Zoom system for a laser slit lamp

Abstract

The invention relates to a zoom system for imaging, with a variable scale of imaging, a fixed entrance plane (16) onto a likewise fixed target plane (15). The zoom system includes a proximal partial system (T.sub.1) with variable converging power and a distal partial system with fixed converging power. The proximal partial system itself includes a distal component (10) and a proximal component (8), which respectively have a positive converging power. The converging power of the proximal component (8) is substantially greater than the converging power of the distal component (10). The proximal partial system (T.sub.1) acts as a collimator. The rear focal plane is virtual. Between the proximal component (8) and the distal component (10), two components (9a, 9b) with negative converging power are displaceable along the optical axis for varying the magnification. These displaceable components (9a, 9b) have a high converging power, so that a large variation of the imaging scale between 1.times. and 20.times. can be attained with short displacement paths. The zoom system preferably serves for focusing a therapy laser beam in a laser slit lamp. Due to the high converging powers in the proximal portion of the zoom system, the laser beam is greatly widened, and the beam waist is located behind the target plane (15), by which means high intensities in the front region of the eye are avoided.

Dependencies are inferred from the claim text.