Image scanning apparatus

There is provided an image scanning apparatus which can restrict unevenness in rotation of a transmission, and can substantially make constant a sub-scanning interval so as to prevent lowering of an image quality. In the case where a movement rate of sub-scanning is set with use of a stepping motor 16, an integer rotation of a first gear 12 is controlled so as to be set as one step of sub-scanning movement. Further, in the case where a transmission means is composed of a plurality of gears (first gear 12, second gear 14), the plurality of gears have the number of teeth which is set so that when one (the second gear 14) of gears meshing with each other makes one rotation, the other (the first gear 12) thereof makes an integer rotation.

BACKGROUND OF THE INVENTION
 1. Field of the Invention
 The present invention relates to an image scanning apparatus which can
 effect a sub-scanning operation by relatively and intermittently moving a
 main scanning unit and a recording medium stepwise, and can record or read
 an image by driving the main scanning unit each time the sub-scanning is
 stopped.
 2. Description of the Prior Art
 A number of image recording apparatuses for recording an image in an image
 scanning apparatus have been developed nowadays, which are each mounted
 with a digital exposure system. Generally, in the digital exposure system,
 an image is recorded on a recording medium in such a manner that a light
 beam outputted from a semiconductor laser is modulated with image data and
 the light beam is deflected by high-speed rotation of a polygon mirror
 (main scanning), and further the light beam reflected by the polygon
 mirror is subjected to sub-scanning with use of a galvano-mirror or the
 like, or the above main scanning is effected repeatedly while moving the
 recording medium (or moving the recording medium stepwise). In this case,
 as the recording medium, a photosensitive drum electrified by a corona
 discharge, a photosensitive material or the like may be used. Also, in
 place of the semiconductor laser, other light emitter such as an LED may
 be used as a light source.
 In case of repeating the above main scanning while shifting the recording
 medium in a stepwise manner, it is general that a stepping motor is used
 for activating its stepwise movement. The stepping motor is suitable for
 performing a highly precise positioning because a stop position of the
 recording medium can be controlled according to pulse control.
 A transmission system is usually interposed between a rotary shaft of the
 stepping motor and a conveying roller for carrying the recording medium,
 and a rotational speed of the stepping motor is transmitted to the
 conveying roller so as to be decelerated.
 SUMMARY OF THE INVENTION
 However, the aforesaid transmission system comprises a plurality of gears
 which mesh with each other. For this reason, even if the rotational speed
 of the stepping motor is controlled with high precision, there is a case
 where a step movement rate varies due to a meshing tolerance of these
 gears. If the step movement rate is not uniform, an interval between
 adjacent two main scanning operations (hereinafter referred to just as a
 main scanning interval) becomes irregular, whereby troublesome striped
 patterns occur in an image to cause a deterioration of an image quality
 thereof.
 Taking such circumstances into consideration, it is an object of the
 present invention to provide an image scanning apparatus which can
 restrict unevenness in rotation of a transmission system, and can
 substantially make constant a main scanning interval so as to prevent a
 deterioration of an image quality.
 To achieve the above object, the invention described in claim 1 provides an
 image scanning apparatus comprising: a drive motor; sub-scanning means for
 relatively and intermittently moving a main scanning unit and a recording
 medium stepwise when a driving force of the motor is transmitted; and main
 scanning means for effecting a main scanning operation by driving the main
 scanning unit each time a sub-scanning operation is stopped, wherein the
 image scanning apparatus further includes transmission means which is
 composed of a plurality of gears meshing with each other, and varies a
 rotational speed of the motor so that the driving force thereof is
 transmitted to the sub-scanning means, and is characterized in that one
 integer rotation of a selected one of the plurality of gears is adapted to
 be set as one step of a sub-scanning movement in the step movement.
 In accordance with the present invention described in claim 1, the gear is
 not strictly driven at an equal linear velocity within one rotation; for
 this reason, there is unevenness in the rotation due to a runout tolerance
 in a diameter direction. But an average linear velocity for one rotation
 is constant, and therefore, a feeding rate per one rotation is also
 constant. Based on this fact, one rotation is taken as a unit, and an
 integer rotation is set as one step of sub-scanning movement, whereby even
 if an error is caused in the moving rate of sub-scanning movement during
 its shifting movement, the sub-scanning operation is stopped at equal
 intervals when the main scanning operation is effected, preventing thereby
 an unevenness of the sub-scanning movement.
 The number of teeth of gears is expressed by an integer. Therefore, if one
 gear is selected from the plurality of gears and an integer rotation of
 the selected gear (i.e., a rotation which usually makes constant a tooth
 position in the stopped state of the gear) is set as one step, an error
 which is normally caused when the same teeth are meshed with each other
 may be ignored.
