Optical scanning unit having more maintenance-friendly adjustable lens having a support member with first and second faces, an adjusting member and moving member opposite the adjusting member, and image forming apparatus including the same

An optical scanning unit includes: a light source configured to emit a light beam; a lens arranged so that the light beam emitted from the light source passes therethrough; a rotatable deflector configured to deflect the light beam coming from the lens, the deflected light beam being guided to a light receiving member; a movable lens holder configured to hold the lens, the lens holder being provided in a space between the light source and the deflector; a support member having a first face located on a first side thereof, the first face facing toward a vertically-downward direction and extending in a direction substantially parallel to a reference-axis defined between the light source and the deflector, there also being a second face located on a second side, the second face being arranged opposite to the first face; and a force-transferring member configured to transfer a force to the lens holder for moving the lens holder along the first face of the support member, the force being applied to the force-transferring member at the second side of the support member.

PRIORITY STATEMENT

This application claims foreign priority under 35 U.S.C. §119 upon Japanese patent application No. 2006-003705 filed on Jan. 11, 2006 to Japanese Patent Office, the entire contents and disclosure of which is hereby incorporated herein reference.

BACKGROUND

In general, an image forming apparatus includes an optical scanning unit. In the optical scanning unit, a light beam emitted by a light source may enter a rotatable deflector via a lens. Then, the light beam deflected by the rotatable deflector may be guided to an image-carrying member such as photoconductor to scan a surface of the image-carrying member to form a latent image on the image-carrying member.

For example, such optical writing unit may include a light source, a collimate lens, a cylindrical lens, a polygon mirror (as rotatable deflector), and other mirrors to guide a light beam from the light source to the image-carrying member.

In such optical writing unit, if a reflection face of the polygon mirror may be slanted from an optimal angle (i.e., mirror face has a tangle error), or if an axis of the polygon mirror may be slanted from an optimal angle due to assembly error, light beams may scan the image-carrying member with an uneven pitch relative to each other, or light beams may not be focused on a optimal position on the image-carrying member.

If such phenomenon may occur, a resultant image to be produced on a recording medium may have a lower image quality.

The cylindrical lens may be provided in the optical writing unit to reduce the above-mentioned drawbacks. In general, the cylindrical lens may be disposed between the light source and polygon mirror used as rotatable deflector.

A light reference-axis of the cylindrical lens may be defined between a light emitting point of the light source and a given reflection point of the polygon mirror used as rotatable deflector.

A related art image forming apparatus may include an optical writing unit having a moving unit for moving a cylindrical lens to adjust a reference-axis direction of cylindrical lens.

In such related art, the cylindrical lens may be moved by a driver (e.g. motor) to adjust a reference-axis direction of the cylindrical lens.

Accordingly, such related art may need a driver, driving-force transmission mechanism, and a driving mechanism controller, for example, by which such related art may have a complex configuration and need a space for allocating such devices. Such a configuration may not be favorable from a viewpoint of miniaturization of image forming apparatus.

Another related art image forming apparatus may include an optical writing unit having another configuration for moving a cylindrical lens in its reference-axis direction.

Such optical writing unit may include a lens holder, which holds the cylindrical lens, and a housing having a support face on which the lens holder is placed.

The lens holder may be movable on the support face in a direction parallel to a reference-axis direction of the cylindrical lens.

The support face may include a guide member thereon to guide a movement of the lens holder in the reference-axis direction of the cylindrical lens.

The lens holder may have an adjustment hole, which has a substantially rectangular shape formed along the support face and parallel to the reference-axis direction.

A screw may be inserted through the adjustment hole and then may be engaged with a screw hole provided on the housing used as support member.

In such optical writing unit, the screw may be loosened when adjusting a position of the cylindrical lens.

Specifically, under such screw-loosened condition, the lens holder may be moved in the reference-axis direction by a force applied from a hand of maintenance person to adjust a position of the lens holder.

After adjusting a position of the lens holder at an appropriate position, the screw may be tightened to fix the cylindrical lens at such appropriate position.

Such optical writing unit may not need a driver, driving-force transmission mechanism, and a driving mechanism controller to adjust a position of the cylindrical lens, by which such another related art may not need a complex configuration and a space for allocating such devices.

Another background art image forming apparatus may include another optical writing unit having another configuration for moving a cylindrical lens in its reference-axis direction.

Such optical writing unit may include a lens holder for holding a cylindrical lens, and a housing (used as support member) having a support face having a guide hole.

The guide hole may have a substantially rectangular shape formed along the support face and parallel to the reference-axis direction.

The lens holder has a protruded portion to be snap-fitted to the guide hole, and the lens holder may be moveable on the support face in the reference-axis direction of the cylindrical lens when the protruded portion of lens holder moves in the guide hole.

Furthermore, the housing may have a long-shaped hole aligned in the reference-axis direction of the cylindrical lens.

When the lens holder is placed on the housing, a projection portion of the lens holder may be exposed to an outside of the housing. In other words, the projection of the lens holder may pass though the long-shaped hole, and an exposed portion of the lens holder may be used to move the lens holder in the reference-axis direction of the cylindrical lens.

Specifically, a maintenance person may grab the exposed portion of the lens holder and move the lens holder along the long-shaped hole by applying a hand force, by which a position of the cylindrical lens may be adjusted.

Such optical writing unit may further include another configuration having an eccentric cam for moving the cylindrical lens in the reference-axis direction with a hand force of maintenance person.

In this art, the lens holder may have a long-shaped hole formed in a direction perpendicular to a reference-axis direction.

The eccentric cam may include a circular base, a center-axis shaft, and an eccentric-axis shaft, for example.

The center-axis shaft may extend in a first direction from the circular base and may be aligned on a rotational axis of the circular base.

The eccentric-axis shaft may extend in a second direction from the circular base deviated from a rotational axis of the circular base. The first direction and second direction may be set to an opposite direction each other, for example.

The center-axis shaft of eccentric cam may be inserted in a bearing hole of the housing and some part of the center-axis shaft may be exposed to an outside of the housing.

The eccentric-axis shaft of eccentric cam may be inserted in the long-shaped hole of the lens holder.

A maintenance person can grab an exposed portion of the center-axis shaft to rotate the eccentric cam with a hand force.

With such configuration, the lens holder may be moved in its reference-axis direction while the protruded portion of the lens holder may be guided in the guide hole of the housing.

Accordingly, a maintenance person may adjust a position of the cylindrical lens in its reference-axis direction with a hand force.

Such optical writing unit may not need a driver, driving-force transmission mechanism, and a driving mechanism controller to adjust a position of the cylindrical lens, by which such background art may not need a complex configuration and a space for allocating such devices.

However, the above-mentioned optical writing unit may have a lower working efficiency when adjusting a position of the cylindrical lens by a maintenance person. Hereinafter, such drawback may be explained.

In general, when adjusting a position of the cylindrical lens in its reference-axis direction, an optical writing unit may be placed on a platform of an adjustment machine, wherein a posture or orientation of the optical writing unit on the platform may be set substantially similar to a posture or orientation of the optical writing unit in an image forming apparatus.

