Patent Description:
<CIT> discloses an invention of an image forming apparatus. As shown in <FIG> of the patent literature, the image forming apparatus has a camera unit <NUM> for image inspection. The camera unit <NUM> is provided with a sheet conveyance path <NUM> to convey a sheet from upstream toward downstream while holding the sheet with rollers. Two cameras <NUM> and <NUM> are oppositely provided in the same position on and under the sheet conveyance path <NUM>. In the camera unit <NUM>, the sheet is conveyed in one direction along the sheet conveyance path <NUM>, while the two cameras <NUM> and <NUM> read respective images on the upper and lower surfaces of the conveyed sheet. A sheet inspection device <NUM> uses the obtained images of the sheet sent from the camera unit <NUM> to inspect the images printed on the sheet. Further, <CIT> discloses an image reading apparatus and an image forming system comprising three conveyance members for conveying a sheet and image reading units arranged between conveyance members. In order to inhibit the height of a sheet P from varying in the reading position, the respective speeds and forces of the three conveyance members such that the first conveyance member has the highest holding force, but the lowest speed, while the other two conveyance members have smaller holding forces, but higher speeds. Thereby, a tension is applied to the sheet P whilst being inspected by the image reading units. <CIT> discloses an image forming apparatus with a sheet length measuring device capable of measuring the length of a conveyed sheet. Moreover, <CIT> discloses an image forming apparatus that facilitates user's determination of necessity of setting an inspection resuming page and is improved in jam processing efficiency.

In the image forming apparatus disclosed in <CIT>, the camera unit is provided with a roller conveyance unit, as a sheet conveyance unit, in which the pair of rollers to hold the sheet from positions above and below the sheet is provided at a predetermined interval. The camera unit performs image sensing on images of the sheet between the pairs of rollers. Accordingly, since there is no member to hold and guide the sheet between the pairs of rollers, the position of the sheet conveyed at a high speed is not stable. In some cases, the position of the sheet changes in a direction vertical to the paper surface. When the camera unit is an image sensing device having a shallow depth of focus such as a CIS (Contact Image Sensor), it is impossible to perform image reading when the sheet moves in a focal depth direction.

As shown in <FIG>, the present inventors have invented an image inspection apparatus which inspects images of a print sheet with camera(s) while conveying the print sheet with a suction type conveyance unit. The image inspection apparatus 1a has a printing device <NUM>, an inspection device 3a, and a post-processing device <NUM>, sequentially provided along the print-sheet moving direction.

The printing device <NUM> has plural storage parts <NUM> which hold plural types of print sheets, a loop-shaped conveyance passage <NUM> which is connected to the storage parts <NUM>, and which is capable of conveying the print sheet twice in the same passage while turning over the print sheet by reversing the print sheet, a first conveyance unit <NUM> which is provided in a part of the conveyance passage <NUM>, and which sucks and conveys the print sheet the print sheet, and a printing unit <NUM> which is provided above the first conveyance unit <NUM>, and which discharges ink to form an image on the print sheet conveyed with the first conveyance unit <NUM>. The first conveyance unit <NUM> has a belt conveyer <NUM> having a belt, in which a large number of holes are formed, put around plural rollers, and an unshown suction unit, provided on the lower surface side of the belt conveyer <NUM>, to suck the print sheet on the upper surface side of the belt. The first conveyance unit <NUM> sucks the print sheet on the upper surface side of the belt with the suction unit, and conveys the print sheet by moving the belt. For the sake of convenience, the exposed surface of the print sheet conveyed with the first conveyance unit <NUM> will be referred to as a front surface, and the opposite side, as a rear surface.

The inspection device 3a has a second conveyance unit <NUM> which is connected to the first conveyance unit <NUM> of the previous-stage printing device <NUM>, and which sucks and conveys the print sheet, with the front surface exposed on the upper side, and a first inspection unit <NUM> which is provided in a downward posture above the second conveyance unit <NUM> on the upstream side, and which inspects the image on the front surface of the print sheet. The configuration of the second conveyance unit <NUM> is approximately the same as the configuration of the first conveyance unit <NUM>. Further, on the downstream side of the second conveyance unit <NUM>, a third conveyance unit <NUM> which sucks and conveys the print sheet sent from the previously-stage second conveyance unit <NUM>, with the rear surface exposed to the lower side, and a second inspection unit <NUM>, which is provided in an upward posture below the third conveyance unit <NUM> on the upstream side, and which inspects the image on the rear surface of the print sheet are provided. The configuration of the third conveyance unit <NUM> is approximately the same as the configuration of the first conveyance unit <NUM> and the second conveyance unit <NUM>. However, the third conveyance unit <NUM> is provided in an upside-down posture.

The post-processing device <NUM> is a device to receive the print sheet, having the images on the front and rear surfaces inspected with the inspection device 3a, perform various necessary post-processing on the print sheet, and discharge it as a final product.

According to the image inspection apparatus 1a, a first conveyance speed V1 of the first conveyance unit <NUM> in the printing device <NUM> and a second conveyance speed V2 of the second conveyance unit <NUM> in the inspection device 3a are controlled so as to be substantially the same. When the control is properly performed, no problem occurs in the inspection of the image on the print sheet with the first inspection unit <NUM> of the inspection device 3a.

However, in a state where the first conveyance speed V1 and the second conveyance speed V2 are not substantially the same, when inspecting the image on the print sheet with the first inspection unit <NUM> of the inspection device 3a, a problem occurs in image reading as described below with reference to <FIG> continuously show a state of inspection performed with the first inspection unit <NUM> on the print sheet, sent from the first conveyance unit <NUM> to the second conveyance unit <NUM>, when the second conveyance speed V2 is higher than the first conveyance speed V1 (when the conveyance speed on the downstream side is higher than the conveyance speed on the upstream side).

<FIG> shows a state of image formation with the printing unit <NUM> on the print sheet P being sucked and conveyed with the first conveyance unit <NUM>. The front end of the print sheet P has not reached the second conveyance unit <NUM>. The print sheet P is conveyed at the first conveyance speed V1 (< second conveyance speed V2).

