JPH08166555A - LED array head - Google Patents

Abstract

(57) An object of the invention is to realize an LED array head in which variations in light quantity and variations in beam spot diameter are small. An LED having a plurality of light emitting sources.
(Light Emitting Diode) In an LED array head that performs optical writing on an image surface 5 of a photoconductor or the like by using an LED array light source in which a plurality of array chips 1 are arrayed, a cycle of each LED array chip 1 An imaging optical system composed of a microlens array 2 corresponding to is arranged, and each microlens 2a is an imaging lens composed of a single lens including an aspheric surface in which aberrations such as field curvature are well corrected. It is characterized by being configured. Therefore, according to the present invention, it is possible to realize an LED array head with less variation in light quantity and variation in beam spot diameter by using an inexpensive microlens array.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an LED array head applied to a writing optical system such as an optical printer, a digital copying machine and a facsimile.

[0002]

2. Description of the Related Art An LED array head using an LED element as a light source is a raster scan system using a semiconductor laser (LD) and a scanning optical system (a deflector such as a rotating polygon mirror and an imaging lens for constant velocity scanning). Compared with, there is no mechanical operation part, so there are advantages that it is highly reliable against vibration and noise and that it is advantageous for downsizing. On the other hand, there is a problem that the light amount variation within one line is large and the beam spot shape is likely to be nonuniform among the dots. Such variations in light amount and disturbance of the beam spot cause density unevenness such as black streaks on the output image, and are particularly likely to appear remarkably in the case of a multivalued image such as a photographic image. Such a variation in the light amount and the disturbance of the beam spot largely depend on the imaging optical element such as the rod lens array rather than the LED itself. That is, 1. Since a light amount loss occurs at the joints of the image forming optical elements (rod lens array, GRIN lens array, roof mirror lens array, etc.), a light amount variation matching the cycle of the joints occurs (the pitch between the LED light emitting element and the image forming optical element). Are different), 2. Due to the generation of flare light such as reflected light in the imaging optical element, it is difficult to converge into a uniform beam, and a uniform beam spot cannot be obtained.

[0003]

A conventional LED array head has a rod lens array (for example, SELFOC lens array (S manufactured by Nippon Sheet Glass Co., Ltd.) as an imaging optical system.
Erecting equal-magnification imaging elements such as LA) and roof mirror lens array (RMLA) have been used. However, such an erecting equal-magnification imaging element has a problem that the light amount variation and the beam spot variation due to the joint between the lenses are large as described above.

The present invention has been made in view of the above circumstances, and an object of the present invention is to realize an LED array head having a small variation in light amount and a small variation in beam spot diameter as described above.

[0005]

As a means for achieving the above object, the invention according to claim 1 is configured by arranging a plurality of LED (light emitting diode) array chips having a plurality of light emitting sources in an array. In an LED array head that uses an LED array light source to perform optical writing on an image surface of a photoconductor or the like, an imaging optical system including a microlens array corresponding to a cycle of each LED array chip is arranged, and Each microlens is characterized in that it is composed of an imaging lens composed of a single lens including an aspherical surface in which aberration such as field curvature is well corrected.

The invention according to claim 2 is the L according to claim 1.
In the ED array head, when the dot (light emitting source) position of each LED array chip and the writing position on the image plane are reversed at the chip cycle, the connection is reversed in advance at the time of wire bonding to the electrode pattern of the LED array chip. Is characterized by.

The invention according to claim 3 is the L according to claim 1.
In the ED array head, when the dot (light emitting source) position of each LED array chip and the writing position on the image plane are inverted at the chip cycle, the write data is inverted in advance in the memory. .

The invention according to claim 4 is the L according to claim 1.
The ED array head is characterized in that the electrode pattern of the LED array chip is inclined so that the emission direction of each light emitting source of each LED array chip is focused near the center of the microlens.

The invention according to claim 5 is the L according to claim 1.
In the ED array head, the emission end face of the LED array chip has a convex surface in the dot arrangement direction so that the emission direction from each light emitting source of each LED array chip is focused near the center of the microlens.

The invention according to claim 6 is the L according to claim 1.
The ED array head is characterized in that a light shielding plate is provided between the LED array chips to reduce the crosstalk of the light flux between the chips.

The invention according to claim 7 is the L according to claim 1.
The ED array head is characterized in that the optical power is arranged such that the lateral magnification of the microlens is 1 or more.

