JP3222346B2 - Optical writing device for light emitting element array printer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical writing device for a light emitting element array printer.

[0002]

2. Description of the Related Art Conventionally, techniques in such a field include:
For example, White Series NO. 6 "Optical Printer Design" Trikeps WS 6P. 114-129
Was disclosed. Conventionally, an optical printer uses a laser, an LED element, a liquid crystal element, and the like as a light source. A photosensitive drum uniformly charged by a charger is irradiated and exposed by the light source to form an electrostatic latent image. Is formed. The electrostatic latent image is thereafter developed by a developing device to form a toner image, and the toner image is transferred to a sheet by a transfer device and fixed by a fixing device. Among the light emitting element array printers, LED printers use LED elements as light sources.

FIG. 2 is a schematic view of such a conventional LED printer. In this figure, 11 is a photosensitive drum, 12
Is a charger for charging the photosensitive drum 11, 13 is an LED array head for exposing the photosensitive drum 11 to form an electrostatic latent image, and 14 is a toner for developing the electrostatic latent image on the photosensitive drum 11 to form a toner. A developing unit 15 for forming an image; a transfer unit 15 for transferring the toner image onto paper 16; a fixing unit 17 for fixing the transferred toner image; a cleaning unit 18 for removing toner remaining on the photosensitive drum 11; Reference numeral 19 denotes a charge removing lamp for removing charges remaining on the photosensitive drum 11, reference numeral 20 denotes a paper cassette, and reference numeral 21 denotes a paper stacker.

When the LED elements of the LED array head 13 selectively emit light, an electrostatic latent image is formed on the photosensitive drum 11 uniformly charged by the charger 12.
In the developing device 14, the toner adheres to the photosensitive drum 11 according to the electrostatic latent image. On the other hand, the paper 16 fed from the paper cassette 20 is transferred to the photosensitive drum 11 and the transfer device 15.
Pass through. At this time, the toner adhered on the photosensitive drum 11 is transferred to the sheet 16 by the transfer unit 15 and then fixed by the fixing unit 17 to be
Is stored in.

In the photosensitive drum 11, a cleaning device 18 removes toner remaining on the photosensitive drum 11, and a discharge lamp 19 removes an electrostatic latent image formed in the previous electrophotographic process. It is removed to prepare for each process after the next charging process. A DC or AC motor is used as a driving unit for rotating the photosensitive drum 11 at a constant speed and a driving unit for feeding paper.

FIG. 3 is an enlarged perspective view of an optical imaging system of a conventional light emitting element array printer, and FIG. 4 is a conceptual diagram of an optical imaging system of a conventional light emitting element array printer. In FIG. 3, reference numeral 13 denotes an LED array head in which a plurality of, for example, 128 LED array chips 31 are arranged, and reference numeral 32 denotes a rod lens array in which a plurality of gradient index lenses are arranged. The rod lens array 32 forms an image of the light L of the LED array chip 31 on the photosensitive drum 11, which is the surface to be illuminated, at an erect equal magnification.

In this case, the resolution of the LED array head 13 and the resolution of the electrostatic latent image on the photosensitive drum 11, that is, the resolution of the print screen become the same. The resolution of the LED array head 13 is generally 300 DPI (dot per inch), 400 DPI, 600 DPI, etc.
When the resolution is large, for example, an image including a curve can be faithfully printed on the original image.

In the drive section, print data and drive signals are output from the print data output section 36 to the LED drive section 37. The LED drive section 37 converts the print data and drive signals into LED drive signals and It is sent to the array head 13. FIG. 5 is a plan view of a conventional LED array head. In this figure, reference numeral 39 denotes a substrate, and the substrate 39 has a wiring pattern (not shown) formed by thick film or thin film printing or the like. Reference numeral 31 denotes an LED array chip provided with a plurality of LED elements (not shown) in a row, and a plurality of LED array chips 31 are provided on a substrate 39. As a result, the LED elements are linearly arranged along the longitudinal direction of the substrate 39 at an equal pitch.

Reference numeral 40 denotes a driving circuit chip (hereinafter referred to as a driver IC) for driving the LED elements. The driver ICs 40 are provided for each LED array chip 31 one by one. Reference numeral 41 denotes a bonding wire that electrically connects the LED array chip 31 and the driver IC 40. FIG. 6 is a diagram showing a light emitting unit of the LED array head.

In FIG. 1, reference numeral 31 denotes an LED array chip, and reference numeral 44 denotes a light emitting area, which is arranged at a pitch of, for example, 42.3 μm. Reference numeral 45 denotes an individual electrode connected to the light emitting area 44. The individual electrode 45 is connected to the driver IC 40 (see FIG. 5) by a bonding wire 41. By supplying a print data signal to the driver IC 40, the LED array head 13
(See FIG. 3), a desired light emission pattern can be obtained. The light emitting unit of the LED array head 13 is an LED.
It is formed by arranging a plurality of array chips 31 in a line.

FIG. 7 is a perspective view showing a boundary portion of the LED array chip. In this figure, 31 is an LED array chip, 44 is a light emitting area, 45 is an individual electrode, and 48 is a connection space. At the boundary of each LED array chip 31, the end of the light emitting area 44 and the LED array chip 31
Is 8 μm, and the distance between the LED array chips 31, that is, the connection space 48 is 6.3 μm.

[0012]

However, in the above-described conventional light-emitting element array printer, the accuracy of the distance between the light-emitting areas 44 and between the end of the light-emitting area 44 and the end of the LED array chip 31, and the accuracy of the LED. It is difficult to increase the accuracy of the outer dimensions of the array chip 31,
The LED array chips 31 cannot be accurately arranged in a line. Moreover, since there are many connection points between the LED array chip 31 and the driver IC 40, the yield is reduced and the cost is increased.

To increase the resolution of a printed image,
The resolution of the LED array head 13 must be increased. For example, in order to manufacture the LED array head 13 of 600 DPI or more, the light emitting area 44 and the LED array chip 31 must be reduced in size, and the mounting technology such as wire bonding using the bonding wires 41 must be increased in density, which increases the cost. Would.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an optical writing apparatus for a light emitting element array printer capable of printing at a high resolution by using a light emitting element array head having a low resolution. I do.

[0015]

To achieve the above object, the present invention provides: (1) a light emitting element array head comprising a plurality of light emitting elements, and a light emitting element array head disposed opposite to the light emitting element array head; A photosensitive medium that receives the light emitted by the light emitting element to form an electrostatic latent image and that is disposed between the light emitting element array head and the photosensitive medium and that converges the light emitted by the light emitting element and forms the light on the photosensitive medium; In an optical writing device of a light emitting element array printer having a converging rod lens for forming an image, two colors having an absorption wavelength at a wavelength of writing light between the converging rod lens and the photosensitive medium in order from the converging rod lens side. A ferroelectric liquid crystal cell in which a dichroic dye is added, and the absorption axis of the dichroic dye molecule is uniformly aligned in the main scanning direction and the sub-scanning direction according to the polarity of the applied electric field. Light incident surface at an angle And a birefringent plate having a predetermined thickness, a predetermined thickness, and capable of displacing polarized light having a component in the direction of the optical axis by a desired distance.

