JPS6258283A - Laser printer capable of indicating light quantity - Google Patents

Abstract

PURPOSE:To easily and accurately measure the quantity of laser light, by dividing the laser light with a beam splitter provided in a laser light path and visually indicating the received quantity of laser light by means of an indicating means, through which the divided laser lights can visually be confirmed from the outside. CONSTITUTION:A beam splitter 7 divides laser light L from an optical system 2 into two parts, one part being directed in the direction l1 toward a photosensitive body 3 and the other part in another direction l2. The laser light directed in the direction l2 is received by each APD 9. A MAX-MIN detecting circuit 20 detects the maximum values and minimum values of light quantity signals corresponding to all surfaces of reflection while a rotating polygon mirror is rotated by an appropriate times and averages the detected values. Each data of 'means value', etc., indicated by means of an indicating means 19 are used as reference values when the laser output of the laser light source is adjusted.

Description

[Detailed description of the invention] Technical field The present invention relates to laser printers.

BACKGROUND ART In general, in a laser printer, a laser beam emitted from a laser beam m is modulated based on an image signal to obtain modulated light, and the modulated light is reflected by a rotating polygon mirror and irradiated onto a photoreceptor. An electrostatic image is thereby formed on the photoreceptor.

This electrostatic image is then formed into a visible image on the printing paper through development, transfer, and fixing operations.

In order to finally obtain a good visible image, it is necessary for the electrostatic image formed on the photoreceptor to be created with a predetermined amount of charge, and for this purpose, it is necessary to irradiate the photoreceptor onto the photoreceptor. The amount of laser light applied must be set to match the characteristics of the photoreceptor. Further, the photoreceptor deteriorates over time, and in that case, it is necessary to adjust the amount of laser light depending on the deterioration.

In conventional laser printers, when adjusting the light intensity, the laser beam is set to unmodulated CW (direct current) light, the photoconductor is removed from the printer body, and the rotating polygon mirror is rotated by hand to align the laser beam with the writing position on the photoconductor. Set the laser beam so that it is centered, and measure the amount of light by shining the laser beam on the sensor part of a well-known power meter.
Based on the measurement results, the amount of laser light emitted from the laser light source was adjusted.

However, since the above-mentioned conventional method performs adjustment based on an arbitrary surface of the rotating polygon mirror, it is not possible to adjust the amount of light in consideration of variations in reflectance between the reflecting surfaces constituting the polygon mirror. Moreover, if an attempt is made to adjust the amount of light by taking this variation into consideration, work efficiency will be significantly reduced. Furthermore, when measuring the intensity unevenness of the laser light intensity in the main scanning direction, the conventional method involves removing the entire optical system including the rotating polygon mirror, and using a special jig to measure the light intensity while moving the polygon mirror little by little. Measurements must be taken, which is very inefficient.

Purpose In view of the above points, an object of the present invention is to provide a laser printer that can easily and reliably measure the amount of laser light while taking into account the variation in reflectance between each reflecting surface of a rotating polygon mirror. shall be.

composition The above object is achieved by the following configuration.

A beam splitter is placed on the photoreceptor from the laser light source, the beam splitter splits the laser light, the split laser light is received by a light receiving element, and the amount of light received by the light receiving element is displayed on a display that can be viewed from outside the printer. Visibly display.

Hereinafter, the present invention will be explained based on Examples.

FIG. 1 shows the general overall shape of a laser printer. This overall shape can be made into various shapes depending on the various types of equipment to which the printer is attached.

For example, the shape is not limited to the illustrated shape, but may be a simple rectangular parallelepiped shape.

The laser printer 1 has an optical system 2 and a belt-shaped photoreceptor 8 inside. The optical system 2 includes a laser light source (not shown), a modulator, and a rotating polygon mirror, and the modulator modulates the laser light emitted from the laser light source based on an image signal, and the resulting modulated light is transmitted to the rotating polygon. The electrostatic latent image is guided to the photoreceptor 8 through a mirror, thereby forming an electrostatic latent image on the photoreceptor 8.

The latent image thus obtained is developed into a developed image by a developing device (not shown), and then transferred to transfer paper stored in the paper feed tray 4, and further fixed onto the transfer paper by a well-known fixing operation. .

Thereafter, the transfer paper is discharged to the outside of the printer l.

As mentioned above, the amount of laser light that exits the optical system 2 and irradiates the photoreceptor 3 must be an appropriate value depending on the characteristics of the photoreceptor 3. In order to adjust the light amount, it is important to know how much laser light is irradiated from the optical system 2 to the photoreceptor 8 in the current state. In this embodiment, the amount of light is measured using the following configuration.

In a laser printer, a light amount detecting means 5 irradiates an optical path from an optical system 2 to a photoreceptor 8. The light amount detection means 5 includes a beam splitter 7 (for example) attached to the lower side of the cylindrical lens 6 as shown in FIG.
- Humira). The beam splitter 7 splits the laser beam from the optical system 2 into two directions: a direction 11 toward the photoreceptor 8 and another direction 12.

In the direction 12 when viewed from the beam splitter 7, there are a plurality of light receiving elements (five in the figure) fixed to a bracket 8 attached to the lower side of the cylindrical lens 6, such as an APD (avalanche photo diode). ) 9 in a laser printer that emits light. Therefore, the light divided into 12 directions is received by each APD 9.

The APD 9 generates a photocurrent according to the amount of received light, and as shown in FIG. . Thereafter, in the logarithmic conversion circuit 18, the output signal from the voltage follower 12 is subjected to logarithmic conversion using a preset reference level as QdB. The reference repé μ is variously set depending on the purpose.

