JP2000180764A - Optical scanner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately comprehend the present state of a semiconductor laser, even when using a scanner under ambient temperature which is different from the reference temperature. SOLUTION: A turn-on time counting circuit 80 counts the line turn-on time of one line by counting the turn-on/off data of one line fetched from an image- processing IC 62 for every pixel, integrating it with density data fetched from the IC 62 and performing proportional correction to the density data. A turn-on time counting circuit 82 counts line turn-on time. A turn-on time correction circuit/comparator circuit 84 fetches cumulative line turn-on time data stored in the circuit 82 by one page, and integrates it with a temperature correction coefficient selected based on the ambient temperature detected by a temperature detector 66, so as to correct the temperature. The corrected turn-on time is added successively to obtain the cumulative correction turn-on time and is compared with guaranteed time under the reference temperature stored in a guarantee time storage memory.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical scanning device, and more particularly, to an optical scanning device for turning on a semiconductor laser according to image data.

[0002]

2. Description of the Related Art At present, an electrostatic image forming apparatus for copying an image on transfer paper by electrophotography has been widely used. In this electrostatic image forming apparatus, an electrostatic latent image is formed by scanning a photosensitive member having a uniformly charged surface with a light beam modulated based on image data by a scanning device. After supplying toner to the developed electrostatic latent image and developing it,
The transfer paper is superimposed on the developed toner image, and the toner is electrostatically attracted to the transfer paper surface and transferred. Thereafter, heat or pressure is applied to the transfer paper to fix the transferred toner image, thereby forming an image.

Here, a semiconductor laser is used as a light source of an optical scanning device that scans a photosensitive member with a light beam. The life of the semiconductor laser (the time during which it can be turned on until a failure occurs) is longer than the life of the image forming apparatus. In order to determine whether the semiconductor laser can be reused, it is important to grasp the current state of the semiconductor laser.

In general, a semiconductor laser emits light for a long time,
It is known that the drive current required to output a predetermined light amount gradually increases, and the differential efficiency decreases. It is known that, when a semiconductor laser emits light at a predetermined drive current, the output light quantity gradually decreases as the semiconductor laser deteriorates.

FIG. 12 shows a state transition characteristic of a semiconductor laser which focuses on a change in a drive current required to obtain a constant output light amount depending on a lighting time of the semiconductor laser. Generally, failure of semiconductor laser (change of state until failure)
Can be classified into three types (type 1 to type 3) as shown in FIG. In FIG. 12, the vertical axis represents the driving current If necessary to obtain a constant output light amount, and the horizontal axis represents the semiconductor laser lighting time h, and the driving current Ifb is 1.5 times the initial driving current Ifa. Is used as a failure criterion.

[0006] The type 1 failure is a type in which the current rapidly increases during a short lighting period and exceeds a drive current value as a failure determination reference, and is an initial failure caused by a manufacturing process. The main causes of this type 1 failure are defects in the formation of the semiconductor laser such as defects in the formation of the light absorbing portion such as scratches on the cavity mirror of the semiconductor laser, dark portions (dark spots and the like) in the active layer of the semiconductor laser, and short-circuiting of the electrodes. It is.

[0007] Type 2 is a type that suddenly occurs during use of a machine and suddenly increases in current to exceed a drive current value of a failure determination criterion. The application of the electric current causes the cavity mirror to be destroyed, or the proliferation of the light absorbing portion due to a minute defect or the like existing when the cavity mirror of the semiconductor laser is manufactured.

Further, type 3 belongs to a wear-out failure, and a lattice defect is transferred to the inside of the active layer of the semiconductor laser by, for example, transferring a lattice defect from the substrate surface to the inside of the active layer of the semiconductor laser during the manufacture of the semiconductor laser chip. This is caused by the formation of a dark portion due to the mismatch, and in each case, the current injection-luminous efficiency gradually deteriorates.

[0009] Of these three types of semiconductor laser failures, type 1 semiconductor laser failures can be eliminated by screening such as burn-in. Therefore, when a semiconductor laser is used as a light source of an optical scanning device, failures that need to be noted include those having an intermediate life between Type 1 and Type 2 which cannot be screened due to burn-in, and those of Types 2 and 3. It is a failure.

[0010] The lifetime (lighting time) of the semiconductor laser as described above is determined by a manufacturer by conducting an energizing time test in which a current is passed so that a constant light quantity is obtained under the worst environmental temperature. Is guaranteed in a guaranteed manner. However, the time guaranteed by the manufacturer is the life of the semiconductor laser when used at a certain predetermined temperature (hereinafter referred to as “guaranteed temperature”), and the life of the semiconductor laser depends on temperature (depending on the environmental temperature). It is known that the time required to reach a failure criterion varies). Therefore, when the semiconductor laser is used under an environment temperature that changes depending on the environment at that time, even if the optical scanning device using the semiconductor laser is recovered due to a failure of the image forming apparatus, the accurate remaining life of the semiconductor laser is not known. However, it was not possible to determine the reusability.

In this life guarantee method, statistics are guaranteed for each beam, and when the number of beams increases, FIG.
As shown in FIG. 3, since the statistical failure rate for each beam is integrated, the life of the statistical guarantee in the optical scanning device is shortened. In order to guarantee the same level of service life as a single beam, an excessive guarantee rate is guaranteed for each beam, or a long laser life test is guaranteed, which limits the shortening of the laser development period. There was also a problem.

Therefore, in the conventional life determination of the semiconductor laser, attention is paid not to the lighting time but to the fact that the drive current increases due to the long-time emission of the semiconductor laser. A technique for determining that the life has expired when a failure criterion is reached has been proposed (JP-A-2-194).
975).

