JP2001270152A - Scanning optical unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a scanning optical unit which can form a color image having no color shift. SOLUTION: In a tandem scanning optical unit, the charge transport layer in photosensitive drums 51-54 for respective color components is formed of a first CTL 5c having sensitivity in a first wavelength and a second CTL 5d having sensitivity in a second wavelength. Scanning lines of identical shape are formed on respective photosensitive drums 51-54 by means of a laser beam L of second wavelength. Furthermore, entire region of scanning lines is irradiated intermittently with light of first wavelength from each modulation light source E1-E4. Since the first CTL 5c and the second CTL 5d become conductors on each photosensitive drum 51-54 at the spot positions of laser beams L1-L4 at a moment when the modulation light sources E1-E4 are turned on. Consequently, previously imparted surface charges are lost and an electrostatic image is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a so-called tandem scanning optical device used for a color laser printer or the like.

[0002]

2. Description of the Related Art A tandem scanning optical apparatus includes a plurality of photosensitive drums provided for each color component, and a plurality of scanning optical systems for forming scanning lines on each photosensitive drum. . The image forming apparatus including the tandem scanning optical device performs color printing by multiply developing an image formed for each color component on each photosensitive drum on one sheet. .

Usually, four photosensitive drums are provided corresponding to the respective color components of yellow, magenta, cyan, and black (YMCK). The tandem scanning optical device scans a laser beam individually in correspondence with each color component of YMCK, and forms an image of each color component of YMCK on each photosensitive drum, thereby performing color printing. Image forming speed.

[0004]

In such a tandem scanning optical device, a plurality of (normally four) laser diodes or the like corresponding to each color component are required, and each of these light sources is provided separately. In addition, a collimator lens for converting a laser beam emitted from the light source into parallel light and a complicated optical system for forming an image of the laser beam emitted from the collimator lens on a photosensitive drum are required.

For example, a set of a light source, a polygon mirror for deflecting a laser beam emitted from the light source, and an fθ lens for forming an image of the laser beam deflected by the polygon mirror on a photosensitive drum is provided for each color component. A scanning optical device provided with four sets is known. However, the configuration of this scanning optical device is complicated because a plurality of sets of light sources, polygon mirrors, and fθ lenses are required. In addition, since separate light sources, polygon mirrors, and fθ lenses are used for each color component, it is difficult to match the shapes of the scanning lines formed on each photosensitive drum.

There is also known a scanning optical system including a single polygon mirror for simultaneously scanning laser beams emitted from a plurality of light sources. It is conceivable that this scanning optical system is further improved so that the front lens of the fθ lens constituted by a plurality of lenses is a lens common to each color component. With such a configuration, since each laser beam is guided together by the common polygon mirror and lens, it is considered that the shapes of the scanning lines formed on each photosensitive drum are likely to match each other.

However, even in such a scanning optical device, the following problem arises because an individual light source is used for each color component. That is, since the laser beam emitted from each light source passes through the same lens, it is desirable that the wavelength is the same.For example, in the case of a laser diode, even if the same product, the wavelength band of the laser beam is different due to individual differences. different. Moreover, the laser diode is
Even for the same individual, the wavelength band of the laser beam changes depending on conditions such as temperature. As described above, when the wavelength bands of the laser diodes emitted from the respective light sources are different from each other, the shapes of the scanning lines formed on the respective photosensitive drums are different from each other due to chromatic aberration of magnification in the lens.

That is, although the degree varies depending on the method, in general, in a conventional tandem scanning optical device,
It is difficult to match the shapes of the scanning lines formed on each photosensitive drum with high accuracy. If the shapes of the scanning lines do not match each other, there is a problem that a color shift occurs in the obtained print result.

It is an object of the present invention to provide a scanning optical device capable of forming a high-precision color image by making the shapes of the scanning lines coincide with each other with a simple configuration.

[0010]

The scanning optical device according to the present invention employs the following configuration in order to solve the above problems.

