A reversible DC motor drive includes a DCDC converter having a DC input, a first output having a first pulsed DC voltage and first DC voltage value, a second output having a second pulsed DC voltage and second DC voltage value, and a third output having a third pulsed DC voltage and third DC voltage value. A PCB bracket is in the upper shell, and a PCB with a camera lens and a sensor is fixed on the PCB bracket; a film clip rail is fixed in the upper shell, a pulley track is under the film clip rail, and a light box is hung under the pulley; the photo framework is in the lower shell; in the lower shell, a light board is on the photo framework. The integrator produces an output that is quantized to produce a digital output. The illumination unit is therefore suitable for different ophthalmologic devices.