JP5434034B2 - Imaging apparatus and image reading apparatus - Google Patents

Description

  The present invention relates to an imaging apparatus and an image reading apparatus that reads an image formed on a document using the imaging apparatus.

  2. Description of the Related Art An image reading apparatus that automatically reads an image of a document is used as a reading apparatus such as a copying machine or a facsimile, or a scanner for computer input. In this type of image reading apparatus, a light source provided along the main scanning direction is used to irradiate the original with light, and reflected light from the irradiated original is received by a plurality of light receiving elements arranged along the main scanning direction. Light is received by a light receiving element array having elements. Then, an image on one side of the document is read by relatively moving the reading position of the document by the light receiving element array in the sub-scanning direction. In this type of image reading apparatus, a configuration in which reflected light from a document is imaged on a light receiving element array via an imaging optical system using a lens is widely used.

  Incidentally, in recent years, image reading apparatuses that read not only monochrome images but also color images have become widespread. In the image reading apparatus corresponding to the color image, a plurality of light receiving element arrays corresponding to the respective colors are arranged side by side in the sub-scanning direction.

  When an image on a document is read using a plurality of light receiving element arrays that are shifted in the sub-scanning direction, each light receiving element array reads images at different positions in the sub-scanning direction at the same time. For this reason, the read data of each color read by each light receiving element array is shifted in line units in the sub-scanning direction, and the read data of each color obtained by reading the same position in the sub-scanning direction of the document is output in synchronization. Processing is performed.

  When adopting a configuration in which the light receiving element arrays for each color are arranged shifted in the sub-scanning direction, for example, when vibration occurs in the imaging optical system during the reading operation, the reading data of each color obtained by performing the synchronization process In some cases, color misregistration in the sub-scanning direction may occur. As a technique for reducing this color misregistration, a method is known in which the imaging magnification in the sub-scanning direction is increased with respect to the main scanning direction to reduce the influence of vibration.

  As a conventional technique described in the publication, there is a technique in which an imaging magnification in the sub-scanning direction is increased with respect to the main scanning direction using an anamorphic lens (see Patent Document 1).

  Further, as a conventional technique described in the publication in which an imaging optical system is configured by a reflecting mirror without using a lens, an imaging system is configured by using two reflecting mirrors, and a meridional light beam is transmitted between the two reflecting mirrors. There is a technique for converging to create a conjugate point (see Patent Document 2).

JP-A-3-113396 Japanese Patent Laid-Open No. 2002-48977

  SUMMARY OF THE INVENTION An object of the present invention is to provide a small image forming apparatus having different image forming magnifications in the main scanning direction and the sub-scanning direction.

According to the first aspect of the present invention, a light receiving unit in which a plurality of light receiving element rows arranged in the main scanning direction are arranged in the sub scanning direction, and a power of a cross section in the sub scanning direction is the main scanning direction. in the cross section of the first free-form surface is larger than the power, the first reflection member and said main scanning direction of the cross-section of the power sub scanning direction of the cross section of the second free-form surface is greater than the power that reflects light from the original in, and a second reflecting member for reflecting the light reflected by the first free-form surface of the first reflecting member to the light receiving portion, a plurality of the light receiving element array by the light receiving portion Each of the constituent light receiving elements is set to have a length in the sub-scanning direction larger than a length in the main scanning direction, and light from the document is transmitted between the first free curved surface and the second free curved surface. Configuration to form an image on the light receiving part without intermediate image formation It is, an imaging apparatus, wherein the sub-scanning direction of the imaging magnification with respect to the imaging magnification of the main scanning direction is large.

The invention according to claim 2 further includes a diaphragm member that restricts and restricts light from the first free curved surface to the second free curved surface, and the diaphragm member is the first free curved surface of the first reflecting member. The length of the second reflecting member in the main scanning direction is set to be shorter than that of the second free curved surface, and light reflected by the first free curved surface is reflected toward the second free curved surface by a flat surface. The imaging apparatus according to claim 1 , further comprising a third reflecting member.

According to a third aspect of the invention, the movement of moving a light irradiating means for irradiating light to the original, an imaging apparatus according to claim 1 or 2 wherein, in the sub-scanning direction relative position of the document and the imaging device An image reading apparatus having a unit.

