Lens unit, lens unit holder, print head, image sensor head, image forming apparatus, image scanner apparatus

A lens unit according to an embodiment includes: lens members in each of which lenses are linearly arrayed in a longitudinal direction; at least one light block member between the lens members; engagement sections arranged in the longitudinal direction, each of the engagement sections configured to mutually engage members including the lens members and the light block member and stacked with each other; and clamp members disposed in positions corresponding to at least one of the engagement sections in the longitudinal direction and configured to clamp the stacked members. All the stacked members are fixed with each other at only one portion in the longitudinal direction.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority based on 35 USC 119 from prior Japanese Patent Application No. 2016-149975 filed on Jul. 29, 2016, entitled “LENS UNIT, LENS UNIT HOLDER, PRINT HEAD, IMAGE SENSOR HEAD, IMAGE FORMING APPARATUS, IMAGE SCANNER APPARATUS”, the entire contents of which are incorporated herein by reference.

BACKGROUND

The present disclosure relates to a lens unit, a lens unit holder, a print head, an image sensor head, an image forming apparatus, and an image scanner apparatus.

2. Description of the Related Art

In a lens unit of related art, a first lens array manufactured by injection molding and a second lens array manufactured by injection molding using the same mold are disposed such that the second lens array is turned around an axis set in a longitudinal direction of a light block member, and has optical axes alighted with optical axes of the first lens array. The first and second lens arrays and the light block member are stacked such that the light block member is held between the lens arrays. This structure absorbs relative displacement and a shape difference due to contraction and expansion of materials (see, for example, Japanese Patent Application Publication No. 2013-15847).

SUMMARY

However, in the structure explained above, if the components constituting the lens unit are different in linear expansion due to heat and water absorption, the entire lens unit may warp in the lens optical axis direction.

An object of an embodiment is to suppress the warp in the lens optical axis direction.

An aspect of the invention is a lens unit that includes: lens members in each of which lenses are linearly arrayed in a longitudinal direction; at least one light block member between the lens members; engagement sections arranged in the longitudinal direction, each of the engagement sections configured to mutually engage members including the lens members and the light block member and stacked with each other to align with optical axes of the lenses; and clamp members disposed in positions corresponding to at least one of the engagement sections in the longitudinal direction and configured to clamp the stacked members. All the stacked members are fixed with each other at only one portion in the longitudinal direction.

According to the aspect of the invention, it is possible to suppress the warp in the lens optical axis direction.

DETAILED DESCRIPTION OF EMBODIMENTS

One or more embodiments of a lens unit, a lens unit holder, a print head, an image sensor head, an image forming apparatus, and an image scanner apparatus are explained below with reference to the drawings.

First Embodiment

First, a print head included in a printer functioning as an image forming apparatus is explained. Note that the configuration of the printer is explained later.

FIGS. 1A to1D are explanatory diagrams of a print head in a first embodiment.FIG. 1A is a perspective view of the print head.FIG. 1Bis a plan view of the print head.FIG. 1Cis an enlarged view of an attachment part of a lens unit to a holder, which is provided in a longitudinal center portion of the print head.FIG. 1Dis an enlarged view of one of attachment parts of the lens unit to the holder, which are provided at positions other than the longitudinal center portion of the print head.FIG. 2is a sectional view of the print head and is an X-X arrow view inFIGS. 1A to 1D.FIGS. 3A and 3Bare explanatory diagrams of the holder of the print head.FIG. 3Ais a plan view of the holder.FIG. 3Bis an X-X arrow view inFIG. 3A.FIG. 4is a sectional view of the print head and is a Y-Y arrow sectional view inFIG. 1.

Print head101in this embodiment is explained with reference toFIGS. 1A to 4.

InFIGS. 1A to 1D,FIG. 2, andFIG. 4, in order to clearly explain an attachment structure of lens unit102and lens unit holder (hereinafter referred to as “holder”)103, a structure is illustrated in which a silicone sealing material is omitted between lens unit102and holder103. However, in order to prevent foreign matters from intruding into the inside of print head101from a gap section formed between lens unit102and holder103, the silicone sealing material may be disposed between lens unit102and holder103.

As illustrated inFIG. 1, in print head101, lens unit102is fixed (attached) to holder103using adhesives105and107. Lens unit102includes lens cover111, first lens array112, partition wall light block plate113, second lens array114, and incident light block plate115.

As illustrated inFIG. 2, at attachment parts161of lens unit102to holder103at positions other than the longitudinal center portion of print head101illustrated inFIG. 1D, members of lens unit102, which are lens cover111, first lens array112, partition wall light block plate113, second lens array114, and incident light block plate115, are stacked in the direction of optical axis102aof semiconductor light emitting element117, and the stacked members111,112,113,114, and115are champed together by clamp members104provided at both widthwise sides of lens unit102, and lens unit102is attached to holder103via clamp members104. Note that the widthwise direction of the lens unit102is orthogonal to the stacking direction of the members and orthogonal to the longitudinal direction of lens unit102.

Plural pairs of clamp members104are disposed in the longitudinal direction of lens unit102, and each pair of clamp members104clamp all the stacked members from both widthwise sides of the lens unit102. Lens unit102is fixed (attached) to holder103with adhesive105filled in first filling section103aprovided between clamp members104and holder103.

On the other hand, as illustrated inFIG. 4, at attachment part162of lens unit102to holder103at the longitudinal center portion of print head101illustrated inFIG. 10, all the stacked members (lens cover111, first lens array112, partition wall light block plate113, second lens array114, and incident light block plate115) of lens unit102are bonded (fixed) one another with adhesive106filled on both widthwise sides of lens unit102. Further, at the attachment part of lens unit102to holder103at the longitudinal center portion of print head101, adhesive107is filled in second filling section103b(see,FIG. 4) between the bonding part of lens unit102and lens holder103such that adhesive107is in direct contact with at least one of the stacked members (lens cover111, first lens array112, partition wall light block plate113, second lens array114, and incident light block plate115) of lens unit102, thereby lens unit102is fixed (attached) to lens holder103via adhesive107at the longitudinal center portion of print head101.