That is, in the scanning optical device of the present invention, a charge generation layer (CGL) generates charges.
r), a charge transport layer (CT) formed on the charge generation layer
L: In a scanning optical apparatus including a photoconductor having a carrier transport layer (L) and a charger (main charger) for uniformly charging the surface of the photoconductor, the charge transport layer of the photoconductor includes a first charge transport layer. Charge transport layer (CT) sensitive to
L) and a second charge transport layer (CTL) having sensitivity to the second wavelength, and a light source unit for emitting a laser beam, and a deflector for deflecting and scanning the laser beam emitted from the light source unit A scanning optical system for forming a scanning line on the photosensitive member by using the laser beam deflected and scanned by the deflector; and a predetermined optical system for causing the photosensitive member and the scanning line on the photosensitive member to withstand the scanning line. Drive mechanism for relatively moving in the direction (sub-scanning direction), a modulated light source capable of emitting light of the first wavelength toward the position of the scanning line on the photoconductor, the light source unit, the deflector, and the drive Controlling a mechanism to scan a laser beam on the photoconductor and controlling the modulation light source to intermittently irradiate the modulation light source to a position of a scanning line on the photoconductor in accordance with predetermined drawing data With a part And wherein the door.

With such a configuration, the laser beam is scanned so as to move the spot position in a state where a spot is always formed on the photosensitive member without being modulated. Then, at the moment when the spot of the laser beam reaches the position where an image is to be formed on the photosensitive member, the entire scanning line is irradiated by the modulated light source. At this time,
Since the spot position is simultaneously irradiated by the laser beam of the second wavelength and the light of the first wavelength,
A first charge transport layer (CTL) and a second charge transport layer (CT)
L) are both conductors. Therefore, at the spot position, the charge uniformly applied to the surface of the photoreceptor is lost,
An electrostatic latent image is formed.

The first charge transport layer (CTL) is formed on the charge generation layer (CGL), and the second charge transport layer (CT)
L) may be formed on the first charge transport layer (CTL). Also, the first charge transport layer (CTL)
A third charge transporting layer (CTL) having sensitivity to the above wavelength may be further formed.

In this scanning optical apparatus, the photosensitive member includes a plurality of photosensitive drums corresponding to each color component for forming a color image, and the driving mechanism controls the photosensitive drums respectively. A drum driving mechanism for rotating at a high speed, and further, a light splitting element for splitting a laser beam deflected and scanned by the deflector in accordance with each photosensitive drum, and a laser beam emitted from the light splitting element. For example, a light guide unit formed of, for example, a group of mirrors for guiding each of the photosensitive drums may be provided. Each color component may be four colors of yellow, magenta, cyan, and black.
Three colors of yellow, magenta, and cyan may be used, or another combination may be used.

Further, the deflecting unit may include a polygon mirror, and the scanning optical system may include an fθ lens unit disposed between the deflector and the light splitting element.
In the fθ lens unit, only the front group lens is disposed between the deflector and the light splitting element, and the plurality of rear group lenses are respectively positioned between the light splitting element and each of the photosensitive drums. It may be arranged.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A scanning optical device according to an embodiment of the present invention will be described below with reference to the drawings. FIG.
FIG. 2 is a plan view of a main part showing the scanning optical device of the present embodiment. FIG. 2 is a sectional view taken along the line II-II in FIG.

This scanning optical device comprises a light source unit for emitting a laser beam, a deflecting unit for deflecting and scanning these laser beams, an fθ lens unit 3 for converging a laser beam deflected and scanned from the deflecting unit 2, and a scanning light. Is provided with a prism P and a mirror group 4 that divide the light into four directions.

The scanning optical apparatus includes a housing (not shown) and an optical table 6 fixed to the housing and arranged horizontally. Above the optical bench 6, a light source unit 1, a deflecting unit 2, an fθ lens unit 3, a prism P, and a mirror group 4 are arranged. The photoconductor unit 5 is disposed in a housing below the optical bench 6.

The light source unit 1 has a light source unit 11 for emitting a laser beam L and a cylindrical lens 12. The light source unit 11 includes a laser diode that emits a laser beam having a wavelength of 780 nm as divergent light, and a collimator lens (both not shown) that converts the divergent light into parallel light. The cylindrical lens 12 is disposed so that its curved generating line is horizontal to the optical bench 6, and converts the laser beam L incident as parallel light into the optical bench 6.
Is converged only in the direction perpendicular to the direction (the direction corresponding to the sub-scanning direction).

The deflecting unit 2 has a polygon mirror 21 and a polygon motor (not shown). Polygon mirror 21
Has a flat, substantially regular hexagonal column shape, and each side surface is formed as a reflection surface. This polygon mirror 2
Numeral 1 has its central axis oriented perpendicular to the optical bench 6 and is rotatably supported about the central axis. The polygon mirror 21 is driven by a polygon motor and rotates counterclockwise in FIG.

