JPH1175035A - Optical scanner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical scanner which reads image information with a high definition signal quality and is inexpensive without providing many photodetectors in the neighborhood of an original. SOLUTION: This device is provided with a laser scanner unit 24 which performs deflection scanning of luminous flux to an original, a photodetector 54 which is made out of an avalanche diode that receives scattered light from the original and performs photoelectric conversion and an amplifier circuit which amplifies an electric signal from the photodetector 54, optically reads image information on the original and controls photoelectric conversion efficiency by changing both or either of the multiplication factor of a signal by the photodetector 54 and the amplification factor of a signal by the amplifier circuit.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scanning optical apparatus applied to a copying machine, a document reading apparatus, and the like, for scanning a document by a light source such as a laser.

[0002]

2. Description of the Related Art Conventionally, in a scanning optical device for reading an image provided in a copying machine or the like, an object to be read such as a print original is placed on an original mounting surface on a flat plate, and the object to be read is placed on the platen. On the other hand, a light beam from a light source is deflected and scanned by a polygon mirror to irradiate the light beam, and the light beam reflected from an object to be read is received by a light receiving means such as a photodetector. Has been obtained image information corresponding to the object to be read.

The original mounting surface is usually formed of a transparent material such as glass, and the light beam is irradiated over the entire area of the original mounting surface. Outside the mounting area, there is nothing to block the light beam, and a light beam with a high energy density may enter the eyes of the user and damage the eyes. For this reason, the emission output of the laser, which is the light source, is limited to a level that is safe even when the light beam enters the eyes of the user.

In order to solve the problem that the light beam may be incident on the user's eyes, a light beam irradiating portion of a document is provided inside the apparatus, and the document is conveyed into the apparatus. An apparatus that prevents the light beam from being emitted to the outside of the apparatus has also been considered.

[0005]

However, in the above-described conventional scanning optical device, the output of the light beam to be incident on the original is limited, so that the reflected light from the original is weak. For this reason, in order to receive the reflected light, it is necessary to arrange a plurality of light receiving elements and a large number of driving circuits near the document, and it has not been possible to provide an apparatus at low cost.

Further, in the above-described conventional apparatus in which the light beam is prevented from being emitted to the outside of the apparatus, it is possible to increase the light output from the original by increasing the light beam. This eliminates the need to arrange a large number of light receiving elements near the document. But,
A high-power laser light source is expensive, and an expensive optical system for condensing the laser light source into a minute beam is required, so that the apparatus cannot be provided at low cost.

Therefore, the present invention has been made to solve the above-mentioned problems, and does not require a high-power laser light source, and even if the reflected light from the original is weak.
It is an object of the present invention to provide an inexpensive scanning optical device capable of reading with high quality signal quality without providing a large number of light receiving elements near a document.

[0008]

In order to achieve this object, a scanning optical apparatus according to the first aspect of the present invention comprises a deflection scanning means for deflecting and scanning a light beam with respect to an original, and a scattered light from the original. Light receiving means for receiving light and photoelectrically converting the light, comprising an electric signal amplifying means for amplifying the electric signal from the light receiving means, for those configured to optically read the image information on the original, In particular, the light receiving unit is configured by an element having a signal multiplying function, and by changing a signal multiplication factor by the light receiving unit, or both or a signal amplification factor by the electric signal amplifying unit, , And is configured to control the photoelectric conversion efficiency.

Therefore, by controlling the photoelectric conversion efficiency by changing the multiplication factor of the signal by the light receiving means and / or the amplification rate of the signal by the electric signal amplifying means, the image information on the document can be obtained. It can be read with high quality.

The scanning optical device according to claim 2 is
The light receiving means is constituted by an avalanche photodiode which is a photoelectric conversion element utilizing electron avalanche multiplication.

Accordingly, since the avalanche photodiode multiplies the signal by the avalanche multiplication, the scattered light from the document can be received with high sensitivity.

The scanning optical device according to claim 3 is
The photoelectric conversion efficiency is changed according to the scanning width of the light beam that scans the original.

Therefore, since the photoelectric conversion efficiency is changed in accordance with the scanning width of the light beam that scans the original, image information can always be read with high quality regardless of the length of the original.

[0014] Further, the scanning optical device according to claim 4 is
The photoelectric conversion efficiency is changed according to the reflectance of the document.

Therefore, since the photoelectric conversion efficiency is changed in accordance with the reflectance of the document, even when a document having a different reflectance is read, image information can always be read with high quality.

