JP2015081923A - Imaging optical element, print head, image reading device, and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an imaging optical element that can be integrally molded and is easily adjustable for optical characteristics.SOLUTION: The imaging optical element includes a first imaging plane array 11, a prism array 12, a reflection surface 13, and a second imaging plane array 14. A normal line on a plane top of a plurality of imaging planes constituting the first imaging plane array, a normal line on a plane including ridge lines of a plurality of prisms constituting the prism array 12, a normal line on the reflection surface 13, and a normal line on a plane top of a plurality of imaging planes constituting the second imaging plane array, are defined as a first normal line, a second normal line, a third normal line, and a fourth normal line, respectively; and a direction of each normal line from the imaging optical element to the outside is defined as a positive direction. An angle α formed by the positive direction of the first normal line and the positive direction of the third normal line is an acute angle; and an angle β formed by the positive direction of the second normal line and the fourth normal line is an acute angle.

Description

  The present invention relates to an imaging optical element, a print head having the imaging optical element, an image forming apparatus having the imaging optical element, and an image reading apparatus having the imaging optical element.

  As one of the print head optical systems, an optical system configured using a lens array and a roof prism array or a roof mirror array is known (see, for example, Patent Documents 1 to 5).

  Generally, since the depth of the print head is as narrow as about 100 μm, the accuracy required for the optical system is increased. As a result, the print head often requires an adjustment mechanism particularly in the optical axis direction of the lens.

  In addition, since the depth of the print head is narrow, the accuracy required for the temporal stability of the optical system is increased. For this reason, it is desirable that the lens array and the roof prism array or the roof mirror array constituting the print head optical system are integrally formed.

  For example, Patent Literature 1, Patent Literature 2, Patent Literature 4, and Patent Literature 5 disclose that an imaging element having two lens arrays and a prism array is integrally formed.

  However, in the techniques disclosed in Patent Document 1, Patent Document 2, Patent Document 4, and Patent Document 5, the incident light and the emitted light are not parallel. For this reason, in these techniques, for example, if adjustment of the optical axis direction of the imaging element is performed with respect to incident light, the position of the emitted light is shifted, and thus it is difficult to adjust the position of the lens.

  That is, in order to facilitate the adjustment of the optical axis direction of the imaging optical element, it is desirable that the incident light and the emitted light are parallel (or substantially parallel).

  For example, Patent Documents 3 and 5 disclose configurations using a roof mirror array, a lens array, and a reflection mirror.

  However, in the configurations disclosed in Patent Document 3 and Patent Document 5, when the optical axis direction adjustment of the lens is performed, the position of the emitted light is shifted, so that it is difficult to adjust the position of the lens. Further, with the configurations disclosed in Patent Document 3 and Patent Document 5, it is difficult to integrally mold the optical system.

  Patent Document 6 discloses a configuration in which a lens array, a prism array, and a reflecting surface are realized by a single optical element.

  Here, in the configuration disclosed in Patent Document 6, the optical position adjustment is easy because the direction of the incident light and the direction of the outgoing light substantially coincide.

  However, in the configuration disclosed in Patent Document 6, the angle between the incident side lens array surface and the output side lens array surface and the prism array surface is 90 degrees, and the configuration of the reflecting surface is simple. It cannot be molded with a shaped mold.

  That is, in the configuration disclosed in Patent Document 6, the accuracy of the optical element is not obtained, and there is a risk of increasing the cost due to the complicated mold configuration.

Further, although a gradient index lens array is known as an optical system for a print head, it cannot be applied to a high-speed machine because the light utilization efficiency is not sufficient. In particular, when organic EL (Electro-Luminescence) is used as the light source of the print head, the amount of light of the organic EL is LED (Light
Therefore, an optical system having higher light utilization efficiency is required.

  An object of the present invention is to provide an imaging optical element that can be integrally molded and that can easily adjust optical characteristics.

  The present invention is an imaging optical element that includes a first imaging plane array, a prism array, a reflecting surface, and a second imaging plane array, and the first imaging plane array includes a plurality of first imaging plane arrays. The imaging planes are arranged, and the prism array is configured by arranging a plurality of prisms in the same direction as the arrangement direction of the plurality of imaging planes constituting the first imaging plane array. The surface array is formed by arranging a plurality of imaging planes in the same direction as the arrangement direction of the plurality of imaging planes constituting the first imaging plane array, and a plurality of imaging forming the first imaging plane array. The normal line at the surface vertex of the surface is the first normal line, the normal line in the plane including the ridge lines of the plurality of prisms constituting the prism array is the second normal line, the normal line of the reflecting surface is the third normal line, The normal line at the surface vertices of the plurality of image planes constituting the two image plane array is defined as the fourth normal line, and the first normal line and the second normal line The angle formed by the positive direction of the first normal line and the positive direction of the third normal line when the direction from the imaging optical element to the outside is positive with respect to the line, the third normal line, and the fourth normal line Is an acute angle, and the angle formed between the positive direction of the second normal and the positive direction of the fourth normal is an acute angle.