In the LED array head according to any one of claims 1 to 7, the image forming optical system including the microlens array corresponding to the cycle of each LED array chip is arranged, and each microlens has an image. Each microlens of the microlens array is arranged corresponding to each LED array chip because it is composed of an imaging lens consisting of a single lens including an aspherical surface in which aberrations such as surface curvature are satisfactorily corrected. Since the joint portion of the LED array chip corresponds to the joint portion between the LED array chips, if the light flux from each light emitting source of the LED array chip is configured to gather near the center of the microlens, the light amount variation due to the joint portion between the lenses and It is possible to reduce variations in beam spot diameter.

As another means for achieving the above object, the invention according to claim 8 is an L having a plurality of light emitting sources.
An LED array light source in which a plurality of ED (light emitting diode) array chips are arranged in an array and a microlens array are used to perform optical writing on an image surface of a photoconductor or the like.
In the ED array head, the LED light emitting elements on the LED array chip are grouped so as to match the arrangement period of the microlenses, and each microlens is
It is characterized in that it is composed of an imaging lens composed of a single lens including an aspherical surface in which aberrations such as field curvature are well corrected.

The invention according to claim 9 is the L according to claim 8.
In the ED array head, when the dot (light emitting source) position of the LED light emitting element group divided into groups on each LED array chip and the writing position on the image plane are inverted at the microlens cycle, the group on the LED array chip It is characterized in that the wire connection is reversed in advance at the time of wire bonding to the electrode patterns of the divided LED light emitting element groups.

According to a tenth aspect of the present invention, in the LED array head according to the eighth aspect, the dot (light emitting source) positions of the LED light emitting element groups divided into groups on each LED array chip and the writing position on the image plane. Is characterized in that the write data is inverted in advance in the memory when the data is inverted at the microlens cycle.

According to an eleventh aspect of the present invention, in the LED array head according to the eighth aspect, the emission direction of each group of LED light emitting elements on each LED array chip from each light emitting source is the center of the microlens. It is characterized in that the electrode patterns of the LED light emitting element groups divided into groups on the LED array chip are inclined so as to be focused in the vicinity.

According to a twelfth aspect of the present invention, in the LED array head according to the eighth aspect, a light shielding plate is provided between the grouped LED light emitting elements on each LED array chip, and the group on the LED array chip is provided. Divided L
The feature is that crosstalk of the light flux between the ED light emitting element groups is reduced.

According to a thirteenth aspect of the present invention, in the LED array head according to the eighth aspect, the optical power arrangement is such that the lateral magnification of the microlens is 1 or more.

In the LED array head according to any one of claims 8 to 13, the LED light emitting elements on the LED array chip are grouped so as to match the cycle of arrangement of the microlenses, and each microlens has an image plane. Since each microlens of the microlens array is composed of a single lens including an aspherical surface in which aberrations such as curvature are well corrected, each microlens of the microlens array is grouped into LED light emitting element groups on each LED array chip. Corresponding to the grouped LED light emitting element groups on the LED array chip, the grouped LEDs on the LED array chip are connected to each other.
If the light beams from the light emitting sources of the light emitting element group are configured to be gathered in the vicinity of the center of the microlens, it is possible to reduce the light amount variation and the beam spot diameter variation due to the joint between the lenses.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. First, the first embodiment will be described. FIG. 1 is a schematic configuration diagram of an LED array head showing an example of the first embodiment of the present invention.
As shown in FIG. 1, the LED array head of the present invention uses an LED array light source in which a plurality of LED array chips 1 having a plurality of light emitting sources (LEDs) are arranged in an array, and each LED of the LED array light source is used. An image forming optical system composed of a microlens array 2 corresponding to the cycle of each LED array chip is arranged facing the array chip 1 (claim 1).

Here, the LED array chip 1 may be either a surface emitting type or an edge emitting type. In addition, the LED array chip 1 usually has a structure in which several tens of light emitting sources (LEDs) are arranged in an array in a chip of several mm square, and the LED array chip 1 has a structure of light emitting sources. An electrode pattern (not shown) including the same number of electrodes is formed.

In this embodiment, as described above, each of the microlenses 2a having a size substantially the same as the size of the LED array chip 1 is formed in each L.
It is characterized by having an imaging optical system (microlens array) 2 arrayed corresponding to each ED array chip, and the luminous flux emitted from a plurality of light emitting sources of one LED array chip 1 is The LED array chip 1
Image plane 5 such as a photoconductor by a microlens 2a corresponding to
It is imaged as a beam spot on the top.