That is, in this embodiment, in attachment part162at the longitudinal center portion, the stacked members(lens cover111, first lens array112, partition wall light block plate113, second lens array114, and incident light block plate115) of lens unit102are bonded to one another with adhesive106filled in both widthwise sides of lens unit102.

In this way, all the stacked members are fixed (bonded) together by the adhesive at attachment part162at the longitudinal center portion of lens unit102(the attachment part in which clamp members104are not disposed). Further, lens unit102is fixed (attached) to holder103at attachment part162at the longitudinal center portion of lens unit102.

Note that, as illustrated inFIGS. 1A and 1B, round hole108aand long hole108bare provided at both longitudinal end portions of print head101, which are to be fit with protrusions provided at a printer body to position print head101with respect to the printer body.

Contact sections109aand109bare provided near both longitudinal end portions of print head101. Contact sections109aand109bare to be in contact with contact sections of the printer body to be positioned such that distance Li between latent image surface308aof a photosensitive drum and an upper surface extreme point of first lens array112in the direction of lens optical axis102aillustrated inFIG. 2is a designed optical distance.

Note that, an eccentric cam mechanism may be provided in contact sections109aand109b, to adjust distance Li to be the optical designed distance.

As illustrated inFIGS. 3A and 3B, lens unit102is fixed to holder103by bonding adhesive105to holder103via clamp members104in slit section110on the upper surface of holder103.

As illustrated inFIG. 2, the attachment height of lens unit102with respect to holder103is adjusted such that distance Lo between the surfaces of semiconductor light emitting elements117linearly arrayed in the longitudinal direction on printed wiring board116and a lower surface extreme point of second lens array114in lens unit102is a designed optical distance.

Next, lens unit102is explained. Lens unit102includes lens cover111, first lens array112, partition wall light block plate113, second lens array114, and incident light block plate115stacked in this order from latent image surface308aside of the photosensitive drum. Lens cover111protects lens unit102.

First lens array112and second lens array114functioning as lens members are tabular lens arrays in which micro-lenses are linearly arrayed in the longitudinal direction. First lens array112and second lens array114are disposed such that optical axes of the micro-lenses are aligned. First lens array112and second lens array114form an image of semiconductor light emitting elements117as an erected non-magnification image on latent image surface308aof the photosensitive drum according to a combination of the micro-lenses.

Partition wall light block plate113functioning as a light block member is disposed between first lens array112and second lens array114. Partition wall light block plate113is a tabular plate in which an opening section functioning as a diaphragm is formed be aligned with the optical axes of the micro-lenses. Partition wall light block plate113blocks a stray light component in a ray emitted from second lens array114in the direction of first lens array112and secures a clearance (an interval) between first lens array112and second lens array114.

Incident light block plate115blocks a stray light component made incident on second lens array114from semiconductor light emitting elements117.

Members of lens cover111, first lens array112, partition wall light block plate113, second lens array114, and incident light block plate115are engaged with one another by being clamped with clamp members104.

Printed wiring board116mounted with semiconductor light emitting elements117is positioned by setting board contact section118illustrated inFIG. 3Band the surface of printed wiring board116in contact with each other such that distance Lo between the surface of semiconductor light emitting elements117and the lower surface extreme point of second lens array114in lens unit102is the designed optical distance.

Printed wiring board116is held and fixed to board contact section118provided on holder103side by engaging base clamp member119illustrated inFIG. 2in clamp hole120provided on a side surface of holder103.

At the longitudinal center portion of lens unit102, as illustrated inFIG. 4, at least one of adhesive106and the stacked members (111to115) of lens unit102are directly fixed (attached) to holder103by adhesive107.

As explained above, lens unit102in this embodiment is configured by stacking the plate members of lens cover111, first lens array112, partition wall light block plate113, second lens array114, and incident light block plate115. Note that, in this embodiment, one partition wall light block plate113is disposed between first lens array112and second lens array114. However, two or more plate members such as light block members may be disposed.

A stacked configuration of lens unit102is explained with reference toFIGS. 5 to 13.

First,FIG. 5is a perspective view of the lens unit. At the longitudinal center portion of lens unit102illustrated inFIG. 5, the stacked members of lens unit102are fixed (bonded) to one another by adhesive106. At positions other than the longitudinal center portion of lens unit102, the stacked members of lens unit102are clamped by clamp members104in the stacked state.

FIG. 6is an explanatory diagram of a stack structure of the lens unit.FIG. 7is an enlarged view of the stack structure of the lens unit (an enlarged view of the region CC inFIG. 6).FIG. 7illustrates a state before the members of lens unit102are stacked.

InFIGS. 6 and 7, lens unit102includes, from the upper side toward the lower side, lens cover111, first lens array112, partition wall light block plate113, second lens array114, and incident light block plate115as members of lens unit102.

First lens array112and second lens array114are desirably injection-molded using the same mold. First lens array112and second lens array114are disposed to be rotation-symmetrical to each other with the longitudinal direction of partition wall light block plate113as a rotation axis. First lens array112and second lens array114are shifted in the longitudinal direction by a half cycle (P/2) of lens pitch P to align the optical axes of the lenses. Note that, in first lens array112and second lens array114, multiple micro-lenses are arrayed in a zigzag in two rows in the longitudinal direction. An interval between the optical axes of the micro-lenses in the same row (e.g., optical axis102band optical axis102c) is arrayed as lens pitch P in the longitudinal direction.