<FIG> shows a state of the image formation with the printing unit <NUM> at the rear end of the print sheet P being conveyed with the first conveyance unit <NUM> and the second conveyance unit <NUM>. The front end of the print sheet P has already reached the second conveyance unit <NUM>. Image inspection is started with the first inspection unit <NUM> while a conveyance force with the second conveyance unit <NUM> is applied to the print sheet. Since the part sucked and conveyed with the first conveyance unit <NUM> is longer than the part sucked and conveyed with the second conveyance unit <NUM>, the print sheet P is conveyed at the first conveyance speed V1 (< second conveyance speed V2).

<FIG> shows a state of the image inspection with the first inspection unit <NUM> on the print sheet P being conveyed with the first conveyance unit <NUM> and the second conveyance unit <NUM> after the completion of the image formation with the printing unit <NUM>. In the print sheet P, the part sucked and conveyed with the second conveyance unit <NUM> is longer than the part sucked and conveyed with the first conveyance unit <NUM>. Accordingly, the print sheet P is conveyed at the second conveyance speed V2 (> first conveyance speed V1). That is, the conveyance speed of the print sheet P is higher.

<FIG> is a graph showing the behavior of the print sheet P in the image inspection shown in <FIG> with the relationship between time elapsed from the start of the conveyance (horizontal axis) and the position of the print sheet P with reference to the position of the start of the conveyance (vertical axis). In the graph, the inclination of the straight line indicates the conveyance speed of the print sheet P. According to the graph, when predetermined time has elapsed since the start of the conveyance of the print sheet P and the print sheet has reached a predetermined position, the conveyance speed of the print sheet P becomes higher. That is, as described with reference to <FIG>, the conveyance speed of the print sheet P increases from the first conveyance speed V1 of the first conveyance unit <NUM> to the second conveyance speed V2 (> first conveyance speed V1) of the second conveyance unit <NUM>.

<FIG> show an example of the image read with the first inspection unit <NUM> in image inspection of the print sheet P in the image inspection apparatus 1a. <FIG> shows the image when it is normally read. <FIG> shows the image read in a state as shown in <FIG> and <FIG>. The image shows hiragana letters (Japanese cursive characters) "a, i, u, e, o," and "ka, ki, ku, ke, ko" continuously and vertically arranged. In <FIG>, the image is read in the direction from top to bottom with the first inspection unit <NUM>.

In the image reading in the image inspection apparatus 1a, when the first conveyance speed V1 and the second conveyance speed V2 are substantially the same, the print sheet is conveyed at a uniform speed (V1=V2). In this case, as shown in <FIG>, there is no disorder in the image read with the first inspection unit <NUM>. However, as described with reference to <FIG> and <FIG>, in a case where the conveyance speed of the print sheet P increases, when the image on the print sheet P conveyed at the relatively low first conveyance speed V1 is read, a long image relatively extended in the conveyance direction as an upper half part in <FIG> is obtained, then, when the image on the print sheet P conveyed at the relatively high second conveyance speed V2 is read, a short image relatively contracted in the conveyance direction as a lower half part in <FIG> is obtained. In this manner, when the conveyance speed of the print sheet P changes in the middle of image reading, disorder occurs in the read image, to disturb execution of proper inspection. In the above-described example, the conveyance speed of the print sheet P increases in the middle of image reading. On the other hand, when the conveyance speed decreases, the obtained image has disorder, i.e., the upper half part is short and the lower half part is long in the reading direction, oppositely to <FIG>.

The present invention solves the objects newly found in the invention which has been made by the present inventors in consideration of the problems of the conventional art. The present invention provides an image inspection apparatus capable of inspecting an image formed on an inspection object while conveying the inspection object from an upstream side conveyance unit to a downstream side conveyance unit.

An image inspection apparatus according to a first aspect of the present invention includes: a downstream-side second conveyance unit configured to convey a sheet-type inspection object conveyed at a first conveyance speed with an upstream-side first conveyance unit, at a second conveyance speed; and an inspection unit configure to inspect an image formed on the sheet-type inspection object conveyed with the second conveyance unit. When the downstream-side second conveyance unit and the upstream-side first conveyance unit both contact and convey the sheet-type inspection object at the same time, the inspection unit is provided at a position such that it is configured to start inspection of the image when a downstream-side part of the sheet-type inspection object, on which a conveyance force of the downstream-side second conveyance unit acts, has a length equal to or longer than a half of a length of the sheet-type inspection object in the conveyance direction and a conveyance speed of the sheet-type inspection object has changed to the second conveyance speed.

In the image inspection apparatus according to the present invention, it is possible to perform inspection on the image on the inspection object with the inspection unit while conveying the inspection object with the upstream-side first conveyance unit and the downstream-side second conveyance unit. At this time, even when the first conveyance speed and the second conveyance speed are not substantially the same, since the timing of the start of the inspection of the image on the inspection object with the inspection unit is behind the change of the conveyance speed of the inspection object to the second conveyance speed, the conveyance speed of the inspection object during the inspection is constantly the second conveyance speed. Since the conveyance speed does not change, no disorder occurs in the image read with the inspection unit.

A first embodiment of the present invention will be described with reference with <FIG> and <FIG>.

As schematically shown in <FIG>, an image inspection apparatus <NUM> has the printing device <NUM>, the inspection device <NUM>, and the post-processing device <NUM>, provided along a direction in which the print sheet P moves. The printing device <NUM> forms an image on the print sheet P. The image formed on the print sheet P is inspected with the inspection device <NUM>. Accordingly, the inspection object in the image inspection apparatus <NUM> according to the present embodiment is the print sheet P on which the image is formed.

The printing device <NUM> has plural storage parts <NUM> which hold plural types of print sheets P, the loop-shaped conveyance passage <NUM> which is connected to the storage parts <NUM>, and which is capable of conveying the print sheet P twice in the same passage while turning over the print sheet by reversing the print sheet, the first conveyance unit <NUM> which is provided in a part of the conveyance passage <NUM>, and which sucks and conveys the print sheet P, and the printing unit <NUM> which is provided above the first conveyance unit <NUM>, and which discharges ink to form an image on the print sheet P conveyed with the first conveyance unit <NUM>. The printing unit <NUM> has plural inkjet heads for different ink colors, and the printing unit <NUM> is capable of forming a color image on the both surfaces of the print sheet P.