The laser beam L emitted from the cylindrical lens 12 of the light source unit 1 is converged only in the direction perpendicular to the optical bench 6, and is converged on the optical bench 6 near each reflection surface of the polygon mirror 21. An image is formed into a horizontal line segment. In a state where the polygon mirror 21 is rotating, the laser beam L reflected by each reflection surface is directed in the direction of the arrow y (main scanning direction) in FIG.
Is deflected and scanned.

Lens section 3 is composed of a first lens 31 and a second lens 32 arranged in order on the optical path of the laser beam L reflected by the polygon mirror 21, and a laser beam divided into four by a prism P as described later. Beam L1
Third lenses 331 to 334 provided corresponding to L4
By The first lens 31 is a lens for correcting aberration of the fθ lens unit 3. Also, the second
The lens 32 has convergence power mainly in the main scanning direction (the y direction in FIG. 1).

The third lenses 331 to 334 are fixed in elongated holding members F1 to F4, respectively. Each of these holding members F1 to F4 has a longitudinal direction indicated by y in FIG.
1 and 2, and arranged in the direction opposite to the arrow in the x direction in FIGS. Note that each of the holding members F1 to F4 is open at the upper and lower portions. Slits S1 to S4 are formed at positions corresponding to the lower openings of the holding members F1 to F4 on the optical bench 6, respectively. In addition, each of these third lenses 331 to 334
Is mainly in the x direction (sub-scanning direction) in FIGS. 1 and 2.
Has the power of convergence.

The prism P as a light splitting element is formed in a long shape, and has a substantially L-shaped cross section perpendicular to the longitudinal direction. FIG. 3 is an enlarged view showing only the prism P in FIG. As shown in this figure,
The prism P includes a long first portion PA having a triangular prism shape and a long second portion PB having a trapezoidal cross section.

The first portion PA has a cross section perpendicular to the longitudinal direction formed into a right-angled isosceles triangle with a base angle of 45 °. The second portion PB is formed in an isosceles trapezoidal shape whose cross section perpendicular to the longitudinal direction has a base angle of 45 °. The length of the short side of the triangle of the cross section of the first portion PA and the length of the second portion P
The lengths of the oblique sides of the trapezoid of the cross section of B are the same.
Then, the first portion PA and the second portion PB are bonded so as to join both sides having the same length in the triangle and the trapezoid of the cross section thereof.

In the prism P, this bonded surface is referred to as a first surface P1, a surface having the same shape as the first surface P1 in the first portion P1 is referred to as a second surface P2, and a second surface P2 in the second portion P2. A surface having the same shape as the first surface P1 is referred to as a third surface P3. These first plane P1, second plane P2, and third plane P
3, a semipermeable membrane is formed.

The prism P is arranged so that its longitudinal direction is directed horizontally to the optical table 6 and perpendicular to the optical axes of the first lens 31 and the second lens 32 of the fθ lens 3. Have been. The surface corresponding to the bottom side of the triangle of the cross section of the first portion PA is the bottom surface Ph, and horizontally faces the optical bench 6. Also, the second part P
The surface corresponding to the base of the trapezoid of the cross section of B is a vertical surface Pp
And faces the rear surface of the second lens 32 of the fθ lens 3. Further, the center of the first surface P1 of the prism P is defined by the first lens 31 and the second lens 3 of the fθ lens 3.
The two optical axes are arranged so as to coincide with each other.

The laser beam L emitted from the second lens 32 of the fθ lens 3 enters the prism P into its vertical plane Pp
And is divided into transmitted light and reflected light by the first surface P1. The transmitted light transmitted through the first surface P1 is
2, the light is further divided into transmitted light and reflected light by the second surface P2. The transmitted light transmitted through the second surface P2 is
The laser beam L1 is emitted outside the prism P. Further, the reflected light reflected by the second surface P2 is:
The laser beam is emitted from the bottom surface Ph to the outside of the prism P as a laser beam L2. On the other hand, the reflected light reflected by the first surface P1 goes to the third surface P3, and is further divided into transmitted light and reflected light by the third surface P3. The transmitted light transmitted through the third surface P3 is emitted outside the prism P as a laser beam L3. The light reflected by the third surface P3 is emitted from the vertical surface Pp to the outside of the prism P as a laser beam L4.

