JP2966705B2 - Image reading / writing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading / writing apparatus used for a facsimile or the like and having an electrophotographic printing function and a document reading function.

[0002]

2. Description of the Related Art Conventionally, in an electrophotographic printing apparatus, a photosensitive drum having a charged surface is exposed by an exposure device to form an electrostatic latent image on the photosensitive drum. Is developed into a toner image by a developing device, and the toner image is transferred to a transfer material and fixed.

Incidentally, the above-mentioned exposure apparatus uses a fluorescent lamp, a cold cathode tube or the like as a light source. In addition to an apparatus that forms optical information by using a liquid crystal element, there is an apparatus that forms optical information by using a laser or an LED element. In the case of an LED printer, an LED array head having the LED elements arranged in a line direction as a light source of an exposure device is provided. FIG. 2 is a schematic view of a conventional LED printer.

In FIG. 1, reference numeral 11 denotes a photosensitive drum, 12 denotes a charger for charging the surface of the photosensitive drum 11, and 13 denotes a light source as a light source of an exposure device for exposing the photosensitive drum 11 to form an electrostatic latent image. LED array head, 13a is the LE
A converging lens array 14 for forming light of each LED element (not shown) of the D array head 13 on the surface of the photosensitive drum 11; and a developing device 14 for developing an electrostatic latent image on the photosensitive drum 11 to form a toner image , 15 is a transfer device for transferring the toner image to the paper 16, 17 is a fixing device for fixing the toner image transferred to the paper 16, 18 is a cleaning device for removing the toner remaining on the photosensitive drum 11, and 19 is a photosensitive device A discharge lamp for removing the electric charge remaining on the body drum 11, a paper cassette 23, and a paper stacker 24.

When the LED elements of the LED array head 13 selectively actuate and emit light, an electrostatic latent image is formed on the photosensitive drum 11 uniformly and uniformly charged by the charger 12, and the electrostatic latent image is formed. The toner adheres to the photoconductor drum 11 from the developing device 14 in accordance with the latent image. On the other hand, the paper 16 fed from the paper cassette 23 is
And the transfer device 15. At this time, the photosensitive drum 1
The toner adhering to 1 is transferred to a sheet 16 by a transfer unit 15 and then fixed by a fixing unit 17 and stored in a sheet stacker 24.

In the photosensitive drum 11, the cleaning device 18 removes the toner remaining on the photosensitive drum 11, and the charge removing lamp 19 removes the remaining charge, and prepares for each process after the next charging process. . Further, in order to prevent the image quality from deteriorating when the roundness of the photosensitive drum is low, the optical axis of the converging fiber array is provided to intersect with the rotation axis of the photosensitive drum. (See JP-A-56-30154).

By the way, in a facsimile or the like,
An image reading / writing device having an electrophotographic printing function and a document reading function is used, and an LED array head is used as a sensor for image reading (Japanese Patent Laid-Open No. 58-157).
252). Next, the image reading / writing device will be described. FIG. 3 is a schematic diagram of a conventional image reading / writing device. In this case, only the operation at the time of reading an image will be described.

In the figure, 20 is an LED array head,
Reference numeral 21 denotes a photosensitive drum, reference numeral 22 denotes a plurality of LED elements (not shown), a plurality of LED arrays arranged in a line direction, reference numeral 31 denotes a document which is run on the photosensitive drum 21, and reference numeral 32 denotes a document reflected by the document 31. A converging lens array for imaging the reflected light on the surface of the LED array 22, a wiring board 33 for supporting the LED array 22,
Reference numeral 35 denotes a document illumination light source for irradiating the document 31, and reference numeral 36 denotes a light shielding (shielding) light emitted by the document illumination light source 35.
And a light-shielding plate 37 for preventing the LED array 22 from being irradiated.
And a control IC for controlling the LED array 22.

