JP2625765B2 - Resolution measuring device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to a resolution measuring device for an image recording device such as a laser printer.

[Conventional technology]

As is well known, a digital copying machine using a laser printer or a laser scanner modulates a laser beam generated from a laser light source with an image signal to be recorded, deflects the laser beam with a scanner such as a rotary polygon mirror, and lays a latent image on a photoconductor. A latent image is formed on a photoconductor by scanning an image forming range, and the latent image is developed by a developing device and transferred and recorded on a recording sheet.

In this type of laser printer or the like, the resolution is uniquely determined by the rotation speed of the scanner motor.

On the other hand, 240, 300, 400, 480 SPI
(Spot Per Inch) and other types of resolutions are manufactured integrally with the scanner. For example, when commercializing a laser printer with a resolution of 240 SPI, a printer with a 240 SPI scanner motor capable of adapting to all resolutions Built into the main body.

Therefore, the printer main body is provided with a resolution selection setting means so as to be able to correspond to all of a plurality of types of resolutions, and when the installation of the scanner motor is completed, the resolution corresponding to the scanner motor is selected and set to correspond to the resolution of the scanner motor. The video clock signal is selectively set.

[Problems to be solved by the invention]

However, in the configuration in which the resolution is set for each of the scanner motors incorporated in the printer main body as described above, there is a problem that the operation of setting the resolution is troublesome, and the recorded image is disturbed due to a setting error. In addition, a setting means such as a switch or a numeric keypad for selecting and setting the resolution must be provided, and there has been a problem that it is expensive.

SUMMARY OF THE INVENTION An object of the present invention is to provide a resolution measuring device for a laser printer, which can eliminate the need for a resolution setting operation and setting means.

[Means for solving the problem]

According to the present invention, the rotation speed of the scanner
Detecting means for detecting with a laser light detection pulse or the like obtained in each scanning cycle, and determining means for determining the resolution based on the detection output of the detecting means are provided. This is an automatic setting.

(Operation) The determining means determines the resolution based on the detection output of the rotation speed of the scanner motor. Then, the resolution is automatically set based on the determination result. Thereby, the video clock corresponding to the rotation speed of the scanner motor is automatically set. Therefore, it is not necessary to set the resolution each time the scanner motor is assembled, and the resolution setting means itself is not required.

〔Example〕

FIG. 1 is a block diagram of a laser printer to which the present invention is applied. A laser oscillator 2 is provided inside a printer main body 1, and a laser beam output from the laser oscillator 2 is transmitted to a printer control unit 3. The signal is modulated by an image signal input from the host computer 4 via the host computer 4. The modulated laser light is deflected by a scanner 6 rotated and driven by a scanner motor 5 and is incident on a photosensitive drum 9 via a lens 7 and a mirror 8.

The photosensitive drum 9 is driven to rotate in the direction of the arrow shown in the drawing, enables scanning in the sub-scanning direction by laser light, and an image to be recorded is formed as an electrostatic latent image by combination with scanning in the main scanning direction by the scanner 6. You. After the electrostatic latent image formed on the photosensitive drum 9 is developed by the developing device 10, the electrostatic latent image is transferred by the transfer corotron 13 to the recording paper sent from the paper feed tray 11 or the manual feed tray 12. After the transfer, the recording paper is fixed to the image by the fixing device 14 and is discharged to the discharge tray 15. In addition, 16 and 17 are paper feed rolls.

The printer control unit 3 controls the entire image forming operation as described above. However, in a standby state waiting for the input of an image signal from the host computer 4, the printer motor 3 stops the scanner motor 5 and causes the scanner motor 5 to rotate at a high speed. The accompanying noise is reduced. However, when an image signal to be recorded is input from the host computer 4, the image signal is stored in an internal buffer memory, and then the rotation of the scanner motor 5 is started. When the scanner motor 5 reaches the rated rotation speed, an image signal is input to the laser oscillator 2,
The modulation of the laser beam is started, and the exposure of the photosensitive drum 9 by the laser beam and the subsequent image forming operation such as development and transfer are started.

The printer control unit 3 controls the image forming operation as described above, but detects the rotation speed of the scanner motor 5 only once when the power is turned on, selects a video clock signal corresponding to the rated rotation speed, and sets a subsequent image. Control the forming operation.

In this embodiment, the rotation speed of the scanner motor 5 is detected as follows.

That is, as shown in FIG. 2, a detector 18 for detecting the laser beam LZ input via the mirror 8 is located near the scanning start position of the laser beam in the main scanning direction of the photosensitive drum 9.
(Hereinafter, referred to as an SOS sensor for detecting a scanning start position).

