JPH1158813A - LED writing light source device - Google Patents

Abstract

(57) [Summary] L used in a recording device of an electrophotographic system
In an ED writing light source device, variations in dot position and output can be maintained with high precision, and occurrence of warpage and twist due to heat generation can be suppressed, and a high-density good image can be obtained with an inexpensive configuration. To do. SOLUTION: A head unit 1 having a light source provided with a micro light emitting unit of an LED on the same substrate and a driver for driving the micro light emitting unit, and a head feed mechanism for moving the head unit 1 in a scanning direction are provided. . Then, the head unit 1 is moved in accordance with the image data, and a data signal at that position is sent to the driver to drive the LED to form an image on the photoconductor 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light source device for writing an LED on a photosensitive member in a recording apparatus using an electrophotographic method, such as a copying machine, a facsimile, a bar code printing machine, a printer, and a plotter.

[0002]

2. Description of the Related Art FIG. 10 is a diagram showing a configuration of an electrophotographic system having a digital optical system. In the figure, 101 is LE
A driving device for the D writing light source 102;
Reference numeral 04 denotes a charge removing lamp, 205 denotes a cleaner, 206 denotes a stacker serving as a paper discharge tray, 207 denotes a fixing device, 208 denotes a peeler, 209 denotes a transfer device, 210 denotes a paper feed cassette, 211 denotes a developing device, and 212 denotes a photosensitive drum. is there.

The conventional electrophotographic system uses an LED array as the light source 102 and controls the electric charge on the photosensitive drum 112 by causing only the necessary components to emit light from the LEDs of the minute light emitting section. Then, LE is set so that electric charges are left in the image area.
D irradiates light, and attaches a toner having an opposite charge to the remaining charge on the photoconductor. Alternatively, light is irradiated so as to erase the image portion, and a toner having the same charge as the charge on the photoconductor is attached. Then, an image can be recorded by transferring the attached toner to paper or the like.

FIGS. 11 to 13 show an LED writing light source used in the above-mentioned system. FIG. 11 shows the overall structure, FIG. 12 shows the structure of an LED head, and FIG. 13 shows a cross section of an LED array module. ing.

In FIG. 11, reference numeral 121 denotes an LED array chip,
Reference numeral 122 denotes a driver (IC) for driving the LED array chip 121, reference numeral 123 denotes a substrate on which those components and an SLA (concentrating rod lens array) 124 are mounted, and reference numeral 125 denotes SL.
A fixing metal fitting, 126 is an FPC (flexible wiring board) with GEP lining, 127 is an FPC press-fitting metal, 128 is a connector, and 129 is a base board supporting the above components.

In FIG. 12, reference numeral 131 denotes the above-mentioned SLA,
132 is an SLA holder, 133 is an LED module part,
134 is a circuit board, 135 is a mechanism, and in FIG.
141 is a common electrode wiring pattern, 142 is an individual electrode wiring pattern, 143 is W / B (wire bonding), 1
44 is a conductive paste, 145 is a driver for the LED 146, and 147 is a ceramic substrate.

[0007] LED array chip 121 and driver 12
2 are mounted on one substrate 123 correspondingly, and each electrode of the corresponding circuit between the LED array chip 121 and the substrate wiring patterns 141 and 142, and each electrode of the driver 145 is wire-bonded. It is connected. The common electrode of the LED array chip 121 is formed on the lower surface of the LED and has a conductive paste 1 such as an Ag paste.
44 are connected to the common pattern on the substrate 147.

[0008] The width of an image written by the above light source is limited by the length of the LEDs arranged on one line on the LED writing light source, and the resolution is limited by the dot pitch of the LEDs.

The LED chip used here is:
It is necessary to use a material which has a large absorption coefficient of light emitted in the crystal and low light leakage. Therefore, GaA
An LED in which GaAsP is grown on an s substrate is used.

FIG. 14 shows an example of the pattern of the LED chip. The wire bond electrode portions 152 of each light emitting portion 151 are arranged in a staggered manner. FIG.
Is a diagram showing a structural example of the LED, 153 is an aluminum electrode, 154 is an insulating tank, and 155 is an Au-Ge-Ni electrode.