Then, a light-receiving device such as CCD (charge coupled device) may be placed on a given position of the adjustment machine, wherein the given position may correspond to a position of a surface of image-carrying member (or photoconductor) when the optical writing unit is placed in the image forming apparatus. A number of light-receiving devices may be set to one or two, for example.

Then, the optical writing unit is activated, and the light-receiving device may detect a light beam scanning the image-carrying member in an axis direction of the image-carrying member.

Then, such detected result may be displayed on a display unit as lens-position-adjustment information. A maintenance person may check or look up such information to adjust a position of the cylindrical lens.

In such optical writing unit, when a maintenance person grabs the lens holder by hand to move the lens holder, the hand of maintenance person may block a path of incident light or outgoing light of the cylindrical lens.

In such configuration, the maintenance person may adjust a position of the cylindrical lens as below.

At first, the maintenance person may move the lens holder with a hand. Then, the hand is set aside from the optical writing unit so that the light-receiving device can detect a light beam.

Then, by checking or looking up lens-position-adjustment information prepared from a detection result detected by the light-receiving device, the maintenance person may move the lens holder by hand again to adjust a position of the cylindrical lens.

The maintenance person may repeat the above-mentioned processes to find an appropriate position of the cylindrical lens.

Such process may not be convenient for the maintenance person because the maintenance person may have to stop a movement of the lens holder to check or look up the lens-position-adjustment information and then restart a movement of the lens holder.

Accordingly, the maintenance person may feel an inconvenience for conducting such above-mentioned processes.

In case of background art image forming apparatus, a maintenance person can move the lens holder by grabbing the exposed portion of center-axis shaft by hand, which may be exposed to an outside of the housing.

Accordingly, a hand of maintenance person may not block an incident light or outgoing light of the cylindrical lens when adjusting a position of cylindrical lens.

Under such configuration, the maintenance person may adjust a position of the cylindrical lens as below.

The maintenance person may move the lens holder with a hand while checking or looking up lens-position-adjustment information prepared from a detection result detected by the light-receiving device to find an appropriate position of the cylindrical lens.

Accordingly, in the background art image forming apparatus, the maintenance person may adjust a position of the cylindrical lens in the optical writing unit easier compared to the above-mentioned optical writing unit in the related art image forming apparatus.

However, the optical writing unit in the background art image forming apparatus may be disposed under an image-carrying member (or photoconductor) when the optical writing unit is installed in the image forming apparatus, wherein the optical writing unit emits a light beam (or scanning light beam) in an upward direction.

Accordingly, such optical writing unit may be placed on a platform of an adjustment machine with a posture or orientation, which may be substantially similar to a posture or orientation of the optical writing unit, which is installed in the image forming apparatus.

Therefore, when the optical writing unit is placed on the platform of the adjustment machine, the exposed portion of the center-axis shaft, exposed to an outside of the housing, may face a downside in a vertical direction.

Under such configuration, the maintenance person may have to put a hand from a downside of the platform when adjusting a position of the cylindrical lens.

Accordingly, the maintenance person may have to move the exposed portion of the center-axis shaft from downside of the optical writing unit, placed on the platform of the adjustment machine.

The maintenance person may feel uncomfortable for such adjustment work compared to an adjustment work conducted from an upper side of the optical writing unit placed on the platform of the adjustment machine. Such uncomfortable situation may be undesirable from a viewpoint of a positioning the cylindrical lens with a higher precision.

Positioning of cylindrical lens in its reference-axis direction may need a higher precision to enhance or maintain an image quality to be produced by an image forming apparatus. Therefore, it has been desired that a maintenance person can conduct such adjustment work in a precise manner by a hand with a simplified manner.

SUMMARY

An embodiment of the present invention provides an optical scanning unit comprising: a light source configured to emit a light beam; a lens arranged so that the light beam emitted from the light source passes therethrough; a rotatable deflector configured to deflect the light beam coming from the lens, the deflected light beam being guided to a light receiving member; a movable lens holder configured to hold the lens, the lens holder being provided in a space between the light source and the deflector; a support member having a first face located on a first side thereof, the first face facing toward a vertically-downward direction and extending in a direction substantially parallel to a reference-axis defined between the light source and the deflector, there also being a second face located on a second side, the second face being arranged opposite to the first face; and a force-transferring member configured to transfer a force to the lens holder for moving the lens holder along the first face of the support member, the force being applied to the force-transferring member at the second side of the support member.

An embodiment of the present invention provides an image forming apparatus comprising: an image-carrying member; an optical scanning unit, such as is mentioned above, configured to form a latent image on the image-carrying member via irradiating a light beam on the image-carrying member; and a developing unit configured to develop the latent image and to transfer the developed image to a recording medium.

An embodiment of the present invention provides a method of adjusting a position of a lens in an optical scanning unit such as is mentioned above. Such a method comprises: emitting a light beam towards the lens, the light beam to be guided by the lens to a sensor placed at a given position; sensing an optical property of the light beam with the sensor; outputting information for adjusting a position of the lens in the optical scanning unit based on a result of the sensing step; applying, at the second side of the support member, a force to the force-transferring member such that the lens holder is moved along the first face of the support member; and maintaining, while the lens holder is being moved, contact between the lens and the first face of the support member.

Additional features and advantages of the present invention will be more fully apparent from the following detailed description of example embodiments, the accompanying drawings and the associated claims.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

Referring now to the drawings, wherein like reference numerals designate identical or corresponding parts throughout the several views, an image forming apparatus according to an example embodiment is described with particular reference toFIG. 1.

FIG. 1is a schematic cross-sectional view of an image forming apparatus1according to an example embodiment. The image forming apparatus1may include a printer having a tandem arrangement and intermediate transfer method, but the image forming apparatus1may not be limited to such printer but may include other applications.

As show inFIG. 1, the image forming apparatus1may include a sheet cassette2, image forming units3Y,3C,3M, and3K, an optical writing unit4, an intermediate transfer unit5, and a fixing unit6, for example.

The sheet cassette2may be withdrawable from the image forming apparatus1.

The image forming units3Y,3C,3M, and3K may be used to form toner images of yellow(Y), cyan(C), magenta(M), and black(K), respectively. Hereinafter, reference characters of Y, C, M, and K may represent yellow, cyan, magenta, and black, respectively.

FIG. 2is a schematic cross-sectional view of the image forming unit3Y. The image forming units3Y,3C,3M, and3K may take a similar configuration one another except toner colors.

As shown inFIGS. 1 and 2, the image forming units3Y,3C,3M, and3K may include photoconductors10Y,10C,10M, and10K, respectively.

The image forming units3Y,3C,3M, and3K may further include charge units11Y,11C,11M, and11K, developing units12Y,12C,12M, and12K, and cleaning units13Y,13C,13M, and13K around the photoconductors10Y,10C,10M, and10K, respectively.

The photoconductors10Y,10C,10M, and10K having a drum shape may rotate in a direction shown by an arrow A inFIG. 2. The photoconductors10Y,10C,10M, and10K may be used as an image carrier, which forms a latent image and a toner image thereon.