(2) In the optical writing device for a light emitting element array printer according to the above (1), the displacement direction of the image forming position displacement means is the main scanning direction of the light emitting element array printer, and the displacement distance is the light emitting element array. The distance between the light-emitting elements is の. (3) a light-emitting element array head including a plurality of light-emitting elements, a photosensitive medium disposed to face the light-emitting element array head, and receiving light emitted by the light-emitting elements to form an electrostatic latent image; An optical writing device for a light emitting element array printer, comprising: a light condensing rod lens disposed between a light emitting element array head and the photosensitive medium and converging light emitted by the light emitting element to form an image on the photosensitive medium. Between the rod lens and the photosensitive medium, in order from the converging rod lens side, set a light incident surface at a predetermined angle with respect to the optical axis,
A birefringent plate having a predetermined thickness and capable of displacing polarized light in the direction of the optical axis by a desired distance; and a dichroic dye having an absorption wavelength at the wavelength of the writing light is added. An image forming position displacing means having a ferroelectric liquid crystal cell in which the absorption axis of the dye molecule is uniformly aligned in the main scanning direction and the sub-scanning direction according to the polarity of the applied electric field is provided.

(4) In the optical writing device for a light emitting element array printer according to the above (3), the displacement distance in the image forming position displacement means is 1/2 of the distance between the light emitting elements of the light emitting element array. The direction is the main scanning direction of the light emitting element array printer. (5) a light-emitting element array head including a plurality of light-emitting elements, a photosensitive medium disposed to face the light-emitting element array head, and receiving light emitted by the light-emitting elements to form an electrostatic latent image; An optical writing device for a light emitting element array printer, comprising a converging rod lens disposed between a light emitting element array head and the photosensitive medium and focusing light emitted by the light emitting element to form an image on the photosensitive medium. A dichroic dye having an absorption wavelength at the wavelength of the writing light is added between the array head and the converging rod lens in order from the light emitting element array head side, and the absorption axis of the dichroic dye molecule is applied to the electric field. A ferroelectric liquid crystal cell that is uniformly aligned in the main scanning direction and the sub-scanning direction according to the polarity of the light incident surface is set at a predetermined angle with respect to the optical axis, and has a predetermined thickness, Polarization of the component of the optical axis direction And a birefringent plate capable of by a displacement distance is obtained by so disposing the imaging position displacement means.

(6) A light-emitting element array head comprising a plurality of light-emitting elements, and a photosensitive medium disposed opposite to the light-emitting element array head and receiving light emitted by the light-emitting elements to form an electrostatic latent image An optical writing device for a light emitting element array printer, comprising a converging rod lens that is disposed between the light emitting element array head and the photosensitive medium and focuses light emitted by the light emitting element and forms an image on the photosensitive medium. A light incident surface is set between the light emitting element array head and the converging rod lens at a predetermined angle with respect to an optical axis in order from the light emitting element array head side, and has a predetermined thickness. A birefringent plate capable of displacing the polarization of the axial component by a desired distance; and a birefringent plate having an absorption wavelength at the wavelength of the writing light.
A ferroelectric liquid crystal cell which adds a chromatic dye and uniformly aligns the absorption axis of the dichroic dye molecules in the main scanning direction and the sub-scanning direction according to the polarity of the applied electric field; Means are provided.

(7) A light-emitting element array head comprising a plurality of light-emitting elements, and a photosensitive medium disposed opposite to the light-emitting element array head and receiving the light emitted by the light-emitting elements to form an electrostatic latent image An optical writing device for a light emitting element array printer, comprising a converging rod lens that is disposed between the light emitting element array head and the photosensitive medium and focuses light emitted by the light emitting element and forms an image on the photosensitive medium. A dichroic dye having an absorption wavelength at the wavelength of the writing light is added between the light emitting element array head and the converging rod lens, and the absorption axis of the dichroic dye molecule is adjusted according to the polarity of the applied electric field. A ferroelectric liquid crystal cell oriented in the main scanning direction and the sub-scanning direction is installed as described above, and a light incident surface is set between the converging rod lens and the photosensitive medium at a predetermined angle with respect to an optical axis. And the specified thickness And, and the polarization of the optical axis direction component placing a birefringent plate which can be displaced by a desired distance,
An image forming position displacing means is provided.

(8) A light-emitting element array head comprising a plurality of light-emitting elements, and a photosensitive medium disposed opposite to the light-emitting element array head and receiving the light emitted by the light-emitting elements to form an electrostatic latent image An optical writing device for a light emitting element array printer, comprising a converging rod lens that is disposed between the light emitting element array head and the photosensitive medium and focuses light emitted by the light emitting element and forms an image on the photosensitive medium. A light incident surface is set at a predetermined angle with respect to the optical axis between the light emitting element array head and the converging rod lens, has a predetermined thickness, and converts the polarization of the optical axis direction component to a desired distance. A birefringent plate that can be displaced only by a distance, and a dichroic dye having an absorption wavelength at the wavelength of the writing light is added between the converging rod lens array and the photosensitive medium. Apply light absorption axis Uniformly placed ferroelectric liquid crystal cells aligned in the main scanning direction and the sub-scanning direction depending on the polarity of the field,
An image forming position displacing means is provided.

(9) In the optical writing device for a light emitting element array printer according to the above (5), (6), (7) or (8), the displacement distance of the image forming position displacement means is the light emitting element of the light emitting element array. The distance between them is 1/2, and the displacement direction is the main scanning direction of the light emitting element array printer.

[0022]

According to the present invention, by switching the polarity of an electric signal applied to the ferroelectric liquid crystal cell, light can be formed at a position facing the light emitting element array on the photosensitive medium, or a predetermined distance can be obtained. An image can be formed at the displaced position. Therefore, when the light emitting operation of the LED array head is performed in accordance with the odd number data of one line of print data, and when the even number data of the one line of print data is performed,
By switching the polarity of the electric signal applied to the ferroelectric liquid crystal cell of the imaging position displacement element when performing the light emitting operation of the LED array head, an LED array head having a resolution of N μm pitch in the main scanning direction is used. It is possible to irradiate the surface of the photosensitive drum with a resolution of N / 2 μm in the main scanning direction and print.

Therefore, printing can be performed at a high resolution using a light emitting element array printer having a low resolution.
Conversely, printing can be performed at a higher resolution by using a high-resolution light emitting element array printer.

[0024]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a diagram schematically showing a configuration of an optical writing device of a light emitting element array printer and a writing light path according to a first embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a light emitting element array, 2 denotes a converging rod lens array, 3 denotes an image forming position displacement element, and 4 denotes a photosensitive drum as a photosensitive medium. Is changing.