When the print dot density is low, the driver 122 can be mounted on one side of the LED array chip 121, but when the dot density is high, the driver 122 is mounted on both sides as shown in FIG.

This driver includes a logic circuit section such as a shift register and a latch, and a driver section using transistors, and is integrated in 64-128 bits. Further, the current limiting resistor is provided in the IC in units of bits, and also functions as a stabilizing resistor when driving the LED.

FIG. 16 is a block diagram showing L constituting the driver 122.
FIG. 3 is a diagram illustrating a basic configuration of an ED drive circuit. This circuit is
As described above, the driver section 16 includes the register 161 to which the image signal is input, the latch 162, the AND gate 164 connected to the memory (ROM), and the driver section 165.
5 drives the LED array 166.

Here, in order to improve the uniformity of the LED writing light source, variation correction is performed. Typical methods for this variation correction include (1) LED chip rank selection, (2) electric Correction by dynamic control. Further, the method (2) is as shown in FIG.
(A) LED chip unit control and (b) LED dot unit control.

FIG. 17 is a diagram showing an energization time control circuit for correcting the above-mentioned variation, wherein 171 is a shift register, 172 and 172a and 172b are latch circuits, Q1 and Q2 are AND gates, and Tr1 and Tr2 are transistors. Is shown.

The exposure correction conditions by the above circuit are as follows. First, assuming that the exposure energy of the LED is E, the emission output of the LED is P _O , and the energization time of the LED is τ, the following equation is used.

E = P _O τ (1) When the correction energization time of each LED is τ (k), the following equation is established.

Τ (k) = T _O + (m−k) t (2) T _O : Common energizing time m: Number of correction steps t: Basic unit of additional time for correction k: Natural number (1 to m) From the above equations (1) and (2), they are expressed as follows.

E = {T _O + (m−k) t} P _O (3) Here, assuming that the exposure energies of an arbitrary LED emission output value B _k are E (k) and E (k−1). The following equation is obtained from the equation (3).

[0020] _{E (k) = {T O} + (m-k) t} B k (4) E (k-1) = {T O + (m-k + 1) t} B k (5) in this case The variation ΔE of the exposure energy is represented by (4),
The following is obtained from the equation (5).

The ΔE = {E (k) -E (k-1)} / {E (k) + E (k-1)} = 2 / {2T O + (2m-2k + 1) t} (6) The fluctuation ΔE is maximized when m = k. Therefore, ΔE at the maximum is expressed by the following equation.

ΔE = t / (2T _O + t) (7) Here, since T _O is an integral multiple of t, the energization time T _O is as follows.

[0023] _{T O = nt (8) n} : integer typically to the variation ΔE within 15% ±, (7), the following equation (8) is obtained.

ΔE = 1 / (2n + 1) ≦ 0.15 (9) From the above, n ≧ 2.8, and the minimum energization time is as follows.

[0025] T _O = 3t (10) Further, the basic unit t for correction is expressed by the following equation.

T = N / df (11) N: total number of dots d: number of data bits expressed in data processing format f: transfer clock frequency The maximum correction time τ (k) max is the one-line lighting time T Must be smaller. If T = 1 msec, m is equal to or less than 11 according to the equations (2) and (10). As described above, the corrected exposure energy maximum value and minimum value E
max and Emin are the maximum value Pmax of the LED emission output.
And the minimum value Pmin is as follows.

Emax = 3tPmax (12) Emin = (2 + m) tPmin (13) Here, as the print density increases, the number of dots increases. Accordingly, the basic unit t also extends. However, in order to make the lighting time of one line the same, it is necessary to shorten the energizing time.
For this purpose, it is necessary to make ΔE larger than 15%, or to increase the dot multiplication factor by a and the number of steps m ′ as follows.

M ′ ≦ 1 / at−2 (14) This is because ΔE is required to narrow the variation correction range of the LED.
This indicates that it is necessary to suppress the variation of the LED itself to 1 / a in order not to change.