FIG. 14 shows a schematic configuration of a semiconductor laser deterioration detecting apparatus to which this technique is applied. As shown in FIG. 14, the semiconductor laser 500 is an LD driver 5
02, a drive current Id is supplied to output a light beam,
The amount of output light is monitored by the photodiode 504. The up / down counter 506 controls the drive current Id by increasing or decreasing the counter value so that the output light amount from the semiconductor laser 500 becomes constant. More specifically, the output voltage V0 of the D / A converter 508 changes as the counter value of the up / down counter 506 increases and decreases, and the LD driver 5
02, the output current I of V / I converter 510
The drive current Id is controlled by changing 0. That is, the output voltage V0 from the D / A converter 508 has a correlation with the drive current Id. Comparison circuit 51
2, the output voltage V0 from the D / A converter 508
Is compared with the reference voltage Vr to determine whether or not the drive current Id of the semiconductor laser 500 under a certain amount of light has exceeded the failure reference current value, thereby determining the life.

Also, a technique has been proposed in which the lifetime is determined by comparing the value with the initial value, paying attention to the decrease in the external quantum differential efficiency (see Japanese Patent Application Laid-Open No. 3-183181).

FIG. 15 shows a schematic configuration of a semiconductor laser deterioration detecting apparatus to which this technique is applied. As shown in FIG. 15, the driving current of the semiconductor laser 600 is controlled by the microcomputer 602. The output light amount of the semiconductor laser 600 is detected by the detection unit 604, and the detection result is input to the microcomputer 602. Microcomputer 602
Then, the differential efficiency is obtained from the change in the driving current that changes the output light amount of the semiconductor laser 600 from the predetermined value p1 to p2,
The life is determined by comparing with the initial differential efficiency stored in the comparing unit to determine whether or not the difference is within an allowable setting range.

In the case of a plurality of beams, a use limit is determined based on the size of a beam spot, and even if one beam does not operate, the life is switched by switching to another beam (Japanese Patent Laid-Open No. 5-6077). Gazette).

[0017]

However, the prior art does not take into account the temperature dependence of the life of the semiconductor laser (lighting time until failure), so that the optical scanning device is marketed due to the failure of the image forming apparatus. Was collected, only a binary determination of whether or not the failure criterion was reached could be made.
Further, even if the remaining life was determined, only the determination including a large error could be performed due to the temperature dependency. Therefore, in the prior art, it was not possible to make a highly accurate recycling determination of the semiconductor laser or the semiconductor laser unit mounted on the optical scanning device recovered from use.

Further, since the minimum lighting time per pixel of the optical scanning device is very short, on the order of ns (nanosecond), measuring the lighting time in real time requires a complicated and expensive measurement system. However, the method of correcting the laser life that changes depending on the environmental temperature was not clear. For this reason, there is no optical scanning device that counts the lighting time of the laser in consideration of the temperature dependence of the life of the semiconductor laser and compares it with a desired guaranteed time.

A method of providing a temperature detecting / cooling mechanism in an assembly body of a semiconductor laser and controlling the temperature dependence of the electro-optical characteristic value of the semiconductor laser is known as a known technique (Japanese Patent Application Laid-Open No. Sho 53-61290). However, in this technology, a semiconductor laser can be used for a long time,
Since there is no mechanism for determining the life of the semiconductor laser and the guaranteed temperatures are different, it was not possible to determine with high accuracy whether or not the laser can be reused.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an optical scanning device capable of accurately grasping the current state of a semiconductor laser even when used under an environmental temperature different from the guaranteed temperature. The purpose is to provide.

[0021]

According to an aspect of the present invention, there is provided an optical scanning device for lighting a semiconductor laser in accordance with image data, wherein the lighting time of the semiconductor laser is reduced. The semiconductor laser is characterized by having a counting means for counting, and a state determining means for determining a current state of the semiconductor laser based on a counting time by the counting means and a preset reference lighting time.

According to the first aspect of the present invention, the optical scanning device includes the counting means and the state determining means. The counting means counts the lighting time of the semiconductor laser. The state of the semiconductor laser gradually changes by lighting. Therefore, the counting time (total lighting time) of the semiconductor laser obtained by the counting means indicates the state of the semiconductor laser. The state determining means is based on the counting time (total lighting time) of the semiconductor laser obtained by the counting means and a preset reference lighting time (for example, a guaranteed time in which normal lighting is guaranteed by a manufacturer). The state of the semiconductor laser is determined.

Incidentally, the counting means is provided for the ns of the semiconductor laser.
Instead of directly measuring the (nanosecond) order lighting time, as described in claim 3, image data (for example, density data input to an optical scanning device or a semiconductor generated in an optical operating device) The lighting time of the semiconductor laser may be obtained and counted based on the data for turning on / off the laser).

According to a second aspect of the present invention, there is provided an optical scanning device for lighting a semiconductor laser in accordance with image data, wherein the counting means for counting the lighting time of the semiconductor laser, and the state determining means, comprise: Detecting means for detecting, a correcting means for correcting the counting time by the counting means based on the temperature detected by the detecting means, a corrected counting time corrected by the correcting means, and a preset reference lighting. State determination means for determining a current state of the semiconductor laser based on time.

According to the second aspect of the present invention, an optical scanning device includes a counting unit, a determining unit, a detecting unit, a correcting unit, and a state determining unit. The counting means counts the lighting time of the semiconductor laser. The correcting means corrects the counting time (total lighting time) obtained from the counting time based on the temperature detected by the temperature detecting means. That is, the counting time is temperature-corrected in response to a change in the life of the semiconductor laser (lighting time until failure) due to the temperature. The details of the temperature correction applied to the present invention will be described later.

The state determining means determines the state of the semiconductor laser based on the correction counting time and a preset reference lighting time (for example, a guaranteed time for which normal lighting is guaranteed by a manufacturer).

The counting means may calculate the lighting time of the semiconductor laser based on the image data, as in the first aspect.

Next, the principle of temperature correction of the lighting time of a semiconductor laser (hereinafter referred to as "LD") applied to the present invention will be described.