 For example, provided that the number of teeth of a gear (hereinafter,
 referred to as gear A) on a drive source side is 15 and the number of
 teeth of a gear (hereinafter, referred to as gear B) on an output side is
 60, the relationship between the former (gear A) and the latter (gear B)
 is as shown in the following Table 1, and an error is converged at the
 number of rotation (a rotational speed) as shown in the Table 1.
 TABLE 1
 The number of integer The number of
 rotation of gear A rotation of gear B Convergence of error
 1 (15 teeth) 1/4 converged at 4 lines
 2 (30 teeth) 1/2 converged at 2 lines
 3 (45 teeth) 3/4 converged at 4 lines
 4 (60 teeth) 1/1 converged at 1 line
 As can be seen from the above Table 1, if four rotations of the gear A is
 set as one step, the gear B makes one rotation, and both gears A and B
 make an integer rotation, and an error is converged every one line. This
 is the most preferable selection of the gear.
 The invention described in claim 2 provides the image recording apparatus
 according to claim 1, in which the selected gear is a final step gear of
 the plurality of gears connected.
 In accordance with the invention described in claim 2, claim 1 has shown
 that an error may be converged at some few lines in number. Further, in
 the case where gears are connected to each other, there is the need of
 taking all the number of teeth of the gear connected in the downstream
 side of the selected gear into consideration. In the case where one gear
 is selected from the plurality of connected gears, if the final step gear
 thereof is selected, the only selected gear may be controlled so as to
 make an integer rotation; therefore, adjustment can be readily performed.
 In the above description, if the gear B is the final step gear, an error
 is constantly converged every one line, and a stable sub-scanning
 operation can be effected.
 The invention described in claim 3 provides the image recording apparatus
 according to claim 1 or 2, in which the plurality of gears have the number
 of teeth which is set in such a manner that two of those gears meshing
 with each other make an integer rotation.
 In accordance with the invention described in claim 3, the rotation of the
 gear is set so as to make an integer rotation. In this case, the
 sub-scanning moving rate is actually an extremely small value; for this
 reason, deceleration is a basic concept. If the gear on a drive side is
 set so as to make an integer rotation each time the gear on an output side
 makes one rotation, a duration until an error is converged can be
 shortened.
 The invention described in claim 4 provides the image recording apparatus
 according to any one of claims 1 to 3, in which an index indicative of the
 peak point of an error on a plus side is marked preliminarily onto one of
 the two gears meshing with each other and an index indicative of the peak
 point of an error on a minus side is preliminarily marked onto the other,
 and the two gears mesh with each other so that the two peak points meet
 each other.
 In accordance with the invention described in claim 4, it is preferable
 that an error is offset when gears mesh with each other. An index
 indicative of the peak point of the error on a plus side and an index
 indicative of the peak point of the error on a minus side are previously
 marked onto one and the other of the two gears meshing with each other,
 respectively. And then, the aforesaid two gears are meshed with each other
 so that the above two peak points meet each other, and by doing so, the
 error can be restricted by the minimum limitation even though a reference
 gear (e.g. a gear in which its one rotation is set as one sub-scanning) is
 not the final step gear.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
 Overall Structure (Exterior View)
 Referring now to FIGS. 1 to 3, an image recording apparatus 100 according
 to the preferred embodiment of the present invention is shown therein.
 The image recording apparatus 100 reads image data recorded on an optical
 disk 102 and an FD 104 (see FIG. 3) to expose onto a photosensitive
 material 106, and transfers an image recorded on the photosensitive
 material 106 to an image receiving paper 108 and outputting the image
 receiving paper.
 An upper portion of the front surface of a box-shaped casing 110 (left-hand
 side in FIG. 3) is formed as an inclined surface, and an operation
 indicating portion 112 is provided thereon.
 As shown in FIG. 2, the operation indicating portion 112 is divided into a
 monitor portion 114 and an input portion 116 which are disposed on right
 and left sides, respectively. The monitor portion 114 allows the read
 image to be projected thereon.
 The input portion 116 is composed of a plurality of operation keys 118 and
 a display portion 120 for confirmation of input data, and allows input of
 data which is required for image recording, for example, the number of
 sheets to be recorded, size setting, color-balance adjustment,
 negative/positive selection, and the like.
 A deck portion 122 is provided below the operation indicating portion 112.
 The deck portion 122 is composed of an optical-disk deck portion 124 and
 an FD deck portion 126 which are disposed at right and left sides of FIG.
 2, respectively.
 The optical-disk deck portion 124 is provided in such a manner that a tray
 130 can be opened and closed by pressing an open/close button 128. An
 optical disk 102 can be loaded in an interior of the apparatus in such a
 manner as to be placed on the tray 130.
 On the other hand, an FD insertion slot 132 is provided in the FD deck
 portion 126. When the FD 104 is inserted into the FD insertion slot, a
 drive system of the apparatus is actuated so as to insert the FD 104 into
 the apparatus. Further, in order to take out the FD 104 from the FD deck
 portion 126, an operation button 134 is pressed to pull out the FD 104.