FIG. 8 is a diagram showing the configuration of the imaging position displacement element in FIG. In this figure, a laminated structure of a ferroelectric liquid crystal cell unit 50 and a birefringent plate 52 is formed in order from the converging rod lens array 2 side. The ferroelectric liquid crystal cell unit 50 has two glass substrates 8 and 9 each having transparent electrodes 6 and 7 formed on one surface and an alignment film (not shown) formed on the surface on which the alignment film and the transparent electrodes 6 and 7 are formed. Are arranged at a desired distance from each other, and are sealed between glass substrates 8 and 9 via an absorption layer 10 made of liquid crystal and dichroic dye. Further, a driving circuit 51 for applying an electric signal to the ferroelectric liquid crystal cell unit 50 is provided.

First, the structure and operation of the ferroelectric liquid crystal cell portion in the imaging position displacement element will be described. Regarding the structure of the liquid crystal cell, a ferroelectric liquid crystal having a chiral smectic C phase is used as the liquid crystal used for the absorption layer 10 composed of the liquid crystal and the dichroic dye. FIG. 9 is a schematic diagram for explaining the switching of the ferroelectric crystal of the optical writing device of the light emitting element array printer according to the first embodiment of the present invention, and FIG. 9A shows the stable state A (for example, electric field -E). 9 is applied, and FIG.
(B) shows a stable state B (for example, an electric field + E applied state).
Is shown.

As shown in this figure, the ferroelectric liquid crystal has a helical structure. When the ferroelectric liquid crystal is sandwiched between liquid crystal cells having a cell pitch smaller than the helical pitch, the helical structure is released, and as shown in FIG. A state is realized in which a region where the liquid crystal molecules 53 are tilted and stabilized by the tilt angle θ (here, θ = 45 °) with respect to the normal direction W of the smectic layer and a region where the liquid crystal molecules 53 are tilted and stabilized by θ in the opposite direction are mixed. it can.

[0028]

(Equation 1)

By applying an electric field in a direction perpendicular to the plane of the paper, the direction of the liquid crystal molecules 53 and their spontaneous polarization can be made uniform, and that state can be maintained.
By switching the polarity of the applied electric field, switching between the two states can be performed. That is, in FIG. 9, when an electric field −E is applied, the state A is inclined by −θ from the smectic layer normal direction W, and when an electric field + E is applied, when the electric field + E is applied, θ changes from the smectic layer normal direction W to θ.
90 ° from the orientation state of state A
It can be stabilized in the inclined state B.

FIG. 10 is a schematic diagram showing the operation of a ferroelectric liquid crystal cell in which a ferroelectric liquid crystal and a dichroic dye are sealed.
0 (a) shows the stable state A (state where the electric field −E is applied), and FIG. 10 (b) shows the stable state B (state where the electric field + E is applied). First, the installation direction of the ferroelectric liquid crystal cell will be described. The liquid crystal molecules are oriented in directions different from each other by 90 ° in two kinds of stable states. Therefore, the liquid crystal molecules 53 are arranged so that the major axis direction (director direction) of the liquid crystal molecules 53 in one of the stable states (here, the stable state A when an electric field of −E is applied) is coincident with the main scanning direction of the optical printer. .

In the ferroelectric liquid crystal cell, when a dichroic dye is mixed in the ferroelectric liquid crystal, the long axis of the dichroic dye molecules 54 is also oriented in the long axis direction of the liquid crystal molecules 53. (Here, it is assumed that the major axis of the dichroic dye molecule is the absorption axis.) Therefore, the transparent electrodes 6 and 7 of the ferroelectric liquid crystal cell unit 50 are provided.
By switching the polarity of the electric field applied to the liquid crystal molecules, switching between the two states of the liquid crystal molecule alignment is performed,
The orientation direction of the chromatic dye molecules 54 can be switched between two states in which the orientation directions are mutually 90 °.

That is, when an electric field of -E is applied between the transparent electrodes 6 and 7, the liquid crystal molecules 53 take an alignment state (stable state A) inclined by -θ from the normal direction W of the smectic layer. The dichroic dye molecules 54 are also oriented in the director direction of the liquid crystal molecules 53. On the other hand, when an electric field of + E is applied to the transparent electrodes 6 and 7, the liquid crystal molecules 53 assume an alignment state (stable state B) inclined by + θ from the normal direction W of the smectic layer. The dichroic dye molecules 54 are also oriented in the director direction of the liquid crystal molecules 53. In this case, since θ = 45 °, the alignment is performed at an angle of 2θ = 90 ° from the stable state A.

When the linearly polarized light incident on the ferroelectric liquid crystal cell unit 50 is a polarized light that oscillates in the direction of the absorption axis of the dichroic dye molecules 54, the light is absorbed by the dichroic dye and the ferroelectric liquid crystal cell unit 50 cannot be passed. On the other hand, the linearly polarized light incident on the ferroelectric liquid crystal cell unit 50 is
For polarized light that oscillates in a direction perpendicular to the absorption axis of
It is transmitted as it is without being absorbed by the coloring pigment.

FIG. 11 is an explanatory view showing the structure and operation of the birefringent plate in the imaging position displacement element. In this figure,
The birefringent plate 52 is set so that the y-axis (the direction in which the optical axis a is projected on the incident side surface) of the birefringent plate 52 is aligned with the main scanning direction. The birefringent plate 52 is made of a uniaxial crystal having optical anisotropy, for example, calcite.
Is cut obliquely so that the normal direction x and the optical axis a are at an angle φ (where φ> 0 °). Here, the direction in which the optical axis a is projected on the incident side surface of the birefringent plate 52 is the y axis, x
The normal direction of a plane including the axis and the y axis is defined as the z axis.

Next, transmission of light L incident on the birefringent plate 52 in the normal direction x will be described. In the case where the light L is linearly polarized light vibrating in the y-axis direction, that is, light L1, this light L1 is an extraordinary light component traveling in the optical axis direction of the birefringent plate. The output is displaced by a distance S in a plane (principal section) including the normal direction x of the refraction plate 52 and the optical axis a.

On the other hand, when the light L is linearly polarized light vibrating in the z-axis direction, that is, light L2, the light L2 is an ordinary light component and is transmitted as it is. Here, the displacement amount S can be expressed by the following equation (1). S = {[D (b ² -a ^{2)] / 2c 2} sin2φ ... (1} ) However, D; the thickness of the birefringent plate _{a = 1 / n e, b} = 1 / n o n e; birefringence in the angle of the normal direction x and the optical axis a birefringent plate ^{c 2 = a 2 sin 2 φ} + b 2 cos 2 φ; refractive index in the optical axis direction of the plate n _o; refractive index in the direction orthogonal to the optical axis phi is there.

