JP2003097910A - Line light source, sheet detecting device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a line light source capable of uniformly illuminating an object to be illuminated, and provide a sheet detecting device and an image forming device capable of accurately detecting a sheet by using the line light source. SOLUTION: The line light source is composed of an approximately cylindrical optical guiding body 114-B made up of a transparent material, a case 504 and a case cover 505 containing the optical guiding body 114-B, an LED 114-A projecting light onto one edge surface of the optical guiding body 114-B, and a deflecting film 503 deflecting the light projected from an aperture 506 disposed on the case cover 505. In the optical guiding body 114-B, a tapering surface is formed on the section of side surface opposite to the aperture 506, and a plurality of knurling worked grooves 502 are formed on the tapering surface. Each reflecting surface of knurling worked grooves 502, which faces the LED 114-A and is disposed further from the LED 114-A, is arranged closer to the optical axis of the LED 114-B.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a linear light source for irradiating linear light, and a sheet detecting device and an image forming apparatus using the linear light source.

[0002]

2. Description of the Related Art Conventionally used linear light sources include those used in document reading devices such as FAX. An example thereof is shown in FIGS. 27 and 28.

The linear light source shown in FIG. 27 is composed of a light guide 1113-B and an LED 1113-A made of a transparent resin. As illustrated, the light emitted from the LEDs is diffusely reflected downward by the granular diffuse reflection surface 1002 formed on the upper surface of the light guide body 1113-B, thereby creating a light source that emits linearly. . By irradiating the sheet 1001 with this light source and reading the reflected light with a sensor arranged in a line (not shown), the density of the sheet 1001 as an irradiation target is read.

The linear light source shown in FIG. 28 has the structure proposed in Japanese Patent No. 3104847, and includes LED1114-
It is a light source that reflects the light emitted from A in a certain direction by the knurled groove 1003 formed on the upper surface of the light guide body 1114-B and irradiates it downward. As shown, LED1114-
The light incident from A is repeatedly reflected in the light guide body 1114-B, and the reflection surface 1004 of the knurled groove 1003 formed in the upper portion of the light guide body is cut into an isosceles triangle shape.
The sheet 1001 is reflected by the sheet 1001 with a predetermined angle θp.
Is irradiated.

FIG. 29 is a diagram showing the amount of light emitted by the linear light source of FIG. 28 from point A to point B.
As shown in the figure, the light amount is strong at the position A close to the LED 1114-A, and becomes weaker as the distance from the LED increases.

[0006]

However, since the linear light source described in the above-mentioned conventional example has the following characteristics, it is not suitable for uniformly and accurately irradiating an irradiation object (sheet). . Therefore, when it is used as a light source for a sheet detection device or the like, a detection error may occur.

The amount of light emitted from the light guide is not uniform,
The amount of light is high in a place near the LED and is low in a place away from the LED. Therefore, the amount of light that illuminates the object to be irradiated becomes uneven.

The outgoing angle of the outgoing light from the light guide is not vertical, but is angular. The line-shaped light source of FIG. 27 is a broad emission, which is a collection of lights having various angles, and the line-shaped light source of FIG. 28 is light having a predetermined angle θp.

The present invention has been made to solve the above-mentioned problems of the prior art, and an object thereof is to provide a line light source capable of uniformly irradiating an object to be irradiated, and a line light source using the line light source. An object of the present invention is to provide a sheet detection device and an image forming apparatus that can perform sheet detection with high accuracy.

[0010]

In order to achieve the above-mentioned object, a linear light source of the present invention includes a light guide member having a substantially cylindrical shape having a light transmitting property, and the light guide member that stores the light guide member. The light emitted from the point light source includes a light guide housing having a slit-shaped opening formed along the axis of the body, and a point light source that irradiates one end face of the light guide with light. In the linear light source that reflects the light in the light guide body and emits it as linear light from the opening, the side surface of the light guide opposite to the opening faces the point light source. A plurality of grooves having a reflecting surface that reflects light from the light source are formed side by side in the axial direction, and the reflecting surface facing the point light source is closer to the optical axis of the point light source as the groove is farther from the point light source. It is arranged in.

The groove is a groove having a triangular cross section formed in a direction orthogonal to the axis of the light guide, and
The reflective surface of the groove facing the point light source preferably has a larger area than the other surface.

It is further preferable to provide a deflecting member for refracting the light emitted from the opening so that the light is perpendicular to the irradiation object.

Further, the sheet detecting apparatus of the present invention uses a linear light source arranged along the width direction of a conveyed sheet and straddling an end portion in the width direction of the sheet, and a linear irradiation light of the linear light source. A light-receiving element array having a plurality of corresponding light-receiving elements, and a sheet detection device that detects the position in the width direction of the sheet by partially shielding or reflecting the linear irradiation light by the sheet, as a linear light source. The linear light source of the present invention is used.