The first conveyance unit <NUM> has the belt conveyer <NUM> in which a conveyance belt <NUM> is put around a downstream-side driving roller <NUM>, an upstream-side driven roller <NUM>, and two other small driven rollers 10a and 10b. The conveyance belt <NUM> has a large number of through holes. An unshown platen in which a large number of through holes are formed is in contact with the lower surface side of the conveyance belt <NUM> on the upper side of the first conveyance unit <NUM>. Further, an unshown chamber is attached to the lower surface of the platen. The inside of the chamber is sucked with an unshown fan. In this manner, the first conveyance unit <NUM> is a suction-conveyance unit. When the fan is driven, the air is sucked from the position above the conveyance belt <NUM> through the through holes of the conveyance belt <NUM> and the platen into the chamber. The print sheet P is sucked to the upper surface side of the conveyance belt <NUM>. When the conveyance belt <NUM> is driven, the print sheet P is conveyed at the first conveyance speed V1.

Note that the upstream side and the downstream side mean the upstream side and the downstream side of a conveyance direction in which the respective conveyance units <NUM> to <NUM> convey the print sheet P. Further, for the sake of convenience, the exposed surface of the print sheet P conveyed from the first conveyance unit <NUM> to the second conveyance unit <NUM> will be referred to as a front surface, and the opposite side, a rear surface.

The inspection device <NUM> has the second conveyance unit <NUM> and the first inspection unit <NUM>. The second conveyance unit <NUM> is connected to the first conveyance unit <NUM> in the previous-stage printing device <NUM>. The second conveyance unit <NUM> sucks and conveys the print sheet P with the front surface exposed to the upper side. The first inspection unit <NUM> is set so as to read an image in synchronization with the second conveyance speed V2 of the second conveyance unit <NUM>. The configuration of the second conveyance unit <NUM> is approximately the same as the configuration of the first conveyance unit <NUM>. The second conveyance unit <NUM> conveys the print sheet P at the second conveyance speed V2. The first inspection unit <NUM> is provided in a downward posture above the second conveyance unit <NUM> on the downstream side. The first inspection unit <NUM> inspects an image on the front surface of the print sheet P. The position in which the first inspection unit <NUM> is provided on the downstream side of the second conveyance unit <NUM> is a position downstream of an intermediate position between the first conveyance unit <NUM> and the second conveyance unit <NUM>, indicated with a center line C in <FIG>, by a length L1 which is equal to or longer than a half of the length of the print sheet P. In the image inspection apparatus <NUM>, print sheets P in various sizes may be used. In such case, it is preferable to select a print sheet P having the maximum length in the conveyance direction, as a reference to set the above length L1, among the print sheets P which may be used.

When the length L1 is set as described above, when the front end of the print sheet P has reached the first inspection unit <NUM>, the conveyance force of the first conveyance unit <NUM> acts only on the upstream-side part of the print sheet P having a length shorter than a half of the length of the print sheet P in the conveyance direction. On the other hand, the conveyance force of the second conveyance unit <NUM> acts on the downstream-side part of the print sheet P having a length equal to or longer than a half of the length of the print sheet P in the conveyance direction. That is, the timing of the start of inspection of the image on the print sheet P with the first inspection unit <NUM> is behind the change of the conveyance speed of the print sheet P to the second conveyance speed V2. The conveyance speed of the print sheet P during the inspection is constantly the second conveyance speed V2. Since the conveyance speed does not change, no disorder occurs in the image read with the first inspection unit <NUM>.

The third conveyance unit <NUM> which sucks and conveys the print sheet P sent from the previous-stage second conveyance unit <NUM>, with the rear surface exposed to the lower side, and a second inspection unit <NUM>, provided in an upward posture below the third conveyance unit <NUM> on the downstream side, which inspects an image on the rear surface of the print sheet P, are provided on the downstream side of the second conveyance unit <NUM>. The configuration of the third conveyance unit <NUM> is approximately the same as the configuration of the first conveyance unit <NUM> and the second conveyance unit <NUM>; however, the posture of the third conveyance unit <NUM> is reversed upside down. Further, the second inspection unit <NUM> is set in a position away from an intermediate position between the second conveyance unit <NUM> and the third conveyance unit <NUM> by a length longer than the length L1, on the downstream side.

Note that pressing rollers <NUM> to press floating of the front end of the print sheet P are respectively provided above the driven roller <NUM> of the second conveyance unit <NUM> and below the driven roller <NUM> of the third conveyance unit <NUM>. These pressing rollers <NUM> rotate in accordance with the conveyance belt <NUM>.

The first inspection unit <NUM> and the second inspection unit <NUM> are CIS (Contact Image Sensor) having the same specification. The inspection part to read an image formed on the print sheet P for inspection is not limited to the CIS, but a sensor having other principle or structure may be used, or a camera may be used.

The post-processing device <NUM> performs various post-processing on the print sheet P, on which the image has been formed with the printing device <NUM> then the image has been inspected with the inspection device <NUM>, and discharges the print sheet P. As contents of the post-processing, sorting work includes sorting and stacking, staple binding, lined paper insertion, paper folding in various forms, enclosure in envelopes, and the like. It is possible to provide the post-processing device <NUM> having necessary functions in accordance with purposes.

According to the image inspection apparatus <NUM>, the first conveyance speed V1 of the first conveyance unit <NUM> in the printing device <NUM>, the second conveyance speed V2 of the second conveyance unit <NUM> in the inspection device <NUM>, and a third conveyance speed V3 of the third conveyance unit <NUM> in the inspection device <NUM> are controlled so as to be substantially the same. When the control is properly performed, the images on the print sheet P are inspected with the first inspection unit <NUM> and the second inspection unit <NUM> in the inspection device <NUM> without any problem.

As described in the paragraphs of "Technical Problem", in the image inspection apparatus 1a shown in <FIG>, when the first conveyance speed V1 and the second conveyance speed V2 are not substantially the same, a problem occurs in reading of an image on the print sheet P. As described below in detail, in the image inspection apparatus <NUM> according to the present embodiment, this problem is solved by changing the above-described arrangement of the inspection units <NUM> and <NUM>.

<FIG> are schematic cross-sectional views continuously showing a process of inspection of an image on the print sheet P delivered from the first conveyance unit <NUM> to the second conveyance unit <NUM> with the first inspection unit <NUM> when the second conveyance speed V2 is higher than the first conveyance speed V1 (the conveyance speed on the downstream side is higher than the conveyance speed on the upstream side).

<FIG> shows a state of image formation with the printing unit <NUM> on the print sheet P being sucked and conveyed with the first conveyance unit <NUM>. The front end of the print sheet P has not reached the second conveyance unit <NUM>, and the print sheet P is conveyed at the first conveyance speed V1 (< second conveyance speed V2).