Here, a case where calcite, which is a typical birefringent crystal, is used as an example of the birefringent plate 52 will be described. The refractive index of the incident light wavelengths in the 720nm, for example n _e = 1.65, a n _o = 1.48. At this time, the angle φ between the optical axis a and the normal direction x of the birefringent plate
The displacement amount S1 per 1 mm of the birefringent plate with respect to
Can be expressed as That is, in FIG. 12, the horizontal axis represents the angle (φ) between the normal direction x of the birefringent plate and the optical axis a, that is, the angle (φ) between the optical axis of the birefringent plate and the surface normal of the birefringent plate. And the vertical axis indicates the displacement S1 (μm) per 1 mm thickness of the birefringent plate.

For example, when the angle φ between the optical axis a and the normal direction x of the birefringent plate is set to 5 °, the thickness D (m
The relationship between m) and the amount of displacement S (μm) is proportional as shown in FIG. Therefore, the displacement amount S is set to 21.15 μ, which is half the pitch of the light emitting area 44 in the main scanning direction, 42.3 μm.
m, for example, the optical axis a and the normal direction x of the birefringent plate
And the thickness D may be set to 1.24 mm.

According to the above (1), the displacement amount S is proportional to the thickness D, and the proportionality constant S1 can be determined by the angle φ between the optical axis a and the normal direction x of the birefringent plate. Therefore, by appropriately designing the angle φ between the optical axis a and the normal direction x of the birefringent plate and the thickness D, a desired displacement can be obtained. Next, the operation of the embodiment of the present invention will be described.

FIG. 14 is a light path diagram in the first embodiment of the present invention. FIG. 14 (a) shows a stable state A of liquid crystal molecules to which an electric field -E is applied, and FIG. 14 (b) shows an electric field + E. 4 shows a stable state B of the liquid crystal molecules to which is applied. here,
Consider two light emitting areas of the LED array head. The pitch of the light emitting areas 44 is, for example, 42.3 μm. In the first embodiment of the present invention, the displacement S of the imaging position displacement element is set to, for example, 21.15 μm.

Here, first, as shown in FIG. 14A, the ferroelectric crystal cell portion 50 of the imaging position displacement element is provided with -E.
The case where the liquid crystal molecules are aligned in the stable state A by applying the electric field of FIG. In this stable state A, since the long axis direction (director direction) of the liquid crystal molecules 53 is set to coincide with the main scanning direction of the optical printer, the dichroic dye molecules 54 are also uniformly aligned in the main scanning direction. You.

The light L emitted from the light emitting area 44a is
The light passes through the converging rod lens array 2 and enters the ferroelectric liquid crystal cell unit 50. Of the light incident on the ferroelectric liquid crystal cell unit 50, a component (⇔) having a vibration direction parallel to the main scanning direction is parallel to the long axis (in this case, the absorption axis) of the dichroic dye molecules 54. In the liquid crystal cell, it is absorbed by the dichroic dye and cannot pass through the liquid crystal layer. On the other hand, the component having a vibration direction in the direction orthogonal to the main scanning direction is a polarized light that vibrates in the short axis direction of the dichroic dye molecules 54, and therefore passes through as it is and is output from the ferroelectric liquid crystal cell unit 50. Then, the points k1 and k2 are applied to the birefringent plate 52 of the imaging position displacement element.
Incident from. Since the light incident on the birefringent plate 52 is linearly polarized light that oscillates in a direction orthogonal to the main scanning direction, the birefringent plate 52 has no component in the direction of the optical axis a. Therefore, when outputting from this birefringent plate 52, k
The dots 55 a and 55 b output from 1 ′ and k 2 ′ and face the light emitting areas 44 a and 44 b of the light emitting element array 1 on the photosensitive drum 4 are irradiated.

Next, as shown in FIG. 14 (b), a case where a + E electric field is applied to the ferroelectric liquid crystal cell of the imaging position displacement element 3 to orient the liquid crystal molecules 53 in the stable state B will be described. I do. Since the liquid crystal molecules 53 are uniformly oriented in a direction orthogonal to the main scanning direction of the optical printer, the dichroic dye molecules 54 are also uniformly oriented in a direction orthogonal to the main scanning direction. Of the light incident on the ferroelectric liquid crystal cell unit 50, a component having a vibration direction in a direction perpendicular to the main scanning direction is indicated by a circle ●, which is parallel to the long axis of the dichroic dye molecule 54 (in this case, the absorption axis). In the dielectric liquid crystal cell, it is absorbed by the dichroic dye and cannot pass through the liquid crystal layer. On the other hand, the component ⇔ having a vibration direction parallel to the main scanning direction is polarized light oscillating in the short axis direction of the dichroic dye molecules 54, and therefore passes through as it is and is output from the ferroelectric liquid crystal cell unit 50. Then, the light is incident on the birefringent plate 52 of the imaging position displacement element 3 from points k1 and k2.

Since the direction in which the optical axis of the birefringent plate 52 is projected on the incident surface (the y direction) is aligned with the main scanning direction, the light incident on the birefringent plate 52 vibrates in a direction parallel to the main scanning direction. It becomes linearly polarized light. Since the birefringent plate 52 has a component in the direction of the optical axis a, when the birefringent plate 52 is output, 21.15
The light-emitting areas 44a and 44a of the light-emitting element array 1 on the photosensitive drum 4 are displaced by μm and output from k1 ″ and k2 ″.
The dot 56a displaced by 21.15 μm from the dot 55a facing the dot 4b and the dot 56b displaced by 21.15 μm from the dot 55a are irradiated.

Therefore, using an LED array head having a resolution of 42.3 μm pitch, it is possible to use the LED array head in the main scanning direction.
It is possible to irradiate the photosensitive drum with a resolution of 15 μm. The driving of the first embodiment of the present invention will be described. First, an electric field of -E is applied to the ferroelectric liquid crystal cell of the imaging position displacement element 3 to uniformly align the liquid crystal molecules 53 and the dichroic dye molecules 54 in a direction coincident with the main scanning direction (that is, And stabilize to stable state A). Since the ferroelectric liquid crystal can maintain a stable state even when the electric field is removed,
Here, the electric field may be removed.

The light emitting operation of the LED array head is performed according to the odd number data of the print data for one line in the main scanning direction. At this time, since only polarized light in the direction orthogonal to the main scanning direction can pass through the ferroelectric liquid crystal cell, no displacement of the imaging position occurs. Subsequently, an electric field of + E is applied to the ferroelectric liquid crystal cell of the imaging position displacement element 3 to uniformly align the liquid crystal molecules 53 and the dichroic dye molecules 54 in a direction perpendicular to the main scanning direction (ie, And stabilize to a stable state B).

The light emitting operation of the LED array head is performed according to the even-numbered data in the print data for one line in the main scanning direction. At this time, since the light is displaced by the distance S in the main scanning direction and only the polarized light oscillated in the main scanning direction can pass through the ferroelectric liquid crystal cell, the imaging position is displaced in the main scanning direction and the photosensitive drum 4 is irradiated. I do.