First lens array112and second lens array114are stacked in this way because, when first lens array112and second lens array114are manufactured by injection molding, it is possible to suppress deviation of the lens optical axes of first lens array112and second lens array114as much as possible by adjusting molding accuracy of a mold and the direction of a resin flow.

With such a stack structure of first lens array112and second lens array114, in the stack structure of lens unit102illustrated inFIGS. 6 and 7, lens cover111, first lens array112, partition wall light block plate113, second lens array114, and incident light block plate115are shifted in the longitudinal direction by the half cycle (P/2) of lens pitch P and stacked.

FIG. 8is an enlarged view of the stack structure of the lens unit and is an enlarged view of region AA in the longitudinal center portion of lens unit102illustrated inFIG. 6.FIG. 9is an enlarged view of a stacked state of the lens unit in the first embodiment and is a view illustrating a state in which the members of the lens unit illustrated inFIG. 8are stacked.FIG. 10is an explanatory diagram of a bonding structure (a fixation structure) of the lens unit.

As shown inFIGS. 8 and 9, an engagement section at or in vicinity of the longitudinal center portion of lens unit102illustrated inFIG. 6includes protrusions121a,121c,121f, and121hfunctioning as engagement parts and recesses121b,121d,121e, and121gfunctioning as engagement parts for positioning each of the members with respect to the other members in the longitudinal direction, the widthwise direction, and the optical axis height direction, for example, by restricting movements or misalignments of each of the members with respect to adjacent members in the longitudinal direction, the widthwise direction, and the optical axis height direction. The protrusions121a,121c,121f, and121hand recesses121b,121d,121e, and121gare formed in ribs provided at the outer circumferential edge portion of lens cover111and the outer circumferential edge portions of regions where the lens arrays are disposed in first lens array112and second lens array114and in ribs provided at the outer circumferential edge portions of aperture regions where diaphragms are disposed in partition wall light block plate113and incident light block plate115.

When protrusions121a,121c,121f, and121hand recesses121b,121d,121e, and121gare respectively fit with each other as illustrated inFIG. 9, the members are engaged with one another and can be highly accurately positioned in the longitudinal direction, the widthwise direction, and the optical axis height direction such that, for example, maximum tolerance is approximately 10 μm.

On side surfaces of the ribs of lens cover111, first lens array112, partition wall light block plate113, second lens array114, and incident light block plate115, recesses122a,122b,122c,122d, and122e, which extend in the stacking direction on the side surfaces of the members and in which adhesive106is filled, are formed such that the members can be bonded and fixed by adhesive106illustrated inFIG. 10after the members are stacked.

Since first lens array112and second lens array114are injection-molded using the same mold, recess122bformed in first lens array112and recess122dformed in second lens array114are formed to be wider than other recesses122a,122c, and122eby the half cycle (P/2) of lens pitch P in the longitudinal direction in order to linearly form recesses122in the stacking direction when first lens array112and second lens array114are shifted from each other in the longitudinal direction by the half cycle (P/2) of lens pitch P and stacked.

FIG. 11is an enlarged view of the stack structure of the lens unit, illustrating region BB other than the longitudinal center portion of lens unit102illustrated inFIG. 6.FIG. 12is an enlarged view of the stacked state of the lens unit, illustrating a state in which the members of the lens unit illustrated inFIG. 11are stacked.FIG. 13is an explanatory diagram of a clamp structure of the lens unit.

In this embodiment, at the plural positions (engagement sections) other than the longitudinal center portion of lens unit102illustrated inFIG. 6, the members are engaged with one another with the engagement parts rather than being fixed to one another by an adhesive taking into account the fact that expansion and contraction depending on coefficients of linear expansion in the materials of lens cover111, first lens array112, partition wall light block plate113, second lens array114, and incident light block plate115occur depending on temperature and humidity environments around print head101(seeFIG. 1). Consequently, at the engagement sections other than the longitudinal center portion of lens unit102, each of the members are positioned with respect to the other members in the widthwise direction and the optical axis direction while each of the members are allowed to slide (expansion and contraction) with respect to the other members in the longitudinal direction of lens unit102. For example, at the engagement sections other than the longitudinal center portion of lens unit102, misalignments or movements of each of the members with respect to adjacent members are restricted in the widthwise direction and the optical axis direction and are not restricted in the longitudinal direction of lens unit102.

As illustrated inFIGS. 11 and 12, at each of such engagement sections, sliding protrusions123a,123c,123f, and123hfunctioning as engagement parts and sliding recesses123b,123d,123e, and123gfunctioning as engagement parts are formed on the ribs of the members. Sliding recesses123b,123d,123e, and123gare formed to correspond to sliding protrusions123a,123c,123f, and123h. In order to enable the members to slide only in the longitudinal direction of lens unit102in a state in which sliding protrusions123a,123c,123f, and123hand sliding recesses123b,123d,123d, and123gare fit with each other, the dimension in the longitudinal direction of lens unit102of sliding recesses123b,123d,123e, and123gis formed to be longer than the dimension in the longitudinal direction of lens unit102of sliding protrusions123a,123c,123f, and123hby a slidable length.

In this way, in this embodiment, fitting structures123are formed by sliding protrusions123a,123c,123f, and123hand sliding recesses123b,123d,123e, and123gdisposed in the longitudinal direction of lens unit102. The stacked members of lens unit102are engaged with one another to align the optical axes of the lenses.

As illustrated inFIG. 13, clamp members104are fit and attached in recess124aformed at the outer edge portion of lens cover111and recess124bformed at the outer edge portion of incident light block plate115to cover fitting structure123illustrated inFIG. 12. Clamp members104are disposed in positions corresponding to at least one fitting structure123in the longitudinal direction of the lens unit (in this embodiment, all fitting structures123excluding the longitudinal center portion of the lens unit) to clamp at both widthwise end portions of all the stacked members.