LD used as a light source of an optical scanning device
, The lighting possible time (hereinafter referred to as “guaranteed time”) is guaranteed by the manufacturer. The guaranteed time is a time when one lamp is lit and a predetermined guaranteed temperature (hereinafter, referred to as “reference temperature”).
, And the guaranteed time changes when the environmental temperature or the number of lightings changes.

The change in the guaranteed time of the semiconductor laser when the ambient temperature and the number of lightings are used as parameters will be described below. However, for environmental temperature changes of several tens of degrees Celsius,
The increase in the junction temperature change due to the increase in the number of lighting is several degrees Celsius and about 1
Since it is 1/0, the contribution of the increase in the laser junction temperature due to the increase in the number of lightings to the change in the laser assurance time is negligible compared to the change in the environmental temperature, and is not taken into consideration here.

First, a laser assurance time for an environmental temperature change at the time of one lighting is derived. The guaranteed time t (T) of the LD at an arbitrary environmental temperature T at the time of lighting of one lamp is represented by the activation energy Ea, the Boltzmann constant k, and the reference temperature T ₀ from the Arrhenius equation relating to the temperature change of the chemical reaction rate constant.
If the guaranteed time in is represented by t ₀ , it is generally expressed as in Equation 1.

[0032]

(Equation 1)

The activation energy Ea is derived from a temperature accelerated energization test of the semiconductor laser.

Next, the guaranteed time t (n) at the time of n lines is obtained by calculating a statistical laser failure rate function per lighting, that is, a survival rate per line and raising it to the nth power.
Specifically, since the failure rate function is expressed by a Weibull function, the survival rate is calculated from the Weibull failure rate function per one, and is calculated by raising to the nth power. Therefore, assuming that the guaranteed survival rate per one is β, the Weibull shape parameter is m, and the scale parameter is η, the guaranteed time t (n) at the time of n pieces is expressed as Expression 2.

[0035]

(Equation 2)

This equation 2 is an example in which the guaranteed time t ₀ of the above equation 1 is converted into an actual failure rate function, and the one obtained by substituting t (n) of the equation 2 for t ₀ of the equation 1 is an arbitrary environment. The laser guarantee time t (n, T) at the temperature T and the number n of lightings is given by the following equation (3).
It is generalized as follows.

[0037]

(Equation 3)

For reference, Table 1 shows the specific laser guaranteed time t (n, T) obtained from Equation 3, and FIG. 11 shows the laser guaranteed time t (n, T) using the values in Table 1. An example of the change is shown below.

[0039]

[Table 1]

In Table 1, E is a general value of a semiconductor laser specifically used in a laser printer.
a = 0.6 to 0.8 eV (depending on the semiconductor laser used), t ₀ = 1000 hours, T ₀ = 60 ° C., β = 99
%, Η = 10750 hours (depending on the failure type),
m = 2 (wear failure period, depends on failure type).

From the above relationship, it can be seen that the guaranteed time of the laser is uniquely changed by the environmental temperature change and the number of lightings. Therefore, simply counting the laser lighting time up to the present time does not provide an accurate understanding of the current situation with respect to the laser warranty time, and compares the function for counting the corrected lighting time corrected based on the environmental temperature with the warranty time. For the first time, it is possible to accurately grasp the state of the laser, that is, the remaining life, by providing the function of performing the above operation.

The correction of the lighting time based on the environmental temperature is specifically performed by calculating the ratio of the guaranteed time at an arbitrary temperature obtained by Expression 3 and the guaranteed time at a reference temperature as a reference.
The ratio is multiplied by the lighting time at an arbitrary temperature to obtain a corrected lighting time. For example, the lighting time at a single beam temperature of 20 ° C. is t1, the lighting time at a temperature of 30 ° C. is t2, and the reference temperature is 60 ° C.
Then, the corrected lighting time tc can be obtained as in Expression 4.

[0043]

(Equation 4)

The reference temperature is Th, and an arbitrary temperature section T
If the lighting time at m is tm, the corrected lighting time tc
Is generalized as shown in Equation 5.

[0045]

(Equation 5)

In order to accurately describe the temperature, the temperature must be treated as a continuous amount. However, since there is a temperature measurement error, tm is defined as a lighting time at a representative value in a certain temperature section.

Therefore, as can be seen from Equation 5, if the temperature information is obtained, the guaranteed time due to the environmental temperature change can be converted into the lighting time at the reference temperature (the lighting time is temperature corrected), and The remaining life can be estimated by comparing with the guaranteed time at the temperature. Also,
The correspondence to n beams can be solved by providing each beam with this function independently. Therefore, if this function is introduced into the optical scanning device, it is possible to determine the lifetime of the guaranteed time and determine whether recycling is possible.

Next, the specific configuration will be described.

As a method of correcting the lighting time temperature, a method of correcting the lighting time by hardware, a method of correcting the lighting time by software, and a temperature correction table are prepared in advance by incorporating the temperature detection data and Equation 5 into a control circuit. A method is conceivable. In any method, the first unit for detecting the temperature of the image forming apparatus, the optical scanning device, or the laser, the second unit for counting the lighting time of the laser, and correcting the lighting time of the laser based on the detected temperature. And a fourth means for storing the temperature-corrected lighting time, and a fifth means for comparing the stored temperature-corrected lighting time with the guaranteed time under the reference temperature. At least means are required.
Further, based on the result of the comparison, the sixth means for turning on / off the laser current circuit of the semiconductor laser driving circuit and, if necessary, the stored temperature-corrected lighting for checking when the laser current circuit is recovered from the market. The system functions as a system by displaying time and adding a seventh means for warning a laser failure in the case of failure (life expiration). The details of the optical scanning device having this system will be described using a specific example in an embodiment (first embodiment) of the invention described later.