  According to the present invention, integral molding is possible and the optical characteristics can be easily adjusted.

1 is a perspective view showing an embodiment of an imaging optical element according to the present invention. It is a schematic block diagram which shows the prism of the prism array of the said imaging optical element. It is XZ sectional drawing of the said imaging optical element. It is sectional drawing in the dashed-dotted line B of FIG. 3 of the said imaging optical element. It is sectional drawing corresponding to FIG. 3 in the imaging optical element of a reference example. It is XZ sectional drawing which shows the normal line direction of the surface which comprises the said imaging optical element. It is a schematic block diagram which shows the said imaging optical element and a metal mold | die. It is a schematic diagram which shows the optical position adjustment in the imaging optical element of another reference example. It is a schematic diagram which shows the optical position adjustment in the said imaging optical element. It is XZ sectional drawing which shows another embodiment of the imaging optical element which concerns on this invention. It is XZ sectional drawing which shows another embodiment of the imaging optical element which concerns on this invention. It is XZ sectional drawing which shows another embodiment of the imaging optical element which concerns on this invention. It is XZ sectional drawing which shows another embodiment of the imaging optical element which concerns on this invention. It is XZ sectional drawing which shows another embodiment of the imaging optical element which concerns on this invention. It is XZ sectional drawing which shows embodiment of the print head based on this invention. 1 is an XZ sectional view showing an embodiment of an image reading apparatus according to the present invention. 1 is a configuration diagram showing an embodiment of an image forming apparatus according to the present invention.

  Embodiments of an imaging optical element according to the present invention, a print head having the imaging optical element, an image forming apparatus having the imaging optical element, and an image reading apparatus having the imaging optical element are described below. Will be described with reference to the drawings.

● Imaging optics ●
First, an embodiment of an imaging optical element according to the present invention will be described.

  FIG. 1 is a perspective view showing an embodiment of an imaging optical element according to the present invention. As shown in the figure, the imaging optical element 10 is formed by integrally molding a translucent resin, and includes a first imaging surface array 11, a prism array 12, a reflecting surface 13, and a second imaging surface. The array 14 and the first rib 15 are provided.

  In the following description, it is assumed that a light source (not shown) is installed outside the first imaging plane array 11 (−X axis direction) in the imaging optical element 10. A light source can also be installed outside the imaging plane array 14 (+ X axis direction).

  The first imaging plane array 11 is configured by arranging a plurality of imaging planes 11a in an array in a one-dimensional direction (longitudinal direction of the imaging optical element 10).

  FIG. 2 is a schematic configuration diagram showing the prisms 12 a of the prism array 12 of the imaging optical element 10. As shown in the figure, the prism array 12 has an array of prisms 12a corresponding to the imaging plane 11a of the first imaging plane array 11 in the same direction (one-dimensional direction) as the arrangement direction of the imaging plane 11a. Arranged. The prism 12a has an apex angle between the prism surface 12a1 and the prism surface 12a2, for example, 90 degrees.

  Here, in the following description, the arrangement direction (one-dimensional direction) of the imaging plane 11a of the first imaging plane array 11, the plurality of prisms 12a, and the imaging plane 14a of the second imaging plane array 14 is the Y-axis direction. The direction of the first normal line is the X-axis direction, and the direction orthogonal to the X-axis direction and the Y-axis direction is the Z-axis direction.

  Returning to FIG. The reflection surface 13 is configured by a mirror reflection surface in which a highly reflective member such as an aluminum vapor deposition layer is provided on the total reflection surface or the surface of the imaging optical element 10.

  The second imaging plane array 14 is configured by arranging a plurality of imaging planes 14a in an one-dimensional direction.

  The first rib 15 is provided on the longitudinal side surface (Y-axis direction side portion) of the first imaging plane array 11. Here, the first rib 15 extends outward from the first image plane array 11. That is, the end of the first rib 15 in the −X-axis direction is more than the surface vertex of the imaging plane of the first imaging plane array 11 when the direction toward the inside of the imaging optical element 10 is the + X-axis direction. Located in the X-axis direction.

  The first rib 15 has a portion that overlaps at least a part of the prism array 12 when viewed from the Z-axis direction, and extends outward from the prism array 12. That is, the end of the first rib 15 in the + X-axis direction is positioned in the + X-axis direction than the end of the prism array 12 in the + X-axis direction.