An image forming apparatus of the present invention is characterized by comprising the above-mentioned sheet detecting device and an image forming means for determining an image forming timing on a sheet based on a detection result of the sheet detecting device. .

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the present invention will be illustratively described in detail below with reference to the drawings. The linear light source according to the present invention is suitable for being used as a light source of a sheet detecting device, and such a sheet detecting device is used in an electrophotographic or inkjet image forming apparatus such as a printer, a copier, or a facsimile. It is suitable to be used as a sheet position detecting means for determining the image forming timing.

Unless otherwise specified, the dimensions, materials, shapes, relative arrangements, and the like of the constituent parts described in the following embodiments limit the scope of the present invention thereto. It's not meant.

(First Embodiment) FIG. 1 is a schematic sectional view of a linear light source according to a first embodiment of the present invention.

1 and 2 show a schematic configuration of a linear light source according to a first embodiment of the present invention. FIG. 1 is a schematic sectional view of a linear light source according to the present embodiment, and FIG. 2 is a schematic perspective view showing the structure of the linear light source.

As shown in FIGS. 1 and 2, the linear light source of this embodiment has a substantially cylindrical light guide 114-B formed of a material having a light-transmitting property (for example, resin) and a light guide. Light body 114
A case 504 and a case lid 505 as a light guide storage body that stores −B, and an LED formed in the case 504.
An LED (light emitting diode) 114-A as a point light source which is attached to the attachment hole 507 and irradiates light to one end surface of the light guide 114-B, and light emitted from an opening 506 provided in the case lid 505 are provided. And a deflecting film 503 as a deflecting member for refracting.

The light guide 114-B has a knurl cut on the side surface located on the side opposite to the opening 506. Specifically, first, a tapered surface is formed on the side surface portion, and a plurality of knurled grooves 502 having a triangular cross section are formed on the tapered surface in a direction orthogonal to the axis of the light guide 114-B.

The groove depths of the knurled grooves 502 are substantially the same, but the tapered surfaces are formed at a predetermined angle so as to approach the central axis of the light guide 114-B as the distance from the LED 114-A increases. LED in each knurl groove 502
The reflective surface facing 114-A is arranged closer to the optical axis of the LED 114-B as the knurled groove 502 farther from the LED 114-A is. In this embodiment, the length (width in the direction orthogonal to the light guide 114-B) w of each knurled groove 502 is substantially constant.

The case 504 and the case lid 505 are made of a material that blocks light. Also, the opening 506
Are formed in a slit shape along the axis of the light guide 114-B. In addition, in the present embodiment, the width u of the opening 506 is set to be substantially constant.

In this structure, the light emitted from the LED 114-A to the one end surface (the left end surface in FIG. 1) of the light guide 114-B is guided into the light guide 114-B and reflected by the knurled groove 502. The light is reflected by the surface (mainly the surface facing the LED 114-A) at a critical angle, and is emitted as linear light from the opening 506 of the case lid 505. The emitted light has a predetermined angle depending on the angle of the reflecting surface of the knurled groove 502.

The deflecting film 503 is for refracting and transmitting outgoing light, and its refractive index is knurl 50.
It is set according to the angle of the two reflecting surfaces. Specifically, the above-described predetermined angle of the emitted light is just canceled and the transmitted light of the deflection film 503 is guided by the light guide 114-.
The light is refracted so that the light is perpendicular to the irradiation target arranged parallel to the B axis.

An example of applying the linear light source to a sheet detecting device of an electrophotographic image forming apparatus will be described in detail below.

FIG. 3 is a schematic view of the sheet detecting apparatus according to this embodiment. The sheet detection device includes a linear light source and a sensor module 115 arranged at a position facing the linear light source.
And is configured. The sensor module 115 is a light-receiving element array in which light-receiving elements are arranged in a row corresponding to the linear irradiation light from the linear light source (hereinafter, the edge sensor 1
15). The main line light source and the sensor module are attached to a sheet conveying path of the image forming apparatus as will be described later, and are used as a paper lateral edge detecting unit for detecting a positional deviation of the left edge of the sheet.

FIG. 4 shows the voltage of the analog signal output from each element of the edge sensor 115, which is shown in FIG.
It is a graph showing the light distribution characteristic of 4-B. Details will be described later.

FIG. 5 shows an example of a schematic configuration of a printer engine of the image forming apparatus according to this embodiment, and an example of a system in which the above-described paper lateral edge detecting means or the light guide 114-B can be utilized. Is.

Based on the schematic configuration of the printer engine shown in FIG. 5, the outline of the double-sided printing sequence will be described below as an example.

When the image data from the video controller 101 (see FIG. 6) is printed on the first surface (front surface) of the recording medium (sheet) conveyed from the paper feeding unit 209 (flow X), the registration roller 202 is used. Remove the skew of the recording medium with. A TOP sensor 117 (see FIG. 7) for detecting the leading edge of the recording medium is arranged at the same position as the registration roller 202, and at the same time as removing the skew,
The CPU 304 of the printer engine 102 recognizes that the front end of the recording medium has reached a predetermined position.