The above description has been made on the case where the exposure amount is corrected by time. However, the correction may be performed by using the fact that the light emission output of the LED is proportional to the energizing current. This can be achieved by considering τ (k) as a basic unit of a correction energizing current, TO as a basic unit of a common energizing current, and t as a basic unit of an additional current for correction. Also in this case, since the maximum number m of steps of the correction cannot be changed similarly to the time correction, it is necessary to suppress the variation of the LED chip itself to the present level or less and to satisfy the linearity of the output-current value of the LED itself.

The above correction information is recorded in the ROM and is referred to as needed.

The driving of the LED writing light source is performed by the LE
This is a combination of a D emission output correction circuit and an IC driver, and the basic configuration is shown in FIG. 17 as an example of an LED dot control circuit.

Further, when driving the LED writing light source, a bit serial transfer format has to be adopted due to its configuration. FIG. 18 shows an interface between the head unit and the printer. The function of each signal is as follows.

DATA: Video input signal, LE
The light emission state of D is indicated.

CLOCK: A sampling clock for DATA and DTP.

DTP: a synchronization signal of the DATA signal.

Immediately after DTP is input, sampling of a video input signal is started in synchronization with CLOCK. On and Off of the LED are controlled by the logical level of DATA.

These data are input to the serial IN-parallel OUT shift register 171 and held by the latch circuits 172, 172a, 172b. Here, if the electrodes on the LED array chip are arranged in a zigzag pattern as shown in FIG. 14, the data must be distributed to the odd and even sides with respect to the LEDs. For this reason, it is necessary to convert the data input by bit serial into 2-bit parallel data and input it to the IC driver. Therefore, in FIG. 17A, since it is necessary to align the shift data, it is common to use a bidirectional shift register as shown in FIG. 17B and select the L / R terminal for indicating the shift direction.

Then, the correction information is input from the ROM to each IC driver, and after the information is latched by the latch circuit (1) of the IC driver, the print data is input to the shift register. The print data is held in the latch circuit (2), and at the same time, the logical product of the print data and the information of the latch circuit (1) is obtained.
The required exposure energy is emitted by being energized for each LED dot.

Although uniformity is required for the exposure energy, if undulation or the like occurs along the longitudinal direction of the LED writing light source, a light image formed on the photoreceptor is blurred, and the printing quality is reduced.

The light emitted from the LED chip is
It is necessary to form a dot-shaped light image on the photoreceptor through a 1 × image forming lens such as a selfoc lens. This is because there is a need for an erecting equal-magnification imaging system that enables images formed by adjacent lenses to overlap each other.
When passing through a SELFOC lens, the incident light travels meandering sinusoidally with respect to the optical axis. Therefore, even if the geometrical optical path lengths are different, light passing through the central axis also advances simultaneously regardless of the lens length, and forms an image as a lens.

If the lens deviates even slightly from the center of the object image distance TC, an MTF (Modulation Transfer Fun
ction) is significantly reduced. This is because, since the selfoc lens is a compound eye lens, if the 1: 1 imaging relationship is disrupted, the overlap of adjacent images is disrupted and the image is degraded. Therefore, it is necessary to have a degree of parallelism that keeps the center of the Selfoc lens and the TC within the standard at all points. Also, when the Selfoc lens is represented by the F value of an optically equivalent spherical lens,
The F value on the center is as follows.

F = (m / 2πK _N ) ^0.5 (1 / θ) (15) m: Degree of overlap θ: Opening angle N: Number of columns K _N is given by the number of columns as follows.

K ₁ = 1 K ₂ = 2- (1/8 m ² ) K ₃ = 3- (3/2 m ² ) K ₄ = 4- (15/4 m ² ) Also, the image plane obtained by the Selfoc lens Illuminance E
Is given by the following equation using the above F value.

E = (τπL / 16) (1 / F) ² (16) τ: equivalent ratio of lens L: LED luminance As described above, the aperture angle and the number of rows are larger, but the greater the degree of overlap, the darker.

[0045]

However, since the LED writing light source device in the conventional electrophotographic system is configured as described above, there are the following problems.

(1) The print interval (several thousands of dots)
Must be kept constant over time and require sophisticated manufacturing techniques.

(2) Since the characteristics of each chip differ due to variations in the LED substrate and variations due to impurity diffusion, correction by a driver IC or the like is required.