For example, each of the photoconductors10Y,10C,10M, and10K may be made of a cylinder, made of aluminum having a given diameter (e.g., 40 mm), and a photosensitive layer formed on the cylinder. The photosensitive layer may include an organic photo conductor (OPC), for example.

The charge units11Y,11C,11M, and11K may charge surfaces of the photoconductors10Y,10C,10M, and10K, respectively.

The developing units12Y,12C,12M, and12K may respectively develop latent images formed on the photoconductors10Y,10C,10M, and10K as toner image.

The cleaning units13Y,13C,13M, and13K may remove toners remaining on the photoconductors10Y,10C,10M, and10K, respectively.

The optical writing unit4, provided under the image forming units3Y,3C,3M, and3K, may emit a light beam L to the surface of the photoconductors10Y,10C,10M, and10K. The optical writing unit4may be used as optical scanning unit.

The intermediate transfer unit5, provided over the image forming units3Y,3C,3M, and3K, may include an intermediate transfer belt20, to which toner images are transferred from the image forming units3Y,3C,3M, and3K.

The fixing unit6may fix the toner images on a transfer sheet P, which receives the toner images from the intermediate transfer belt20.

The image forming apparatus1may further include toner bottles7Y,7C,7M, and7K over the intermediate transfer unit5as shown inFIG. 1. The toner bottles7Y,7C,7M, and7K can store toners of yellow(Y), cyan(C), magenta(M), and black(K), respectively. The toner bottles7Y,7C,7M, and7K may be removable from the image forming apparatus1by opening an ejection tray8of the image forming apparatus1.

The optical writing unit4may include a light source (e.g., laser diode) and a polygon mirror, for example.

The light source may emit the laser beam L, and the polygon mirror deflects the laser beam L. Then, the deflected laser beam L may scan surfaces of the photoconductors10Y,10C,10M, and10K. The optical writing unit4will be explained in detail later.

In the intermediate transfer unit5, the intermediate transfer belt20may be extended by a drive roller21, a tension roller22, and a driven roller23, and may be rotated in a counter-clockwise direction inFIG. 1at a given timing.

As shown inFIG. 1, the intermediate transfer unit5may include primary transfer rollers24Y,24C,24M, and24K used for transferring toner images from the photoconductors10Y,10C,10M, and10K to the intermediate transfer belt20.

As shown inFIG. 1, the intermediate transfer unit5may further include a secondary transfer roller25, which may transfer the toner images from the intermediate transfer belt20to the transfer sheet P.

The intermediate transfer unit5may further include a belt-cleaning unit26, which may remove toners remaining on the intermediate transfer belt20after the toner images are transferred from the intermediate transfer belt20to the transfer sheet P.

Hereinafter, an image forming process in the image forming apparatus1is explained.

At first, the charge units11Y,11C,11M, and11K may uniformly charge the surfaces of the photoconductors10Y,10C,10M, and10K, respectively.

Then, the optical writing unit4may scan the surfaces of the photoconductors10Y,10C,10M, and10K with the laser beam L, based on original image information, to form latent images on the surfaces of the photoconductors10Y,10C,10M, and10K.

The latent images formed on the surfaces of the photoconductors10Y,10C,10M, and10K may be developed as toner image by supplying toners from developing rollers15Y,15C,15M, and15K in the developing units12Y,12C,12M, and12K to the surface of the photoconductors10Y,10C,10M, and10K, respectively.

The toner images formed on the photoconductors10Y,10C,10M, and10K may be superimposingly transferred to the intermediate transfer belt20, rotating in a counter-clockwise direction inFIG. 1, with an effect of the primary transfer rollers24Y,24C,24M, and24K.

The primary transfer rollers24Y,24C,24M, and24K may conduct such primary transfer operation with a given timing each other so that toner images of each color can be correctly superimposed on the intermediate transfer belt20.

After such primary transfer operation, each surface of the photoconductors10Y,10C,10M, and10K may be cleaned by a cleaning blade13aof the cleaning units13Y,13C,13M, and13K, by which the photoconductors10Y,10C,10M, and10K may be prepared for a next image forming operation.

Toners stored in toner bottles7Y,7C,7M, and7K may be supplied to the developing units12Y,12C,12M, and12K in the image forming units3Y,3C,3M, and3K through a toner transport route (not shown), as required.

The transfer sheet P in the sheet cassette2may be fed to paired-registration rollers28in the image forming apparatus1by a feed roller27, provided near the sheet cassette2.

The paired-registration rollers28may feed the transfer sheet P to the second transfer roller25at a given timing so that the toner images can be transferred from the intermediate transfer belt20to the transfer sheet P.

Then, the transfer sheet P may be transported to the fixing unit6to fix toner images on the transfer sheet P, and then the transfer sheet P may be ejected to the ejection tray8by an ejection roller29.

After the toner images are transferred from the intermediate transfer belt20to the transfer sheet P, the belt-cleaning unit26may remove toners remaining on the intermediate transfer belt20.

Hereinafter, the optical writing unit4is explained in detail.

FIG. 3is a schematic configuration of the optical scanning unit4when viewed from an axis direction of photoconductor10.FIG. 4is a schematic view of lower side of the optical scanning unit4, viewed from a direction of arrow B inFIG. 3.FIG. 5is a schematic view of upper side of the optical writing unit4, viewed from a direction of arrow C inFIG. 3.

In an example embodiment, the optical writing unit4may include light source units70K,70M,70C,70Y as shown inFIGS. 4 and 5.

Each of the light source units70K,70M,70C,70Y may include a light source, which can emit writing beams Lk, Lm, Lc, and Ly. Each of the writing beams Lk, Lm, Lc, and Ly may scan the photoconductors10K,10M,10C, and10Y, respectively.

As shown inFIG. 3, the optical writing unit4may include polygon mirrors41aand41b, which have a regular polygonal shape such as hexagonal shape when viewed from an axis direction of polygon mirror.

Each of the polygon mirrors41aand41bmay have a plurality of side faces used as reflecting mirror, and may be rotated at a higher speed by a polygon motor (not shown) such as 32,000 rpm (revolution per minute), for example.

The optical writing unit4may further include lens units60Y,60C,60M, and60K having a cylindrical lens as shown inFIG. 4.

As shown inFIG. 4, the lens units60Y,60C,60M, and60K may be disposed between the light source unit70K,70M,70C,70Y and polygon mirrors41aand41b. A configuration of the lens units60Y,60C,60M, and60K will be explained later in detail.

As shown inFIGS. 3,4, and5, the optical writing unit4may include heat insulating glasses42aand42b. The heat insulating glasses42aand42bmay be a transparent member, which can insulate heat generated by the polygon motor.

The f-theta lens43aand43bmay convert a light beam deflected by the polygon mirrors41aand41bhaving equiangular motion to a light beam having uniform linear motion.

The first mirrors44a,44b,44c,44d, second mirrors46a,46b,46c,46d, third mirrors47a,47b,47c,47d, and long-shaped lens50a,50b,50c,50dmay be used to guide a writing beam (or scanning light beam) to each of the photoconductors10Y,10C,10M, and10K.

The optical writing unit4may further include dust-proof glasses48a,48b,48c, and48d. The dust-proof glasses48a,48b,48C, and48dmay reduce or suppress an intrusion of dust such as toner particles into a housing of the optical writing unit4.