In the case of a plurality of beams, the second to sixth means are independently provided for each beam, and the maximum value of the lighting times independently corrected for temperature is obtained, and the guaranteed time under the reference temperature is calculated. The feature is that an eighth means for comparing is further provided, and the result is passed to the seventh means. The details of the optical scanning device having such a system will be described with a specific example in an embodiment (second embodiment) of the invention described later.

[0051]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) Next, an example of an embodiment according to the present invention will be described in detail with reference to the drawings.

FIG. 1 shows an image forming apparatus 10 provided with an optical scanning device to which the present invention is applied. As shown in FIG. 1, the image forming apparatus 10 is covered with a casing 12.

A paper tray 14 is provided below the image forming apparatus 10. In the paper tray 14, for example,
Paper 16 of a desired size such as a B5 size, a B4 size, an A4 size, or an A3 size is provided. A half-moon roller 18 </ b> A is provided near the paper discharge section of the paper tray 14. The half moon roller 18A sends out the sheets 16 supplied to the sheet tray 14 one by one in order from the upper layer. The paper 16 sent from the paper tray 14 is transported by a plurality of transport roller pairs 20 between a photosensitive drum 22 and a transfer charger 24 described later.

On one side (right side in FIG. 1) of the image forming apparatus 10, a manual feed tray 26 into which the paper 16 is manually inserted as required is provided. Bypass tray 26
In the vicinity of the paper discharge section, the above-described paper tray 14 is provided.
A half-moon roller 18B is provided in the same manner as
Can be sent out one by one from the upper layer.

On the side (left side in FIG. 1) of the image forming apparatus 10 facing the side on which the manual tray 26 is provided, there is provided a discharge tray 28 for discharging the paper 16 on which a desired image is formed. Have been.

An image forming unit 30 is provided in the casing 12. The image forming section 30 includes a cylindrical photosensitive drum 22 that rotates at a constant speed in the direction of arrow A shown in FIG. 1, image data obtained by reading an original with a scanner and performing various image processing (the image forming apparatus according to the present embodiment). 10 is intended for a black-and-white image, and is converted into gray-scale image data by performing image processing (see FIG. 1). The image forming apparatus includes a scanning device 32 and a fixing device 34 for fixing a desired image on the paper 16.

A charger 3 is provided near the peripheral surface of the photosensitive drum 22.
6 are provided. The charger 36 is connected to the photosensitive drum 22
Is uniformly charged. The photosensitive drum 22 uniformly charged by the charger 36 is irradiated with a light beam by rotating in the direction of arrow A shown in FIG. As a result, a latent image is formed on the photosensitive drum 22.

Further, on the downstream side in the rotation direction of the photosensitive drum 22 from the irradiation position of the light beam by the light scanning device 32,
The photosensitive drum 22 faces the peripheral surface of the photosensitive drum 22.
A developing device 38 for supplying toner to the printer is provided. The toner supplied from the developing device 38 adheres to the portion irradiated with the light from the direction of arrow B shown in FIG. 1 by the optical scanning device 32. Thus, a toner image is formed on the photosensitive drum 22.

On the downstream side in the rotation direction of the photosensitive drum 22 from the position where the developing device 38 is disposed (the position at which the axis of the photosensitive drum 22 is suspended), the charging surface for the transfer is opposed to the peripheral surface of the photosensitive drum 22. A body 24 is provided. The transfer charger 24 transfers the toner image formed on the photosensitive drum 22 to the paper 16.

A cleaner 40 is disposed on the downstream side in the rotation direction of the photosensitive drum 22 from the position where the transfer charger 24 is disposed, facing the photosensitive drum 22. The toner remaining on the surface of the photosensitive drum 22 after the transfer is removed by the cleaner 40.

The paper 16 on which the toner image has been transferred is conveyed in the direction of arrow C shown in FIG. A fixing device 34 including a pressure roller 42 and a heating roller 44 is provided downstream of the photosensitive drum 22 in the transport direction of the paper 16. The fixing device 34 heats and pressurizes the paper 16 on which the conveyed toner image has been transferred, and melts and fixes the toner. That is, a so-called fixing process is performed in the fixing device 34, and a predetermined image is formed on the paper 16.

Next, the optical scanning device 32 will be described with reference to FIGS. FIG. 2 shows a schematic configuration of the optical scanning device 32, and FIG. 3 shows a block diagram. The optical scanning device 32 outputs one light beam.

The optical scanning device 32 has an LD 46 as a light source.
And a rotary polygon mirror 48 for reflecting the light beam emitted from the LD 46 and irradiating the photosensitive drum 22 with the light beam.

As shown in FIG. 3, the LD 46 is provided with an LD light emitting section 50 for emitting a light beam, and a photodiode (hereinafter referred to as “PD”) 52 for detecting the light amount. The drive current of the LD 46 is APC (Auto
Power Control) circuit 53. The APC circuit 53 monitors a current value corresponding to a light emission amount of the LD 46 output from the PD 52, and controls a drive current so that the current value becomes a predetermined value.
Thus, the LD 46 always outputs a light beam of a predetermined light amount.

The LD 46 is connected to an LD driver 58 provided on a driving driver board 56 via a switch 54 which is turned ON / OFF based on the result of the life judgment of the LD 46 by a life judgment circuit 68 described later. . This L
The D driver 58 is connected to the comparator 60. The comparator 60 is an image processing IC 6 that generates lighting ON / OFF data (8-bit data) and density data (8-bit data) for each pixel based on the image data.
2 output data and analog screen generator 64
And generates an ON / OFF signal on the order of ns.

That is, the LD 46 is connected to the LD driver 58
ON / OFF based on this ON / OFF signal
The light beam is controlled to be emitted based on the image data. A temperature detector (chip thermistor) 66 is also mounted on the driver board 56 for driving, and the temperature inside the optical scanning device 32 (hereinafter, referred to as the temperature sensor).
"Ambient temperature"). This temperature detection result is used for the life judgment of the LD 46 by the life judgment circuit 68 described later.

