JP2004259724A - Light emitting element / light receiving element array and optical write head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable an optical system which performs light quantity correction by monitoring luminous intensities of light emitting elements by means of light receiving elements to perform the light quantity correction with high accuracy. <P>SOLUTION: In a light emitting element/light receiving element array chip 30, light emitting elements (LED) 32 and light receiving elements (PD) 36 are integrated. Bonding pads 34 for light emitting elements are connected to the light emitting elements 32, and bonding pads 38 for light receiving elements are connected to the light receiving elements 36. Top surfaces of the light receiving element 36 are covered with wiring materials of the bonding pads 38. Therefore, no reflected light from a rod lens or a photosensitive drum is inputted to the light receiving elements 36. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a light emitting element / light receiving element array and an optical writing head, and more particularly to a light emitting element / light receiving element array in which the light intensity is corrected by monitoring the light emission intensity of the light emitting element, and such a light emitting element / light receiving element array. The present invention relates to an optical writing head used. The present invention further relates to a light amount correction method for an optical writing head.
[0002]
[Prior art]
In an optical writing head using an LED array as a light source and an image forming apparatus such as an electrophotographic printer using the same, an initial light-emitting intensity variation of a light source, a variation in light quantity with time, and a variation in light quantity caused by a variation in light quantity caused by a temperature change. There is a problem that variations in light emission intensity cause shading of a printed image, causing streaks in the printed image, and significantly lowering the image quality.
[0003]
As a solution to these problems, in the technique described in Patent Document 1, a light emitting element / light receiving element array is formed by two-dimensionally arranging a light emitting element and a light receiving element on the same substrate, and the reflection emitted from the light emitting element is reflected. Light is detected by the light receiving element, and the light receiving element monitors the change in the light emission intensity of the light emitting element, and corrects the change in the light emission intensity so as to have a predetermined exposure amount, stabilizes the light emission intensity, and achieves high quality. An optical head for electrophotography which forms an image is disclosed.
[0004]
In this specification, the light emission intensity and the exposure amount are used in the following sense. The luminous intensity represents the power at the moment when each luminous point emits light. The exposure amount is obtained by integrating the light emission intensity with the lighting time, and has an energy dimension. That is, the amount is proportional to the number of photons to be irradiated.
[0005]
[Patent Document 1]
JP 2002-144634 A
[Problems to be solved by the invention]
However, the optical head for electrophotography described in Patent Document 1 has the following problems.
[0007]
FIG. 1 shows an optical writing head including a light emitting element / light receiving element array. According to this optical writing head, the housing 12 provided with the rod lens array 10 and the heat sink 16 provided with the light emitting element / light receiving element array 14 are arranged such that the optical axis 18 of the rod lens array 10 It is arranged so as to coincide with the element array 14 and is fixed by the member 20.
[0008]
The light emitted from the light emitting element of the light emitting element / light receiving element array 14 is partially reflected on the incident surface of the rod lens array 10 and is incident on the light receiving element provided in the light emitting element / light receiving element array 14, or Light transmitted through the lens array 10 and specularly reflected by the photosensitive drum 22 re-enters the rod lens and reaches the light receiving element.
[0009]
However, the intensity of light reaching the light receiving element via such a path is affected by the surface condition of the reflection surface, and the intensity of light incident on the light receiving element varies.
[0010]
For example, the presence or absence of surface scratches on the photosensitive drum and the adhesion of toner on the exit surface of the rod lens change the light reflectance and transmittance. Due to these problems, there is a problem that an excessive change occurs more than a change in the light emission intensity due to the temperature-dependent change and the deterioration with time of the light emitting element, so that it is not possible to perform appropriate light amount correction.
[0011]
For example, as for the light emitted from the light emitting element, about 5 to 10% of the specularly reflected light on the entrance surface and the exit surface of the rod lens array returns to the light receiving element. If the light irradiated on the surface of the photosensitive drum has a regular reflectance of about 20% on the surface of the photosensitive drum, about 10% of the light reflected by the photosensitive drum returns to the light receiving element.
[0012]
The photosensitive drum contacts the cleaning blade and the toner in the operation process, so that fine scratches are generated on the surface and the reflected light is scattered. For this reason, the intensity of the light returning to the light receiving element fluctuates, and it is difficult to accurately detect the light emission intensity of the light emitting element.