According to the first aspect of the present invention, the imaging device can be made smaller and the light receiving element arrays can be made smaller than the configuration in which the meridional light beam is condensed between the two reflecting mirrors to form the conjugate point. Can improve the S / N ratio of data output from.
According to the second aspect of the invention, as compared with the case not employing the configuration according to this aspect, with the imaging device by reducing the sub scanning direction of the light beam width can be made small, compact imaging optical system Can be
According to the third aspect of the present invention, the image on the document is arranged so as to be shifted in the sub-scanning direction as compared with the case where the imaging magnification in the main scanning direction and the sub-scanning direction are the same. When reading using a plurality of light receiving element arrays, it is possible to improve the S / N ratio of data output from each light receiving element array and reduce the color shift of read data.

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
<Embodiment 1>
FIG. 1 is a diagram illustrating a schematic configuration of an image reading apparatus 1 to which the first embodiment is applied. Here, FIG. 1A shows a side sectional view of the image reading apparatus 1, and FIG. 1B shows a top view of the image reading apparatus 1.
The image reading apparatus 1 includes a reading unit 10 that reads an image of a fixed document, and a platen cover 20 that is attached to the reading unit 10 so as to be openable and closable and is used to fix the document to the reading unit 10. . In FIG. 1B, the description of the platen cover 20 is omitted.

  The reading unit 10 includes an apparatus frame 11 that forms a casing, and a platen glass 12 on which a document is placed in a stationary state. The reading unit 10 moves over almost the entire platen glass 12, moves at a half rate of the full-rate carriage 13 that reads the image of the document through the platen glass 12, and is obtained from the full-rate carriage 13. And a half-rate carriage 14 for supplying the light to the imaging unit. The full rate carriage 13 and the half rate carriage 14 as an example of the moving unit are driven by a motor and a drive system (not shown).

  The full-rate carriage 13 is obtained from an illumination lamp 15 as an example of a light irradiating unit that irradiates white light on the original, a reflector 15A that reflects the irradiation light from the illumination lamp 15 toward the platen glass 12, and the original. A first mirror 16A that receives the reflected light is provided. Further, the half-rate carriage 14 is provided with a second mirror 16B and a third mirror 16C that provide the light reflected by the first mirror 16A to the imaging unit. The reflecting surfaces of the first mirror 16A, the second mirror 16B, and the third mirror 16C are flat. Here, in FIG.1 (b), description of the illumination lamp 15, the reflector 15A, the 1st mirror 16A, the 2nd mirror 16B, and the 3rd mirror 16C is abbreviate | omitted.

  Further, the reading unit 10 includes an image forming unit 30 as an example of an image forming device that optically reduces and forms an image (light image) of the light reflected by the third mirror 16 </ b> C, and the image forming unit 30. A light receiving unit 40 that receives and photoelectrically converts the output light and outputs the light, and a processing circuit 50 that processes light reception data input from the light receiving unit 40 are further provided.

  Here, the imaging unit 30 includes a first curved surface as an example of a first flat mirror 31 on which reflected light from the third mirror 16C is incident, and a first reflecting member on which reflected light from the first flat mirror 31 is incident. The mirror 32, the second planar mirror 33 as an example of the diaphragm member or the third reflecting member on which the reflected light from the first curved mirror 32 is incident, and the reflected light from the second planar mirror 33 are incident and the reflected light is reflected. And a second curved mirror 34 as an example of a second reflecting member that emits toward the light receiving unit 40. Both the first plane mirror 31 and the second plane mirror 33 are held by the first holding member 35 and fixed to the apparatus frame 11, and both the first curved mirror 32 and the second curved mirror 34 are It is held by the second holding member 36 and fixed to the apparatus frame 11. However, in FIG. 1B, the description of the first holding member 35 and the second holding member 36 is omitted. In FIG. 1B, the light receiving unit 40 is hidden behind the first flat mirror 31.

  In the following description, the moving direction of the full rate carriage 13 and the half rate carriage 14 is referred to as a sub-scanning direction x, and the direction perpendicular to the sub-scanning direction is referred to as a main scanning direction y. In the following description, the direction of light from the platen glass 12 to the light receiving unit 40 via various mirrors is referred to as an optical axis direction z. However, in FIGS. 1A and 1B, the direction of light from the platen glass 12 to the first mirror 16A is shown as the optical axis direction z.