As shown inFIGS. 3 to 5, the optical writing unit4may include a housing100for containing the above-mentioned parts.

Specifically, as shown inFIG. 4, the light source units70K,70M,70C, and70Y may be attached to a lower side of a support plate100aof the housing100.

Furthermore, the lower side of the support plate100amay be attached with the lens units60Y,60C,60M, and60K having a cylindrical lens61, f-theta lenses43a,43b, and first mirrors44a,44b,44c, and44d.

Furthermore, the lower side of the support plate100amay be attached with the long-shaped lens50afor Y color and long-shaped lens50dfor K color.

On one hand, an upper side of the support plate100amay be attached with a long-shaped lens50cfor M color and a long-shaped lens50bfor C color.

The long-shaped lens50a,50b, and50cmay have a holder, with which the long-shaped lens50a,50b, and50cmay be attached on the housing100. The long-shaped lens50a,50b, and50cmay be tilted for some degree so that an outgoing angle of laser beam from the long-shaped lens50a,50b, and50cmay be adjustable.

The long-shaped lens50afor K color may be fixed on the upper side face of the support plate100adirectly.

With such configuration, in an example embodiment, an outgoing angle of writing beam (or scanning light beam) from the long-shaped lens50a,50b, and50cmay be adjusted by referring the writing beam (or scanning light beam) for K color as a reference beam.

Furthermore, the second mirrors46a,46b,46c,46dand third mirrors47a,47b,47c,47dmay be attached to the housing100, which may be over the upper side of the support plate100aas shown inFIG. 3.

Furthermore, as shown inFIG. 3, the support plate100amay include a dented portion to install the polygon mirrors41aand41b. The dented portion may be referred as container110, hereinafter.

As shown inFIG. 4, the container110may have the heat insulating glass42on side walls of the container110, wherein the heat insulating glass42may be disposed between the polygon mirrors41a,41band the lens units60Y,60C,60M,60K.

The polygon mirrors41aand41bmay be attached to the container110with a screw, for example.

As shown inFIG. 3, the housing100may include an upper cover120and a lower cover130.

The upper cover120may be attached on an upper side of the housing100, and the lower cover130may be attached on a lower side of the housing100.

As shown inFIG. 3, the upper cover120may be provided with openings to pass through the writing beam Ly, Lc, Lm, and Lk to the photoconductors10Y,10C,10M, and10K, respectively. The openings may be covered with the dustproof glasses48a,48b,48c, and48d.

The housing100, covered by the upper cover120and lower cover130, may reduce an intrusion of dust into the optical writing unit4, by which optical parts in the optical writing unit4such as lens and mirror may be less likely to be contaminated by dust such as toner particles.

The upper cover120and lower cover130may be made of resinous material, sheet metal, or the like, for example.

The optical writing unit4may have the light source units70Y,70C,70M, and70K, which emit the respective writing beams Ly, Lc, Lm, and Lk based on a signal generated from an original image data.

Such original image data may be input to the image forming apparatus1from a scanner (not shown), personal computer or the like, for example.

Then, the writing beams Ly, Lc, Lm, and Lk may pass through a collimate lens (not shown) and an aperture (not shown) provided on a wall of the housing100.

After passing through the aperture, the writing beams Ly, Lc, Lm, and Lk may pass through the cylindrical lens61of the lens units60Y,60C,60M, and60K, and then may pass through the heat insulating glass42, and may enter a reflection face of the polygon mirrors41aand41b.

The writing beams Ly, Lc, Lm, and Lk may be deflected by the polygon mirrors41aand41b, rotated by the polygon motor. Such writing beams Ly, Lc, Lm, and Lk may be used as scanning light beam for scanning each of the photoconductors10Y,10C,10M, and10K.

Then, the writing beams (or scanning light beams) Ly, Lc, Lm, and Lk may pass through the f-theta lenses43aand43b.

The writing beams Lk for K color may pass through the long-shaped lens50d, and then may reflect on the first lens44d, second lens46d, third lens47d, and then may pass through the dustproof glass48d. Then, the writing beams Lk may scan the photoconductor10K to form a latent image for K color on the photoconductor10K.

In a similar way, the writing beams Ly for Y color may pass through the long-shaped lens50a, and then may reflect on the first lens44a, second lens46a, third lens47a, and then may pass through the dustproof glass48a. Then, the writing beams Ly may scan the photoconductor10Y to form a latent image for Y color on the photoconductor10Y.

The writing beam Lm for M color may pass through the long-shaped lens50cvia the first lens44c, and then may reflect on the second lens46c, third lens47c, and may pass through the dustproof glass48c. Then, the writing beams Lm may scan the photoconductor10M to form a latent image for M color on the photoconductor10M.

In a similar way, the writing beam Lc for C color may pass through the long-shaped lens50bvia the first lens44b, and then may reflect on the second lens46b, third lens47b, and may pass through the dustproof glass48b. Then, the writing beams Lc may scan the photoconductor10C to form a latent image for C color on the photoconductor10C.

Hereinafter, an adjustment work for adjusting position of cylindrical lens61along a direction substantially parallel to a reference-axis is explained.

FIG. 6is a schematic configuration of the optical scanning unit4(including housing100, etc.) when viewed from an axis direction of photoconductor10, in which the optical scanning unit4is placed on the platform200of an adjustment machine (not shown).

In an example embodiment, the optical writing unit4may be placed on the platform200with a posture or orientation, which is substantially similar to a posture or orientation of the optical writing unit4installed in the image forming apparatus1(seeFIGS. 1 and 3).

After placing the optical writing unit4on the platform200with such posture or orientation, light detectors201Y,201C,201M, and201K may be disposed over the optical writing unit4at a given position, respectively, as shown inFIG. 6.

Specifically, the light detectors201Y,201C,201M, and201K may be disposed at a given position, which corresponds to a position for each surface of the photoconductors10Y,10C,10M, and10K when the optical writing unit4is installed in the image forming apparatus1.

In other words, instead of the photoconductors10Y,10C,10M, and10K, the light detectors201Y,201C,201M, and201K may be disposed in a configuration shown inFIG. 6, respectively, which may be understood by comparing configurations shown inFIGS. 3 and 6.

The light detectors201Y,201C,201M, and201K may include a CCD (charge-coupled device), for example.

Specifically, as one example, three detectors may be used for light detector201Y: one detector may be disposed at an each end portion of the axis direction of photoconductor10Y, and one detector may be disposed at a center portion of the axis direction of photoconductor10Y. Although the photoconductor10Y may not exist in a configuration inFIG. 6, the phrase of “axis direction of photoconductor10Y” may be used for the clarity of explaining of the positions of the light detector201Y.

As similar to the light detector201Y, e.g., three detectors may be used for each of light detectors201C,201M, and201K with a similar configuration. However, a number of light detectors and position of light detectors may be changed, as required.

As shown inFIG. 6, the light detectors201Y,201C,201M, and201K may be connected to a control unit202of the adjustment machine.

The light detectors201Y,201C,201M, and201K may detect respective light beams coming form the optical writing unit4, and may transmit detection results such as received light-intensity and beam-spot diameter to the control unit202as detection signal.