As shown in FIG. 2, the mirror group 4 is classified into first to fourth systems provided on the optical path of each of the laser beams L1 to L4 emitted from the prism P. The first system in the mirror group 4 includes a mirror 411
And the mirror 413, and the second system is the mirror 42
1 to a mirror 423. The third system includes mirrors 431 to 433, and the fourth system includes:
It comprises a mirror 441.

Then, of the laser beams L1 to L4 emitted from the prism P, the laser beam L1 is guided to the third lens 331 by the mirrors 411 to 413. The laser beam L2 is transmitted to each of the mirrors 421 to 42
3 guides the light to the third lens 332. Then, the laser beam L3 is guided to the third lens 333 by each of the mirrors 431 to 433. The laser beam L4 is guided by the mirror 441 to the third lens 334.

Each of the laser beams L1 to L4 guided by the mirror group 4 is applied to each of the holding members F1 to F4.
Each of the third lenses 331 to 33 is incident from the upper opening of F4.
4 and is emitted from the slits S1 to S4 of the optical bench 6 below the optical bench 6 through the lower openings of the holding members F1 to F4.

The photosensitive member section 5 has four photosensitive drums 51 to 54 each having a photosensitive layer formed on a cylindrical surface.
These photosensitive drums 51 to 54 are arranged below the slits S1 to S4 of the optical bench 6, respectively. That is,
Each of the photoconductor drums 51 to 54 is rotatably supported at the central axis with its central axis directed parallel to the longitudinal direction of each of the slits S1 to S4.

The photosensitive unit 5 has a drum driving mechanism connected to each of the photosensitive drums 51 to 54. This drum drive mechanism can individually drive each of the photoconductor drums 51 to 54 and rotate them around their central axes. Each of the photoconductor drums 51 to 54 has
Black, yellow, cyan, and magenta toners are supplied.

The laser beam L reflected by the polygon mirror 21 is scanned in the y direction in FIG. 1 and passes through the first lens 31 and the second lens 32 of the fθ lens unit 3.
The laser beam L transmitted through the second lens 32 enters the prism P and is divided into four laser beams L1 to L4. Each of these laser beams L1 to L4 is guided by a mirror group 4 and each of the third lenses 3 of the fθ lens unit 3.
Light is incident on 31 to 334. Then, the laser beams L1 to L4 emitted from the third lenses 331 to 334, respectively.
Form spots on the photoconductor drums 51 to 54 and form scanning lines parallel to the central axes of the photoconductor drums 51 to 54, respectively. In addition, this photoconductor 5
Will be further described later.

The scanning optical device has a detecting section 7 for detecting a drawing start position. The detection unit 7 includes a separation mirror 71, a condenser lens 72, and a light receiving sensor 73.

The separation mirror 71 is disposed on the optical path of the laser beam L1 between the prism P and the mirror 411 at a scanning start position outside the area corresponding to the effective scanning range on the photosensitive drum 51. When the polygon mirror 21 rotates counterclockwise in FIG. 1, the laser beam L reflected by the polygon mirror 21 is deflected and scanned in the direction of the arrow in the y direction in FIG. That is, the laser beam L1 further transmitted through the first lens 31, the second lens 32 and the prism P
Is also scanned in the direction of the arrow in the y direction in FIG. Therefore, each time the reflecting surfaces of the polygon mirror 21 are switched, the laser beam L1 at the scanning start position emitted from the prism P is reflected by the separation mirror 71.

The condenser lens 72 is a cylindrical lens, and is disposed on the optical path of the laser beam reflected by the separation mirror 71 with its curved generatrix directed parallel to the optical bench 6. First lens 3 of fθ lens unit 3
The laser beam transmitted through the first and second lenses 32 is converged only in a direction (main scanning direction) that is orthogonal to the beam axis and horizontal to the optical bench 6, but is converged in a direction perpendicular to the optical bench 6 (sub scanning direction). The light enters the condenser lens 72 while diverging. The condenser lens 72 converges the incident laser beam in the sub-scanning direction. The light receiving sensor 73 is arranged near the image forming position of the convergent light emitted from the condenser lens 72, detects this convergent light, and determines the timing of the write (drawing) start position in the main scanning direction. A signal is output.