  FIG. 2 is a diagram illustrating a schematic configuration of a light receiving unit 40 as an example of a light receiving unit provided in the reading unit 10. The light receiving unit 40 includes a rectangular substrate 41, a red light receiving element array 42, a green light receiving element array 43, and a blue light receiving element array 44 disposed on the substrate 41. The red light receiving element array 42, the green light receiving element array 43, and the blue light receiving element array 44 are arranged along the main scanning direction y, and the light receiving element arrays are arranged in the sub scanning direction x. Is arranged. Here, each of the red light receiving element array 42, the green light receiving element array 43, and the blue light receiving element array 44 is configured by arranging k light receiving elements 45 made of photodiodes or the like on a straight line in the main scanning direction y. . Each light receiving element 45 has a rectangular shape in which a: b = 2: 1, where a is the length in the sub-scanning direction x and b is the length in the main scanning direction y. . The distance between the red light receiving element array 42 and the green light receiving element array 43 and the distance between the green light receiving element array 43 and the blue light receiving element array 44 are distances D, respectively.

  FIG. 3 is a functional block diagram showing the configuration of the processing circuit 50 shown in FIG. The processing circuit 50 includes an analog processing unit 51, an A / D conversion unit 52, a shading correction unit 53, a delay processing unit 54, and an image processing unit 55. The analog processing unit 51 includes red data Ri from the red light receiving element array 42 constituting the light receiving unit 40, green data Gi from the green light receiving element array 43, and blue data Bi from the blue light receiving element array 44. Are input independently. The red data Ri, green data Gi, and blue data Bi input from the light receiving unit 40 are analog data.

The analog processing unit 51 performs analog correction such as gain / offset adjustment for each of the red data Ri, the green data Gi, and the blue data Bi.
The A / D conversion unit 52 converts the red data Ri, the green data Gi, and the blue data Bi subjected to the analog correction into digital data.
The shading correction unit 53 performs shading correction on the input digitized red data Ri, green data Gi, and blue data Bi using each shading data read from a memory (not shown). In the shading correction, input red data Ri, green data Gi, and blue data Bi are respectively applied to the corresponding red light receiving element array 42, green light receiving element array 43, and blue light receiving element array 44. Output correction is performed in accordance with variations in sensitivity of the light receiving element 45, light quantity distribution characteristics of the illumination lamp 15, and the like.

  The delay processing unit 54 corrects a shift caused by a difference in attachment positions of the red light receiving element array 42, the green light receiving element array 43, and the blue light receiving element array 44. In the present embodiment, as shown in FIG. 2, the green light receiving element array 43 is arranged so as to be shifted by the distance D in the sub-scanning direction x with respect to the red light receiving element array 42. The blue light receiving element rows 44 are arranged so as to be shifted by a distance D in the sub scanning direction x. For this reason, in the image reading apparatus 1, when a document reading operation is performed, a specific part (one line in the main scanning direction y) of the document is first read by the blue light receiving element array 44, and then this specific reading is performed. The part is read by the green light receiving element array 43, and finally this specific part is read by the red light receiving element array 42. In other words, at the same timing, the red light receiving element array 42, the green light receiving element array 43, and the blue light receiving element array 44 are reading the images of the parts having different positions in the sub-scanning direction x. become. Therefore, the delay processing unit 54 uses the red data Ri output from the red light receiving element array 42 to be read last as a reference, and uses the green data Gi output from the green light receiving element array 43 as the red data Ri. The blue data Bi output from the blue light receiving element array 44 is delayed by a period corresponding to the distance 2D with respect to the red data Ri (the distance D is set for the green data Gi). Delayed by the corresponding period). As a result, the red data Ri, the green data Gi, and the blue data Bi obtained by reading the same part of the document (the same line in the main scanning direction y) are output from the delay processing unit 54 in synchronization. become. In order to perform such processing, the delay processing unit 54 temporarily stores red data Ri, green data Gi, and blue data Bi for a plurality of lines in the sub-scanning direction x. (Not shown) is provided.

  The image processing unit 55 performs various image processing on the input red data Ri, green data Gi, and blue data Bi, and uses the obtained data as red image data Ro, green image data Go, and blue image data, respectively. Output to an external device as Bo. Examples of processing performed by the image processing unit 55 include γ / gray balance correction, color space conversion, enlargement / reduction, filtering processing, contrast adjustment, and background removal.

  FIG. 4 is a diagram showing an optical path from the reading position of an object on the platen glass 12 to the image plane, that is, the light receiving unit 40 (specifically, the light receiving element 45). Here, FIG. 4A shows an optical path in a yz plane which is a cross section in the main scanning direction y and the optical axis direction z, and FIG. 4B is a cross section in the sub scanning direction x and the optical axis direction z. The optical path in the xz plane is shown. In FIG. 4, the description of the first mirror 16A, the second mirror 16B, and the third mirror 16C disposed in the optical path is omitted. In FIG. 4A, the light receiving unit 40 is hidden behind the first flat mirror 31.