The scanning optical device according to claim 5 is
The deflection scanning unit is configured to perform a first scan for obtaining a reflectance of the document and a second scan for reading image information on the document.

Therefore, the deflection scanning means can obtain the reflectance of the original document by the first scanning and can set the photoelectric conversion efficiency optimally according to the reflectance. Image information can be read with high quality.

The scanning optical device according to claim 6 is
By changing the bias voltage applied to the light receiving means, the multiplication factor of the light receiving means is controlled.

Therefore, by changing the bias voltage applied to the light receiving means, the multiplication factor of the light receiving means can be reliably controlled.

Further, the scanning optical device according to claim 7 is
Temperature detection means for detecting the temperature of the light receiving means,
The bias voltage applied to the light receiving means is changed based on the detection result of the temperature detecting means.

Therefore, when the temperature detecting means detects the temperature, the bias voltage applied to the light receiving means is changed based on the detection result, so that the photoelectric conversion is always performed at an optimum multiplication factor regardless of the temperature change. It can be carried out.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view showing a schematic configuration of a laser copying apparatus 1 provided with a scanning optical device according to an embodiment of the present invention.

In FIG. 1, a laser copying apparatus 1 includes a main body case 2, a document placing portion 5 for placing a document,
A sheet feeder unit 10 for feeding a sheet P as an example of a recording medium for image formation, a latent image forming unit 20 in which reading, charging, exposure, and the like of a document image for image formation are sequentially performed; A developing unit 70 for visualizing the latent image formed by the latent image forming unit 20 with a developer, and a transfer unit for transferring a developing material image developed by the developing unit 70 to a sheet P 71, a fixing unit 72 for fixing the transfer image transferred by the transfer unit 71 to the sheet P, and a discharge tray 73 for discharging the sheet P on which the image is fixed along the transport path PP. It is provided with.

The latent image forming section 20 includes a photosensitive drum 21 as an example of a photosensitive member, a charge removing lamp 22 for removing a residual potential remaining on the photosensitive drum 21 after transfer, and
A blade cleaner 23 for removing toner adhering to the photoreceptor, a laser scanner unit 24 for scanning and reading a document image and performing exposure for forming an electrostatic latent image on the photoreceptor drum 21; Body drum 21
, And a charger 25 for charging the electrostatic latent image to form an electrostatic latent image.

The original placing section 5 includes an original placing plate 3 made of a transparent material such as glass for placing an original, and a holding lid 4 as a lid member for covering the original placing plate. The holding lid 4 is provided to be openable and closable by a hinge or the like (not shown) on the back side in FIG. Further, the document placing section 5 can place a document by a horizontal driving mechanism (not shown) and can be driven in a horizontal direction to a point indicated by a two-dot chain line on the left side in the figure.

Next, each component constituting the laser copying apparatus 1 will be described in detail.

In FIG. 1, the paper feeder unit 10 includes a paper cassette 11 which is detachably disposed at a lower portion of the main body case 2, and the paper P is provided on the bottom of the paper cassette 11 in an upward direction. An urging sheet pressing plate 12 is provided. A paper feed roller 13 extending from the front side to the back side in FIG. 1 is formed above the paper feed cassette 11 so as to contact the paper P urged by the paper pressing plate 12. The paper feed roller 13 is rotatably supported, and its paper feed roller 13 is configured to be driven to rotate at a predetermined paper feed timing by a drive system (not shown). Therefore, the sheets P stored in the sheet cassette 11 are fed one by one from the upper side. In order to prevent double feeding of the paper P, a separating member elastically biased to the paper feed roller 13 by a compression spring may be provided below the paper feed roller 13. Further, a pair of transport rollers 14 for transporting the paper P and a pair of registration rollers 15 for aligning the leading end of the fed paper P are rotatable downstream of the feed roller 13 in the transport direction. Each is pivoted.

Next, the photosensitive drum 21 as an example of the photosensitive member provided in the latent image forming section 20 is made of, for example, an organic photosensitive member mainly composed of positively charged polycarbonate. More specifically, the photoreceptor drum 21 has, for example, a cylindrical aluminum sleeve as a main body and a predetermined thickness (for example, about 20 μm) in which a photoconductive resin is dispersed in polycarbonate on the outer periphery thereof. And is rotatably supported by the main body case 2 with the cylindrical sleeve installed. In other words, the positively charged (positively charged) electrostatic latent image formed on the photosensitive drum 21 is developed by the reversal developing method with the positively charged toner. The photosensitive drum 20 is configured to be driven to rotate clockwise in a side view by a driving unit (not shown).