The control unit202may conduct a plurality of computations based on received detection signal and may continuously display information, corresponding to the detection signal, on a display unit203with a substantially real time manner.

For example, the control unit202may receive detection signals (e.g., corresponding to light-intensity and beam-spot diameter detected by the light detectors201Y,201C,201M, and201K) from the light detectors201Y,201C,201M, and201K, and may display information, corresponding to detection signals, on the display unit203as lens-position-adjustment information with a substantially real time manner.

With such configuration, a maintenance person can conduct an adjustment work for adjusting a position of cylindrical lens61to an appropriate position while checking or looking up the lens-position-adjustment information displayed on the display unit203.

FIG. 7is a schematic perspective view of upper side of the optical scanning unit4placed on the platform200of the adjustment machine, in which a plurality of parts, e.g., light source unit70and polygon mirrors41aand41b, related to a light path are shown.

FIG. 8is a schematic perspective view of lower side of the optical scanning unit4placed on the platform200of the adjustment machine.

InFIGS. 7 and 8, some portions of the support plate100aof the housing100may be omitted from the drawing for the purpose of simplicity of explanation.

Furthermore, because the lens units60Y,60C,60M, and60K may take a similar configuration one another, the lens unit60may be used hereinafter for the purpose of simplicity of explanation.

In an example embodiment, the optical writing unit4may be placed on the platform200of the adjustment machine with a posture or orientation, which is substantially similar to a posture or orientation when the optical writing unit4is installed in the image forming apparatus1(seeFIGS. 1 and 3).

Accordingly, the light source unit70, collimate lens71, cylindrical lens61on the lens unit60may be positioned on a lower side of the support plate100aof the housing100as shown inFIGS. 7 and 8.

As shown inFIGS. 7 and 8, the lens unit60may include a movable lens holder62for holding cylindrical lens61, and a lens adjuster63, for example.

The lens adjuster63may be used to adjust a movement of the lens holder62in a reference-axis direction D of the cylindrical lens61, the reference-axis being defined between the light source unit70and the polygon mirrors41aand41b.

The lens adjuster63may include an adjusting member63a, which is provided on an upper side of the support plate100a, wherein a maintenance person may operate the adjusting member63awith a driver (e.g., of a hand-held variety)160.

As shown inFIGS. 7 and 8, the lens holder62may be disposed on the lower side of the support plate100a, and the adjusting member63amay be disposed so as to be accessible from the upper side of the support plate100a, e.g., by being disposed on the upper side.

In an example embodiment, a maintenance person may rotate the adjusting member63awith the driver160to move the lens holder62; as a consequence, the cylindrical lens61is moved in a direction along the reference-axis, which is indicated by an arrow D inFIG. 8. Such configuration and movement will be explained later in detail. The combination including the lens holder62and the cylindrical lens61occupies/consumes a first volume in space. The combination also has a range of motion along the reference-axis. The range can be described in terms of a length measured along the reference-axis relative to a reference point thereon. At any position in the range, the combination will consume/occupy an amount of space equal to the first volume. To ensure unrestricted movement throughout the range of motion, a second volume of open space (i.e., a space that can be occupied) should be provided. Depending upon where the reference point is established, the second volume can be determined, e.g., as a product of the first volume multiplied by the length, or as a product of the first volume multiplied by an adjusted value of the length, etc. The second volume can be described as an occupiable space in the sense that the combination can be moved through the occupiable space and (at any given position along the range of motion) can consume/occupy a portion of the occupiable space, the portion being equal to the first volume.

In general, an adjustment work for adjusting a position of the cylindrical lens61in its reference-axis direction at an appropriate position may need to be conducted with a highly precise manner.

Therefore, it can be beneficial to make adjustment work, associated with positioning the cylindrical lens61, easier and simplified.

In an example embodiment, the adjusting member63amay be positioned so as to be accessible from the upper side of the support plate100a(e.g., the adjusting member63amay be disposed on the upper side of the support plate100a) as shown inFIGS. 7 and 8.

Accordingly, a maintenance person can operate the adjusting member63awith the driver160from an upper side of the support plate100a.

Therefore, the maintenance person may operate the adjusting member63awith an easier manner compared to a hypothetical configuration (not shown) that would dispose the adjusting member63aat the lower side of the support plate100a.

Furthermore, in a configuration according to an example, the cylindrical lens61may be positioned at the lower side face of the support plate100aas shown inFIGS. 7 and 8when the maintenance person may conduct an adjustment work.

Accordingly, an incident light, which may enter the cylindrical lens61, and an outgoing light, which may outgo from the cylindrical lens61, may pass or go through an underside of the support plate100a.

Therefore, the maintenance person, while using the driver160for operating the adjusting member63a, may avoid blocking a light-path for the incident light and outgoing light of the cylindrical lens61with the driver160.

With such configuration, when the maintenance person conducts an adjustment work for positioning the cylindrical lens61in its reference-axis direction, the maintenance person may conduct following operations with an easier and effective manner as below.

Specifically, the maintenance person may rotate the adjusting member63awith the driver160while checking or looking-up the lens-position-adjustment information displayed on the display unit203to find an appropriate positioning of the cylindrical lens61in its reference-axis direction.

Accordingly, a working efficiency of the adjustment work for the cylindrical lens61may be enhanced.

In an example embodiment, the optical writing unit4may be placed on the platform200of the adjustment machine as shown inFIG. 6when it is desired to conduct an adjustment work of the cylindrical lens61in its reference-axis direction.

Under such configuration shown inFIG. 6, the polygon mirrors41aand41bmay deflect a scanning light beam. Then, such scanning light beam may reflect at the first mirrors44a,44b,44c,44d, the second mirrors46a,46b,46c,46d, and the third mirrors47a,47b,47c,47d.

With such reflection at the mirrors, such scanning light beam may pass through the upper side of the support plate100a(seeFIG. 6) and then reaches the light detectors201Y,201C,201M, and201K.

Depending on a positional relationship of the adjusting member63aand a light-path for the optical writing unit4, such scanning light beam may happened to be partially blocked by the driver160.

However, in an example embodiment, the light detector201may not detect the scanning light beam in an entire length of the axial direction of the photoconductor10, but instead may detect the scanning light beam at three portions (e.g., both end portion and center portion of the photoconductor10) as one example as above-mentioned.

Based on detection results from fewer than all, e.g., 2 out of 3, detectors of the light detector201, lens-position-adjustment information may be displayed on the display unit203, and a maintenance person may conduct an adjustment work while checking or looking-up the lens-position-adjustment information.

In such configuration, the driver160may block a part of the scanning light beam when conducting an adjustment work of the cylindrical lens61without completely interrupting the generation and display of lens-position-adjustment information. Such robust operation is possible because the scanning light beam may be detected at separate portions (e.g., three portions in example embodiment) in the axial direction of the photoconductor10as above-mentioned, wherein such portions may be spaced apart from each other.

However, such blocked portion by the driver160can be set to a portion, which can avoid the light-path of scanning light beam over the support plate100a.