[0013]
Although it is conceivable to provide a reflector 24 such as a mirror inside the optical writing head as shown in FIG. 2, the number of parts increases the size and cost of the optical writing head.
[0014]
In the light-emitting element / light-receiving element array, if the light-emitting element and the light-receiving element are made of the same band gap material, the sensitivity of the light-receiving element to the emission wavelength is reduced, and a large area light-receiving element is required. is there.
[0015]
This is because the light-emitting element emits light having an energy lower than the band gap, and light having an energy higher than the band gap is attenuated by self-reabsorption in the light-emitting layer, and light below the band gap is not absorbed. This is because the sensitivity is lowered.
[0016]
The present invention has been made in view of such conventional problems, and has as its object to monitor the light emission intensity of a light emitting element with a light receiving element and perform light quantity correction with high accuracy in an optical system for correcting light quantity. An object of the present invention is to make it feasible and to be able to carry out at low cost.
[0017]
[Means for Solving the Problems]
The light emitting element / light receiving element array of the present invention forms a light emitting element array and a light receiving element array composed of light receiving elements corresponding to the respective light emitting elements of the light emitting element array on the same substrate. Is characterized in that it is covered with a wiring material to prevent the reflected light from entering, and the emitted light of the light emitting element is directly incident on the corresponding light receiving element, so that the emission intensity of each light emitting element can be monitored.
[0018]
The light emitting element can be constituted by a light emitting diode formed by a diffusion method, and the light receiving element can be constituted by a photodiode formed by a diffusion method.
[0019]
Alternatively, the light emitting element array can be constituted by a self-scanning light emitting element array having a pnpn structure formed by epi growth, and the light receiving element can be constituted by a photodiode having a pn junction in the pnpn structure.
[0020]
The optical writing head of the present invention can be composed of the light emitting element / light receiving element array as described above and a rod lens array or a flat microlens array.
[0021]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 3 shows a light emitting element / light receiving element array chip 30 in which an LED (light emitting diode) and a PD (photodiode) are integrated on the same chip. A light emitting element bonding pad 34 is connected to the light emitting element (LED) 32, and a light receiving element bonding pad 38 is connected to the light receiving element (PD) 36. The upper surface of the light receiving element 36 is covered with a wiring material of the bonding pad 38. Therefore, the light reflected from the rod lens or the photosensitive drum does not enter the light receiving element 36.
[0022]
FIG. 4 is a cross-sectional view taken along line XX ′ of FIG. An insulating film 42 serving also as a diffusion mask and a protective film is provided on the surface of the n-type substrate 40, and p-type impurities are diffused from openings of the insulating film to form p-type regions 44 and 46. ing. The wirings 34 and 38 are in contact with this p-type region. In the figure, reference numeral 48 denotes a back electrode.
[0023]
When a current flows through the p-type region 44, light is emitted. A part of the emitted light propagates in the substrate 40 and reaches a pn junction at the boundary between the p-type region 46 and the n-type substrate 40. In this case, the light receiving element 36 may be used in a photodiode (PD) mode with a bias or in a solar cell mode. Thus, the emission intensity of the light emitting element can be detected by the corresponding light receiving element.
[0024]
Since the PD has a relatively small temperature coefficient, it is not significantly affected by temperature, but the temperature of the PD can be known by measuring the rising voltage of the diode by passing a small current through the PD. The sensitivity of the PD may be corrected based on this temperature. Further, in FIG. 3, the bonding pads 38 for the light receiving element are all independent, but all PDs may be connected to one bonding pad for use. Further, the light receiving element may be divided into several blocks, and each block may be connected to one bonding pad.
[0025]
FIG. 5 shows a second example of the configuration of the light emitting element / light receiving element. In FIG. 4, the pn junction is formed by diffusion, but here, a multi-layer film is formed on an n-type semiconductor substrate by epitaxial growth and separated by mesa etching. In the figure, 50 is an n-type epi layer formed on the n-type substrate 40, and 52 is a p-type semiconductor layer, which forms a light emitting element. 54 is an n-type semiconductor layer formed on the n-type substrate 40, and 56 is a p-type semiconductor layer, which forms a light receiving element. 58 is a protective insulating film. The same components as those in FIG. 4 are denoted by the same reference numerals as those in FIG.
[0026]
The above is an example using the LED as the light emitting element and the light receiving element PD. The light emitting element and the light receiving element are not limited to these, and a three-terminal light emitting thyristor having a pnpn structure can be used for the light emitting element.
