JP2001277590A - Method for correcting light amount of optical printer head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for correcting a light amount of an optical printer head capable of accurately expressing a gradation by satisfactorily regulating a contrast of an image even if an expression of the gradation of a high accuracy is needed like a photographic image. SOLUTION: An optical printer head has a light emitting element array chip having many light emitting elements linearly arranged and many terminal electrodes electrically connected to the elements mounted on a circuit board covered with many circuit wirings in such a manner that the wirings are connected to the electrodes via bonding wires. The method for correcting the light amount of the optical printer head comprises the steps of emitting the light emitting elements 4 at least at respective ones before forming a latent image on a photosensitive member by using the optical printer head when the latent image is formed on the member, measuring a light amount of the lights emitted from the elements 4 by including a light amount of the lights reflected on the bonding wires 6 disposed near the elements 4, and regulating a magnitude of a power to be applied to the respective elements 4 in response to the light amount obtained by the measurement.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light amount correcting method for an optical printer head used as an exposure means for an electrophotographic printer, a facsimile, a copying machine or the like.

[0002]

2. Description of the Related Art Conventionally, optical printer heads such as LED array heads have been used as exposure means for electrophotographic printers and the like.

In such an LED array head, a plurality of LED array chips in which, for example, 128 light emitting diode elements are linearly arranged are mounted in a row on a circuit board on which a large number of circuit wirings are attached. And a structure in which a rod lens array is disposed on these LED array chips, and the light emitting diode elements of the LED array chips are selectively and individually lit based on image data, and the illuminated light is emitted. The light functions as an exposure unit by irradiating and forming an image on an external photoconductor through the lens array and forming a predetermined latent image on the photoconductor.

Then, the latent image formed on the photoreceptor becomes a toner image through a developing process, and a predetermined image is formed on the recording paper by transferring and fixing the toner image on the recording paper.

Incidentally, the LED array chip is manufactured by a conventionally known semiconductor manufacturing technique, and the LED array chip obtained in this way has a predetermined light emission variation.

Therefore, in order to make the intensity of light irradiated on the photoreceptor uniform, it is necessary to perform light quantity correction at the time of use.
As a specific method, it has been common practice to measure the amount of light of the light emitting diode elements in advance and adjust the power applied to each light emitting diode element based on the measured value.

[0007]

By the way, in the above-mentioned conventional optical printer head, during the printing operation, not only the direct light from the light emitting diode element but also the reflected light from the bonding wire is usually applied to the photosensitive member. Irradiation is performed, and the amount of light is affected by the position and shape of the bonding wire, and has a different size for each dot.

However, in the above-described conventional light amount correction method, only the light amount directly from the light emitting diode element is measured, and the magnitude of the power applied to each light emitting diode element is adjusted based on the measured value. The effect of the reflected light on the image density is not considered at all. Therefore, when accuracy is required for gradation expression as in a photographic image, the above-described light amount correction cannot perform sufficient correction, and fine adjustment of contrast becomes difficult, and the image becomes unclear. I was

[0009]

SUMMARY OF THE INVENTION The present invention has been devised in view of the above-mentioned drawbacks, and a light amount correcting method for an optical printer head according to the present invention is described on a circuit board on which a large number of circuit wirings are attached. A light emitting element array chip having a large number of light emitting elements arranged linearly and a large number of terminal electrodes electrically connected to the light emitting elements is mounted, and the circuit wiring and the terminal electrodes are connected via bonding wires. Using a connected optical printer head, when irradiating light emitted from the light emitting elements to a photoreceptor to form a latent image, the amount of light is corrected by adjusting the amount of power applied to each light emitting element. A light amount correction method for an optical printer head, wherein at least one of the light emitting elements emits light, and the light amount is reflected by a bonding wire located closest to the light emitting element. With measured included, is characterized in that for adjusting the magnitude of power applied to each light emitting element in accordance with the amount obtained by the measurement.

Further, according to the light amount correcting method for an optical printer head of the present invention, the intensity distribution obtained by the light amount measurement includes:
It is characterized in that a peak corresponding to the light emitting element side edge of the bonding wire exists.

Further, in the light amount correcting method for an optical printer head according to the present invention, a lens is disposed on a light emitting element array chip of the optical printer head, and the light amount measurement is performed at a high position corresponding to an image forming position of the lens. It is characterized by being performed in the above.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a perspective view showing the configuration of an optical printer head (LED array head) to which the light amount correction method according to one embodiment of the present invention is applied, and FIG. 2 is a side view of the LED array head of FIG.

The LED array head shown in FIG. 1 has a plurality of LED array chips (light emitting element array chips) 3 arranged in a line on an upper surface of a circuit board 1 on which a large number of circuit wirings 2 are attached. A plurality of driver ICs 7 are mounted and mounted, respectively, and a rod lens array 8 is arranged at a predetermined position on the LED array chip 3.

The circuit board 1 is formed by attaching and forming a large number of circuit wirings 2 in a predetermined pattern on the upper surface of an insulating substrate 1a made of an electrically insulating material such as a glass cloth base epoxy resin, glass, or alumina ceramics. The upper surface functions as a supporting base material for supporting a large number of circuit wirings 2, a plurality of LED array chips 3, a driver IC 7, and the like.