The static elimination lamp 22 includes a light source such as an LED (light emitting diode), EL (Electro Luminescence), and a fluorescent lamp, and irradiates light remaining on the photosensitive drum 21 with light after transfer. It is removed (discharged) by the fact. Thus, it is possible to prevent the remaining charge from affecting the next electrostatic latent image and finally appearing on the image formed on the sheet P.

The blade cleaner 23 makes the elastic rubber contact the photosensitive drum 21 directly, and
The remaining untransferred residual toner is scraped off,
This residual toner is prevented from causing image defects in the next exposure cycle.

The charger 25 is composed of a scorotron-type charger for positive charging that generates corona discharge from a charging wire made of, for example, tungsten.

The laser scanner unit 24 is disposed above the photosensitive drum 21 and has the following configuration. As shown in FIG. 2, a scanner frame 26 of the laser scanner unit 24 includes a red semiconductor laser unit 30 including a red semiconductor laser 27 serving as a reading light source and an infrared laser including an infrared light laser 31 serving as a recording light source. An optical laser unit 34 is provided. In this embodiment, a red semiconductor laser 27 is used as a reading light source.
Has a wavelength of 650 nm, but a green or blue laser having a wavelength of 400 to 700 nm may be used in the visible region. As a light source for recording,
It is desirable to use a wavelength of 780 nm from the viewpoints of cost and photoconductor sensitivity, but it is also possible to focus the beam diameter on the photoconductor more minutely by using a shorter wavelength light source. .

The optical axis of the red semiconductor laser 27 serving as the reading laser is aligned with the infrared laser 31 serving as the recording laser.
It is arranged so that it is almost perpendicular to the optical axis of
A dichroic mirror 43 that transmits or reflects light of a specific wavelength is provided at the intersection of each optical axis.

A dichroic mirror 4 on which an infrared light beam IR for recording and a red light beam R for reading are incident.
Reference numeral 3 has a characteristic of reflecting the infrared light beam IR and transmitting the red light beam R, and these beams have the same optical path.

That is, the red light beam R is incident on the dichroic mirror 43 via the collimator lens 28 for making the light flux substantially parallel and the diaphragm 29 for making the spot diameter a predetermined size.
And reaches the cylindrical lens 46. The recording infrared light beam IR is incident on a dichroic mirror 43 via a collimator lens 32 for making the light flux substantially parallel and a stop 33 for making the spot diameter a predetermined size. 43
And reaches the cylindrical lens 46 along the same optical path as the red light beam R.

The cylindrical lens 46 is a lens that focuses a light beam only in one direction, and the respective light beams serve as polarizers disposed at the focal position of the cylindrical lens 46 via the cylindrical lens 46. Into the regular hexagonal polygon mirror 47. When the polygon mirror 47 rotates at a constant speed, the polygon mirror 47 is rotated.
2 is scanned at a constant speed in a direction parallel to the plane of FIG. 2 and condensed by an imaging lens 48 as a condensing means. In addition, the light is directed by the reflection mirror 50.

The dichroic mirror 49 and the reflection mirror 50 are provided in front of the imaging lens 48, as shown in FIG. And dichroic mirror 4
Reference numeral 9 reflects an infrared light beam IR for recording or the like, transmits a red light beam R for reading, and irradiates the original 6 on the document table 3 with a light beam for reading. The reflection mirror 50 irradiates the photosensitive drum 21 with the recording infrared light beam IR transmitted through the dichroic mirror 49.

As shown in FIG. 2, a BD mirror 51 for reflecting a recording light beam emitted from the semiconductor laser 31 is provided at a position in the scanner frame 26 corresponding to a position outside the irradiation range of the photosensitive drum 21. And B for detecting a light beam reflected by the BD mirror 51 and forming a horizontal synchronization signal.
A D sensor 52 is provided.

As shown in FIGS. 1 and 3, a light detecting lens 53 for detecting a light beam scattered and reflected by the original 6 is provided at a position opposed to the original 6 with the original table 3 interposed therebetween.
Further, a photodetector 54 composed of an avalanche photodiode, which is a well-known photoelectric conversion element, is disposed at a substantially central position in the scanning direction of the light beam. Note that this photodetector 54
Is not limited to one, but may be plural (for example, two or three), and respective signals may be added. However, since the avalanche photodiode has a very high sensitivity, it is sufficient to use at most a few photodetectors 54. Incidentally, the photodetector 54 constitutes the light receiving means of the present invention.