[0027]
FIG. 6 is a plan view showing a light-emitting element / light-receiving element array in which a light-receiving element is formed in a self-scanning light-emitting element array using a three-terminal light-emitting thyristor as a light-emitting element. FIG. 7 is a diagram showing a cross section taken along line YY ′ of FIG. FIG. 8 shows an electrical equivalent circuit of the self-scanning light emitting element array shown in FIG.
[0028]
6, 60 is the light emitting thyristor _(L 1 in FIG. _{8, L 2, L 3,} ...), 62 a shift thyristor _(T 1 in FIG. _{8, T 2, T 3,} ...), the gate electrode 64 (G ₁ , G ₂ , G ₃ ,... In FIG. 8), 66 are coupling diodes (D ₁ , D ₂ , D ₃ ,... In FIG. 8), and 68 is a resistor (R _{L in} FIG. 8). .phi.1, .phi.2 clock pulse _{line, V GK} is a power supply line, the phi _I is a write signal line. 70 is a light receiving element corresponding to the light emitting thyristor, and 72 is a light receiving element line.
[0029]
In FIG. 7, the light-emitting thyristor and the shift thyristor have a pnpn structure. In the figure, reference numeral 80 denotes an n-type semiconductor substrate, 82 denotes an n-type semiconductor layer, 84 denotes a p-type semiconductor layer, 86 denotes an n-type semiconductor layer, 88 denotes a p-type semiconductor layer, and 90 denotes a protective insulating film. Note that the same components as those in FIG. 6 are denoted by the same reference numerals.
[0030]
As can be seen from FIG. 7, the light receiving element 70 uses a pn junction between the p-type semiconductor layer 84 and the n-type semiconductor layer 82 as a PD. Such a PD is separated from the light emitting element 60 by mesa etching.
[0031]
The configuration of the PD is not limited to this, and any pn junction in a pnpn structure can be used. For example, in FIG. 9, a pn junction between the n-type semiconductor layer 86 and the p-type semiconductor layer 84 is used for the PD. In a self-scanning light-emitting element array having a double hetero structure in order to increase luminous efficiency, the two layers 86 and 84 correspond to an active layer. Therefore, in order to receive light from the light-emitting element, this pn junction is used. Is suitable. In FIG. 9, reference numerals 74 and 75 denote light receiving element lines.
[0032]
In FIG. 10, a pn junction between the p-type semiconductor layer 88 and the n-type semiconductor layer 86 is used for the PD. Since they correspond to the anode layer and the gate layer of the self-scanning light-emitting element array, they can be manufactured in exactly the same steps as the self-scanning light-emitting element array. In FIG. 10, reference numerals 76 and 77 denote light receiving element lines.
[0033]
In FIG. 11, the light emitting element is an optical transistor using three layers of an n-type semiconductor layer 86, a p-type semiconductor layer 84, and an n-type semiconductor layer 82. Using the n-type semiconductor layer 86 as an emitter, a base-emitter current due to a photocurrent is converted into a collector current. Since this structure can be manufactured only by taking out the light receiving element line 78 from the n-type semiconductor layer 86, exactly the same process as the self-scanning light emitting element array can be used.
[0034]
In FIG. 12, the semiconductor layer 86, 84, 82 is insulated by ion implantation with hydrogen ions instead of the mesa etching between the light receiving element and the light emitting element, instead of the mesa etching between the light receiving element and the light emitting element. Separation was performed. The separation area is indicated by 89. This configuration is characterized in that there is no discontinuous change in the refractive index due to mesa etching between the light receiving element and the light emitting element, so that more light enters the light receiving element. Here, separation by ion implantation is performed for the configuration of FIG. 11, but it may be applied to any of FIGS. 5, 7, 9, and 10.
[0035]
A plurality of light emitting element / light receiving element array chips having the above-described structure are arranged in a linear or staggered manner to produce a light emitting element / light receiving element array for an optical writing head. A light amount correction method in the optical writing head having the configuration of FIG. 1 equipped with such a light emitting element / light receiving element array will be described.