The plurality of LED array chips 3 mounted on the circuit board 1 are mounted and mounted in a line along the longitudinal direction of the circuit board 1, and each of the LED array chips 3 has, for example, 600 dpi on its upper surface. 12 arranged linearly with dot density
Eight light emitting diode elements (light emitting elements) 4 and a large number of terminal electrodes 5 electrically connected to the elements 4 are provided.

As the light-emitting diode element 4 of the LED array chip 3, a GaAlAs-based or GaAsP-based light-emitting diode element is preferably used, and the terminal electrode 5 of the chip 3 is formed on the circuit board 1 by a conventionally known wire bonding method. It is electrically connected to the corresponding circuit wiring 2.

The power supply power is applied to the light emitting diode element 4 through the circuit wiring 2, the bonding wire 6, the terminal electrode 5 and the like so that the light emitting diode element 4 emits light with a predetermined luminance. It has become.

The LED array chip 3 is manufactured by employing a conventionally known semiconductor manufacturing technique, and the LED array chip 3 obtained by such a manufacturing method is used.
Usually has a predetermined light emission variation. Therefore, when the optical printer head is used, highly accurate light amount correction using light amount correction data, which will be described later, is indispensable in order to make the light amount irradiated to the photoconductor uniform.

On the other hand, a driver IC 7 mounted on the circuit board 1 is for individually controlling the light emission of the light emitting diode elements 4 based on image data from the outside. Is provided with a shift register and a latch for light amount correction data, in addition to a shift register and a latch for image data. The light emitting diode element 4 is energized based on two types of data stored in the two latches. Is controlled.

In this embodiment, when performing light quantity correction,
A plurality of constant current power supplies having different current values are prepared, and one or more of these constant current power supplies are selected based on the light amount correction data stored in the latch to correspond to the light emitting diode. By connecting to the element 4, the power applied to the light emitting diode element 4 is adjusted.

The driver IC 7 is, like the LED array chip 3 described above, provided with the corresponding circuit wiring 2 on the upper surface of the circuit board by a conventionally known wire bonding method.
Is electrically connected to

The rod lens array 8 on the LED array chip 2 is for irradiating the light emitted from the light emitting diode element 4 onto an external photosensitive member P and forming an image. The rod lens array 8 has a linear shape. And a plurality of bar-shaped lenses arranged in a staggered pattern in two rows, and is held and fixed at a predetermined position by a lens holder (not shown).

Thus, the above-described LED array head has:
The light emitting diode elements 4 of the LED array chip 3 are selectively and individually illuminated based on image data and light amount correction data from the outside, and the emitted light is transmitted to an external photoconductor P via a rod lens array 8. Irradiation and imaging
By forming a predetermined latent image on the photoconductor P, it functions as an exposure unit.

The latent image formed on the photoreceptor P then undergoes a developing process to become a toner image, and the toner image is transferred and fixed on the recording paper to form a predetermined image on the recording paper. Becomes

Next, a method of creating light amount correction data used for correcting the light amount of the LED array head will be described.

First, the light emitting diode elements 4 are sequentially emitted one by one, and the light quantity is measured for each light emitting diode element.

As shown in FIG. 3, this light quantity measurement is performed using a measuring device equipped with a CCD camera which moves a height corresponding to the image forming position of the rod lens array 8 in parallel with the arrangement of the LED array chips 3. By subjecting the CCD image read by the CCD camera to image processing, a light amount distribution as shown in FIG. 4 can be obtained.

FIG. 4A shows that the light of the light emitting diode element is C.
FIG. 4B is a diagram showing an image obtained by observing with a CD camera. FIG. 4B is a diagram showing a light intensity distribution corresponding to the image shown in FIG. 4A.
(A) The area indicated by oblique lines, specifically, the area corresponding to the position of the light emitting diode element 4 and the bonding wire 6
It can be seen that light is detected in the region corresponding to the position.

What is important here is to measure the above-mentioned light amount including the light amount of the light b ₂ reflected by the bonding wire 6 existing near the light emitting diode element 4.

That is, when the light emitting diode element 4 is turned on, as shown in FIG. 4A, in addition to the light b ₁ directly emitted from the light emitting diode element 4,
Are adapted to reflected light b ₂ with a 5% to 15% of the strength of the intensity of the light b ₁ is irradiated, required gradation accurate as in the case of forming a photographic image when it is not only the direct light b ₁ from the light emitting diode element 4, it is important to influence by the reflected light b ₂ described above with due consideration to create a light quantity correction data.

Therefore, in this embodiment, the light emitting diode element 4
For example, when the size of the light-emitting diode element 4 is 30 μm in length × 20 μm in width, the center of the light-emitting diode element 4 is centered so that the amount of both the direct light b ₁ and the reflected light b _{2 from} The measurement range is set so as to cover a wide area within a radius of 250 μm.