The position of the document table 3, that is, the mounting surface of the document 6, is set to coincide with the focal position of the imaging lens 48, and is set to a position optically conjugate with the position of the photosensitive drum 21. Therefore, the spot diameter of the light beam that scans on the photosensitive drum 21 is equal to the spot diameter that scans on the document 53. Therefore, the accuracy at the time of document recording and the accuracy at the time of image reading become equal, and the image on the document 6 can be faithfully reproduced on the photosensitive drum 21.

An avalanche photodiode is a semiconductor detecting element having a function of multiplying a signal therein. A high voltage is applied to a depletion layer region inside the avalanche photodiode to cause avalanche multiplication, and one light particle is generated. , One or more signal charges are output. The multiplication factor of the avalanche photodiode changes depending on the ambient temperature and the electric field (bias voltage) applied to the depletion layer. For example, the multiplication factor at a constant bias voltage decreases as the temperature increases, and the multiplication factor increases as the bias voltage increases. It has the property of being high. Incidentally, the bias voltage is set to about 150 to 200 V in a general element.

Next, the electrical circuit configuration of each part of the laser copying apparatus 1 will be described with reference to FIGS.

As shown in FIG. 4, the image reading section includes a photodetector 54, an amplification circuit 60, a temperature detection section 63,
The PU 64 and the voltage control circuit 62 are connected to each other. The amplifier circuit 60 constitutes an electric signal amplifier, and the temperature detector 63 constitutes a temperature detector.

When the photodetector 54 receives the scattered light from the document, it performs photoelectric conversion and inputs an electric signal to the amplifier circuit 60. After being further electrically amplified by the amplifier circuit 60, A /
The CPU converts the signal strength into digital data in the D conversion unit 61.
64, and the CPU 64 stores it in the memory 65.

The voltage control circuit 62 has, for example, a configuration as shown in FIG. In accordance with the control signal from the CPU 64, 170V, which is the bias voltage of the photodetector 54, is obtained from the power supply voltage of 200V, and the reference voltage to the + input of the operational amplifier can be changed to about ± 20V by changing the reference voltage. it can. Also, since the bias voltage is monitored and controlled by feeding back to the operational amplifier, the bias voltage is always kept at the set value. That is, in order to increase the multiplication factor of the photodetector 54, the CP
An instruction may be sent from U64 to increase the bias voltage.

The temperature detector 63 measures the temperature of the photodetector 54 using a temperature detecting element such as a thermistor in order to measure the temperature of the photodetector 54. CPU
64 instructs the voltage control circuit 62 to increase the bias voltage when the temperature of the photodetector 54 increases, and keeps the multiplication factor constant.

The amplifier circuit 60 has, for example, a configuration as shown in FIG. The electric signal after photoelectric conversion output from the photodetector 54 is input to the input terminal, and is amplified and output from the output terminal. Amplification rate is CPU6
4 can be arbitrarily set by changing the control signal from 4 to an analog voltage value by a D / A converter and changing the bias voltage of the amplifier (transistor).

When reading and copying various originals, it may be convenient to change the photoelectric conversion efficiency according to the originals. For example, if the photoelectric conversion efficiency is set to be optimal for reading black characters on a white background document, when reading characters printed on paper such as gray,
The contrast between the character portion and the paper portion is hard to be obtained, and the reading accuracy is deteriorated. Thus, by increasing the photoelectric conversion efficiency, it is possible to read the character portion with the character portion highlighted. The photoelectric conversion efficiency represents the intensity of the electric signal output from the electric signal amplifying means with respect to the amount of light input to the light receiving means. In the present embodiment, the multiplication factor of the photodetector 54 and the amplification circuit 60 And the amplification factor.

Similarly, when reading a glossy and high-reflectivity document such as a photograph, the photoelectric conversion efficiency in reading a normal document reflects light from a black portion to some extent. The result may be whitish as a whole, or, in some cases, the signal may be saturated in the amplifying unit at the subsequent stage and may not operate. Therefore, by setting the photoelectric conversion efficiency lower than that of a normal document, the above-described problem can be avoided.

Further, even when the reading width of the document is different, it is convenient to change the photoelectric conversion efficiency. FIG. 7 shows the distribution of scattered light when a document having a uniform density is read by one light receiving element when the reading width of the document is short and long. According to this, when the document width is long, the difference in signal level depending on the scanning position, for example, at the center and both ends, is larger than when the document width is short (shading). For this reason, it is necessary to perform correction for matching a low signal level portion with a high signal portion. This correction is performed by inputting the received light signal to the A / D converter, storing the obtained digital value of the received light signal intensity in a memory as a reference level, and comparing and reading the image information when reading image information from a document. General. However, when this correction is performed, a dynamic range cannot be obtained in a portion where the signal level is low, so it is disadvantageous to identify the density of the document with gradation, and a high-quality image can be read over the entire document. It becomes difficult.

