JP2003182140A - Imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable imaging without causing a light source failure or great deterioration of the image quality even when a quantity of light of a part of light beams cannot be detected. <P>SOLUTION: In an APC quantity of light control mode, a level of a driving amount control signal to be outputted to an LD array driving part 92 is controlled by an amplifier 120 and a sample hold circuit 122 to make a laser beam light intensity detection value (quantity of light signal) agree with a set value (quantity of light set signal). When the level of the driving amount control signal exceeds an upper limit of a driving amount control range by the reason that the laser beams do not enter a light intensity sensor, or the like, the control mode is switched to a forced control mode because outputs of a comparator 128 and an OR circuit 126 are changed over. Laser beams are forcibly turned to a predetermined quantity of light by outputting as the driving amount control signal, a forced driving amount set signal of a level corresponding to a median value of the driving amount control range via a mode change means 124. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus, and more particularly, it forms an image on an object to be scanned by scanning a plurality of light beams emitted from a plurality of light sources on the object to be scanned. The present invention relates to an image forming apparatus.

[0002]

2. Description of the Related Art As a light beam scanning device of an image forming apparatus, a plurality of light beams are respectively deflected and simultaneously scanned on an object to be scanned, such as a photoconductor, to scan a plurality of scanning lines in one main scan. A structure for forming an image by performing scanning is conventionally known, and a surface emitting laser (VCSE) that can be easily arrayed is formed.
L: Vertical Cavity Emitting Laser) is used as a light source, and the number of light beams to be simultaneously scanned (the number of scanning lines simultaneously scanned by the light beam) is increased to realize a high image forming speed. It has been proposed (see, for example, Japanese Patent Laid-Open No. 5-294005).

As described above, when a plurality of scanning lines are simultaneously scanned by a plurality of light beams to form an image, variations in the light amount of the individual light beams are visually recognized as density unevenness on the image. The amount of current or voltage supplied to the light source that emits each light beam so that the light amount of each light beam is detected and is constant, (hereinafter these are collectively referred to as the laser drive amount). Light intensity control (also referred to as APC) for controlling

Here, the edge emitting laser, which is widely used as a light source of a light beam scanning device, emits a light beam called a back beam from the opposite side in addition to the main light beam emitted from the front side. Therefore, this back beam can be used for light amount detection. Generally, in the edge-emitting laser, the edge-emitting laser and an optical sensor for detecting the light amount of the back beam are modularized as a single package, so that the light amount of the light beam can be detected reliably and accurately.

[0005]

However, the surface emitting laser has a structure in which the back beam is not emitted. Therefore, when the surface emitting laser is used as the light source of the light beam scanning device, for example, Japanese Patent Application Laid-Open No. 4-355986.
As described in Japanese Patent Publication, a part of a main light beam emitted from a light source and made into a parallel light flux by a collimator lens is reflected by a half mirror, condensed by a lens and made incident on an optical sensor. It is necessary to detect the amount of light. However, in the above detection method, there are many optical components on the optical path from the light source to the optical sensor, and it is difficult to arrange them all in a single package as in the case of an edge-emitting laser.

Therefore, when the surface emitting laser is used as the light source of the light beam scanning device, the optical components such as the half mirror and the optical sensor are arranged in the casing of the optical scanning device as a package separate from the light source and the like. However, because the optical path length from the laser light source to the optical sensor is relatively long, high precision is required for the arrangement of the above optical components, and in particular, a surface-emitting laser is arrayed so that multiple light beams can be emitted. In a mode in which the surface emitting laser array configured as described above is used as a light source, for example, in a situation where each optical component is temporarily assembled at the time of assembling the light beam scanning device, the light emitted from the light source is caused by the optical axis shift of the optical component. In many cases, all or part of the beam is not incident on the optical sensor, that is, the light amount detection by the optical sensor is impossible or inaccurate.

For example, when adjusting the arrangement position of the optical components, it is necessary to emit a light beam from a light source, for example, for recording a test pattern image on a sheet for confirmation, but the light beam emitted from the light source is required. When the light amount control (APC) is performed in a state where all or part of the light does not enter the optical sensor, the light amount detection value for the light beam that does not enter the optical sensor becomes 0 or a value significantly smaller than the actual light amount. As a result of driving the light source with an excessive amount of laser drive,
There is a risk that the light source will break down or that it will significantly deteriorate. For this reason, it is required to enable the emission of a light beam (formation of an image) from the light source while preventing the failure of the light source and the occurrence of remarkable deterioration.

The state in which all or part of the light beam emitted from the light source does not enter the optical sensor is not only when the light beam scanning device is assembled, but also when the casing of the light beam scanning device is impacted from the outside. It may occur even when the arrangement position of the optical component is displaced. Even in such a case, it is possible to maintain the state in which an image can be formed while preventing the failure of the light source and the occurrence of remarkable deterioration until the readjustment of the arrangement position of the optical component is performed. desirable. Further, the state in which the light beam does not enter the optical sensor may be a failure of the light source, such as the light beam not being emitted from the light source. Therefore, it is required to establish a method for separating the cause.

In connection with the above, in the structure for forming an image by a plurality of light beams emitted from a plurality of laser light sources, even if some of the laser light sources fail, the deterioration of the image quality is reduced. However, the following techniques have been proposed as techniques that enable image formation.

That is, Japanese Unexamined Patent Publication No. 2000-180751.
In the gazette, while controlling the laser drive current by changing the laser drive current so that the light quantity of each laser detected by the photodiode becomes a constant value, the drive current of the laser is monitored and the drive current is significantly higher than the specified value. When it increases, it is recognized as a laser failure, the laser light source to be used is selected according to the location and number of failed lasers, and the scanning speed of the laser beam in the main scanning direction is increased according to the selected number of lasers. At the same time, a technique is disclosed in which the frequency of an image signal for turning on a laser light source is increased, at the same time, a user is notified of a failure of the laser and the user is prompted to replace the laser.

However, the technique described in the above publication detects the light quantity of each laser by the photodiode incorporated in the multi-beam laser, and in the case where the light quantity of the light beam cannot be detected due to the optical axis shift of the optical parts. Is not considered at all. Further, as a countermeasure against a failure of the light source, if the scanning speed of the laser beam is increased as described above, there is a disadvantage that noise and power consumption are increased, and in order to increase the frequency of the image signal. Requires an electric circuit to operate at high speed, and the noise emission level also increases accordingly.

Further, in Japanese Unexamined Patent Publication No. 10-151798, in a configuration in which two lines of light are normally used to record two lines on an electrostatic drum at the same time, one of the light emitting units has a light emitting capability. If an abnormality occurs, reduce the rotation speed (process speed) of the electrostatic drum by half,
A technique of forming an image by supplying all image signals to a normal light emitting unit is disclosed.

However, the technique described in the above publication is
The emission detection unit for failure detection, which consists of an optical sensor, detects whether each emission unit is emitting light normally. Is not detected, or no distinction is made between the optical axis shift and the failure of the light source. In addition, in order to realize the same image by changing the image signal supplied to the light emitting unit when the abnormality of the light emitting unit occurs, it is necessary to reduce the process speed by half. There is a drawback in that considerable complication is unavoidable.

Further, in Japanese Patent Laid-Open No. 2000-6463, in an image forming apparatus for forming an image (electrostatic latent image) on a photosensitive member by light beams from a plurality of light sources, the light emitting states of the plurality of light sources are changed. When the light emission state of any of the plurality of light sources is abnormal by the detection means, the image forming operation is performed using only the normal light sources, and the normal light sources are determined according to the number of normal light sources. There is disclosed a technique of switching the rising speed and the falling speed of the light beam from the device, adjusting the light amount of the light beam emitted from the normal light source, or adjusting the developing bias voltage of the developing device.
However, even the technique described in the above publication does not take into consideration the case where the light amount detection means cannot detect the light beam due to the optical axis shift of the optical component or the distinction between the optical axis shift and the light source failure.

The present invention has been made in consideration of the above facts, and even when the light amount of a part of the light beam cannot be detected, the image formation can be performed without causing the failure of the light source and the significant deterioration of the image quality. The purpose is to obtain an image forming apparatus that can be performed.

[0016]

In order to achieve the above object, an image forming apparatus according to a first aspect of the present invention scans a plurality of light beams emitted from a plurality of light sources on a scanned object. Thus, in the image forming apparatus for forming an image on the object to be scanned, the light amount detection is arranged at a position where a part of each of the plurality of light beams is incident and detects the light amount of the incident light beam. Means and first light amount control means for controlling the light amount of the light beam by changing the light source driving amount by negative feedback control so that the light amount detection value by the light amount detecting means becomes a predetermined value. Second light amount control means for controlling the light amount of the light beam by setting to a predetermined value, and light amount control for each of the plurality of light beams by either the first light amount control means or the second light amount control means What to do Selection means for-option, and comprising the.

In the image forming apparatus according to the first aspect of the present invention, a plurality of light beams are emitted from a plurality of light sources, and the plurality of light beams are respectively scanned on the object to be scanned,
An image is formed on the object to be scanned. In the invention according to claim 1, a light amount detecting means for detecting the light amount of the incident light beam is arranged at a position where a part of each of the plurality of light beams is incident, and the first light amount control means Controls the light quantity of the light beam by changing the light source drive quantity by negative feedback control so that the light quantity detection value by the light quantity detection means becomes a predetermined value.

As the light source according to the first aspect of the invention, for example, a surface emitting laser is suitable, but an edge emitting laser may be used, or another element capable of emitting a light beam may be used as the light source. You may use as. Further, the light source drive amount according to the invention of claim 1 may be, for example, a voltage applied to the light source, a current supplied to the light source, or both the voltage and the current. May be The light amount detection sensor according to the invention of claim 1 is, for example, a half mirror that separates the light beam, a light amount sensor that detects the light amount of the light beam, and the light beam that is separated by the half mirror is focused on the light amount sensor. It can be composed of optical components such as a lens.

Here, for example, when the optical components forming the light amount detecting means have an optical axis shift or the like and the light amount detecting means cannot detect the light amount of a part of the plurality of light beams, When the light quantity control means No. 1 tries to control the light quantity of the light beam, there is a possibility that the light source drive quantity becomes excessive by trying to match the light quantity detection value with a predetermined value, resulting in failure of the light source or extreme deterioration. There is. On the other hand, in the invention described in claim 1, second light amount control means for controlling the light amount of the light beam by setting the light source drive amount to a predetermined value is provided, and the selection means is a plurality of light beams. For each of the beams, it is selected which of the first light amount control means and the second light amount control means performs the light amount control.

The selecting means initially selects to perform the light quantity control by the first light quantity controlling means, as in the invention described in claim 2 described later, and the light source driving quantity is out of the predetermined range. With respect to the above, the light amount control may be switched to the light amount control by the second light amount control means. For example, at the time of manufacturing the image forming apparatus, the light beam is emitted from the light source with each optical component temporarily assembled. In the case where there is a possibility that the light quantity detection means cannot detect the light quantity of the majority of the plurality of light beams, the light quantity control of each light beam is performed by the second light quantity control means from the beginning. It can also be configured to be performed. Thus, even when there is a light beam whose light amount cannot be detected by the light amount detecting means, the light amount control of the light beam is performed by the second control.
The light quantity control means can prevent the light source from being damaged or extremely deteriorated due to the excessive light quantity drive amount.

