Abstract: A wafer holding device, comprising a rotating baseplate, a wafer seat which is provided on the rotating baseplate coaxially with the rotating baseplate and which receives a peripheral edge of a wafer by a circumference, a predetermined number of chuck levers rotatably mounted on the wafer seat so that the chuck levers can be rotated around an axis extending in a tangential direction on a circumference of the rotating baseplate, and springs for resiliently pushing an end of the chuck lever toward the wafer seat, wherein the peripheral edge of the wafer received on the wafer seat is pinched by the wafer seat and the chuck lever.

Abstract: A stencil making apparatus thermo-sensitively perforates a stencil sheet by a thermal print head. The apparatus includes a controlling device for driving contiguous N pieces of heat generating elements of the thermal print head while shifting respectively heat generating timings at every 1/N of a period of one line of main scanning in perforating inputted image data of the one line of the main scanning.

Abstract: A wafer holding device, comprising a rotating baseplate, a wafer seat which is provided on the rotating baseplate coaxially with the rotating baseplate and which receives a peripheral edge of a wafer by a circumference, a predetermined number of chuck levers rotatably mounted on the wafer seat so that the chuck levers can be rotated around an axis extending in a tangential direction on a circumference of the rotating baseplate, and springs for resiliently pushing an end of the chuck lever toward the wafer seat, wherein the peripheral edge of the wafer received on the wafer seat is pinched by the wafer seat and the chuck lever.

Abstract: An image is processed by using an error diffusion method of propagating density distribution errors in pixels around a pixel to be noted. A method includes the steps of calculating thresholds (Th.sub.1, Th.sub.2) of densities corresponding to the area ratio between the pixels; selecting a pixel to be noted (f) which are different in the area ratio from each other; calculating errors (E) produced in the peripheral pixels according to the distances from the peripheral pixels to the noted pixel and areas of the individual peripheral pixels; adding the propagated errors to a density of the noted pixel so as to make a rearrangement (f') on the density of the noted pixel; comparing the rearranged density of the noted pixel with the thresholds to obtain a corresponding level (G) represented in a binary form, and obtaining density distribution errors (e).