For this reason, when the document width is long, the photoelectric conversion efficiency is set higher than usual and the overall signal level is raised, so that the signal levels at both ends of the document can be identified with gradation. It is possible to raise to. In order to change the photoelectric conversion efficiency, when an avalanche photodiode is used as the photodetector 54, it can be realized by changing the multiplication factor of the element itself, and further provided immediately after the light receiving element. Fine adjustment can be performed by adjusting the gain of the amplified circuit.

In this embodiment, in order to change the photoelectric conversion efficiency as described above, the control signal from the CPU 64 controls the bias voltage of the photodetector 54 and / or the amplification factor of the amplifier circuit 60. Can be set arbitrarily.

Next, the developing unit 70 driven after the above-described image reading and exposure corresponding thereto are performed.
Will be described.

As shown in FIG. 1, the developing section 70 is disposed close to the photosensitive drum 21. Although not shown in detail below, the developing section 70 supplies a developing roller and a developing voltage. Power supply, toner box, etc. In this toner box, positively charged toner is stored together with a magnetic carrier, and supplies toner to the developing roller. The toner in the present embodiment is a positively charged toner, for example, a non-magnetic toner composed of a pulverized toner or a polymerized toner composed of styrene-acryl having a pearl-like shape, and a coloring agent such as a pigment and a polyester resin. It is configured to include a binder resin. As a result, most of the toner is rubbed by the developing roller, the photosensitive drum 21 and the like, and is charged to a positive (positive) polarity.

Next, a transfer unit 71 is disposed downstream of the contact portion between the developing unit 70 and the photosensitive drum 21 in the moving direction of the photosensitive drum 21 as described above. Transfer unit 7
Like the charger 25, the charger 1 includes a scorotron-type transfer charger for positive charging for generating corona discharge from a charging wire made of, for example, tungsten or the like, and a separation charger.

A fixing section 72 is provided downstream of the separation charger in the sheet conveying direction. The fixing unit 72 includes a heating roller including a well-known halogen lamp and a pressing roller. The toner image transferred onto the upper surface of the sheet P is pressed while being heated and is fixed on the sheet P.

Further, a pair of transport rollers for transporting the paper, downstream of the fixing unit 72 in the transport direction of the paper P,
A paper discharge tray 73 is provided, and the paper P discharged from the fixing unit 72 is guided to the outside of the copier and placed thereon.

Next, the operation of the laser copying apparatus 1 configured as described above will be described with reference to the drawings.

First, the user places the original 6 on the original placing plate 3.
Is placed, the cover 4 is closed, the size of the document is specified on an operation panel (not shown) provided on the upper surface of the laser copying apparatus 1, and the type of the document is selected from the classification corresponding to the reflectance. Then, the operation is started by pressing the copy start key.

The CPU 64 determines the multiplication factor of the avalanche photodiode as the photodetector 54 and the amplification factor of the amplifier circuit 60 based on the designated original size and original type. These are performed by referring to the setting table stored in the memory 65. For example, when the document size is set to "A4 size" and the document type is set to "photo", the corresponding multiplication factor and amplification factor are read from the setting table. As mentioned earlier, the CPU
64 instructs the voltage control circuit 62 to change the bias voltage in order to change the multiplication factor of the photodetector 54;
Further, a control signal is sent to the amplifier circuit 60 in order to change the amplification factor of the amplifier circuit 60.

Next, the red semiconductor laser 27 emits light,
The red light beam R is irradiated and scanned from the laser scanner unit 24 onto a white plate (which uniformly develops white) (not shown). Then, the reflected light from the white plate is detected by the photodetector 54, and the reflected light level at each scanning position is recorded in a memory as a reference of the white level, and so-called white level setting is performed.

When the white level is set, first, the red semiconductor laser 27 emits light and the dichroic mirror 4
3. By operation of the polygon mirror 47, the imaging lens 48 and the dichroic mirror 49, the red light beam R is irradiated on the surface of the document 6. The emission timing of the red semiconductor laser 27 is controlled by making the infrared light beam IR incident on the BD sensor 52 as described later.

