JP5113024B2 - LASER SCAN UNIT, PHOTOSENSITIVITY SENSITIVITY EVALUATION DEVICE FOR PHOTOSENSOR HAVING THE UNIT, AND PROGRAM FOR CONTROLLING THE UNIT - Google Patents

Description

  The present invention relates to a laser scanning unit, a sensitivity characteristic evaluation apparatus for a photosensitive member having the unit, and a program for controlling the unit.

  In recent years, image forming apparatuses such as digital electrophotographic copying machines and laser printers are required to have high resolution and high-speed print output. For this reason, rotation of the photosensitive member at a high linear velocity is required. Currently, the polygon mirror for scanning this photosensitive member has a rotational speed of about 30,000 rpm, and has almost reached its limit. For this reason, a multi-beam scanning exposure method is employed in which a plurality of light sources are arranged in parallel in the sub-scanning direction of the photosensitive member without increasing the number of rotations of the polygon mirror, and a plurality of beams are scanned in one scan in the main scanning direction. In the multi-beam scanning exposure system, a multi-beam recording head is used. With this multi-beam recording head, the rotational speed of the polygon mirror can be reduced to about 1/2 as compared with a one-beam light source. As a result, exposure scanning, which was impossible in the case of one beam, is possible, and as a result of a margin in rotational speed, the linear velocity of the photosensitive member can be further increased.

On the other hand, in an image forming apparatus that uses the above-described photosensitive member at a high linear velocity, the exposure by laser scanning increases, for example, to about 4 W / cm ^2, and the time for one point to be exposed by one scan is 50 ns. is characterized a longitudinal and short. In order to measure the sensitivity characteristics of the photosensitive member under the same conditions (scale) as the exposure power and exposure time, there is only a method of laser scan exposure under the same measurement conditions. When the laser scan unit (hereinafter referred to as “LSU”) used at this time is a single beam, it is emitted from a laser diode element (hereinafter referred to as “LD element”) and linearly enters the polygon mirror. Design in layout is possible. In contrast, in a multi-beam LSU (except in the case of a laser diode array), when one of the beams is laid out in such a straight line, the remaining beam is optically turned by an optical element (component) several times, and the polygon It is necessary to design the layout so as to be incident on the mirror. In addition, in a dedicated measurement apparatus, not only simultaneous multi-beam exposure with the same wavelength but also an LSU equipped with a plurality of LD elements with different wavelengths may be used. This is one LSU, which can evaluate the sensitivity characteristics of the photoconductor with respect to different wavelengths, and is also desired in terms of operability and economy. In this case, it is essential to arrange the LD elements separately for each different emission wavelength. Therefore, in an LSU equipped with a plurality of LD elements, the beam of the other LD element must be an optical element (component). Will be incident multiple times on the polygon mirror. Further, when it is desired to change the size of the beam irradiated to the photosensitive member, a plurality of apertures having different apertures may be replaced as necessary. Furthermore, if you want to reduce the light power applied to the photoreceptor more, a neutral density filter is inserted in the optical path, but a thin film is formed on the laser incident surface of these optical components, causing interference and laser driving conditions. And the relationship between the optical power (IL characteristics) may be distorted. In such a filter, the surface accuracy may also affect the IL characteristics. Normally, I-L characteristic is highly linear. However, as in Patent Document 1, for example, the aperture is changed in the optical path, or even in the same aperture, due to the dimensional tolerance of the aperture and the aperture holder, the position is slightly different from the previous time depending on how to apply force during setting, etc. sometimes -L characteristic itself would change.

JP 2006-123480 A

  In the exposure by the laser scan unit (LSU), first, the optical power applied to the irradiation position on the surface (image surface) of the photoconductor to be measured is determined, and laser drive is performed to reach the image surface with the optical power. The condition is determined from the IL characteristic relational expression. The I-L characteristics of this LSU may change when the optical components placed in the optical path are replaced. Normally, the I-L characteristic is highly linear, but the I-L linear relationship may be distorted due to deviations from the original set position of the optical parts such as apertures and dimming elements, or changes in the optical parts themselves. is there. As a result, the scanning conditions of the laser scanning unit differ, and particularly in an evaluation apparatus for evaluating the characteristics of the photoreceptor, a problem arises in its reliability. The object of the present invention is to solve such problems all at once.

In order to solve the above problems, the present invention has the following solutions.
[1] A laser scan unit (LSU) equipped with a plurality of laser light sources ,
The laser scanning unit, a microprocessor, memory, interface, display device, and a microcomputer system comprising a key input device, is controlled so as to light the respective laser light sources to the light intensity L by the laser driving condition I,
Have the laser light sources and various optical components, and,
A detection unit for detecting a change of the optical component,
Based on the instruction from the microcomputer system, one in a position a and position after the optical component passing before the laser beam is incident on the polygon mirror, of said plurality of laser sources after the optical component passing One of so as to totally by receiving a laser beam, is configured to have a moving means for causing movement of the light detection means to the laser beam on the optical path, and
When the detection unit detects a change in the optical component,
Changing two or more of the laser driving conditions I of the laser light source affected by the change of the optical component, and detecting the intensity L of each obtained light by the light detecting means moved by the moving means ;
The microcomputer system acquires a data pair (I, L) of the two or more changed I and the intensity L of each light obtained by each I as a data string, and the two or more acquired data strings And the IL characteristic data stored in the memory in the microcomputer system ,
When the difference exceeds a certain allowable standard, the light intensity L of the laser light source is calculated based on the laser driving condition I using the newly derived IL characteristic relational expression based on the acquired data. A laser scanning unit characterized by controlling .
[2] The light detecting means is a photodiode, said one optical component is intended to attenuate the intensity of the light, or not to determine the image plane beam size, which causes some or all of the laser beam counterclockwise Isa The laser scan unit according to [1], wherein
[3] The laser scanning unit according to [1] or [2], wherein the optical component is at least one selected from a neutral density filter, a splitter, or an aperture.
[4] The light detecting means is a photodiode,
The laser scanning unit is controlled to light each laser light source at the light intensity L according to the laser driving condition I using the following relational expression (1):
The microcomputer system instructs the mobile unit to move in the optical path of the laser beam on the basis of the detection signal of the optical component changes more affected changes before Symbol optics of the photodiode, a laser Two or more driving conditions I are changed, and the light intensity L of the laser beam of the laser light source is detected by the photodiode, and the changed I and L obtained by this I are a data pair (I, L) The data string is acquired, and the IL characteristic data obtained from the acquired data string is newly approximated by the relational expression (1), according to any one of [1] to [3] Laser scan unit.
I = a _n L ⁿ + a _n-1 L ^n-1 + (1)
(L is the optical power at the image plane position (unit is mW), I is the laser driving condition (when the laser driving condition I is current, the unit is mA, and the current value is converted into a voltage value) V), and an, an-1,... Are coefficients of each term, where n is an integer of 1 or more.)
[5] The laser driving condition I to be changed by two or more is in a range from the threshold Ith (lower limit) of the laser driving current to Iop (upper limit) for outputting the rated power, and a plurality of I in the range are changed. The laser scan unit according to any one of [1] to [4], wherein a data string of a data pair (I, L) of I and L is acquired.
[6] Any one of [1] to [5], wherein, by the comparison, if the data pair includes a data pair that deviates from a predetermined acceptance criterion , a warning is displayed on the display device . The laser scan unit described in 1.
[7] If there is a data pair that deviates from the predefined acceptance criteria for the data pair by the comparison,
The laser scanning unit uses the approximated expression of the IL characteristic relational expression based on a fifth order polynomial as the following relational expression (2) for the acquired data string, and the laser light source affected by the change of the optical component the laser scanning unit according to any of characterized in that to control the intensity of the light L [1] to [3].
I = a _n L ⁿ + a _n-1 L ^n-1 + (2)
(L is the optical power at the image plane position (unit is mW), I is the laser driving condition (when the laser driving condition I is current, the unit is mA, and the current value is converted into a voltage value) V), and an, an-1,... Are coefficients of each term, where n is an integer of 1 or more.)
[8] A sensitivity characteristic evaluation apparatus for a photoreceptor having the laser scan unit according to any one of [1] to [7].
[9] The change of the optical components in the laser scan unit (LSU) is detected by the detector,
Based on a command from the microcomputer system, a position before the laser beam is incident on the polygon mirror, and a position after passing through the optical component, of the plurality of laser light sources after passing through the optical component. Move the light detection means on the optical path of the laser to receive all the laser beam,
The intensity L of the irradiation light is measured, the laser driving condition I and the intensity L are changed by changing two or more I, and a data pair (I, L) of the changed I and L obtained by this I ) Data columns,
The two or more acquired data strings and the data pair (I, L) obtained from the IL characteristic relation stored in the memory in the microcomputer system are represented as L of each data pair having the same value of I. Compare with the value of
It is determined whether the difference from the data of the IL characteristic relational expression stored in the memory by the comparison exceeds a predetermined permissible standard, and if the difference exceeds the predetermined permissible standard, The power of the laser light source affected by the optical component changed by the IL characteristic relational expression obtained by two or more data strings is controlled, and if the difference does not exceed the predetermined allowable standard, the memory is stored in the memory. A program for controlling a laser scan unit, which controls the laser scan unit to control the power of a laser light source affected by an optical component changed by a stored IL characteristic relational expression.