[0036]
In light quantity correction, first, the light emission intensity distribution of the optical writing head is measured. FIG. 13 is a diagram showing an apparatus for measuring the light emission intensity distribution of the optical writing head. (A) is a side view of the apparatus, and (B) is a front view. A light amount sensor 106 is disposed on a rail 104 extending in the direction of arrangement of the rod lens array 102 of the optical writing head 100 at a position movably along the rail and opposed to an emission portion of the optical writing head. By causing the light emitting element array to emit light and moving the light quantity sensor 106 along the rail 104, the light emission intensity distribution is measured in dot units, and the light emission intensity in dot units of the light emitting element is adjusted so that the exposure amount of each dot becomes uniform. And / or adjust the lighting time. In this state, the light emission intensity or exposure amount of the light emitting element in units of dots or chips is measured by the light receiving element provided in the light emitting element / light receiving element array chip, and the value is stored in the non-volatile storage means in the driver circuit. Record it.
[0037]
The optical writing head 100 whose emission intensity distribution has been measured as described above is installed in an optical printer. FIG. 14 shows the configuration of the optical printer. A photoconductive material (photoconductor) such as amorphous Si is formed on the surface of the cylindrical photosensitive drum 112. This drum rotates at the speed of the print. The surface of the photoreceptor of the rotating drum is uniformly charged by the charger 114. Then, the light of the dot image to be printed is irradiated on the photoreceptor by the optical writing head 100 to neutralize the charge at the position where the light is applied, thereby forming a latent image. Subsequently, the developing unit 118 applies toner on the photoconductor in accordance with the charged state on the photoconductor. Then, the transfer device 120 transfers the toner onto the sheet 124 sent from the cassette 122. The sheet is fixed by applying heat or the like in a fixing device 126 and sent to a stacker 128. On the other hand, the drum on which the transfer has been completed is neutralized over the entire surface by the erase lamp 130, and the remaining toner is removed by the cleaner 132.
[0038]
When adjusting the light quantity change due to the temperature of the light emitting element of the optical writing head 100 and the light quantity change due to aging, the light emitting element is set in dot units or a plurality of dot units in a time gap such as between paper feeds during optical printer printing. The light is emitted, and the light emission intensity or exposure amount at that time is directly measured by the light receiving element, the value is compared with the value written in the non-volatile storage means, and the difference is corrected. The light amount of the light emitting element is adjusted so that the light amount of the light emitting element becomes uniform.
[0039]
At this time, the photosensitive drum 112 is irradiated with light to form a latent image, and the toner adheres to the photosensitive member in the developing process. However, as described above, the light emission timing is controlled at a timing corresponding to the gap portion of the paper feed. The toner adhered to the photoconductor is cleaned by the cleaning blade of the cleaning device 132 without adhering to the paper.
[0040]
In this case, it is necessary to intentionally set the pitch between the papers for paper feeding, and there is a possibility that the printing speed may be reduced. Therefore, it is preferable that the timing of the light amount correction is performed for each of a plurality of printed sheets.
[0041]
According to this embodiment, the light receiving element is manufactured at the same time as the light emitting element, so that the cost can be reduced as compared with the individual manufacturing.
[0042]
Further, according to the present embodiment, the light receiving element directly receives the light from the light emitting element, so that the light receiving element is not affected by the surface condition of the reflector unlike the related art. Therefore, since the light emission intensity or the exposure amount with high accuracy can be detected, the light amount correction with high accuracy can be performed even with lapse of time or a change in the operating condition, and a high-quality image free from streaks can be obtained.
[0043]
Hereinafter, another embodiment of the present invention will be described. In this embodiment, instead of the rod lens array, an optical resin lens with very little light quantity unevenness is used.
[0044]
In an optical writing head using a rod lens array, if the position of the light emitting element deviates from the center of the optical axis of the lens, a light intensity step occurs in the lens cycle. Therefore, in the case of such an optical writing head, in order to correct the light amount, as described with reference to FIG. 13, the light amount of the light emitting element is detected through the lens, and the light amount is made uniform. Therefore, large-scale equipment is required for adjustment.
[0045]
FIG. 15 schematically shows an optical writing head equipped with a flat microlens array to avoid this. (A) is a diagram of the flat microlens array 140 viewed from the side, and (B) is a plan view of the flat microlens array. The flat plate microlens array 140 emits light from the light emitting element / light receiving element array 14 configured by superposing a plurality of (two in this embodiment) resin lens arrays 144 having a large number of microlenses 142 formed on both surfaces. The light thus collected is focused on the photosensitive drum 22.