Each of the microlenses 2a constituting the microlens array 2 is composed of an imaging lens composed of a single lens, but it is preferable that the microlenses 2a have an aspherical surface in which aberrations such as field curvature are well corrected. desirable. Further, since the microlens 2a is composed of a single lens, the microlens array 2 can be mass-produced at low cost by the plastic molding technique.

In this configuration, the microlens array 2 is used.
In order to prevent variation in the amount of light at the joint between the microlenses 2a, the luminous flux from each light emitting source of the LED array chip 1 is gathered near the center of the microlens 2a. In this case, the light emission on the LED array chip is emitted. The position of the source (light emitting dot) and the writing position on the image plane 5 are the microlens 2
Since it is inverted by a, it is necessary to invert the write data by other means in advance.

Here, in the LED array head having the structure shown in FIG. 1, the means for inverting the write data is to reverse the connection in advance at the time of wire bonding to the electrode of each light emitting source (LED) of the LED array chip 1. (Claim 2). That is, it is reversed at the time of wire bonding connection or on the substrate wiring.

As another means for inverting the write data, the write data is inverted in the memory in advance (claim 3). That is, the data is inverted in LED array chip units on the memory of the LED array drive driver circuit (not shown).

Next, in the LED array head having the configuration shown in FIG. 1, as described above, the directions of the luminous fluxes emitted from the respective light emitting sources (LEDs) of the LED array chip 1 gather near the center of the microlens 2a. With this structure, it is possible to realize an optical system in which the loss of the light amount at the joint of the lenses is small and the variation in the light amount is small.

Therefore, in this embodiment, as shown in FIG.
The respective electrodes 3 of the LED array chip 1 are arranged so as to be inclined by θ, and the luminous fluxes emitted from the respective LEDs of the LED array chip 1 are each focused near the center of the microlens 2a (claim 4). . The inclination θ of each electrode 3 on the LED array chip 1 differs depending on the electrode arrangement position, and the inclination θ of the electrode at the central portion of the LED array chip 1 is almost 0. The inclination θ becomes large.

As described above, the LE having the configuration shown in FIG.
In the D array head, the direction of the light flux emitted from each LED of the LED array chip 1 is gathered in the vicinity of the center of the microlens 2a, so that an optical system with little light amount loss at the joints of the lenses and little light amount variation However, as another means for collecting the direction of the light flux emitted from each LED in the vicinity of the center of the microlens 2a, as shown in FIG. 3, the emission end face 1a of the LED array chip 1 is arranged in the dot arrangement direction. With the configuration having the convex surface, the direction of the light flux emitted from each LED can be focused near the center of the microlens 2a (claim 5).

Here, the convex surface is, for example, an LED.
When the refractive index of the active layer of the array chip 1 is n, the distance from the emitting end face 1a to the microlens 2a is S, and the radius of curvature of the emitting end face 1a is R, {(n-1) S · 9/10} < R <{(n-1) S ・ 11
It is desirable to satisfy the relationship of / 10}.

Next, in the LED array head having the structure shown in FIG. 1, as shown in the drawing, each LED array chip 1
By providing the light shielding plate 4 between the LED array chips, it is possible to reduce the crosstalk of the light flux between the LED array chips (claim 6). Here, it is desirable that the light shielding plate 4 is coated with black paint or has a rough surface. Further, the light shielding plate 4 and the microlens array 2 may be integrated.

Next, in the LED array head of the present invention, as shown in the embodiment of FIG. 4, the distance from the emission end face 1a of the LED array chip 1 to the microlens 2a is S ₁ , and the microlens 2a to the image plane. S ₂ up to 5
In such a case, it is advisable to adopt an optical power arrangement in which the lateral magnification β = S ₂ / S _{1 of the} microlens 2a is 1 or more (claim 7). That is, by setting the lateral magnification β to 1 or more,
The interval ω between the LED array chips 1 can be widened, chipping defects when mounting the LED array chips 1 on a substrate can be reduced, and the cutting accuracy of the LED array chips can be roughened.

The first embodiment of the present invention has been described above. Next, the second embodiment of the present invention will be described. FIG. 5 is a schematic configuration diagram of an LED array head showing an example of the second embodiment of the present invention. As shown in FIG. 5, the LED array head of the present invention uses an LED array light source in which a plurality of LED array chips 1 having a plurality of light emitting sources (LEDs) are arranged in an array.
The LED light emitting elements on each LED array chip 1 of the D array light source are divided into some groups (LED light emitting element groups) 6, and the grouped LED light emitting element groups 6
And the microlens array 2 are arranged so that the cycles thereof match (claim 8).