  FIG. 5 is a diagram for explaining the configuration and positional relationship of the surfaces of the members arranged in the optical path. Here, FIG. 5A shows an object (reading position), a first plane mirror 31, a first curved mirror 32, a second plane mirror 33, a second curved mirror 34, and an image plane (light receiving element 45). Relationship between the radius of curvature of each member surface, the tilt angle with respect to the axis in the main scanning direction y (hereinafter referred to as the tilt angle around the y-axis), and the spacing between the surfaces (referred to as the surface spacing in the following description). Is shown. FIG. 5B is a view for explaining the surface shapes of the reflecting surfaces of the first curved mirror 32 and the second curved mirror 34.

In the imaging unit 30, the central axis C at which the reflection surfaces of the first flat mirror 31, the first curved mirror 32, the second flat mirror 33, and the second curved mirror 34 are the center in the main scanning direction y is It is arranged so as to be the center in the scanning direction y.
In the imaging unit 30, the first flat mirror 31 is the longest, the first curved mirror 32 is long, the second curved mirror 34 is long next, with respect to the length in the main scanning direction y. Therefore, in the imaging unit 30, the length of the second plane mirror 33 in the main scanning direction y is the shortest.

  Here, the curvature radii of the object and the image plane are infinite, and the curvature radii of the reflection surfaces of the first plane mirror 31 and the second plane mirror 33 are also infinite. On the other hand, the first curved mirror 32 has a reflecting surface expressed by substituting each constant shown by # 1 in FIG. 5B into the following formula 1, and the second curved mirror 34 is 5 has a reflecting surface expressed by substituting each constant shown by # 2 in FIG. Therefore, the first curved mirror 32 and the second curved mirror 34 have reflecting surfaces having different shapes.

  Here, the reflecting surface of the first curved mirror 32 is a first free-form curved surface that is symmetrical in the main scanning direction y with the central axis C as an axis, and whose power in the xz section is larger than that in the yz section.

  On the other hand, the reflection surface of the second curved mirror 34 is a second free-form surface that is symmetric in the main scanning direction y about the central axis C, and whose power in the yz section is larger than that in the xz section.

  As for the inclination angle around the y axis, the reflection surface of the first plane mirror 31 is −6 °, the reflection surface of the first curved mirror 32 is 6 °, and the reflection surface of the second plane mirror 33 is −6 °. The reflection surface of the second curved mirror 34 is set to 6 °. Since the object and the image plane are the start point and end point of the reflected light, the tilt angle around the y axis is not defined.

  Further, with respect to the surface interval, the first curved surface is 454 mm between the object and the first plane mirror 31 and -80 mm between the first plane mirror 31 and the first curved mirror 32 with respect to the optical axis direction z. The distance between the mirror 32 and the second plane mirror 33 is 80 mm, the distance between the second plane mirror 33 and the second curved mirror 34 is -80 mm, and the distance between the second curved mirror 34 and the image plane is 75 mm. Each is set to 18 mm. Note that the distance between the object and the first flat mirror 31 is kept constant as the full-rate carriage 13 and the half-rate carriage 14 move during the image reading operation.

Now, with reference to FIG. 4, the behavior until the light reflected from the object (original) reaches the image plane (the light receiving element 45 of the light receiving unit 40) will be described.
The light irradiated by the illumination lamp 15 and reflected by the document on the platen glass 12 spreads in the main scanning direction y and the sub-scanning direction x, and spreads in the first mirror 16A, the second mirror 16B, and the third mirror 16C (FIG. 1). Through the first plane mirror 31 via Since the first flat mirror 31 has a flat reflecting surface, the light incident on the first flat mirror 31 is reflected toward the first curved mirror 32 while further spreading in the main scanning direction y and the sub-scanning direction x. Is done.

  Since the first curved mirror 32 has a reflecting surface whose power in the xz section is larger than that in the yz section, the light incident on the first curved mirror 32 is in the sub-scanning direction compared to the main scanning direction y. The light is reflected toward the second flat mirror 33 in a state where it is strongly focused on x. Since the second plane mirror 33 has a shorter length in the main scanning direction y than the first curved mirror 32, only a part of the light reflected by the first curved mirror 32 is incident on the second planar mirror 33. Will do. Since the second flat mirror 33 has a flat reflecting surface, the light incident on the second flat mirror 33 is reflected toward the second curved mirror 34. The second flat mirror 33 reflects only the reflected light around the central axis C among the light reflected from the first curved mirror 32, and thus functions as a diaphragm member in the imaging unit 30. The light reflected by the first curved mirror 32 travels without being imaged until it is incident on the second curved mirror 34 via the second flat mirror 33.