[0046]
Since the resin lens 140 having such a configuration can transmit light two-dimensionally, light amount transmission unevenness due to the lens pitch does not occur, so that it is not necessary to acquire light amount data via the lens. Therefore, since the light emitting intensity or the exposure amount of the light emitting element can be detected by the head alone, a large light amount detecting device is not required. That is, the light emitting element is caused to emit light in dot units or a plurality of dot units, the light emission intensity or the exposure amount at that time is measured by the light receiving element, and the value is written in the nonvolatile storage means. The light energy of the light emitting element that emits light at the timing of the paper feed gap during printing is measured by the light receiving element, collated with the value written in the nonvolatile storage means, the difference is corrected, and each dot or plural The light emission intensity and / or the lighting time of the light emitting element can be adjusted so that the exposure amount per dot becomes uniform.
[0047]
Another embodiment of the present invention will be described. In the embodiment shown in FIG. 6, a PD 70 corresponding to each light emitting element 60 is provided. However, in the configuration of FIG. 6, the chip width is increased by the amount of the PD, and the cost is accordingly increased. Further, in the configuration of FIG. 6, since the PD is provided between the side of the light emitting element and the long side of the chip, when the chips are arranged in a staggered manner, the interval between the light emitting elements increases.
[0048]
Therefore, in the case of the present embodiment, as shown in FIG. 16, one PD 70 is provided beside the first light emitting element 70 at the left end (position shifted in the light emitting element arrangement direction). The other structure is the same as that of FIG. 6, and therefore, the same components as those of FIG. 6 are denoted by the same reference numerals. FIG. 6 shows a bonding pad provided at the left end of the chip. Reference numeral 38 denotes a bonding pad for the PD 70.
[0049]
In such a configuration, the chip width is hardly changed, which is advantageous in cost. However, it is not possible to monitor the light emission intensity or the exposure amount for all the light emitting elements, and correction is performed using data on the first light emitting elements.
[0050]
【The invention's effect】
According to the present invention, since the light receiving element provided in the chip directly receives light from the light emitting element, it is not necessary to use reflected light. Therefore, since it is not affected by the change in the surface state of the light reflecting object such as the rod lens array, the light emitting intensity or the exposure amount of the light emitting element with high accuracy can be detected. By performing the light amount correction using the monitoring result of the light emission intensity or the exposure amount, the change in the light amount and the change in the light amount due to the deterioration with time of the light emitting element can be corrected, and a high-quality image can be guaranteed.
[Brief description of the drawings]
FIG. 1 is a diagram showing an optical writing head including a light emitting element / light receiving element array.
FIG. 2 is a diagram showing an optical writing head having a reflecting object such as a mirror inside.
FIG. 3 is a view showing a light emitting element / light receiving element array chip according to the present invention.
FIG. 4 is a sectional view taken along line XX ′ of FIG. 3;
FIG. 5 is a diagram showing another example of the configuration of the light emitting element / light receiving element.
FIG. 6 is a plan view showing a light emitting element / light receiving element array in which a light receiving element is formed on a self-scanning light emitting element array.
FIG. 7 is a view showing a cross section taken along line YY ′ of FIG. 6;
8 is a diagram showing an electrical equivalent circuit of the self-scanning light emitting element array shown in FIG.
FIG. 9 is a diagram showing another example of the configuration of the light emitting element / light receiving element.
FIG. 10 is a diagram showing another example of the configuration of the light emitting element / light receiving element.
FIG. 11 is a diagram showing another example of the configuration of the light emitting element / light receiving element.
FIG. 12 is a diagram showing another example of the configuration of the light emitting element / light receiving element.
FIG. 13 is a diagram showing an apparatus for measuring a light amount distribution of an optical writing head.
FIG. 14 is a diagram illustrating a configuration of an optical printer.
FIG. 15 is a diagram showing an optical writing head equipped with a flat microlens array.
FIG. 16 is a plan view showing a light emitting element / light receiving element array in which one light receiving element is formed on a self-scanning light emitting element array.