 Access lamps 136 and 138 are respectively provided for the optical-disk
 deck portion 124 and the FD deck portion 126 so that they are each turned
 on during access in the apparatus.
 A discharge tray 140 is provided further below the deck portion 122. The
 discharge tray 140 is usually accommodated in the apparatus, and is
 provided so as to be pulled out by an operator's finger being put on a
 holding portion 142 (see FIG.
 The image receiving paper 108 on which the image is recorded is discharged
 onto the discharge tray 140.
 The image receiving paper 108 is previously accommodated on a tray 144 in a
 layered form. The tray 144 is loaded into a tray mounting hole 146 formed
 on an upper surface of the casing 110. The image receiving papers 108 are
 taken out one by one from the tray 144 mounted in the tray mounting hole
 146, and after images are transferred onto the image receiving papers 108,
 these image receiving papers 108 are guided to the discharge tray 140.
 Two circular cover members 148 and 150 are attached to the right side
 surface of the casing 110 (toward the front side on the paper of FIG. 1).
 These cover members 148 and 150 are each provided so as to be
 independently movable. As shown in FIG. 3, a feed reel 152 and a take-up
 reel 154 onto which the rolled photosensitive material 106 is wound are
 respectively disposed in the apparatus along axial directions of the cover
 members 148 and 150. These reels 152 and 154 can be taken out from or
 loaded into the apparatus in a state in which the cover members 148 and
 150 are removed therefrom.
 Image Receiving Paper Conveying System
 As shown in FIG. 3, the tray 144 loaded in the tray mounting hole 146 is
 set so that an upper surface of the leading end of the tray faces a
 semicircular roller 156.
 The semicircular roller 156 is formed in such a state that a cylindrical
 roller is cut along a plane parallel to an axis thereof. Usually, a
 cutting surface 158 of the semicircular roller 156 faces an uppermost
 image receiving paper 108 in the tray 144 at a predetermined interval.
 When the semicircular roller 156 rotates, the image receiving paper 108 of
 the uppermost layer and peripheral surface of the semicircular roller 156
 contact with each other, and then, the image receiving paper 108 is pulled
 out by a small amount when the semicircular roller 156 makes one rotation.
 The pulled-out image receiving paper 108 is nipped by a first roller pair
 160, and is completely pulled out from the tray 144 by a driving force of
 the first roller pair 160.
 A second roller pair 162, a guide plate 164 and a third roller pair 166 are
 successively disposed at the downstream side of the first roller pair 160.
 The image receiving paper 108 is, after having been nipped by the first
 roller pair 160, nipped by the second roller pair 162, guided by the guide
 plate 164, and then, is further nipped by the third roller pair 166.
 In the third roller pair 166, the image receiving paper 108 overlaps with
 the photosensitive material 106. Namely, the third roller pair 166 is also
 used as a conveying path of the photosensitive material 106.
 Photosensitive Material Conveying System
 The photosensitive material 106 is accommodated in the apparatus in a state
 of being elongated and wound onto the feed reel 152 in a layered form. The
 feed reel 152 is mounted at a predetermined position in such a manner that
 the cover member 150 (on the rear side of the apparatus) is removed and
 the feed reel 152 is inserted into the apparatus in the axial direction
 thereof.
 With the photosensitive material 106 being mounted at the predetermined
 position, loading of the photosensitive material 106 is effected along a
 predetermined conveying path in a state that the outermost layer of the
 photosensitive material 106 is pulled out as an initial setting. The
 photosensitive material 106 is loaded in the following procedure that the
 outermost layer thereof is pulled out from the feed reel 152, nipped by a
 fourth roller pair 168 situated in the vicinity of the feed reel 152,
 conveyed through a reservoir portion 170 and a guide plate 172, and is
 nipped by the third roller pair 166, and thereafter, the outermost layer
 is successively wound onto a heat roller 174 and a take-up reel 154. In
 this case, a leader tape having a length required for loading may be
 provided at the leading end portion of the photosensitive material 106
 wound onto the feed reel 152.
 On the conveying path of the photosensitive material 106, an exposure
 section 176 is provided between the fourth roller pair 168 and the
 reservoir portion 170. Further, a water applying portion 178 is provided
 between the reservoir portion 170 and the guide plate 172. The exposure
 section 176 and the water applying portion 178 will be described later in
 detail. After the image has been exposed onto the photosensitive material
 106 in the exposure section 176, the photosensitive material 106 overlaps
 with the image receiving paper 108 at the third roller pair 166 in a state
 in which water is applied to an emulsion surface (i.e., a surface to be
 exposed) of the photosensitive material.
