Thermal printer and optical fixing device therefor

A thermal printer for use with a recording medium having at least a thermosensitive layer which develops a color when heated and is fixed when exposed to electromagnetic rays of a specific kind, the thermal printer comprising:

• a transport system for transporting the recording medium along a transport path in a forward direction at a first speed and in a reverse direction at a second speed;
• a thermal head which records an image to the thermosensitive layer while the recording medium is transported in the forward direction;
• a fixing lamp disposed behind the thermal head in the forward direction of the transport path and extending across the transport path, for projecting the electromagnetic rays onto the recording medium to fix the thermosensitive layer after recording;
• a lamp driving device for driving the fixing lamp while the recording medium is transported in the forward direction at the constant speed and then stops with a trailing end portion of the recorded image placed in an illumination area in front of the fixing lamp;
• a shutter movable between a closed position where the shutter is inserted in the illumination area, for shielding the electromagnetic rays from the recording medium, on one hand, and an open position retracted from the illumination area, the direction from the open position to the closed position being substantially reverse to the forward direction of the recording medium;
• a shutter driving device which starts to move the shutter from the open position to the closed position at the same speed as the first speed of the recording medium, immediately after the recording medium stops being transported in the forward direction;
• and
• at least an opening formed through the shutter in parallel to the fixing lamp, the opening being opposed to a low illuminance fraction of the illumination area, while the shutter is moved to the closed position, so as to permit supplementing the electromagnetic rays to a portion of the recording medium that stops in the low illuminance fraction.

A thermal printer for use with a recording medium having at least a thermosensitive layer which develops a color when heated and is fixed when exposed to electromagnetic rays of a specific kind, the thermal printer comprising:

• a transport system for transporting the recording medium along a transport path in a forward direction at a first speed and in a reverse direction at a second speed;
• a thermal head which records an image to the thermosensitive layer while the recording medium is transported in the forward direction;
• a fixing lamp disposed behind the thermal head in the forward direction of the transport path and extending across the transport path, the fixing lamp projecting the electromagnetic rays onto the recording medium to fix the thermosensitive layer after recording;
• a lamp driving device for driving the fixing lamp to project the electromagnetic rays while a trailing end portion of the recorded image stops in an illumination area in front of the fixing lamp, as well as while the recording medium is transported in the reverse direction;
• a shutter movable between a closed position where the shutter is inserted in an illumination area in front of the fixing lamp, for shielding the electromagnetic rays from the recording medium, on one hand, and an open position retracted from the illumination area, the direction from the open position to the closed position being substantially reverse to the forward direction of the recording medium;
• a shutter driving device which starts to move the shutter from the closed position to the open position at the same speed as the second speed of the recording medium, immediately after the recording medium stops being transported in the forward direction with the trailing end portion of the recorded image placed in the illumination area;
• and
• at least an opening formed through the shutter in parallel to the fixing lamp, the opening being opposed to a low illuminance fraction of the illumination area, while the shutter is in the closed position, so as to permit applying a supplementary amount of electromagnetic rays to a portion of the recording medium that stops in the low illuminance fraction.

A thermal printer for use with a thermosensitive recording medium having at least first to third thermosensitive layers for developing first to third colors, the thermal printer comprising:

• a thermal head which records first to third color frames of a full-color image to the first to third thermosensitive layers in a frame sequential fashion while the recording medium is transported along a transport path in a forward direction;
• first and second fixing lamps which are alternatively turned on for projecting first or second kind electromagnetic rays onto the recording medium to fix the first or the second thermosensitive layer, respectively, the first and second fixing lamps extending across the transport path of the recording medium such that an intermediate portion of each of the first and second fixing lamps, where luminance is approximately uniform, extends over a range exceeding a maximum width of the recording medium;
• a photosensor disposed on a lateral side of the recording medium so as to receive the first or the second kind electromagnetic rays from the intermediate portion of the first or the second fixing lamp on the same condition, to detect an illuminance value;
• and
• a control device for controlling the quantity of electromagnetic rays applied to the recording medium in accordance with the illuminance value detected by the photosensor.