It has a mechanism to detect each time an optical component such as an optical component such as a neutral density filter and an aperture that changes the beam size is replaced or inserted, and is usually located at a position off the optical path from the microprocessor. LSU has a mechanism to move and place a photodiode (PD) with a light-receiving surface larger than the beam cross-sectional area at a position just before the laser beam enters the polygon mirror so that the entire beam is received. When the microprocessor detects the replacement of the optical component, the detected signal is used as a trigger to move the PD to the optical path, and the laser is turned on under a plurality of laser driving conditions. acquiring the optical power data, it is programmed to compare the I-L characteristic data which has been saved by acquiring the data previously in memory It is to have, with the optical components of the motion, the replacement can be confirmed whether a change in the I-L characteristic occurs.

Further, by examining the IL characteristics only in the range of driving conditions where problems are likely to occur in the IL characteristics, data is acquired within the driving conditions range so that problems can be detected and solved quickly. The problem can be solved in a short time by obtaining the -L characteristic relational expression.
Furthermore, when the replacement of optical components is detected, the microprocessor mounted on the LSU automatically acquires the IL characteristics as (I, L) data strings, and the IL before the change (before the replacement of the optical components). Compared with the data based on the characteristic relational expression, if there is a difference, a warning is displayed on the display device, and the user can take necessary measures.
Furthermore, when the replacement of optical components is detected, the microprocessor installed in the LSU automatically acquires the I-L characteristics as an (I, L) data string, and compares it with the state set up first. In this case, an accurate exposure power can be given at any time by obtaining an IL characteristic relational expression between the optical power of the image plane and the driving condition.
Further, when the IL characteristic is distorted and the IL characteristic curve is approximated by a new approximate expression, it is approximated by a fifth-order polynomial, and even with the distorted IL characteristic, an accurate I-L characteristic is obtained. The amount of exposure can be controlled by using an L characteristic curve.
Furthermore, by using the above-described LSU, it is possible to provide a photoconductor sensitivity evaluation apparatus that irradiates an object with accurate exposure power at any time.

Hereinafter, embodiments of the LSU of the present invention will be described in detail with reference to the drawings.
In the present invention, the I-L characteristic I is defined as the laser driving condition, and L is described as the optical power of the laser beam when the surface of the photosensitive member is irradiated under the driving condition. In the present specification, “optical component” refers to a component that attenuates the intensity of light, a component that determines an image plane beam size, a component that transmits or reflects part or all of the beam, and the like.
This optical component exists between the light source and the scanning system (polygon mirror). For example, as shown in FIG. 1, apertures 31, 31 ′, neutral density filters 32, 32 ′, 51, 51 ′, a splitter 33, a mirror 34, and the like can be given.
As I, there are a case where a laser drive current (If) is used and a case where a monitor current (Im) of a laser diode (abbreviated as LD) is used. When the above-mentioned If or Im is used as the laser driving condition I, for example, mA is used as the unit. When the current value is converted into a voltage value and used as the drive condition, V is used as the unit of the drive condition I, for example.

  The laser scan unit (LSU) of the present invention is an LSU equipped with a plurality of LDs. Each LD may have the same wavelength or a different wavelength. As shown in FIG. 1, this LSU is equipped with a microcomputer 1. In the present invention, the LSU is controlled to turn on the laser unit according to the laser driving condition I from the IL characteristic relational expression stored in the memory 12 of the microcomputer 1. The LSU according to the present invention includes a detector (not shown) that detects a change in the optical component 3 such as the neutral density filter 32, 32 ′, 51, 51 ′ or the aperture 31, 31 ′ for each laser, and a photo The diode (PD) includes moving means 4 that moves so as to receive the entire beam from the laser unit.

  The microcomputer 1 instructs the moving means 4 on the basis of the change detection signal of the optical component 3, and moves the optical power L (beam intensity) of the laser according to the change after passing through the optical component 3 to the movement. A data pair (I, L) of the laser driving condition I and the optical power L detected by a photodiode (not shown) mounted on the means 4 is collected in the memory and stored in the memory. The power L of the laser related to the changed optical component is controlled by comparing with the data of the IL characteristic relational expression.

  As shown in FIG. 1, the present invention has two or more laser units LD1, LD2,... As a light source (for example, FIG. 1 shows an example using two laser units LD1 and LD2). ). In this laser unit, an LD driver 54 incorporating an APC (Auto Power Control) loop for receiving a part of light emitted from the LD element and controlling the light emission state of the LD for each laser unit, 54 'is connected. Each laser unit preferably has a temperature control circuit, for example, and it is preferable to use a laser unit in which the LD emission state is stabilized by suppressing the temperature change of the LD element (that is, temperature control). In the laser scanning unit of the present invention, the laser driving condition I defined by the IL characteristic relation stored in the microcomputer 1 is sent to the DC voltage generators 55 and 55 ′ related to the unit LD of each laser, This is input to the LD drivers 54 and 54 '. In the case of APC, this signal becomes the reference value of the monitor current when the LD is lit, and the LD is driven so that the monitor current (photocurrent) from the LD becomes equal to this reference value. Accordingly, each LD is controlled to be irradiated with the power controlled for each LD.