Further, when the light quantity of a part of the light beam cannot be detected by the light quantity detecting means is a failure of the light source such as the light beam not being emitted from the light source, an image is formed on the object to be scanned. At this time, regardless of whether the light amount of the light beam is controlled by the first light amount control means or the second light amount control means, the light beam is not irradiated on the scanned object, so that it is formed on the scanned object. The degree of image quality deterioration of the image is also the same. However, when the reason why the light amount detecting means cannot detect the light amount of a part of the light beam is, for example, the optical axis shift of the optical component forming the light amount detecting means, the light amount of the light beam is controlled by the first light amount control. When controlled by the means, the light amount of the light beam becomes excessively large, which may cause failure of the light source or extreme deterioration, and in addition, the image quality may be deteriorated as compared with the case where the light beam is not irradiated to the scanned object. There is also.

On the other hand, according to the first aspect of the invention, the light quantity of the light beam whose light quantity cannot be detected by the light quantity detecting means is controlled by the second light quantity control means, so that the light quantity of the light beam is excessive (or excessively small). ), It is possible to prevent the image quality of the image formed on the scanned object from being significantly deteriorated. Therefore, according to the first aspect of the invention, even when the light amount of a part of the light beams cannot be detected, it is possible to perform image formation without causing a failure of the light source or causing a significant deterioration in image quality. .

In the invention according to claim 1, the selecting means sequentially controls the light quantities of the plurality of light beams by the first light quantity controlling means as described in claim 2, and at the same time, When the light source drive amount is out of the predetermined range while the light amount control means is changing the light source drive amount, it is determined to be abnormal, and the light amount control of the light beam by the first light amount control means is stopped, It is preferable that the light amount control of the light beam is performed by the second light amount control means.

As a result, only the light beam which has some abnormality (for example, optical axis shift of the optical component, failure of the light source, etc.) due to the drive amount of the light source being out of the predetermined range is
Since the light amount control means performs the light amount control, for example, for the light beam whose light amount may not be detected by the light amount detection means, the light amount control by the second light amount control means is selected from the beginning. Compared with, it is possible to further suppress the image quality deterioration of the image formed on the scanned object.

In the invention according to claim 2, the second
The light amount control means of, for example, as described in claim 3,
The light source drive amount may be configured to set a median value within a predetermined range. Accordingly, it is possible to prevent the light amount of the light beam whose light amount is controlled by the second light amount control means from being significantly deviated from the actual optimum light amount, and the light beam is formed on the object to be scanned. The degree of image quality deterioration of the image can be reduced.

Further, in the invention according to claim 2,
The light amount control means of, for example, as described in claim 4,
The light source drive amount may be set to a value substantially equal to the light source drive amount of another light beam set by the first light amount control means before the light beam. An LD array formed by forming a plurality of laser diodes (LDs) that can be used as a light source according to the present invention in a single array is generally manufactured by the same semiconductor process. The quantity-emitted light quantity characteristics do not differ significantly. Therefore, in particular, as a plurality of light sources according to the present invention, L
In the case of using the D array or the like, as described above, the light source drive amount is set to a value approximately equal to the light source drive amount of another light beam set by the first light amount control means before the light beam. As a result, it is possible to prevent the light amount of the light beam whose light amount is controlled by the second light amount control means from being significantly deviated from the actual optimum light amount, and the light beam is formed on the scanned object. The degree of image quality deterioration of the image can be reduced.

Further, in the invention described in claim 2,
The light amount control means of, for example, as described in claim 5,
As the light source drive amount, a value approximately equal to the average value of the light source drive amounts set by the first light amount control means is set for the light beams which are not judged to be abnormal by the selecting means among the plurality of light beams. It may be configured as follows. With this, similarly to the above-mentioned invention of claim 4, especially when the LD array is used as the plurality of light sources according to the present invention, the light quantity of the light beam whose light quantity is controlled by the second light quantity control means. However, it is possible to prevent a large deviation from the actual optimum light amount, and it is possible to reduce the degree of image quality deterioration of the image formed on the scanned object.

Further, in the invention described in claim 2,
The light amount control means of, for example, as described in claim 6,
As the light source drive amount, the light source drive amount at the time when the selection unit determines that the light source is abnormal may be set.
Also in this aspect, it is possible to prevent the light amount of the light beam whose light amount is controlled by the second light amount control means from being significantly deviated from the actual optimum light amount, and to be formed on the object to be scanned. It is possible to reduce the degree of image quality deterioration of the generated image.

According to a seventh aspect of the invention, in the invention according to any one of the second to sixth aspects, when the selection means determines that there is an abnormality, or the first light quantity control means and the second light quantity. When the light beam is emitted from the light source after the light amount control by at least one of the control means is finished, and the light amount detection value by the light amount detection means is outside the predetermined light amount range, the plurality of light sources can each emit the light beam. It is characterized in that it further comprises a judging means for judging whether or not the state is uncertain.

In the invention according to any one of claims 2 to 6, when the selection means determines that the light source drive amount is out of a predetermined range, the selection means is abnormal, or the first light amount control means and the second light amount control means. Even if the light amount control by at least one of the light amount control means is ended, when the light amount detection value by the light amount detecting means is out of the predetermined light amount range when the light beam is emitted from the light source after the light amount control, The abnormality such that a part of the plurality of light beams is not incident on the light amount detection means due to an optical axis shift of an optical component forming the light amount detection means,
Alternatively, there is a high possibility that an abnormality in which a light beam is not emitted from the light source has occurred due to a failure of the light source.

In the above case, the judging means according to the invention judges whether or not each of the plurality of light sources is capable of emitting a light beam. Therefore, the judging means causes each of the plurality of light sources to emit light. When it is determined that the beam can be emitted, there is an abnormality that at least one of the plurality of light beams is not incident on the light amount detection means, and the determination means causes at least one of the plurality of light sources. When it is determined that the light beam cannot be emitted, it can be recognized that there is an abnormality that the light beam is not emitted from at least one light source. Therefore, according to the invention of claim 7, it is possible to accurately determine the content of the abnormality that has occurred.

In the invention described in claim 7, the determination means determines whether or not each of the plurality of light sources is capable of emitting a light beam. For example, as described in claim 8, each of the plurality of light sources respectively determines. The light beam is emitted to form a predetermined evaluation image, the user is requested to visually evaluate the evaluation image and input the evaluation result, and the evaluation is input based on the evaluation result input through the input means. be able to.

The formation of the evaluation image is to form an image formed by gathering a plurality of lines each having a width corresponding to one scanning line or a small number of lines by using a small number of one or two light beams. Can be performed by sequentially switching the light beam to be used. In the above aspect, the number of light beams to be scanned may be determined according to the minimum width of lines that can be visually recognized on the formed image (for example, the scanning line 1
If a line with a width of one line is visible on the image, the light beams are scanned one by one, and if the minimum width of the line visible on the image is two scanning lines, then two light beams are scanned. Etc.) The evaluation image is not limited to the above-mentioned image, but in the case where there is a light source that cannot emit a light beam among a plurality of light sources, it is an image that can identify the light beam (and the light source) that is not emitted from the light source. Is desirable.

By forming the evaluation image as described above,
If a plurality of light sources can emit light beams,
If there is no remarkable density fluctuation in the evaluation image and at least one of the plurality of light sources is incapable of emitting a light beam, a significant density fluctuation will partially occur in the evaluation image. Whether or not each of the light sources is capable of emitting a light beam appears as visible information. According to the eighth aspect of the invention, the user visually evaluates whether or not there is a significant partial density variation in the evaluation image, and information indicating whether or not there is a partial significant density variation in the evaluation image. Is inputted as an evaluation result via the input means, and based on the inputted evaluation result, it is judged whether or not a plurality of light sources are capable of emitting light beams, respectively. Therefore, it is possible to reliably determine whether or not the plurality of light sources are in the states capable of emitting light beams.

In the invention described in claim 7, the determination by the determination means is not limited to the determination by forming the evaluation image and allowing the user to evaluate as described above. As described above, the plurality of light sources respectively emit light beams based on whether or not the plurality of light beams are respectively detected by the light detection means which is provided separately from the light amount detection means and is capable of detecting the plurality of light beams. Alternatively, it may be determined whether or not the injection is possible. As the light detection means, for example, a light detection means for a synchronization signal (for example, an SOS sensor) provided for the purpose of generating a synchronization signal that defines the modulation start timing in each scanning of the light beam.
Can be used.

Further, whether or not each of the plurality of light sources is capable of emitting a light beam is specifically determined by, for example, emitting light beams in order from the individual light sources and outputting one light beam to the light detecting means. If there is a light beam that is not detected by the light detection unit, it can be determined that the light source that emits the light beam is not in a state capable of emitting the light beam. According to the invention described in claim 9, it is possible to determine whether or not each of the plurality of light sources is capable of emitting a light beam, without a user's hand.

The light intensity of each light beam (light beam 1
The light amount per line) is smaller than the minimum value of the light amount range that can be detected by the light detection unit, and when the light beams incident one by one cannot be detected, the light amount range that the light detection unit can detect is changed. A means may be provided to reduce the minimum value of the light amount range that can be detected by the light detecting means by the means, or the light beams may be emitted from two or more light sources, respectively. It is also possible to deal with it by making it incident on the light detection means at the same time.

According to a tenth aspect of the present invention, in the invention according to any one of the seventh to ninth aspects, when the judging means judges that a plurality of light sources can respectively emit light beams, It is determined that at least one of the plurality of light beams is not incident on the light amount detection means and a first abnormality has occurred, and at least one of the plurality of light sources is determined to be in a state in which the light beam cannot be emitted. In this case, it is determined that the second abnormality in which the light beam is not emitted from at least one light source is occurring, and it is determined that the first abnormality is occurring in response to the abnormality determined to be occurring. It is characterized in that different processing is performed depending on the case and the case where it is determined that the second abnormality has occurred.

As described above, according to the invention described in any one of claims 7 to 9, when an abnormality occurs, it is determined whether or not each of the plurality of light sources can emit a light beam. it can. Here, if the plurality of light sources can emit light beams respectively, it is considered that the optical axis shift of the optical components forming the light amount detecting means is the cause, and the light source according to any one of claims 2 to 6. By implementing the invention, the deterioration of the image quality can be further reduced, but when at least one of the plurality of light sources cannot emit a light beam,
Even if the invention according to any one of claims 2 to 6 is implemented, the image quality deterioration of an image cannot be reduced.