Printing of one line in the main scanning direction is completed, the photosensitive drum 4 is fed in the sub-scanning direction, and the printing operation of the next line is continued. Therefore, it is possible to irradiate the photosensitive drum 4 with the resolution of N / 2 μm in the main scanning direction by using the LED array head having the resolution of N μm pitch using the optical writing device of the embodiment of the present invention. , Can be printed.

In this embodiment, when the main scanning direction is aligned with the direction in which the optical axis of the birefringent plate is projected onto the incident surface, an electric field of -E is applied to the ferroelectric liquid crystal cell to bring the ferroelectric liquid crystal cell into the stable state A. The liquid crystal molecules and the dichroic dye molecules are aligned in the main scanning direction.
When the electric field of E is applied to bring the state to the stable state A, the liquid crystal molecules 5
The same effect can be obtained even if the orientation direction of the trichromatic and dichroic dye molecules 54 is orthogonal to the main scanning direction. In this case, since the displaced light passes through the ferroelectric liquid crystal cell and the light that has not been displaced is absorbed by the ferroelectric liquid crystal cell, it is necessary to perform printing using even data.

FIG. 15 is a diagram schematically showing a configuration of an optical writing device of a light emitting element array printer and a writing light path according to a second embodiment of the present invention. In FIG. 15, 10
1 is a light emitting element array, 102 is a converging rod lens array, 103 is an imaging position displacement element, 104 is a photosensitive drum as a photosensitive medium, and changes the path of the writing light L to change the imaging position. .

FIG. 16 is a diagram showing the configuration of the imaging position displacement element in FIG. As shown in this figure, a birefringent plate 152 and two glass substrates 108, 1 on which transparent electrodes 106, 107 are formed on one surface and an alignment film (not shown) is formed.
The ferroelectric liquid crystal cell portion 150 having a structure in which the alignment film and the transparent electrodes 106 and 107 are opposed to each other via an absorption layer 110 made of liquid crystal and a dichroic dye, and is sealed. And a drive circuit 151 for applying an electric signal to the ferroelectric liquid crystal cell unit 150.

As can be seen from FIGS. 15 and 16, according to the second embodiment of the present invention, the configuration of the imaging position displacement element of the first embodiment is such that the birefringent plate, the two-color It is a ferroelectric liquid crystal cell mixed with a chromatic dye. The structure and operation of the birefringent plate and the structure and operation of the ferroelectric liquid crystal cell are the same as the structure and operation of the birefringent plate and the structure and operation of the ferroelectric liquid crystal cell in the first embodiment. Therefore, detailed description is omitted.

Next, the operation of the second embodiment of the present invention will be described. FIG. 17 is a light path diagram according to the second embodiment of the present invention. Here, two light emitting areas of the LED array head are considered. The pitch of the light emitting area 144 is, for example, 42.3 μm. Light L emitted from the light emitting area 144a passes through the converging rod lens array 102 and is incident on the birefringent plate 152 of the imaging position displacement element 103. The light L is transmitted through the birefringent plate 152,
Linear polarized light having a vibration direction in the direction perpendicular to the main scanning direction
(L2) and linearly polarized light ⇔ (L1) having a vibration direction parallel to the main scanning direction, and L1 is an output point k of L2.
It is output from point k2 displaced by S in the main scanning direction from 1.

Here, first, as shown in FIG. 17A, the case where the electric field of -E is applied to the ferroelectric liquid crystal cell of the imaging position displacement element to orient the liquid crystal molecules in the stable state A. explain. In the stable state A, the liquid crystal molecules 153 are set so that the major axis direction (director direction) of the liquid crystal molecules 153 matches the main scanning direction of the optical printer.
Are also uniformly oriented in the main scanning direction.

Of the light transmitted through the birefringent plate 152, the light L1 displaced by the distance S in the main scanning direction by the birefringent plate 152 is linearly polarized light 振動 having a vibration direction parallel to the main scanning direction. Is absorbed by the dichroic dye in
Cannot pass through the liquid crystal layer. On the other hand, the linearly polarized light (L2) having a vibration direction in the direction orthogonal to the main scanning direction is a polarized light that vibrates in the short axis direction of the dichroic dye molecule 154, and therefore passes through as it is and faces the light emitting area 144a. Drum 1
Irradiate the dots 155a on the pixel 04.

Next, as shown in FIG. 17B, a case where a + E electric field is applied to the ferroelectric liquid crystal cell of the imaging position displacement element 103 to orient the liquid crystal molecules 153 in the stable state B will be described. I do. In this figure, liquid crystal molecules 153 are:
Since the dichroic dye molecules 154 are uniformly oriented in the direction orthogonal to the main scanning direction of the optical printer, the dichroic dye molecules 154 are also uniformly oriented in the direction orthogonal to the main scanning direction. Of the light transmitted through the birefringent plate 152, linearly polarized light (L2) having a vibration direction in a direction orthogonal to the main scanning direction is absorbed by the dichroic dye in the ferroelectric liquid crystal cell and cannot pass through the liquid crystal layer. . On the other hand, the light L displaced by the distance S in the main scanning direction by the birefringent plate 152
Is a linearly polarized light having a vibration direction parallel to the main scanning direction.
Since the polarized light oscillates in the short axis direction of the dichroic dye molecule 154, the light passes through the polarized light as it is and irradiates the dot 156a on the photosensitive drum 104. The dot 156a is shifted by a distance S from the image formation position (dot 155a) when an electric field of -E is applied to the ferroelectric liquid crystal cell.

Here, the displacement amount S can be expressed by the above-mentioned equation (1). A case where calcite, which is a typical birefringent crystal, is used as an example of the birefringent plate 152 will be described. When the incident light wavelength and 720nm, a refractive index at 720nm of calcite, for example, n _e = 1.6
5, is a n _o = 1.48. At this time, the birefringent plate 1 mm corresponds to the angle φ between the optical axis a and the normal direction x of the birefringent plate.
The displacement S1 per contact can be represented as shown in FIG.

For example, when the angle between the optical axis a and the normal direction x of the birefringent plate is φ = 5 °, the relationship between the thickness D and the displacement is proportional as shown in FIG. Accordingly, the displacement amount S is set to a pitch of 42.3 μ in the main scanning direction of the light emitting area 144.
In the case where the half amount of m is set to 21.15 μm, for example, the angle between the optical axis a and the normal direction x of the birefringent plate is φ = 5 °,
The thickness D may be set to 1.24 mm.

From the above equation (1), the displacement amount S is proportional to the thickness D, and the proportionality constant S1 can be determined by the angle φ between the optical axis a and the normal direction x of the birefringent plate 152.
Therefore, by appropriately designing the angle φ between the optical axis a and the normal direction x of the birefringent plate and the thickness D, a desired displacement can be obtained. Therefore, it is possible to irradiate the photosensitive drum with a resolution of 21.15 μm in the main scanning direction using an LED array head having a resolution of 42.3 μm pitch.