In each laser, the irradiation light from the LD element first passes through apertures (optical parts that determine the size of light passing therethrough) 31, 31 ′.
The laser beam that has passed through the apertures 31 and 31 ′ passes through the optical components 3 such as the ND filters 51 and 51 ′, the neutral density filters 32 and 32 ′, and the beam splitter 33, and then operates at a predetermined rotational speed. Is rotated and scanned. Thereafter, the light passes through the scanning optical system 101 and is irradiated onto the photosensitive member 102. Examples of components of the scanning optical system 101 include an fθ lens, a cylindrical lens, and a folding mirror. In addition to these scanning optical systems, the scanning system (comprising the scanning optical system 101 and the polygon mirror 100) can have a synchronization detection sensor and the like necessary for scanning.

  As shown in FIG. 1, the main body of the microcomputer system used in the LSU of the present invention has an MPU 11, a memory 12, and an I / F (interface) 13, and further includes a display unit 14 and an input unit 15. It is comprised. Via the I / F 13, a laser drive condition signal I is transmitted to the DC voltage generator so that each laser unit can be driven under the laser drive condition I, and a control signal for on / off control is transmitted to each laser driver. . Further, the moving unit 4 used in the LSU of the present invention is mounted with a photodiode PD411 so that the light intensity (also referred to as optical power) of the laser beam immediately before entering the polygon mirror 100 is obtained. As described above, the LSU of the present invention measures the optical power of the laser beam before passing through the optical component 3 and before entering the polygon mirror 100. Therefore, the moving unit 4 used in the present invention is used to move the photodiode PD411. The movement of the moving unit 4 is controlled by the microcomputer 1 described above. The moving unit 4 only needs to be able to control the moving distance to a position where the PD 411 can receive the entire beam size. For example, as shown in FIG. 1, the moving unit 4 includes a rotary solenoid 42 and a slider 41 to which the photodiode PD 411 is fixed. Furthermore, it can be configured to have an amplifier 43 that converts the photocurrent of the PD 411 by IV conversion and amplifies it. The moving unit 4 is placed in the optical path from the LD (LD1 and LD2 in FIG. 1) to the polygon mirror 100 by the microcomputer 1, for example, the neutral density filter 32, 32 ′ or the aperture 31 of the optical component 3. , 31 ′, that is, when the replacement of these optical components 3 is detected, the moving unit 4 (the rotary solenoid 42 constituting the moving unit in the configuration shown in the LSU layout shown in FIG. 1) is transmitted via the I / F 13. By moving the slider 41, the slider 41 on which the PD 411 is placed is moved in the optical path of the laser unit related to the change of the optical component 3.

  The IL characteristic associates the relationship between the driving condition I of each laser unit and the optical power L on the image plane. That is, in the present invention, the driving condition I applied to each LD element and the light emitted from the LD element are thereby deflected by the polygon mirror 100 and scanned after passing through optical components such as an aperture and a neutral density filter. It is expressed as a set of data pairs (Ii, Li) with the optical power Li that passes through the optical system 101 and is irradiated onto the image surface (irradiation surface of the photosensitive member). In the present invention, instead of the optical power Li on the image plane, the I-L characteristic is obtained by the optical power L after passing through the optical component and before the polygon mirror irradiation (preferably just before the polygon mirror irradiation). This measurement of the light intensity (light power) before the scanning system is because it is not constant where the irradiation position of the beam comes due to reflection by the polygon mirror on the image plane. For this reason, the optical power received by the PD411 differs from the optical power reaching the image plane, so the ratio of the optical power received by the PD411 and the power of the image plane = [image plane power / PD photocurrent. ] In advance, the optical power data of the image plane can be obtained at any time by multiplying this ratio by the photocurrent (= optical power) received by the PD 411. In order to accurately perform this conversion, it is necessary that the light receiving surface size of the PD 411 is larger than the beam size (cross section) and all light can be received. Although a commercially available light meter sensor that can directly display optical power can be used as the PD, in consideration of size and cost, this application is equipped with an amplifier 43 that IV converts and amplifies the PD411 photocurrent in the LSU. did. Therefore, the optical power L is detected from the output of the photocurrent (proportional to the optical power at that position in the optical path) by the photodiode (PD 411) placed on the slider 41 placed after passing through the optical parts and before the polygon mirror irradiation. By doing so, it is possible to accurately estimate the intensity of scanning light on the photosensitive member.

  In the laser scanning unit (LSU) of the present invention, in the case of a single beam, the beam emitted from the LD element is generally designed to be a straight line as a layout reaching the polygon mirror 100. However, in the case of a multi-beam configuration (= meaning of a plurality of lasers), if one of the laser units has such a linear layout, the beam from the other LD elements to the polygon mirror 100 is affected. As shown in FIG. 1, the layout must be designed so that the optical path is bent by one or a plurality of (for example, two) mirrors 34 to reach the polygon mirror 100. Depending on the mirror used at this time, the beam may be affected, and the relationship between the laser driving condition I and the optical power L may be a distorted characteristic (so-called non-linear) different from a straight line. This distortion may also become severe in a specific range of the laser driving condition I even in the case of the same mirror. However, mirrors are used to bend the beam in a straight line and the mirror rarely moves once it is positioned.

  Therefore, the degree of distortion does not change each time it is used (ie, every time it passes through a once-positioned optical component), but the apertures 31, 31 ′ are changed to other apertures in order to change the beam size in the image plane. Or when the positions of the apertures 31 and 31 'are changed (that is, when the aperture position of the previous aperture is slightly shifted from the position of the beam when changing to another aperture), the laser driving condition I And the optical power L (I-L characteristics) may be affected. At this time, if there is a portion (range (range of light intensity, etc.)) where distortion originally exists with respect to the I-L characteristic, this portion is more strongly affected and the difference becomes larger according to the study of the present inventors. It has been confirmed. The apertures 31 and 31 'are changed in use in almost no LSU used in an image forming apparatus such as a laser printer, but may be in a photoconductor sensitivity evaluation apparatus using an LSU. Further, it has been confirmed by examination that the IL characteristic may be distorted when the neutral density filters 32 and 32 'are inserted in the optical path in order to reduce the light in the LSU. If the IL characteristic changes in this way, the optical power of the LD cannot be accurately controlled using past data of the IL characteristic stored in the memory. For this reason, even if the IL characteristic relational expression stored in the conventional memory is used so as to control the light quantity to the specified level, the scan with the planned light power L cannot be performed on the photoconductor, and therefore the photosensitivity. The characteristics cannot be measured accurately. In order to solve such a problem, in the laser scan unit LSU of the present invention, the replacement of the apertures 31, 31 ′, the neutral density filters 32, 32 ′, etc. or the change of the position is detected, and the I− Compares the change in L characteristics with the previous one, acquires a data string of data pairs (I, L) with laser power L when two or more I are newly changed, and the conventional IL relational expression And the acquired data pairs, and if the difference exceeds a certain acceptance criterion, the laser drive condition is determined using the newly derived IL characteristic relational expression based on the acquired data. Depending on the relationship between I and the laser power L, it is possible to control L (ideally Li) irradiated to the photoreceptor by inputting I into the LD related to the change.