As described above, the measures for reducing the deterioration of the image quality are different depending on the cause of the abnormality that has occurred. However, in the invention according to claim 10, as a countermeasure for the abnormality, one of a plurality of light beams is used. If it is determined that at least one of the first abnormalities is not incident on the light amount detecting means (in the case where a plurality of light sources can emit light beams),
A second light beam which is not emitted from at least one light source,
Different processing is performed when it is determined that the abnormality has occurred (when at least one of the plurality of light sources is in a state in which the light beam cannot be emitted), so image quality degradation when the abnormality occurs is guaranteed. Can be reduced to

Incidentally, when it is determined that the second abnormality has occurred (when at least one of the plurality of light sources is in a state where the light beam cannot be emitted), a measure (a process for reducing image quality deterioration) ), For example, the above-mentioned JP-A-200
The processes described in Japanese Patent Application Laid-Open No. 0-180751, Japanese Patent Application Laid-Open No. 10-151798, Japanese Patent Application Laid-Open No. 2000-6463, etc. may be mentioned, but other known processes may be performed.

Further, in the invention described in claim 10, the judging means specifies the light beam which is not emitted from the light source when it is judged that the second abnormality has occurred as described in claim 11, for example. It is preferable to store information for identifying the specified light beam in the storage means. For example, the processing described in each of the above publications can be applied as a countermeasure when it is determined that the second abnormality has occurred. It is necessary to recognize the light beam that is not emitted from the light source since the light source is switched. According to the invention of claim 11, the light beam not emitted from the light source is specified and the information is stored in the storage means by the judgment means. Therefore, the information stored in the storage means is used for coping with the second abnormality. be able to.

According to a twelfth aspect of the present invention, in the invention according to the eleventh aspect, when the light beam emitted from the light source is modulated to form an image, the scanning position on the object to be scanned is not emitted from the light source. For at least one light beam close to the light beam specified as the light beam,
Based on the modulation signal for modulating the specified light beam, the time during which the specified light beam is emitted from the light source is extended near the timing at which the specified light beam should be emitted from the light source, or originally emitted from the light source. It is characterized by further comprising a modulation control means for controlling the modulation of the at least one light beam so that the light source emits the light even during a period in which the light source is not operated.

The inventor of the present application particularly has a condition that the resolution of an image to be formed is very high (for example, 1500 dpi or more) and that the number of light beams simultaneously scanning the object to be scanned is large (for example, 10 or more). Does not contribute to image formation because a small part of the large number of light beams scanned at the same time is not emitted from the light source (even when the light amount is significantly insufficient) (exposure is impossible). Na)
It was confirmed by experiments that even in the state, in the high density portion in the image where the light beam irradiation area per unit area is large, the image quality is slightly deteriorated with only a slight decrease in density. In addition, the inventor of the present application has found that, in the middle / low density portion where the light beam irradiation area per unit area is narrow, the density is lowered due to the influence of a part of the light beam that is not emitted from the light source, but the scanning position on the scanned object is It was confirmed by experiments that if a light beam adjacent to a light beam not emitted from the light source is irradiated onto the object to be scanned instead of the light beam not emitted from the light source, the density reduction can be improved even in the intermediate / low density image portion.

Based on the above, in the invention according to claim 12, the scanning position on the object to be scanned is at least one light beam close to the light beam specified as the light beam not emitted from the light source, Based on the modulation signal for modulating the specified light beam, the time during which the specified light beam is emitted from the light source is extended near the timing at which the specified light beam should be emitted from the light source, or originally emitted from the light source. Since the modulation of the at least one light beam is controlled so as to be emitted from the light source even in the period not to be performed, when the second abnormality occurs in which the light beam is not emitted from the at least one light source, for example, the scanning speed is It is possible to suppress the deterioration of image quality to the minimum without significantly changing the processing in the image forming apparatus such as changing the process speed or the process speed.

Further, in the invention described in claim 10, it is determined that the determining means has occurred when it is determined that the first abnormality or the second abnormality has occurred, for example, as described in claim 13. It is preferable to present a plurality of measures to the determined abnormality to the user and to take the measure selected by the user. As a measure against the occurrence of the first abnormality, for example, there is a measure to set the light source drive amount for the light beam not incident on the light amount detection means to a predetermined value by the second light amount control means. As the value (light source driving amount), for example, there are a plurality of options as described in claims 3 to 6. In addition, as a measure against the second abnormality, for example, the above-described Japanese Patent Laid-Open No. 2000-1807.
51, JP 10-151798 A, JP 2
The processing described in Japanese Patent Application Laid-Open No. 000-6463, or claim 12
Although there are advantages and disadvantages in dealing with the second abnormality, the image quality of the image to be formed (resolution or reproducibility of the original image, etc.), image forming speed, noise, The reality is that there are no measures to satisfy all of the items such as power consumption. On the other hand, in the invention according to claim 13, a plurality of measures for the abnormality determined to have occurred are presented,
Since the countermeasure selected by the user is taken, it is possible to take the most desirable countermeasure for the user as the countermeasure for the abnormality that has occurred.

[0047]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, an example of an embodiment of the present invention will be described in detail with reference to the drawings.

[First Embodiment] FIG. 1 shows an image forming apparatus 10 according to the first embodiment. The image forming apparatus 10 includes a photoconductor drum 12 rotated in a direction indicated by an arrow A in FIG. 1 at a predetermined rotation speed by a driving unit (not shown). Above the photoconductor drum 12, an outer peripheral surface of the photoconductor drum 12 is provided. A charger 14 is provided for charging the. The photosensitive drum 12 corresponds to the scanned object according to the present invention.

Above the charger 14, the light beam scanning device 1 is provided.
6 are arranged. As will be described in detail later, the light beam scanning device 16 modulates a plurality of laser beams emitted from a light source in accordance with an image to be formed and deflects the laser beams in the main scanning direction to form an outer peripheral surface of the photosensitive drum 12. The upper part is scanned parallel to the axis of the photosensitive drum 12. As a result, an electrostatic latent image is formed on the outer peripheral surface of the photoconductor drum 12.

A developing device 18 is provided on the side of the photosensitive drum 12.
Are arranged. The developing device 18 includes a roller-shaped container rotatably arranged. Four accommodating portions are formed inside the accommodating body, and developing devices 18Y, 18M, 18C, and 18K are provided in each accommodating portion. Each of the developing devices 18Y, 18M, 18C, and 18K includes a developing roller 20, and internally stores toners of colors Y, M, C, and K, respectively. Further, on the opposite side of the developing device 18 with the photoconductor drum 12 interposed therebetween, a static eliminator / cleaner having a function of neutralizing the outer peripheral surface of the photoconductor drum 12 and a function of removing unnecessary toner remaining on the outer peripheral surface. 22 are arranged.

The formation of a full-color image by the image forming apparatus 10 according to this embodiment is performed while the photosensitive drum 12 makes four revolutions. That is, while the photoconductor drum 12 makes four revolutions, the charger 14 continues to charge the outer peripheral surface of the photoconductor drum 12, the charge / cleaner 22 continues to charge the outer peripheral surface, and the light beam scanning device 16 should form. Y, which represents a color image
Scanning the outer peripheral surface of the photoconductor drum 12 with a laser beam modulated according to any of M, C, and K image data is used to modulate the laser beam each time the photoconductor drum 12 makes one rotation. Repeat while switching the image data to be used. The developing device 18 includes developing devices 18Y, 18M, 18
The developing roller 20 of either C or 18K is the photosensitive drum 1.
In the state corresponding to the outer peripheral surface of No. 2, the developing device corresponding to the outer peripheral surface is operated to develop the electrostatic latent image formed on the outer peripheral surface of the photoconductor drum 12 into a specific color. Drum 12
The formation of the toner image of the specific color on the outer peripheral surface is repeated while rotating the container so that the developing device used for developing the electrostatic latent image is switched every time the photosensitive drum 12 rotates once.

As a result, every time the photosensitive drum 12 makes one rotation, Y, M,
The toner images of C and K are sequentially formed so as to overlap each other, and a full-color toner image is formed on the outer peripheral surface of the photoconductor drum 12 when the photoconductor drum 12 has rotated four times.

An endless intermediate transfer belt 24 is arranged substantially below the photosensitive drum 12. The intermediate transfer belt 24 is wound around rollers 26, 28 and 30.
The outer peripheral surface is arranged so as to contact the outer peripheral surface of the photosensitive drum 12. The rollers 26 to 30 are rotated by the driving force of a motor (not shown) being transmitted, and the intermediate transfer belt 24 is rotated.
Rotate in the direction of arrow B.

A transfer device 32 is arranged on the opposite side of the photosensitive drum 12 with the intermediate transfer belt 24 interposed therebetween, and the toner image formed on the outer peripheral surface of the photosensitive drum 12 is transferred to the transfer device 3.
2 is transferred onto the image forming surface of the intermediate transfer belt 24. When the toner image formed on the outer peripheral surface of the photoconductor drum 12 is transferred to the intermediate transfer belt 24, the area of the outer peripheral surface of the photoconductor drum 12 which carried the transferred toner image is neutralized. -Cleaned by the cleaner 22.

A tray 34 is arranged below the intermediate transfer belt 24, and a large number of sheets P as recording materials are accommodated in the tray 34 in a stacked state. A take-out roller 36 is arranged diagonally above and to the left of the tray 34 in FIG. The recording paper located at the uppermost position in the stacked state is taken out from the tray 34 by rotating the take-out roller 36, and the roller pair 38,
It is conveyed by rollers 40.

A transfer device 42 is arranged on the opposite side of the roller 30 with the intermediate transfer belt 24 interposed therebetween. The sheet P conveyed by the roller pair 38 and the roller 40 is sent between the intermediate transfer belt 24 and the transfer device 42, and the toner image formed on the image forming surface of the intermediate transfer belt 24 is transferred by the transfer device 42. . A fixing device 44 including a fixing roller pair is provided downstream of the transfer device 42 in the transport direction of the paper P.
The sheet P on which the toner image has been transferred is discharged outside the machine body of the image forming apparatus 10 after the transferred toner image is melted and fixed by the fixing device 44, and is placed on a paper discharge tray (not shown). Placed.

Next, referring to FIG. 2, the light beam scanning device 16
Will be described. The light beam scanning device 16 includes a number of surface emitting lasers (hereinafter, simply referred to as LDs) that emit laser beams.
The LD array 50 is formed by arraying. Although only three laser beams are shown in FIG. 2 for simplification, the LD array 50 is actually an array of several tens of LDs and is capable of emitting several tens of laser beams. ing. Although the individual LDs are arranged two-dimensionally (in a matrix) on the LD array 50, it is also possible to arrange them in one row instead.

A collimator lens 52 and a half mirror 54 are sequentially arranged on the laser beam emitting side of the LD array 50. The laser beam emitted from the LD array 50 is made into a substantially parallel light flux by the collimator lens 52, and then is incident on the half mirror 54.
A part is separated and reflected by 4. Half mirror 54
A lens 56 and a light amount sensor 58 on the laser beam reflection side of the
Are sequentially arranged, and a part of the laser beam separated / reflected from the main laser beam (the laser beam used for exposure) by the half mirror 54 passes through the lens 56 and is incident on the light amount sensor 58. The amount of light is detected by. The half mirror 54 and the lens 56
The light amount sensor 58 corresponds to the light amount detecting means of the present invention.