Next, the photoconductor section 5 will be further described. As shown in FIG. 2, the photoconductor unit 5 includes modulated light sources E1 to E5 provided for the respective photoconductor drums 51 to 54.
E4. Each of the modulation light sources E1 to E4 has a wavelength of 500
A plurality of light emitting diodes that emit light of nm are linearly arranged. The modulated light sources E1 to E4
Are arranged opposite to the scanning lines formed by the laser beams L1 to L4 on the respective photosensitive drums 51 to 54, and can irradiate the entire position of each scanning line and the vicinity thereof.

FIG. 4 is an explanatory view schematically showing the structure of the photosensitive member section 5. As shown in FIG. Note that FIG. 4 shows only the configuration of the photoconductor drum 51 and the vicinity thereof, but the same applies to the configuration of each of the photoconductor drums 52 to 54 and the vicinity thereof.

A long main charger 511 is disposed above the photosensitive drum 51 in FIG. The main charger 511 is arranged to face the photoconductor drum 51 with its longitudinal direction parallel to the central axis of the photoconductor drum 51. The main charger 511 can negatively charge the surface of the photosensitive drum 51.

A developing unit 512 is disposed on the right side of the photosensitive drum 51 in FIG. This developing device 5
Reference numeral 12 includes a long toner supply port for incorporating negatively charged toner and discharging the toner to the outside. The developing device 512 is arranged such that the longitudinal direction of the toner supply port is parallel to the central axis of the photosensitive drum 51 and the toner supply port is opposed to the photosensitive drum 51.

Further, a long transfer charger 513 is arranged below the photosensitive drum 51 in FIG. The transfer charger 513 is arranged to face the photosensitive drum 51 with its longitudinal direction parallel to the central axis of the photosensitive drum 51. Then, the transfer charger 5
The sheet 13 can positively charge the sheet M conveyed between the transfer charger 513 and the photosensitive drum 51.

On the left side of the photosensitive drum 52 in FIG. 4, a static elimination lamp 514 and a cleaner 515 are arranged in order from bottom to top in FIG. Static elimination lamp 514
Is a long lamp, and can emit light in both wavelength bands of at least 500 nm and 780 nm. The neutralization lamp 514 is opposed to the photosensitive drum 51 with its longitudinal direction parallel to the central axis of the photosensitive drum 51. The cleaner 515 is formed by a long brush or blade or the like. The cleaner 515 is disposed so that its longitudinal direction is parallel to the central axis of the photosensitive drum 51 and is in contact with the surface of the photosensitive drum 51.

FIG. 5 is an explanatory view schematically showing the structure of the photosensitive drum 51. Although FIG. 5 shows only the photosensitive drum 51, each of the photosensitive drums 52 to 5
4 is similarly configured. As shown in FIG. 5, the photosensitive drum 51 is formed on a cylindrical aluminum base 5a, a charge generation layer (hereinafter referred to as CGL) 5b formed on the base 5a, and formed on the CGL 5b. It has a first charge transport layer (hereinafter, referred to as first CTL) 5c and a second charge transport layer (hereinafter, referred to as second CTL) 5d formed on the first CTL 5c.

The CGL 5b is a carrier generation layer which generates carriers and is positively charged. The first CTL 5c is a charge transport having sensitivity to light having a wavelength of 500 nm. That is,
The first CTL 5c functions as a conductor only when irradiated with light having a wavelength of 500 nm. The second CTL 5d is
The charge transport is sensitive to light having a wavelength of 780 nm. That is, the second CTL 5d functions as a conductor only when irradiated with light having a wavelength of 780 nm. In addition, CGL5
b, the first CTL 5c, and the second CTL 5d correspond to a charge generation layer, a first charge transport layer, and a second charge transport layer, respectively.

Next, a control system of the scanning optical device will be described. FIG. 6 is a block diagram schematically showing a control system of the scanning optical device. As shown in FIG. 6, the scanning optical device has a control unit 8 that controls each unit of the device. The control unit 8 controls each of the modulated light sources E1 to E as described below.
4, the light source unit 11, the deflecting unit 2, the detecting unit 7, and the drum driving mechanism D, respectively.