Thereafter, before the image data is recorded on the recording medium, and while the recording medium is attracted to the electrostatic transport belt 208 by the suction roller 203 and is transported, the recording is performed by the paper lateral edge detecting means 201 in the printer engine 102. The side edge of the medium is detected. Here, the paper edge (for example, the left edge) on the horizontal scanning start side is detected. Paper edge detection unit 20
1 uses an optical sensor so that it can be detected without touching the recording medium, and includes a line light source 114 and an edge sensor 11.
It is composed of 5. The output from the edge sensor is processed by a desired electric circuit described later, and the lateral edge position of the recording medium can be detected.

As a detection method in the present embodiment, light is applied to an optical sensor in which light receiving elements are arranged in a line in an array, and whether the irradiation light is shielded by the recording medium or not. The case where the end portion is detected without contacting the recording medium is shown. However, the detection method is not particularly limited to this embodiment. It is also possible to detect the edge of the recording medium by reflecting the irradiation light to the recording medium like other optical means.

Then, the sending timing of the image data sent from the video controller 101 is changed in accordance with the left end position of the recording medium, and the lasers in the optical scanners of the respective colors are based on the image data sent to the printer engine 102. Drive circuit 116-C, 116-Y, 116-
By driving M and 116-K, toner images are formed on the photosensitive drums 204 to 207 of the respective colors, transferred onto a recording medium, and the fixing device 210 fixes the toner image on the recording medium. In this way, even if the left edge position of the recording medium is misaligned,
By changing the transmission timing of the image data accordingly, printing can always be performed at the same position from the left end of the recording medium.

After the printing on the first side (front side) is completed, the recording medium is switched back by the sheet discharge roller 211 and is conveyed by the double-sided conveying roller 212. Then, the paper is re-fed to the registration roller 202 (flow of Y), and the leading edge of the paper is fed to the TOP sensor 11
When the second side (back side) is detected, the paper lateral edge detecting means 201 also detects the left edge of the recording medium. Similar to the case of the first surface, the sending timing of the image data sent from the video controller 101 is changed based on the left end position of the recording medium, and printing is performed at a desired position on the paper.

FIG. 6 is a block diagram of the entire image forming apparatus. The video controller 101 receives print information from a host computer (not shown), and the image expansion unit
It is expanded into bitmap image data and stored in a page memory (not shown). The image output control unit controls the horizontal synchronization signal (BD signal 11) sent from the printer engine 102.
The image data 110 is sent to the printer engine 102 based on 1) and the vertical synchronizing signal (TOP signal 112). In addition, the video controller 101 and the printer engine 102 periodically transmit and receive information via the serial communication line 113.

FIG. 7 is a block diagram of an electric control circuit relating to image generation of the printer engine.

In the figure, 110-K, 110-M, 1
10-Y and 110-C are image data of YMCK colors sent from the video controller 101, and 116
It is input to the laser drive circuit section of each color of -K, 116-M, 116-Y, 116-C. Reference numeral 117 denotes a TOP sensor, which is a sensor arranged on the conveyance path of the recording medium to detect the front end of the recording medium. CPU304
Is the signal 123 transmitted from this TOP sensor 117.
Is monitored, and when the leading edge of the recording medium reaches a predetermined position, the video controller 101 waits for a certain period of time.
By sending the OP signal 112, the start of sending the image data is instructed. 400-A is a sensor control unit, which is a signal 1 for controlling the edge sensor 115 and the line light source 114.
19 and 118 are generated. 400-B is an edge detector, which is a signal 120 sent from the edge sensor 115.
Is processed by a desired processing circuit to detect the positional deviation of the lateral end portion of the recording medium. CPU304
Transmits the amount of positional deviation obtained from the information 122 from the edge detection unit 400-B to the video controller 101 via the serial communication line 113.

FIG. 8 is a timing chart of image data in the sheet conveying direction (sub-scanning direction) of the image forming apparatus. The TOP sensor output signal 123, the serial communication line 113, the TOP signal 112, and the image data 1 of FIG.
10 shows timings for double-sided printing for 10-K, 110-M, 110-Y, and 110-C.

When the TOP sensor output signal 123 becomes HIGH, it means that the leading edge of the recording medium has reached a predetermined position. After a predetermined time (the time when the leading edge reaches the edge sensor 115), the CPU 304 detects the positional deviation of the left end edge of the recording medium with the edge sensor 115, and the video controller 101 with the serial communication line 113.
The left edge shift amount is notified to. Video controller 1
01 reflects the received positional deviation amount in the left margin. Further, the CPU 304 uses the video controller 10
1 is the TOP signal 112, which is a synchronization signal for transmitting the C-color image data 110-C, and the TOP sensor output signal 1
It is sent to the video controller 101 after T (t-c) time from the rising edge of 23. Video controller 101
As shown in FIG. 5, the recording medium is the photosensitive drum 20 of each color.
Image data 1 considering the time difference of reaching 4 to 207
Must send 10. After printing the first side, the second side is printed through the double-sided conveyance roller 212. The timing of each signal on the second surface is the same as that on the first surface.