On the main laser beam emission side of the half mirror 54, an aperture 60, a cylinder lens 62 having power only in the sub-scanning direction, and a folding mirror 64 are arranged in order, and the main laser beam emitted from the half mirror 54 is After being shaped by the aperture 60, it is refracted by the cylinder lens 62 so as to form a long linear image in the main scanning direction in the vicinity of the reflecting surface of the rotary polygon mirror 66, and reflected by the folding mirror 64 toward the rotary polygon mirror 66 side. It The aperture 60 is preferably arranged near the focal position of the collimator lens 52 in order to evenly shape the plurality of laser beams.

The rotary polygon mirror 66 is rotated in the direction of arrow C in FIG. 2 when the driving force of a motor (not shown) is transmitted, and the laser beam reflected by the folding mirror 64 and incident is deflected / reflected along the main scanning direction. To do. Rotating polygon mirror 66
Fθ lenses 68 and 70 having power only in the main scanning direction are arranged on the laser beam emitting side of the laser beam, and the laser beam deflected / reflected by the rotating polygon mirror 66 is substantially on the outer peripheral surface of the photosensitive drum 12. It is moved at a constant speed and is refracted by the Fθ lenses 68 and 70 so that the image forming position in the main scanning direction coincides with the outer peripheral surface of the photosensitive drum 12.

Cylinder mirrors 72 and 74 having power only in the sub-scanning direction are sequentially arranged on the laser beam emitting side of the Fθ lenses 68 and 70.
The laser beam that has passed through 70 is reflected by the cylinder mirrors 72 and 74 so that the image forming position in the sub-scanning direction coincides with the outer peripheral surface of the photoconductor drum 12, and the photoconductor drum 12
Is irradiated on the outer peripheral surface of the. The cylinder mirror 72,
Reference numeral 74 also has a surface tilt correction function for making the outer peripheral surfaces of the rotary polygon mirror 66 and the photosensitive drum 12 conjugate with each other in the sub-scanning direction.

On the laser beam emitting side of the cylinder mirror 72, a pickup mirror 76 is arranged at a position corresponding to the end (SOS: Start Of Scan) of the scanning start side in the laser beam scanning range. An SOS sensor 78 is arranged on the laser beam emitting side of the pickup mirror 76. When the laser beam emitted from the LD array 50 is such that one of the reflecting surfaces of the rotary polygon mirror 66 that reflects the laser beam is oriented to reflect the incident beam in the direction corresponding to SOS, The light is reflected by the pickup mirror 76 and is incident on the SOS sensor 78 (see also the imaginary line in FIG. 2).

The signal output from the SOS sensor 78 is
To modulate the laser beam scanned on the outer peripheral surface of the photoconductor drum 12 with the rotation of the rotary polygon mirror 66 to form an electrostatic latent image, in order to synchronize the modulation start timing in each main scan. Used.

Next, the structure of the control unit for controlling the emission of the laser beam from the LD array 50 of the light beam scanning device 16 will be described with reference to FIG. The control unit includes an information processing unit 80. The information processing unit 80 includes a display unit 82 including an LCD or the like provided on the front panel of the image forming apparatus 10 and an input unit including a plurality of keys. 8
4 is connected. Further, the information processing unit 80 is connected to a rotation driving unit 86 that rotationally drives the photoconductor drum 12, and the video control unit 88 and the LD array control unit 9 are connected.
0 is connected to each. The video control unit 88 and the LD array control unit 90 are connected to each other, and the video control unit 8
8 is connected to the SOS sensor 78, and the LD array controller 90 is connected to the light amount sensor 58. LD array control unit 9
0 is connected to the LD array 50 via the LD array drive unit 92.

Further, as shown in FIG. 4, the video control unit 88
Is a timing measuring unit 9 connected to the SOS sensor 78.
4, the output end of the timing measuring unit 94 is connected to the input ends of the APC video signal generator 96 and the SOS detection video signal generator 98, respectively. The output terminals of the APC video signal generator 96 and the SOS detection video signal generator 98 are connected to the input terminals of the video signal selector 100. The input ends of the video signal selector 100 are connected to the information processing unit 80, the LD array control unit 90, and the output ends of the beam abnormality determination image data generator 102, respectively. Is connected to the output end of the information processing unit 80.

The output terminal of the video signal selector 100 has a video signal changing section 104 and a first abnormal beam storage section 10.
6 are respectively connected to the input terminals. The input end of the first abnormal beam storage unit 106 is also connected to the output end of the LD array control unit 90, and the output end of the first abnormal beam storage unit 106 is connected to the input end of the abnormality cause determination unit 108. . The input end of the abnormality cause determination unit 108 is the second abnormal beam storage unit 1
The output terminal of the second abnormal beam storage unit 110 is also connected to the output terminal of the information processing unit 80. The output end of the abnormality cause discriminating unit 108 is the information processing unit 8.
0 and the input terminal of the video signal changing unit, respectively. The video control unit 88 also includes a light amount setting unit 112, a forced drive amount setting unit 114, and an optical axis adjustment forced lighting instruction unit 11.
6, the light amount setting unit 112, the forced drive amount setting unit 114, the optical axis adjustment forced lighting instruction unit 116, the output terminals of the APC video signal generator 96 and the video signal changing unit 104 are LD array control units. 90 input terminals are respectively connected.

The LD array control unit 90 has the same number of drive amount control units 118 as shown in FIG. 5 as the number of LDs in the LD array 50. The drive amount control unit 118 includes an amplifier 120. One of the two input ends of the amplifier 120 is connected to the output end of the light amount setting unit 112 and the other is connected to the light amount sensor 58, and the output end of the amplifier 120 is Sample and hold circuit 1
It is connected to the input end of 22. The sample-hold circuit 122 is conceptually composed of a capacitor, one end of which is connected to the signal line and the other end of which is grounded, and a switching means which turns on and off between the output end of the amplifier 120 and one end of the capacitor. The input terminal of the sample hold circuit 122 is the video signal generator 96 for APC of the video control unit 88.
Of the APC video signal generator 96 of the video control unit 88.
Is turned on when an APC signal is input from.

Further, the drive amount control unit 118 is provided with a mode changing unit 124, and the mode changing unit 124 receives a signal (capacitor terminal voltage: drive amount control signal) from a capacitor via a signal line and also compulsorily. A forced drive amount setting signal is input from the drive amount setting unit 114. The mode changing unit 124 is conceptually configured by a switching unit that selectively outputs the drive amount control signal input from the capacitor and the forced drive amount setting signal input from the forced drive amount setting unit 114. , This switching means
It switches according to the mode change signal input from the OR circuit 126.

The signal output from the mode changing means 124 is output to the LD array drive section 92 as a drive amount control signal and also input to the comparator 128. Further, the drive amount upper limit level setting signal is input from the light amount setting unit 112 to the comparator 128. The output terminal of the comparator 128 is connected to the information processing section 80 and the input terminal of the OR circuit 126 via the latch 130, and the input terminal of the OR circuit 126 is also connected to the compulsory lighting instruction section 116 for optical axis adjustment. There is.

Next, the operation of the first embodiment will be described. In the image forming apparatus 10, image data representing an image to be formed is input to the information processing unit 80 from the outside, and the information processing unit 80
Turns on / off the emission of the laser beam from each LD of the LD array 50 so that the input image data is formed on the outer peripheral surface of the photosensitive drum 12 as an electrostatic latent image of the image represented by the image data. To a modulated signal (hereinafter referred to as a video signal) for outputting. The video signal output from the information processing unit 80 is input to the video signal selector 100 of the video control unit 88. Further, the information processing unit 80
Various information is displayed on the display unit 82, and the operation of each unit of the image forming apparatus 10 is controlled in accordance with an instruction input by the user via the input unit 84.

When the laser beam emitted from the LD array 50 and deflected and scanned by the rotary polygon mirror 66 crosses the light receiving surface of the SOS sensor 78, the SOS sensor 7 is detected.
When the laser beam is detected by 8, the SOS signal is input from the SOS sensor 78 to the timing measuring unit 94. The timing measuring unit 94 detects the start timing of the main scanning of the laser beam based on the input SOS signal and measures the main scanning period of the laser beam,
The timing information indicating the measurement result is output to the SOS detection video signal generator 98 and the APC video signal generator 96.

The SOS detection video signal generator 98 detects the laser beam by the SOS sensor 78 in each main scan on the basis of the timing information input from the timing measuring section 94, so that the SOS is detected in each main scan. The period when the laser beam crosses the light receiving surface of the sensor 78 (SOS
During a period, an SOS detection video signal for emitting a laser beam from the LD (driving the LD for lighting) is generated and output to the video signal selector 100. In order to avoid a situation in which the SOS sensor 78 cannot detect the laser beam due to the insufficient amount of received light, the SOS detection video signal generator 98 uses a large number of LDs of the LD array 50 as SOS detection video signals. A signal for driving a plurality (for example, two) of the LDs to light up during the SOS period is generated.

Also, the APC video signal generator 96 is
Based on the timing information input from the timing measurement unit 94, the period (image forming period) in which an image is formed by the laser beam and the SO in the main scanning period of each time.
For the purpose of performing APC for sequentially controlling the light amount of each laser beam emitted from each LD of the LD array 50 during a predetermined period (APC period) excluding the S period, L
A video signal for APC for sequentially lighting and driving the individual LDs of the D array 50 is generated, and the video signal selector 100
Output to.

The video signal selector 100 includes an information processing section 8
The video signal input from 0, the SOS detection video signal input from the SOS detection video signal generator 98, and the AP input from the APC video signal generator 96.
A video signal in which the C video signal is superimposed is generated and output to the LD array drive unit 92 via the video signal changing unit 104 (the above video signal is the first abnormal beam storage unit 106).
Will also be entered).

The LD array controller 90 controls the LD array 50.
Drive amount control section 118 provided for each individual LD
At, the drive amount of the corresponding LD is set, and the set LD drive amount is output to the LD array drive unit 92 as a drive amount setting signal. The LD array drive unit 92 turns on and off each LD of the LD array 50 at a timing according to the video signal input from the LD array control unit 90, and also responds to the drive amount control signal input from the LD array control unit 90. By driving each LD with a large driving amount (for example, current), the light amount of the laser beam emitted from each LD during the lighting drive of each LD is controlled.

By the way, in the present embodiment, the LD mode is set based on the light amount signal from the light amount sensor 58 as the APC mode.
A light amount control mode for setting the drive amount of each LD of the array 50 and a forced control mode for forcibly setting the drive amount of each LD are prepared. In the following, first, the light quantity control mode of the APC will be described.

The APC video signal generator 96 is an APC
In order to perform APC during the period, the individual LDs of the LD array 50 are sequentially driven to be turned on by the video signal for APC, and the APC signal is sent to the drive amount control unit 118 of the LD array control unit 90 corresponding to the LDs that are driven to be turned on. Output. L
A part of the laser beam emitted from the D array 50 is reflected by the half mirror 54 and enters the light amount sensor 58, and the light amount is detected by the light amount sensor 58. The signal output from the light amount sensor 58 is current-voltage converted by a signal processing circuit (not shown), and the drive amount control unit 11 produces a light amount signal having a voltage level corresponding to the light amount of the laser beam.
8 to the amplifier 120.