Accordingly, when a positional relationship of adjusting member63aand light-path of scanning light beam may be set to a configuration that the light detector120can detect scanning light beam without a blocking effect of the driver160when conducting an adjustment work of the cylindrical lens61, an maintenance person may conduct such adjustment work effectively and efficiently.

Although not shown, the driver160may be inserted to the adjusting member63aof the lens adjuster63without opening the upper cover120, for example. In such a case, the upper cover120may have an opening at a position over the adjusting member63a. Such opening may be covered by a cover (not shown) during a normal image forming operation, and may be opened when conducting the above-described adjustment work.

Hereinafter, the lens unit60is explained in detail with reference toFIG. 9.FIG. 9is a schematic cross sectional view of the optical scanning unit4, in which a positioning of the lens unit60is shown.

In an example embodiment, the lens holder62may hold the cylindrical lens61while constantly contacting a face of the cylindrical lens61to a lens-receiving face100b.

As shown inFIG. 9, the lens-receiving face100bmay be provided at a lower side of the support plate100aof the housing100.

In an example embodiment, the lower side of the support plate100amay include two lens-receiving faces100b, formed in a parallel direction of the reference-axis direction of the cylindrical lens61, for example.

Accordingly, the two lens-receiving faces100bmay contact with a plurality of contact faces of the cylindrical lens61. Such plurality of contact faces of the cylindrical lens61may be referred as contact face of the cylindrical lens61, hereinafter, as required.

In example embodiment, the lens holder62, holding the cylindrical lens61, may be attached to the support plate100awhile the lens holder62may be movable in a reference-axis direction of the cylindrical lens61.

The lens holder62may be moved in a reference-axis direction of the cylindrical lens61shown by an arrow D inFIG. 9by rotating the adjusting member63a(not shown inFIG. 9, but seeFIG. 7). Such direction shown by an arrow D may be referred as reference-axis direction D, hereinafter, as required.

During a movement of the lens holder62in the reference-axis direction D, the contact face of the cylindrical lens61may maintain a contact condition with the lens-receiving face100b.

In other words, when the lens holder62is moved in the reference-axis direction D, the cylindrical lens61may remain in contact while slidably moving on the lens-receiving face100b.

In an example embodiment, a higher precision lens-receiving face100bmay be made with a fine surface finishing.

If the lens-receiving face100bis formed with a higher precision, the cylindrical lens61may be regulated and positioned relative to the lens-receiving face100bin a more precise manner when the lens holder62is moved.

Such configuration may enhance a precision of light reference-axis alignment of light source units70, cylindrical lens61, and polygon mirrors41aand41b.

In such configuration, a lens focal line of cylindrical lens61and a scanning face of polygon mirrors41aand41bmay be precisely aligned with each other over time.

If the lens focal line of cylindrical lens61and scanning face of polygon mirrors41aand41bmay not be aligned in a precise manner with each other, an optical property of the light beam may degrade (e.g., unfavorably larger beam-spot diameter).

In an example embodiment, the lens focal line of cylindrical lens61and scanning face of polygon mirrors41aand41bmay be better aligned by more precisely positioning the cylindrical lens61.

In an example embodiment, the cylindrical lens61may be more precisely positioned when the cylindrical lens61is moved in its reference-axis direction D to better maintain alignment of the lens focal line of cylindrical lens61and scanning face of polygon mirrors41aand41b.

Although not shown, in a hypothetical case, an intervening part may be disposed between the cylindrical lens61and the lens-receiving face10b, wherein the lens-receiving face100bmay be used for determining the positioning of the cylindrical lens61.

If a number of such intervening parts may become greater, dimensional error of each intervening part may be accumulated, and an assembly error of intervening parts may also be accumulated. If such error becomes greater, the cylindrical lens61may not be correctly positioned.

In an example embodiment, the cylindrical lens61may contact the lens-receiving face100b(used as reference face for positioning) directly.

In other words, the cylindrical lens61and lens-receiving face100bmay contact each other without interposing an intervening part therebetween.

Therefore, in an example embodiment, the cylindrical lens61may be positioned with a higher precision manner compared to a configuration (not shown) having an intervening part between the cylindrical lens61and lens-receiving face100b.

FIG. 10is an expanded view of the cylindrical lens61and the lens-receiving face100b, which may contact each other.

In an example embodiment, the cylindrical lens61may slidably move on the lens-receiving face100bin the reference-axis direction D shown inFIG. 10by rotating the adjusting member63awith the driver160(seeFIG. 7).

In an example embodiment, the housing100and lens-receiving face100bmay be made of resinous material in view of reducing manufacturing cost.

If the cylindrical lens61may have a contact face having a sharp edge portion, such cylindrical lens61may scrape the lens-receiving face100bfor some amount when the cylindrical lens61slidably moves on the lens-receiving face100bin the reference-axis direction D inFIG. 10.

If the cylindrical lens61may slidably move on the lens-receiving face100brepeatedly, the lens-receiving face100bmay be scraped more and more, and resultantly, such scraped lens-receiving face100bmay cause a precision degradation of positioning of the cylindrical lens61.

In view of such drawback, in an example embodiment, an edge portion of contact face of the cylindrical lens61may receive a chamfering or rounding process so that the contact face of the cylindrical lens61may have a C-face or R-face at the edge portion, wherein the C-face may mean a chamfered face and R-face may mean a rounded face as shown inFIG. 10.

With such chamfering or rounding process to the contact face of the cylindrical lens61, a scraping effect of the cylindrical lens61to the lens-receiving face100bmay be reduced compared to a cylindrical lens having no chamfering or rounding process to its contact face.

Accordingly, even if the cylindrical lens61may slidably move on the lens-receiving face100bin the reference-axis direction shown by an arrow D inFIG. 10repeatedly, the cylindrical lens61may be positioned with a higher precision over time. In other words, a positioning precision of the cylindrical lens61may not degrade over time.

FIG. 11Ais an upper perspective view of the adjusting member63aof lens adjuster63, viewed from an upper side of the support plate110a. In other words, a maintenance person may see the adjusting member63aof lens adjuster63in an angle shown inFIG. 11A.

FIG. 11Bis a lower perspective view of the adjusting member63aof lens adjuster63, viewed from a lower side of the support plate110a.

FIG. 12Ais an upper perspective view of the lens holder62, viewed from an upper side of the support plate110a.FIG. 12Bis a lower perspective view of the lens holder62, viewed from a lower side of the support plate110a.

As shown inFIGS. 11A and 11B, the lens adjuster63may include the adjusting member63a, a base63b, a center-axis shaft63c, an eccentric shaft63d, for example.

The base63bmay be rotatable by a force applied to the adjusting member63a.

The center-axis shaft63cmay extend from the base63bin a direction along the rotational center axis of the base63b.

The eccentric shaft63dmay extend from the base63bin a direction, deviated and parallel to the rotational center axis of the base63b(seeFIG. 11B).

As shown inFIG. 11A, the base63bmay include the adjusting member63a, which receive the driver160, at the upper side of the base63b.

When the driver160rotates the adjusting member63a, the center-axis shaft63cmay rotate around a rotational center axis of the base63b.