That is, the control section 8 is connected to each of the modulation light sources E1 to E4 via an LED drive circuit (not shown), and obtains drawing data from a higher-level device (not shown), and also obtains each drawing data in accordance with the drawing data. Set the modulation light sources E1 to E4 to O
N / OFF control is performed. Note that each of the modulation light sources E1 to E4
It corresponds to each color component in color image formation,
It is individually controlled by the control unit 8.

The control unit 8 is connected to a laser diode in the light source unit 11 of the light source unit 1 via an LD drive circuit (not shown). Then, the control unit 8 can turn on the laser diode of the light source unit 11 in a steady state.

Further, the controller 8 is connected to a polygon motor (not shown) in the deflecting unit 2, and rotates the polygon mirror 21 at a constant speed in the counterclockwise direction in FIG. 1 by the polygon motor. Further, the control unit 8 causes each of the photosensitive drums 51 to rotate at a constant speed by the drum driving mechanism D in the photosensitive unit 5. The control unit 8 is connected to the light receiving sensor 73 in the detecting unit 7.
By receiving the output signal from the third mirror 3, it is possible to recognize the starting position of the scanning performed for each reflection surface of the polygon mirror 21.

The laser diode in the light source unit 11 of the light source unit 1 is always on. Therefore, the laser beams L1 to L4 always form an image on the surfaces of the photoconductor drums 51 to 54 to form spots.
These spots move in a direction parallel to the central axis of each of the photosensitive drums 51 to 54 according to the rotation of the polygon mirror 21, and form scanning lines on the photosensitive drums 51 to 54. At this time, each of the photosensitive drums 51 is driven by a drive mechanism (not shown) and is rotating at a constant speed. Therefore, the entire surface of each of the photosensitive drums 51 to 54 is scanned by the corresponding laser beam L1 to L4, respectively.

The control unit 8 uses a signal from the light receiving sensor 73 of the detection unit 7 as a synchronization signal,
The spot positions of the laser beams L1 to L4 in drawing each line on each of the photosensitive drums 51 to 54 are always recognized. Then, the control unit 8 individually controls ON / OFF of each of the modulated light sources E1 to E4 according to the drawing data. That is, taking the photosensitive drum 51 as an example, the control unit 8 changes the modulation light source E1 every time the spot of the laser beam L1 moving at a constant speed on the photosensitive drum 51 reaches a position where an image is to be formed. Turn ON. However, when the spot of the laser beam L1 is located at a position other than the position where an image is to be formed, the control unit 8 turns off the modulated light source E1.

Therefore, the photosensitive drum 51 is irradiated with the laser beam L1 over the entire surface thereof. However, the photosensitive drum 51 is irradiated by the modulated light source E1 only at a point on the surface where an image is to be formed.

That is, as shown in FIGS. 4 and 5, the surface of the photosensitive drum 51 is irradiated with the laser beam L1 in a state where it is uniformly negatively charged in advance by the main charger 511. This laser beam L having a wavelength of 780 nm
When the light is irradiated by the light spot 1, the second CTL 5 d of the photosensitive drum 51 at the spot position becomes a conductor only at that moment. However, at this moment, the modulated light source E1
If F, the first CTL 5c does not function as a conductor, so that the negative charge on the surface of the photosensitive drum 51 is not lost.

However, when the modulation light source E1 is turned on,
At that moment, at the spot position by the laser beam L1 on the surface of the photosensitive drum 51, irradiation with both the light of the wavelength of 780 nm and the light of the wavelength of 500 nm is performed simultaneously. Then, at that moment, at the spot position, both the first CTL 5c and the second CTL 5d become conductors. Therefore, at the spot position on the surface of the photosensitive drum 51, the previously given negative charge is lost. As a result, an electrostatic latent image is formed on the surface of the photoconductor drum 51, which is composed of the portion where the negative charges have been lost and the portion where the negative charges have remained.

Since the photosensitive drum 51 is rotating at a constant speed, the portion of the surface of the photosensitive drum 51 irradiated with the laser beam L1 reaches the position of the developing device 512. The developing unit 512 supplies the toner uniformly to the surface of the photosensitive drum 51. Since this toner is negatively charged, it adheres only to the portion of the surface of the photosensitive drum 51 where the negative charge has been lost. That is, the photosensitive drum 51
The electrostatic latent image formed on the surface is developed by the developing device 512.