FIG. 9 is a timing chart showing the timing of sending image data in the sheet width direction (main scanning direction) of the image forming apparatus. BD-C, BD-Y, BD in the figure
The -M and BD-K signals are horizontal synchronization signals, which are signals that are generated each time one line is printed. The video controller 101 sends the image data 110 by adding the timing Tedg according to the left edge shift amount of the recording medium to the predetermined time Tbd from the rising edge of the BD signal,
Printing is performed at a predetermined position from the left edge of the recording medium.

The BD signals of the respective colors are controlled so that their cycles are completely the same, but they may have a phase difference.

FIG. 10 is an enlarged view of a part of the light guide 114-B and the deflection film 503 of FIG.

The description of FIGS. 3 and 10 will now be given.

The light guide 114-B is a cylindrical part made of a transparent resin or the like as described above, and has a notch called a knurled groove 502 formed on the upper part thereof. This light guide 1
The role of 14-B is to reflect the light emitted from the LED 114-A on the inner surface of the light guide 114-B, emit parallel light in the downward direction, and illuminate the edge sensor 115.

As shown in FIG. 3, the light guide 114-B has a cylindrical shape having a length f [mm] and a diameter h [mm], and the knurled groove 502 is separated from the LED 114-A. According to the inside of the cylinder (direction approaching the LED optical axis)
On the opposite side of the LED 114-A, g [m
m] The position is closer to the inside.

Next, the path of light will be described. LED
The light emitted from 114-A is emitted in various directions as shown in FIG. This depends on the directional characteristics of the adopted LED. In general, when light is incident through different materials, it is said that light incident over a critical angle (an angle uniquely determined by the two materials) is totally reflected without loss. Light incident at an angle deeper than the critical angle is refracted and incident at a predetermined refraction angle. The light incident from the LED 114-A reaches the knurling groove 502 while reflecting on the inner wall of the light guide 114-B, and if the incident angle with the knurling surface (reflection surface) exceeds the critical angle, the light is directed downward. Light is totally reflected to the outside of the light guide 114-B, and the deflection film 50
The light is refracted at 3, and the edge sensor 115 is vertically irradiated with light. At this time, light whose incident angle with the knurled surface is deeper than the critical angle will penetrate through the knurled surface.
Since the distance between 4-A and the edge sensor 115 is sufficient and the angles of the light passing through the light guide body are substantially in the same direction, the light emitted from the light guide body 114-B to the outside is substantially the same. The angles are almost the same. Since the light radiated in the same direction is refracted by the deflection film 503, the light radiated by the edge sensor 115 becomes parallel light and light perpendicular to the sheet which is the object to be irradiated.

Further details will be described with reference to FIG. The shape of the knurled groove 502 is determined by the length c of the reflecting surface, the pitch b, the groove angles θ and θ ′, and the inclination α of the entire groove. As the length c of the reflecting surface is longer, the amount of reflected light tends to increase (see FIG. 11). Therefore, from the side D-E, the side C
The reflection efficiency can be increased by increasing the length of -D so that the reflection surface facing the LED 114-A has a larger area than the other surface. The groove pitch b affects the sharpness of the shadow projected on the edge sensor at the left edge of the paper. If the pitch is too fine, the reflected light will be diffused and the shadow at the left end will be blurred, and as a result, the edge sensor 1
The left end of the output signal of 15 has a large inclination.
If the pitch is too coarse, the intervals of the light beams become coarse, and as a result, the inclination of the left end portion of the output signal of the edge sensor 115 becomes large. See FIG.

For reference, the angle γ emitted from the light guide 114-B toward the deflection film 503 is 23 degrees under the following conditions. Diameter of light guide: h = 4 mm Overall length of knurled groove: f = 140 mm Inclination of knurled groove: α = Tangent 1/140 Angle of valley of knurled groove: θ = θ ′ = 57 degrees

When the material of the light guide is acrylic, the critical angle when light travels from acrylic to air is 4
It becomes 2.155 degrees.

As shown in FIG. 10, knurled groove 502
The light striking the side C-D of the light arrives after being repeatedly reflected by the inner wall of the light guide 114-B, the light j that directly arrives without being reflected, and the light that has entered the side A-B of the previous stage. Light k 3
It is a kind. Of these, the light k is very small, and the light that illuminates the sensor is mainly light that has passed through the paths of the light j and the light i.

Next, with the shape of the light guide proposed in the present invention, L
The reason why a smooth light distribution characteristic from the first dot to the Nth dot can be obtained by increasing the amount of light emitted from the light guide member in the portion away from the ED will be described with reference to FIGS. 13 and 14.