A rotary polygon mirror 48 is disposed downstream of the light beam emitted from the LD 46 in the traveling direction. LD
The light beam emitted from 46 is converted from a diffused light beam into a parallel light beam via a collimator lens and a cylinder lens (not shown), and is incident on a rotary polygon mirror 48.

The rotating polygon mirror 48 has a plurality of reflecting surfaces 4 on its side.
8A is formed in a regular polygonal shape (a regular hexagon in this embodiment), and the incident light beam is converged on the reflection surface 48A.

The rotary polygon mirror 48 is mounted on a motor 70 and rotates in the direction of arrow B about the rotary shaft 72 by driving the motor 70. That is, each reflection surface 48
The angle of incidence of the light beam on A changes continuously and is deflected. As a result, the surface of the photosensitive drum 22 is scanned in the direction of arrow C (scanning direction) with the scanning width M, and the light beam is irradiated on the photosensitive drum 22.

An fθ lens 74 is arranged in the traveling direction of the light beam reflected by the rotary polygon mirror 48. The fθ lens 74 makes the scanning speed when irradiating the photosensitive drum 22 with a light beam a uniform speed, and forms an image point on the peripheral surface of the photosensitive drum 22.

The light beam transmitted through the fθ lens 74 is bent by a reflection mirror (not shown) and
Is irradiated. In the traveling direction of the light beam and on the upstream side in the scanning direction (the right end direction of the photosensitive drum 22), a mirror 76 is provided.
Is arranged. The mirror 76 allows the photosensitive drum 22
The first light beam of each line scan is reflected.

An SOS (Start Of Scan) sensor 78 is arranged in the direction in which the mirror 76 reflects the light beam. Each time the photosensitive drum 22 is scanned, the first light beam of each line scan enters the SOS sensor 78. That is, in the SOS sensor 78, the optical scanning device 32
, The irradiation start timing for each line on the photosensitive drum 22 can be detected. SO
The S sensor 78 is connected to the aforementioned LD driver 58. In the LD driver 58, a signal indicating the irradiation start timing (hereinafter, referred to as “SOS signal”) is used to output the LD4.
The timing of ON / OFF control of No. 6 is measured. Further, the SOS sensor 78 is also connected to a life determination circuit 68.

As shown in FIG. 3, the life judging circuit 68 is composed of lighting time counting circuits 80 and 82 and a lighting time correction circuit / comparison circuit 84.

The lighting time counting circuit 80 comprises a counter 86, a shift register 88 and an integrating circuit 9 as shown in FIG.
0.

The output of the image processing IC 62 and the output of the SOS sensor 78 are connected to the input side of the lighting time counting circuit 80. The lighting time counting circuit 80 includes the SOS sensor 7
The lighting ON / OFF data (8-bit data) and the density data (8-bit data) for each pixel for one line are taken in from the image processing IC 62 in synchronization with the SOS signal from the CPU 8.

The counter 86 counts lighting ON / OFF data taken from the image processing IC 62 for each pixel, and stores the data in the shift register 88 as data for each line.

The integrating circuit 90 integrates the data stored in the shift register 88 and the density data fetched from the image processing IC 62 and performs proportional correction on the density data. As a result, the lighting time (hereinafter, referred to as “line lighting time T _L ”) is obtained for each line, and line lighting time data is created. That is, the lighting time of the ns order, which is difficult to directly count from the ON / OFF signal generated by comparing the output data of the image processing IC 62 with the analog screen generator 64, can be counted for each line.

On the other hand, the output side of the lighting time counting circuit 80
The line lighting time data is connected to the lighting time counting circuit 82, and the created line lighting time data is input to the lighting time counting circuit 82.

The lighting time counting circuit 82 comprises a counter 92 and a register 94 as shown in FIG. The counter 92 sequentially adds the line lighting time of the lighting time data for each line received from the lighting time counting circuit 80, and generates the accumulated line lighting time data in the register 94.
To be stored. That is, the register 94 stores the total line lighting time _TL (hereinafter, referred to as “cumulative line lighting time SUMT _L ”). Further, the lighting time counting circuit 82
The lighting time correction circuit / comparing circuit 84 for determining the life of the LD 46 is connected.

The inter-page signal and the display request signal from the image forming apparatus 10 are input to the lighting time correction circuit / comparison circuit 84. Further, the above-described temperature detector 66 is connected via an A / D converter 96.

Each time the inter-page signal is received, the lighting time correction circuit / comparison circuit 84 takes in the environmental temperature detected by the temperature detector 66.

The lighting time correction circuit / comparison circuit 84
Captures the cumulative line lighting time data stored in the register 94 each time the inter-page signal is received,
The value of the register 94 is reset. This process is synchronized with the inter-page signal, the accumulated line lighting time SUMT _L is a line lighting time of one page cumulative register 94 (hereinafter, this time of "page lighting time Tp") becomes the lighting The time correction circuit / comparison circuit 84,
The register 94 is reset to count the page lighting time Tp of the next print.

The lighting time correction circuit / comparison circuit 84
As shown in FIG. 6, a register 98, a temperature correction coefficient table storage memory 100, an integrating circuit 102, a lighting time stack memory 104, a laser guaranteed time storage memory 106, and a comparison circuit (comparator) 108 It is configured.

The register 98 stores a page lighting time.

The temperature correction coefficient table storage memory 100 stores a table of the environmental temperature and the temperature correction coefficient, so that the temperature correction coefficient corresponding to the environmental temperature detected by the temperature detector 66 can be selected. I have. In addition,
The temperature correction coefficient is a coefficient for converting the deterioration per unit time due to the lighting of the LD 46 at the environmental temperature represented by the above-described equation 5 into the lighting time at the reference temperature.