(3) Since a plurality of dots arranged in an array are simultaneously emitted, a large amount of heat is generated from the LED and the driver, and the substrate, the heat radiating plate, and the like are disturbed, and positional deviation is likely to occur.

(4) The interval between LED chips becomes narrower for higher density, and the defect occurrence rate due to misalignment increases.

(5) The defect occurrence rate of chip position shift due to die bond shift increases.

(6) Since a GaAs-based GaAsP VPE, which can be easily made planar, is used for the LED,
High output is difficult.

(7) When the density of LED dots is increased and the chip becomes a staggered arrangement electrode, it is necessary to convert image serial data into 2-bit parallel data.

(8) A controller for controlling the correction data and the serial data is required.

(9) Since the power consumption and the lighting time due to the light emission output correction are different for each dot, the variation is increased in a long term.

(10) When inspecting the manufactured LPH, it is necessary to inspect all the light emitting points.
It takes time and cost.

(11) Since a plurality of LED chips are used, there is a large variation in the wavelength in the product, and the variation may not be corrected due to the photoconductor sensitivity characteristics even when the output is corrected.

(12) It is necessary to select usable LEDs within a range in which the output can be corrected.

(13) A lens array of the same magnification imaging system is required, and a selfoc lens, a roof mirror lens array, a plurality of lens arrays for erectly forming an intermediate image, a flat microlens array, and the like are used. There must be.

(14) Since the length of the lens array such as a SELFOC lens is required for the printing width, the influence of the lens variation directly increases the variation of the LED exposure amount. In order to avoid this, it is necessary to select lenses, which causes an increase in cost.

(15) Although the SELFOC lens and the case are joined by silicone or the like, it is difficult to maintain the parallelism at the printing width due to manufacturing errors of the lens and the case, which causes a variation in the exposure amount.

(16) A leaf spring is used because the positional accuracy is regarded as important in the assembly. However, since the contact area between the PCB and the heat sink is regulated by the surface roughness, sufficient heat dissipation is obtained. Is difficult. Further, as the LED dot density increases, the amount of heat generated also increases, causing warpage.

(17) Since a current of several tens of A flows when all dots are lit, there are restrictions on the power supply capacity, responsiveness, and wiring system.

(18) In order to use a plurality of drivers,
Variations in drivers used on the same substrate affect variations in products. In order to prevent this, it is necessary to select drivers, which causes an increase in cost.

The present invention has been made by paying attention to the above-described problems, and it is possible to keep the dot position and the output variation highly accurate, and to suppress the occurrence of warpage and twist due to heat generation. It is an object of the present invention to provide an LED writing light source device capable of obtaining a high-density good image with an inexpensive configuration.

[0065]

An LED writing light source device according to the present invention is configured as follows.

(1) A light source provided with a small light emitting portion of an LED on the same substrate, a head portion having a driver for driving the small light emitting portion, and moving means for moving the head portion in the scanning direction. The head unit is moved in accordance with the image data, and a data signal at that position is sent to the driver to drive the LED to form an image on the photoreceptor.

(2) In the apparatus of the above (1), the minute light emitting portion has a plurality of dots on one line, and this line is arranged in the horizontal direction with respect to the photosensitive member moving direction.

(3) In the device of the above (1), the minute light emitting portion has a plurality of dots on one line, and this line is arranged in a direction perpendicular to the moving direction of the photoconductor.

(4) In the device of the above (1), the minute light emitting section has a plurality of dots on a plurality of rows, and the rows are arranged in the horizontal direction with respect to the photosensitive member moving direction.

(5) In the apparatus of the above (1), the minute light-emitting portion has a plurality of dots on a plurality of rows, and the rows are arranged in the horizontal direction with respect to the photosensitive member moving direction.

(6) In any one of the above-mentioned devices (1) to (5), a lens unit of the same-magnification imaging system such as a SELFOC lens is provided.

(7) In any one of the above-mentioned devices (1) to (5), the condenser lens is provided with a lens portion which forms an image at a magnification equal to that of a minute light emitting portion on the photosensitive member by a condenser lens.