For example, when a predetermined amount of laser light hits the photoreceptor 8, the AP
It can be a signal sent from D9 via the logarithmic conversion circuit 18.

Note that if there are variations in sensitivity among the five APDs 9, accurate light amount measurement cannot be performed. So each APD9
For this, the multiplication degree of each APD can be changed by appropriately adjusting the applied reverse bias voltage, thereby reducing the variation in sensitivity between each APD (variation in photocurrent per unit light amount).
It is desirable to compensate for

The light amount signal logarithmically converted by the logarithmic conversion circuit 13 is then subjected to Aρ conversion by the A/D conversion circuit 14, and then subjected to two processes. One is the adding circuit 1 which adds the light intensity signal obtained when the rotating polygon mirror is rotated an appropriate number of times.
5 and the averaging processing circuit 16 perform averaging processing on each APD 5, and the results are stored in the data memo 1J17.
, is displayed on the display means 19 via the display driver 18.

The display means 19 includes, for example, five APDs 9 as shown in FIG.
(in the figure, the numbers 1 to 5 are attached), and the result of the above-mentioned averaging process is displayed in dB in the [Average 1 column] of the display columns. Ru.

This "average value" for each APD 9 indicates a value obtained by averaging the total light amount data of the laser light reflected from each reflecting surface of the rotating polygon mirror at the same image height position in the main scanning direction.

Another process that the light quantity signal A/D converted by the A/D conversion circuit 14 receives is the MAX-MIN detection circuit 2.
This is done by 0. That is, since there is variation in reflectance among the reflecting surfaces constituting the rotating polygon mirror, the maximum reflectance (MAX) and minimum reflectance (MIN) are different for each reflecting surface.

Accordingly, MAX and MIN also occur in the light amount signals received by each APD 9 and A/D converted accordingly. MAX
- The MIN detection circuit 2o detects the MAX light amount signal corresponding to all the reflecting surfaces while rotating the rotating polygon mirror an appropriate number of times.
This detects the value and the MIN value, and averages them. The detection result is displayed on the display means 19 via the data memory 17 and display driver 18 in the same manner as the above-mentioned "average value" processing. In this case, l'-MAX
Displayed in the J column and the [MINJ column.

Each data such as the "average value" displayed on the display means 19 is
This is used as a reference by the operator when adjusting the laser output from the laser light source. Therefore, it is desirable to install the display means 19 in a place where the operator can easily see it. For example, it is preferable to attach it to the output connector section 21 as shown in FIG.

As described above, the "average value", [MAXJ, [MIN] displayed on the display means 19 that can be observed from the outside of the printer 1
By reading each data of J, the amount of laser light can be measured during the printing operation, that is, while the optical system 2 is actually operating. This means that in the laser printer manufacturing process, after the laser printer is finally assembled,
This means that the light intensity can be measured at the same time as the operation is checked, and the laser output can be adjusted based on the results, leading to a reduction in man-hours in the manufacturing process.

Furthermore, these data are not simply data regarding one reflecting surface of the rotating polygon mirror, but are averaged data based on data from all reflecting surfaces. Therefore, it can be said that the measurement data is highly reliable.

Furthermore, in this embodiment, a plurality (5) of APDs 9 arranged in the main scanning direction are used to measure the amount of light at different image height positions. Therefore, in addition to the variations between the respective reflecting surfaces, it is also possible to measure the variations in the main scanning direction.

In the above embodiment, the beam splitter 7 is placed behind the cylindrical lens 6, and the laser beam is split at this position, but the splitting position may be any other arbitrary position.

In the display means 19, "average value", "MAXJ", "MI
Although three pieces of data for NJ are displayed, at least one piece of data may be displayed.

The reason why the APD 9 was used as the light receiving element is to enable easy correction of variations in sensitivity among the light receiving elements when a plurality of light receiving elements are used. Therefore, when using only one light-receiving element or when using a light-receiving element with uniform sensitivity, it is not necessary to use an APD.

□In the embodiment shown in Fig. 2, one of the APDs 9 is placed at one end of the cylindrical lens 6 (slightly before the main scanning image writing start position), and after receiving light, the writing start timing is controlled from that position. By doing so, the synchronization detection circuit that conventionally controls the write start position can be omitted.

Additionally, if the photoconductor 3 (Fig. 1) deteriorates, it is necessary to increase the laser light intensity accordingly, but by providing a circuit that detects the surface potential of the photoconductor, it is possible to prevent deterioration of the photoconductor. In response to the accompanying change in surface potential, the amount of laser light can be increased appropriately while comparing it with the initial setting value. In this case as well, the display means 19 provides accurate light amount measurement data.

Effects According to the present invention, the amount of laser light can be easily and reliably measured while taking into account the variation in reflectance between the reflecting surfaces of the rotating polygon mirror.

[Brief explanation of the drawing]

1 is an overall perspective view of the laser printer, FIG. 2 is a perspective view of the light amount detection means, FIG. 3 is a circuit diagram up to the light amount display, and FIG. 4 is a plan view of an example of the display means. 7... Beam splitter 9... Light receiving element 19...
・Display means

Claims (1)

[Claims] In a laser printer, a laser beam emitted from a laser light source is modulated based on an image signal to obtain modulated light, and the modulated light is irradiated onto a photoconductor via a rotating polygon mirror. A beam splitter is placed on the laser optical path between the two and splits the laser light into the direction towards the photoconductor and other directions, and a beam splitter that receives the laser light split in the other directions mentioned above and has different levels depending on the amount of light received. A laser printer comprising: a light-receiving element that outputs an electric signal; and display means that can visually display the amount of received light based on the output signal of the light-receiving element and that can visually recognize the visible display from outside the printer.