Recesses124aand124b, which are provided at portions of lens unit102in contact with clamp members104, are each formed in a taper shape increased in a recess amount toward the widthwise center of lens unit102in order to prevent clamp members104from coming off.

In the longitudinal direction of lens unit102, two end portions of clamp members104and two end portions of recesses124aand124bare formed such that clearances X and X′ are provided between the two end portions of clamp members104and the two end portions of recesses124aand124b. Clamp members104are fit in recesses124aand124b.

Clamp members104and recesses124aand124bare formed in this way in order to absorb a displacement amount caused by a difference in a coefficient of linear expansion from holder103when lens unit102expands and contracts in the longitudinal direction because of temperature and humidity environments around print head101(seeFIG. 1) in use. This enables the members of lens cover111, first lens array112, partition wall light block plate113, second lens array114, and incident light block plate115to slide between clamp members104.

Note that clearances X and X′ are determined in view of coefficients of linear expansion due to temperature and water absorption of lens cover111, partition wall light block plate113, and incident light block plate115configuring lens unit102and holder103illustrated inFIG. 2.

Next, modification 1 of the lens unit is explained.FIG. 14is a perspective view of a lens unit in the modification1 of the first embodiment.FIGS. 15A to 15Care explanatory diagrams of a clamp structure of the lens unit in the modification 1.

In lens unit130in the modification 1 shown inFIGS. 14 to 15C, members of lens cover131, first lens array112, partition wall light block plate113, second lens array114, and incident light block plate135are clamped by clamp members104.

In the modification 1, the configurations of recess133aformed at the outer edge portion of lens cover131and recess133bformed at the outer edge portion of incident light block plate135are different from recess124aand recess124bexplained above.

In recess133aand recess133b, which are provided at portions in contact with clamp members104, taper sections133cand133dincluding inclined surfaces (inclined surfaces increased in a recess amount along the longitudinal direction) are formed to extend in the longitudinal direction of lens unit130. Clamp members104are fit in taper sections133cand133dwhen clamp members104are attached to lens unit130.

As illustrated inFIG. 15B, first, clamp members104are fit in portions having large recess amounts of recess133aand recess133b. As illustrated inFIG. 15C, fit clamp members104are slid to portions having small recess amounts of recess133aand recess133bin the longitudinal direction to clamp and fix the members of lens cover131, first lens array112, partition wall light block plate113, second lens array114, and incident light block plate135.

Note that, in the modification 1, as in the first embodiment, clearance X is provided between end portions (end portions in the longitudinal direction of lens unit130) of clamp members104and end portions (end portions in the longitudinal direction of lens unit130) of recess133aand recess133b.

Next, modification 2 of the lens unit is explained.FIGS. 16A and 16Bare explanatory diagrams of a print head according to the modification 2 of the first embodiment.FIG. 17is a sectional view of the print head according to the modification 2.FIG. 18is a perspective view of the lens unit in the modification 2.FIGS. 19A and 19Bare enlarged views of a stacked state of the lens unit according to the modification 2.FIGS. 20A and 20Bare explanatory diagrams of a clamp state of the lens unit according to the modification 2.

FIG. 16Ais a perspective view of the print head according to the modification 2.FIG. 16Bis a plan view of the print head according to the modification 2.FIG. 19Ais an enlarged view of a region other than the longitudinal center portion of lens unit172illustrated inFIG. 18.FIG. 19Bis an enlarged view of a region in the longitudinal center portion of lens unit172illustrated inFIG. 18.FIG. 20Ais a sectional view of a part other than the longitudinal center portion of lens unit172illustrated inFIG. 18.FIG. 20Bis a sectional view of the longitudinal center portion of lens unit172illustrated inFIG. 18.

As shown inFIGS. 16A and 16B and 17, according to lens unit172of the modification 2, stacked members (lens cover181, first lens array112, partition wall light block plate113, second lens array114, and incident light block plate185) of the lens unit172are clamped to be fixed with each other by clamp members104at the longitudinal center portion of lens unit172.

As illustrated inFIG. 18, the stacked members of lens unit172are clamped by clamp members104in the engagement section at the other engagement selections other than the longitudinal center portion.

That is, in the modification 2, all the stacked members are fixed with each other at a fixation part in the longitudinal center portion of lens unit172(a fixation part in which clamp members104are disposed).

In the longitudinal center portion of lens unit172, the members of lens unit172are clamped to be fixed with one another by clamp members104as illustrated inFIG. 17. When lens unit172is attached to holder103, lens unit172is attached to holder103using adhesive174via clamp members104, at the longitudinal center portion of lens unit172, as in the positions other than the center part.

In the longitudinal center portion of lens unit172as illustrated inFIG. 19B, as in the engagement sections illustrated inFIG. 19Aother than the longitudinal center portion, recesses184aand184b, which are provided at portions in contact with clamp members104, are formed. Recesses184aare formed at the outer edge portion of lens cover181. Recess184bare formed at the outer edge portion of incident light block plate185.

Recesses184aand184b, which are provided at the portions in contact with clamp members104, are formed in a taper shape increased in recess amounts in the stacking direction of the members of lens unit172toward the widthwise center of lens unit172in order to prevent clamp members104from coming off.

As illustrated inFIGS. 20A and 20B, a recess amount Δh10 of recess184ain the engagement section at the longitudinal center portion of lens unit172is formed to be smaller than a recess amount Δh11 of recess124ain the engagement sections other than the longitudinal center portion of lens unit172. A recess amount Δh20 of recess184bat the engagement section at the longitudinal center portion of lens unit172is formed to be smaller than a recess amount Δh21 of recess124bin the engagement sections other than the longitudinal center portion of lens unit172.