The integrating circuit 102 integrates the temperature correction coefficient corresponding to the environmental temperature detected by the selected temperature detector 66 and the page lighting time Tp stored in the register 98. That is, the page lighting time Tp depends on the environmental temperature.
(Hereinafter, the corrected time is referred to as “corrected page lighting time Tcp”).

The correction page lighting time Tcp is stored in the lighting time stack memory 104. That is, since the lighting time corrected in temperature for each print is accumulated in the lighting time stack memory 104, the temperature-corrected cumulative lighting time of the LD 46 (hereinafter referred to as “cumulative corrected lighting time Sum”).
T ”) is stored. The cumulative correction lighting time SumT is maintained even when the power is turned off.

The guaranteed laser time storage memory 106 stores a guaranteed time L indicating the lighting life of the LD 46 at the reference temperature.
imT is stored in advance. In the comparison circuit 108, the cumulative corrected lighting time SumT stored in the lighting time stack memory 104 and the laser guaranteed time storage memory 106
Is compared with the guaranteed time LimT stored in the.

The lighting time correction circuit / comparison circuit 84 determines whether or not the LD 46 has reached the end of life based on the comparison result. That is, when the cumulative lighting time SumT is shorter than the guaranteed time LimT, the LD 46 determines that the life is not over, and when the cumulative lighting time SumT exceeds the guaranteed time LimT, the LD 46 determines that the life is over. The life determination is performed immediately after the image forming apparatus 10 is started up or periodically (every predetermined number of processed sheets).

A display circuit 110 is connected to the output side of the lighting time correction circuit / comparison circuit 84. The lighting time correction circuit / comparison circuit 84 displays the display circuit 1 at the end of the life.
10 is operated to display an error on a display panel (not shown) of the image forming apparatus 10. Further, even when a display request signal is input from the image forming apparatus 10, the display circuit 110 is operated to display the remaining life of the LD 46 obtained from the cumulative corrected lighting time stored in the lighting time stack memory 104. . Thus, the user can easily determine whether or not the LD 46 is reusable.

The display circuit 110 includes the LD driver 5
8 and operates even when the LD 46 is not lit (determined by the current value from the PD 52) despite the drive current being supplied. Thus, even if the LD 46 breaks down due to an accident, an error is displayed on the display panel (not shown) of the image forming apparatus 10.

Next, the flow of the image forming process by the image forming apparatus 10 according to the embodiment of the present invention will be described.

When the image forming apparatus 10 is instructed to form an image, the photosensitive drum 22 is uniformly charged by the charger 36, and the light beam emitted from the optical scanning device 32 forms an image to be formed on the paper 16. Irradiated correspondingly. As a result, a latent image is formed on the photosensitive drum 22. The latent image formed on the photosensitive drum 22 is developed by supplying toner by the developing device 38. The developed toner image is transferred to the paper 16 by the transfer charger 24. The paper 16 to which the toner image has been transferred is subjected to a fixing process by a fixing device 34 to form an image, and is discharged to a discharge tray 28.

Next, the life determination circuit 68 of the optical scanning device 32
Will be described with reference to FIG. FIG.
2 shows a flowchart of the failure determination process.

When the power of the image forming apparatus is turned on (step 300), in step 302, the cumulative lighting time Sum stored in the lighting time stack memory 104.
T is compared with the guaranteed time LimT stored in the laser guaranteed time storage memory 106. Cumulative lighting time Su
If mT is longer than the guaranteed time LimT (negative determination), it is determined that the LD 46 has expired and has failed, and the process proceeds to step 304.

In step 304, the display circuit 110 is operated to display an error on a display panel (not shown) of the image forming apparatus. At this time, the switch 54 is turned off so that the photosensitive drum 22 is not irradiated with the light beam.
I do.

In step 302, if the cumulative lighting time is shorter than the guaranteed time (affirmative determination), the LD
The reference numeral 46 indicates that the life has not expired, and it is determined that the operation is normal.

In step 306, the switch 54 is turned on.
Then, the LD 46 is connected to the LD driver 58. Thereby, the LD 4 is controlled by the LD driver 58.
From 6, the light beam based on the image data is emitted.

The image forming process is started, and the light scanning device 32
When the light beam is scanned on the photosensitive drum 22 by the
The SOS signal is input from the SOS sensor 78 to the lighting time counting circuit 80 of the life determination circuit 68 every line scanning. When detecting the input of the SOS signal (step 308), the lighting time counting circuit 80 proceeds to step 310 and fetches one line of lighting ON / OFF data and density data from the image processing IC 62.

Next, in step 312, the lighting time is counted from the lighting ON / OFF data taken in, is integrated with the density data, and the lighting time for one line (the line lighting time T) is calculated.
_L ). The obtained line lighting time is sent to the lighting time counting circuit 82, and the accumulated line lighting time SumT _L
(Step 314). Lighting time counting circuit 8
In 2, the accumulated line lighting time SUMT _L is updated to store.

When the scanning of the light beam for one page is completed, the image forming apparatus 10 outputs an inter-page signal to the lighting time correction circuit / comparison circuit 84.

In step 316, the lighting time correction circuit /
It is determined whether or not the comparison circuit 84 has detected an inter-page signal, and if the inter-page signal has not been detected (negative determination).
Returns to step 308. That is, the line lighting time _TL is calculated one after another until the inter-page signal is detected,
It will be added to the accumulated line lighting time SUMT _L stored in the lighting time counting circuit 82. Lighting time correction circuit /
When the comparison circuit 84 detects the inter-page signal (affirmative determination), the process proceeds to step 318.

In step 318, the lighting time counting circuit 8
Lighting time accumulation line lighting time SUMT _L stored in 2 as a page lighting time Tp correction circuit / comparator circuit 8
Take in 4. In order to count the lighting time of the next page, the accumulated line lighting time S of the lighting time counting circuit 82 is counted.
umT _L is reset to 0 hours.