(8) In any one of the above-mentioned devices (1) to (5), the minute light emitting portion is reduced by a lens to increase the resolution.

[0074]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a view showing a schematic configuration of a mechanism section according to an embodiment of the present invention, and shows a positional relationship between a scanning head section and a photosensitive member in a recording apparatus using electrophotography. . In the figure, 1 is a head unit, 2 is an automatic position detecting mechanism, 3 is a head feed mechanism (moving means) having a driving motor, and 4 is a photoconductor.

FIG. 2 is a diagram showing a detailed configuration of the head unit 1. As shown in FIG. In the figure, 11 is an LED section, 12 is an LED section 11
13 is an LED unit 11 and a lens unit 14
And 15 is a driver IC unit.

FIGS. 3A and 3B show the LED section 11.
FIG. 3 is a cross-sectional view showing details of a light source unit. In the figure, 21 is a metal electrode, 22 is a diffusion mask, and 23 is a constant composition region (VP
E), 24 is a composition transition region (VPE), 25 is a substrate crystal part, 26 is a metal electrode, and the peak wavelength is λp = 650.
nm.

FIG. 4 is a block diagram showing the configuration of a control system of the head unit 1. As shown in FIG. In the figure, reference numeral 31 denotes a timing signal generating circuit for outputting a timing signal to each unit, 32 denotes a memory for storing image data, 33 denotes a driver of an LED 34, 35 denotes a driver of a motor 36, and 37 denotes a driver of a sensor 38.

The above-described head unit 1 has a single light source as shown in FIG. 2, moves this light source to a prescribed position,
D is turned on in accordance with the image data at that position.
At this time, assuming that the moving speed of the photoconductor 4 is I (mm / s), the printing density is N (dpi), and the printing width is L (mm), the printing width L is the line speed V (mm / s) at which the light source moves. ) Becomes as follows.

V = NI / 25.4 (21) Therefore, the time T (s) required for one line is expressed by the following equation.

T = 25.4 / NI (22) The number of dots n included in the print width is as follows.

N = NL / 25.4 (23) The light emission time t (s) per light is expressed by (22),
The following is obtained from the equation (23).

T = T / n = (25.4) ² / N ² IL (24) Also, assuming that the emission output of the LED 11 is P (mW / cm ² ) and the transmission efficiency of the optical system is η _T , The above light irradiation energy E (μJ / cm ² ) is given by the following equation.

E = Pη _T t = Pη _T (25.4) ² / N ² IL (25) If the sensitivity of the photoconductor 4 is η _P (cm ² / μJ),
The exposure amount is I / η _p . Therefore, since the light irradiation energy needs to be equal to or more than this exposure amount, the following equation is obtained.

E ≧ I / η _p (26) From the equations (25) and (26), the following equation is obtained.

Pη _T (25.4) ² / N ² IL ≧ I / η _p P ≧ N ² IL / (25.4) ² η _T η _P (27) From the above, the LED emission output is higher than P I just want it.

Then, the head unit 1 having the LED is driven by a stepping motor, a DC motor, or an AC servomotor. When the head unit 1 moves, it is necessary to transmit torque, but a belt or a ball screw is used for this. FIG. 1 shows a state in which the head unit 1 of FIG. 2 is attached to a ball screw. This head is shown in FIG.
It is composed of a middle LED section 11, a board section 12, a case section 13, a lens section 14, and a driver IC section 15.

The LED has a single light source as shown in FIG. 3, and the light source forms an image on the photoreceptor by a condenser lens or a lens system capable of reducing the light source to a degree satisfying the resolution of the light source. The image data is stored in the memory in one cycle (one round trip) or a plurality of times. A signal is transmitted to the motor driver in synchronization with the data calling data clock. Then, the head unit 1 moves in accordance with this signal, the image data stored in the memory at that point is taken out of the memory, transmitted to the LED driver, and the image at that position is formed on the photoconductor.

Further, an LED having a wavelength characteristic having the highest sensitivity to the wavelength sensitivity of the photosensitive member 4 may be selected. For example, in the case of the distribution sensitivity characteristic as shown in FIG. 5, an LED having a peak wavelength of 950 nm using GaAs as a substrate may be used.