  By providing the first rib 15, the imaging optical element 10 can increase the strength of the imaging optical element 10 while maintaining the ease of integral molding.

  Further, by providing the first rib 15, in the imaging optical element 10, the ease of handling (handling property) of the imaging optical element 10 can be improved.

  Further, the first rib 15 can be used for fixing the imaging optical element 10 to other parts such as a housing (not shown).

  FIG. 3 is an XZ sectional view of the imaging optical element 10. As shown in the figure, in the imaging optical element 10, the first imaging plane array 11 and the second imaging plane array 14 are provided in parallel. In the imaging optical element 10, the prism array 12 and the reflecting surface 13 are provided so as to be inclined by 45 degrees with respect to the first imaging surface array 11.

  4 is a cross-sectional view of the imaging optical element 10 taken along the alternate long and short dash line B in FIG. 3 is a cross-sectional view of the imaging optical element 10 passing through the one-dot chain line B of FIG. 3 and parallel to the Y-axis direction, and the prism array 12 and the reflecting surface 13 are bent 90 degrees.

  In FIG. 4, in order to facilitate understanding of the configuration of the imaging optical element 10, the incident portion and the emission portion of the prism array 12 are divided into two parts.

  Here, with reference to FIG. 4, in the imaging optical element 10, the first imaging plane array 11, the prism array 12, the reflecting plane 13, and the second imaging plane array 14 in the light traveling direction (+ X axis direction). The distance between is described.

  The distance La between the first image plane array 11 and the prism array 12 is the distance Lb between the prism array 12 and the reflection surface 13 and the distance Lc between the reflection surface 13 and the second image plane array 14. Is equal to the sum of

  With this configuration, the imaging optical element 10 can improve imaging performance.

  As shown in FIG. 4, the arrangement pitch of the first imaging plane array 11 and the second imaging plane array 14 is set to the same 0.8 mm. By making both arrangement pitches the same, the first imaging plane array 11 and the second imaging plane array 14 are configured such that there is no light phase shift in the Y-axis direction.

  Here, the arrangement pitch of the prisms 12 a of the prism array 12 is set to 0.1 mm, which is smaller than the arrangement pitch of the first imaging plane array 11 and the second imaging plane array 14.

  The manner in which the light incident on the imaging optical element 10 forms an image will be described with reference to FIGS.

  3 and 4, it is assumed that the light source is located at a position F1 that is a predetermined distance away from the first imaging plane array 11.

  As shown in FIG. 3, the light emitted from the light source at the position F1 enters the imaging plane of the first imaging plane array 11 and becomes parallel light or substantially parallel light. Thereafter, the light propagates through the imaging optical element 10 and enters the prism array 12.

  As shown in FIG. 4, the light incident on the prism array 12 is totally reflected twice by the prism surfaces 12 a 1 and 12 a 2 of the prism 12 a having an apex angle of 90 degrees and is emitted from the prism array 12.

  Here, the incident angle to the prism array 12 and the exit angle from the prism array 12 are both the angle θ in the Y-axis direction. That is, the prism array 12 is a so-called retroreflective optical system.

  The light emitted from the prism array 12 is totally reflected or mirror-reflected by the reflecting surface 13 and then emitted from the image forming surface 14 a of the second image forming surface array 14.

  Here, the light emitted from the imaging surface 14a of the second imaging surface array 14 includes substantially one point at the position F2, including the light imaged at the position F2 and the light reaching the position in the vicinity thereof. It is assumed that the image is formed.

  As described above, the imaging optical element 10 can form an erect image in the arrangement direction by the retroreflection function of the prism array 12.

  That is, according to the imaging optical element 10, the light emitted from the predetermined position F1 on the object plane is passed through the first imaging plane array 11, the prism array 12, the reflecting surface 13, and the second imaging plane array 14. It is possible to pass through and form an image at a predetermined position F2.

Reference Example Next, the arrangement pitch of the first imaging plane array 11 and the second imaging plane array 14 of the imaging optical element 10 described above and the prism array 12 will be described using a reference example having the same arrangement pitch. .

  FIG. 5 is a cross-sectional view corresponding to FIG. 3 in the imaging optical element of the reference example. As shown in the figure, in the imaging optical element 10A of the reference example, the arrangement pitch of the prism arrays 12A is equal to the arrangement pitch of the first imaging plane array 11 and the second imaging plane array 14. Other configurations are the same as those of the imaging optical element 10 described above.

  Here, in the same manner as in FIG. 3, let us consider light passing through the virtual surface a at the virtual surface a connecting the end portions in the arrangement direction of the incident surface and the output surface. In this case, the light passes through the imaging plane 11a of the first imaging plane array 11 and enters the prism array 12A.