This is for the purpose of setting supporting points of the members in lens unit172as portions clamped by clamp members104in the longitudinal center portion of lens unit172.

As lens covers111and131, acrylic resin is used. However, polycarbonate and the like can also be used in order to adjust a coefficient of linear explanation to coefficients of linear explanation of the other members.

As first lens array112and second lens array114, cycloolefin polymer resin (product name: ZEONEX (registered trademark) manufactured by ZEON Corporation) is used. Acrylic resin, polycarbonate, or epoxy resin can also be used. However, in a long structure in this embodiment, it may be preferable to use the cycloolefin polymer resin having a small water absorption rate from the viewpoint of dimension stability.

As partition wall light block plate113and incident light block plate115, polycarbonate is used. ABS (acrylonitrile butadiene styrene) resin can be used. However, since it is desirable to set coefficients of linear expansion of lens cover111, first lens array112, and second lens array114the same as much as possible, it is desirable to use polycarbonate.

As clamp members104, a stainless steel material for spring is used.

As holder,103, a sheet metal is used. However, LCP (liquid crystal polymer) resin and aluminum die-cast can also be used.

Printed wiring board116is obtained by patterning a copper foil using a glass cloth epoxy resin substrate as a core material.

Semiconductor light emitting elements117is obtained by substantially linearly arraying, for example, at 600 dpi (dots per inch) or 1200 dpi, light emitting diode elements containing GaAs (gallium arsenic) as a main material. Semiconductor light emitting elements117can also be an element in which a driving circuit is integrally molded.

As base clamp member119, polycarbonate is used. However, nylon and the like can also be used.

Adhesives105,106, and107are UV (Ultra Violet) curing resin containing acrylic resin as a main component. A contact image sensor head (hereinafter referred to as “image sensor head”) included in an image scanner functioning as an image scanner apparatus is explained. Note that the configuration of the image scanner is explained below.

FIGS. 21A and 21Bare explanatory diagrams of the image sensor head in the first embodiment.FIG. 21Ais a perspective view of the image sensor head.FIG. 21Bis a plan view of the image sensor head.FIG. 22is a sectional view of the image sensor head taken along the X-X line inFIGS. 21B.FIG. 23is a sectional view of the image sensor head taken along the Y-Y line inFIG. 21B.

Image sensor head140according to this embodiment is explained with reference toFIGS. 21A to 23. As illustrated inFIG. 22, in image sensor head140, at the attachment parts of lens unit141to holder150other than the longitudinal center portion of lens unit141, lens unit141is attached (bonded) to holder150with adhesive151filled between clamp members147of lens unit141and holder150.

As in lens unit102used in print head101illustrated inFIG. 2, pairs of clamp members147clamp lens cover142, first lens array143, partition wall light block plate144, second lens array145, and incident light block plate146.

The attachment positions of lens unit141to holder150are determined when receiving section152of lens unit141in holder150and a rib lower surface of incident light block plate146of lens unit141come into contact with each other such that distance Lo between the surface of semiconductor light receiving element149linearly arrayed on printed wiring board148and a lower surface extreme point of second lens array145in lens unit141is an optical designed distance.

Printed wiring board148mounted with semiconductor light receiving element149is positioned by coming into contact with substrate contract section153provided in holder150. As a method of attaching printed wiring board148to holder150, printed wiring board148is attached to holder150using an adhesive or printed wiring board148is held between holder150and a base clamp member using the base clamp member as in the print head101illustrated inFIG. 2.

Light guide body154for propagating light irradiated from a light source of image sensor head140on scanned document surface409ais fixed to holder150to be set beside the widthwise direction of lens unit141. Light blocking cover155is provided to prevent a light leak from a part other than a light irradiation surface of light guide body154.

An attaching position of image sensor head140is adjusted such that distance Li between an upper extreme point of first lens array143of lens unit141and scanned document surface409ais an optical designed distance.

As illustrated inFIG. 23, at the attachment part of lens unit140to the holder150at the longitudinal center portion, the stacked members (bonding lens cover142, first lens array143, partition wall light block plate144, second lens array145, and incident light block plate146) of the lens unit are bonded with one another with adhesive156, and adhesive157is bonded to the adhesive156or is bonded directly to at least one of the stacked members (lens cover142, first lens array143, partition wall light block plate144, second lens array145, and incident light block plate146), so that lens unit141is fixed (attached) to holder150with adhesive157.

The stacked members (lens cover142, first lens array143, partition wall light block plate144, second lens array145, and incident light block plate146) of the lens unit are the same as lens cover111, first lens array112, partition wall light block plate113, second lens array114, and incident light block plate115(seeFIG. 2) of lens unit102used in the printer head explained above.

Adhesives151,156, and157are UV curing resin containing acrylic resin as a main component. Printed wiring board148is obtained by patterning a copper foil using a glass cloth epoxy resin substrate as a core material.

Semiconductor light receiving element149is obtained by substantially linearly arraying, for example, at 600 dpi, 1200 dpi, or 2400 dpi, CMOS sensors or CCD sensors manufactured on an Si substrate.

As light guide body154, acrylic resin is used. Light blocking cover155of light guide body154can be molded resin having high universality.

Next, operations of the configuration explained above is explained. Operations of lens unit102illustrated inFIGS. 2 to 13used in print head101illustrated inFIGS. 1A to 1D, operations of lens unit130illustrated inFIGS. 14 to 15C, and operations of lens unit141illustrated inFIGS. 22 and 23used in image sensor head140illustrated inFIGS. 21A and 21B will be explained with reference toFIGS. 1A to 23.

Lens units102,130, and141have a configuration in which members of a resin plate such as lens covers111,131, and142, first lens arrays112and143, partition wall light block plates113and144, second lens arrays114and145, and incident light block plates115,135,146are stacked. Therefore, when coefficients of linear expansion due to heat or water absorption of the members are different, expansion and contraction of the members involved in the respective coefficients of linear expansion occur.