Next, when the reflected light from the original 6 in response to the light beam irradiation as described above is detected by the photodetector 54, this detection signal is amplified by the amplifier 60,
The voltage amplitude is converted into a digital value by the D conversion section 61 and the CPU 6
4 is input. The CPU 64 calculates, based on the amount of attenuation of the detection signal with respect to a reference white level obtained by the white level setting,
For each dot corresponding to one dot in image recording, the reflected light amount difference (density difference) with respect to the white level is recorded in the memory 65. For example, when recording the reflected light amount difference with an accuracy of 1/256 of the white level, a memory capacity of 1 byte is required for each dot. However, since the reading operation and the writing operation are performed almost simultaneously, the memory capacity for image recording may be one or two dots.

The temperature detecting section composed of a thermistor circuit always detects the temperature of the photodetector 54 and inputs the detected temperature to the CPU 64. The CPU 64 instructs the voltage control circuit 62 to increase the bias voltage when the temperature increases in response to the temperature change of the photodetector 54, and instructs the voltage control circuit 62 to decrease the bias voltage when the temperature decreases. ing. Since this operation is performed in real time, the photoelectric conversion efficiency of the photodetector 54 is always maintained at the photoelectric conversion efficiency set based on the document size and type.

Then, the CPU 64 outputs a modulation signal of the recording infrared light laser based on the image information stored in the memory by the above processing, and outputs the recording infrared light semiconductor according to the signal. Infrared light beam I by laser
Irradiation of R is performed, and the light beam IR is reflected toward the photosensitive drum 21 by a dichroic mirror, a polygon mirror, and a reflecting mirror, and scans the surface of the photosensitive drum 21.

FIG. 8 shows the operation timing of the reading semiconductor laser and the recording semiconductor laser. As shown in FIG. 8, the recording semiconductor laser is turned on at time Tp before the light beam enters the BD sensor 52. At this time, the reading semiconductor laser (for example, the red semiconductor laser 27) is turned off in order to increase the timing accuracy. With the rotation of the polygon mirror 47, the light beam from the recording semiconductor laser enters the BD sensor 52 and
When the D signal is detected, the reference time To for one scan is set, and the recording semiconductor laser is turned off once. However, after turning off the light, the reading semiconductor laser is turned on at a time Trs after a lapse of a predetermined time, and similarly, the recording semiconductor laser is turned on. Time T elapsed
In s, the recording semiconductor laser is modulated and driven according to the image information stored in the memory as described above. Here, time T
The relationship between rs and Ts is a time including a delay until a read signal obtained by the photodetector is input to the modulation circuit and the recording semiconductor laser is modulated. Thereafter, at times Tre and Te corresponding to the scanning of the image area (for example, 210 mm, which is the width in the A4 lateral direction), the reading semiconductor laser is turned off. Then, this operation is repeated every scanning.

On the other hand, prior to the irradiation of the recording light beam L, at a predetermined timing, the discharge lamp 2
After the residual charge on the photoconductor drum 21 is wiped out by the photoconductor 2, the surface of the photoconductor drum 21 is
As a result, it is uniformly charged to a predetermined potential. In this state,
The recording light beam IR irradiated as described above is irradiated on the photosensitive drum 21, and an electrostatic latent image corresponding to the image read by the red light beam is formed on the photosensitive drum 21.

Such processing is performed in the main scanning direction.
When the scanning is performed for the scanning lines, the original placing unit 5 is transported by one dot by a driving mechanism (not shown) that transports the original placing unit 5 in the sub-scanning direction (the direction of the two-dot chain line in the figure). It is driven to rotate. These operations are performed in the sub-scanning direction of the document (for example, about 30
0 mm), the exposure operation for reading and copying the entire document is completed.

The developing operation by the developing device is performed simultaneously with the above-described exposure operation. The toner in the developing device is charged to a positive polarity by friction charging with a magnetic carrier or the like, and the toner charged to the positive polarity is formed on a developing roller on a brush, and the developing roller contacts the photosensitive drum 21. Conveyed to the contact position, and adheres to the electrostatic latent image formed so as to have a predetermined potential difference from the developing roller on the photosensitive drum 21 by the infrared light beam IR,
Development takes place. As a result, on the photosensitive drum 21,
A toner image is formed, and the toner image is transferred by a transfer charger onto a sheet of paper P conveyed synchronously by a registration roller 14, and then is transferred to a photosensitive drum 2 by a separation charger.
The sheet P is separated from the sheet P, is subjected to a fixing process by a heating roller and a pressing roller of the fixing unit 72, and is discharged to a discharge tray after fixing.