  Since the second curved mirror 34 has a reflecting surface whose power in the yz section is larger than that in the xz section, the light incident on the second curved mirror 34 is in the main scanning direction compared to the sub-scanning direction x. The light is reflected toward the light receiving unit 40 while being strongly condensed by y. With this configuration, the outgoing light emitted from the imaging unit 30 has a higher image magnification in the sub-scanning direction x than that in the main scanning direction y with respect to the incident light incident on the imaging unit 30. . In this example, the reflecting surface of the first curved mirror 32 and the reflecting surface of the second curved mirror 34 are shaped as described above, so that the image magnification in the main scanning direction y of the light emitted from the imaging unit 30 is zero. .22, whereas the image magnification in the sub-scanning direction x is 0.44, which is twice that.

  The light reflected by the second curved mirror 34 is incident on the red light receiving element array 42, the green light receiving element array 43, and the blue light receiving element array 44 constituting the light receiving unit 40. At this time, the light reflected by the second curved mirror 34 is in the main scanning direction on the light receiving surfaces of the light receiving elements 45 constituting the red light receiving element array 42, the green light receiving element array 43 and the blue light receiving element array 44. An image is formed at y and an image is formed also in the sub-scanning direction x. That is, the light receiving surface of each light receiving element 45 is disposed within the range of the focal depth in the main scanning direction y and within the range of the focal depth in the sub scanning direction x, and the image point and the sub scanning in the main scanning direction y. Image points in the direction x are substantially coincident. Since the light receiving surface of each light receiving element 45 has a length a in the sub-scanning direction x that is twice the length b in the main scanning direction y as described above, the light receiving surface of each light receiving element 45 is Compared with the case where the lengths of y in the sub-scanning direction x and main scanning direction are both set to a, more light is taken in. As a result, the S / N ratio of red data Ri, green data Gi, and blue data Bi output from the light receiving unit 40 is improved.

  Here, FIG. 6 shows the distance D in the sub-scanning direction x between the red light receiving element row 42, the green light receiving element row 43 and the blue light receiving element row 44 in the light receiving unit 40, and the object, that is, the platen glass 12 (not shown). FIG. 8 is a diagram illustrating a relationship between the red reading position RP, the green reading position GP, and the blue reading position BP in the sub-scanning direction x in the upper document M.

  In the present embodiment, the reflected light from the document M is received in a state where the image magnification in the sub-scanning direction x is larger than the image magnification in the main scanning direction y (specifically, twice) in the imaging unit 30. Light is incident on the red light receiving element array 42, the green light receiving element array 43, and the blue light receiving element array 44 constituting the unit 40. Therefore, as shown in the lower left of FIG. 6, at the same time, the distance between the red reading position RP read by the red light receiving element array 42 and the green reading position GP read by the green light receiving element array 43, and the green The distance between the green reading position GP read by the light receiving element array 43 and the blue reading position BP read by the blue light receiving element array 44 is a distance E, respectively.

  On the other hand, as in the prior art, the reflected light from the original M is used for the red that constitutes the light receiving unit 40 in a state where the image magnification in the sub-scanning direction x is equal to the image magnification in the main scanning direction y in the imaging unit 30. When the light is made incident on the light receiving element array 42, the green light receiving element array 43, and the blue light receiving element array 44, it is as shown in the lower right of FIG. More specifically, the interval between the red reading position RP and the green reading position GP and the interval between the green reading position GP and the blue reading position BP at the same time are respectively greater than the distance E described above. Wide distance F. In this example, the distance F is twice the distance E due to the difference in image magnification in the sub-scanning direction x.

  In the image reading apparatus 1 of the present embodiment, red data Ri by the red light receiving element array 42, green data Gi by the green light receiving element array 43, and blue light receiving obtained by reading different positions at the same time. The blue data Bi by the element array 44 is processed and synchronized by the delay processing unit 54 provided in the processing circuit 50, and then output as red image data Ro, green image data Go, and blue image data Bo. . For this reason, if speed fluctuation occurs in the full rate carriage 13 or the half rate carriage 14 during the image reading operation, the output red image data Ro, green image data Go, and blue image data Bo are combined to form an image. In this case, there is a possibility that color misregistration due to misalignment in the sub-scanning direction x may occur in a region where reading is performed when speed fluctuation occurs.