Each of the LED arrays 22 and the control ICs 37 is mounted on the wiring board 33, for example, n (n is an integer), for example, 40 LEDs.
7 is electrically connected by a gold wire or the like. Also,
The light emitted by the document illumination light source 35 has a center wavelength of about 5
The light emitted from each LED element of the LED array 22 is near-infrared light having an emission wavelength of about 700 [nm] in order to match sensitivity with the photosensitive drum 21. Consists of

[0010] In the image reading / writing apparatus having the above configuration,
The light emitted by the document illumination light source 35 illuminates the document 31,
The light is reflected by the original 31 and becomes reflected light. And
The reflected light is sent to the focusing lens array 32, is focused by the focusing lens array 32, and is imaged on the surface of the LED array 22. Here, the LED array 22 is formed of a PN junction element. When a reverse bias is applied to the PN junction element and light is applied to the junction surface, electrons are excited by the light, and P
A current proportional to the light intensity flows through the N-junction element. This current is detected by the control IC 37, and the image on the document 31 can be read.

[0011]

However, in the conventional image reading / writing apparatus, when reading an image, the depth of focus is MTF (Modulation Transf).
er Function) is reduced, and the resolution is reduced. Here, the focusing lens array 32 will be described.

As the focusing lens array 32, a selfoc lens array SLA (trade name: Nippon Sheet Glass Co., Ltd.)
Manufactured). The focusing lens array 32 is an optical system in which a number of gradient index lenses (not shown) are arranged to form an erect real-size real image. Next, the depth of focus MTF characteristic will be described with reference to FIGS. 4 to 6 (Nippon Sheet Glass Catalog SLA Vol 4, 1989.
7).

FIG. 4 is a first characteristic diagram of the focusing lens array,
FIG. 5 is a second characteristic diagram of the focusing lens array, and FIG. 6 is a third characteristic diagram of the focusing lens array. 4A to 6A show the relative positions of the LED array 22 (FIG. 3), the focusing lens array 32, and the photosensitive drum 21, and FIG. 4B shows the focusing lens having a conjugate length of 16.9 mm. The relationship between each deviation Δl and the depth of focus MTF when using the array 32 is
(C) shows the relationship between each deviation Δl and the depth of focus MTF when the focusing lens array 32 having a conjugate length of 18.0 [mm] is used. 4 (b) and (c) of FIGS. 4 to 6 show the case where the number of write lines or read lines within 1 [mm] (hereinafter referred to as “line density”) is changed. For example, if the line density is 2
[Lp / mm] means that two lines are printed within 1 [mm].

In FIG. 1, reference numeral 28 denotes a surface of the LED array 22, which becomes a light emitting surface when writing an image and becomes a light receiving surface when reading an image. 29 is the center of the conjugate length of the focusing lens array 32, 30 is the original surface of the original 31, and TC is the conjugate length. In FIG. 4, the surface 28 as the light receiving surface is shifted in the positive and negative directions by the deviation Δl,
That is, the center of the focusing lens array 32 does not deviate. The depth of focus MTF decreases as the deviation Δl increases.

FIG. 4 shows a case where the surface 28 is shifted in the positive and negative directions by a deviation Δl.
The same applies to the case where the document surface 30 is shifted in the positive and negative directions by the deviation Δl.

In FIG. 5, the conjugate length TC is as designed, but the conjugate length center 29 is shifted in the positive and negative directions by a deviation Δl ′. In FIG. 6, the conjugate length TC is TC ′.
Changes to FIG. 7 is an arrangement diagram of a converging lens array in a conventional image reading / writing device.

In FIG. 1, reference numeral 21 denotes a photosensitive drum, 22 denotes an LED array, 28 denotes a surface of the LED array 22, and 29 denotes a conjugate center of the focusing lens array 32. Also, TC
Is the conjugate length. The LED array 22, the focusing lens array 32, and the photosensitive drum 21 are fixed at positions where the light of the LED elements (not shown) of the LED array 22 correctly irradiates the photosensitive drum 21 when writing an image. The conjugate length TC corresponding to the emission wavelength of the light emitted by the 22 LED elements is set.