FIG. 13 shows the LE of the light guide proposed by the present invention.
It is a figure explaining that light reaches knurl surface Sa of a portion near D, and knurl surface Sb of a portion distant from LED. The surface Sb is the light L5 to L directly arriving from the LED.
6 and the light L7 reflected and arriving at the inner wall 501 of the light guide
~ L8 is received. LED 11 used in the present embodiment
The directional characteristic of 4-A is of a cannonball type as shown in FIG. 14, and 0 degree (optical axis) has the strongest amount of light,
There is light distribution up to about ± 20 degrees. LED like this
By using, all of L5 to L8 described above receive a large amount of LED light. Especially L5-L6
Is light that arrives without being reflected by the inner wall of the light guide, and therefore reaches the surface Sb without loss.

The surface Sa is the light L1 which arrives directly from the LED.
~ L2 and the light L3 which is reflected by the inner wall of the light guide and arrives ~
Receive L4. Considering the directional characteristics of the LED, the light amount decreases as compared with the light reaching the surface Sb.

As described above, by increasing the light received on the knurled surface away from the LED over the light received on the near surface, as a result, from the first dot to the Nth dot as shown in the graph of FIG. Therefore, a smooth light distribution characteristic can be obtained.

Further, in order to increase the reflection efficiency of the entire knurled surface, the length c of the knurled surface is such that the side C-D for directly receiving light is longer than the side D-E (see FIG. 10).

As described above, by illuminating the edge sensor 115 vertically with parallel light having a smooth light distribution characteristic,
Even if the distance between the sheet and the edge sensor 115 varies during the sheet conveyance process, the position detection of the left end of the sheet can be recognized without error. As shown in FIG.
When the standard value of the distance between the edge sensor and the paper is 3 mm, there is no error even if the distance varies with vertical light. However, for example, when the light emitted from the edge sensor has an inclination of 23 degrees, the variation in the distance between the edge sensor and the sheet causes an error in recognizing the left end position.

FIG. 16 is a diagram for explaining the arrangement of the edge sensor 115 for measuring the positional deviation of the left edge of the paper and the position of the recording medium. For example, in the case of an image forming apparatus capable of printing up to A3 size and the reference in the conveyance direction of the recording medium is the central reference, the recording medium of each size is at the position shown in the figure. In order to detect the left edge of each of these sizes, the edge sensor 115 may be arranged at the position shown in the figure. Further, it is preferable to detect the shift amount of the left edge by detecting the front end (for example, 5 mm) of the recording medium as shown in the figure.

FIG. 17 shows a specific example in which the edge sensor 115 is used to detect the left edge shift amount of the recording medium 124 of A3 size. Edge sensor 11
As shown in FIG. 5, light receiving dots 5 are arranged in a direction orthogonal to the transport direction of the recording medium 124 from the first dot. When the recording medium 124 is displaced with respect to the standard position of the left edge (the Mth dot of the edge sensor 115) in the case of A3 size and the edge is detected, the nth dot is the recording medium. When the edge is recognized as the left edge, the shift amount in this case is (M−n) dots. By notifying the video controller 101 of this detection result, the video controller 101 delays the image data output timing from the BD signal by (M-n) dots from the original A3 size paper timing and sends it (see FIG. Corresponding to a time of 9 Tedg).

FIG. 18 is a diagram showing an outline of the edge sensor 115.

As shown in the figure, the light output from the LED 114-A is transmitted through the light guide 114-B and is guided by the light guide 114.
The light is reflected by the knurled surface formed on the upper surface of -B and is uniformly irradiated downward. If there is no recording medium 124,
The light is directly incident on the light receiving dots of the edge sensor 115, and when the recording medium 124 is present, the light is blocked and does not enter the light receiving dots of the edge sensor 115. The light receiving dots are arranged at a pitch of 300 dots / inch, for example. In other words, they are arranged at 0.084 mm pitch,
It has the ability to recognize the left edge of the recording medium 124 at that pitch. The signal 120 output from the edge sensor 115 is as illustrated. The voltage of the incident light-receiving dots rises, and the voltage of the light-receiving dots shielded from light and not incident falls. At the edge, the output signal drops while tilting as shown in the figure.

FIG. 19 shows an edge sensor output signal 120 when the recording medium is plain paper. Further, in the figure, a clock signal SNSCLK and a reset signal SNSRST to be given to the edge sensor 115 are described. Details of these two signals will be described later.

Next, the operation of the drive circuit of the edge sensor 115 will be described with reference to the block diagram of FIG. 20 and the timing chart of FIG. Note that FIG. 20 shows the sensor control unit 400-A and the edge detection unit 400- of FIG.
It is a detailed block diagram about B.