A dichroic mirror for separating a recording light beam and a reading light beam has a spectral reflection characteristic as shown in FIG. FIG. 9 shows the wavelength on the horizontal axis and the reflectance on the vertical axis. Assuming that the wavelength of the light beam emitted by the semiconductor laser for reading is λ1 and the wavelength of the light beam emitted by the semiconductor laser for recording is λ2 longer than λ1, the dichroic mirror has a reflectance R1 for the wavelength λ1, and the wavelength λ
For 2, R2 is smaller than R1. When the extinction ratio is used as an index indicating the wavelength separation characteristics of the dichroic mirror, R1 / R2 is the extinction ratio in this case. For example, when recording an image and reading an image at the same time, if the efficiency of separating the optical path by the dichroic mirror is low, the reading light flux becomes stray light and acts on the photosensitive drum 21 as bias light, and is applied to the printed image. It may have an adverse effect as dirt.

Therefore, for example, when reading an image,
The irradiation light amount is set to 1 mW, and the photosensitive drum 2 is used for recording.
Assuming that the amount of light irradiated to 1 is 100 μW, the modulation degree, which is the ratio when the amount of light is turned on and off during recording, needs to be about 100 times. Therefore, the amount of light allowed as a bias on the photosensitive drum 21 is 1 μW. Therefore, it is desirable that the extinction ratio of the dichroic mirror is at least 1/1000.

The dichroic mirror as the synthesizing means determines the efficiency from the light source, and does not require an extinction ratio as high as that of the dichroic mirror as the separating means. Of course, it is conceivable to use the same component having the same extinction ratio to increase the efficiency, but from the viewpoint of cost, it is more advantageous to use a half mirror that is a metal single-layer film rather than to use a dichroic mirror. is there.

Next, the operation of the second embodiment of the present invention will be described.

The user places the original 6 on the original placing plate 3, closes the holding cover 4, and specifies the size of the original on a panel (not shown) provided on the upper surface of the laser copying apparatus 1. Thereafter, the operation is started by pressing the copy start key.

First, the red semiconductor laser 27 emits light,
The red light beam R is irradiated and scanned from the laser scanner unit 24 onto the document 6 surface. When the reflected light from the document 6 with respect to the irradiation of the light beam is detected by the photodetector 54,
After the detection signal is amplified by the amplifier circuit 60, the voltage amplitude is digitized by the A / D converter 61, input to the CPU 64, and stored in the memory 65. This is performed on the entire surface of the document, similarly to the reading operation of the first embodiment. The CPU refers to the setting table stored in the memory based on the distribution of the reflected light of the entire original document obtained by these operations and the information of the original size specified by the user, and the photodetector 54 A multiplication factor of an avalanche photodiode and an amplification factor of the amplifier circuit 60 are determined. For example, when the variation in the reflected light of the entire document is large, the photoelectric conversion efficiency (that is, the product of the multiplication factor and the amplification factor) is set to be relatively low, while when the variation is small, the photoelectric conversion efficiency is increased. It is set. Thereafter, the same reading and writing operations as in the first embodiment are performed.

The present invention is not limited to the embodiment described in detail above, and various changes can be made without departing from the gist of the present invention.

For example, in the above-described embodiment, only the formation of a monochrome image has been described, but a configuration in which a color image can be formed may be adopted. In this case, a laser beam of three colors of R, G, and B is provided as a semiconductor laser for reading, and the document can be read in color by scanning the document three times with the laser scanner unit 24. Furthermore, cyan, which is a well-known method for recording,
A color image can be copied by mounting a developing unit including magenta, yellow, or black toner and operating a color image based on image information obtained by the reading mechanism.

Further, in the above embodiment, the configuration is such that the user specifies the size of the original on the operation panel.
It is also possible to arrange a document size sensor in which a light emitting element and a light receiving element are paired in the vicinity of the document placing portion so as to automatically recognize the document size.

Further, in the above-described embodiment, an example was described in which an OPC photosensitive member (organic photosensitive member) was used as the photosensitive member. However, the present invention is not limited to this. Alternatively, a sheet-like photoconductor in which aluminum is deposited as a conductive layer on a polyester film may be used, and the relative movement directions of the photoconductor and the developing roller may be opposite or the same or both.

In the above embodiment, the photodetector 54
Although an avalanche photodiode was used as a light receiving element, the present invention is not limited to this as long as the light receiving element has a signal multiplication function.

Further, in the above-described embodiment, the laser copying apparatus and the multifunctional peripheral apparatus have been described. However, the invention can be applied to a single reading scanner apparatus.

[0083]

As is apparent from the above description,
In the scanning optical device according to the first aspect of the present invention, the light receiving unit is configured by an element having a signal multiplying function, and a signal multiplication factor by the light receiving unit or a signal amplification by the electric signal amplifying unit. It is configured to control the photoelectric conversion efficiency by changing both or any of the ratios, so that the photoelectric conversion efficiency can be freely controlled to always read the image information on the document with high quality. it can.