  The light incident on the prism array 12A is emitted from the prism array 12A so as to be directed toward the virtual plane a by the retroreflection function of the prism array 12A.

  Here, the prism array 12A has a large light shift amount in the Y-axis direction. For this reason, the light emitted from the prism array 12 does not pass through the virtual surface a again, and is different from the image forming surface 11a on which the light is incident from the image forming surface 14a that is different in position in the Y-axis direction (not paired). It will be emitted.

  That is, in the imaging optical element 10A of the reference example, so-called ghost light G that does not form an image at a desired position F2 is generated.

  In order to reduce the ghost light G as described above, the prism array 12 has a pitch larger than the arrangement pitch of the first imaging plane array 11 and the second imaging plane array 14 as in the imaging optical element 10 described above. It is effective to reduce the arrangement pitch.

  Returning to FIG. In the imaging optical element 10, let us consider light passing through the virtual surface a at the virtual surface a connecting the end portions in the arrangement direction of the entrance surface and the exit surface. In this case, since the arrangement pitch of the prisms 12a of the prism array 12 is reduced, the deviation of the light beam position in the Y-axis direction in the prism array 12 can be reduced.

  That is, the light emitted from the prism array 12 passes through the virtual plane a again, and passes through the imaging plane 14a in which the position in the Y-axis direction corresponds to (a pair of) the imaging plane 11a on which the light is incident. Can be made.

  As described above, according to the imaging optical element 10, it is possible to form an image at the desired position F2 without generating ghost light unlike the imaging optical element 10A of the reference example.

  Therefore, according to the imaging optical element 10, it is possible to form a bright image by reducing the loss of light by configuring the retroreflective optical system in the Y-axis direction.

  Next, the normal direction of the surfaces constituting the imaging optical element 10 will be described.

  FIG. 6 is an XZ sectional view showing the normal direction of the surface constituting the imaging optical element 10. As shown in the figure, in the imaging optical element 10, the normal line of the surface vertex of the imaging plane 11a of the first imaging plane array 11 is defined as a first normal line N1. Here, the light that passes through the surface vertex of the imaging surface 11a and enters in parallel with the first normal line N1 passes through the prism array 12, the reflecting surface 13, and the second imaging surface array 14 in this order.

  Further, a normal line in a plane including the ridge lines of the plurality of prisms constituting the prism array 12 is set as a second normal line N2.

  The normal line of the reflecting surface 13 (line extending vertically from the reflecting surface 13) is defined as a third normal line N3, and the normal line of the surface vertex of the image plane 14a of the second image plane array 14 is defined as a fourth normal line N4. And

  In addition, about the 1st normal line N1-the 4th normal line N4, let the direction which goes outside from each surface be a positive direction.

  Here, in the imaging optical element 10, the angle α formed by the positive direction of the first normal line N1 and the positive direction of the third normal line N3 is an acute angle. In the imaging optical element 10, the angle β formed by the positive direction of the second normal line N2 and the positive direction of the fourth normal line N4 is an acute angle.

  FIG. 7 is a schematic configuration diagram showing the imaging optical element 10 and a mold. In the figure, an example in which the imaging optical element 10 is molded using a mold 101 and a mold 102 is shown.

  In general, in order to mold a resin product with high accuracy and low cost, a mold configuration in which two molds are opened in two different directions (preferably two opposite directions) may be employed.

  That is, in order to realize resin molding of the imaging optical element 10 with such a mold configuration, the angle α formed by the first normal line N1 and the third normal line N3 is an angle greater than 0 degree and less than 80 degrees. You can do it.

  Further, the angle β formed by the second normal line N2 and the fourth normal line N4 may be an angle larger than 0 degree and smaller than 80 degrees.

  Here, when the imaging optical element 10 is resin-molded using a mold, the angle formed by the first normal line N1 and the fourth normal line N4 is substantially 180 degrees (the first normal line N1 and the first normal line N1). It is desirable that the fourth normal line N4 is substantially parallel to the fourth normal line N4.

  Here, substantially 180 degrees means including 180 degrees and a difference in angle at which the imaging optical element 10 can be molded using the above-described mold configuration.

  For example, when the formed angle α or the formed angle β is in the vicinity of 90 degrees, it is impossible to mold with a mold configuration that opens in two directions as shown in FIG. 7, so a mold configuration that opens in three directions is necessary, for example. become. In this case, there is a problem that the accuracy of the mold is lowered or the mold configuration is complicated and the cost is increased.

  Further, when the formed angle α or the formed angle β is 80 degrees or more and less than 90 degrees, it is possible to mold with a mold configuration that opens in two directions as shown in FIG. Since the angle difference from 13 becomes too large, it is difficult to obtain the accuracy of the reflecting surface 13.