At step 320, the environmental temperature is measured by the temperature detector 66. In step 322, a temperature correction coefficient corresponding to the measured environmental temperature is selected from the temperature correction coefficient table stored in the temperature correction coefficient table storage memory 100.

At step 324, the selected temperature correction coefficient is added to the page lighting time taken at step 316. As a result, a page lighting time corrected by the environmental temperature, that is, a corrected page lighting time Tcp is obtained.

In step 326, the calculated corrected page lighting time Tcp is added to the cumulative corrected lighting time SumT.

In step 328, it is determined whether the image forming process is completed and the power of the image forming apparatus 10 is turned off. If the image forming process is subsequently performed (negative determination), the process returns to step 308. That is, one image forming process is performed before the power of the image forming apparatus 10 is turned off.
Each time a page is performed, a corrected lighting time Tcp corrected based on the ambient temperature of the LD 46 is calculated and sequentially added to the cumulative corrected lighting time SumT.

When the image forming process is completed (positive determination),
Proceed to step 330 to turn off the power of the image forming apparatus 10
Then, the process returns to step 300. As a result, when the image forming apparatus 10 is turned on next time and started up, first, the cumulative correction lighting time SumT and the guaranteed time LimT in which the LD lighting time by the image forming process performed during the current power-on are added. Is determined, and a failure determination is made as to whether or not the life of the LD 46 has expired.

(Second Embodiment) Next, an optical scanning device that outputs a plurality of light beams will be specifically described with reference to an example in which three light beams are output. FIG. 8 is a block diagram of the optical scanning device 32 that outputs three light beams. The members described in the first embodiment are denoted by the same reference numerals as those in FIG. 3, and the description is omitted.

The LD 46 as a light source of the optical scanning device 32 is provided with three LD light emitting units 50 for emitting light beams, and each of the LD light emitting units 50 emits a light beam. That is, the LD 46 outputs three light beams. The LD light emitting units 50 are each connected to an APC circuit, and are individually supplied with a drive current.

Also, the PD 5 corresponding to each LD light emitting unit 50
2 (only one is shown and omitted in FIG. 3), and each APC circuit monitors the output light amount from each LD light emitting unit 50 that supplies a drive current, and outputs a predetermined light amount. Is controlled so as to output a light beam.

The optical scanning device 32 includes a switch 54 and an LD driver 5 so as to correspond to each of the LD light emitting units 50.
8, three comparators 60, three analog screen generators 64, and three image processing ICs 62 are provided and connected in the same manner as in the first embodiment (in FIG. 3, the comparator 60, the analog screen generator 64, Only one image processing IC 62 is shown and omitted.

The life determining circuit 68 also includes three lighting time counting circuits 8 corresponding to the respective LD light emitting units 50.
0 and 82 are provided and connected in the same manner as in the first embodiment. That is, the lighting time is counted for each LD light emitting unit 50. The outputs of the three lighting time counting circuits 82 are connected to a lighting time correction circuit / comparison circuit / maximum time comparison circuit 112.

The lighting time correction circuit / comparison circuit / maximum time comparison circuit 112 has a register 9 as shown in FIG.
8, integrating circuit 102, and lighting time stack memory 10
4 are provided three each. Further, a memory 100 for storing a temperature correction coefficient table and a memory 1 for storing a laser assurance time.
06, the comparison circuit 108 and the maximum lighting time comparison circuit 114
Is provided.

The inter-page signal is input from the image forming apparatus 10 to the lighting time correction circuit / comparison circuit / maximum time comparison circuit 112. The lighting time correction circuit / comparison circuit / maximum time comparison circuit 112 is detected by the temperature detector 66 every time an inter-page signal is received, similarly to the lighting time correction circuit / comparison circuit 84 of the first embodiment. Then, the temperature correction coefficient corresponding to the environmental temperature is selected from the temperature correction coefficient table storage memory 100. The register 94 of each lighting time counting circuit 82
From the cumulative line lighting time data Su of each LD light emitting unit 50
The mT _L stored in the register 98 captures as the pages lighting time Tp of each LD light emitting section 50, also resets the registers 94 at the same time.

In each integrating circuit 102, the temperature correction coefficient corresponding to the environmental temperature detected by the selected temperature detector 66 and the page lighting time Tp stored in each register 98
And are integrated. That is, in each integrating circuit 102, each L
The corrected page lighting time Tcp of the D light emitting unit is obtained, and each corrected page lighting time Tcp is determined by the lighting time stack memory 10.
4 is stored. That is, the cumulative correction lighting time SumT of the corresponding LD light emitting unit 50 is stored in each lighting time stack memory 104.

The maximum lighting time comparison circuit 114 is provided for each of the LD light emitting units 5 stored in the lighting time stack memory 104.
The cumulative correction lighting time SumT of 0 is compared to determine the maximum value, and the maximum cumulative correction lighting time MaxSumT is determined.

The comparison circuit 108 compares the obtained maximum cumulative corrected lighting time MaxSumT with the guaranteed time LimT stored in the laser guaranteed time storage memory 106.

On the basis of the comparison result, the lighting time correction circuit / comparison circuit / maximum time comparison circuit 112
Is a service life determination as to whether or not is the service life. That is, 3
If at least one of the LD light emitting units 50 is turned on beyond the guaranteed time, it is determined that the LD 46 has reached the end of its life.

Next, the failure determination of the LD 46 performed by the life determination circuit 68 of the optical scanning device 32 that outputs three light beams will be described. FIG. 10 shows a flowchart of the failure determination process. Note that, in FIG. 10, the same processes as those in the first embodiment have the same step numbers as those in FIG.

When the power of the image forming apparatus is turned on (step 300A), in step 350, the cumulative lighting time SumT of each LD 46 stored in each lighting time stack memory 104 is compared, and the maximum cumulative corrected lighting time is calculated. Ma
Determine xSumT.