<FIG> shows a state of the image formation with the printing unit <NUM> at the rear end of the print sheet P being conveyed with the first conveyance unit <NUM> and the second conveyance unit <NUM>. The front end of the print sheet P has already reached the second conveyance unit <NUM> and received the conveyance force of the second conveyance unit <NUM>. Since the part sucked and conveyed with the first conveyance unit <NUM> is longer than the part sucked and conveyed with the second conveyance unit <NUM>, the print sheet P is conveyed at the first conveyance speed V1(< second conveyance speed V2). The front end of the print sheet P has reached the second conveyance unit <NUM>, but has not reached the first inspection unit <NUM> around the end of the second conveyance unit <NUM> on the downstream side. Accordingly, the inspection of the image on the print sheet P has not been started yet.

<FIG> shows a state of conveyance of the print sheet P with the first conveyance unit <NUM> and the second conveyance unit <NUM> after the completion of the image formation with the printing unit <NUM>. In the print sheet P, the part sucked and conveyed with the second conveyance unit <NUM> is longer than the part sucked and conveyed with the first conveyance unit <NUM>. Accordingly, the print sheet does not receive the influence of the first conveyance unit <NUM>, and the print sheet is conveyed at the second conveyance speed V2(> first conveyance speed V1). That is, the conveyance speed of the print sheet P is higher than the state shown in <FIG>. However, the print sheet P has not reached the first inspection unit <NUM> yet, and the inspection of the image on the print sheet P has not been started yet. Thereafter, the print sheet P is inspected with the first inspection unit <NUM> while being conveyed at the second conveyance speed V2. During the inspection, the conveyance speed is constantly the second conveyance speed V2. No disorder occurs in the read image, and the inspection is appropriately performed.

Note that the front surface of the print sheet P is subjected to the inspection with the first inspection unit <NUM> then is passed through the second conveyance unit <NUM>, and the rear surface of the print sheet P is subjected to the inspection with the second inspection unit <NUM> while being conveyed with the third conveyance unit <NUM>. As described above, the second conveyance speed V2 and the third conveyance speed V3 are controlled so as to be substantially the same. Even when it is not configured to perform such control, the front end of the print sheet P reaches the second inspection unit <NUM> and inspection is started after the entrance of the part greater than the half of the print sheet P into the third conveyance unit <NUM> and the change of the print sheet conveyance speed to the third conveyance speed V3. Accordingly, during the inspection with the second inspection unit <NUM>, the conveyance speed is constantly at the third conveyance speed V3. Regardless of whether or not the third conveyance speed V3 and the second conveyance speed V2 are the same, no disorder occurs in the image read with the second inspection unit <NUM>. The inspection is appropriately performed on the image read with the second inspection unit <NUM>.

<FIG> are schematic cross-sectional views continuously showing a process of inspection of an image on the print sheet P delivered from the first conveyance unit <NUM> to the second conveyance unit <NUM> with the first inspection unit <NUM>, when the first conveyance speed V1 is higher than the second conveyance speed V2 (the conveyance speed on the upstream side is higher than the conveyance speed on the downstream side).

<FIG> shows a state of image formation with the printing unit <NUM> on the print sheet P being sucked and conveyed with the first conveyance unit <NUM>. The front end of the print sheet P has not reached the second conveyance unit <NUM>, and the print sheet P is conveyed at the first conveyance speed V1 (> second conveyance speed V2).

<FIG> shows a state of the image formation with the printing unit <NUM> at the rear end of the print sheet P being conveyed with the first conveyance unit <NUM> and the second conveyance unit <NUM>. The front end of the print sheet P has already reached the second conveyance unit <NUM> and received the conveyance force of the second conveyance unit <NUM>. Since the part sucked and conveyed with the first conveyance unit <NUM> is longer than the part sucked and conveyed with the second conveyance unit <NUM>, the print sheet P is conveyed at the first conveyance speed V1(> second conveyance speed V2). The front end of the print sheet P has reached the second conveyance unit <NUM>, but has not reached the first inspection unit <NUM> around the end of the second conveyance unit <NUM> on the downstream side. Accordingly, the inspection of the image on the print sheet P has not been started yet.

<FIG> shows a state of conveyance of the print sheet P with the first conveyance unit <NUM> and the second conveyance unit <NUM> after the completion of the image formation with the printing unit <NUM>. In the print sheet P, the part suck-conveyed with the second conveyance unit <NUM> is longer than the part sucked and conveyed with the first conveyance unit <NUM>. Accordingly, the print sheet does not receive the influence of the first conveyance unit <NUM>, and the print sheet is conveyed at the second conveyance speed V2(< first conveyance speed V1). That is, the conveyance speed of the print sheet P is lower than the state shown in <FIG>. However, the print sheet P has not reached the first inspection unit <NUM> yet, and the inspection of the image on the print sheet P has not been started yet. Thereafter, the print sheet P is inspected with the first inspection unit <NUM> while being conveyed at the second conveyance speed V2. During the inspection, the conveyance speed is constantly the second conveyance speed V2. No disorder occurs in the read image, and the inspection is appropriately performed.

Note that the front surface of the print sheet P is subjected to the inspection with the first inspection unit <NUM> then is passed through the second conveyance unit <NUM>, and the rear surface of the print sheet P is subjected to the inspection with the second inspection unit <NUM> while being conveyed with the third conveyance unit <NUM>. As in the case of the inspection process described with reference to <FIG>, regardless of whether or not the third conveyance speed V3 of the third conveyance unit <NUM> and the second conveyance speed V2 of the second conveyance unit <NUM> are the same, no disorder occurs in the image read with the second inspection unit <NUM>. The inspection is appropriately performed.

A second embodiment of the present invention will be described with reference to <FIG>.

<FIG> shows an image inspection apparatus <NUM>' according to the second embodiment. The basic configuration of the image inspection apparatus <NUM>' according to the second embodiment is the same as the configuration of the image inspection apparatus <NUM> according to the first embodiment. In <FIG>, the constituent elements corresponding to the constituent elements of the first embodiment have the same as reference numerals the reference numerals in <FIG>, and the description of the first embodiment will be referred to. As described below, the second embodiment differs from the first embodiment only in the arrangement of the first inspection unit <NUM> and the second inspection unit <NUM>.