  In this case, in order to improve the accuracy of the reflecting surface 13, the angle α and the angle β formed as described above may be made smaller than 80 degrees. In order to further improve the accuracy of the reflecting surface 13, it is desirable to make the angle α and the angle β formed smaller than 50 degrees.

  Next, the reason why the angle formed by the first normal line N1 and the fourth normal line N4 is preferably substantially 180 degrees will be described.

  Here, it is considered to adjust the position of the imaging optical element 10 in the optical axis direction in order to adjust the focus position shift due to the processing error or the installation error of the imaging optical element 10.

  FIG. 8 is a schematic diagram showing optical position adjustment in an imaging optical element of another reference example. As shown in the drawing, in the imaging optical element 10B of another reference example, the angle formed by the first normal line and the fourth normal line is 90 degrees. In the figure, O represents the object plane, and I represents the image plane.

  FIG. 8A shows a state before the optical position adjustment of the imaging optical element 10B, and the position of F2B with respect to the image plane I (hereinafter referred to as “focus position”) due to the influence of processing errors and installation errors. It's off. FIG. 8B shows a state after the optical position adjustment of the imaging optical element 10B, and the position of the imaging optical element 10B in the X-axis direction is moved so that the image plane I is in focus. I am letting.

  As shown in FIG. 8, in the imaging optical element 10B, although the focus position can be adjusted by adjusting the position of the first imaging plane array 11B, the image plane I is adjusted together with the position of the second imaging plane array 14B. The upper imaging position is shifted in the X-axis direction. That is, in the imaging optical element 10B, the position on the image plane I shifts when adjusting the focus position, and it is very difficult to adjust the optical characteristics such as position adjustment.

  FIG. 9 is a schematic diagram showing optical position adjustment in the imaging optical element 10. As shown in the figure, in the imaging optical element 10, the angle formed by the first normal line and the fourth normal line is substantially 180 degrees as described above. In the figure, O represents the object plane, and I represents the image plane.

  FIG. 9A shows a state before the optical position adjustment of the imaging optical element 10, and the focus position is deviated from the image plane I due to the influence of processing errors and installation errors. FIG. 9B shows a state after the optical position adjustment of the imaging optical element 10, and the position of the imaging optical element 10 in the X-axis direction is moved so that the image plane I is in focus. I am letting.

  As shown in FIG. 9, in the imaging optical element 10, since the angle formed by the first normal line and the fourth normal line is substantially 180 degrees, the first image plane array 11 and the second image plane are formed. The direction of optical misalignment with the array 14 matches.

  Therefore, in the imaging optical element 10, since only the focus position can be adjusted on the image plane I in the optical axis direction, the light beam position is difficult to shift in other directions (Y-axis direction and Z-axis direction). Adjustment of optical characteristics such as position adjustment can be performed very easily.

  The angle formed between the second normal line N2 and the third normal line N3 is substantially 180 degrees (the second normal line N2 and the third normal line N3 are substantially parallel). desirable. With this configuration, the imaging optical element 10 can ensure good imaging performance.

● Imaging optical element (2) ●
Next, another embodiment of the imaging optical element according to the present invention will be described focusing on differences from the previously described embodiments.

  FIG. 10 is an XZ sectional view showing another embodiment of the imaging optical element according to the present invention. As shown in the figure, the imaging optical element 10C according to the present embodiment has the second rib 16 on the side surface between the first imaging plane array 11 and the reflecting surface 13 as described above. Different from the imaging optical element 10.

  Here, the second rib 16 can be configured to protrude in the −X-axis direction from the surface vertex of the imaging plane 11 a of the first imaging plane array 11.

  With this configuration, the imaging optical element 10C can protect the first imaging plane array 11 better than the case where only the first ribs 15 are provided.

● Imaging optical element (3) ●
Next, still another embodiment of the imaging optical element according to the present invention will be described focusing on differences from the previously described embodiments.

  FIG. 11 is an XZ cross-sectional view showing still another embodiment of the imaging optical element according to the present invention. As shown in the figure, the imaging optical element 10D according to the present embodiment has the third rib 17 between the prism array 12 and the second imaging plane array 14, and the imaging described above. It is different from the optical elements 10 and 10C.

  Here, the third rib 17 can be configured to protrude in the + X-axis direction from the surface vertex of the image plane 14 a of the second image plane array 14.

  With this configuration, the imaging optical element 10 </ b> D can protect the second imaging plane array 14 in addition to the first imaging plane array 11 and the prism array 12.

● Imaging optical element (4) ●
Next, still another embodiment of the imaging optical element according to the present invention will be described focusing on differences from the previously described embodiments.

