye, the color filters, which must otherwise be inserted into a white illuminating beam, are not needed.