As shown in <FIG>, the first inspection unit <NUM> in the image inspection apparatus <NUM>' according to the second embodiment is provided in a downward posture above the second conveyance unit <NUM> on the upstream side. An interval L2 between the first inspection unit <NUM> and the downstream-side end of the first conveyance unit <NUM> on the upstream side is longer than the length of the print sheet. Note that the downstream-side end of the first conveyance unit <NUM> is not the right end of the driving roller <NUM> which is the end as a shape and on which the conveyance belt <NUM> is put, but means the rightmost position in the first conveyance unit <NUM> to apply the conveyance force to the print sheet P. In the present embodiment, considering that the maximum available print-sheet size in the image inspection apparatus <NUM>' is A3, and the vertical length of the A3-sized print sheet is <NUM>, it is set such that L2=<NUM> holds. With this configuration, the length of an inspection device <NUM>' according to the second embodiment in the conveyance direction is longer than the length of the inspection device <NUM> in the conveyance direction in the first embodiment.

As shown in <FIG>, the second inspection unit <NUM> of the image inspection apparatus <NUM>' according to the second embodiment is provided in an upward posture below the third conveyance unit <NUM> on the upstream side. As in the case of the first embodiment, the second conveyance unit <NUM> and the third conveyance unit <NUM> are arrayed without gaps.

In the image inspection apparatus <NUM>' according to the second embodiment, even when an A3-sized sheet is conveyed in portrait as the print sheet P, when the front end of the print sheet P reaches the first inspection unit <NUM>, the rear end of the print sheet P is already away from the first conveyance unit <NUM>. The print sheet P receives only the conveyance force of the second conveyance unit <NUM>. That is, the timing of the start of inspection of the image on the print sheet P with the first inspection unit <NUM> is behind the change of the conveyance speed of the print sheet P to the second conveyance speed V2. The conveyance speed of the print sheet P during the inspection is constantly the second conveyance speed V2. Since the conveyance speed does not change, no disorder occurs in the image read with the first inspection unit <NUM>. As long as the length of the print sheet P in the conveyance direction is shorter than the length of the A3-sized sheet in the conveyance direction, the same advantage is obtained.

Note that in the image inspection apparatus <NUM>' according to the second embodiment, by setting the interval between the downstream-side end of the second conveyance unit <NUM> and the second inspection unit <NUM> to <NUM> as in the case of the above interval L2, the length of the inspection device <NUM>' in the conveyance direction is longer than the length of the inspection device <NUM>' in the conveyance direction shown in <FIG>. However, in the case where the A3-sized sheet is conveyed in portrait as the print sheet P, even when the conveyance speed V2 of the second conveyance unit <NUM> and the conveyance speed V3 of the third conveyance unit <NUM> are not substantially the same, the inspection with the second inspection unit <NUM> is started after the change of the conveyance speed of the print sheet P to the constant conveyance speed V3. Accordingly, no problem occurs in the inspection with the second inspection unit <NUM>.

In the above-described first and second embodiments, the suction-conveyance unit using a suction fan as the conveyance unit is shown. Further, a suction unit using the principle of electrostatic adsorption may be used, i.e., a suction unit having any suction principle and structure may be used. Further, the occurrence of malfunction in the image inspection on the downstream side due to the difference between the upstream-side conveyance speed and the downstream-side conveyance speed is not limited to the suction type conveyance units but the malfunction also occurs in rollerconveyance type conveyance units. The example of this case will be described next as a third embodiment.

The third embodiment of the present invention will be described with reference to <FIG>.

<FIG> shows an image inspection apparatus <NUM>" according to the third embodiment. Among the constituent elements of the image inspection apparatus <NUM>" according to the third embodiment, the constituent elements corresponding to the constituent elements of the first embodiment have the same as reference numerals the reference numerals in <FIG>, and the description of the first embodiment will be referred to. As described below, the third embodiment differs from the first embodiment in the use of a rollertype conveyance unit and in the arrangement of the first inspection unit <NUM>.

As shown in <FIG>, a first conveyance unit <NUM>' of a printing device <NUM>' and a second conveyance unit <NUM>' of an inspection device <NUM>" are roller conveyance units. The first conveyance unit <NUM>' and the second conveyance unit <NUM>' respectively have two pairs of driving roller <NUM> and driven roller <NUM> to convey the print sheet by holding the print sheet P and applying the holding force to the print sheet P. Further, in <FIG>, reference numeral <NUM> denotes a conveyance passage for the print sheet P set from the first conveyance unit <NUM>' through the second conveyance unit <NUM>' to the downstream side.

As show in <FIG>, the arrangement of the first inspection unit <NUM> in the third embodiment differs from the first and second embodiments. In the present embodiment, the first conveyance speed V1 of the upstream-side first conveyance unit <NUM>' and the second conveyance speed V2 of the downstream-side second conveyance unit <NUM>' are controlled so as to be the same. However, the conveyance speeds V1 and V2 may not be substantially the same due to tolerance among the constituent parts. In such case, in a state where the print sheet P is conveyed while being held with only the upstream-side first conveyance unit <NUM>', the conveyance speed of the print sheet P is V1. In a state where the print sheet P is conveyed while being simultaneously held with the upstream-side first conveyance unit <NUM>' and the downstream-side second conveyance unit <NUM>', the conveyance speed of the print sheet P is not constant. Further, in a state where the print sheet is conveyed while being held with only the downstream-side conveyance unit, the conveyance speed of the print sheet P is V2.

Accordingly, in the present embodiment, the first inspection unit <NUM> is provided on the downstream side from the position of the front end of the print sheet P when the conveyance speed has become the second conveyance speed V2 by application of the holding force only from the second conveyance unit <NUM>' to the print sheet P. That is, as shown in <FIG>, assuming that a distance from a nip point between the driving roller <NUM> and the driven roller <NUM> on the downmost stream side at which the first conveyance unit <NUM>' applies the holding force to the print sheet P to the inspection position of the first inspection unit <NUM> is L3, the distance L3 may have any value as long as the length is equal to or longer than a length obtained by subtracting the length of a margin from the front end of the print sheet P to an image reading start position from the length of the print sheet P in the conveyance direction. When the first inspection unit <NUM> is provided in this manner, as shown in <FIG>, immediately after the passage of the rear end of the conveyed print sheet P through the first conveyance unit <NUM>' and the change of the conveyance speed to the constant second conveyance speed V2, the front end of the print sheet P passes through the inspection position of the first inspection unit <NUM> and the inspection is started from the image closest to the front end.