Then, the eccentric shaft63dmay rotate eccentrically around the rotational center axis of the base63b.

In an example embodiment, the lens adjuster63may be made of resinous material such as polyacetal resin, but not limited to polyacetal resin.

If the lens adjuster63is made of resinous material such as polyacetal resin, the lens adjuster63may receive a relatively smaller abrasion effect by friction when an adjustment work of the cylindrical lens61is conducted.

As described later, the lens adjuster63may contact the lens holder62and support plate100a, by which the lens adjuster63may friction with the lens holder62and support member100.

With such configuration using resinous material, an adjustment work of the cylindrical lens61may be conducted with a higher precision manner over time.

As shown inFIGS. 12A and 12B, the lens holder62may include a holder base62a, and a lens receiver62b, for example.

The holder base62amay be attached to the lower side of the support plate100a.

The lens receiver62bmay be protruded from a face of the holder base62aas shown inFIG. 12B.

The cylindrical lens61may be pressed to a contacting face62cof the lens receiver62b, and then be held to the lens holder62with a fixing member (to be explained later).

In an example embodiment, a light-outgoing face of the cylindrical lens61may be pressed to the contacting face62c.

As shown inFIGS. 12A and 12B, the holder base62amay include an adjustment hole62d.

The adjustment hole62dmay have a substantially oblong or rectangular shape, a long axis of which is extended in a direction perpendicular to the above-mentioned reference-axis direction D. As above explained, the lens holder62may be moved in the reference-axis direction D.

The eccentric shaft63dmay be inserted into the adjustment hole62d.

A width of the adjustment hole62dmay mean a width in the reference-axis direction D of the holder base62a. Such width of the adjustment hole62dmay set to a value substantially corresponding to a dimension of the eccentric shaft63d, or set to a value which is slightly larger than a diameter of the eccentric shaft63d.

Furthermore, the holder base62amay be provided with a guide62eprotruded from the holder base62aas shown inFIGS. 12A and 12B.

In an example embodiment, the lens unit60may be assembled and attached to the support plate100aas below.

At first, the cylindrical lens61may be held onto the lens holder62.

Then, the guide62emay be engaged to a guide hole (not shown) provided to the support plate100awith a snap-fit manner.

Such guide hole, formed in the support plate100amay have a substantially oblong figure, which is extended in the reference-axis direction D of the cylindrical lens61. A width of the guide hole may be set to a value corresponding to a thickness of the guide62e.

With such configuration, the lens holder62may be attached to the lower side face of the support plate100aas shown inFIGS. 9 and 13, and may be movable in the reference-axis direction D of the cylindrical lens61.

Then, the lens adjuster63having the adjusting member63amay be fitted in a bearing hole100g(seeFIG. 9) in the support plate100a.

Specifically, the center-axis shaft63cof the lens adjuster63may be inserted into the bearing hole100gfrom an upper side of the support plate100afrom a direction shown by an arrow E inFIG. 11A.

At this time, the eccentric shaft63dof the lens adjuster63may be inserted into the adjustment hole62dof the lens holder62from a direction shown by an arrow E inFIG. 12A, by which the eccentric shaft63dmay be inserted and snap-fitted into the adjustment hole62d.

With such process, the lens unit60may be assembled and attached to the support plate100a.

When the adjusting member63ais rotated under such configuration, the lens adjuster63may rotate while the center-axis shaft63cis supported by the bearing hole100gof the support plate100a.

Then, with a rotation of the lens adjuster63, the eccentric shaft63dmay rotate eccentrically around the rotational center axis of the base63b.

Then, with a rotation of the eccentric shaft63d, the eccentric shaft63dmay contactingly push an inner wall of the adjustment hole62dof lens holder62.

Then, with such pushing movement in the adjustment hole62dby the eccentric shaft63d, the guide62eof lens holder62may be moved in the guide hole, formed in the support plate100a.

With such process, the lens holder62may move reciprocally along the reference-axis direction D of the cylindrical lens61under the lower side of the support plate100a.

In an example embodiment, the lens holder62and lens adjuster63may be assembled to the support plate100awith a snap-fit process. The snap-fit process may reduce a time required for assembling or removing parts compared to a screw-fitting process or the like.

With such assembly process requiring less time for assembly, the lens unit60may be assembled to the support plate100awith an enhanced working efficiency.

Furthermore, even if the cylindrical lens61may be contaminated or scratched, the cylindrical lens61may be replaced more easily in the above-described assembly configuration.

In an example embodiment, the adjusting member63amay have a shape that can be operated by the driver160. However, the adjusting member63acan take another shape such as hexagonal shape that can be operated by a wrench, for example.

Furthermore, in an example embodiment, the lens holder62may have a coefficient of linear expansion of about 1.0×10−5(1/° C.) or less, for example.

Because the cylindrical lens61may be disposed closely to the polygon mirrors41aand41b, the lens holder62also be disposed closely to the polygon mirrors41aand41bas shown inFIG. 9.

Because the polygon motor for driving the polygon mirrors41aand41bmay generate a relatively greater amount of heat, the lens holder62, disposed closely to the polygon mirrors41aand41b, may be susceptible to such generated heat.

If the heat generated at the polygon mirrors41aand41bmay affect the lens holder62, a position of the cylindrical lens61may be deviated from an appropriate position. For example, such heat effect may deform the contacting face62cof the lens holder62.

In view of such heat effect, in an example embodiment, the lens holder62may have the coefficient of linear expansion of about 1.0×10−5(1/° C.) or less so that heat generated at the polygon mirrors41aand41bmay not affect a positioning of the cylindrical lens61.

In other words, such heat effect may be controlled within a practical rage for realizing an appropriate positioning of the cylindrical lens61.

The lens holder62having the coefficient of linear expansion of about 1.0×10−5(1/° C.) or less may be manufactured from a resinous material such as polycarbonate (PC), for example. Such resinous material may be preferable from a viewpoint of reducing manufacturing cost and enhancing mass produce-ability.

Hereinafter, a retaining mechanism for retaining the cylindrical lens61in the lens holder62is explained.

FIG. 13is a schematic view for explaining a retaining mechanism for retaining the cylindrical lens61in the lens holder62.FIGS. 14A and 14Bare example perspective views of a fixing member64, which may configure the retaining mechanism.

In an example embodiment, as shown inFIG. 13, the light-outgoing face of the cylindrical lens61may contact the contacting face62cof the lens holder62.

Then, as shown inFIG. 13, the light-incoming face of the cylindrical lens61may be biased with the fixing member64such as leaf spring with a first biasing (e.g., resiliently biasing) force Fx.

With such first biasing force Fx, a position of the cylindrical lens61in its reference-axis direction D may be determined while pressing the light-outgoing face of the cylindrical lens61to the contacting face62c.

Furthermore, the cylindrical lens61may be biased toward the lower side of the support plate100awith the fixing member64with a second biasing (e.g., resiliently biasing) force Fz.

With such second biasing force Fz, a position of the cylindrical lens61in a normal line direction of the support plate100amay be determined.

If an external shock (e.g., an impulse force) may occur to the optical writing unit4or image forming apparatus1, contact between the cylindrical lens61and the lens-receiving face100bmay temporarily become broken/interrupted, and then the positioning of the cylindrical lens61in the normal line direction of the support plate100amay be deviated from an appropriate position.