 Referring now to FIG. 6, there is schematically shown a drive system for
 driving the aforesaid fourth roller pair 168.
 One (e.g. an upper side roller) of the roller pair 168 is an idle roller
 168A; the other (e.g. a lower side roller) thereof is a drive roller 168B.
 A first gear 12 which constitutes a part of a transmission system means is
 coaxially attached to the rotary shaft 10 of the drive roller 168B so that
 the drive roller 168B can be coaxially rotated with the rotation of the
 first gear 12.
 The first gear 12 engages with a second gear 14 which constitutes the
 transmission system together with the first gear 12. In this case a gear
 ratio of the first gear 12 to the second gear 14 is set to 4:1.
 Specifically, for example, if the second gear 14 has 20 teeth in its
 number, the number of teeth of the first gear 12 has 80 teeth, which is a
 multiplied integer of 20.
 The second gear 14 is attached to a rotary shaft 16A of a stepping motor 16
 used as a drive source, and is rotated in accordance with a rotation of
 the stepping motor 16.
 When the stepping motor 16 is rotated, a rotating force is transmitted to
 the drive roller 168A through the second gear 14 and the first gear 12,
 and then the roller pair 168 is rotated, so that the photosensitive
 material 16 nipped by the roller pair 168 can be conveyed.
 In general, since a gear has characteristics such that it is not strictly
 driven at an equal linear velocity within one rotation; for this reason,
 there is unevenness due to a runout tolerance in a diameter direction.
 However, as an average linear velocity every one rotation is constant, a
 feeding rate per one rotation is also constant.
 FIG. 7 shows unevenness of the linear velocity when the first gear 12 is
 rotated. In this case, the gear characteristic is shown in the form of a
 sine wave because unevenness in a linear velocity of every predetermined
 tooth is substantially constant. Actually, the gear characteristic is not
 shown as an accurate sine wave. Further, in FIG. 7, an abscissa takes a
 time; on the other hand, an ordinate takes an error. An upper side of the
 ordinate is an error on a plus side, while a lower side thereof is an
 error on a minus side.
 As shown in FIG. 7, assuming that a start position of one rotation is
 indicated by an arrow S of FIG. 7, it can be seen that no error in every
 one cycle occurs therein, and an average linear velocity in every one
 rotation is constant.
 For this reason, in the case where a movement rate of the sub-scanning is
 set by use of the stepping motor 16, an integer rotation of the first gear
 12 is controlled so as to be set as one step of a sub-scanning movement.
 Moreover, in the case where the transmission system is composed of a
 plurality of gears (first gear 12, second gear 14) like this embodiment,
 the number of teeth of the plurality of gears is set such that one (first
 gear 12) of two gears which are engaged with each other makes an integer
 rotation while the other (second gear 14) thereof makes one rotation.
 In FIG. 8, there is shown unevenness of a linear velocity when the second
 gear 14 is rotated. The condition or the like is the same as the first
 gear 12.
 As shown in FIG. 8, a frequency of the second gear 14 is higher than that
 of the first gear 12, wherein smaller and shorter sine waves are repeated
 more frequently. However, four cycles of the second gear 14 coincides with
 the first gear 12 at a point (see an arrow "P" of FIG. 9) where there is
 no discrepancy therebetween. In other words, the first gear 12 returns to
 an initial state at every one rotation, so that an error accumulation is
 avoided.
 Heat Roller
 The heat roller 174 serves as a heat development transfer section of the
 present apparatus, and is composed of a cylindrical roller main body 180
 and a heater 182 which is provided in the roller main body 180 along the
 axial direction of the roller main body. Further, the heat roller 174
 serves to apply heat to members wound onto the roller main body 180 (i.e.,
 the photosensitive material 106 and the image receiving paper 108) in such
 a manner that the surface of the roller main body 180 is heated by
 actuation of the heater 182. The heating of the heat roller 174 allows
 heat development transfer processing, and the image recorded on the
 photosensitive material 106 is thereby transferred onto the image
 receiving paper 108.
 A peeling roller 184 and a peeling claw 186 are disposed in the vicinity of
 a lower right side of the heat roller 174, and are provided so as to
 separate, from the photosensitive material 106, the image receiving paper
 108 wound onto the heat roller 174 by a length of about one third (1/3) of
 the overall circumference of the heat roller 174 to guide the image
 receiving paper 108 toward the discharge tray 140.
 On the other hand, the photosensitive material 106 is wound onto the heat
 roller 174 by a length of about a half (1/2) the overall circumference of
 the heat roller 174, and is turned to an opposite direction so as to be
 guided to a position where the take-up reel 154 is mounted.