As described above, the conveyance unit in the present invention is not limited to the suction type conveyance unit as in the first and second embodiments. However, when the roller conveyance unit as in the case of the third embodiment is used, there is a possibility that the print sheet flaps in a direction vertical to the drawing during the conveyance. Accordingly, as an inspection unit, it is preferable to use another image inspection device with a shallow focal depth rather than the CIS with a deep focal depth.

A fourth embodiment of the present invention will be described with reference to <FIG> and <FIG>.

<FIG> shows an image inspection apparatus <NUM> according to the fourth embodiment. In the configuration of the image inspection apparatus <NUM> according to the fourth embodiment, the constituent elements corresponding to the constituent elements of the first embodiment have the same as reference numerals the reference numerals in <FIG>, and the description of the first embodiment will be referred to. As described below, the fourth embodiment differs from the first embodiment in that the first inspection unit provided in a downward posture above the second conveyance unit <NUM> includes a camera <NUM> as the first inspection part and a CIS <NUM> as the second inspection part.

Note that <FIG> lacks a constituent element corresponding to the third conveyance unit <NUM>. However, when only the front surface of the print sheet P is to be inspected, such constituent element is not required. It may be configured such that the constituent element corresponding to the third conveyance unit <NUM> is provided for inspection of the rear surface of the print sheet P. In this case, a camera and a CIS may be provided as in the case of the second conveyance unit <NUM>, as the second inspection unit <NUM> provided in an upward posture below the third conveyance unit <NUM>, as needed.

The camera <NUM> has a deep focal depth in comparison with the CIS <NUM> as the second inspection part, and has a comparatively large allowable error of the installation location. As an example of numerical value, assuming that the installation location is <NUM> from an image sensing object, the allowable error is about ±<NUM> to <NUM>. Further, the reading accuracy is relatively high in comparison with the CIS <NUM> as the second inspection part. As an example of numerical value, the reading accuracy is about <NUM> dpi. As the camera <NUM> has this high reading accuracy, the camera <NUM> is used for image sensing an image especially requiring high-accuracy reading, among the images formed on the print sheet P as the inspection object.

<FIG> shows a bar code as an example of the image subjected to image sensing with the camera <NUM>. The bar code is configured with a combination of a narrow bar NB, a wide bar WB, narrow space NS, and wide space WS. The ratio of the width of the narrow bar NB to the width of the wide bar WB, and the ratio of the width of the narrow space NS to the width of the wide space WS, regarding a bar-code reading direction (vertical direction, i.e., a direction orthogonal to the bar in <FIG>) are set to predetermined values, e.g., about <NUM>:<NUM> to <NUM>:<NUM>. The left part of <FIG> shows an image of the bar code read with the camera <NUM> when the print sheet is conveyed at the conveyance speed V1, and the right part of <FIG> shows an image of the same bar code read with the camera <NUM> when the print sheet is conveyed at the conveyance speed V2 higher than the conveyance speed V1. That is, in comparison with the image read when the print sheet is conveyed at the conveyance speed V1, the image read when the print sheet is conveyed at the conveyance speed V2 higher than the conveyance speed V1 is extended in the reading direction. Accordingly, when the conveyance speed of the print sheet changes in the middle of reading of the bar code, since the above-described ratio of the read image of the bar code changes in the image, it is impossible to perform reading. Note that the degree of deviation from the specified value of the ratio of the width of the narrow bar NB to the width of the wide bar WB, defined in the bar code, at which reading is impossible, is determined based on the performance of the reading device (camera).

Accordingly, as in the case of the first inspection unit <NUM> in the first embodiment, the camera <NUM> is provided in a position to start image inspection when the conveyance speed of the print sheet P has changed to the second conveyance speed V2. That is, the camera <NUM> is located in a position downstream of the intermediate position between the first conveyance unit <NUM> and the second conveyance unit <NUM> by a length equal to or longer than a half of the length of the print sheet P (L1 in <FIG> in the first embodiment). In the present embodiment, the position is in the vicinity of the driving roller <NUM> of the second conveyance unit <NUM>.

The CIS <NUM> has a shallow focal depth in comparison with the camera <NUM> as the first inspection part, and has a comparatively small allowable error of the installation location. As an example of numerical value, assuming that the installation location is <NUM> from an image sensing object, the allowable error is about ±<NUM>. Further, the reading accuracy is relatively low in comparison with the camera <NUM> as the first inspection part. As an example of numerical value, the reading accuracy is about <NUM> dpi. As the CIS <NUM> has low reading accuracy, the CIS <NUM> is used for image sensing other image than the image especially requiring high-accuracy reading, among the images formed on the print sheet P as the inspection object. For example, the CIS <NUM> is used for inspection of the entire image printed on the print sheet P based on bitmap data. The necessity of use of the camera <NUM> for this image reading is low, and the CIS <NUM> is sufficiently available in the point of reading accuracy. Further, even when the conveyance speed of the print sheet P changes upon reading with the CIS <NUM>, the influence on the reading is small. Accordingly, regarding the installation location of the CIS <NUM>, the necessity to satisfy the conditions as in the case of the camera <NUM> is low. That is, the CIS <NUM> may be provided in the vicinity of the pressing roller <NUM> on the upstream side from the camera <NUM> in the second conveyance unit <NUM>.

In the image inspection apparatus <NUM> according to the fourth embodiment, the object of reading with the camera <NUM> is a bar code which requires high accuracy reading. The reading accuracy of the camera <NUM> has a resolution necessary for bar code reading. Further, the timing of the start of the inspection of the image on the print sheet P with the camera <NUM> is behind the change of the conveyance speed of the print sheet P to the second conveyance speed. Accordingly, even when the first conveyance speed and the second conveyance speed are not substantially the same, the conveyance speed of the print sheet P during the inspection of the print sheet P with the camera <NUM> is constantly the second conveyance speed, and the conveyance speed does not change. No disorder occurs in the image read with the camera <NUM>, and no problem occurs in the reading. On the other hand, the object of reading with the CIS <NUM> with relatively low reading accuracy is an image which does not require high accuracy reading. Even when the conveyance speed of the print sheet P changes in the middle of conveyance of the print sheet P, no substantial problem occurs in the reading with the CIS <NUM>. Note that a bar-code reader to perform optical reading by using laser or the like may be used in place of the camera <NUM>.