Further, the portion on the surface of the photosensitive drum 51 passes through the position of the developing device 512 and reaches the position of the transfer charger 513. Note that a sheet M transported by a transport mechanism (not shown) is interposed between the transfer charger 513 and the photosensitive drum 51. Then, the transfer charger 513
Causes the sheet M conveyed to the left in FIG. 4 to be positively charged. On the other hand, since the toner on the surface of the photosensitive drum 51 is previously negatively charged, it adheres to the surface of the positively charged paper M. That is, the image formed by the toner formed on the surface of the photosensitive drum 51 is transferred onto the sheet M by the transfer charger 513.

Then, the portion of the surface of the photosensitive drum 51 where the transfer has been completed reaches the charge removing lamp 514. The neutralization lamp 514 has a wavelength of 7 with respect to the surface of the photosensitive drum 51.
Since the light of 80 nm and the light of wavelength 500 nm are irradiated, both the first CTL 5c and the second CTL 5d become conductors, and the surface of the photosensitive drum 51 is uniformly discharged. Further, the portion of the surface of the photosensitive drum 51 from which the charge has been uniformly removed reaches the cleaner 515. This cleaner 515
The toner slightly remaining after the transfer processing in the transfer charger 513 is physically removed.

As described above, the portion of the photosensitive drum 51 from which the surface is uniformly discharged and the toner is also removed reaches the main charger 511 again, and undergoes the above-described processing.

In this way, a latent image is formed on each of the photosensitive drums 51 to 54 for each corresponding color component. The toner corresponding to each color component is supplied to each of the photoconductor drums 51 to 54. In this state, the transport device (not shown) transports the paper to be printed. On the conveyed sheet, the image of the toner for each color component formed on the surface of each of the photosensitive drums 51 to 54 is sequentially transferred on one scanning line on the printing sheet. Further, the paper on which the image for each color component is multiplex-transferred is subjected to a heat fixing process in a fixing unit (not shown), thereby completing the color printing. The color-printed sheet is discharged to a discharge unit (not shown).

As described above, in the scanning optical device according to the present embodiment, the laser beam L emitted from a single laser diode in the light source
The laser beams are divided and used as laser beams L1 to L4.
Therefore, the wavelengths of the laser beams L1 to L4 always match. Therefore, the laser beams L1 to L4 can form scanning lines of the same shape on the surfaces of the photosensitive drums 51 to 54 without being affected by the chromatic aberration of magnification in the fθ lens unit 3, respectively. in this way,
If the scanning line shapes on the surfaces of the photosensitive drums 51 to 54 match, a color image without color shift is formed.

<Modification> This modification is characterized in that the photoconductor section 5 has a photoconductor drum shown in FIG. 7 in the configuration of the scanning optical device. Although only the photosensitive drum 51 'is shown in FIG. 7, the photosensitive section 5 includes an individual photosensitive drum for each color component for forming a color image, as in the above embodiment. I have.

As shown in FIG. 7, the photosensitive drum 51 'of the present modified example has a third CT as a third charge transport layer.
It is characterized in that it further has L5e. This third
The CTL 5e is formed on the second CTL 5d of the photosensitive drum 51 of the embodiment shown in FIG. In addition,
The third CTL 5e is a charge transport having a sensitivity at 500 nm as in the first CTL. Therefore, the photosensitive drum 51 ′ loses a predetermined negative charge only when it is simultaneously irradiated with the laser beam L1 having the wavelength of 780 nm and the light having the wavelength of 500 nm emitted from the modulation light source, as in the above-described embodiment. Will be Other configurations, operations, and effects are the same as those of the above embodiment.

[0063]

According to the scanning optical device of the present invention configured as described above, the modulation light source is turned on in accordance with the drawing pattern.
By turning on / off, an image can be formed without modulating the laser beam from the light source unit.

Therefore, when the present invention is applied to a scanning optical device for forming a latent image on a photosensitive member corresponding to each color component for forming a color image, it is not necessary to modulate a laser beam. A single laser beam emitted from the light source unit can be divided and used. For this reason,
It is easy to match the shapes of the scanning lines on each photoconductor with each other, and it is possible to form a color image without color shift.

[Brief description of the drawings]

FIG. 1 is a plan view showing a scanning optical device according to an embodiment of the present invention.

FIG. 2 is a sectional view taken along the line II-II in FIG.

FIG. 3 is an enlarged view showing a prism.