Further, the light amount setting signal of the voltage level corresponding to the light amount setting value of the laser beam emitted from each LD of the LD array 50 is input to the amplifier 120 from the light amount setting section 112. The amplifier 120 is composed of a differential amplifier, amplifies the difference between the voltage levels of the light amount setting signal and the light amount signal, and outputs the amplified difference to the sample hold circuit 122. Here, the AP input from the APC video signal generator 96 is supplied to the drive amount control unit 118 corresponding to the APC target LD.
The switching means of the sample hold circuit 122 is turned on by the C signal, so that the output end of the amplifier 120 is electrically connected to one end of the capacitor, and the capacitor is charged by the output voltage of the amplifier 120.

In the light quantity control mode, the mode changing means 12
The switching means of No. 4 is switched so as to output the terminal voltage of the capacitor, and this terminal voltage is output to the LD array drive unit 92 as a drive amount control signal, and in accordance with this drive amount control signal, the LD of the APC target The light amount of the output laser beam is controlled. The voltage across the capacitor of the sample-hold circuit 122 (voltage level of the drive amount control signal) changes at a changing speed according to the deviation between the light amount setting value represented by the light amount setting signal and the actual light amount represented by the light amount signal, and When the light amount matches the light amount setting value, the amplifier 12
It becomes constant when the output voltage of 0 becomes 0. Thus, the amplifier 120 and the sample hold circuit 122
Corresponds to the first light amount control means of the present invention.

During the APC period, the above-described processing is repeated while sequentially switching the LDs to be APCs, so that the light amounts of the laser beams emitted from the respective LDs are, for example, beams 1, 2, and 3 shown in FIG. The driving amount of each LD is negatively feedback controlled so as to match the light amount setting value.

In the light beam scanning device 16 according to this embodiment, since the optical path length from the LD array 50 to the light quantity sensor 58 is long, for example, a shock is applied to the casing of the light beam scanning device 16 from the outside, and the half mirror 54. By shifting the optical axes of the lens, the lens 56, the light amount sensor 58, etc.,
A part of the laser beam emitted from each LD of the D array 50 may not enter the light amount sensor 58. In this case, the light amount of the laser beam is detected by the light amount sensor 5
8 is not detected, the LD drive amount continues to increase because the output voltage of the amplifier 120 does not decrease when APC is performed on the LD that emits the laser beam.
If D is driven with an excessive amount of drive, there is a risk that the LD will fail or the LD will significantly deteriorate.

On the other hand, in this embodiment, the light quantity setting unit 1
The drive amount upper limit level setting signal is input from 12 to the comparator 128. The drive amount upper limit level setting signal is a signal that defines the upper limit of the drive amount control range (see also FIG. 6) in the light amount control mode, and has the same level as the level of the drive amount control signal corresponding to the upper limit of the drive amount control range. It is said that. In addition, the forced drive amount setting unit 114 sets L in the forced control mode.
The forced drive amount setting signal that specifies the D drive amount is output.
In the present embodiment, the drive amount defined by the forced drive amount setting signal is the drive amount corresponding to the central value of the drive amount control range.

As a result, the mode changing means 124 outputs L
When the level of the drive amount control signal output to the D array drive unit 92 becomes higher than the drive amount upper limit level setting signal, the level of the output signal of the comparator 128 switches from low level to high level, and the level of this output signal changes. Latch 13
It is held at 0 and input to the OR circuit 126, and OR
When the mode change signal output from the circuit 126 becomes high level, the mode change unit 124 outputs the signal from the sample hold circuit 122 (light amount control mode) to the forced drive amount setting unit 114. Switch to the state (forced control mode) that outputs the signal. As described above, the forced drive amount setting unit 114 corresponds to the second light amount control means of the present invention (specifically, the second light amount control means according to claim 3), and includes the comparator 128, the latches 130, O.
The R circuit 126 and the mode changing means 124 correspond to the selecting means (specifically, the selecting means described in claim 2) of the present invention.

Therefore, when the light quantity of the laser beam emitted from the LD for APC is not normally detected by the light quantity sensor 58 and the driving quantity for the LD for APC exceeds the upper limit of the driving quantity control range, the APC The mode of the APC for the target LD shifts from the light amount control mode to the forced control mode, and as shown by the beam 4 in FIG.
Since the light amount of the laser beam emitted from the LD targeted for PC is forcibly set to the center value of the drive amount control range, it is possible to prevent the LD from failing or being significantly deteriorated. Further, as described above, it is possible to prevent the light amount of the laser beam whose light amount cannot be detected by the light amount sensor 58 from becoming excessive, so that it is possible to form an image without causing a significant deterioration in image quality.

When there is a high possibility that the light quantity of the laser beam cannot be detected by the light quantity sensor 58, such as when assembling the light beam scanning device 16 and adjusting the optical axis of the optical component, the optical axis is high. Forced lighting instruction section 116 during adjustment
Switches the mode signal (normally low level) output to the OR circuit 126 to high level. Also in this case, since the APC mode is switched from the light amount control mode to the forced control mode similarly to the above, each LD of the LD array 50 is prevented from being driven with an excessive driving amount, and the LD array 5 is prevented.
It is possible to perform operations such as assembly and optical axis adjustment using the laser beam emitted from 0.

By the way, when the APC mode of a particular LD is switched to the forced control mode, the level of the output signal of the comparator 128 is switched from low level to high level.
This output signal is output to the video control unit 88 and the information processing unit 80 as an abnormality detection signal via the latch 130 to notify that some abnormality has occurred. The abnormality detection signal output to the video control unit 88 is input to the first abnormal beam storage unit 106.

A video signal output from the video signal selector 100 is input to the first abnormal beam storage unit 106, and the first abnormal beam storage unit 106 outputs an abnormal signal based on the input video signal. The LD for which the APC was performed when the detection signal was input (that is, the LD whose APC mode has been switched to the forced control mode) is specified, and the information for identifying the specified LD is stored as the information of the LD in which the abnormality has occurred. . Therefore, even when a plurality of LDs in which the APC mode is switched to the forced control mode occur until the APC for each LD of the LD array 50 is completed, each LD is regarded as an abnormal LD and the first abnormal beam is detected. Each is stored in the storage unit 106.

On the other hand, when the LD in which the APC mode is switched to the forced control mode occurs, the cause is that the laser beam is emitted from the LD in addition to the optical axis shift of the half mirror 54, the lens 56, the light amount sensor 58, and the like. It is also possible that the LD is out of order. Therefore, in the first embodiment, each of the LDs in the LD array 50 can emit a laser beam by recording an abnormality determination image (details will be described later) on the paper P, allowing the user to perform an inspection, and inputting the inspection result. It is determined whether or not

That is, when the abnormality detection signal is input from the LD array control unit 90 (driving amount control unit 118), the information processing unit 80 waits until the timing at which the abnormality determination image can be recorded on the paper P arrives. An abnormality determination image output signal for instructing the output (recording) of the abnormality determination image is output to the beam abnormality determination image data generator 102 and the video signal selector 100 of the video control unit 88. The beam abnormality determination image data generator 102 has image data representing a predetermined abnormality determination image stored in advance in a memory or the like. Abnormality judgment image (electrostatic latent image) represented by the image data
A video signal for forming the video signal is output to the video signal selector 100.

The video signal selector 100 includes an information processing section 8
When the abnormality determination image output signal is input from 0, the video signal for forming the abnormality determination image input from the beam abnormality determination image data generator 102 is replaced with the video signal input from the information processing unit 80 at normal times. Output. By inputting this video signal to the LD array drive unit 92 via the LD array control unit 90, each LD of the LD array 50 is driven according to the video signal for forming an abnormality determination image, and the LD of the photoconductor drum 12 is driven. An abnormality determination image is recorded on the paper P by forming an electrostatic latent image of the abnormality determination image on the outer peripheral surface, and performing each processing of development, transfer, and fixing on the electrostatic latent image. become.

The above-mentioned abnormality determination image may be any image as long as it can identify the LD that cannot emit a laser beam among the LDs of the LD array 50, and various images are possible. In the present embodiment, as shown in FIG. 7A, as an example, only one of the LDs in the LD array 50 is driven to light up (laser beam is emitted), and a plurality of main scans are performed. An image is formed by repeating the process of exposing and recording the abnormality determination patch repeatedly until all the LDs are turned on while sequentially switching the LDs to be turned on. Note that FIG. 7 shows the number of LDs (L
The number of laser beams that can be originally emitted from the D array is 4
However, the LD array 5 according to the present embodiment is shown.
Since 0 is a configuration in which several tens of LDs are arrayed, the above processing actually causes the same number as the number N of LDs provided in the LD array as shown in FIG. 8A as an example. An abnormality determination image including the abnormality determination patch is formed.

Further, in the present embodiment, in order to identify each abnormality determination patch of the abnormality determination image, as shown in FIG. 8A, each abnormality determination patch is given an identification number. This identification number is used when the LD that has been driven to light for exposing and recording the individual abnormality determination patch does not actually emit a laser beam, or when the laser beam emitted from the LD that has been driven to drive is the light of the optical component. The LD array 5 is arranged so that it can be visually recognized on the abnormality determination image even when the photosensitive drum 12 is not irradiated due to the axis shift.
It is desirable to drive all the LDs of 0 for lighting and perform exposure recording.

When the abnormality determination image is recorded on the sheet P as described above, the information processing section 80 is, for example, as shown in FIG.
As shown in, the abnormality judgment image recorded on the paper P is visually inspected, and if there is an abnormality judgment patch having a remarkably low density,
A failure determination image evaluation screen requesting the user to input the identification number attached to the patch is displayed on the display unit 82. As a result, if the abnormality determination image does not include an abnormality determination patch having a remarkably low density, the identification number of the abnormality determination patch must be input by the user who has completed the visual inspection of the abnormality determination image. If the display end of the failure judgment image evaluation screen is instructed, the information processing unit 80 may not emit a laser beam, or the emitted laser beam may not be irradiated onto the photoconductor drum 12 (second abnormality). It can be recognized that there is no LD occurring.

If the abnormality determination image includes an abnormality determination patch having a remarkably low density, the user who has completed visual inspection of the abnormality determination image has determined that the abnormality determination is a remarkably low density. By inputting the patch identification number by the user via the input unit 84, the information processing unit 80 can recognize the abnormality determination patch having a remarkably low density, and when the recognized abnormality determination patch is exposed and recorded. It is possible to recognize the LD that has been driven to turn on as the LD having the second abnormality. The recognition of the LD in which the second abnormality has occurred corresponds to the determination means described in claim 7 (specifically, the determination means described in claim 8).

Further, depending on the image forming apparatus 10, a line having a width corresponding to one scanning line cannot be visually recorded, and the minimum width of the visible line on the formed image is the scanning line 2. It may be more than this amount. In such a case, when exposure recording of each abnormality determination patch is performed, as shown in FIG. 7B as an example, a plurality of (2 in FIG.
The LDs may be driven to light at the same time.