FIGS. 6 to 9 show monolithic array type light sources. In the figures, reference numeral 41 denotes an anode electrode, 42 denotes an epitaxial layer, 43 denotes an n-GaAs substrate, and 44 denotes a cathode electrode.

These light sources emit a specific wavelength in accordance with the sensitivity characteristics of the photosensitive member, and are characterized in that they are formed on a monolithic substrate. These dots are formed on a wafer formed by vapor phase growth or liquid phase growth by forming a selective expansion or epi phase in a constriction type by etching or by selective growth such as CVD or MBE.

During the closed loop control, the final end of the photosensitive member is detected by the automatic position detecting mechanism 2 shown in FIG. 1 and correction is performed.

Then, as shown in FIG. 6, the arrangement direction of the dots of the LED having the minute light emitting point on the substrate of the monolithic compound semiconductor is set to the horizontal direction with the moving direction of the photoconductor. That is, the direction is perpendicular to the head feed direction. The head with this LED is a condenser lens or a 1x imaging lens,
Alternatively, an image is formed on the photoreceptor by a lens system that can be reduced to satisfy the resolution of the light source. Then, the image data (1) when the formed dot width is moved from the left (right) end to the right (left) end in a direction orthogonal to the moving direction of the photoconductor, and only the dot length from the final position. There is image data (2) from the position shifted in the photoconductor moving direction to the left (right) end, and this image data (1) and image data (2) are defined as one cycle (one reciprocation).

The image data is stored in the memory in one cycle (one round trip) or a plurality of cycles. A signal is transmitted to the motor driver in synchronization with the data calling data clock. The head moves in accordance with this signal, the image data stored in the memory at that point is taken out of the memory, transmitted to the LED driver, and the image at that position is formed on the photosensitive member.

In the case of FIG. 6, the head moves to the position X in the head scanning direction, and 7-bit data in the photosensitive member moving direction at that position is transferred to the LED driver.
The ED emits light. Under this light emission condition, in the case of a 1 × imaging lens, the LED light emission point and the image formation point can be on the same side, so that the 7-bit data may be in phase. However, in the case of a condenser lens or a reduction system lens, since the LED light emission point and the image formation point are reversed, the 7-bit data needs to be in the opposite phase.

After the head moves from the left (right) end to the right (left) end, the photosensitive member moves by 7 bit width and moves again from the right (left) end to the left (right) end of the head. .

Further, as shown in FIG. 7, the direction is the direction perpendicular to the moving direction of the photoconductor having the arrangement direction of the dots of the LED having the minute light emitting point on the substrate of the monolithic compound semiconductor. In other words, it is horizontal with the head feed direction. The head having this LED forms an image on the photoreceptor by using a condenser lens, an equal-magnification imaging lens, or a lens system that can be reduced to a degree satisfying the resolution of the light source. Then, the image data (1) when the formed one dot width is moved from the left (right) end to the right (left) end in a direction orthogonal to the moving direction of the photoconductor, and one dot from the final position. There is image data (2) from the position shifted by the photoconductor moving direction by the length to the left (right) end, and the image data (1) and the image data (2) are defined as one cycle (one reciprocation).

The image data is stored in the memory in one cycle (one round trip) or a plurality of cycles. A signal is transmitted to the motor driver in synchronization with the data calling data clock. The head moves in accordance with this signal, the image data stored in the memory at that point is taken out of the memory, transmitted to the LED driver, and the image at that position is formed on the photoconductor.

In the case of FIG. 7, the head moves to the position X in the head scanning direction, and 7-bit data in the head scanning direction at that position is transferred to the LED driver, and the LED emits light. Under this light emission condition, in the case of a 1 × imaging lens, the LED light emission point and the image formation point can be on the same side, so that the 7-bit data may be in phase. However, in case of condenser lens or reduction type lens, LED
Since the light emitting point and the imaging point are reversed, the 7-bit data needs to be in the opposite phase. The movement of the head unit is performed in units of 7 bits.

After the head has moved from the left (right) end to the right (left) end, the photosensitive member moves by one bit width and moves again from the right (left) end to the left (right) end of the head. .
By repeating this, an image is created on the photoconductor.