On the other hand, when reading an image, the original traveling path m on the photosensitive drum 21 is moved along the original 31.
(FIG. 3) is caused to travel, so that the distance between the surface 28 of the LED array 22 and the document surface 30 is shorter than the conjugate length TC by a distance Δm. In this case, it is equivalent to the deviation Δl being shifted to the negative side in FIG. Therefore,
Focusing lens array 32 having a conjugate length TC of 16.9 [mm]
With a line density of 4 [lp / mm] and a thickness of 0.
When a 1 mm test chart is read, the depth of focus M
The TF is 8% lower than when the distance Δm (= Δl) is 0.

Further, since the wavelength differs between the time of writing the image and the time of reading the image, the conjugate length TC changes accordingly, and the depth of focus MTF decreases. FIG. 8 is a diagram showing the relationship between the wavelength and the conjugate length. In the figure, the horizontal axis represents the wavelength λ, and the vertical axis represents the conjugate length TC. As shown in the figure, when the wavelength λ changes, the conjugate length TC
Also change.

For example, a focusing lens array 32 (FIG. 3) having a conjugate length TC of 16.9 [mm] and an emission wavelength of 740 [n]
m] and the center wavelength is 550 [n
m], the conjugate length TC becomes 18.6 [mm] at the time of writing an image, and 18.5 [mm] at the time of reading an image, even though the conjugate length TC is 16.5 [mm]. The light is received at 6 [mm], which is equivalent to the change of the conjugate length TC to TC 'in FIG. 6, and the depth of focus MTF is reduced.

The present invention solves the problems of the conventional image reading / writing apparatus, and the depth of focus does not change between the time of writing an image and the time of reading the image. It is an object of the present invention to provide an image reading / writing device which does not have any problem.

[0022]

For this purpose, in the image reading / writing apparatus according to the present invention, a photosensitive drum, an LED array arranged opposite to the photosensitive drum, and the photosensitive drum are provided. It has a converging lens array disposed between the LED arrays, and a document illumination light source for irradiating the document with light when reading an image.

The LED array is used as a light source of an exposure device when writing an image, and is used as a document reading sensor when reading an image. The converging lens array converges light emitted by the LED elements of the LED array when writing an image, and converges reflected light on a document when reading an image. The LED array and the focusing lens array are set at a first position corresponding to the emission wavelength of the LED array when writing an image, and at a second position corresponding to the wavelength of a document illumination light source when reading an image. For this purpose, a position setting means is provided.

[0024]

According to the present invention, as described above, in the image reading / writing device, the photosensitive drum, the LED array disposed opposite to the photosensitive drum, the photosensitive drum and the LED array A focusing lens array disposed between
A document illumination light source for irradiating the document with light when reading an image;

The LED array is used as a light source of an exposure device when writing an image, and is used as a document reading sensor when reading an image. The converging lens array converges light emitted by the LED elements of the LED array when writing an image, and converges reflected light on a document when reading an image. Therefore, at the time of writing an image, the light emitted by the LED elements of the LED array is sent to the converging lens array, focused on the converging lens array, and imaged on the surface of the photosensitive drum.

When reading an image, the original is illuminated by an original illuminating light source, and the reflected light is sent to a converging lens array, which converges and forms an image on the surface of the LED array. The LED array and the focusing lens array are set at a first position corresponding to the emission wavelength of the LED array when writing an image, and at a second position corresponding to the wavelength of a document illumination light source when reading an image. For this purpose, a position setting means is provided.

When the original is moved on or above the photosensitive drum, the distance between the converging lens array and the photosensitive drum and the distance between the converging lens array and the original surface cannot be equalized. Deviation occurs. Also, since the wavelength of the original illumination light source at the time of reading an image is different from the emission wavelength of the LED element of the LED array at the time of writing an image, a deviation occurs in the conjugate length.