The linear light source 114 always emits the same amount of light irrespective of environmental changes by calibrating the amount of light when the power of the printer is turned on and for each predetermined number of prints. For calibration, first, CPU
LED according to the value set in register 135 by 304
The drive signal generator 130 outputs the signal 118 having a desired pulse width.
Thus, the LED 114-A is turned on with a desired light amount.
Then, the analog voltage of the edge sensor output signal 120 of the edge sensor 115 at that time is converted into an A / D converter 125.
The CPU 304 refers to the value. In this loop, the value set in the register 135 is determined so that the analog output of the edge sensor 115 has a desired value.

When the CPU 304 detects the edge of the recording medium with the edge sensor 115, first, the LED 11
Turn on 4-A. Next, the CPU 304 gives an instruction to the sensor control signal generation unit to cause the edge sensor 11 to operate.
5, SNSCLK signal 119 and SNSRST signal 11
9 is sent out. The edge sensor 115 sends the edge sensor output signal 120 in synchronization with the rising edge of the first SNSCLK signal from the SNSRST signal. The signal 120 is input to the positive input pin of the comparator 127 and is compared with the threshold signal VTH142 to become the binarized signal 140 (see the chart of FIG. 21).

The binarized signal 140 is input to the edge detection unit 128, and when the signal changes from HIGH to LOW, the signal 141 is changed from HIGH to LOW. Once L
The signal 141 that has become OW is held until the SNSRST signal 119 becomes HIGH. The signal 141 is input to the count enable terminal of the counter 129.
That is, the counter 129 controls the edge sensor output signal 12
0 until the left edge of the recording medium is detected.
It continues counting LK119, stops counting up when an edge is recognized, and stores and holds the count value up to that point in the register 133 (see the signal 142 in FIG. 21).

The CPU 304 refers to the held value to detect the position of the left edge of the recording medium. Comparator 12
The threshold value 142 given to the CPU 7 is set by the CPU 304 in the register 13
It is generated by the D / A converter 126 converting the value set to 2 into an analog voltage.

FIG. 22 is a diagram for explaining the sequence from power-on to the end of printing.

When the power is turned on (S1), first the LED1
The light amount of 14-A is automatically adjusted (S2), and further the threshold voltage applied to the comparator 127 is adjusted (S3). In this state, the image forming apparatus is in the standby state,
It waits for a print instruction from the video controller 101.

When the video controller 101 issues a print instruction, printing is started (S4), and the recording medium is fed from the paper cassette (S5). When the TOP sensor on the paper transport path recognizes the leading edge of the recording medium (S6),
After a predetermined time (the time when the position of 5 mm from the leading edge of the paper reaches the edge sensor 115), the positional deviation amount of the left edge of the recording medium is measured (S7), and the deviation amount is notified to the video controller 101 (S8). .

The video controller 101 changes the left margin of the image based on the shift amount (S9), and sends the image data of the first side in order from the C color in synchronization with the TOP signal sent from the engine ( In step S11, the toner is fixed on the recording medium by the fixing device (S12).

In the case of single-sided printing, the standby state is kept as it is, and the print instruction from the video controller 101 is awaited. On the other hand, in the case of double-sided printing, the sheet is re-fed through the double-sided conveyance path (S16). Below, the TO on the paper transport path
It is the same as the first surface from when the P sensor recognizes the leading edge of the recording medium to when the recording medium is fixed. When the power SW is turned off (S15), the process ends.

As described above, according to this embodiment,
Since the edge sensor 115 as the irradiation target or the sheet can be uniformly irradiated, the left edge of the sheet can be detected accurately and the quality of the formed image can be improved.

In this embodiment, the knurled groove 5
Although the width w of 02 is set to a constant width, the width w may be increased as the distance from the LED 114-A is increased to make the light distribution characteristics uniform. In addition, the width u of the opening 506 may be increased as the distance from the LED 114-A is increased, and the light distribution characteristics may be made uniform.

In this embodiment, the image forming apparatus having the four-color photosensitive drums has been described. However, one photosensitive drum is provided and the four-color toner developing devices are sequentially brought into contact with the photosensitive drums. The present invention can be preferably used in an image forming apparatus that forms a color image. Further, it may be used for a monochrome image forming apparatus or an inkjet image forming apparatus.

Further, in the present embodiment, the image data transmission timing is changed according to the shift amount of the left end position of the recording medium. However, the BD signal which is a horizontal synchronizing signal serving as a reference of the image data transmission timing (FIG. 9). Even if the sending timing of (see) is changed, the same function can be realized.

Further, the linear light source 114 may be used as a pre-exposure means for irradiating the photosensitive drum in the electrophotographic recording apparatus. The pre-exposure means is a means for uniformly exposing the photosensitive drum prior to charging to suppress a ghost image.
By using this light source, the surface of the photosensitive drum can be uniformly irradiated with light, so that it is possible to effectively suppress ghost images and improve image quality. When used as the pre-exposure means, the irradiation angle does not necessarily have to be 90 degrees, so that the deflection film may be omitted.

