Abstract: In an exposure apparatus for exposing a photosensitive medium using light-emitting elements, correction to account for environmental conditions at the time of exposure that change is performed by dynamically changing the value of current or voltage to be supplied to the LEDs. Thereby, control of exposure duration can be performed solely for expression of multi-gradation levels, so that a very high resolution is not required for the control of exposure duration. Therefore, it is possible to realize a low-price exposure apparatus capable of printing multi-gradation images. For exposure to a single color using a plurality of LEDs, the gradation level to be expressed by the individual LEDs is cyclically changed, so that the construction of gradation level control for each LED can be simplified. Further, since the LEDs can be used at substantially equal duties, the individual variation of LEDs does not evidently show. It is also possible to prevent an inconvenient incident where a particular LED deteriorates.

Abstract: A pressure developing unit moving along a surface of a cycolor medium to perform pressure development has a first rotating member that faces a platen and is capable of performing pressure development of a recording sheet, and a second rotating member that is capable of transmitting a load applied to the first rotating member to a carriage shaft. If the pressure developing unit is moved along the carriage shaft, the first and second rotating members move by revolving along the recording sheet and the carriage shaft respectively in a direction in which the pressure developing unit moves, so that there is no possibility of sliding friction being caused. The pressure developing unit can be moved along the carriage shaft causing only rolling friction. Thus, it is possible to reduce the size of a motor for moving the pressure developing unit and to realize thereby a recorder that is compact in size and low in power consumption.

Abstract: An exposure head wherein a light-shielding panel having enclosing openings capable of receiving individual LED chips, and a front surface panel having small openings are disposed at a front surface of an LED panel in which the LED chips are arranged, is provided. In the exposure head, the LED chips and bonding wires can be housed in the enclosing openings, and can be protected from a medium to be exposed, by the front surface panel. Therefore, each dot can be irradiated with exposure light from the LED chips, which are disposed close to the photosensitive medium, so that each dot can be exposed without using a lens system. The inside surfaces of the enclosing openings are made reflective to prevent exposure light from leaking from the cells in which the individual LED chips are housed, into other LED chip cells, so that each dot can be exposed to high-intensity exposure light.