A fifth embodiment of the present invention will be described with reference to <FIG>.

<FIG> shows an image inspection apparatus <NUM> according to the fifth embodiment. Among the constituent elements of the image inspection apparatus <NUM> according to the fifth embodiment, the constituent elements corresponding to the constituent elements of the first embodiment have the same as reference numerals the reference numerals in <FIG>, and the description of the first embodiment will be referred to. As described below, the fifth embodiment differs from the first embodiment in that the first inspection unit provided in a downward posture above the second conveyance unit <NUM> includes two cameras, i.e., a camera 31a and a camera 31b, as the first inspection part.

Note that <FIG> lacks a constituent element corresponding to the third conveyance unit <NUM> in the first embodiment. However, when only the front surface of the print sheet P is to be inspected, such constituent element is not required. It may be configured such that in <FIG>, the constituent element corresponding to the third conveyance unit <NUM> of the first embodiment is provided for inspection of the rear surface of the print sheet P. In this case, as the second inspection unit <NUM> provided in an upward posture below the third conveyance unit <NUM>, two cameras may be provided as in the case of the second conveyance unit <NUM>, as needed.

The camera 31a and the camera 31b are the same as the camera <NUM> according to the fourth embodiment. The camera 31a and the camera 31b are high reading-accuracy inspection units respectively having a deep focal depth and a comparatively large allowable error of the installation position in comparison with the CIS.

One of the cameras, the camera 31a is used for image sensing of an image which requires especially high accuracy reading among images formed on the print sheet P as the inspection object. More particularly, the camera 31a reads a bar code as described in the fourth embodiment. As in the case of the camera <NUM> according to the fourth embodiment, the camera 31a is provided in a position to start image inspection when the conveyance speed of the print sheet P has changed to the second conveyance speed V2. That is, the camera 31a is located in a position downstream of the intermediate position between the first conveyance unit <NUM> and the second conveyance unit <NUM> by a length equal to or longer than a half of the length of the print sheet P (L1 in <FIG> in the first embodiment). In the present embodiment, the position is in the vicinity of the driving roller <NUM> of the second conveyance unit <NUM>.

Further, the other one of the cameras, the camera 31b, is used for image sensing other image than the image especially requiring high-accuracy reading, among the images formed on the print sheet P as the inspection object. For example, the camera 31b is used for reading a page number (numeral) of the print sheet, other characters, and the like. In a case where characters are read with the camera, even when the conveyance speed of the print sheet changes, the influence on the reading is small in comparison with the case of bar code. Accordingly, regarding the installation location of the camera 31b, the necessity to satisfy the conditions as in the case of the camera <NUM> is low. That is, the camera 31b may be provided in the vicinity of the pressing roller <NUM> on the upstream side from the camera 31a in the second conveyance unit <NUM>.

In the image inspection apparatus <NUM> according to the fifth embodiment, the object of reading with the camera 31a is a bar code which requires high accuracy reading. The reading accuracy of the camera 31a has a resolution necessary for bar code reading. Further, the timing of the start of the inspection of the image on the print sheet P with the camera 31a is behind the change of the conveyance speed of the print sheet P to the second conveyance speed. Accordingly, even when the first conveyance speed and the second conveyance speed are not substantially the same, the conveyance speed of the print sheet P during the inspection of the print sheet P with the camera 31a is constantly the second conveyance speed, and the conveyance speed does not change. Accordingly, no disorder occurs in the image read with the camera <NUM>, and no problem occurs in the reading. On the other hand, the object of reading with the camera 31b with relatively low reading accuracy is an image which does not require high accuracy reading. Even when the conveyance speed of the print sheet P changes in the middle of conveyance of the print sheet P, no substantial problem occurs in the reading with the camera 31b. Note that a bar-code reader to perform optical reading by using laser or the like may be used in place of the camera 31a.

The characteristic feature of the image inspection apparatus <NUM>, <NUM>' or <NUM>" according to a first aspect is that, the image inspection apparatus <NUM>, <NUM>' or <NUM>" has: the downstream-side second conveyance unit <NUM> to convey the sheet-type inspection object P, conveyed at the first conveyance speed V1 with the upstream-side first conveyance unit <NUM>, at the second conveyance speed V2; and the inspection unit <NUM> to inspect an image formed on the inspection object P conveyed with the second conveyance unit <NUM>. The inspection unit <NUM> is provided in the position to start image inspection when the conveyance speed of the inspection object P has changed to the second conveyance speed V2.

In the image inspection apparatus <NUM>, <NUM>' or <NUM>" according to the first aspect, it is possible to perform inspection on the image on the inspection object P with the inspection unit <NUM> while conveying the inspection object P with the upstream-side first conveyance unit <NUM> and the downstream-side second conveyance unit <NUM>. At this time, even when the first conveyance speed V1 and the second conveyance speed V2 are not substantially the same, the timing of the start of the inspection of the image on the inspection object P with the inspection unit <NUM> is behind the change of the conveyance speed of the inspection object P to the second conveyance speed V2. Accordingly, the conveyance speed of the inspection object P during the inspection is constantly the second conveyance speed V2, and the conveyance speed does not change. No disorder occurs in the image read with the inspection unit <NUM>.

The characteristic feature of the image inspection apparatus <NUM>, <NUM>' or <NUM>" according to the second aspect is that, in the image inspection apparatus <NUM>, <NUM>', or <NUM> according to the first aspect, the inspection unit <NUM> is provided on the downstream side of the position of the front end of the inspection object P when the holding force to determine the conveyance speed of the inspection object P is applied with the second conveyance unit <NUM> or <NUM>'.

In the image inspection apparatus <NUM>, <NUM>', or <NUM>" according to the second aspect, it is possible to perform inspection on the image on the inspection object P with the inspection unit <NUM> while holding and conveying the inspection object P with the upstream-side first conveyance unit <NUM> and the downstream-side second conveyance unit <NUM>. Note that the inspection unit <NUM> is provided on the downstream side from the position of the front end of the inspection object P when the holding force of the conveyance unit to determine the conveyance speed of the inspection object P is applied with the second conveyance unit <NUM> or <NUM>'. Accordingly, even when the first conveyance speed V1 and the second conveyance speed V2 are not substantially the same, the timing of the start of the inspection of the image on the inspection object P with the inspection unit <NUM> is behind the change of the conveyance speed of the inspection object P to the second conveyance speed V2 by the operation of the holding force of the second conveyance unit <NUM>, <NUM>'. Accordingly, the conveyance speed of the inspection object P during the inspection is constantly the second conveyance speed V2, and the conveyance speed does not change. No disorder occurs in the image read with the inspection unit <NUM>.