Here, the LED array chip 1 may be either a surface emitting type or an edge emitting type. In addition, the LED array chip 1 usually has a structure in which several tens of light emitting sources (LEDs) are arranged in an array in a chip of several mm square, and the LED array chip 1 has a structure of light emitting sources. An electrode pattern (not shown) including the same number of electrodes is formed.

In this embodiment, as described above, the microlenses 2a are grouped into L on the LED array chip 1.
It is characterized by having an imaging optical system (microlens array) 2 arrayed corresponding to the ED light emitting element group 6, and the LED light emitting element group 6 is divided into groups on one LED array chip 1. The light beams emitted from the plurality of light emitting sources are imaged as beam spots on the image plane 5 of the photoconductor or the like by the microlenses 2a corresponding to the grouped LED light emitting elements 6 on the LED array chip 1. It

Each microlens 2a constituting the microlens array 2 is composed of an image-forming lens made of a single lens, but preferably has an aspherical surface in which aberrations such as field curvature are well corrected. desirable. Further, since the microlens 2a is composed of a single lens, the microlens array 2 can be mass-produced at low cost by the plastic molding technique.

In this structure, the microlens array 2 is used.
In order to prevent the variation in the amount of light at the joint between the microlenses 2a, the luminous fluxes emitted from the light emitting sources of the LED light emitting element groups 6 grouped on the LED array chip 1 are gathered near the center of the microlens 2a. But
In this case, since the light emitting source (light emitting dot) position of the grouped LED light emitting element groups 6 on the LED array chip 1 and the writing position on the image plane 5 are inverted by the microlens 2a, writing is performed by other means. It is necessary to invert the data beforehand.

Here, in the LED array head having the structure shown in FIG. 5, as means for inverting the write data, the LEs divided into groups on the LED array chip 1 are used.
The wire connection is previously reversed at the time of wire bonding to the electrode of each light emitting source (LED) of the D light emitting element group 6 (claim 9). That is, it is reversed at the time of wire bonding connection or on the substrate wiring.

As another means for inverting the write data, the write data is inverted in the memory in advance (claim 10). That is, the data is inverted for each LED light emitting element group unit on the LED array chip 1 in the memory of the LED array driving driver circuit (not shown).

Next, in the LED array head having the configuration shown in FIG. 5, as described above, the luminous flux emitted from each light emitting source (LED) of the LED light emitting element group 6 divided into groups on the LED array chip 1. By arranging the light beams in the vicinity of the center of the microlens 2a, it is possible to realize an optical system in which the light amount loss at the joints of the microlenses is small and the light amount variation in the microlens cycle is small.

Therefore, in this embodiment, as shown in FIG.
The electrodes 3 of the grouped LED light emitting element groups 6 on the LED array chip 1 are arranged with an inclination of θ, and the luminous fluxes emitted from the respective light emitting sources of the grouped LED light emitting element groups 6 on the LED array chip 1 are arranged. Is focused near the center of each corresponding microlens 2a (claim 11).

The inclination θ of each electrode 3 of the grouped LED light emitting element groups 6 on the LED array chip 1 differs depending on the arrangement position of the electrodes, and the grouped LED light emitting element groups 6 on the LED array chip 1 are arranged. The inclination θ of the electrode at the central portion is almost 0, and the inclination θ becomes larger for the electrodes on both ends of the LED light emitting element group 6 divided into groups on the LED array chip 1.

Next, in the LED array head having the structure shown in FIG. 5, each LED array chip 1 as shown in FIG.
By providing the light shielding plate 4 between the LED light emitting element groups 6 which are divided into the upper groups, it is possible to reduce the crosstalk of the luminous flux between the LED light emitting element groups 6 which are divided into the group on the LED array chip 1. It is possible (claim 12).
Here, it is desirable that the light shielding plate 4 is coated with black paint or has a rough surface. Further, the light shielding plate 4 and the microlens array 2 may be integrated.

Next, in the LED array head of the present invention, as shown in the embodiment of FIG. 7, the distance from the emitting end face 1a of the LED array chip 1 to the microlens 2a is S ₁ , and the microlens 2a to the image plane. S ₂ up to 5
Then, the optical power arrangement is such that the lateral magnification β = S ₂ / S _{1 of the} microlens 2a becomes 1 or more.
3). That is, by setting the lateral magnification β to 1 or more,
The LED light emitting element groups 6 divided into groups on the LED array chip 1 can be made smaller by the magnification, and L
The ED array chip 1 itself becomes smaller, resulting in LE
The distance ω between the D array chips 1 can be widened, and L
The chipping defects when mounting the ED array chip 1 on the substrate are reduced, and the cutting accuracy of the LED array chip can be made rough.