The driving of the second embodiment of the present invention will be described. First, an electric field of -E is applied to the ferroelectric liquid crystal cell of the imaging position displacement element 103 to uniformly orient the liquid crystal molecules 153 and the dichroic dye molecules 154 in a direction coinciding with the main scanning direction (ie, And stabilize to stable state A). Since the ferroelectric liquid crystal can maintain a stable state even when the electric field is removed, the electric field may be removed here.

The light emitting operation of the LED array head is performed in accordance with the odd-numbered data in one line of the print data in the main scanning direction. At this time, since only polarized light in the direction orthogonal to the main scanning direction can pass through the ferroelectric liquid crystal cell, no displacement of the imaging position occurs. Subsequently, an electric field of + E is applied to the ferroelectric liquid crystal cell of the imaging position displacement element 103 to uniformly align the liquid crystal molecules 153 and the dichroic dye molecules 154 in a direction orthogonal to the main scanning direction (ie, And stabilize to a stable state B).

The light emitting operation of the LED array head is performed in accordance with the even-numbered data in one line of the print data in the main scanning direction. At this time, since the light is displaced by the distance S in the main scanning direction and only polarized light oscillated in the main scanning direction can pass through the ferroelectric liquid crystal cell, the image forming position is displaced in the main scanning direction and the photosensitive drum 104 is irradiated. I do.

Printing of one line in the main scanning direction is completed, the photosensitive drum 104 is fed in the sub-scanning direction, and the printing operation of the next line is continued. Therefore, using the optical writing device of the second embodiment of the present invention, an LED having a resolution of N μm pitch
Using the array head, it is possible to irradiate the photosensitive drum 104 with a resolution of N / 2 μm in the main scanning direction, and to perform printing.

In the second embodiment, the main scanning direction is aligned with the direction in which the optical axis of the birefringent plate 152 is projected onto the plane of incidence, and an electric field of -E is applied to the ferroelectric liquid crystal cell to change to the stable state A. At this time, the alignment directions of the liquid crystal molecules 153 and the dichroic dye molecules 154 are made to coincide with the main scanning direction. However, when the electric field of -E is applied to the ferroelectric liquid crystal cell to bring the ferroelectric liquid crystal cell into the stable state A, The same effect can be obtained even when the alignment direction of the liquid crystal molecules 153 and the dichroic dye molecules 154 is orthogonal to the main scanning direction.
In this case, the displaced light passes through the ferroelectric liquid crystal cell, and the undisplaced light is absorbed by the ferroelectric liquid crystal cell.
It is necessary to print using even data.

FIG. 18 is a diagram schematically showing the configuration of an optical writing device of a light emitting element array printer and a writing light path according to a third embodiment of the present invention. In FIG.
1 is a light emitting element array, 202 is a converging rod lens array, 203 is an imaging position displacement element, and 204 is a photosensitive drum as a photosensitive medium, which changes the path of the writing light L to change the imaging position. .

FIG. 19 is a view showing the configuration of the imaging position displacement element provided between the light emitting element array and the rod lens array shown in FIG. As shown in this figure, a laminated structure of a ferroelectric liquid crystal cell section 250 and a birefringent plate 252 is formed in order from the light emitting element array 201 side. The ferroelectric liquid crystal cell section 250 has a transparent electrode 2 on one surface.
06 and 207, and an alignment film (not shown) was formed.
The glass substrates 208 and 209 are aligned with the alignment film and the transparent electrode 2.
06, 207 are opposed to each other, arranged at a desired distance, and sealed between the glass substrates 208, 209 via an absorption layer 210 made of liquid crystal and dichroic dye. I have.

Further, it comprises a drive circuit 251 for applying an electric signal to the ferroelectric liquid crystal cell section 250. FIG.
8. As can be seen from FIG. 19, the third embodiment of the present invention
The configuration of the optical writing apparatus according to the first embodiment includes a light emitting element array, a ferroelectric liquid crystal cell mixed with a dichroic dye, a birefringent plate, a converging rod lens array, and a photosensitive drum in the order of writing light. It has become. That is, the position of the converging rod lens array as the image forming means is different from that of the first embodiment.

Therefore, the structure and operation of the birefringent plate and the structure and operation of the ferroelectric liquid crystal cell are the same as those of the first embodiment, and the structure and operation of the ferroelectric liquid crystal cell. Are identical. The operation and the light path of the third embodiment are different from the first embodiment only in the position of the converging rod lens array as the image forming means.
FIG. 20 is a diagram schematically showing a configuration of an optical writing section and a writing light path of a light emitting element array printer according to a fourth embodiment of the present invention.

In FIG. 20, the birefringent plate 3 serving as an imaging position displacement element is arranged in the order of the path of light L from the light emitting element array 301.
52 and a ferroelectric liquid crystal cell portion 35 to which a dichroic dye is added
0, a converging rod lens array 302, and a photosensitive drum 304 as a photosensitive medium. As can be seen from FIG. 20, in the fourth embodiment of the present invention, a light emitting element array, a birefringent plate, a ferroelectric liquid crystal cell mixed with a dichroic dye, a converging rod lens array ,
It is a photosensitive drum. That is, only the position of the converging rod lens array as the image forming means is different from that of the second embodiment.

Accordingly, the structure and operation of the birefringent plate and the structure and operation of the ferroelectric liquid crystal cell are the same as those of the second embodiment. Are identical. The operation and the light path of the fourth embodiment are different from the second embodiment only in the position of the converging rod lens array as the image forming means.
Since the effect is the same, the description is omitted. Also, the driving of the fourth embodiment is the same as that of the second embodiment, and the description is omitted.

FIG. 21 is a diagram schematically showing a configuration of an optical writing device of a light emitting element array printer according to a fifth embodiment of the present invention and a writing light path. In FIG. 21, a ferroelectric liquid crystal cell unit (imaging position displacement element) 450 as a part of the imaging position displacement element and a converging rod lens array 40 are arranged in the order of the path of the writing light L from the light emitting element array 401.
2. Birefringent plate 452 as a part of the imaging position displacement element,
A photosensitive drum 404 as a photosensitive medium, which changes the path of the writing light L to change the image forming position, as in the first embodiment.

As can be seen from FIG. 21, according to the fifth embodiment of the present invention, in the configuration of the optical writing device of the first embodiment, a dichroic dye is mixed in the path of the writing light from the light emitting element array. A ferroelectric liquid crystal cell, a converging rod lens array, a birefringent plate, and a photosensitive drum. That is, the ferroelectric liquid crystal cell of the image forming position displacing means and the birefringent plate are separated, and a converging rod lens array as the image forming means is disposed between them to form an image.