Further, as shown in FIG. 8, the arrangement direction of two dots of LEDs having minute light emitting points on the substrate of the monolithic compound semiconductor is defined as the direction perpendicular to the moving direction of the photosensitive member, and the arrangement direction of seven dots is defined as the direction of the photosensitive member. Let it be parallel to the moving direction. This L
The head having the ED forms an image on the photoreceptor by using a condenser lens, an equal-magnification imaging lens, or a lens system that can be reduced to a degree satisfying the resolution of the light source. The image data (1) when the formed dot width is moved from the left (right) end to the right (left) end in a direction orthogonal to the moving direction of the photoconductor, and the photoconductor by the dot length from its final position. There is image data (2) from the position shifted in the movement direction to the left (right) end, and this image data (1) and image data (2) are defined as one cycle (one reciprocation).

In the image data, one cycle (one round trip) or a plurality of cycles of data is stored in the memory. A signal is transmitted to the motor driver in synchronization with the data calling data clock. The head moves in accordance with this signal, the image data stored in the memory at that point is taken out of the memory, transmitted to the LED driver, and the image at that position is formed on the photosensitive member.

In the case of FIG. 8, the head is moved to the position X in the head scanning direction, and A, B with respect to the photosensitive member moving direction at that position.
7-bit data of each column is transferred to the LED driver,
Accordingly, the LED emits light. In this light emission condition, in the case of a 1 × imaging lens, the LED light emission point and the image formation point can be on the same side, so that the data of 7 bits in columns A and B may be in phase. However, in the case of a condenser lens or a reduction-type lens, since the LED light emission point and the image formation point are reversed, it is necessary to rotate the phases of the A and B columns and 7-bit data by 180 degrees. The movement of the head unit is performed in units of 2 bits.

After the head has moved from the left (right) end to the right (left) end, the photoreceptor moves by a width of 7 bits and moves again from the right (left) end of the head to the left (right) end. .
By repeating this, an image is created on the photoconductor.

As shown in FIG. 9, the 7-bit arrangement direction of the LED having a small light emitting point on the substrate of the monolithic compound semiconductor is perpendicular to the moving direction of the photoconductor, and the 2-dot arrangement direction is the direction of the photoconductor. Let it be parallel to the moving direction. This L
The head having the ED forms an image on the photoreceptor by using a condenser lens, an equal-magnification imaging lens, or a lens system that can be reduced to a degree satisfying the resolution of the light source. The image data (1) when the formed dot width is moved from the left (right) end to the right (left) end in a direction orthogonal to the moving direction of the photoconductor, and the photoconductor by the dot length from its final position. There is image data (2) from the position shifted in the movement direction to the left (right) end, and this image data (1) and image data (2) are defined as one cycle (one reciprocation).

The image data is stored in the memory in one cycle (one round trip) or a plurality of cycles. A signal is transmitted to the motor driver in synchronization with the data calling data clock. The head moves in accordance with this signal, the image data stored in the memory at that point is taken out of the memory, transmitted to the LED driver, and the image at that position is formed on the photosensitive member.

After the head moves from the left (right) end to the right (left) end, the photoreceptor moves by a width of 2 bits and moves again from the right (left) end of the head to the left (right) end. I do.

In the case of FIG. 9, the head is moved to the position X in the head scanning direction, and A, B with respect to the photosensitive member moving direction at that position.
7-bit data of each column is transferred to the LED driver,
Accordingly, the LED emits light. In this light emission condition, in the case of a 1 × imaging lens, the LED light emission point and the image formation point can be on the same side, so that the data of 7 bits in columns A and B may be in phase. However, in the case of a condenser lens or a reduction system lens, since the LED light emission point and the image formation point are reversed, the data of the A and B columns and 7 bits must be rotated by 180 degrees. The movement of the head unit is performed in units of 7 bits.

Then, after the head section moves from the left (right) end to the right (left) end, the photosensitive member moves by 2 bit width, and moves again from the right (left) end to the left (right) end of the head section. I do. By repeating this, an image is created on the photoconductor.