Such external shock may occur to the optical writing unit4or image forming apparatus1if a person may drop the optical writing unit4or image forming apparatus1carelessly, for example.

In an example embodiment, the cylindrical lens61may more likely to be effected by a gravity effect due to a configuration of an example embodiment, and such gravity effect may cause the cylindrical lens61to leave from the lens-receiving face100bmore or less.

Under such configuration, the positioning of the cylindrical lens61in the normal line direction of the support plate100amay be deviated from an appropriate position.

In view of such situation, in an example embodiment, the fixing member64may be configured to set the second biasing force Fz effectively greater than the first biasing force Fx.

The second biasing force Fz may press the cylindrical lens61toward the lens-receiving face100b.

The first biasing force Fx may press the cylindrical lens61toward the contacting face62cof the lens receiver62b.

Specifically, following two forces may be assumed to realize an appropriate positioning of the cylindrical lens61.

A first force may be defined as a total static friction of the lens receiver62b, fixing member64, and cylindrical lens61. The first force may be generated in a reference-axis direction of the cylindrical lens61.
First force=(total static friction of members)

A second force may be defined with the second biasing force Fz of the fixing member64and a self-weight of the cylindrical lens61.

Specifically, the second force may be defined by subtracting a self-weight of the cylindrical lens61from the second biasing force Fz.
Second force=(Fz)−(self-weight of cylindrical lens61)

Therefore, the above-explained two forces may have a following relationship for realizing an appropriate positioning of the cylindrical lens61.
Second force>First force

With such relationship, even if contact between the cylindrical lens61and the lens-receiving face100bmay become disrupted, the second biasing force Fz of the fixing member64may push back the cylindrical lens61toward the lens-receiving face100bso as to restore the contact.

With such configuration, even if an external shock temporarily disrupts contact between the cylindrical lens61and the lens-receiving face100bof the optical writing unit4, the cylindrical lens61may be returned to a contact condition with the lens-receiving face100b.

Accordingly, a position of the cylindrical lens61in the normal line direction of the support plate100amay be maintained at an appropriate position.

As shown inFIG. 14A, the fixing member64may have a configuration having a pressing member64ato press a center portion of bottom side of the cylindrical lens61toward the lens-receiving face100b, for example.

Furthermore, as shown inFIG. 14B, the fixing member64may have another configuration having two pressing members64bto press each end portion of bottom side of the cylindrical lens61toward the lens-receiving face10b, for example.

In general, the more the number of pressing members, the better the positioning of the cylindrical lens61in the normal line direction of the support plate100a. The number of pressing members may be determined by considering several factors.

In an example embodiment, the lens holder62and fixing member64may be manufactured as separate parts. However, the lens holder62alone may include a function similar to the fixing member64, as required.

Furthermore, in an example embodiment, a configuration for moving the lens holder62has a following feature as shown inFIG. 9.

In recent years, an image forming apparatus may be manufactured with a concept of further miniaturization. Accordingly, each part may be preferably manufactured smaller and smaller.

In case of configuration for moving the lens holder62, the lens holder62may need or occupy a relatively larger space. Therefore, a miniaturization of the lens holder62may be considered when designing a miniaturization of an optical unit and image forming apparatus. In addition, a miniaturization of the lens adjuster63may also be considered.

In an example, as shown inFIGS. 9 and 13, an occupiable space SP of the lens holder62in the reference-axis direction D may be considered because such occupiable space SP may occupy a relatively larger space under the lower side of the support plate100a.

The occupiable space SP, shown by a dot line inFIGS. 9 and 13, may have a given volume, which may be determined by several designing factors. Although not shown inFIGS. 9 and 13, the occupiable space SP may have an imagined three-dimensional shape when viewing the lens holder62in the reference-axis direction D. For example, such imagined three-dimensional shape may be an imagined rectangular parallelepiped shape, for example.

In view of miniaturization of an optical unit and image forming apparatus, a size of the lens holder62may be reduced, by which the occupiable space SP of the lens holder62may be reduced.

Under such condition, a design work may be conducted to limit a space required for lens adjuster63to be within such occupiable space SP of the lens holder62.

For example, as shown inFIG. 11B, the lens adjuster63has a snap-edge63eat the end of the eccentric shaft63d.

If such snap-edge63emay not be within the occupiable space SP of the lens holder62(i.e., the snap-edge63emay be out of the occupiable space SP), a miniaturization of the configuration for moving the lens holder62may not be realized.

In an example embodiment, a size of the snap-edge63emay be set within the occupiable space SP of the lens holder62under the lower side of the support plate100aas shown inFIGS. 9 and 13.

With such designing, a configuration for moving the lens holder62under the lower side of the support plate100amay be preferably miniaturized, by which a space-saving of an image forming apparatus may be enhanced.

Furthermore, in an example embodiment, the cylindrical lens61may be tilted for a given degrees as shown inFIG. 15to adjust a normal line direction of a light-incoming face of the cylindrical lens61with respect to a direction of light beam coming form the light source unit70Y,70M,70C, and70K.

In an example embodiment, a controller (not shown) may detect electric current, which runs in a laser diode in the light source unit70Y,70M,70C, and70K.

Then, the controller may control the laser diode with a feedback control method based on detection results of electric current of the laser diode so that the laser diode may emit a light beam having a stabilized light intensity over time.

If a light-beam emitting direction of the light source unit70Y,70M,70C, and70K and the normal line direction of the light-incoming face of the cylindrical lens61may be aligned in a substantially similar direction, a reflecting light LR reflecting on the light-incoming face of the cylindrical lens61may enter the light source unit70Y,70M,70C, and70K.

If such condition may occur, the controller may not be able to control the light source unit70Y,70M,70C, and70K with a feedback control method, by which a light-output of the light source unit70Y,70M,70C, and70K may be destabilized.

In view of such condition, in an example embodiment, the cylindrical lens61may be tilted for a given degrees as shown inFIG. 15to adjust the normal line direction of the light-incoming face the cylindrical lens61with respect to a direction of light beam coming form the light source unit70Y,70M,70C, and70K.

Specifically, the normal line direction of the light-incoming face the cylindrical lens61may be slanted with respect to the direction of light beam coming form the light source unit70Y,70M,70C, and70K.

With such configuration, the reflecting light LR reflecting on the light-incoming face of the cylindrical lens61may not enter the light source unit70Y,70M,70C, and70K, by which the controller may control the light source unit70K,70M,70C,70Y with a feedback control method so that the light source unit70K,70M,70C,70Y may emit a light beam having a stabilized light intensity over time.

Furthermore, in an example embodiment, the heat insulating glass42may be provided between the cylindrical lens61and polygon mirrors41aand41b. Accordingly, heat generated at the polygon mirrors41aand41bmay not be transmitted to the cylindrical lens61, and thereby a positioning of the cylindrical lens61may be effectively conducted by reducing heat effect from the polygon mirrors41aand41b.

Numerous additional modifications and variations are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the disclosure of the present invention may be practiced otherwise than as specifically described herein.