Therefore, the structure and operation of the birefringent plate, the design method, and the structure and operation of the ferroelectric liquid crystal cell are the same as those of the first embodiment. The structure and operation of the cell are the same. The operation and light path of the fifth embodiment are the same as those of the first embodiment except that the position of the converging rod lens array serving as the image forming means is different from that of the first embodiment. Is omitted.

FIG. 22 is a diagram schematically showing a configuration of an optical writing section of a light emitting element array printer according to a sixth embodiment of the present invention and a writing light path. In FIG. 22, a birefringent plate 552, a converging rod lens array 502, and a ferroelectric liquid crystal cell unit 550 to which a dichroic dye is added are arranged in the order of the light emitting element array 501 and the path of the writing light L emitted from the light emitting element array 501. And a photosensitive drum 504 as a photosensitive medium, which changes the path of the writing light L to change the image forming position, as in the third embodiment.

As can be seen from FIG. 22, in the sixth embodiment of the present invention, a light emitting element array, a birefringent plate, a converging rod lens array, and a ferroelectric mixed with a dichroic dye are arranged in the order of the path of writing light. Liquid crystal cell and photosensitive drum.
That is, the ferroelectric liquid crystal cell of the image forming position displacing means and the birefringent plate are separated, and a converging rod lens array as the image forming means is disposed between them to form an image.

Therefore, the structure and operation of the birefringent plate, the design method, and the structure and operation of the ferroelectric liquid crystal cell are the same as those of the second embodiment. The structure and operation of the cell are the same. The operation and light path of the sixth embodiment are different from those of the second embodiment only in the position of the converging rod lens array serving as the image forming means. Omitted.

In the present invention, any type of birefringent plate may be used as long as it can separate polarized light and can be displaced by a desired distance. Further, the present invention is not limited to the above-described embodiments, and various modifications are possible based on the gist of the present invention, and these are not excluded from the scope of the present invention.

[0078]

As described above, according to the present invention, the following effects can be obtained. By switching the polarity of the electric signal applied to the ferroelectric liquid crystal cell, light is imaged at a position facing the light emitting element array on the photosensitive medium, or at a position displaced by a predetermined distance. be able to.

Therefore, when the light emitting operation of the LED array head is performed in accordance with the odd data of the print data of one line, and when the light emitting operation of the LED array head is performed in accordance with the even data of the print data of one line. Sometimes, by switching the polarity of the electric signal applied to the ferroelectric liquid crystal cell of the imaging position displacement element, using an LED array head having a resolution of N μm pitch in the main scanning direction,
Irradiation can be performed on the photosensitive drum at a resolution of N / 2 μm in the main scanning direction, and printing can be performed.

Thus, printing can be performed at a high resolution using a light emitting element array printer having a low resolution.
Conversely, printing can be performed at a higher resolution by using a high-resolution light emitting element array printer. Further, in a printer image forming optical system including a light emitting element array, a photosensitive drum, and a rod lens array, the image forming position displacement means of the present invention must be installed in a limited space between focal lengths. As shown in the embodiment, in the present invention, since the order of the constituent elements can be changed variously, there is also an effect that the degree of freedom in installing the imaging position displacement element is large.

[Brief description of the drawings]

FIG. 1 is a diagram schematically illustrating a configuration of an optical writing device of a light emitting element array printer and a writing light path according to a first embodiment of the present invention.

FIG. 2 is a schematic view of a conventional LED printer.

FIG. 3 is an enlarged perspective view of an optical imaging system of a conventional light emitting element array printer.

FIG. 4 is a conceptual diagram of an optical imaging system of a conventional light emitting element array printer.

FIG. 5 is a plan view of a conventional LED array head.

FIG. 6 is a diagram showing a light emitting unit of the LED array head.

FIG. 7 is a perspective view showing a boundary portion of the LED array chip.

FIG. 8 is a diagram showing a configuration of an imaging position displacement element in FIG. 1;

FIG. 9 is a schematic diagram illustrating switching of ferroelectric liquid crystal in the optical writing device of the light emitting element array printer according to the first embodiment of the present invention.

FIG. 10 is a schematic diagram showing an operation of a ferroelectric liquid crystal cell in which a ferroelectric liquid crystal and a dichroic dye are sealed.

FIG. 11 is an explanatory diagram showing the structure and operation of a birefringent plate in an imaging position displacement element.

FIG. 12 is a diagram illustrating an angle between an optical axis of the birefringent plate and a surface normal of the birefringent plate, and a displacement per 1 mm thickness of the birefringent plate.

FIG. 13 is a diagram illustrating a relationship between a thickness D of a birefringent plate and a displacement amount S.

FIG. 14 is a light path diagram according to the first embodiment of the present invention.

FIG. 15 is a diagram schematically showing a configuration of an optical writing device of a light emitting element array printer and a writing light path according to a second embodiment of the present invention.

16 is a diagram showing a configuration of an imaging position displacement element in FIG.

FIG. 17 is a light path diagram according to the second embodiment of the present invention.

FIG. 18 is a diagram schematically showing a configuration of an optical writing device of a light emitting element array printer and a writing light path according to a third embodiment of the present invention.

19 is a diagram showing a configuration of the imaging position displacement element installed between the light emitting element array and the rod lens array shown in FIG.

FIG. 20 is a diagram schematically showing a configuration of an optical writing unit and a writing light path of a light emitting element array printer according to a fourth embodiment of the present invention.

FIG. 21 is a diagram schematically showing a configuration of an optical writing device of a light emitting element array printer and a writing light path according to a fifth embodiment of the present invention.

FIG. 22 is a diagram schematically illustrating a configuration of an optical writing unit and a writing light path of a light emitting element array printer according to a sixth embodiment of the present invention.

[Explanation of symbols]

1, 101, 201, 301, 401, 501 Light emitting element array 2, 102, 202, 302, 402, 502 Focusing rod lens array 3, 103, 203, 303 Imaging position displacement element 4, 104, 204, 304, 404, 504 Photoconductor drum 6, 7, 106, 107, 206, 207 Transparent electrode 8, 9, 108, 109, 208, 209 Glass substrate 10, 110, 210 Absorption layer 44, 44a, 44b, 144, 144a, 144b
Light-emitting area 50, 150, 250, 350, 450, 550 Ferroelectric liquid crystal cell section 51, 151, 251 Drive circuit 52, 152, 252, 352, 452, 552 Birefringent plate 53, 153 Liquid crystal molecules 54, 154 2 colors Sex dye molecules 55a, 55b, 56a, 56b, 155a, 156a
Dot

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-6-24039 (JP, A) JP-A-60-93894 (JP, A) JP-A-61-23118 (JP, A) JP-A-7- 36054 (JP, A) JP-A-1-179019 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B41J 2/44 B41J 2/45 B41J 2/455 G02F 1/13- 1/141

Claims (9)