As described above, in this embodiment, only one monolithic substrate needs to be used, and it is possible to maintain high positional accuracy and high output variation. Further, heat generation by the LED and the driver IC can be minimized, and occurrence of warpage, twist, and the like due to heat generation can be prevented. In addition, a GaAs-based G
High output can be achieved by using a double heterobase made of AlGaAs without relying on the VPE of aAsP. In addition, since a plurality of LED chips are not used, miniaturization can be performed without considering deviation between LED chips. In the case where the exposure energy has gradation, only one IC for gradation is required. Regarding the lens,
Since a lens array corresponding to the printing width is not required, it is easy to suppress variations in the lenses. Further, it is not always necessary to use the same-magnification imaging lens, and by using the reduction optical system, it is possible to produce an image having a higher density than the dot density on the LED chip.

[0110]

As described above, according to the present invention, variations in dot positions and outputs can be maintained with high accuracy, and the occurrence of warpage or twist due to heat generation can be suppressed. There is an effect that a good image with high density can be obtained.

[Brief description of the drawings]

FIG. 1 is a perspective view schematically showing a mechanism section according to an embodiment of the present invention.

FIG. 2 is a configuration diagram showing details of a head unit.

FIG. 3 is a sectional view showing details of a light source unit.

FIG. 4 is a block diagram illustrating a configuration of a control system of a head unit.

FIG. 5 is a diagram illustrating spectral sensitivity characteristics of a photoconductor;

FIG. 6 is a diagram showing a horizontal monolithic array type light source.

FIG. 7 is a diagram showing a vertical monolithic array type light source.

FIG. 8 is a plan view showing a horizontal two-dimensional monolithic array light source.

FIG. 9 is a plan view showing a vertical two-dimensional monolithic array type light source.

FIG. 10 is a sectional view showing the configuration of an electrophotographic system having a digital optical system.

FIG. 11 is a perspective view showing a configuration of an LED writing light source.

FIG. 12 is an exploded perspective view showing the structure of an LED head.

FIG. 13 is a sectional view of an LED array module.

FIG. 14 is a plan view showing a pattern example of a chip;

FIG. 15 is a sectional view showing an example of the structure of an LED.

FIG. 16 is a block diagram showing a basic configuration of an LED drive circuit.

FIG. 17 is a diagram showing an LED energization time control circuit.

FIG. 18 is an explanatory diagram showing an interface with a printer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Head part 2 Automatic position detection mechanism 3 Head feed mechanism (moving means) 4 Photoconductor 11 LED part 12 Substrate part 13 Case part 14 Lens part 15 Driver IC part

Claims (8)

[Claims] A light source provided with a micro light emitting portion of an LED on the same substrate, a head portion having a driver for driving the micro light emitting portion, and moving means for moving the head portion in a scanning direction; An LED writing light source device, wherein a head section is moved in accordance with image data, and a data signal at the position is transmitted to the driver to drive an LED to form an image on a photosensitive member. 2. The LED writing light source according to claim 1, wherein the minute light emitting portion has a plurality of dots on one row, and the rows are arranged in a horizontal direction with respect to a moving direction of the photoconductor. apparatus. 3. The LED writing light source according to claim 1, wherein the minute light emitting portion has a plurality of dots on one line, and the line is aligned in a direction perpendicular to a moving direction of the photoconductor. apparatus. 4. The light source for LED writing according to claim 1, wherein the minute light emitting section has a plurality of dots on a plurality of rows, and the rows are arranged in a horizontal direction with respect to a moving direction of the photoconductor. apparatus. 5. The LED writing light source according to claim 1, wherein the minute light emitting section has a plurality of dots on a plurality of rows, and the rows are aligned in a horizontal direction with respect to a moving direction of the photoconductor. apparatus. 6. The LED writing light source device according to claim 1, further comprising a lens unit of an equal-magnification imaging system such as a selfoc lens. 7. The LED writing light source device according to claim 1, further comprising a lens portion that forms an image at an equal magnification with a minute light emitting portion on the photosensitive member by a condenser lens. 8. The LED writing light source device according to claim 1, wherein the minute light emitting section is reduced by a lens to increase the resolution.