  However, in the present embodiment, as described above, by making the image magnification in the sub-scanning direction x larger than the image magnification in the main-scanning direction y in the imaging unit 30, the image magnification in the sub-scanning direction x and the main scanning are set. Compared with the case where the image magnification in the direction y is made equal, the interval between the reading positions of the respective colors is narrowed. For this reason, even when the speed fluctuation occurs in the full rate carriage 13 or the half rate carriage 14 during the image reading operation, the output red image data Ro, green image data Go, and blue image data Bo are combined to generate an image. Color misregistration at the time of configuring is suppressed.

Next, an MTF (Modulated Transfer Function) characteristic of the image reading apparatus 1 to which the present exemplary embodiment is applied will be described.
FIG. 7 is a diagram for explaining the measurement conditions of the MTF characteristics. The inventor measured the MTF characteristics in the main scanning direction y and the sub-scanning direction x using the object height H of the object (original M placed on the platen glass 12) as a parameter. Here, the object height H was normalized by setting H = 0.0 at the center in the main scanning direction y (corresponding to the central axis C) and H = 1.0 at one end in the main scanning direction y. Is. Here, the measurement of the MTF characteristics was performed for three of H = 0.0, H = 0.7, and H = 1.0. Note that the length of the document M in the main scanning direction y, that is, the width is 300 mm.

  FIG. 8 is a diagram illustrating the MTF characteristics of the image reading apparatus 1 according to the present embodiment. In FIG. 8, the horizontal axis is the spatial frequency and the vertical axis is the contrast. For example, y (0.0) shown in the legend in the figure means the MTF characteristic in the main scanning direction y at the object height H = 0.0. The same applies to the other x (0.0), y (0.7), x (0.7), y (1.0) and x (1.0).

Here, it is understood that y (0.0), y (0.7) and y (1.0) draw a similar curve. Therefore, the MTF characteristic in the main scanning direction y has a similar shape regardless of the size of the object height H, that is, the position in the main scanning direction y on the document M. It is understood that x (0.0), x (0.7) and x (1.0) also draw similar curves. Therefore, the MTF characteristic in the sub-scanning direction x has a similar shape regardless of the size of the object height H.
On the other hand, y (0.0) and x (0.0), y (0.7) and x (0.7), y (1.0) and x (1.0) having the same object height H Are compared with each other, it is understood that the MTF characteristics in the sub-scanning direction x are about half of the MTF characteristics in the main scanning direction y.
In the present embodiment, since the image magnification in the sub-scanning direction x is twice as large as the image magnification in the main scanning direction y, the main scanning direction y and the sub-scanning direction x are considered on the basis of the spatial frequency of the document surface. It can be said that the scanning direction x has equivalent MTF characteristics.

<Embodiment 2>
FIG. 9 is a diagram illustrating a schematic configuration of the image reading apparatus 1 to which the second exemplary embodiment is applied. Here, FIG. 9A shows a side sectional view of the image reading apparatus 1, and FIG. 9B shows a top view of the image reading apparatus 1.
The image reading apparatus 1 includes a reading unit 10 and a platen cover 20, and is the same as the first embodiment in that the reading unit 10 includes an apparatus frame 11 and a platen glass 12. The difference from the first embodiment is that a reading unit 60 including a mechanism is provided. The reading unit 60 is configured to move in the sub-scanning direction x using a driving mechanism (not shown).
In the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

FIG. 10 is a cross-sectional view illustrating a schematic configuration of a reading unit 60 provided in the reading unit 10.
The reading unit 60 includes a casing 61 provided with an opening along the main scanning direction y on the upper side, an illumination lamp 15 provided in the casing 61 for irradiating white light on the document, and irradiation from the illumination lamp 15. It includes a reflector 15A that reflects light toward the platen glass 12, and a first mirror 62A, a second mirror 62B, a third mirror 62C, and a fourth mirror 62D that sequentially reflect light reflected from the original. The reflection surfaces of the first mirror 62A, the second mirror 62B, the third mirror 62C, and the fourth mirror 62D are flat. Further, the reading unit 60 optically reduces and optically converts the light image reflected by the fourth mirror 62D, and receives and photoelectrically converts the light output from the image forming unit 30. It further includes a light receiving unit 40 for outputting, and a processing circuit 50 for processing light reception data input from the light receiving unit 40. The constituent members of the imaging unit 30 are the same as those described in the first embodiment, but the arrangement of the constituent members is slightly different.

  FIG. 11 is a diagram for explaining the configuration and positional relationship of the surfaces of the members arranged in the optical path. Here, FIG. 11A shows an object (reading position), a first plane mirror 31, a first curved mirror 32, a second plane mirror 33, a second curved mirror 34, and an image plane (light receiving element 45). The relationship between the curvature radius of the surface of each member, the inclination angle around the y-axis, and the surface spacing is shown. FIG. 11B is a diagram for explaining the radii of curvature of the reflecting surfaces of the first curved mirror 32 and the second curved mirror 34.