The scanning optical device according to claim 2 is
Since the light receiving means is constituted by an avalanche photodiode which is a photoelectric conversion element utilizing electron avalanche multiplication, the avalanche photodiode multiplies a signal by electron avalanche multiplication, so that even a weak light has high sensitivity. The number of light receiving means and the number of amplifier circuits can be reduced.

The scanning optical device according to claim 3 is
Since the photoelectric conversion efficiency is changed according to the scanning width of the light beam that scans the original, even if the original width is long, a high-quality image can be read over the entire original with a small number of light receiving units. Thus, image information can always be read with high quality regardless of the width of the document to be read.

The scanning optical device according to claim 4 is
Since the photoelectric conversion efficiency is changed in accordance with the reflectance of the document, high-quality image information can always be read regardless of the type of the document.

The scanning optical device according to claim 5 is
Since the deflection scanning unit is configured to perform a first scan for obtaining the reflectance of the document and a second scan for reading image information on the document, the reflectance of the document is Without the need for special equipment to obtain
Further, even when a user reads a document having a different reflectance without designating the type of the document, the image information can always be read with high quality.

The scanning optical device according to claim 6 is
Since the multiplication factor of the light receiving means is controlled by changing the bias voltage applied to the light receiving means, the multiplication factor of the light receiving means can be reliably controlled.

The scanning optical device according to claim 7 is
Temperature detection means for detecting the temperature of the light receiving means,
Since the bias voltage applied to the light receiving means is configured to be changed based on the detection result of the temperature detecting means, the photoelectric conversion can always be performed at an optimum multiplication factor regardless of the temperature change, There is no need to add a means for keeping the temperature constant by a Peltier element or the like.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a schematic configuration of a laser copying apparatus provided with a scanning optical device according to an embodiment of the present invention.

FIG. 2 is a plan view illustrating a schematic configuration of a laser scanner unit.

FIG. 3 is a side view illustrating a schematic configuration of a laser scanner unit.

FIG. 4 is a block diagram illustrating an electric circuit configuration of a reading unit of the scanning optical device.

FIG. 5 is an electric circuit diagram of a voltage control circuit.

FIG. 6 is an electric circuit diagram of the amplifier circuit.

FIG. 7 is a graph showing the relationship between the length of a document width and the amount of light.

FIG. 8 is a timing chart showing a reading operation and a recording operation of the laser scanner unit.

FIG. 9 is a characteristic diagram illustrating a spectral reflection characteristic of a dichroic mirror.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 laser copy device 3 document placing plate 4 holding lid 11 paper feed cassette 20 latent image forming unit 21 photosensitive drum 24 laser scanner unit 30 red semiconductor laser unit 34 infrared semiconductor laser unit 47 polygon mirror 48 imaging lens 49 dichroic Mirror 50 reflecting mirror 53 photodetection lens 54 photodetector

Claims (7)

[Claims] 1. A deflection scanning means for deflecting and scanning a light beam on a document, a light receiving means for receiving scattered light from the document and performing photoelectric conversion, and an electric signal amplifying means for amplifying an electric signal from the light receiving means. A scanning optical apparatus configured to optically read image information on the document, wherein the light receiving unit is configured by an element having a signal multiplying function, Alternatively, the scanning optical device is configured to control the photoelectric conversion efficiency by changing both or any of the amplification factors of the signal by the electric signal amplification unit. 2. The scanning optical apparatus according to claim 1, wherein said light receiving means is constituted by an avalanche photodiode which is a photoelectric conversion element utilizing electron avalanche multiplication. 3. The scanning optical device according to claim 1, wherein a photoelectric conversion efficiency is changed according to a scanning width of a light beam scanning the original. 4. The scanning optical device according to claim 1, wherein the photoelectric conversion efficiency is changed according to the reflectance of the document. 5. The apparatus according to claim 1, wherein the deflection scanning unit is configured to perform a first scan for obtaining a reflectance of the document and a second scan for reading image information on the document. The scanning optical device according to claim 4, wherein 6. The scanning device according to claim 1, wherein a bias voltage applied to said light receiving means is changed to control a multiplication factor of said light receiving means. Optical device. 7. A temperature detecting means for detecting a temperature of said light receiving means, and wherein a bias voltage applied to said light receiving means is changed based on a detection result of said temperature detecting means. The scanning optical device according to claim 6.