FIG. 4 is an explanatory view schematically showing a configuration of a photoconductor unit according to an embodiment of the present invention.

FIG. 5 is an explanatory diagram schematically showing a configuration of a photosensitive drum according to an embodiment of the present invention.

FIG. 6 is a block diagram schematically showing a control system according to an embodiment of the present invention.

FIG. 7 is an explanatory view schematically showing a configuration of a photosensitive drum according to a modified example.

[Explanation of symbols]

Reference Signs List 1 light source unit 11 light source unit 2 deflecting unit 21 polygon mirror 3 fθ lens unit 31 first lens 32 second lens 331-334 third lens 4 mirror group 411-413, 421-423, 431-433, 4
41 mirror 5 photoreceptor part 51 to 54 photoreceptor drum E1 to E4 modulation light source 5a base 5b CGL (charge generation layer) 5c first CTL (first charge transport layer) 5d second CTL (second charge transport layer) 5e third CTL ( Third charge transport layer) 8 Control unit

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) G03G 15/04 111 H04N 1/29 G 5C074 H04N 1/04 C 1/113 B41J 3/00 D 1/29 H04N 1 / 04 D 104A F-term (reference) 2C362 AA46 BA51 BA83 BA84 BB14 CA22 CA39 CB59 2H030 AA01 AB02 BB02 BB71 2H045 AA01 BA02 BA26 BA34 CA63 2H076 AB05 AB06 AB08 AB12 AB42 5C072 AA03 BA17 CA06 CA07 HA07 Q13A03 XB13 CC26 DD24 FF15 GG03 GG04 GG09 GG12

Claims (8)

[Claims] 1. A scanning optical system comprising: a charge generating layer for generating charges; a photosensitive member having a charge transport layer formed on the charge generating layer; and a charger for uniformly charging the surface of the photosensitive member. An apparatus, wherein the charge transport layer of the photoreceptor is at least constituted by a first charge transport layer having sensitivity to a first wavelength and a second charge transport layer having sensitivity to a second wavelength. A light source unit that emits light, a deflector that deflects and scans a laser beam emitted from the light source unit, and a scanning optic that converges the laser beam that is deflected and scanned by the deflector to form a scanning line on the photoconductor. A drive mechanism for relatively moving the photoconductor and a scanning line on the photoconductor in a predetermined direction intersecting the scanning line; and directing light of a first wavelength to a position of the scanning line on the photoconductor. Modulated light source capable of emitting light, said light source unit, deflection And controlling a modulator and a driving mechanism to scan a laser beam on the photoconductor, and controlling the modulation light source to intermittently apply the modulation light source to a position of a scanning line on the photoconductor in accordance with predetermined drawing data. A scanning unit, further comprising: a control unit for irradiating the laser beam. 2. The photoconductor according to claim 1, wherein the first charge transport layer is formed on the charge generation layer, and the second charge transport layer of the photoconductor is
2. The scanning optical device according to claim 1, wherein the scanning optical device is formed on the first charge transport layer. 3. The scanning device according to claim 2, wherein said photoconductor is sensitive to a first wavelength and further has a third charge transport layer formed on said second charge transport layer. Optical device. 4. A photosensitive drum comprising: a plurality of photosensitive drums corresponding to each color component for forming a color image; and a drive mechanism for rotating each of the photosensitive drums at a constant speed. A light splitting element for splitting the laser beam deflected by the deflector in accordance with each photosensitive drum, and a guide for guiding each laser beam emitted from the light splitting element to each photosensitive drum. The scanning optical device according to claim 1, further comprising an optical unit. 5. The scanning optical system according to claim 1, wherein the deflecting unit includes a polygon mirror, and the scanning optical system includes an fθ lens unit disposed between the deflector and the light splitting element. 5. The scanning optical device according to 4. 6. The deflecting unit has a polygon mirror, the scanning optical system includes a front lens group disposed between the deflector and the light splitting element, and the light splitting element and each of the light splitting elements. 5. The scanning optical device according to claim 4, further comprising: an f [theta] lens unit including a plurality of rear group lenses disposed respectively with the photosensitive drum. 7. The scanning optical device according to claim 4, wherein said light guide means is a mirror group comprising a plurality of mirrors. 8. The scanning device according to claim 4, wherein each of the photosensitive drums is provided for each of yellow, magenta, cyan, and black color components for forming a color image. Optical device.