(Second Embodiment) FIGS. 23 and 24
Shows a second embodiment of the present invention. In the first embodiment, the inclination α of the knurled groove was constant, whereas in the present embodiment, the inclination is gradually increased from the end surface on the LED side to the end surface on the opposite side. Increasing the inclination as the distance from the LED 114-A improves the uniformity of the light distribution characteristics.

Since other configurations and operations are the same as those of the first embodiment, the same reference numerals are given to the same components and the description thereof will be omitted.

In the present embodiment, as shown in FIG.
The knurled groove 510 having the inclination α1 in the portion near the LED 114-A is further deepened in the inclination α2 at the portion 508 and further deepened in the inclination α3 at the portion 509. As a result, the reflecting surface of each knurled groove 510 facing the LED 114-A has a knurled groove 5 far from the LED 114-A.
Tens of them are arranged closer to the optical axis of the LED 114-A.

Further, as shown in FIG. 24, since the angles θ and θ ′ of the knurled grooves 510 are substantially the same, 508
Knurled groove 51 closer to the LED 114-A than the part
The length c1 of the knurled surface e of 0 is shorter than the length c2 of the knurled surface d farther from the LED 114-A than the portion 508. In other words, as the distance from the LED 114-A increases, the length of the knurled surface becomes longer (the area of the knurled surface becomes larger), so that uniform light distribution characteristics can be obtained. Since the groove has the same engraving angle as that of the first embodiment, the angle of light emitted from the light guide 114-B is the same as that of the first embodiment.

As a result, also in the structure of the present embodiment, the same effect as that of the first embodiment can be obtained.

In the present embodiment, the knurled groove 5 is used.
Although the gradient of 10 is changed stepwise to α1, further α2, and further α3, it may be continuously changed in a curved shape.

(Third Embodiment) FIGS. 25 and 26.
Shows a third embodiment of the present invention. In the first embodiment described above, the knurled groove has a constant notch depth, whereas in the present embodiment, the LED 114 has the same depth.
The depth z of the knurled groove 511 is increased as the distance from −A increases.

Since other configurations and operations are the same as those of the first embodiment, the same reference numerals are given to the same components and the description thereof will be omitted.

FIG. 26 is an enlarged view of the knurled groove 511. As shown in the figure, when the depth z of the knurled groove 511 is gradually increased, the length of the reflecting surface of the knurled groove 511 is also gradually increased. As a result, the reflective surface of each knurled groove 511 facing the LED 114-A is arranged closer to the optical axis of the LED 114-A as the knurled groove 511 that is farther from the LED 114-A is arranged, and the light distribution is uniform as a whole. The characteristics are obtained.

On the other hand, since the step angles θ and θ ′ are constant angles, the angle of the light reflected by the knurled groove 511 and reflected downward is constant from the first dot to the nth dot of the edge sensor (not shown). Becomes Since the pitch of the step is also constant, the inclination of the waveform at the edge of the paper is also constant. In the case of this example, the ridge portion 512 of the knurled groove 511,
513 has a trapezoidal shape.

As a result, also in the configuration of this embodiment, the same effect as that of the first embodiment can be obtained.

[0088]

As described above, in the linear light source of the present invention, since the reflection surface of the light guide member is arranged closer to the optical axis of the point light source in the groove farther from the point light source, the structure is inexpensive. It is possible to realize a linear light source having a flat light distribution characteristic and a stable directivity and capable of uniformly irradiating an irradiation target.

Further, by combining the linear light source and the light receiving element array of the present invention, it is possible to realize a sheet detecting apparatus capable of accurately detecting the sheet position (for example, the amount of displacement in the sheet width direction).

Further, the sheet detecting apparatus of the present invention is provided, and by determining the image forming timing on the sheet based on the detection result of the sheet detecting apparatus, the desired printing position can be obtained without depending on the sheet conveyance deviation. It is possible to realize an image forming apparatus capable of printing on.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a linear light source according to a first embodiment of the invention.

FIG. 2 is a schematic perspective view showing the structure of the linear light source according to the same embodiment.

FIG. 3 is a schematic diagram of a sheet detection device according to the same embodiment.

FIG. 4 is a graph showing a light distribution characteristic of the linear light source according to the same embodiment.

FIG. 5 is a schematic configuration diagram of a printer engine of the image forming apparatus according to the embodiment.

FIG. 6 is a block diagram of the entire image forming apparatus according to the embodiment.

FIG. 7 is a block diagram of an electric control circuit relating to image generation of the printer engine of the image forming apparatus according to the embodiment.

FIG. 8 is a timing chart of image data in the sheet conveying direction (sub-scanning direction) of the image forming apparatus according to the embodiment.

FIG. 9 is a timing chart of image data in the sheet width direction (main scanning direction) of the image forming apparatus according to the embodiment.

FIG. 10 is an enlarged view of a main part of the linear light source according to the same embodiment.

FIG. 11 is a graph showing the relationship between the surface length of the knurled surface and the amount of reflected light.