 Water Applying Portion
 As shown in FIG. 3, the water applying portion 178 operates to apply water,
 serving as an image forming solvent, onto the photosensitive material 106
 or the image receiving paper 108 to allow overlapping surfaces of the
 photosensitive material 106 and the image receiving paper 108 to closely
 adhere to each other for heat development. Further, the water applying
 portion 178 is composed of an applying member 188 extending along a
 transverse (widthwise) direction of the photosensitive material 106 and a
 tank 190 in which water is filled.
 The applying member 188 is formed of a high absorptive material such as
 felt, sponge or the like, having a proper degree of hardness, and is
 provided so as to contact with the photosensitive material 106 at a
 predetermined pressure during conveying of the photosensitive material
 106. Water filled in the tank 190 is constantly supplied to the applying
 member 188 by a proper amount by taking advantage of a capillary
 phenomenon. When the photosensitive material 106 and the applying member
 188 contact with each other, water is applied onto the surface (i.e., the
 emulsion surface) of the photosensitive material 106 by means of the
 applying member 188.
 Further, since the applying member 188 abuts against the photosensitive
 material 106 at a proper pressure, water is uniformly applied to the
 photosensitive material 106.
 Replenishment of water into the tank 190 is effected in such a manner that
 the entire water applying portion 178 is removed from the apparatus, but
 water may be constantly supplied from an exterior of the apparatus by
 using a pipe arrangement.
 Meanwhile, in the present embodiment, water is used as the image forming
 solvent, but the water used in this embodiment is not limited to pure
 water and also includes water which is widely and generally used. Further,
 a mixed solvent of water and a low-boiling-point solvent such as methanol,
 DMF, acetone, diisobutylketone or the like may be used. Moreover, a
 solution which contains an image formation accelerator, an anti-fogging
 agent, a development stopping agent, hydrophilic heat solvent or the like
 may also be used.
 Exposure Section
 In FIG. 4, there is shown an exposure section 176 according to the present
 embodiment.
 The exposure section 176 is mainly formed of a light source unit 200 which
 is provided above the conveying path of the photosensitive material 106,
 and is connected to a controller 202. The controller 202 is provided with
 a memory in which an image signal (the image signal read from the optical
 disk 102 or FD 104) is stored, and turns on a light source portion 204 in
 the light source unit 200 in accordance with the image signal. The light
 source unit 200 is movable in the transverse direction (main scanning
 direction) of the photosensitive material 106 by a drive of a main
 scanning unit 206 which will be described later. The main scanning
 operation is effected when the photosensitive material 106 is step-driven
 and stops in the exposure section 176.
 The light source unit 200 of the exposure section 176 is covered by a
 box-shaped exposure casing 214. The light source portion 204 is disposed
 on the upper end surface of the exposure casing 214, and a light emission
 surface of the light source portion 204 is directed toward an interior of
 the exposure casing 214. An aperture 216 is provided for each of colors on
 the side of the light emission surface of the light source portion 204 so
 as to limit scattering of light from a plurality of LED chips 208.
 Meanwhile, the structure having no aperture 216 may also be provided.
 A telecentric lens 212 is provided on the lower side of the aperture 216
 and at the central portion of the exposure casing 214, and serves to
 converge a light from the light source portion 204 so as to form an image
 on the photosensitive material 106. Meanwhile, the resolution of an image
 thus formed is about 250 to 400 dpi.
 The telecentric lens 212 is composed of a plurality of lenses and a
 diaphragm, and has characteristics in which magnification thereof does not
 vary even when the height of an image surface changes. The telecentric
 lens 212 can eliminate an error possibly caused by a vibration generated
 during the main scanning movement made by the main scanning unit 206, and
 that caused by a state in which the exposure casing 214 is mounted.
 Further, the focus of the telecentric lens 212 is constantly adjusted by
 means of an automatic focusing mechanism (not shown). Alternatively, the
 telecentric lens 212 may also be formed as a lens system whose depth of
 focus is large so as to eliminate the need of adjustment of the focus.
 The light source unit 200 is supported by a pair of guide shafts 218 which
 are disposed parallel to each other and forming a part of the main
 scanning unit 206. The guide shafts 218 are provided along the transverse
 direction of the photosensitive material 106 (i.e., the direction
 indicated by an arrow W in FIG. 4). The light source unit 200 is guided by
 the guide shafts 218 so as to be movable in the transverse direction of
 the photosensitive material 106.
 A portion of an endless timing belt 220 is fixed at the exposure casing 214
 of the exposure section 204. The timing belt 220 is entrained onto
 sprockets 222 positioned in the vicinity of both ends of the pair of guide
 shafts 218. A rotary shaft of one of the sprockets 222 is connected via a
 transmission 224 to a rotary shaft of a stepping motor 226. The light
 source unit 200 is moved along the guide shafts 218 by a reciprocating
 rotation of the stepping motor 226.