The position setting means sets the LED array and the focusing lens array to a first position corresponding to the emission wavelength of the LED array at the time of writing an image in accordance with the deviation, and sets an original illumination light source at the time of reading the image. At the second position corresponding to the wavelength of.

[0029]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a state diagram at the time of writing in an image reading / writing device showing an embodiment of the present invention, and FIG. 9 is a state diagram at the time of reading in an image reading / writing device showing an embodiment of the present invention.

In the drawing, reference numeral 21 denotes a photosensitive drum, 31 denotes a document which is moved on or above the photosensitive drum 21, 32 denotes a converging lens array, and 35 denotes a document illuminating light source which irradiates the document 31 , 51 are LED units disposed so as to face the photosensitive drum 21 via the converging lens array 32, and 52 are a number of L (not shown).
LED that consists of ED elements and is arranged in the line direction
An LED array constituting the array head, 53 is the LED
A wiring board supporting the array 52, a light shielding plate 56 for shielding the light of the document illumination light source 35 so as not to irradiate the LED array 52, and a lens holder 57 for the focusing lens array 32.

A plurality of control ICs (not shown) are supported on the wiring board 53 in parallel with the LED array 52. The LED array 52 and the control ICs are both n (n is an integer), for example, 40 are mounted on the wiring board 53, and each LED array 52 is electrically connected to each control IC by a gold wire or the like. . The LED unit 51 and the converging lens array 32 are both supported by a positioning frame 61 so that their positions can be changed between when writing an image and when reading an image, and are linearly moved by a cam device or the like. Can be

The positioning frame 61 is
A first position setting protrusion 62 and a second position setting protrusion 63 for positioning the ED array 52, and a first position setting protrusion 64 and a second position setting protrusion for positioning the focusing lens array 32. 65. Therefore, the LE
By raising the D array 52 (moving in a direction away from the photosensitive drum 21) and bringing the LED unit 51 into contact with the first position setting protrusion 62, the LED array 52 is set to the L level.
The LED unit 52 is set at an upper position corresponding to the emission wavelength of the ED array 52, and the LED array 52 is lowered (moved in a direction approaching the photosensitive drum 21) to bring the LED unit 51 into contact with the second position setting protrusion 63. LED array 5
2 can be set at a lower position corresponding to the center wavelength of the focusing lens array 32. Further, by raising the focusing lens array 32 and bringing the lens holder 57 into contact with the first position setting projection 64, the focusing lens array 3
2 is set to an upper position corresponding to the emission wavelength of the LED array 52, and the focusing lens array 32 is lowered to bring the lens holder 57 into contact with the second position setting projection 65, thereby focusing the focusing lens array 32. It can be set at a lower position corresponding to the center wavelength of the lens array 32.

In this case, as shown in the figure, when writing an image, the LED array 52 and the focusing lens array 3 are used.
2 are set to the upper position, and when reading an image,
The LED array 52 and the focusing lens array 32 are both set at the lower position. The upper and lower positions of the LED array 52 and the focusing lens array 32 are determined by the conjugate length TC of the focusing lens array 32 to be used and the original illumination light source 35.
, The emission wavelength of the LED array 52, and the like. Here, the center wavelength is a wavelength that shows a peak in the emission spectrum of the document illumination light source 35.

For example, the conjugate length TC is 16.9 [mm],
When the converging lens array 32 having an aperture angle of 20 °, the document illumination light source 35 having a center wavelength of 550 nm, and the LED array 52 having an emission wavelength of an LED element of 740 nm are used when writing an image. The LED array 52
The conjugate length TC corresponding to the emission wavelength of
[Mm]. Further, the conjugate length T corresponding to the center wavelength of the document illumination light source 35 at the time of reading an image
FIG. 8 shows that C is 16.5 [mm].