  Here, the laser driving condition I will be described. As the laser driving condition I, there are a case where If which is a laser driving current value is used and a case where Im which is a laser monitoring current value is used. If is a current value for turning on the laser (laser emission), and its range has a lower limit of Ith which is a threshold value for starting laser emission. Further, Iop, which is a current value for emitting rated optical power, is the upper limit value. In the range from Ith to Iop, the optical power irradiated from the laser semiconductor as the light source is approximately in the range of 1 to 10 in terms of relative intensity. That is, if the light intensity at Ith, which is the threshold value for starting laser emission from the laser light source, is taken as the reference 1, the optical power up to about ten times the intensity at Iop. When light power lower than the light power emitted at the Ith emission lower limit is required, for example, by using an optical element (a neutral density filter) with a transmittance of about 10%, the drive current is 0.1 in total in the range from Ith to Iop. An optical power in the range of ~ 10 (relative intensity value) will be obtained.

  Furthermore, when another neutral density filter is increased and used, the optical power can be adjusted in a total range of 0.01 to 10. Similarly, if one more is used, the drive current can be adjusted in the range from Ith to Iop, and the optical power can be adjusted in the total range from 0.001 to 10. When the laser irradiation power is controlled in such a range, the range that can be evaluated as an evaluation device is widened, and in the present invention, the degree of freedom (usability) is remarkably improved (the neutral density filters 51 and 51 ′ in FIG. 1 are (Each filter is composed of three filters with the same transmittance, and each filter can move into and out of the optical path independently.)

  On the other hand, as I, use of the monitor current value Im of the laser can be mentioned. This uses the photocurrent Im when the laser light output from the rear surface of the laser chip is received by a photodiode incorporated in the LD element and monitored. This monitor current Im is different from the drive current value If. As shown in FIG. 1, when the laser is turned on, the monitor current value Im is input to the LD drivers 54 and 54 ', and is converted into a voltage value by IV conversion inside. This Im (converted to a voltage value) is compared with the input signal (reference signal: voltage value) from the DC voltage generator 55, 55 ', and the laser drive current If is adjusted so that the difference from the reference signal becomes zero. When the LD, which is the light source of the LSU, is turned on by the control method (Auto Power Control: APC), the Im value can be handled as the driving condition.

The light received by the PDs 571 and 571 ′ in the devices 57 and 57 ′ is light in the direction opposite to that emitted from the LD device. Correspondence between the photocurrent value Im of the light in the reverse direction and the optical power L of the image plane, or Im (Ref) as a reference signal and the correspondence between the optical power L of the image plane (data pair (Set) may be referred to as an IL characteristic. Although this Im can be said to be a substitute characteristic of the image plane optical power, in the present invention, the image plane is scanned with the optical power L that is affected by the optical component when the optical power emitted to the image plane side of the LD device is affected. The optical power Im emitted to the opposite side of the image plane side is not affected by the optical components, and it is necessary to measure the optical power L emitted to the image plane side.
When the light returning to the LD element by the optical component is emitted to the opposite side of the image plane side, it may overlap and this may be input to the LD driver as the photocurrent Im. When APC control is performed, the laser output stability may be disturbed due to this, and may further vary.

The PDs 571 and 571 ′ incorporated in the devices 57 and 57 ′ of the laser unit have an extremely small light receiving portion, a small monitor current Im itself, and a poor S / N ratio. However, according to the study by the present inventors, it has been found that there is no problem in controlling L by controlling each LD using this monitor current Im value. Therefore, a part of the emitted light on the image plane side is divided by a beam splitter and incident on an external PD (not shown), and the photocurrent is input to the LD driver as Im and controlled by APC. is there. In the case of this method, care should be taken because the beam splitter used may impair the linearity of the I-L characteristic in some cases (see FIGS. 3 to 8).
As the number of components having a thin film in the optical path increases, the possibility that the IL characteristic is affected increases. That is, in an optical component having these thin films, the linearity of the IL characteristic may be disturbed.

  In the present invention, the microcomputer 1 is mounted on the LSU, and changes in the optical parts 3 such as the apertures 31 and 31 ′ and the neutral density filters 32 and 32 ′ in the optical path, that is, changes in the optical parts 3 are detected, and laser driving conditions are detected. When I is applied, the laser power L is detected by light detection means (for example, PD 411) placed on the slider 41 at the front stage of the scanning system (more specifically, the front stage of the polygon mirror 100). And as the I-L characteristic, a data string of a data pair (I, L) of I and L is acquired, and the I-L characteristic relational expression deviates from linearity from the acquired I-L data string. It is configured to check the presence / absence of distortion (including changes in the distortion location) such as a location different from the original distortion as the presence / absence of the location or the IL characteristic. The optical power L to be confirmed at this time is measured after passing through optical components such as the apertures 31 and 31 ′ and the neutral density filters (which may include ND filters) 32 and 32 ′ and the image. The moving unit 4 is moved to the dotted line position as shown in FIG. 1 in order to install the PD 411 for measuring the amount of irradiation light in front of the polygon mirror near the surface (irradiation surface to the photoconductor). In the present invention, the optical power received by the PD (hereinafter simply referred to as PD (Photo Diode)) arranged in front of the polygon mirror and the power on the image plane (photoreceptor surface) are examined in advance. Ratio: [Image plane power / PD received light power (photocurrent)] (a ratio that takes into account the attenuation of optical power by the scanning system up to the photoconductor including the polygon mirror) and multiplying the optical power received by the PD Thus, it can be obtained as data of the optical power of the image plane. In order to detect this power data more accurately, it is preferable to make the area of the light receiving surface of the PD 411 larger than the beam and receive all of the light for scanning.