As described above, by measuring the light amount over a wide area around the light emitting diode element 4, the reflected light b ₂ corresponding to the edge portion of the bonding wire 6 on the light emitting diode element 4 side in the obtained intensity distribution. look like the peak of the reflected light b ₂ to the corresponding to the rising portion of the loop shape of the peak and the bonding wire 6 is clearly confirmed, it is possible to perform the light amount measurement of the reflected light b ₂ reliably.

Next, by integrating the intensities of the light detected in the measurement area based on the intensity distribution obtained by the above-described measurement, the direct light b ₁ and the reflected light b ₂ from the light emitting diode element 4 are integrated. The total light quantity (b ₁ + b ₂ ) obtained by summing the light quantity and the light quantity is obtained for each dot, and then, the light quantity (b ₁ +
b ₂ ) and a predetermined power value required to fill the difference between the reference value and the reference value (average value) are calculated, and light amount correction data corresponding to this power value is created.

For example, the adjustment of the applied power should be 1% in 3% steps.
In the case of performing in six steps, light quantity correction data is created with 4 bits per dot, the obtained light quantity correction data is stored in a recording medium such as an EEP ROM, and is stored in a device body such as an electrophotographic printer together with an LED array head. Be incorporated.

When the LED array head is used, the light amount correction data is read from the above-mentioned recording medium, transferred and stored in a latch in the driver IC 7, and used for light amount correction.

At this time, as described above, the light quantity correction data is created in consideration of not only the light emission variation of the individual light emitting diode elements 4 but also the influence of the reflected light from the bonding wire 6, so that the light quantity correction data is generated during the printing operation. In addition, the amount of light applied to the photoconductor P is made uniform for each dot, and even when a high-precision gradation expression is required as in a photographic image, the contrast of the image is adjusted well. The gradation can be accurately expressed, and thereby a clear image with less density unevenness can be formed.

It should be noted that the present invention is not limited to the above-described embodiment, and various modifications and improvements can be made without departing from the gist of the present invention.

For example, in the above-described embodiment, when measuring the amount of emitted light, the light emitting diode elements are sequentially emitted one by one. Instead, the light emitting diode elements are set to a level at which reflected light does not interfere with each other. In this case, a plurality of light-emitting elements may be simultaneously emitted, and the light amounts corresponding to these light-emitting diode elements may be measured simultaneously.

In the above embodiment, the rod lens array 8
The light transmitted through the LED array chip 3 is measured and used to generate light quantity correction data. Instead of this, the light from the LED array chip 3 is directly measured without passing through the rod lens array 8 to obtain the light quantity correction data. It may be used for creation.

Further, in the above embodiment, the light quantity was measured using a CCD camera. Alternatively, the light quantity may be measured using an optical sensor such as a photodiode or a photomultiplier tube.

Further, in the above embodiment, the light amount is corrected by adjusting the magnitude of the current flowing through the light emitting diode element 4. However, instead of this, the energizing time to the light emitting diode element is adjusted. The light quantity may be corrected.

[0042]

According to the present invention, since the light quantity correction data is created in consideration of not only the variation in the light emission of the individual light emitting elements but also the influence of the light reflected by the bonding wire, the photoreceptor can be used during the printing operation. The amount of light applied to the image is made uniform, and even when a high-precision gradation expression is required as in a photographic image, the contrast of the image is satisfactorily adjusted to accurately express the gradation. This makes it possible to form a clear image with less density unevenness.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a configuration of an LED array head to which a light amount correction method according to one embodiment of the present invention is applied.

FIG. 2 is a side view of the LED array head of FIG.

FIG. 3 is a diagram showing a configuration of a measuring device used for measuring the amount of light.

FIG. 4A is a diagram showing an image obtained by observing light from a light emitting diode element with a CCD camera;
FIG. 3B is a diagram illustrating a light intensity distribution corresponding to the image illustrated in FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Circuit board, 2 ... Circuit wiring, 3 ... LED
Array chip (light emitting element array chip), 4 ... light emitting element (light emitting diode element), 5 ... terminal electrode, 6.
..Bonding wires 7 Driver ICs 8
... Rod lens arrays

Claims (3)

[Claims] 1. A light emitting element array chip having a large number of light emitting elements linearly arranged on a circuit board on which a large number of circuit wirings are attached, and a large number of terminal electrodes electrically connected to the light emitting elements. While placing, using a light printer head formed by connecting the circuit wiring and the terminal electrode via a bonding wire, when irradiating the photoconductor with light emitted from the light emitting element, to form a latent image, A light amount correction method for an optical printer head that corrects a light amount by adjusting a magnitude of electric power applied to each light emitting element, wherein the light emitting element emits at least one light emitting element at a time, and the light amount is most reduced from the light emitting element. While measuring including the amount of light reflected by the bonding wire located near,
A light amount correction method for an optical printer head, comprising: adjusting a magnitude of electric power applied to each light emitting element according to a light amount obtained by the measurement. 2. The method according to claim 1, wherein a peak corresponding to the light emitting element side edge of the bonding wire exists in the intensity distribution obtained by the light quantity measurement. 3. A lens is disposed on a light emitting element array chip of the optical printer head, and the light quantity measurement is performed at a height corresponding to an image forming position of the lens. 2. The light amount correction method for an optical printer head according to item 1.