In that case, if the members are bonded to one another using an adhesive at two or more positions in the longitudinal direction of the members, lens units102,130, and141as a whole may warp in a lens optical axis direction because of the members may expand and contract corresponding to their coefficients of linear expansion.

On the other hand, in lens units102,130, and141in this embodiment, the stacked members are mutually bonded with adhesives106and156at only one place in the longitudinal direction, which is the longitudinal center portion. Engagement sections other than the longitudinal center portion are clamped by by clamp members104and147to held all the stacked member from both sides in the optical axis direction.

In this way, in the engagement sections other than the longitudinal center portion, the stacked members are not bonded to one another. Therefore, each of the stacked members can slide with respect to the other stacked members in the longitudinal direction, at the positions other than the longitudinal center portion.

In this embodiment, when the members slide, the members restrict one another in the widthwise direction and the lens optical axis direction with sliding protrusions123a,123c,123f, and123hand sliding recesses123b,123d,123e, and123gprovided in the members. Therefore, deviation of optical design is limited only in the longitudinal direction.

Further in this embodiment, at only the longitudinal center portion of lens units102,130, and141, the stacked members are fixed (bonded) to one another by adhesives106and156. Therefore, it is possible to match action points due to expansion and contraction of the members in the longitudinal direction.

In print head101including lens units102and130explained above, lens units102and130and holder103are attached to holder103by adhesive105via clamp members104in the engagement sections other than the longitudinal center portion of lens units102and130.

Therefore, even when there is a difference between a coefficient of linear expansion of lens units102and130and a coefficient of linear expansion of holder103, it is possible to absorb the difference between expansion and contraction amounts of lens units102and130and holder103by sliding lens units102and130in the longitudinal direction in clamp members104.

At the longitudinal center portion of lens units102and130, at least one of lens covers111and131, first lens array112, partition wall light block plate113, second lens array114, incident light block plates115and135, and adhesive106of lens units102and130is directly attached (bonded) to holder103using adhesive107.

Therefore, even when expansion and contraction occur in the longitudinal direction of lens units102and130, an action point of the expansion and contraction can always be set in the longitudinal center portion of a light emitting region of print head101.

In lens unit130, which is the modification 1 of lens unit102, compared with lens unit102, when clamp members104are attached, it is possible to prevent damage to the widthwise end portions extending in the longitudinal direction of lens cover131and incident light block plate135due to contact with clamp members104and occurrence of dust due to the damage.

Further, in lens unit172, which is the modification 2 of lens unit102, since the stacked members are fixed with each other using clamp members104at the longitudinal center portion of lens unit172as in the engagement sections other than the longitudinal center portion, it is possible to easily perform disassembly and reassembly of lens unit172by detaching clamp members104.

In the modification 2, the recess amount of recesses184aand184bformed in lens cover181and incident light block plate185in the longitudinal center portion of lens unit172are formed smaller (shallower) than the recess amount of recesses124aand124bin the part other than the center part. Therefore, it is possible to set a clamp force by clamp members104in the longitudinal center portion of lens unit172higher than a clamp force in the part other than the center part. It is possible to set the longitudinal center portion of lens unit172as a support point of lens unit172.

In image sensor head140illustrated inFIGS. 21A and 21Bincluding lens unit141illustrated inFIGS. 22 and 23, as in print head101explained above, lens unit141is attached to holder150by adhesive151via clamp members147at the positions other than the longitudinal center portion of lens unit141.

Therefore, even when there is a difference between a coefficient of linear expansion of lens unit141and a coefficient of linear expansion of holder150, it is possible to absorb the difference between expansion and contraction amounts of lens unit141and holder150by sliding lens unit141in the longitudinal direction in clamp members147.

At the longitudinal center portion of lens unit141, adhesive157is directly attached to at least one of lens cover142, first lens array143, partition wall light block plate144, second lens array145, incident light block plate146, and adhesive156of lens unit141, so that lens unit141is attached to holder150using adhesive157.

Therefore, even when expansion and contraction occur in the longitudinal direction of lens unit141, an action point of the expansion and contraction can always be set in the longitudinal center portion of an imaging region of image sensor head140.

In this way, in this embodiment, even when an expansion and contraction difference occurs between the constituent members of the lens unit due to ambient temperature and humidity fluctuation, after suppressing warp in the lens optical axis direction of the lens unit, it is possible to maintain design positions of the lens unit in the lens optical axis direction and a direction orthogonal to the lens array direction.

When the lens unit is fixed to the holder, the adhesive is filled between the clamp members of the lens unit and the holder. Therefore, when expansion and contraction of the lens unit occur, it is possible to slide the lens unit in the clamp members. Therefore, it is possible to suppress a break between the lens unit and the holder and warp of the lens unit in the lens optical axis direction.

Therefore, even when there is ambient temperature and humidity fluctuation, it is possible to use the lens unit without deteriorating printing quality and scanning accuracy.

Next, an example is explained in which print head101illustrated inFIGS. 1A and 1Bis applied to a printer as an image forming apparatus.

FIG. 24is a schematic side sectional view illustrating the configuration of the printer. InFIG. 24, printer301as an image forming apparatus is an LED (Light Emitting Diode) printer mounted with print head101illustrated inFIG. 1.

Printer301includes four process units302,303,304, and305that form images of respective colors of yellow (Y), magenta (M), cyan (C), and black (K) using an electrophotographic system.

Process units302,303,304, and305are disposed in the order of process unit302(Y), process unit303(M), process unit304(C), and process unit305(K) along conveyance route307of recording media306.