The characteristic feature of the image inspection apparatus <NUM> or <NUM>' according to a third aspect is that, in the image inspection apparatus <NUM> or <NUM>' according to the second aspect, the first conveyance unit <NUM> and the second conveyance unit <NUM> are suction conveyance units to suck and convey the inspection object P, and that the inspection unit <NUM> is provided in the position downstream of the intermediate position between the first conveyance unit <NUM> and the second conveyance unit <NUM> by the length equal to or longer than a half of the length of the inspection object P.

In the image inspection apparatus <NUM> or <NUM>' according to the third aspect, the inspection unit <NUM> is provided in the position downstream of the intermediate position between the first conveyance unit <NUM> and the second conveyance unit <NUM> by the length equal to or longer than a half of the length of the inspection object P. Accordingly, when the front end of the inspection object P has reached the inspection unit <NUM>, the conveyance force by the suction force of the first conveyance unit <NUM> acts only on the upstream-side part of the inspection object P having the length shorter than a half of the length of the inspection object P in the conveyance direction. On the other hand, the conveyance force by the suction force of the second conveyance unit <NUM> acts on the downstream-side part of the inspection object P having the length longer than a half of the length of the inspection object P in the conveyance direction. That is, the timing of the start of inspection of the image on the inspection object P with the inspection unit <NUM> is behind the change of the suction force of the second conveyance unit <NUM> applied to the inspection object P to be larger than the suction force of the first conveyance unit <NUM> applied to the inspection object P and the change of the conveyance speed of the inspection object P to the second conveyance speed V2. Accordingly, the conveyance speed of the inspection object P during the inspection is constantly the second conveyance speed V2. Since the conveyance speed does not change, no disorder occurs in the image read with the inspection unit <NUM>.

The characteristic feature of the image inspection apparatus <NUM> or <NUM>' according to a fourth aspect is that, in the image inspection apparatus <NUM> or <NUM>' according to the first aspect, the interval between the downstream-side end of the first conveyance unit <NUM> and the inspection unit <NUM> is longer than the length of the inspection object P.

In the image inspection apparatus <NUM> or <NUM>' according to the fourth aspect, since the interval between the downstream-side end of the first conveyance unit <NUM> and the inspection unit <NUM> is longer than the length of the inspection object P, when the front end of the inspection object P has reached the first inspection unit <NUM>, the rear end of the inspection object P is already away from the first conveyance unit <NUM>. The inspection object P has received only the conveyance force of the second conveyance unit <NUM>. That is, the timing of the start of inspection of the image on the inspection object P with the inspection unit <NUM> is behind the change of the conveyance speed of the inspection object P to the second conveyance speed V2. Accordingly, the conveyance speed of the inspection object P during the inspection is constantly the second conveyance speed V2. Since the conveyance speed does not change, no disorder occurs in the image read with the inspection unit <NUM>.

The characteristic feature of the image inspection apparatus <NUM> according to a fifth aspect is that, in the image inspection apparatus according to the first aspect, the inspection unit includes the first inspection part <NUM> having relatively high reading accuracy and the second inspection part <NUM> having relatively low reading accuracy, and that the first inspection part <NUM> is provided in the position to start inspection of the image when the conveyance speed of the inspection object P has changed to the second conveyance speed V2.

In the image inspection apparatus <NUM> according to the fifth aspect, the reading accuracy of the first inspection part <NUM> is high in comparison with the second inspection part <NUM>. Further, since the timing of the start of the inspection of the image on the inspection object P with the first inspection part <NUM> is behind the change of the conveyance speed of the inspection object P to the second conveyance speed V2, even when the first conveyance speed V1 and the second conveyance speed V2 are not substantially the same, the conveyance speed of the inspection object P during the inspection of the inspection object P with the first inspection part <NUM> is constantly the second conveyance speed V2, and the conveyance speed does not change. Accordingly, no disorder occurs in the image read with the first inspection part <NUM>, and no problem occurs in the reading. On the other hand, when the object of reading with the second inspection part <NUM> with relatively low reading accuracy is an image which does not require high accuracy reading, even when the conveyance speed of the inspection object P changes in the middle of conveyance of the inspection object P, no substantial problem occurs in the reading with the second inspection part <NUM>.

The characteristic feature of the image inspection apparatus <NUM> according to a sixth aspect is that, in the image inspection apparatus according to the first aspect, the inspection unit includes the at least two first inspection parts 31a and 31b having relatively high reading accuracy, and that, of the at least two first inspection parts 31a and 31b, the first inspection part 31a to read an image which requires high-accuracy reading is provided in the position to start inspection of the image when the conveyance speed of the inspection object P has changed to the second conveyance speed V2. The first inspection part of the present invention includes the two first inspection parts 31a and 31b in the above-described embodiments; however, the first inspection part may include three inspection parts or more. Of the three inspection parts or more, the one first inspection part or more to read an image which requires high-accuracy reading is provided in the position to start inspection of the image when the conveyance speed of the inspection object P has changed to the second conveyance speed V2.

Claim 1:
An image inspection apparatus (<NUM>; <NUM>'; <NUM>") comprising:
a downstream-side second conveyance unit (<NUM>) configured to convey a sheet-type inspection object in a conveyance direction at a second conveyance speed, the sheet-type inspection object being conveyed at a first conveyance speed with an upstream-side first conveyance unit (<NUM>) in the conveyance direction; and
an inspection unit (<NUM>) configured to inspect an image formed on the sheet-type inspection object conveyed with the second conveyance unit (<NUM>),
characterized in that, when the downstream-side second conveyance unit (<NUM>) and the upstream-side first conveyance unit (<NUM>) both contact and convey the sheet-type inspection object at the same time, the inspection unit (<NUM>) is provided at a position such that it is configured to start inspection of the image when a conveyance force of the downstream second conveyance unit (<NUM>) acts on a downstream-side part of the sheet-type inspection object having a length equal to or longer than a half of a length of the sheet-type inspection object in the conveyance direction and a conveyance speed of the sheet-type inspection object has changed to the second conveyance speed.