An illuminating device comprising: an illuminator having a light emitting side and a top side opposite to the light emitting side; at least one illuminating mechanism particularly consisted of light-emitting diodes and positioned within the illuminator; a clamp; and at least one reversibly operated holding device for fixing the illuminating device, wherein the holding device comprises: a guiding device oriented transverse to the light emitting side; a wing shaped unit fixed on the guiding device, which can be turned in a direction transverse to the light emitting side and can be guided along the guiding device; an unfolding means arranged such that the wing shaped unit is oriented transverse to the guiding device and toward a direction away from the illuminator; a folding means located on the guiding device and on a side of the wing shaped unit opposite to the light emitting side, wherein the wing shaped unit can be unfolded completely over the light emitting side, and the wing shaped unit is reversibly folded up through mechanically contacting with the folding means when being guided away from the light emitting side, and wherein the light emitting side has a basic span larger than a span with the wing shaped unit being folded, characterized in that through rotating of the clamp or a part of the clamp about an axis transverse to the guiding device, the position of the wing shaped unit along the guiding device is moved or fixed. an illuminator having a light emitting side and a top side opposite to the light emitting side; at least one illuminating mechanism particularly consisted of light-emitting diodes and positioned within the illuminator; a clamp; and at least one reversibly operated holding device for fixing the illuminating device, wherein the holding device comprises: a guiding device oriented transverse to the light emitting side; a wing shaped unit fixed on the guiding device, which can be turned in a direction transverse to the light emitting side and can be guided along the guiding device; an unfolding means arranged such that the wing shaped unit is oriented transverse to the guiding device and toward a direction away from the illuminator; a folding means located on the guiding device and on a side of the wing shaped unit opposite to the light emitting side, wherein the wing shaped unit can be unfolded completely over the light emitting side, and the wing shaped unit is reversibly folded up through mechanically contacting with the folding means when being guided away from the light emitting side, and wherein the light emitting side has a basic span larger than a span with the wing shaped unit being folded, characterized in that through rotating of the clamp or a part of the clamp about an axis transverse to the guiding device, the position of the wing shaped unit along the guiding device is moved or fixed. a guiding device oriented transverse to the light emitting side; a wing shaped unit fixed on the guiding device, which can be turned in a direction transverse to the light emitting side and can be guided along the guiding device; an unfolding means arranged such that the wing shaped unit is oriented transverse to the guiding device and toward a direction away from the illuminator; a folding means located on the guiding device and on a side of the wing shaped unit opposite to the light emitting side, wherein the wing shaped unit can be unfolded completely over the light emitting side, and the wing shaped unit is reversibly folded up through mechanically contacting with the folding means when being guided away from the light emitting side, and wherein the light emitting side has a basic span larger than a span with the wing shaped unit being folded, characterized in that through rotating of the clamp or a part of the clamp about an axis transverse to the guiding device, the position of the wing shaped unit along the guiding device is moved or fixed.