In order to detect whether or not an optical component replacement operation has been performed, for example, an aperture is provided with an identification unit for identification as shown in FIG. 2 at the bottom of a plate-like aperture. In order to detect the presence or absence of this change (exchange to another aperture, position change of the aperture), a photoelectric sensor (a combination of a light emitting unit such as an LED and a light receiving unit) is used, for example, 311- in FIG. As shown in 1-31-4, the position of the frame of the neutral density filter is made different for each part number, and the light receiving part receives this identification part from the light emitting part of the sensor. Thus, it is possible to detect the presence / absence of change and the type (product number) of the change.
More specifically, as a means for detecting when the optical component 3 such as the aperture 31, 31 ′ or the neutral density filter 32, 32 ′ is changed or moved, as shown in FIG. Four cutout portions serving as part numbers are provided at the end portions of these optical components, and the presence or absence of the cutout portions is received by a light detection element (for example, PTr: Photo-Transistor). For example, each notch is set to 1 bit and is associated as an n-bit signal. All of the PD is received by removing the aperture. This is the initial unit (for example, 0000 or 1111). On the other hand, it is assumed that, for example, the previous aperture is attached by using one of the apertures after the removal. In this case, the aperture i of the LD unit 1 is the aperture i. This is a case where it is once removed and set again, and it is not replacement of parts, but there is a change. Then, the MPU 11 in the LSU receives a signal indicating that the aperture i has changed by the detecting means. In order to measure the optical power of the LD unit 1 on the basis of this reception, the MPU 11 transmits it so as to move to the rotary solenoid 42, and on the side of the rotary solenoid 42 that receives this, the slider 41 is operated to operate the LD unit 1. The slider 41 on which the PD 411 is placed is moved on the optical path of the laser according to this change so as to measure the light beam intensity. The slider 41 moved to the specified position can start the measurement of the intensity of the laser beam in accordance with the instruction after the PD 411 placed on the slider 41 is set at a predetermined position. In order to detect the change of the optical component 3 described above, as shown in FIG. 2 (D), it has a plurality of light emitting elements (here, four) L1, L2, L3, and L4, and a plurality of light receiving elements (here) In this case, it is possible to detect information regarding which aperture is used for the change. As described above, the detection means used in the present invention may be an optical sensor using the light emitting unit and the light receiving unit as described above, but may be other than this. As shown in FIG. 2, the notch 311 provided for detecting the change of the product number is provided at an arbitrary position on the peripheral side of each optical component. In short, it is only necessary that the replacement of the part can be detected.

  As a result, as shown in FIG. 1, when the microprocessor 11 determines that the optical component 3 is changed, the detection signal associated with the change in the optical component 3 from the LD related to the detection signal to the scanning system (polygon mirror) is used as a trigger. Thus, the PD is moved to the previous stage of the polygon mirror 100 in the optical path where this detection signal is detected. For this movement, for example, the slider 41 on which the PD 411 is placed is performed using the rotary solenoid 42. The peripheral device of the microprocessor 11 includes an AD converter and a DA converter. This AD converter captures photocurrent (converted and input as a voltage signal), and the DA converter is used to add a drive condition signal to the LD driver. On / off of the LD driver can be performed as a peripheral device of the microprocessor 11 by a digital IO port (DIO). The drive condition signal to the LD driver uses a digital IO port instead of a DA converter, and the drive condition data is input to the DC voltage generator as digital data and the output signal (analog voltage) is input to the LD driver. It is preferable in terms of accuracy. This is preferable because the LD light power can be accurately controlled, and repeatability is extremely good.

  In addition, after detecting the identification signal of the optical component, it is desirable to acquire the I and L data pairs over the entire range of the LD driving conditions for the IL characteristics, but this acquisition takes a lot of time. . For this reason, check in advance where the distortion appears in the I-L characteristics of the optical part to be replaced or the optical part whose positioning may change when re-setting. If it is known that appears, data can be collected only for that range.

  Hereinafter, the present invention will be described more specifically by way of examples. However, the present invention is not construed as being limited to the following examples.

(Equipment used)
Multi-beam configuration LSU layout (LDs have different wavelengths),
System Configuration (in-house production) (see Figure 1)
-LD1 emission wavelength 780nm: manufactured by Sharp Corporation, product name GH07825C2K
・ LD2 emission wavelength 655nm: OpNext, product name HL6501MG
・ LD driver: Asahi Data Systems Co., Ltd., product name ALP-7033CA x 2 ・ LD control head with built-in temperature control function: Asahi Data Systems Co., Ltd., product name ALTH-103C x 2 ・ Aperture: 50 × 60, 70 × 85 (Aperture numerical value A × B is represented by an elliptical short axis (A) × long axis (B), which means the target beam size on the image plane: the unit is μm × μm), mainly. 50x60 was used.
・ DC voltage / current generator: ADC Corporation, product name 6144 2 units
If signal generation for LD drive conditions, Im (Ref) signal generation Photometer: Yokogawa Electric Co., Ltd., product name 3292 For measuring optical power of image plane PD: Hamamatsu Photonics Co., Ltd. product name S1336-8BK

In the layout in the LSU (Fig. 1), "ND filters" 51 and 51 'provided in the optical path for each LD element are each composed of three filters with a transmittance of about 12% each. It is configured. As a result, the range of optical power for scanning was switched between 0 and 3 as described above for the number of filters when the beam was transmitted. In combination with this and the laser drive condition range (minimum to maximum), the optical power (relative intensity) from the LD light source can be controlled to a range of about 0.001 to 10. On the other hand, the neutral density filters 32 and 32 'are used to move the entire range of optical power to be obtained (moving the entire range of optical power means that, for example, if the transmittance is 50%, the obtained optical power is The range is 0.0005-5, and if it is 10%, it means the range is 0.0001-1.) In the examples, a filter having a transmittance of 40% at 655 nm was used.
The laser driving condition was Im (Ref), and the power was measured by lighting in APC (Auto power control) mode.

[Initial state 1]
In the LSU used, as shown in FIG. 1, the laser beam of LD1 (780 nm) has a linear layout that passes through optical components such as a filter, and the beam of LD2 (655 nm) is 2 using a reflection mirror 34 and a beam splitter 33. The layout is such that the light path is bent and enters the polygon mirror 100. In either case, an aperture having an image plane beam size of 50 × 60 (an elliptical beam having a minor axis of 50 μm × a major axis of 60 μm) was used.
In the measurement of optical power, all ND filters are removed from the optical path. It is known that the ND filter used here (a three-element filter) can attenuate the intensity of light emitted from the light source LD without distorting it, but it has strong light power and little noise. This is to make a measurement.

The IL characteristics in the initial state are shown in FIGS.
FIG. 3A shows the IL characteristic of the laser unit LD1 under the layout shown in FIG. As shown in this figure, since the linearity (linearity) is extremely good, it can be seen that there is no problem in using the first-order approximation as the relational expression.
FIG. 3B shows the IL characteristic of the laser unit LD2 under the layout shown in FIG. Also in this figure, it can be seen that the linearity of the laser unit LD2 is good, and there is no problem in using the first-order approximate expression as the relational expression, as described above.
According to the IL characteristic relational expressions in FIGS. 3A to 3B, the IL characteristic relation may be expressed using a first-order approximation expression (linear function) in the initial state of each LD element. I understand that.

(Example 1: Use of 40% neutral density filter in LD2 unit)
A 40% attenuation filter 32 ′ is inserted into the laser unit LD2 of the multi-LSU unit (multi-LSU unit in the initial state) shown in FIG. 1 in the initial state.
The insertion of the 40% neutral density filter 32 ′ was detected by a PTr (phototransistor) installed in the vicinity of the neutral density filter. Upon receiving this detection signal, the MPU commands the rotary solenoid 42 to move the slider 41 for measuring the optical power by the photodiode PD 411 placed on the slider 41, and thereby the PD 411 placed on the slider 41. There was movement on the laser beam of LD2. The optical power measurement of the LD2 unit is ready, and the optical power of the LD2 can be measured. FIG. 4 shows the measurement results of the optical power L and Im immediately after entering the polygon mirror 100 after passing through the 40% attenuation filter 32 ′ in LD2. However, the image plane power is converted by multiplying the ratio described above. As shown in FIG. 4, the IL characteristic was distorted. Here, since the light is transmitted through a filter having a transmittance of 40%, the IL characteristic is simply obtained by adding the light attenuation of 0.4 to the relational expression shown in the IL relational expression shown in FIG. Multiplication is expected to yield the IL relationship. However, in the actual IL relational expression, the relationship between the image plane power L and Im deviates from the linearity of the linear approximation expression as shown in the IL relational expression of FIG. Even if the LD 2 is controlled by Im based on the IL relational expression (primary relational expression) in FIG. 3B, it is obtained by the IL relational expression (primary expression) shown in FIG. 3B. It can be seen that scanning of the image plane at L is not performed.