Further, in a mode in which the two LDs are simultaneously driven to be driven during the exposure recording of the individual abnormality determination patches, for example, the first and second LDs are set in the exposure recording of the abnormality determination patch with the identification number = 1. It is driven to turn on, and the second and third patterns are used during exposure recording of the abnormality determination patch with identification number = 2.
When the abnormal judgment patch of the abnormal judgment patch of the identification number = n is exposed and recorded (2
Although the (n-1) th and (2n) th LDs can be driven to light, in this case, for example, if a second abnormality occurs in the second LD, the abnormality of identification number = 1, 2 The density of the determination patch becomes extremely low, and “1” and “2” are input by the user via the input unit 84 as the identification numbers of the abnormality determination patch having the extremely low density.
Therefore, in the above-mentioned aspect, when the identification number of the abnormality determination patch having a remarkably low density is input, the information processing unit 80 commonly drives the lighting drive during the exposure recording of the abnormality determination patches having the plurality of input identification numbers. The LD thus obtained may be recognized as the LD having the second abnormality.

When the presence / absence of the LD having the second abnormality and the LD having the second abnormality have been recognized as described above, the information processing section 80 determines that the LD having the second abnormality has occurred.
Information indicating the presence or absence of the LD, and the LD in which the second abnormality has occurred
If there is, the information for identifying the LD is output to the video control unit 88 as abnormal beam designation information. The abnormal beam designation information is stored in the second abnormal beam storage unit 1 of the video control unit 88.
The second abnormal beam storage unit 110 receives the abnormal beam designation information and the second abnormal beam designation information is received.
The abnormal beam storage unit 110 notifies the abnormal cause determination unit 108. In this way, the second abnormal beam storage unit 110 corresponds to the storage means according to claim 10.

Further, in the LD having the second abnormality, the laser beam is not emitted from the LD, or the LD is not emitted.
Since the photoconductor drum 12 is not irradiated with the laser beam emitted from D, it cannot be used for image formation.
Therefore, when there is an LD having the second abnormality, the information processing unit 80 generates the video signal from the image data received from the outside, and when the LD having the second abnormality is generated during image formation. A video signal is generated so that it is not driven to be turned on. As a result, the power consumption of the image forming apparatus 10 can be reduced. Further, the operation of the APC video signal generator 96 may be controlled so that the APC is not performed on the LD having the second abnormality.

On the other hand, when it is notified that the abnormal beam designation information has been received, the abnormality cause discriminating unit 108 reads out the abnormal beam designation information once stored in the second abnormal beam storage unit 110, and the second abnormality is detected. If it is determined whether there is an LD that has occurred, and if it is determined that there is an LD that has the second abnormality, the LD that has the second abnormality is notified to the video signal changing unit 104.

When the abnormality cause discriminating unit 108 notifies the LD having the second abnormality, the video signal changing unit 104
Is an LD that emits a laser beam (for example, beam 2 and beam 4 in FIG. 9) whose scanning positions on the photoconductor drum 12 are adjacent to the laser beam emitted from the LD that has been notified. (Hereinafter, referred to as near light emitting LD) is recognized. Then, of the video signals input from the video signal selector 100, the two video signals corresponding to the near-light emitting LD are changed to the LD having the second abnormality.
Change according to the video signal corresponding to.

Specifically, the video signal changing unit 104 is
When the video signal corresponding to the LD having the second abnormality is monitored and the location where the signal level is changed so that the video signal drives the LD having the second abnormality to light up, Reference is made to the change in the signal level of the video signal corresponding to the near-light emitting LD at the location. And
As an example, as shown in FIG. 9B, a video signal (beam 2 and beam 4 in FIG. 9) corresponding to the near-light emitting LD is used.
Signal) has also changed so as to drive the LD to light up, as shown in FIG. 9C as an example, the time during which the proximity light emitting LD is driven to light up is a predetermined time (this predetermined time). It is desirable to change the time according to the time length of the portion where the signal level is changing so as to drive the LD to light up in the video signal corresponding to the LD having the second abnormality) Near light emission L
The signal level of the video signal corresponding to D is changed.

Further, as shown in FIG. 10 (B) as an example, the video signal changing section 104 has a signal level that drives the LD among the video signals corresponding to the LD having the second abnormality. When the video signal corresponding to the near-light emitting LD (the signals of the beam 2 and the beam 4 in FIG. 10) is at the signal level at which the LD is extinguished at the changing position, as shown in FIG. As shown in C), the near-light emitting LD is driven to be lit for a predetermined time (the LD having the second abnormality also during the above-mentioned predetermined time).
In the video signal corresponding to (1), it is desirable to change the signal level according to the time length of the portion where the signal level is changing so as to drive the LD to light.) Changing the signal level of the video signal corresponding to the near light emitting LD .

By changing the video signal corresponding to the near-light emitting LD as described above, even when there is an LD having the second abnormality in each LD of the LD array 50, the image quality is particularly improved. It is possible to form an image while suppressing the deterioration of the image quality in the middle / low density portion where the deterioration is easily visible without changing the main scanning speed or the process speed (sub-scanning speed) of the laser beam. in this way,
The video signal changing unit 104 corresponds to the modulation control means described in claim 12. Further, the above-mentioned processing by the video signal changing unit 104 corresponds to the processing “when it is determined that the second abnormality has occurred” described in claim 10.

Further, the abnormality cause discriminating unit 108 collates the information stored in the first abnormal beam storage unit 106 with the information stored in the second abnormal beam storage unit 110, and determines that the LD in which abnormality has occurred is the first LD. The first abnormal beam storage unit 106 stores the second LD as the LD having the second abnormality.
It is determined whether or not there is an LD that is not stored in the abnormal beam storage unit 110. The LD satisfying the above conditions has an abnormality (first abnormality) that the light amount of the laser beam emitted from the LD cannot be detected due to the optical axis shift of the half mirror 54, the lens 56, and the light amount sensor 58. Can be judged.

The LD in which the first abnormality has occurred is the LD in question.
Since the photoconductor drum 12 is irradiated with the laser beam emitted from the photoconductor drum 12, it can be used for image formation by performing APC in the forced control mode.
Does not notify the video signal changing unit 104 of the LD satisfying the above condition, and the LD having the first abnormality has occurred.
Is notified only to the information processing unit 80 (optical axis deviation notification signal in FIG. 4). As a result, the LD in which the first abnormality has occurred
With respect to, the lighting drive is continued with the drive control amount set in the forced control mode. This corresponds to the process “when it is determined that the first abnormality has occurred” described in claim 10.

When the information processing unit 80 is notified of the LD having the first abnormality, the LD having the first abnormality has been notified.
Based on the presence or absence of the LD having the second abnormality recognized based on the identification number input by the user who has verified the abnormality determination image (and the number of LDs having the second abnormality). , If necessary, exchange the LD array 50,
A message recommending that the optical axis of the optical component be adjusted, the light beam scanning device 16 itself be replaced, or that a maintenance service person be called is displayed on the display unit 82.

In the above description, an identification number is given to each abnormality determination patch of the abnormality determination image, and if there is an abnormality determination patch having a remarkably low density, the user is allowed to input the identification number attached to that patch. However, the present invention is not limited to this, and as an example, as shown in FIG. 11A, the identification number is not given to the abnormality determination patch, and as shown in FIG. The user may be allowed to input only the presence or absence of the determination patch. Usually LD
It is extremely rare that the LDs having the first abnormality and the LDs having the second abnormality are mixed in each LD of the array. When the information indicating that there is a patch is input, the L stored in the first abnormal beam storage unit 106 is stored.
The D may be regarded as the LD having the second abnormality, and the above-described processing such as changing the video signal may be performed.

[Second Embodiment] Next, a second embodiment of the present invention will be described. The same parts as those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted. As shown in FIG. 12, the video control unit 88 according to the second embodiment is replaced with the beam abnormality determination image data generator 102 described in the first embodiment, and a video signal generator 132 for SOS detection when an abnormality occurs. In addition, an SOS signal detection unit 134 when an abnormality occurs is provided.

When an abnormality occurs, the SOS detection video signal generator 132 has its input end connected to the output end of the timing measuring section 94 and the output end of the information processing section 80, and its output end input to the video signal selector 100. Connected to the end. In addition, the abnormality occurrence SOS signal detection unit 134 has an input end connected to the output end of the timing measurement unit 94, the output end of the information processing unit 80, and the output end of the SOS sensor 78, and the output end is the second abnormal beam. It is connected to the input end of the storage unit 110 and the SOS sensor 78.

The SOS sensor 78 according to the second embodiment.
The sensitivity is adjustable from the outside. The SOS sensor 78 whose sensitivity can be adjusted from the outside can be realized by adopting the following configuration, for example.

That is, the SOS sensor 78 shown in FIG.
Is provided with a single optical sensor 136, and the signal output from the optical sensor 136 is voltage-converted by the current-voltage conversion circuit 138 and input to the comparator 140. In addition, the comparator 14
The output signal of the threshold adjustment circuit 142 is also input to 0. In this SOS sensor 78, the current-voltage conversion circuit 13
8 is higher than the voltage level (threshold voltage) of the signal output from the threshold adjustment circuit 142, the signal output from the comparator 140 (that is, SOS). Signal) becomes low level, and when the sensor output is lower than the threshold voltage, the SOS signal becomes high level. Therefore, the sensitivity can be adjusted by changing the threshold voltage.

The SOS sensor 78 shown in FIG.
The optical sensors 14A and 144B are provided, and the optical sensors 14A and 144B are provided.
The signal output from 4B is voltage-converted by the current-voltage conversion circuit 146B and input to the comparator 148, but the signal output from the optical sensor 144A is voltage-converted by the current-voltage conversion circuit 146A and then the offset adjustment circuit 150. To the comparator 148 after the voltage level is offset by the offset adjustment circuit 150. In this SOS sensor 78, the voltage level of the signal output from the current-voltage conversion circuit 146A (sensor 1
Output) is higher than the voltage level (sensor 2 output) of the signal output from the current-voltage conversion circuit 146B, the SOS signal output from the comparator 148 becomes high level,
When the sensor 1 output is lower than the sensor 2 output, the SOS signal becomes low level. Therefore, the offset adjustment circuit 150
The sensitivity can be adjusted by changing the offset amount of the voltage level due to.

Next, as the operation of the second embodiment, the operation when the LD in which the APC mode is switched to the forced control mode occurs will be described. In the first embodiment, in the above case, the abnormality determination image is recorded on the paper P and the user is inspected, but in the second embodiment, instead of this, the SOS is used.
By detecting the laser beam with the sensor 78,
It is determined whether or not the second abnormality has occurred in each LD of the LD array 50 (whether the laser beam can be emitted).

That is, in the second embodiment, an abnormal beam detection instruction signal is output from the information processing section 80 in place of the abnormality determination image output signal, and the abnormal beam detection instruction signal is generated when an abnormality occurs in the SOS detection video signal. 132, video signal selector 100, SOS signal detector 13 when an abnormality occurs
4 and the timing measuring unit 94.

When an abnormal beam detection instruction signal is input, the SOS detection video signal generator 132 upon occurrence of an abnormality, based on the timing information input from the timing measuring section 94, in each main scan of the laser beam, SOS
A single LD is driven to be turned on during the period (a laser beam is emitted from the single LD), and the LDs to be turned on during the SOS period are sequentially switched in each main scan.
SOS at the time of occurrence of an abnormality for sequentially driving all the 0 LDs to be turned on (laser beams are sequentially emitted from all the LDs)
A video signal for detection is generated and output to the video signal selector 100.