  FIG. 12 is an XZ cross-sectional view showing still another embodiment of the imaging optical element according to the present invention. As shown in the figure, the imaging optical element 10E according to the present embodiment has the fourth rib 18 on the side surface on the outer side in the + Z-axis direction of the second imaging plane array 14 as described above. It is different from the optical elements 10, 10C, 10D.

  Here, the fourth rib 18 can be configured to protrude in the + X-axis direction from the surface vertex of the image plane 14 a of the second image plane array 14.

  With this configuration, the imaging optical element 10E can protect the second imaging plane array 14 better than when only the third ribs 17 are provided.

● Imaging optical element (5) ●
Next, still another embodiment of the imaging optical element according to the present invention will be described focusing on differences from the previously described embodiments.

  FIG. 13 is an XZ cross-sectional view showing still another embodiment of the imaging optical element according to the present invention. As shown in the figure, the imaging optical element 10F according to the present embodiment has a width Wpi in the Z-axis direction of the prism array 12F, and a width Wi in the Z-axis direction of the imaging surface of the first imaging surface array 11F. Narrower than.

  In general, in an imaging plane array, an end portion of an arbitrary imaging plane is liable to generate a shape error for the convenience of manufacturing, and thus may adversely affect imaging performance. In order to avoid such a risk, an aperture (not shown) is provided in front of the first imaging plane array (light source side) that is the incident surface to block light near the end of the incident surface in the Z-axis direction. It is possible.

  However, if an aperture is provided, one part is added, resulting in an increase in cost and an accurate alignment between the incident surface and the aperture.

  Further, when the aperture is provided, the aperture has a slit shape elongated in the Y-axis direction, so that not only processing is difficult but also strength is reduced. That is, it is not preferable to provide an aperture from the viewpoint of misalignment when vibration occurs.

  Therefore, in the imaging optical element 10F, the prism array 12F functions as an aperture by making the width Wpi of the prism array 12F in the Z-axis direction smaller than the width Wi of the imaging surface of the first imaging surface array 11. Can do.

  Here, in the imaging optical element 10F, by setting Wi> Wpi, only a part of the light that has passed through the incident surface can be incident on the prism array 12F. That is, in the imaging optical element 10F, by setting Wi> Wpi, it is possible to avoid the light passing through the end portion in the Z-axis direction of the incident surface from reaching the image surface, so that the imaging performance is deteriorated. Can be avoided.

  Further, according to the imaging optical element 10F, the first imaging plane array 11F and the prism array 12F that realize the aperture function are integrally molded, so that each part is integrally molded, so that the strength is weakened. Therefore, there is no displacement due to vibration.

  Therefore, according to the imaging optical element 10F, the positional accuracy of the first imaging plane array 11F and the prism array 12F that realize the aperture function can be realized with high accuracy.

● Imaging optical element (6) ●
Next, still another embodiment of the imaging optical element according to the present invention will be described focusing on differences from the previously described embodiments.

  FIG. 14 is an XZ cross-sectional view showing still another embodiment of the imaging optical element according to the present invention. As shown in the figure, in the imaging optical element 10G according to the present embodiment, the width Wr in the Z-axis direction of the reflecting surface 13 is the width Wi in the Z-axis direction of the imaging surface of the first imaging surface array 11G. Narrower than.

  That is, in the imaging optical element 10G, the reflecting surface 13 functions as an aperture by making the width Wr of the reflecting surface 13 in the Z-axis direction smaller than the imaging surface width Wi of the first imaging surface array 11. Can do.

  Here, in the imaging optical element 10G, by setting Wi> Wr, only part of the light that has passed through the incident surface can be incident on the reflecting surface 13G. In other words, in the imaging optical element 10G, by setting Wi> Wr, it is possible to avoid the light passing through the Z-axis direction end portion of the incident surface from reaching the image surface, so that the imaging performance is deteriorated. Can be avoided.

  Further, according to the imaging optical element 10G, since the first imaging surface array 11G that realizes the aperture function and the reflecting surface 13G are integrally molded, the strength is not weakened. Does not occur.

  Therefore, according to the imaging optical element 10G, the positional accuracy between the first imaging surface array 11G and the reflecting surface 13G that realize the aperture function can be realized with high accuracy.

● Print head (1) ●
Next, an embodiment of a print head according to the present invention will be described.

  FIG. 15 is an XZ sectional view showing an embodiment of a print head according to the present invention. As shown in the figure, the print head 30 includes a light source array 31 having light sources arranged in at least one line, an imaging optical element 10 on which light from the light source is incident, and a housing 32.

  The light source array 31 has light sources arranged in the arrangement direction (Y-axis direction) of the first imaging plane array 11. The light source array 31 is held on the substrate 31a.