 The drive of the stepping motor 226 is controlled by the controller 202,
 and is synchronized with the step driving of the photosensitive material
 106. Specifically, in a state in which the photosensitive material 106 is
 move by one step and stops, the stepping motor 226 starts rotating to move
 the light source portion 204 on the photosensitive material 106 along the
 transverse direction of the photosensitive material 106. When the stepping
 motor 226 is rotated in the reverse direction after a predetermined number
 of pulses has been confirmed, the light source portion 204 returns to its
 original position. And thereafter, a subsequent movement of the
 photosensitive material 106 starts synchronously with the returning motion
 of the light source portion 204.
 A photodiode 228 is provided at the side where a light is emitted from the
 light source portion 204 so as to face the photosensitive material 106,
 and outputs a signal corresponding to a quantity of light from the light
 source portion 204 in which light has been received. The photodiode 228 is
 connected to a light-quantity correction unit 230, and the signal
 corresponding to the quantity of light is inputted to the light-quantity
 correction unit 230.
 The light-quantity correction unit 230 compares the quantity of light from
 the LED chips 208 of each of the detected colors with a quantity-of-light
 value predicted from a correcting fixed signal so as to adjust density and
 color balance, and further, outputs a correction value to the controller
 202. The image signal to be transmitted to the light source portion 204 is
 corrected on the basis of the correction value, and each LED chip 208 is
 then turned on at a proper quantity of light.
 As shown in FIG. 5, the light source portion 204 is formed with a plurality
 of LED chips 208 being arranged in group. These LED chips 208 which emit
 light of colors of blue (B), green (G) and red (R) (when described below
 for each of the colors, the LED chip which emits light of blue is referred
 to as B-LED chip 208B, the LED chip which emits light of green is referred
 to as G-LED chip 208G, and the LED chip which emits light of red is
 referred to as R-LED chip 208R) are mounted onto a substrate 210 along the
 transverse direction of the photosensitive material 106 (i.e., the main
 scanning direction) for each of the colors in accordance with the same
 arrangement rule. Meanwhile, the wavelength of light from the R-LED chip
 208R is 650.+-.20 nm, the wavelength of light from the G-LED chip 208G is
 530.+-.30 nm, and the wavelength of light from the B-LED chip 208B is
 470.+-.20 nm.
 On the substrate 210 in the plan view shown in FIG. 5, ten B-LED chips 208B
 are arranged in two rows and in a zigzag manner at the right end, ten
 R-LED chips 208R are arranged in two rows and in a zigzag manner at the
 left end, and ten G-LED chips 208G are arranged in two rows and in a
 zigzag manner at the central position. Namely, the totaled six rows of LED
 chips 208 are arranged.
 A predetermined wiring arrangement is provided on the substrate 210 by
 etching processing or the like, and each wire is covered by metal for heat
 dissipation so as not to cause a short circuit between the wires. For this
 reason, generation of heat due to the LED chips 208 being turned on can be
 restricted, and variation of an amount by which light is emitted can also
 be limited.
 The dimension of each of parts of the light source portion 204 applied to
 the present embodiment are as follows.
 The horizontal and vertical dimensions (XXY) of the substrate 210 are
 5.times.5 mm (maximum) and the outer dimension of each LED chip 208
 (x.times.y) are about 360.times.360 .mu.m. The row pitch P of the same
 color LED chips is 600 .mu.m, the line pitch L of each row of the LED
 chips is 520 .mu.m, and the distance D of a stepped portion formed in the
 zigzag arrangement along the vertical direction of the substrate is 260
 .mu.m. The distance G of a space between the adjacent groups of LED chips
 cannot be univocally determined, but is determined by the telecentric lens
 212. Preferably, the respective distances G between the R-LED chips 208R
 and the G-LED chips 208G and between the G-LED chips 208G and the B-LED
 chips 208B are equal to each other.
 The diagonal line section of each of the LED chips 208 shown in FIG. 5 is a
 region from which light is actually emitted. As shown by the chain line of
 FIG. 5, borders of the light emission region in the adjacent rows of LED
 chips formed in the zigzag arrangement are provided to correspond to each
 other.
 The light source portion 204 having the above-described structure allows
 recording of ten main scanning lines by one main scanning operation for
 each of colors on the photosensitive material 106. For this reason, a step
 movement of the photosensitive material 106 is controlled such that the
 photosensitive material 106 is driven and stopped repeatedly at a pitch of
 ten times of the width of a main scanning line recorded thereon.
 Reservoir Portion
 The reservoir portion 170 is, as described above, disposed between the
 exposure section 176 and the water applying portion 178, and is composed
 of two pairs of nip rollers 192 and 194 and one dancer roller 196. The
 photosensitive material 106 is entrained between the two pairs of nip
 rollers 192 and 194, and a substantially U-shaped slack portion is formed
 in the photosensitive material 106 between these pairs of nip rollers. The
 dancer roller 196 moves up and down correspondingly to the slack portion
 to hold the slack portion of the photosensitive material 106.