(Example 2)
The solid line in FIG. 5 is the IL relational expression shown in FIG.
5, after obtaining the IL relational expression obtained in Example 1, the 40% neutral density filter 32 ′ was removed and attached again. As a result, the change of the neutral density filter 32 ′ is detected by the detection means, and the trigger is applied so that the optical power is measured in front of the polygon mirror 100 as in the first embodiment, and the PD 411 on the slider 41 is changed to this change. It was set in the laser unit LD2. In this LD2 unit, the optical power L is measured and obtained in the same manner as described above. The neutral density filter slightly changes the angle with respect to the beam. When the data of the solid line and the dotted line in FIG. 5 are compared, the distortion is not improved. I-L characteristic It can be seen that has changed. Thus, it can be seen from Examples 1 and 2 that the IL characteristic relational expression may be changed by adding or resetting optical components such as the 40% attenuation filter 32 ′ ( 4 to 5).

(Example 3)
As in Example 1, a 50% neutral density filter 32 ′ was inserted in the optical path of the laser unit LD2. As a result, a change in the neutral density filter 32 ′ (insertion of the 50% neutral density filter) was detected, and a trigger for moving the rotary solenoid 42 was applied as in the first embodiment. As a result, the slider 41 is moved, and the PD 411 placed on the slider 41 is set on the optical path of the LD2 unit so that the optical power can be measured. Thereafter, the measurement of L when I was changed was performed in the same manner as in the previous example, and two or more data strings of the data pair (I, L) of I and L were acquired. The acquired (I, L) data was obtained by using Excel (trademark) manufactured by Microsoft Corporation to obtain a scatter diagram, a regression curve, and the square of the correlation coefficient R.
The result is shown in FIG.
The linearity is slightly distorted as compared with the case without the filter of FIG. However, it can be said that there is no problem in controlling the laser unit according to the laser driving conditions using the characteristic relational expression of the first-order approximate expression according to the IL characteristic relational expression shown in FIG. In other words, the IL characteristic relational expression is expressed by L = 3.4106Im-0.0609 (an expression in which L is approximated by a linear expression of I L = a ₁ I + a ₀ (where a ₁ is the slope of the straight line) And a ₀ represents an intercept.), A characteristic relational expression is represented), and its correlation coefficient R ² was 0.997. The slight deviation from the linear expression of L at the middle position of Im range seems to be caused by the type of filter (surface accuracy of glass surface, thin film thickness, etc.).

(Example 4)
Immediately after the aperture of LD2, a beam splitter was installed as an optical component so that the beam incident angle was 45 degrees. The transmittance of this beam splitter with respect to the laser beam wavelength of 655 nm was about 30%. As in the first embodiment, the slider 41 is moved by using a signal detected that the beam splitter is inserted as a trigger, and the optical power of the LD2 unit in front of the polygon mirror 100 is moved by the PD 411 placed on the slider 41. L can be measured. As a result, the optical power L was measured by changing I of the LD2 unit, and the data string of the data pair (I, L) was acquired. As a result of this measurement, it was confirmed that distortion appeared in the IL characteristic. The measurement of the IL characteristic was repeated three times (see “first to third times” in FIG. 7). As shown in FIG. 7, the IL characteristics of the first to third repetitions are collected as a data string, the first measurement results are plotted with ◆, the second measurement results are plotted with ■, and the third time The measurement results were plotted with ▲. When these first to third data acquisitions are compared, the same characteristics are shown, and it can be seen that there is no problem in reproducibility. Further, after the first to third measurements, the aperture was once removed and set again. As a result, as in the first embodiment, the slider 41 moves using the signal detected by the detection means as a trigger, and the optical power L can be measured in front of the polygon mirror 100. The IL characteristic of the LD2 unit was measured in the same manner as in the above example, and the data string of the data pair (I, L) was acquired. The results are plotted with x in FIG. It was recognized that this x was different from the IL characteristics of the first to third repetitions.

  The aperture (diameter) through which the beam passes is slightly deviated from the optical axis of the beam, resulting in a difference in image plane power. It is necessary to newly acquire (I, L) data and create an IL characteristic relationship diagram. It turns out that there is.

Further, as shown in FIG. 7, it was also found that in the case of this optical component, distortion tends to be strong around the center of the LD driving condition (Im is in the range of 0.65 to 0.9).
The reason for using such a beam splitter is to show that the IL characteristic may change when the aperture is replaced. If there is distortion, the effect of aperture replacement is emphasized.

[Example 5: Example of obtaining IL characteristic relational expression in LSU]
As shown in Example 1, when a 40% neutral density filter was used, the IL characteristics changed as shown in FIG. After changing the neutral density filter in this way, the IL characteristic is measured, and if the IL characteristic relational expression before the change stored in the memory is not compared with the measured IL characteristic relational expression, the memory It is impossible to determine whether or not L can be controlled by controlling I using the IL characteristic relational expression stored in (IL characteristic relational expression before change).
The operation of how to obtain the IL characteristic relational expression in the LSU will be described below with reference to the flowchart of FIG.
The state without the neutral density filter is defined as the specified state (initial state). In the LSU equipped with a plurality of LDs according to the present invention, in the microcomputer 1 in the LSU, for example, when a neutral density filter 32 'is added as an optical component, this is reduced by a detection means (photoelectric sensor). It is detected that there is a filter (S1 / Yes). When this detection signal is input to the MPU 11, the MPU 11 asks the user whether or not to check [do / do not] check the IL characteristic value (S2 (displayed on the display device 14)). When the user inputs “Yes” by input means (touch panel, key, etc.) (in the case of S2 / Yes), the transmittance of the optical component such as the filter 32 ′ (value corresponding to the wavelength of the LD) Find the input (S2 / Yes → S3). Even when the input is not performed, the transmittance of the optical component inserted from the previous history is displayed, and when the confirmation is input, the measurement can be performed as follows. Even if no input is made, the data pair is stored in the memory, and when the transmittance is known, the transmittance can be input and the process can proceed to step S9 (S15 / No → S9). .