[0045]

As described above, the L according to claim 1
In the ED array head, an imaging optical system composed of a microlens array corresponding to the period of each LED array chip is arranged, and each microlens is a non-corrected aberration such as a field curvature. By using an imaging lens composed of a single lens including a spherical surface, it is possible to realize an LED array head with less variation in light quantity and variation in beam spot diameter by using an inexpensive microlens array.

In the LED array head according to the second aspect of the invention, when the dot (light emitting source) position of each LED array chip and the writing position on the image plane are reversed at the chip cycle, the LE is used.
By inverting the connection in advance during wire bonding to the electrode pattern of the D array chip, the write data to be inverted by the microlens can be inverted in advance by a simple means, so that a complicated circuit is not required.

In the LED array head according to the present invention, when the dot (light emitting source) position of each LED array chip and the writing position on the image plane are reversed at the chip cycle, the writing data is previously stored in the memory. By inverting, the write data to be inverted by the microlens can be inverted in advance by a simple means, so that a complicated circuit is not required.

In the LED array head according to the fourth aspect, the electrode pattern of the LED array chip is inclined so that the emission direction from each light emitting source (LED) of the LED array chip is focused near the center of the microlens. By providing the above, it is possible to reduce the light amount loss at the joint of the microlenses and the light amount variation in the chip period.

In the LED array head according to the present invention, the emission end face of the LED array chip is dot-shaped so that the emission direction from each light emitting source (LED) of the LED array chip is focused near the center of the microlens. By having the convex surface in the arrangement direction, it is possible to reduce the light amount loss and the light amount variation in the chip period.

In the LED array head according to the sixth aspect, a light shielding plate is provided between the LED array chips to reduce the crosstalk of the luminous flux between the chips.
Crosstalk of write data between chips can be reduced.

In the LED array head according to the seventh aspect of the invention, by arranging the optical power such that the lateral magnification of the microlens is 1 or more, a wide space can be secured between the LED array chips, and the substrate of the LED array chip can be secured. It can be easily mounted on the top and the cutting accuracy of the LED array chip can be made rough.

In the LED array head according to the present invention, L is arranged so as to match the cycle of the microlens array.
The LED light-emitting elements on the ED array chip are divided into groups, and each microlens is composed of an imaging lens made up of a single lens including an aspherical surface in which aberrations such as field curvature are well corrected, so that the amount of light is increased. It is possible to realize an LED array head with less variation and less variation in beam spot diameter. Further, since an inexpensive microlens array is used, an inexpensive LED array head can be realized.

In the LED array head according to the ninth aspect, the grouped L on each LED array chip is used.
When the dot (light emitting source) position of the ED light emitting element group and the writing position on the image plane are reversed at the microlens cycle, at the time of wire bonding to the electrode pattern of the grouped LED light emitting element groups on the LED array chip. By inverting the connection in advance, the write data to be inverted by the microlens can be inverted in advance by a simple means, so that a complicated circuit is not required.

In the LED array head according to the tenth aspect, the dot (light emitting source) position of the grouped LED light emitting elements on each LED array chip and the writing position on the image plane are inverted at the microlens cycle. In this case, by inverting the write data in the memory in advance, the write data to be inverted by the microlens can be inverted in advance by a simple means, so that a complicated circuit is not required.

In the LED array head according to the eleventh aspect of the present invention, the emitting directions of the LED light emitting element groups grouped on the LED array chips from the respective light emitting sources are focused near the center of the microlens. The electrode pattern of the LED light emitting element group divided into groups on the LED array chip is inclined so that the emission direction of each light emitting source of the LED light emitting element group is focused near the center of the microlens. Therefore, it is possible to reduce the light amount loss at the joints of the microlenses and the light amount variation in the microlens cycle.

In the LED array head according to the twelfth aspect, when the crosstalk of the write data between the grouped LED light emitting elements on each LED array chip becomes a problem, the group on each LED array chip. By providing the light shielding plate between the divided LED light emitting element groups, crosstalk can be easily reduced.

In the LED array head according to the thirteenth aspect, by arranging the optical power such that the lateral magnification of the microlens is 1 or more, a wide space can be secured between the LED array chips and the substrate of the LED array chip can be provided. It can be easily mounted on the top and the cutting accuracy of the LED array chip can be made rough.