(57) [Claims] A light-emitting element array head comprising a plurality of light-emitting elements; and a photosensitive medium disposed opposite to the light-emitting element array head and receiving light emitted by the light-emitting elements to form an electrostatic latent image. An optical writing device for a light-emitting element array printer having a converging rod lens disposed between the light-emitting element array head and the photosensitive medium and converging light emitted by the light-emitting element to form an image on the photosensitive medium; Between the converging rod lens and the photosensitive medium, a dichroic dye having an absorption wavelength at the wavelength of the writing light is added in order from the converging rod lens side, and the absorption axis of the dichroic dye molecule is applied to the applied electric field. A ferroelectric liquid crystal cell that is uniformly aligned in the main scanning direction and the sub-scanning direction in accordance with the polarity, and a light incident surface set at a predetermined angle with respect to the optical axis, having a predetermined thickness, Axial component polarization at desired distance And a birefringent plate which can be only displaced, the optical writing device of the light emitting element array printer, characterized by arranging the imaging position displacement means. 2. An optical writing device for a light emitting element array printer according to claim 1, wherein a displacement direction of said imaging position displacement means is a main scanning direction of the light emitting element array printer, and a displacement distance is light emission of the light emitting element array. An optical writing device for a light-emitting element array printer, wherein the distance is half the distance between elements. 3. A light-emitting element array head comprising a plurality of light-emitting elements, and a photosensitive medium disposed opposite to the light-emitting element array head and receiving light emitted by the light-emitting elements to form an electrostatic latent image. An optical writing device for a light-emitting element array printer having a converging rod lens disposed between the light-emitting element array head and the photosensitive medium and converging light emitted by the light-emitting element to form an image on the photosensitive medium; Between the converging rod lens and the photosensitive medium, in order from the converging rod lens side, a light incident surface is set at a predetermined angle with respect to the optical axis, has a predetermined thickness, and has an optical axis direction component. A birefringent plate capable of displacing polarized light by a desired distance, and a dichroic dye having an absorption wavelength at the wavelength of the writing light are added, and the absorption axis of the dichroic dye molecule is changed according to the polarity of the applied electric field. Uniformly in the main scanning direction and The optical writing device of the light emitting element array printer, characterized by arranging the imaging position displacement means including a ferroelectric liquid crystal cell aligned in 査 direction. 4. The light writing device for a light emitting element array printer according to claim 3, wherein a displacement distance of said image forming position displacement means is 1/2 of a distance between light emitting elements of the light emitting element array, and a displacement direction is. An optical writing device for a light emitting element array printer, which is in a main scanning direction of the light emitting element array printer. 5. A light-emitting element array head comprising a plurality of light-emitting elements, and a photosensitive medium disposed opposite to the light-emitting element array head and receiving light emitted by the light-emitting elements to form an electrostatic latent image. An optical writing device for a light emitting element array printer, comprising a converging rod lens disposed between the light emitting element array head and the photosensitive medium and converging light emitted by the light emitting element to form an image on the photosensitive medium. A dichroic dye having an absorption wavelength at the wavelength of the writing light is added between the light emitting element array head and the converging rod lens in order from the light emitting element array head side.
A ferroelectric liquid crystal cell that uniformly aligns the absorption axis of chromatic dye molecules in the main scanning direction and sub-scanning direction according to the polarity of the applied electric field, and sets the light incident surface at a predetermined angle to the optical axis A birefringent plate having a predetermined thickness and capable of displacing polarized light in the direction of the optical axis by a desired distance; and a light emitting element array provided with image forming position displacing means. Optical writing device for printers. 6. A light-emitting element array head comprising a plurality of light-emitting elements, and a photosensitive medium disposed opposite to the light-emitting element array head and receiving light emitted by the light-emitting elements to form an electrostatic latent image. An optical writing device for a light emitting element array printer, comprising a converging rod lens disposed between the light emitting element array head and the photosensitive medium and converging light emitted by the light emitting element to form an image on the photosensitive medium. A light incident surface is set between a light emitting element array head and the converging rod lens at a predetermined angle with respect to an optical axis in order from the light emitting element array head side, and has a predetermined thickness, A birefringent plate capable of displacing the polarization of the directional component by a desired distance, and a dichroic dye having an absorption wavelength at the wavelength of the writing light are added, and the absorption axis of the dichroic dye molecule is adjusted to the polarity of the applied electric field. Uniform according to And a ferroelectric liquid crystal cell aligned in the main scanning direction and the sub-scanning direction, the optical writing device of the light emitting element array printer, characterized by arranging the imaging position displacement means. 7. A light-emitting element array head comprising a plurality of light-emitting elements, and a photosensitive medium disposed to face the light-emitting element array head and receiving light emitted by the light-emitting elements to form an electrostatic latent image. An optical writing device for a light emitting element array printer, comprising a converging rod lens disposed between the light emitting element array head and the photosensitive medium and converging light emitted by the light emitting element to form an image on the photosensitive medium. A dichroic dye having an absorption wavelength at the wavelength of the writing light is added between the light emitting element array head and the converging rod lens, and the absorption axis of the dichroic dye molecules is made uniform according to the polarity of the applied electric field. A ferroelectric liquid crystal cell oriented in the main scanning direction and the sub-scanning direction is installed, and a light incident surface is set at a predetermined angle with respect to an optical axis between the converging rod lens and the photosensitive medium. Has a predetermined thickness, And the polarization of the optical axis direction component placing a birefringent plate capable of only displaced a desired distance, the optical writing device of the light emitting element array printer, characterized by arranging the imaging position displacement means. 8. A light-emitting element array head including a plurality of light-emitting elements, and a photosensitive medium disposed opposite to the light-emitting element array head and receiving light emitted by the light-emitting elements to form an electrostatic latent image. An optical writing device for a light emitting element array printer, comprising a converging rod lens disposed between the light emitting element array head and the photosensitive medium and converging light emitted by the light emitting element to form an image on the photosensitive medium. A light incident surface is set at a predetermined angle with respect to an optical axis between a light emitting element array head and the converging rod lens,
A birefringent plate having a predetermined thickness and capable of displacing polarized light in the direction of the optical axis by a desired distance is provided, and between the converging rod lens array and the photosensitive medium, the wavelength of the writing light is adjusted. A dichroic dye having an absorption wavelength is added, and a ferroelectric liquid crystal cell is installed in which the absorption axis of the dichroic dye molecules is uniformly aligned in the main scanning direction and the sub-scanning direction according to the polarity of the applied electric field. An optical writing device for a light-emitting element array printer, comprising: an imaging position displacement unit. 9. The light writing device for a light emitting element array printer according to claim 5, wherein the displacement distance in the imaging position displacement means is 1/2 of the distance between the light emitting elements of the light emitting element array. The light emitting device array printer optical writing device, wherein the displacement direction is the main scanning direction of the light emitting device array printer.