After completing the input from the user, the LSU microcomputer (MPU11) issues a command to the vice rotary solenoid (RSR 14 / 10-CAB0 manufactured by Takano Co., Ltd.) 42 to move the slider 41 on which the PD411 is placed. The PD 411 attached to the slider is inserted so as to block the optical path in order to measure the optical power, and set so that the total light quantity of the beam of the LD unit according to the change of the filter 32 ′ in this embodiment can be measured. In this state, Im (Ref) data is sent to a DC voltage generator (product name DC voltage generator 6144) 55 'manufactured by ADC Corporation. In this embodiment, a DIO line (Digital Input / Output) is used and data is transmitted in a digital form (data format is BCD: Binary Coded Decimal) (see FIG. 1, where Im (Ref) is Im described above) (Reference signal)).
The DC voltage generator 55 ′ converts the BCD data into a corresponding analog voltage, which is input to the LD driver 54 ′. In the microcomputer 1 in the LSU, an On / Off signal is sent to the pulse modulation input line of the LD driver using, for example, a DIO line. When the laser is turned on, the photocurrent of PD571 ′ is input to the LD driver and emits light stably in the APC mode. Sequentially, Im (Ref) data is sent to the DC voltage generator 55 ′, and the PD 411 placed on the slider 41 measures the optical power of the laser beam irradiated to the polygon mirror 100 at that time. The photocurrent (unit: mA) that is the measurement data is read by an AD converter through an amplifier 43 (which simultaneously converts the current into a voltage) placed on the slider 41.

  The read data is converted to the image plane power (mW) by multiplying by a coefficient (2.753 mW / mA in this embodiment) that is converted into the value of the image plane optical power, and further the attenuation filter using the transmittance data. It is converted into image surface light power L when there is no image. The converted data is correlated with the corresponding I-L data pair, and the difference is examined point by point with the “IL characteristic without the neutral density filter” stored in the memory 12 in the microcomputer 1 (: S7 At this time, it is also possible to first store IL data pairs in advance: S6). If the difference is within a predetermined criterion (here, 5% as an allowable reference value, and within this allowable reference value), leave it as it is (S1 / Yes → S16), and if the standard (allowable reference value) is exceeded Displays a warning to that effect on the display device.

In addition, the user can stop using the neutral density filter and change it to another one (including reattachment: S9 / No → S1), or in order to create the relational expression of the IL characteristic as it is, the IL It can also be determined whether or not to continue collecting data pairs (S9 / Yes → S10). When it is determined to continue (in the case of S9 / Yes), determination is performed using the primary relational expression as the IL relational expression (S10). The least square method was used to calculate the linear relational expression. In this embodiment, when R ² (contribution rate) that is the square of the correlation coefficient R is 0.999 or less, approximation is performed using a fifth-order polynomial. In this embodiment, it is 0.9982, so an approximate expression using a fifth order polynomial was used. Software for obtaining these IL characteristic relational expressions is incorporated. The validity of the calculation is confirmed with commercial spreadsheet software (Microsoft, Excel).

  In this embodiment, the situation of the “difference” of the optical power for each driving condition is also examined, and when the difference (%) is not uniform and varies in the range of the laser driving condition (minimum to maximum), the distortion is It is judged that it has occurred (determined that the approximation of the linear expression is difficult: S11 / No). If there is data with a difference exceeding ± 5%, it is determined that there is a problem (S11 / No).

In the present invention, when a strong distortion appears in the I-L characteristic, the range of the laser driving condition can be divided into two or more, and the approximate expression can be applied to each divided region. However, in this embodiment, the entire range is dealt with by approximation with one quintic polynomial. Further, only the range in which strong distortion appears can be extracted, and an IL characteristic relational expression can be obtained for only this extracted portion using an approximate expression based on a fifth-order polynomial.
Table 1 shows the relationship between IL before and after the change obtained as described above.

  The column of “(Default) A” and the column of “Image plane position B” in Table 1 are “Default data” and “After filter setting, but without filter at the image plane position (= meaning 100% transmittance). Optical power (converted value from PD measurement) data ”, these are L, the relationship with Im in Table 1 is shown in FIG. 10 and the plot before change is ◆ (initial value (default value)) The change is shown by the ■ plot. It can be seen that through the entire range of driving conditions, the IL characteristic relational expression after the filter is set is different from that before the setting, and approximation by linear expression approximation is impossible.

The flow up to this point shows determination as to whether or not there is a problem of deviation from the previous IL characteristic relational expression. It is determined that there is a problem (in the case of S11 / No), and the IL characteristic relation is determined. A step of approximating the equation with a polynomial is executed (S12). As a result, an IL characteristic relational expression is newly created by approximation with a fifth-order polynomial.
The IL relational expression is based on experience so far that the fifth-order polynomial approximation is appropriate.
An approximation by a fifth order polynomial was calculated with built-in software. This is shown in FIG.
The formula in FIG. 10 is as follows.
y = −25.519x ⁵ + 77.478x ⁴ −85.154 x ³ + 41.3x ² −2.2719x + 0.614
... (A)
(In this equation, x is Im (Ref) and y is the optical power L.)

However, the reason why the relational expression of the IL characteristic is used in the evaluation system is that there is an exposure energy (arbitrary) to be given to the sample (specimen) in the system, and in order to determine the LD driving condition for giving this exposure energy It is.
At this time, in order to calculate the stationary beam power (optical power on the image plane) L given to the photosensitive member from parameters such as the photosensitive member linear velocity and the LSU optical system, and to irradiate the photosensitive member with such a stationary beam power L The LD drive condition I is determined. Therefore, in the relational expression, it is convenient that x is the image plane Power and y is the driving condition I. Explaining in Table 1, x is “power converted to image plane position data” in the fourth column, and y is the driving condition Im in the first column.

It is as follows in this embodiment. The result is shown in FIG.
y = 0.0526x ⁵ −0.4025x ⁴ + 1.1185x ³ −1.3757x ² + 1.1238x−0.1321
... (B)
(In the above formula (B), x represents optical power and y represents Im (Ref).)

  FIG. 11 shows a curve when approximated by a fifth-order polynomial. Even if the I-L characteristic is distorted, a new (I, L) data string is acquired on the spot and the I-L is acquired. The characteristic relational expression is recreated, and accurate exposure can be performed using the newly created IL characteristic relational expression (S13). In the present invention, the sensitivity characteristic evaluation of the photosensitive member (photosensitive member for the image forming apparatus) can be performed by the photosensitive member sensitivity characteristic evaluation apparatus having the LSU on which a plurality of LDs are mounted. As shown in FIG. 1, the sensitivity characteristic evaluation apparatus for a photoreceptor of the present invention has the above-mentioned LSU, and a movable means that can rotate the photoreceptor on a predetermined condition so that the sensitivity of the photoreceptor can be evaluated. And are covered with shielding means such that they are disposed in a space for shielding light. Such a rotationally movable means is controlled by another control means, but an LSU MPU and a control means positioned above the rotationally movable means control means may be provided for integrated control.