[Brief description of drawings]

FIG. 1 is a plan view of an essential part of an LED array head showing an embodiment of claims 1 and 6. FIG.

FIG. 2 is a plan view of an essential part of an LED array head showing an embodiment of claim 4;

FIG. 3 is a plan view of an essential part of an LED array head showing an embodiment of claim 5;

FIG. 4 is a plan view of an essential part of an LED array head showing an embodiment of claim 7;

FIG. 5 is a plan view of an essential part of an LED array head showing an embodiment of claims 8 and 12;

FIG. 6 is a plan view of an essential part of an LED array head showing an embodiment of claim 11;

FIG. 7 is a plan view of an essential part of an LED array head showing an embodiment of claim 13;

[Explanation of symbols]

 1: LED array chip 1a: emission end face 2: microlens array 2a: microlens 3: electrode 4: light shielding plate 5: image plane 6: LED light emitting element group

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location B41J 2/455 G02B 3/00 A H01L 33/00 MH04N 1/036 A

Claims (13)

[Claims] 1. An L (light emitting diode) array chip having a plurality of light emitting sources arranged in an array.
In an LED array head that uses an ED array light source to perform optical writing on an image surface of a photoconductor or the like, an imaging optical system including a microlens array corresponding to a cycle of each LED array chip is arranged, and An LED array head characterized in that each microlens is composed of an imaging lens composed of a single lens including an aspherical surface in which aberrations such as field curvature are well corrected. 2. The LED array head according to claim 1, wherein when a dot (light emitting source) position of each LED array chip and a writing position on the image plane are reversed at a chip cycle.
An LED characterized by reversing the connection beforehand during wire bonding to the electrode pattern of the array chip
Array head. 3. The LED array head according to claim 1, wherein when the dot (light emitting source) position of each LED array chip and the writing position on the image plane are reversed at a chip cycle, write data is previously stored in a memory. The LED array head is characterized by being inverted by. 4. The LED array head according to claim 1, wherein the emission directions of the respective light emitting sources of the respective LED array chips are focused near the center of the microlens.
An LED array head, characterized in that the electrode pattern of the LED array chip is inclined. 5. The LED array head according to claim 1, wherein the emission directions of the respective light emitting sources of the respective LED array chips are focused near the centers of the microlenses.
An LED array head, wherein the emitting end surface of the LED array chip has a convex surface in the dot arrangement direction. 6. The LED array head according to claim 1, wherein a light shielding plate is provided between each LED array chip to reduce crosstalk of light flux between the chips. 7. The LED array head according to claim 1, wherein the optical power arrangement is such that the lateral magnification of the microlens is 1 or more. 8. An L (light emitting diode) array chip having a plurality of light emitting sources arranged in an array.
It consists of an ED array light source and a microlens array,
In an LED array head that performs optical writing on the image surface of a photoconductor or the like, the LED light emitting elements on the LED array chip are divided into groups so as to match the cycle of arrangement of the microlenses, and each microlens has an image surface. An LED array head comprising an imaging lens composed of a single lens including an aspherical surface in which aberrations such as curvature are well corrected. 9. The LED array head according to claim 8, wherein the grouped LEs are provided on each LED array chip.
When the dot (light emitting source) position of the D light emitting element group and the writing position on the image plane are reversed at the microlens cycle, at the time of wire bonding to the electrode pattern of the LED light emitting element group divided into groups on the LED array chip. An LED array head characterized in that the connection is reversed in advance. 10. The LED array head according to claim 8, wherein the grouped L's are provided on each LED array chip.
An LED array head characterized in that, when a dot (light emitting source) position of an ED light emitting element group and a writing position on an image plane are inverted at a microlens cycle, write data is inverted in advance in a memory. 11. The LED array head according to claim 8, wherein the grouped Ls are provided on each LED array chip.
The electrode patterns of the LED light emitting element groups divided into groups on the LED array chip are tilted so that the emission directions of the light emitting sources of the ED light emitting element group are focused near the center of the microlens. LED array head. 12. The LED array head according to claim 8, wherein the grouped Ls are provided on each LED array chip.
An LED array head, characterized in that a light shielding plate is provided between ED light emitting element groups to reduce crosstalk of luminous flux between the grouped LED light emitting element groups on the LED array chip. 13. The LED array head according to claim 8, wherein the optical power arrangement is such that the lateral magnification of the microlens is 1 or more.