When the abnormal beam detection instruction signal is input, the video signal selector 100 replaces the SOS detection video signal input from the SOS detection video signal generator 98 and replaces the SOS detection video signal with the SOS detection video signal. Video signal generator 1
The SOS detection video signal input from 32 is output when an abnormality occurs. As a result, SOS in each main scan
Each time a period comes, a different single LD is driven to be turned on.

As described above, a single L is generated during the SOS period.
When D is turned on and driven, and the LD that is driven to turn on is in a state where it cannot emit a laser beam, the SOS signal is not input in the main scanning cycle when the LD is turned on and driven. Therefore, when the abnormal beam detection instruction signal is input, the timing measuring unit 94 is based on the timing input before the input of the abnormal beam detection instruction signal even in the main scanning cycle in which the SOS signal is not input. Output pseudo timing information. As a result, the SOS detection video signal generator 132 at the time of occurrence of an abnormality detects the SOS at the time of occurrence of an abnormality based on the pseudo timing information output from the timing measuring unit 94 even when the SOS signal is not actually input. It is possible to continue generation and output of the video signal for use.

By the way, normally, a plurality of L's are provided during the SOS period.
Since D is lit and driven, if a single LD is lit and driven during the SOS period as described above, the sensitivity of the SOS sensor 78 becomes insufficient (specifically, the sensor output changes from the solid line to the broken line in FIGS. 13 and 14). It will decrease like
Although the SOS sensor is actually irradiated with the laser beam, it may be erroneously determined that the SOS sensor 78 is not irradiated with the laser beam. Therefore, when the abnormal beam detection instruction signal is input, the abnormality SOS signal detection unit 134 outputs a sensitivity change instruction signal for increasing the sensitivity of the SOS sensor 78 to the SOS sensor 78.

Thus, if the SOS sensor 78 has the structure shown in FIG. 13, the threshold voltage output from the threshold adjustment circuit 142 is reduced, and if the SOS sensor 78 has the structure shown in FIG. By reducing the offset amount of the voltage level by the offset adjusting circuit 150, S
The sensitivity of the OS sensor is increased, and it is possible to prevent an erroneous determination as to whether or not the SOS sensor 78 is irradiated with the laser beam.

When an abnormality occurs, the SOS signal detection unit 134 determines the timing at which the SOS signal is input from the SOS sensor 78, based on the timing information input from the timing measurement unit 94 in each main scan. Then, when the SOS signal is input from the SOS sensor 78 at the determined timing, the L driven by the main scanning cycle of this time is driven.
D determines that the laser beam can be emitted, and S
When the SOS signal is not input from the OS sensor 78, it is determined that the LD that has been driven to turn on in the main scanning cycle this time cannot emit the laser beam, that is, the second abnormality has occurred, The identification information is stored in the second abnormal beam storage unit 110. This makes it possible to detect the LD in which the second abnormality has occurred. The determination of the LD in which the second abnormality has occurred corresponds to the determination means described in claim 9.

In the above, L where the second abnormality has occurred
When detecting D, the single LD is driven to be turned on and the sensitivity of the SOS sensor 78 is increased during the SOS period. However, the present invention is not limited to this, and the LD in which the second abnormality has occurred is detected. At the time of detecting, the plurality of LDs may be driven to be turned on during the SOS period. in this case,
For example, in the first main scan, the first and second L
D is turned on and driven, and the second and third main scans are performed.
When the (2n-1) th and (2n) th LDs are driven to be driven by the nth main scan, such as when the second LD is driven to be driven, for example, the second LD is set to the second LD. If an abnormality occurs, the SOS signal is not input in each of the first and second main scans. Therefore, the SOS signal detection unit at the time of the abnormality occurs in the main scans of the plurality of times in which the SOS signal is not input. LDs that are commonly driven by scanning
It can be determined that the LD has the second abnormality.

In the above, the case where the median value of the drive amount control range is set as the drive amount in the forced control mode has been described, but the present invention is not limited to this. FIG. 15 shows another example of the configuration of the drive amount control unit 118. Note that FIG.
Shows only a portion different from the drive amount control unit 118 shown in FIG. 5, and the components of the drive amount control unit 118 corresponding to different LDs (laser beams) are denoted by reference characters A, B, ...

In FIG. 5 described above, the forced drive amount setting section 11 is used as the drive amount control signal used in the forced control mode.
Although the forced drive amount setting signal is input to the mode changing unit 124 from No. 4, in the drive amount control unit 118 shown in FIG. 15, instead of this, the drive amount control unit that immediately performs APC is performed. The drive amount control signal set in 118 is input to the mode changing unit 124 (for example, the mode changing unit 124 of the drive amount control unit 118B receives APC as the drive amount control signal used in the forced control mode immediately before. The drive amount control signal set by the drive amount control unit 118A is input). Note that FIG.
In the above, the signal line connecting the individual drive amount control units 118 to each other corresponds to the second light amount control means according to claim 4.

Since the LD array 50 manufactures each LD by the same semiconductor process, the light source drive amount of each LD-
The emitted light amount characteristics do not differ greatly, and in most cases, the LD drive amount for making the light amount of the laser beam emitted from each LD a predetermined value is also similar. Therefore, as described above, by using the drive amount control signal set by the drive amount control unit 118 immediately before APC as the drive amount control signal used in the forced control mode, the LD driven in the forced control mode is used. Since the light quantity of the laser beam emitted from the LD array can be controlled to a value close to the light quantity setting value, when a part of the LDs of the LD array 50 is driven to be lit in the forced control mode, an image formed is The degree of image quality deterioration can be reduced.

FIG. 16 shows another example of the structure of the drive amount control section 118. The drive amount control unit 118 shown in FIG. 16 includes an average value calculation unit 152.
2, the drive amount control signals set by all the drive amount control units 118 are input, and the mode change signals input by the mode changing means 124 of all the drive amount control units 118 are input. . The average value calculation unit 152 uses the drive amount control unit 118 in which the APC is completed in the light amount control mode without switching the APC mode to the forced control mode based on the mode change signal input from each drive amount control unit 118. The average value is calculated using only the set drive amount control signal. A signal corresponding to the average value of the drive amount control signals output from the average value calculation unit 152 is input to the mode changing means 124 of all the drive amount control units 118 as a drive amount control signal used in the forced control mode. It The average value calculation unit 152 corresponds to the second light amount control means described in claim 5.

Even when the drive amount control unit 118 is configured as described above, the light amount of the laser beam emitted from the LD driven in the forced control mode is set as in the drive amount control unit 118 shown in FIG. Since the size can be controlled to be close to the value, it is possible to reduce the degree of image quality deterioration of the image formed when a part of the LDs in the LD array 50 is driven to be driven in the forced control mode.

Further, FIG. 17 shows another example of the configuration of the drive amount control section 118. In FIG. 5, a forced drive amount setting signal that defines the LD drive amount in the forced control mode and a drive amount upper limit level setting signal that defines the upper limit of the drive amount control range in the light amount control mode are separately provided to the drive amount control unit 118. Although it is configured to be input, the drive amount control unit 118 shown in FIG.
In the configuration, only the forced drive amount setting signal is input, and this forced drive amount setting signal is set to the same level as the level of the drive amount control signal corresponding to the upper limit of the drive amount control range in the light amount control mode. ing. Note that in FIG. 17, the forced drive amount setting unit 11 that outputs the forced drive amount setting signal
Reference numeral 4 corresponds to the second control means described in claim 6.

Therefore, the drive amount control section 118 shown in FIG.
Then, as shown by beam 4 in FIG. 18, when the drive amount control signal reaches the level corresponding to the upper limit of the drive amount control range in the light amount control mode, the APC mode is switched to the compulsory control mode. Is maintained at a level corresponding to the upper limit of the drive amount control range.

Further, the case has been described above where it is monitored whether the drive amount control signal (LD drive amount) has reached the upper limit of the control range, and if it has reached the upper limit of the control range, the forced control mode is switched to. However, the present invention is not limited to this, and also monitors whether or not the drive amount control signal (LD drive amount) has reached the lower limit of the control range, and switches to the forced control mode when the lower limit of the control range is also reached. You may do it.

Further, in the above, when the level of the drive amount control signal exceeds the predetermined range during execution of APC, it is determined that an abnormality has occurred, the APC mode is switched to the forced control mode, and each LD of the LD array 50 is switched. It is determined whether or not the laser beam can be emitted from the laser beam, but the present invention is not limited to this. For example, the light amount sensor 58 responds to a change in the level of the drive amount control signal during execution of APC.
It may be possible to determine whether or not an abnormality has occurred based on the change in the light amount value detected by the method.

Further, in the above, L in which the second abnormality has occurred
When it is detected that D is present, the video signal changing unit 10
Although the case where the deterioration of the image quality of the image is suppressed by changing the video signal corresponding to the near-light emitting LD according to 4 has been described, the present invention is not limited to this, and a part of the LD of the LD array 50 is used. As a countermeasure when the second abnormality occurs, a plurality of known countermeasures can be executed so that the image forming apparatus 1
When 0 is configured and it is detected that there is an LD in which the second abnormality has occurred, as shown in FIG. 19 as an example, a plurality of types of feasible countermeasures and respective countermeasures are executed. The display unit 8 displays a screen notifying the difference from the normal time.
It is also possible to display it on No. 2 and have the user select the most desirable countermeasure through the input unit 84, and execute the countermeasure selected by the user. Further, the above screen may be displayed at the time of initial setting, and the user may be allowed to select in advance what to do when a second abnormality occurs in some LDs.

Further, the measures to be taken when it is detected that there is the LD in which the first abnormality has occurred are limited to the continuous lighting drive of the LD with the drive control amount fixedly set in advance. Instead, in the forced control mode, the image forming apparatus 10 is configured so that an arbitrary drive control amount can be set from a plurality of types of drive control amounts, and although not shown, it can be executed similarly to FIG. It is most desirable for the user to display on the display unit 82 a screen for notifying a plurality of types of measures (specifically, a plurality of types of drive amount control amounts that can be set) and the difference between the measures at the time of executing the respective measures. A countermeasure may be selected via the input unit 84, and the countermeasure selected by the user may be executed (the LD having the first abnormality is driven by the selected drive amount control amount). The above matters correspond to the invention of claim 13.

[0133]

As described above, according to the first aspect of the invention, the light amount detection value by the light amount detecting means becomes a predetermined value for each of the plurality of light beams for scanning the object to be scanned. One of the light quantity control means selects the light quantity by changing the light source drive quantity by the negative feedback control, or the second light quantity control means selects the light quantity by setting the light source drive quantity to a predetermined value. Therefore, even if the light amount of a part of the light beams cannot be detected, it is possible to form an image without causing a failure of the light source and a significant deterioration of the image quality. .

According to a second aspect of the present invention, in the first aspect of the invention, the light amount of the plurality of light beams is sequentially controlled by the first light amount control means, and the first light amount control means changes the light source drive amount. If the light source drive amount deviates from the predetermined range during the process, the light amount of the light beam is controlled by the second light amount control means. It is possible to further suppress the deterioration of the image quality of the captured image.