Process units302,303,304, and305include photosensitive drums308functioning as image bearing bodies, charging devices309that are disposed around photosensitive drums308and charge the surfaces of photosensitive drums308, and exposing devices310that selectively irradiate lights on the charged surfaces of photosensitive drums308and form electrostatic latent images. In exposing devices310, print head101illustrated inFIGS. 1A and 1Bis used as a light source.

Process units302,303,304, and305include developing devices311that convey toners functioning as developers to the surfaces of photosensitive drums308on which the electrostatic latent images are formed and form toner images and cleaning devices312that remove the toners remaining on the surfaces of photosensitive drums308.

Note that photosensitive drums308rotate in a direction indicated by an arrow in the figure by a driving source such as a motor and a driving mechanism such as a gear.

Printer301includes sheet cassette313that stores recording media306such as paper and hopping roller314that separates recording media306stored in sheet cassette313one by one and conveys recording media306.

Downstream of hopping roller314in a conveying direction of recording media306, pinch rollers315and316and registration rollers317and318that pinch recording media306, correct skew feeding of recording media306in conjunction with pinch rollers315and316, and convey recording media306to process units302,303,304, and305are disposed. Note that hopping roller314and registration rollers317and318are connected to the driving source such as the motor and rotate in association with one another.

Printer301includes transfer rollers319disposed to be opposed to photosensitive drums308. Transfer rollers319are configured by semi-conductive rubber or the like. Potential of photosensitive drums308and potential of transfer rollers319are set to transfer the toner images on photosensitive drums308onto recording media306.

Printer301includes fixation device324that fixes the toner images transferred onto recording media306with heat and pressure and discharge rollers320,321,322, and323that discharge recording media306, on which the toner images are fixed, to a stacker325on the outside of the apparatus.

Recording media306stacked on sheet cassette313are separated one by one and conveyed by hopping roller314. Recording media306pass registration rollers317and318and pinch rollers315and316and pass process units302,303,304, and305in this order. In process units302,303,304, and305, recording media306pass between photosensitive drums308and transfer rollers319, the toner images of the respective colors are transferred onto recording media306in order, recording media306are heated and pressurized by fixation device324, and the toner images of the respective colors are fixed on the recording media306. Thereafter, recording media306are discharged to stacker325by discharge rollers320,321,322, and323.

Next, an example is explained in which image sensor head140illustrated inFIGS. 21A and 21Bis applied to an image scanner functioning as an image scanner apparatus.

FIG. 25is a perspective view illustrating the configuration of the image scanner. InFIG. 25, image scanner401includes housing402, platen409that is provided on the upper surface of housing402and on which an original document to be scanned is placed, and lid410for holding the original document between lid410and platen409.

On the inside of housing402, contact image sensor head403including image sensor head140illustrated inFIGS. 21A and 21Bis disposed. Contact image sensor head403is supported by and attached to two guides404fixed to housing402.

In order to slide contact image sensor head403in a sub-scanning direction along guide404, contact image sensor head403is coupled to driving belt406coupled to stepping motor405.

Control circuit408that controls contact image sensor head403is connected to contact image sensor head403via flexible flat cable407.

As explained above, in the first embodiment, the lens unit is attached to the holder by the adhesive via the clamp members in positions other than the longitudinal center portion of the lens unit. Therefore, it is possible to suppress warp in the lens optical axis direction of the lens unit due to the influence of expansion and contraction displacement depending on a coefficient of linear expansion difference between the constituent members of the lens unit caused by an ambient temperature or humidity environment.

At least a part of the lens unit is attached to the holder by the adhesive at the longitudinal center portion of the lens unit. This produces an effect that it is possible to absorb an expansion and contraction displacement amount in the longitudinal direction depending on a difference in coefficient of linear expansion between the constituent members of the lens unit by using the longitudinal center portion of the lens unit as an action point.

Further, when the lens unit in this embodiment is mounted on the print head or the image sensor head, the influence of expansion and contraction displacement depending on a coefficient of linear expansion that occurs between the lens unit and the holder is absorbed by sliding the stacked members of the lens unit in the clamp members. As a result, there is an effect that it is possible to suppress warp in the lens optical axis direction of the lens unit, secure stable optical performance, and suppress the lens unit from being sheared and peeled from the holder.

Therefore, by using the print head including the lens unit in this embodiment in the image forming apparatus, it is possible to secure stable printing quality without being affected by fluctuation in an ambient environment.

By using the image sensor head including the lens unit in this embodiment in the image scanner apparatus, it is possible to secure stable scanning quality without being affected by fluctuation in an ambient environment.

Second Embodiment

A configuration in the second embodiment is different from the configuration in the first embodiment in that a lens adhesive filling section is provided in a region where an adhesive for fixing a lens unit to a holder is applied. The configuration in the second embodiment is explained on the basis ofFIGS. 26A to 29.

FIGS. 26A to 26Dare explanatory diagrams of a print head in the second embodiment.FIG. 26Ais a perspective view of the print head.FIG. 26Bis a plan view of the print head.FIG. 26Cis an enlarged view of an attachment part of the lens unit to the holder at the longitudinal center portion of the print head.FIG. 26Dis an enlarged view of attachments parts of the lens unit to the holder at positions other than the longitudinal center portion of the print head.

FIG. 27is a sectional view of the print head in the second embodiment taken along the X-X line inFIG. 26B.FIGS. 28A and 28Bare explanatory diagrams of the holder in the second embodiment.FIG. 28Ais a plan view of the holder.FIG. 28Bis an sectional view along the X-X line inFIG. 28A.FIG. 29is a sectional view of the print head taken along the Y-Y line inFIG. 26B. Note that portions same as the portions in the first embodiment explained above are denoted by the same reference numerals and signs and explanation of the portions is omitted.