 In the exposure section 176, the photosensitive material 106 is moved in a
 stepwise manner, but in the water applying portion 178, it is necessary
 that the photosensitive material 106 be conveyed at a fixed speed so as to
 allow uniform application of water onto the photosensitive material 106.
 For this reason, the difference in the conveying speed of the
 photosensitive material 106 is generated between the exposure section 176
 and the water applying portion 178. In order to eliminate the difference
 in the conveying speed, the dancer roller 196 moves up and down to adjust
 an amount of slack formed in the photosensitive material 106 so that the
 stepwise movement and the constant-speed movement of the photosensitive
 material 106 can thereby be carried out synchronously.
 Next, an operation of the present embodiment will be described.
 An overall flow of an image recording operation will first described below.
 In a state in which the tray 144 is loaded in the tray mounting hole 146,
 the feed reel 152 onto which the photosensitive material 106 is completely
 taken up and the take-up reel 154 which is an empty state are mounted at
 respective predetermined positions, and when a printing start key of the
 operation indication portion 112 is operated in a loading completed state,
 the controller 202 reads and stores image data from the optical disk 102
 or the FD 104.
 When the image data is stored in the controller 202, the feed reel 152 is
 driven to start conveying the photosensitive material 106.
 When the photosensitive material 106 reaches a predetermined position in
 the exposure section 176, the photosensitive material 106 is temporarily
 stopped, and thereafter, image signals of ten lines are outputted from the
 controller 202 to the light source portion 204. The image signals are
 outputted every ten lines, and the light source portion 204 is guided by
 the guide shaft 218 by the drive of the stepping motor 226 so as to move
 along the transverse direction of the photosensitive material 106 (main
 scanning) Prior to the outputting of the image signal, the quantity of
 light for each of the colors from the light source portion 204 is detected
 by means of the photodiode 228, and in the light-quantity correction unit
 230, a correction value for adjustment of density, color balance and the
 like is supplied to the controller 202, to thereby correct the image
 signal. The correction of the image signal is carried out for each image.
 When first main scanning is completed, the photosensitive material 106 is
 moved by one step (10-lines pitch) and stops, and subsequently, second
 main scanning is effected. By repeating the above main scanning, an image
 of one frame is recorded on the photosensitive material 106. The
 photosensitive material 106 on which the image has been recorded is held
 by a drive of only upstream side nip roller pair 192 in the reservoir
 portion 170 (a downstream side nip roller pair 194 is stopped) in the
 state of having a slack portion in the reservoir portion 170 to be
 entrained onto the dancer roller 196. For this reason, the above
 photosensitive material 106 is not provided to reach the water applying
 portion 178.
 When the photosensitive material 106 having a length of one image is
 accumulated in the reservoir portion 170, the nip roller pair 194 at the
 downstream side of the reservoir portion 170 start driving. As a result,
 the photosensitive material 106 (recording of images thereon has been
 completed) is conveyed to the water applying portion 178. In the water
 applying portion 178, the photosensitive material 106 is conveyed at a
 constant speed, and water is uniformly applied to the photosensitive
 material 106 by means of the applying member 188.
 Water is constantly conveyed from the tank 190 to the applying member 188,
 and the photosensitive material 106 is pressed by the applying member 188
 at a predetermined pressure. Thus, a proper amount of water is applied to
 the photosensitive material 106.
 The photosensitive material 106 to which water is applied is guided by
 means of the guide plate 172, and then, is conveyed to the third roller
 pair 166.
 On the other hand, the peripheral surface of the semicircular roller 156
 and the leading end of the image receiving paper 108 contact with each
 other by one rotation of semicircular roller 156, and thereafter, the
 image receiving paper 108 of the uppermost layer is pulled out and is
 nipped by the first roller pair 160. The image receiving paper 108 is
 pulled out from the tray 144 by being driven by the first roller pair 160,
 and waits for arrival of the photosensitive material 106 in the state of
 being nipped by the second roller pair 162.
 Synchronously with the passing of the photosensitive material 106 through
 the guide plate, the first roller pair 160 and the second roller pair 162
 start driving, and the image receiving paper 108 is guided by the guide
 plate 164 and conveyed to the third roller pair 166.
 The photosensitive material 106 and the image receiving paper 108 are
 nipped by the third roller pair 166 in an overlapping state, and are
 conveyed to the heat roller 174. At this time, photosensitive material 106
 and the image receiving paper 108 closely adhere to each other by water
 applied to the photosensitive material 106.
 The photosensitive material 106 and the image receiving paper 108 in the
 above overlapping manner are entrained onto the heat roller 174, and are
 subjected to heat from the heater 182 for heat development transfer
 processing. In other words, the image recorded on the photosensitive
 material 106 is transferred onto the image receiving paper 108 so as to
 form an image on the image receiving paper 108.