Therefore, when writing an image, LE
The light emitting surface of the D array 52 is 18.6 from the photosensitive drum 21.
The upper position of the LED array 52 is set so as to be the position of [mm], and the upper position of the converging lens array 32 is set so that the midpoint thereof coincides with the conjugate center 29 of the converging lens array 32 (see FIG. 4). Set. On the other hand, the lower position of the LED array 52 is set so that the light receiving surface of the LED array 52 at the time of reading an image is 16.5 [mm] from the document surface m (see FIG. 7). The lower position of the focusing lens array 32 is set so that the conjugate length centers 29 of the lens array 32 coincide.

In the present embodiment, since the emission wavelength of the LED element is longer than the center wavelength of the original illumination light source 35, the first position is set upward and the second position is set lower. When the emission wavelength of the LED element is short, the first position is set downward and the second position is set upward. It should be noted that the present invention is not limited to the above embodiment, and various modifications can be made based on the gist of the present invention.
They are not excluded from the scope of the invention.

[0037]

As described in detail above, according to the present invention, in an image reading / writing apparatus, a photosensitive drum,
An LED array disposed opposite the photosensitive drum, a converging lens array disposed between the photosensitive drum and the LED array, and a document illumination light source for irradiating a document with light when reading an image. Have.

The LED array is used as a light source of an exposure device when writing an image, and is used as a document reading sensor when reading an image. The converging lens array converges light emitted by the LED elements of the LED array when writing an image, and converges reflected light on a document when reading an image. The LED array and the focusing lens array are set at a first position corresponding to the emission wavelength of the LED array when writing an image, and at a second position corresponding to the wavelength of a document illumination light source when reading an image. For this purpose, a position setting means is provided.

When the original is moved on or above the photosensitive drum, the distance between the converging lens array and the photosensitive drum and the distance between the converging lens array and the original surface cannot be equalized. Deviation, and
Since the wavelength of the document illumination light source at the time of writing an image and the emission wavelength of the LED element of the LED array at the time of reading an image are different, deviations occur in the conjugate length. It can be absorbed by changing it. Therefore,
The depth of focus does not change between the time of writing an image and the time of reading the image, and the resolution does not decrease due to the change in the depth of focus.

[Brief description of the drawings]

FIG. 1 is a state diagram at the time of writing in an image reading / writing apparatus according to an embodiment of the present invention.

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

FIG. 3 is a schematic diagram of a conventional image reading / writing device.

FIG. 4 is a first characteristic diagram of the focusing lens array.

FIG. 5 is a second characteristic diagram of the focusing lens array.

FIG. 6 is a third characteristic diagram of the focusing lens array.

FIG. 7 is a diagram showing an arrangement of a focusing lens array in a conventional image reading / writing apparatus.

FIG. 8 is a diagram illustrating the relationship between wavelength and conjugate length.

FIG. 9 is a state diagram at the time of reading in the image reading / writing apparatus according to the embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 21 photosensitive drum 52 LED array 31 document 32 focusing lens array 35 document illumination light source 62, 64 first position setting protrusion 63, 65 second position setting protrusion

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Hiroshi Furuya 1-7-12 Toranomon, Minato-ku, Tokyo Oki Electric Industry Co., Ltd. (56) References JP-A-61-39070 (JP, A) (58) ) Surveyed field (Int.Cl. ⁶ , DB name) H04N 1/04-1/207

Claims (1)

(57) [Claims] 1. An image forming apparatus comprising: (a) a photosensitive drum; and (b) disposed opposite to the photosensitive drum, used as a light source of an exposure device when writing an image, and used as a document reading sensor when reading an image. (C) disposed between the photosensitive drum and the LED array, for converging light emitted by the LED elements of the LED array at the time of writing an image, and for reflecting light reflected on the original at the time of reading the image. A focusing lens array for focusing; (d) a document illumination light source for irradiating the document with light when reading an image; and (e) the LED array and the focusing lens array correspond to the emission wavelength of the LED array when writing an image. First
An image reading / writing apparatus, wherein the image reading / writing apparatus has a position setting means for setting the position to a second position corresponding to the wavelength of the document illumination light source when reading the image.