  Here, the curvature radii of the object and the image plane are infinite, and the curvature radii of the reflection surfaces of the first plane mirror 31 and the second plane mirror 33 are also infinite. On the other hand, the first curved mirror 32 has a reflection surface expressed by substituting each constant shown by # 1 in FIG. The reflection surface is expressed by substituting the constants indicated by # 2 in FIG. Therefore, the first curved mirror 32 and the second curved mirror 34 have reflection surfaces with different shapes, as in the first embodiment.

  Here, although the shape of the reflection surface of the first curved mirror 32 is slightly different from that described in the first embodiment, it is symmetrical in the main scanning direction y, and the power of the xz section is higher than the power of the yz section. It is a large first free-form surface.

  On the other hand, the reflecting surface of the second curved mirror 34 is slightly different from that described in the first embodiment, but is symmetric in the main scanning direction y, and the power of the yz section is larger than the power of the xz section. It is a second free-form surface.

  As for the inclination angle around the y axis, the reflection surface of the first plane mirror 31 is −6 °, the reflection surface of the first curved mirror 32 is 6 °, and the reflection surface of the second plane mirror 33 is −6 °. The reflection surface of the second curved mirror 34 is set to 6 °. Since the object and the image plane are the start point and end point of the reflected light, the tilt angle around the y axis is not defined.

  Further, with respect to the surface interval, the distance between the object and the first plane mirror 31 is 293.34 mm, the distance between the first plane mirror 31 and the first curved mirror 32 is −40 mm, with respect to the optical axis direction z. The distance between the first curved mirror 32 and the second flat mirror 33 is 40 mm, the distance between the second flat mirror 33 and the second curved mirror 34 is −26 mm, and the distance between the second curved mirror 34 and the image plane is It is set to 27.2 mm. In the present embodiment, since the reading unit 60 moves in the sub-scanning direction x in a state parallel to the platen glass 12, the distance between the object and the first flat mirror 31 is kept constant.

  In the present embodiment, the image magnification in the main scanning direction y of the light emitted from the imaging unit 30 is 0.124 times, whereas the image magnification in the sub-scanning direction x is 0. 248.

  Also in the present embodiment, by making the image magnification in the sub-scanning direction x larger than the image magnification in the main scanning direction y in the imaging unit 30, the image magnification in the sub-scanning direction x and the image in the main scanning direction y are also obtained. Compared with the case where the magnification is made equal, the interval between the reading positions of each color is narrowed. For this reason, even when the speed fluctuation occurs in the full rate carriage 13 or the half rate carriage 14 during the image reading operation, the output red image data Ro, green image data Go, and blue image data Bo are combined to generate an image. Color misregistration at the time of configuring is suppressed.

  FIG. 12 is a diagram illustrating the MTF characteristics of the image reading apparatus 1 according to the present embodiment. In FIG. 12, the horizontal axis is the spatial frequency, and the vertical axis is the contrast. The measurement conditions are the same as those in the first embodiment except that the width of the document is 220 mm.

Here, it is understood that y (0.0), y (0.7) and y (1.0) draw a similar curve. Therefore, the MTF characteristic in the main scanning direction y has a similar shape regardless of the size of the object height H, that is, the position in the main scanning direction y on the document M. It is understood that x (0.0), x (0.7) and x (1.0) also draw similar curves. Therefore, the MTF characteristic in the sub-scanning direction x has a similar shape regardless of the size of the object height H.
On the other hand, y (0.0) and x (0.0), y (0.7) and x (0.7), y (1.0) and x (1.0) having the same object height H Are compared with each other, it is understood that the MTF characteristics in the sub-scanning direction x are about half of the MTF characteristics in the main scanning direction y.
Thus, it can be seen that the MTF characteristics show the same trend as in the first embodiment, although the values themselves are different.

  In the first and second embodiments, the first curved mirror 32 and the second curved mirror 34 are used to make the image magnification in the sub-scanning direction x larger than the image magnification in the main scanning direction y. However, the present invention is not limited to this, and this function may be realized using a plurality of (for example, two) lenses. However, the use of the first curved mirror 32 and the second curved mirror 34 is preferable in that the chromatic aberration of the emitted light is eliminated as compared with the case where a plurality of lenses are used.