FIG. 12 is a graph showing the relationship between the pitch of the knurled groove and the inclination of the sensor output at the edge of the sheet.

FIG. 13 is a diagram illustrating that light reaches the knurled groove of the light guide of the linear light source according to the same embodiment.

FIG. 14 is a graph showing the directivity of LEDs.

FIG. 15 is a graph showing the relationship between the sensor-paper distance and the detected position error.

FIG. 16 is a view for explaining the arrangement of the sheet detection device according to the same embodiment.

FIG. 17 is a diagram illustrating how the left edge of the sheet is displaced.

FIG. 18 is a schematic configuration diagram of a sheet detection device according to the same embodiment.

FIG. 19 is an explanatory diagram showing an example of an output signal of the sheet detection apparatus according to the same embodiment.

FIG. 20 is a block diagram showing a configuration of a sensor control unit of the sheet detection device according to the embodiment.

FIG. 21 is a timing chart of the edge detection unit of the sheet detection apparatus according to the same embodiment.

FIG. 22 is a sequence chart of the image forming apparatus according to the embodiment.

FIG. 23 is a schematic diagram of a linear light source and a sheet detection device according to a second embodiment of the present invention.

FIG. 24 is an enlarged view of a main part of the linear light source according to the same embodiment.

FIG. 25 is a schematic diagram of a linear light source and a sheet detection device according to a third embodiment of the present invention.

FIG. 26 is an enlarged view of a main part of the linear light source according to the same embodiment.

FIG. 27 is a schematic view of a diffuse reflection plate type linear light source according to a conventional technique.

FIG. 28 is a schematic view of a knurled line light source according to a conventional technique.

FIG. 29 is a graph showing a light distribution characteristic of a linear light source according to a conventional technique.

[Explanation of symbols]

101 video controller 102 printer engine 110, 110-K, 110-M, 110-Y, 110
-C image data 111 BD signal 112 TOP signal 113 serial communication line 114 line light source 114-A LED (point light source) 114-B light guide 115 sensor module, edge sensor 116-C, 116-Y, 116-M, 116 -K laser drive circuit 117 TOP sensor 120 edge sensor output signal 124 recording medium (sheet) 127 comparator 130 LED drive signal generation unit 201 paper lateral edge detection means 202 registration roller 203 suction rollers 204 to 207 photosensitive drum 208 electrostatic transport belt 209 supply Paper unit 210 Fixing device 211 Paper discharge roller 212 Double-sided conveyance roller 304 CPU 400-A Sensor control unit 400-B Edge detection unit 501 Inner wall of light guide 502 Knurled groove 503 Deflection film (deflection member) 504 Case (light guide storage) Body) 05 case cover (lightguide storage member) 506 opening 507 LED mounting hole 510 knurls 511 knurls

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G03G 21/00 370 F21Y 101: 02 // F21Y 101: 02 F21S 1/00 FF term (reference) 2F065 AA12 CC02 FF04 FF49 GG04 GG07 GG16 HH13 JJ25 LL28 MM03 QQ08 QQ24 2G051 AA34 AB20 BB17 CA01 DA06 2H027 DC00 DC03 DE02 DE10 2H072 AA09 AA16 AA24 3F048 AA01 AB01 BA05 BB02 CC37 DA06 DC12

Claims (5)

[Claims] 1. A light guide body having a substantially cylindrical light-transmitting property, a light guide body for accommodating the light guide body, and having a slit-shaped opening formed along an axis of the light guide body. A storage body and a point light source that irradiates light to one end surface of the light guide body are provided, and the light emitted from the point light source is reflected in the light guide body to form linear light from the opening. In a line light source that emits light, a plurality of grooves having a reflecting surface that faces the point light source and reflects light from the point light source are arranged in an axial direction on a side surface portion of the light guide opposite to the opening. The line light source, wherein the reflection surface formed and facing the point light source is arranged closer to the optical axis of the point light source in a groove farther from the point light source. 2. The groove is a groove having a triangular cross section formed in a direction orthogonal to the axis of the light guide, and
The line light source according to claim 1, wherein a reflective surface of the groove facing the point light source has a larger area than the other surface. 3. The linear light source according to claim 1, further comprising a deflecting member for refracting the light emitted from the opening so that the light is perpendicular to the object to be irradiated. A linear light source. 4. A linear light source arranged along the width direction of a conveyed sheet and straddling an end portion in the width direction of the sheet, and a plurality of light receiving elements corresponding to linear irradiation light of the linear light source. A light-receiving element array, which detects the widthwise position of a sheet by partially blocking or reflecting a linear irradiation light by the sheet, wherein the linear light source is A sheet detection device, which is the line light source according to. 5. An image forming apparatus comprising: the sheet detecting apparatus according to claim 4; and an image forming unit that determines an image forming timing on a sheet based on a detection result of the sheet detecting apparatus. .