  Here, an LED, an organic EL, or the like can be used as the light source. The light source array 31 can also be arranged in a plurality of rows in the direction orthogonal to the arrangement of the first image plane array 11 (Z-axis direction).

  The housing 32 holds the substrate 31 a that holds the light source array 31 and the imaging optical element 10.

  The substrate 31a and the imaging optical element 10 are held in the same housing 32, but may be held by different members.

  Here, the imaging optical element 10 is the imaging optical element according to the present invention described above. The imaging optical element 10 is attached to the housing 32 via the first rib 15.

  Various methods such as springs and adhesion may be adopted as the method of attaching the imaging optical element 10 to the housing 32. In this embodiment, adhesion using UV (Ultra-Violet) curable resin is performed. ing.

  Before the bonding with the UV curable resin, the position of the imaging optical element 10 in the X-axis direction is adjusted so that the image plane I is the focus position of the second imaging plane array 14.

  In addition to the imaging optical element 10, the imaging optical elements 10C, 10D, 10E, 10F, and 10G described above can be used for the print head 30.

  As described above, according to the print head 30, the imaging optical element 10 can be integrally molded, and the optical adjustment of the imaging optical element 10 can be facilitated.

  And according to the print head 30, since the light quantity emitted by the light source array 31 can be kept small by using the imaging optical element 10 with high light utilization efficiency, heat generation and power consumption can be reduced.

● Image reading device ●
Next, an embodiment of an image reading apparatus according to the present invention will be described.

  FIG. 16 is an XZ sectional view showing an embodiment of an image reading apparatus according to the present invention. As shown in the figure, in the present embodiment, the image reading section 40 is attached to the housing 32 with the light receiver array 33 held by a substrate 33a.

  Here, the image reading unit 40 is used in the image reading apparatus according to the present invention.

  As described above, according to the image reading unit 40, the imaging optical element 10 can be integrally molded, and the optical adjustment of the imaging optical element 10 can be facilitated.

  As a result, since the imaging optical element 10 used in the image reading unit 40 can achieve high light utilization efficiency, the amount of light received on the light receiver array 33 can be increased. That is, according to the image reading unit 40, since the S / N (Signal / Noise) ratio at the time of image reading can be improved, the read image quality can be improved.

● Image forming device ●
Next, an embodiment of the image forming apparatus according to the present invention will be described.

  FIG. 17 is a configuration diagram showing an embodiment of an image forming apparatus according to the present invention. FIG. 1 shows the configuration of an image forming apparatus 50 that forms a multicolor image as an example of the image forming apparatus according to the present invention.

  In FIG. 17, an image forming apparatus 50 includes a photoconductor 51 (51Y, 51M, 51C, 51K) as an image carrier, a charger 52 (52Y, 52M, 52C, 52K), and a print as an optical writing unit. And a head 30 (30Y, 30M, 30C, 30K).

  The image forming apparatus 50 includes a developing device 54 (54Y, 54M, 54C, 54K), a cleaning unit 55 (55Y, 55M, 55C, 55K), and a transfer charging unit 56 (56Y, 56M, 56C, 56K). And a transfer belt 57 and a fixing unit 58.

  Y, M, C, and K represent image colors, and indicate yellow, magenta, cyan, and black, respectively.

  The photoreceptor 51 is an image plane formed by the print head 30 according to the present invention described above.

  In the image forming apparatus 50, the photoconductors 51Y, 51M, 51C, and 51K rotate in the direction of the arrow. In this rotational direction, chargers 52Y, 52M, 52C, and 52K, developing devices 54Y, 54M, 54C, and 54K, transfer charging means 56Y, 56M, 56C, and 56K, and cleaning means 55Y, 55M, 55C, and 55K are arranged. ing.

  The chargers 52Y, 52M, 52C, and 52K are charging members that constitute a charging device for uniformly charging the surface of the photoreceptor. After charging the photoconductors 51Y, 51M, 51C, and 51K with a charging member, electrostatic latent images (electrostatic images) are exposed by the print heads 30Y, 30M, 30C, and 30K according to the present invention used as an exposure apparatus. To form.

  In the image forming apparatus 50, based on the electrostatic latent image, a toner image is formed on the photoreceptor surface by the developing member. That is, the electrostatic latent image by each toner is visualized. Further, the color toner images are transferred onto the transfer belt 57 by the transfer charging units 56Y, 56M, 56C, and 56K.

  As a result, in the image forming apparatus 50, the color toner images are superimposed on the transfer belt. Subsequently, in the image forming apparatus 50, the superimposed color toner images are collectively transferred to a recording medium (not shown) (for example, recording paper), and finally the image is fixed on the recording paper by the fixing unit 58.

  As described above, the print head 30 has high light utilization efficiency and suppresses the generation of ghost light.