In print head201illustrated inFIGS. 26A and 26B, as in print head101illustrated inFIG. 1, in order to clearly illustrate a bonding structure of lens unit202and holder203, illustration of a silicone sealing material between lens unit202and holder203is omitted.

Print head201in this embodiment is explained with reference toFIGS. 26A to 29. In print head201in this embodiment, as in the first embodiment, lens unit202is attached to holder203using adhesives207and211.

In each of the attachment parts of lens unit202to holder203other than the longitudinal center portion of print head201illustrated inFIG. 26D, as illustrated inFIG. 27, the stacked members (lens cover212, first lens array213, partition wall light block plate214, second lens array215, and incident light block plate216) of lens unit202in the optical axis direction are clamped with pairs of clamp members204provided at the widthwise ends of lens unit102.

In lens unit202, adhesive207is filled in lens adhesive filling section205positioned between clamp members204and holder203. Lens unit202is thus attached (fixed) to holder203with adhesive207.

On the other hand, as illustrated inFIG. 29, in the attachment part of lens unit202to holder203at the longitudinal center portion of print head201illustrated inFIG. 26C, stacked members (lens cover212, first lens array213, partition wall light block plate214, second lens array215, and incident light block plate216) of lens unit202are bonded with each other with adhesive208filled on both widthwise end portions of lens unit202, and adhesive211is filled formed between lens unit202and holder203such that adhesive211is in direct contact with at least one of lens cover212, first lens array213, partition wall light block plate214, second lens array215, incident light block plate216, and adhesive208. In this way, the lens unit202is attached (fixed) to the holder203.

In lens unit202of print head201in this embodiment, lens adhesive filling sections205and209are provided in regions where adhesives207and211for attaching lens unit202to holder203are applied.

In lens adhesive filling sections205and209, grooves extending in the lens optical axis direction (the stacking direction of the members of lens unit202) are formed in order to fill adhesives207and211. For example, as illustrated inFIG. 28B, groove205afor filling adhesive207in lens adhesive filling section205is formed to extend in the lens optical axis direction.

In lens adhesive filling sections205and209, filling ports206and210for filling adhesives207and211are formed. Filling ports206and210are formed at end portions of lens adhesive filling sections205and209on the opposite side of semiconductor light emitting elements117.

In lens adhesive filling sections205and209, as illustrated inFIGS. 27 and 29, in order to suppress adhesives207and211from flowing to the lower surface of lens unit202, adhesive catcher sections217and218that catches adhesives207and211filled are formed in positions higher than the lower surface of lens unit202(positions on the inner side of an end face of lens unit202in the stacking direction of the members).

Adhesive catcher sections217and218form bottom sections of lens adhesive filling sections205and209. Adhesive catcher sections217and218are formed at end portions of lens adhesive filling sections205and209on the semiconductor light emitting elements117side.

Distance (height) Z2from adhesive catcher sections217and218of lens adhesive filling sections205and209to filling ports206and210is desirably at least a half of length (height) Z1of lens unit202in the lens optical axis direction. This is for the purpose of securing fixed attachment intensity of lens unit202and holder203.

Next, action of the configuration explained above is explained. Note that, in this embodiment, action of the lens adhesive filling sections of the lens unit is explained with reference toFIGS. 26A to 29. Explanation of operations of the lens unit used for the printer head and the lens unit used for the image sensor head explained in the first embodiment is omitted.

In this embodiment, adhesives207and211are filled from filling ports206and210of lens adhesive filling sections205and209illustrated inFIGS. 26A to 29. Adhesives207and211filled from filling ports206and210are filled in grooves extending from adhesive catcher sections217and218to filling ports206and210and fixedly attach lens unit202and holder203.

As explained above, in lens adhesive filling sections205and209provided in lens unit202and holder203, adhesives207and211are widely used in the lens optical axis direction (the height direction) of lens unit202to bond lens unit202and holder203. Consequently, it is possible to obtain a rectifying force for stress in a rotating direction around a rotation axis set in the widthwise direction of lens unit202, the lens optical axis direction or the longitudinal direction.

Adhesive catcher sections217and218can be provided by forming lens adhesive filling sections205and209from resin. Therefore, it is possible to accurately bond lens unit202and holder203with adhesives207and211.

In this embodiment, the adhesive for attaching the lens unit to the holder is provided over a half or more of the length in the lens optical axis direction of the lens unit. Therefore, it is possible to obtain a sufficient rectifying force for rotation stress of the lens unit in a rotating direction around a rotation axis set in the widthwise direction of the lens unit, the lens optical axis direction, or the longitudinal direction. Therefore, it is possible to suppress fluctuation of the lens optical axis and suppress deterioration in printing quality and scanning accuracy depending on assembly accuracy of the lens unit.

As explained above, in the second embodiment, in addition to the effect in the first embodiment, there is an effect that it is possible to obtain a rectifying force for stress in the rotating direction around the rotation axis set in the widthwise direction of the lens unit, the lens optical axis direction, or the longitudinal direction.

There is an effect that it is possible to accurately bond the lens unit and the holder and improve printing quality and scanning quality.

Note that, in the first embodiment and the second embodiment, the image forming apparatus is explained as the printer. However, the image forming apparatus is not limited to the printer and may be a copying machine, a facsimile apparatus, a multifunction peripheral (MFP), and the like.

The image forming apparatus is explained as the printer of a direct transfer type. However, the image forming apparatus is not limited to the printer of the direct transfer type and may be a printer of an intermediate transfer type including an intermediate transfer body, a copying machine, a facsimile apparatus, a multifunction peripheral (MFP), and the like.

Further, the image scanner apparatus is explained as the image scanner. However, the image scanner apparatus is not limited to the image scanner and may be a copying machine, a facsimile apparatus, a multifunction peripheral (MFP), and the like.