It is a block diagram which shows the structure of LSU mounted with several LD of this invention. It is a figure which shows an example of the detection means for detecting the change of an optical component, and is the figure shown taking the aperture as an example as an example of an optical component. It is a graph which shows IL relational expression of each laser of LSU of this invention, (A) is a graph which shows IL relational expression (initial value) of LD1, (B) is IL relation of LD2. It is a graph which shows a formula (initial value). (A) is the graph which showed the relationship between Im and image surface power (L) when a 40% attenuation filter is inserted in the optical path concerning LD2, along with the IL relational expression (initial value: straight line). It is a graph showing the relationship between Im after insertion of a 40% attenuation filter and the image plane power (L) in the optical path related to LD2, the solid line represents the relationship of Im-L after insertion, and the dotted line represents the filter. It shows the Im-L relationship after inserting and removing and slightly changing the angle with respect to the beam. It is the graph showing the relationship between Im after inserting a 50% attenuation filter in the optical path concerning LD2, and image surface power (L). Immediately after the aperture of LD2 (655nm), set the beam splitter, repeatedly acquire the (I, L) data string to check the reproducibility of the data, remove the aperture once, and reset (I , L) is a diagram showing the I-L characteristics of the acquired data strings. It is a flowchart which shows the operation | movement for calculating | requiring an IL characteristic relational expression using LSU of this invention. It is the graph which compared by the presence or absence of the 40% attenuation filter of LD2 (655nm) (the data of “with filter” is converted into the power when there is no data (meaning transmittance of 100%)). When the IL relational expression shown by the straight line is 40% without neutral density filter (indicated as ◆ default data in the figure), ■ indicates the (I, L) data string with 40% neutral density filter This is a plot of the object (shown as ■ when the filter is set in the figure). It is a graph which shows the validity of the application which approximated IL relational expression by the quintic approximation from the plot of (3) shown in FIG. The straight line is the same as the straight line shown in FIG. FIG. 10 is a graph obtained by obtaining an IL characteristic relational expression (fifth-order approximate expression) using the laser driving conditions as a function of the image plane light power with the data at the time of “filter setting” shown in FIG. 9.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Microcomputer 3 Optical component 4 Moving means 11 MPU (Micro-Processing Unit)
12 Memory 13 Interface (I / F)
14 Display 15 Input 31, 31 ′ Aperture 32, 32 ′ Neutralizing filter 33 Beam splitter 34 Reflecting mirror
41 slider
42 rotary solenoid
43 amplifiers 51 and 51 ′ ND filters (each composed of a plurality of neutral density filters)
52, 52 'Filter driver 53, 53' Temperature control unit 54, 54 'LD driver 55, 55' DC voltage generation unit 56 Motor driver (for polygon)
57, 57 ' laser unit (laser light source)
100 Deflection means (polygon mirror)
101 scanning optical system 102 photoconductor (device under test)
411 light detection means (photodiode)

Claims (9)

A laser scanning unit (LSU) equipped with a plurality of laser light sources ,
The laser scanning unit, a microprocessor, memory, interface, display device, and a microcomputer system comprising a key input device, is controlled so as to light the respective laser light sources to the light intensity L by the laser driving condition I,
Have the laser light sources and various optical components, and,
A detection unit for detecting a change of the optical component,
Based on the instruction from the microcomputer system, one in a position a and position after the optical component passing before the laser beam is incident on the polygon mirror, of said plurality of laser sources after the optical component passing One of so as to totally by receiving a laser beam, is configured to have a moving means for causing movement of the light detection means to the laser beam on the optical path, and
When the detection unit detects a change in the optical component,
Changing two or more of the laser driving conditions I of the laser light source affected by the change of the optical component, and detecting the intensity L of each obtained light by the light detecting means moved by the moving means ;
The microcomputer system acquires a data pair (I, L) of the two or more changed I and the intensity L of each light obtained by each I as a data string, and the two or more acquired data strings And the IL characteristic data stored in the memory in the microcomputer system ,
When the difference exceeds a certain allowable standard, the light intensity L of the laser light source is calculated based on the laser driving condition I using the newly derived IL characteristic relational expression based on the acquired data. A laser scanning unit characterized by controlling . It said light detecting means is a photodiode, the optical component is either intended to attenuate the intensity of the light, or not to determine the image plane beam size, it is intended for a part or all of the laser beam counterclockwise Isa The laser scan unit according to claim 1.   The laser scanning unit according to claim 1, wherein the optical component is at least one selected from a neutral density filter, a splitter, and an aperture. The light detecting means is a photodiode;
The laser scanning unit is controlled to light each laser light source at the light intensity L according to the laser driving condition I using the following relational expression (1):
The microcomputer system instructs the mobile unit to move in the optical path of the laser beam on the basis of the detection signal of the optical component changes more affected changes before Symbol optics of the photodiode, a laser Two or more driving conditions I are changed, and the light intensity L of the laser beam of the laser light source is detected by the photodiode, and the changed I and L obtained by this I are a data pair (I, L) 4. The laser according to claim 1, wherein the I-L characteristic data obtained from the acquired data string is newly approximated by the relational expression (1). 5. Scan unit.
I = a _n L ⁿ + a _n-1 L ^n-1 + (1)
(L is the optical power at the image plane position (unit is mW), I is the laser driving condition (when the laser driving condition I is current, the unit is mA, and the current value is converted into a voltage value) V), and an, an-1,... Are coefficients of each term, where n is an integer of 1 or more.)   The two or more laser drive conditions I to be changed are in a range from a threshold Ith (lower limit) of the laser drive current to Iop (upper limit) for outputting the rated power, and a plurality of I in the range are changed to I The laser scan unit according to claim 1, wherein a data string of a data pair (I, L) of L and L is acquired. 6. The laser scan according to claim 1 , wherein, when the data pair includes a data pair that deviates from a predetermined allowable standard based on the comparison , a warning is displayed on the display device. unit. According to the comparison, when there is a data pair that deviates from an acceptance criterion defined in advance in the data pair,
The laser scanning unit uses the approximated expression of the IL characteristic relational expression based on a fifth order polynomial as the following relational expression (2) for the acquired data string, and the laser light source affected by the change of the optical component the laser scanning unit according to any of claims 1 to 3, characterized in that to control the intensity of the light L.
I = a _n L ⁿ + a _n-1 L ^n-1 + (2)
(L is the optical power at the image plane position (unit is mW), I is the laser driving condition (when the laser driving condition I is current, the unit is mA, and the current value is converted into a voltage value) V), and an, an-1,... Are coefficients of each term, where n is an integer of 1 or more.)   A photoconductor sensitivity characteristic evaluation apparatus comprising the laser scan unit according to claim 1. The detection unit detects changes in the optical components in the laser scan unit (LSU)
Based on a command from the microcomputer system, a position before the laser beam is incident on the polygon mirror, and a position after passing through the optical component, of the plurality of laser light sources after passing through the optical component. Move the light detection means on the optical path of the laser to receive all the laser beam,
The intensity L of the irradiation light is measured, the laser driving condition I and the intensity L are changed by changing two or more I, and a data pair (I, L) of the changed I and L obtained by this I ) Data columns,
The two or more acquired data strings and the data pair (I, L) obtained from the IL characteristic relation stored in the memory in the microcomputer system are represented as L of each data pair having the same value of I. Compare with the value of
It is determined whether the difference from the data of the IL characteristic relational expression stored in the memory by the comparison exceeds a predetermined permissible standard, and if the difference exceeds the predetermined permissible standard, The power of the laser light source affected by the optical component changed by the IL characteristic relational expression obtained by two or more data strings is controlled, and if the difference does not exceed the predetermined allowable standard, the memory is stored in the memory. A program for controlling a laser scan unit, which controls the laser scan unit to control the power of a laser light source affected by an optical component changed by a stored IL characteristic relational expression.

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