  In the first embodiment, the original M is placed on the platen glass 12 and the full rate carriage 13 and the half rate carriage 14 are moved in the sub scanning direction x. In the second embodiment, the reading unit 60 is moved to the sub scanning direction x. The image reading apparatus 1 that reads the image of the document M by moving in the scanning direction x has been described as an example. However, the present invention is not limited to this, and the full-rate carriage 13 and the half-rate carriage 14 or the type that reads the image of the document M by moving the document M in the sub-scanning direction x with the reading unit 60 fixed. It can be applied to any of the above.

  Furthermore, in the first embodiment and the second embodiment, an example in which an image of each RGB color is read using three light receiving element arrays has been described. However, the present invention is not limited to this, and two or more light receiving elements are used. Anything that uses columns may be used. As an example of this, for example, a visible image is read using one light receiving element array, and an invisible image such as an infrared image or an ultraviolet image is read using the other light receiving element array.

  In the first and second embodiments, the second plane mirror 33 is used to stop the reflected light from the original. However, the present invention is not limited to this. For example, perforations are formed in the plate material. You may make it use the slit member etc. which were done.

1 is a diagram illustrating a schematic configuration of an image reading apparatus to which Embodiment 1 is applied. It is a figure which shows schematic structure of a light-receiving unit. It is a block diagram which shows the structure of a processing circuit. It is a figure which shows the optical path from an object to an image surface. In Embodiment 1, it is a figure for demonstrating a structure, positional relationship, etc. of the surface of each member arrange | positioned in an optical path. The intervals in the sub-scanning direction of the red light receiving element array, the green light receiving element array, and the blue light receiving element array in the light receiving unit, and the red reading position, the green reading position, and the blue reading position in the document on the platen glass. It is a figure which shows the relationship with the space | interval of a scanning direction. It is a figure for demonstrating the measurement conditions of a MTF characteristic. 6 is a diagram illustrating MTF characteristics of the image reading apparatus according to Embodiment 1. FIG. It is a figure which shows schematic structure of the image reading apparatus with which Embodiment 2 is applied. It is sectional drawing which shows schematic structure of a reading unit. In Embodiment 2, it is a figure for demonstrating a structure, positional relationship, etc. of the surface of each member arrange | positioned in an optical path. FIG. 10 is a diagram illustrating MTF characteristics of the image reading apparatus according to the second embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Image reading apparatus, 10 ... Reading part, 15 ... Illumination lamp, 30 ... Imaging part, 31 ... 1st plane mirror, 32 ... 1st curved mirror, 33 ... 2nd planar mirror, 34 ... 2nd curved mirror, DESCRIPTION OF SYMBOLS 40 ... Light receiving unit, 41 ... Board | substrate, 42 ... Red light receiving element row | line | column, 43 ... Green light receiving element row | line | column, 44 ... Blue light receiving element row | line | column, 45 ... Light receiving element, 50 ... Processing circuit, 51 ... Analog processing part, 52 ... A / D conversion unit, 53 ... Shading correction unit, 54 ... Delay processing unit, 55 ... Image processing unit, 60 ... Reading unit, x ... Sub-scanning direction, y ... Main scanning direction, z ... Optical axis direction

Claims (3)

A light receiving section in which a plurality of light receiving element rows arranged in the main scanning direction are arranged in the sub scanning direction;
A first reflecting member that reflects light from the document with a first free-form surface whose power in the cross section in the sub-scanning direction is larger than that in the cross section in the main scanning direction;
The light reflected by the first free curved surface of the first reflecting member is directed toward the light receiving unit with a second free curved surface whose power in the cross section in the main scanning direction is larger than that in the sub scanning direction. A second reflecting member that reflects,
Each of the light receiving elements constituting the plurality of light receiving element arrays in the light receiving unit is set to have a length in the sub-scanning direction larger than a length in the main scanning direction,
The light from the document is formed on the light receiving unit without intermediate image formation between the first free curved surface and the second free curved surface, and the imaging magnification in the main scanning direction is An imaging apparatus having a high imaging magnification in the sub-scanning direction. A diaphragm member that restricts and squeezes light from the first free curved surface to the second free curved surface;
The diaphragm member is set to be shorter in the main scanning direction than the first free curved surface of the first reflecting member and the second free curved surface of the second reflecting member, and the first free curved surface is a flat surface. The imaging apparatus according to claim 1 , further comprising a third reflecting member that reflects the light reflected by the light toward the second free-form surface. A light irradiation means for irradiating the document with light;
An imaging apparatus according to claim 1 or 2 ,
An image reading apparatus comprising: a moving unit that moves a relative position between the original and the imaging device in a sub-scanning direction.

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