 The heat development transfer processing is completed in the state in which
 the image receiving paper 108 is wound onto the heat roller 174 by a
 length of about one third (1/3) the entire circumference of the roller,
 and subsequently, the image receiving paper 108 is separated from the
 photosensitive material 106 by means of the peeling roller 184 and the
 peeling claw 186, and is discharged onto the discharge tray 140 in the
 state of being wound onto the peeling roller 184.
 On the other hand, the photosensitive material 106 is wound onto the heat
 roller 174 by a length of about a half the overall circumference of the
 roller, and thereafter, the photosensitive material 106 moves in the
 tangential direction and is wound onto the take-up reel 154.
 In the apparatus according to the present embodiment, image recording
 operation is effected with a compact structure, and also, the optical disk
 deck portion 124 and the FD deck portion 126 are mounted in the apparatus,
 so that image data can be rapidly taken in. Further, the image to be
 recorded can be checked by use of the monitor portion 114, so that density
 and color balance of the image can be easily adjusted.
 Since the discharge tray 140 is of a type that can be accommodated in the
 apparatus, when the apparatus is unused, an even appearance of the
 apparatus can be obtained by removing the tray 144 accommodating the image
 receiving paper 108, so that a working space can be effectively utilized.
 Moreover, in the apparatus according to the present embodiment, the water
 applying portion 178 and the exposure section 176 are fixed to the
 conveying direction of the photosensitive material 106, and their movement
 relative to the photosensitive material 106 is effected only by the
 movement of the photosensitive material 106, so that a movement mechanism
 can be simplified.
 Here, in a step movement of the photosensitive material 106 according to
 the present embodiment, the meshing state of the first gear 12 and the
 second gear 14, which constitute the transmission system, is set as
 follows in order to sufficiently exhibit positioning precision of the
 stepping motor 16.
 Specifically, the gear ratio of the first gear 12 attached to the rotary
 shaft 10 of the drive roller 168B to the second gear 14 engaging therewith
 is set to 4:1. The numeral itself of this gear ratio has no specific
 features, but a condition is set such that one of the gear ratio is an
 integer multiple of the other.
 When the stepping motor 16 rotates, a rotating force of the stepping motor
 16 is transmitted to the drive roller 168A through the second gear 14 and
 the first gear 12, and thereafter, the roller pair 168 is driven so as to
 convey the photosensitive material 106 held therebetween; however, an
 average linear velocity for each rotation is constant, and the feed rate
 per one rotation is also constant. Therefore, in case of setting a
 movement rate of sub-scanning by use of the stepping motor 16, if the
 integer rotation of the first gear 12 is controlled so as to be set as one
 step of the sub-scanning movement, the width of sub-scanning line can be
 kept constant.
 Since the second gear 14 makes an integer rotation when the first gear 12
 makes one rotation, the first gear 12 returns to the initial state per
 each rotation, so that an error accumulation can be eliminated.
 As described above, in the case where the gear ratio of the first gear 12
 and the second gear 14 is set or a meshing position is determined, even if
 the meshing position of these gears is determined at random, the effect as
 described above can be obtained. As shown in FIG. 10, the gear ratio is
 set such that some mountain portions of one gear and some valley portions
 of the other gear coincide at predetermined positions in the respective
 sine waves, and offset each other (.alpha.-.beta. in FIG. 10) (see points
 shown by an arrow R in FIG. 10(A)). Further, as shown in FIG. 11, if an
 index 18 indicative of the peak position of a plus side (mountain side) is
 marked onto one (e.g. the first gear 12) and an index indicative of the
 peak position of a minus side (valley side) is marked onto the other (e.g.
 the second gear 14), the linear velocity during the sub-scanning operation
 (during movement of the photosensitive material 106) is stabilized. For
 example, even if the main scanning operation is effected while conveying
 the photosensitive material 106 as the need arises, lowering of the image
 quality can be prevented, and assembling work can be also improved.
 Meanwhile, according to the present embodiment, the optical disk deck
 portion 124 and the FD deck portion 126 are mounted in the apparatus, but
 the apparatus may be provided with a deck portion which is capable of
 loading other recording medium (e.g. a magneto-optic disk (MO), a
 phase-change disk (PD), a video tape or the like). Further, the apparatus
 may be provided with an image input terminal which takes in image signals
 from exterior (e.g. a personal computer, television or the like).
 In the present embodiment, LED chips 208 are arranged in a zigzag manner as
 the light source portion 204, but they may be arranged in one row of each
 of colors and lengthwise and crosswise. Further, the number of LED chips
 and the number of rows may be varied for each color.
 As is evident from the above description, the image scanning apparatus of
 the present invention can restrict unevenness in rotation of a
 transmission, and can substantially make constant a sub-scanning interval
 so as to prevent lowering of an image quality.