  Therefore, the image forming apparatus 50 can output a stable image with no abnormal image while reducing power consumption.

10 imaging optical element 11 first imaging plane array 12 prism array 12a1 prism surface 12a2 prism surface 13 reflecting surface 14 second imaging plane array 15 first rib 16 second rib 17 third rib 18 fourth rib 30 print head Reference Signs List 31 Light Source Array 32 Housing 33 Photoreceiver Array 40 Image Reading Unit 50 Image Forming Device 51 Photoreceptor 52 Charger 54 Developer 55 Cleaning Unit 56 Transfer Charging Unit 57 Transfer Belt 58 Fixing Unit 101 Mold 102 Mold

JP 2000-108405 A JP 2000-108403 A Japanese Patent Laid-Open No. 04-336559 JP-A-63-225218 Japanese Patent Laid-Open No. 10-153751 Japanese Patent Laid-Open No. 06-250119

Claims (13)

A first imaging plane array;
A prism array;
A reflective surface;
A second imaging plane array;
An imaging optical element comprising:
The first imaging plane array is configured by arranging a plurality of imaging planes,
The prism array is configured by arranging a plurality of prisms in the same direction as an arrangement direction of a plurality of imaging planes constituting the first imaging plane array.
The second imaging plane array is configured by arranging a plurality of imaging planes in the same direction as the arrangement direction of the plurality of imaging planes constituting the first imaging plane array,
A normal line at a surface vertex of a plurality of image planes constituting the first image plane array is defined as a first normal line,
A normal line in a plane including ridge lines of a plurality of prisms constituting the prism array is defined as a second normal line,
The normal of the reflecting surface is the third normal,
The normal line at the surface vertex of the plurality of image planes constituting the second image plane array is a fourth normal line,
About the first normal line, the second normal line, the third normal line, and the fourth normal line, when the direction from the imaging optical element to the outside is a positive direction,
The angle formed between the positive direction of the first normal line and the positive direction of the third normal line is an acute angle,
The angle formed by the positive direction of the second normal line and the positive direction of the fourth normal line is an acute angle.
An imaging optical element characterized by the above. The first normal line and the fourth normal line are parallel to each other.
The imaging optical element according to claim 1. Light rays that pass through the surface vertices of the plurality of imaging planes constituting the first imaging plane array and are incident in parallel to the first normal line are reflected by the prism array, the reflection plane, and the second imaging plane array. Pass in order,
The imaging optical element according to claim 1 or 2. The distance between the first imaging plane array and the prism array in the traveling direction of the light beam is the distance between the prism array and the reflecting surface in the traveling direction of the light beam and the distance in the traveling direction of the light beam. Equal to the sum of the distance between the reflective surface and the second imaging plane array;
The imaging optical element according to claim 3. Having a rib on a longitudinal side surface of the first imaging plane array;
The imaging optical element according to claim 1. The arrangement direction of the prisms is the Y-axis direction, the direction of the first normal is the X-axis direction, and the direction orthogonal to the X-axis direction and the Y-axis direction is the Z-axis direction,
When the direction toward the inside of the imaging optical element in the direction of the first normal is the + X axis direction,
An end portion of the rib in the X-axis direction is located in a −X-axis direction with respect to a surface vertex of the imaging plane of the first imaging plane array.
The imaging optical element according to claim 5. The rib has a portion overlapping with the prism array or the second imaging plane array when viewed from the Z-axis direction.
The imaging optical element according to claim 6. The width in the Z-axis direction of the prism array is narrower than the width in the Z-axis direction of the imaging plane of the first imaging plane array.
The imaging optical element according to claim 1. The width of the reflecting surface in the Z-axis direction is narrower than the width of the imaging surface of the first imaging surface array in the Z-axis direction.
The imaging optical element according to claim 1. A plurality of imaging planes of the first imaging plane array are arranged corresponding to the prisms,
The arrangement pitch of the prisms is smaller than the arrangement pitch of the imaging planes,
The imaging optical element according to claim 1. A print head comprising: a light source array having light sources arranged in at least one row of lines; and an imaging optical element on which light from the light sources is incident,
11. The print head according to claim 1, wherein the imaging optical element is an imaging optical element according to any one of claims 1 to 10. A printhead;
An image carrier;
Developing means for developing an electrostatic image formed on the image carrier by the print head with each color toner;
Transfer means for transferring an image visualized on the image carrier to a recording medium;
An image forming apparatus comprising:
The image forming apparatus according to claim 11, wherein the print head is a print head according to claim 11. An imaging optical element;
A light receiver array having light receivers arranged in a line of at least one row, comprising:
11. The image reading apparatus according to claim 1, wherein the imaging optical element is an imaging optical element according to any one of claims 1 to 10.

Images