In step 352, the maximum cumulative corrected lighting time MaxSumT and the laser guaranteed time storage memory 10
6 is compared with the guaranteed time LimT.
The maximum cumulative lighting time MaxSumT is the guaranteed time Lim
If it is greater than T (negative determination), it is determined that the LD 46 has expired and has failed, and the process proceeds to step 304. That is, if at least one of the three LD light emitting units 50 is turned on for more than the guaranteed time LimT, the LD 46 is determined to have a failure.

At step 304A, an error is displayed on a display panel (not shown) as in the first embodiment.

If the maximum cumulative corrected lighting time MaxSumT is smaller than the guaranteed time LimT in step 352 (affirmative determination), it is determined that the LD 46 has not reached the end of its life and operates normally, and the process proceeds to step 306A. .

After step 306A, each LD light emitting unit 5
For 0, the same processing as in the first embodiment is performed.
That is, until the power of the image forming apparatus 10 is turned off, the corrected lighting time Tcp is calculated for each of the LD light emitting units 50 and is added to the cumulative corrected lighting time SumT.

As described in the first embodiment and the second embodiment, in the present invention, the lighting time of the ns order of the LD 46 used as the light source of the optical scanning device 32 is set as follows.
ON / OFF based on image data from the image processing IC 62
It can be counted from the OFF data and the density data. Further, even when a plurality of light beams are output, the lighting time of the light source (light emitting unit 50) of each light beam can be counted.

Further, the lighting time is corrected based on the environmental temperature, and is converted into the lighting time at the reference temperature. As a result, the state of the laser depending on the environmental temperature can be accurately grasped, and the remaining lighting time (remaining life) up to the failure criterion can also be grasped. Can be.

In the first embodiment and the second embodiment, a method of preparing a temperature correction table in advance is used as the temperature correction method of the lighting time. However, the present invention is not limited to this. Instead, the lighting time may be corrected by hardware, or the lighting time may be corrected by software, by incorporating the temperature detection data and the above equation 5 into a control circuit.

The temperature detector is mounted on a driving driver board 56 provided near the LD 46, and the temperature detector is mounted on the LD 46.
Although the temperature in the vicinity is measured, the temperature is not limited to this, and the temperature in the image forming apparatus 10 may be measured. If possible, attach to LD46 and LD4
If the temperature of No. 6 is measured, more accurate temperature correction can be performed.

[0130]

As described above, according to the present invention, there is provided an optical scanning device capable of accurately grasping the current state of a semiconductor laser even when used under an environmental temperature different from the reference temperature. it can.

[Brief description of the drawings]

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

FIG. 2 is a schematic configuration diagram of an optical scanning device according to the present embodiment.

FIG. 3 is a block diagram illustrating a functional configuration for determining a failure of the semiconductor laser (when one laser is lit) according to the present embodiment;

FIG. 4 is a block diagram illustrating a schematic configuration of a lighting time counting circuit (line lighting time) according to the present embodiment.

FIG. 5 is a block diagram showing a schematic configuration of a lighting time counting circuit (page lighting time) in the present embodiment.

FIG. 6 is a block diagram illustrating a schematic configuration of a lighting time correction circuit / comparison circuit according to the present embodiment.

FIG. 7 is a flowchart illustrating a failure determination process of the semiconductor laser according to the present embodiment (when one laser is lit).

FIG. 8 is a block diagram showing a functional configuration for determining a failure of the semiconductor laser (when n pieces of the semiconductor laser are lit) according to the present embodiment;

FIG. 9 is a block diagram showing a schematic configuration of a lighting time correction circuit / comparison circuit / maximum time comparison circuit in the present embodiment.

FIG. 10 is a flowchart showing a failure determination process (at the time of n lighting) of the semiconductor laser according to the present embodiment.

FIG. 11 shows a change characteristic of a guaranteed time of a semiconductor laser depending on an environmental temperature and the number of lightings.

FIG. 12 shows a state transition characteristic of a semiconductor laser.

FIG. 13 shows a survival rate of an optical scanning device using a plurality of light beams.

FIG. 14 is a schematic configuration diagram of a conventional semiconductor laser deterioration detection device using a driving current.

FIG. 15 is a schematic configuration diagram of a conventional semiconductor laser deterioration detection device using differential efficiency.

[Explanation of symbols]

Reference Signs List 10 image forming device 32 optical scanning device 46 semiconductor laser 62 image processing IC 66 temperature detector 68 life determination circuit 80 lighting time counting circuit (counting means) 82 lighting time counting circuit (counting means) 84 lighting time correction circuit / comparing circuit ( State determination means,
100 temperature correction coefficient table storage memory 102 integration circuit 104 lighting time stack memory 106 laser guaranteed time storage memory 108 comparison circuit 110 display circuit 112 lighting time correction circuit / comparison circuit / maximum time comparison circuit (state determination means) , Correction means, comparison means) 114 Maximum lighting time comparison circuit

Claims (3)

[Claims] 1. An optical scanning device for lighting a semiconductor laser according to image data, comprising: counting means for counting a lighting time of the semiconductor laser; and a counting time by the counting means and a preset reference lighting time. An optical scanning device, comprising: a state determination unit configured to determine a current state of the semiconductor laser based on the above. 2. An optical scanning device for lighting a semiconductor laser in accordance with image data, wherein the counting means counts a lighting time of the semiconductor laser; the state determining means detects a temperature; Correcting means for correcting the counting time by the counting means based on the temperature detected by the detecting means; a correction counting time corrected by the correcting means; and a reference lighting time set in advance, An optical scanning device, comprising: state determination means for determining a current state of a semiconductor laser. 3. The optical scanning device according to claim 1, wherein the counting unit calculates and counts a lighting time of the semiconductor laser based on the image data.