According to the invention described in claim 3, in the invention described in claim 2, since the central value of the predetermined range is set as the light source drive amount, in addition to the above effects, the image quality deterioration of the image formed on the object to be scanned. The effect is that the degree can be reduced.

According to a fourth aspect of the present invention, in the second aspect of the invention, the light source drive amount is substantially equal to the light source drive amount of another light beam set by the first light amount control means before the light beam. Since the same value is set, in addition to the above effect, there is an effect that the degree of image quality deterioration of the image formed on the scanned object can be reduced.

According to a fifth aspect of the present invention, in the second aspect of the present invention, as the light source drive amount, the first light amount control is performed for the light beam which is not judged to be abnormal by the selecting means among the plurality of light beams. By setting a value approximately equal to the average value of the light source drive amount set by each means, in addition to the above effect, there is an effect that the degree of image quality deterioration of the image formed on the scanned object can be reduced. .

According to a sixth aspect of the invention, in the second aspect of the invention, the light source drive amount at the time point when the selection means determines that the light source drive is abnormal is set as the light source drive amount. This has the effect of reducing the degree of image quality deterioration of the image formed on the body.

According to a seventh aspect of the invention, in the invention according to any one of the second to sixth aspects, when the selection means determines that there is an abnormality or when the light beam is emitted from the light source after the light amount control is completed. When the light intensity detection value of is out of the predetermined light intensity range, it is determined whether or not multiple light sources are capable of emitting light beams. Can be distinguished well,
Has the effect.

According to the invention described in claim 8, in the invention described in claim 7, light beams are emitted from each of a plurality of light sources to form a predetermined evaluation image, and the user evaluates the evaluation image visually. In addition to the above-mentioned effect, the plurality of light sources can be used to input the evaluation results, and it is determined whether or not the plurality of light sources can emit light beams based on the input evaluation results. It is possible to reliably judge whether or not the injection can be performed.

According to a ninth aspect of the invention, in the seventh aspect of the invention, a plurality of light beams are respectively detected by the light detecting means provided separately from the light amount detecting means and capable of detecting a plurality of light beams. Based on whether or not the plurality of light sources are capable of emitting light beams, it is determined whether or not the plurality of light sources are capable of emitting light beams. This has the effect of making a decision without bothering the user.

According to a tenth aspect of the present invention, in the invention according to any one of the seventh to ninth aspects, when it is determined that a plurality of light sources can emit light beams, a plurality of light beams are emitted. At least one of the plurality of light sources determines that at least one of the plurality of light sources is in a state in which the light beam cannot be emitted, and at least one of It is determined that the second abnormality in which the light beam is not emitted from each light source is occurring, and the first abnormality is determined as the countermeasure for the abnormality determined to be occurring, and the second abnormality. Since different processing is performed depending on the case where it is determined that the occurrence has occurred, in addition to the above-described effects, there is an effect that it is possible to reliably reduce image quality deterioration when an abnormality occurs.

According to the eleventh aspect of the present invention, in the invention of the tenth aspect, when it is determined that the second abnormality has occurred, the light beam not emitted from the light source is specified, and the specified light beam is identified. Since the information is stored, in addition to the above effect, there is an effect that the information stored in the storage means can be used for coping with the second abnormality.

According to a twelfth aspect of the present invention, in the invention according to the tenth aspect, at least one light beam whose scanning position is close to the light beam specified as a light beam not emitted from the light source is a specified light beam. Based on the modulation signal for modulating the beam, the light source emits light near the timing at which the specified light beam should be emitted from the light source, or even during the period when the light source is not originally emitted. Since the modulation of at least one light beam is controlled so as to be emitted from
When the above abnormality occurs, the image quality deterioration can be suppressed to the minimum without significantly changing the processing in the image forming apparatus.

According to a thirteenth aspect of the present invention, in the aspect of the tenth aspect of the invention, when it is determined that the first abnormality or the second abnormality has occurred, a plurality of countermeasures for the abnormality are presented to the user, In addition to the above-described effect, the countermeasure selected by is taken, which has the effect that the user can take the most desirable countermeasure.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an image forming apparatus according to an exemplary embodiment.

FIG. 2 is a perspective view showing a schematic configuration of a light beam scanning device.

FIG. 3 is a block diagram showing a schematic configuration of a control unit of the image forming apparatus.

FIG. 4 is a block diagram showing a schematic configuration of a video control unit according to the first embodiment.

FIG. 5 is a block diagram showing an example of a schematic configuration of a drive amount control unit.

6 is a timing chart showing an example of APC in the drive amount control section of FIG.

FIG. 7 is an image diagram showing an example of an on / off pattern of each laser beam for recording an abnormality determination image.

8A is an image diagram showing an example of an abnormality determination image, and FIG. 8B is an image diagram showing an example of information displayed on the display unit when the abnormality determination image of FIG.

FIG. 9 is an explanatory diagram showing an example of changing the on / off timing of the laser beam when a part of the laser beam is not applied to the photoconductor.

FIG. 10 is an explanatory diagram showing an example of changing the on / off timing of the laser beam when a part of the laser beam is not applied to the photoconductor.

11A is an image diagram illustrating another example of the abnormality determination image, and FIG. 11B is an image diagram illustrating an example of information displayed on the display unit when the abnormality determination image in FIG.

FIG. 12 is a block diagram showing a schematic configuration of a video control unit according to the second embodiment.

FIG. 13 is a diagram showing an example of an SOS sensor whose sensitivity can be adjusted from the outside.

FIG. 14 is a diagram showing another example of the SOS sensor whose sensitivity can be adjusted from the outside.

FIG. 15 is a block diagram showing another example of a schematic configuration of a drive amount control section.

FIG. 16 is a block diagram showing another example of a schematic configuration of a drive amount control section.

FIG. 17 is a block diagram showing another example of a schematic configuration of a drive amount control section.

18 is a timing chart showing an example of APC in the drive amount control section of FIG.

FIG. 19 is an image diagram showing an example of a display screen when a failure occurs.

[Explanation of symbols]

10 image forming apparatus 12 Photosensitive drum 16 Light beam scanning device 50 LD array 54 half mirror 58 Light intensity sensor 78 SOS sensor 80 Information Processing Department 102 Beam abnormality determination image data generator 104 Video signal changing section 108 Abnormality cause determination unit 110 Second abnormal beam storage unit 114 Forced drive amount setting section 120 amplifier 122 Sample and hold circuit 124 Mode changing means 126 OR circuit 128 comparator 130 latch 132 Video signal generator for SOS detection when abnormality occurs 134 SOS signal detector when an abnormality occurs

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 2C362 AA07 AA13 AA53 AA55 BA04                       BA48 BA51 CB73 EA07                 5C051 AA02 CA07 DA02 DB02 DB07                       DB22 DB24 DB30 DC03 DE29                       EA01                 5C072 AA03 BA20 HA02 HA06 HA09                       HA13 HB01 HB04 QA14 XA05

Claims (13)

[Claims] 1. An image forming apparatus for forming an image on an object to be scanned by scanning an object to be scanned with a plurality of light beams emitted from a plurality of light sources. A light amount detection unit arranged at a position where a part of each light beam is incident, for detecting the light amount of the incident light beam, and a light source drive amount is negatively fed back so that the light amount detection value by the light amount detection unit becomes a predetermined value. By changing it by control,
First light amount control means for controlling the light amount of the light beam, second light amount control means for controlling the light amount of the light beam by setting the light source drive amount to a predetermined value, and each of the plurality of light beams An image forming apparatus comprising: a first light amount control unit and a second light amount control unit for selecting which light amount control is to be performed. 2. The light source is controlled by the selection means while the light quantity of the plurality of light beams is sequentially controlled by the first light quantity control means, and the light source drive quantity is being changed by the first light quantity control means. If the drive amount is out of the specified range,
2. The light amount control of the light beam by the first light amount control unit is judged to be abnormal, and the light amount control of the light beam is performed by the second light amount control unit. Image forming apparatus. 3. The image forming apparatus according to claim 2, wherein the second light amount control means sets a median value of the predetermined range as the light source drive amount. 4. The second light quantity control means sets the light source drive quantity to a value substantially equal to the light source drive quantity of another light beam set by the first light quantity control means before the light beam. The image forming apparatus according to claim 2, wherein the setting is performed. 5. The second light quantity control means sets a first light quantity as a light source drive quantity for a light beam that has not been determined to be abnormal by the selection means among the plurality of light beams.
3. A value which is substantially equal to the average value of the light source drive amount set by each of the light amount control means is set.
The image forming apparatus described. 6. The second light quantity control means sets, as the light source drive quantity, a light source drive quantity at a time point when the selection means judges an abnormality.
The image forming apparatus described. 7. When a light beam is emitted from the light source when the selection unit determines that there is an abnormality, or after the light amount control by at least one of the first light amount control unit and the second light amount control unit is completed. A light amount detection value by the light amount detection unit is out of a predetermined light amount range, further comprising a determination unit for determining whether or not each of the plurality of light sources can emit a light beam. Claim 2
The image forming apparatus according to claim 6. 8. The determination means requests each of the plurality of light sources to emit a light beam to form a predetermined evaluation image and to prompt the user to visually evaluate the evaluation image and input the evaluation result. The image forming apparatus according to claim 7, wherein it is determined whether or not each of the plurality of light sources can emit a light beam based on the evaluation result input through the input unit. 9. The determination means is based on whether or not each of the plurality of light beams is detected by a light detection means that is provided separately from the light amount detection means and is capable of detecting the plurality of light beams. The image forming apparatus according to claim 7, wherein it is determined whether each of the plurality of light sources can emit a light beam. 10. The first determining unit determines that at least one of the plurality of light beams does not enter the light amount detecting unit when determining that the plurality of light sources can emit light beams. When it is determined that an abnormality has occurred and it is determined that at least one of the plurality of light sources is incapable of emitting a light beam, the at least one light source does not emit a light beam. It is determined that
10. The image formation according to claim 7, wherein different processing is performed depending on whether it is determined that the second abnormality has occurred or when it is determined that the second abnormality has occurred. apparatus. 11. The determining means, when determining that the second abnormality has occurred, specifies a light beam that is not emitted from a light source, and stores information for identifying the specified light beam in the storage means. The image forming apparatus according to claim 10, wherein: 12. When modulating a light beam emitted from a light source to form an image, a scanning position on the object to be scanned is close to a light beam specified as a light beam not emitted from the light source. For at least one light beam, the time during which the specified light beam is emitted from the light source is extended near the timing at which the specified light beam should be emitted from the light source, based on the modulation signal for modulating the specified light beam. The modulation control means for controlling the modulation of the at least one light beam is further provided so that the light is emitted from the light source even during a period when the light is not originally emitted from the light source. Image forming apparatus. 13. When the determination means determines that the first abnormality or the second abnormality has occurred, the determination means presents the user with a plurality of countermeasures for the abnormality determined to have occurred, and The image forming apparatus according to claim 10, wherein the selected countermeasure is performed.