[Explanation of symbols]
10, 102 rod lens array 12 housing 14 light emitting element / light receiving element array 16 heat sink 22, 112 photosensitive drum 24 reflector 30 light emitting element / light receiving element array chip 32 light emitting element 34 light emitting element bonding pad 36, 70 light receiving element 38 light receiving element Bonding pad 40 n-type substrate 44, 46 p-type region 48 back electrode 50, 54, 82, 86 n-type semiconductor layer 52, 56, 84, 88 p-type semiconductor layer 58, 90 protective insulating film 60 light-emitting thyristor 62 shift Thyristor 64 Gate electrode 66 Coupling diode 68 Resistor 72 Light receiving element line 80 N-type semiconductor substrate 89 Separation region 100 Optical writing head 106 Light intensity sensor 114 Charger 118 Developing unit 120 Transfer unit 122 Cassette 124 Paper 128 Stacker 130 Erase lamp 132 Clean Vessel

Claims (14)

A light emitting element array composed of a plurality of light emitting elements and a light receiving element array composed of light receiving elements corresponding to each light emitting element of the light emitting element array are formed on the same substrate, and the upper surface of each light receiving element is made of a wiring material. A light-emitting element / light-receiving element array that covers and blocks the incidence of reflected light, and allows light emitted from the light-emitting element to directly enter the corresponding light-receiving element, thereby monitoring the light emission intensity of each light-emitting element. A light emitting element array composed of a plurality of light emitting elements and one light receiving element corresponding to one light emitting element at the end of the light emitting element array are formed on the same substrate, and the upper surface of the light receiving element is a wiring. A light emission that is covered with a material to prevent reflected light from entering, so that emitted light of the one light emitting element can be directly incident on the one light receiving element to monitor the light emission intensity of the one light emitting element. Element / light receiving element array. The light emitting element is configured by a light emitting diode formed by a diffusion method,
The light-emitting element / light-receiving element array according to claim 1, wherein the light-receiving element is configured by a photodiode formed by a diffusion method. The light emitting element array is composed of a self-scanning light emitting element array having a pnpn structure formed by epi growth,
The light-emitting element / light-receiving element array according to claim 1, wherein the light-receiving element is configured by a photodiode having a pn junction in the pnpn structure. The light emitting element array is composed of a self-scanning light emitting element array having a pnpn structure formed by epi growth,
The light-emitting element / light-receiving element array according to claim 1, wherein the light-receiving element is configured by an optical transistor including pnp or npn in the pnpn structure. The light emitting element / light receiving element array according to claim 4, wherein the light emitting element and the light receiving element are separated by mesa etching. The light emitting element / light receiving element array according to claim 4, wherein the light emitting element and the light receiving element are separated by a region insulated by ion implantation. A light emitting element / light receiving element array according to claim 1,
A lens array for condensing light from the light emitting element,
An optical writing head comprising: 9. The optical writing head according to claim 8, wherein the lens array is a rod lens. The optical writing head according to claim 8, wherein the lens array is a flat microlens. An optical printer comprising the optical writing head according to claim 9. An optical printer comprising the optical writing head according to claim 10. A light amount correction method for an optical writing head in the optical printer according to claim 11, wherein
The light emitting elements are caused to emit light, the light intensity sensor is used to measure the light emission intensity distribution for each light emitting element, and the light emitting intensity and / or lighting time of the light emitting elements are adjusted so that the light exposure of each light emitting element is uniform. Then, the light emission intensity or the exposure amount of each light emitting element unit or a plurality of light emitting element units is measured by a light receiving element, and the value is recorded in storage means in the driver circuit,
At the time of the time gap when printing with an optical printer, the light emitting element is caused to emit light, the light emission intensity or the amount of exposure is directly measured by the light receiving element, the value is compared with the value recorded in the storage means, and the difference is compared. A light amount correction method that corrects and adjusts the light emission intensity and / or lighting time of a light emitting element so that the exposure amount of each light emitting element unit or a plurality of light emitting element units becomes uniform. A light amount correction method for an optical writing head in the optical printer according to claim 12,
The light emitting element array emits light, the light emitting intensity or the exposure amount of each light emitting element unit or a plurality of light emitting element units is measured by the light receiving element, and the value is recorded in the storage means in the driver circuit,
At the time of the time gap when printing with an optical printer, the light emitting element is caused to emit light, the light emission intensity or the amount of exposure is directly measured by the light receiving element, the value is compared with the value recorded in the storage means, and the difference is compared. A light amount correction method that corrects and adjusts the light emission intensity and / or lighting time of a light emitting element so that the exposure amount of each light emitting element unit or a plurality of light emitting element units becomes uniform.

Images