The detection pulse S of the laser beam obtained from the SOS sensor 18
The period T of the OSP corresponds to the rotation speed of the scanner motor 5.

Therefore, the printer control unit 3 starts measuring the cycle T of the SOS sensor 18 using an internal software counter,
When the rotation of the scanner motor 5 is stabilized at the rated rotational speed, the rated rotational speed is determined. Then, a crystal oscillator that outputs a video clock signal having a cycle corresponding to the detected rated rotational speed is selected from among a plurality of crystal oscillators provided to support a plurality of types of resolutions, and this crystal oscillator is used for subsequent image formation. Used for operation.

FIG. 3 is a flowchart showing a resolution setting procedure, in which the rotation of the scanner motor is started after the power is turned on (step 20), and the rotation speed is adjusted after a lapse of a certain period of time when the rotation of the scanner motor is stabilized at the rated rotation speed. Detect (Steps 21 and 22). Then, it is determined whether the resolution is, for example, 300 spi, 400 spi, or 480 spi based on the detected rotation speed (step 23), a video clock is selected according to the determined resolution, and the scanner motor is stopped (steps 24 to 24). ).

FIG. 4 is a timing chart showing the relationship between the video clock signal Vck output from the selected crystal oscillator, the detection pulse SOSP of the laser beam, and the like. FIG. 4A shows the detection pulse SOSP, and FIG. Synchronization signal L of image signal in scanning direction
S, FIG. 4C shows the video clock signal Vck, and FIG. 4D shows the on / off control signal LZC of the laser light LZ. If the video clock signal Vck is determined, the printer control unit 3 turns on the laser light. The ON section and the OFF section of the / OFF control signal LZC are determined as shown in the figure. Here, T1 in the figure is a time until the laser light LZ is turned off after the detection of the SOS signal, T2 is a time until the laser light is turned on to start modulation of the laser light by the image signal, and T3 is an image signal. And T4 represent the time until the laser beam is turned on again to extract the SOS signal in the next scanning cycle.

The printer control unit 3 detects the rated rotation speed of the scanner motor 5 as described above, selects a video clock signal Vck corresponding to the rated rotation speed, and then waits for an input of an image signal from the host computer 4. .

As described above, the rated rotation speed of the scanner motor 5, that is, the resolution is determined based on the cycle of the output signal SOSP of the SOS sensor 18, and the video clock signal corresponding to the resolution is automatically selected and set. The manual operation of selecting and setting the resolution, which is performed every time the scanner motor 5 is incorporated into the printer main body 1, can be omitted.

In addition, the means for manually selecting and setting the resolution is not required, and the disturbance of the image due to the setting error can be prevented.

In the embodiment, the rotation speed of the scanner motor 5 is detected by the output signal SOSP of the SOS sensor 18. However, the rotation speed is directly detected by an output signal of a tachogenerator or a rotary encoder coupled to the rotation shaft of the scanner motor 5. A similar effect can be obtained with a configuration for detection. However,
In the case of using the SOS sensor 18, the detection of the rotational speed and the detection of the scanning start position can be performed by one sensor, which is economical.

In the embodiment, the laser printer has been described as an example. However, the present invention can be similarly applied to a digital copying machine using a laser scanner.

〔The invention's effect〕

As described above, according to the present invention, focusing on the fact that the resolution of the laser printer is uniquely determined by the rotation speed of the scanner motor, the rotation speed of the scanner motor is detected, and the resolution is determined based on the rotation speed. Since the video clock signal and the like are automatically selected and set according to the determined resolution, manual setting means and setting operation of the resolution are not required, and effects such as shortening of assembly adjustment time can be obtained.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing one embodiment of a laser printer to which the present invention is applied, FIG. 2 is a layout diagram of a laser beam detector viewed from the same plane as a scanning plane of a laser beam, and FIG. FIG. 4 is a flowchart showing the procedure, and FIG. 4 is a timing chart of a video clock signal and the like set after the resolution is determined. DESCRIPTION OF SYMBOLS 1 ... Printer body, 2 ... Laser oscillator, 3 ... Printer control part, 4 ... Host computer, 5 ... Scanner motor, 6 ... Scanner, 9 ... Photosensitive drum, 10 ...
Developing device, 18 ... Laser light detector.

Claims (2)

(57) [Claims] An image recording apparatus comprising a laser light source, a scanner for deflecting and scanning laser light output from the laser light source, and a scanner motor for rotating the scanner, wherein a rotation speed of the scanner motor is detected. A resolution measurement device comprising: a detection unit that performs the determination; and a determination unit that determines the resolution based on the detection output of the detection unit. 2. The apparatus according to claim 1, wherein said detecting means detects a rotation speed of the scanner motor based on a period of a detection pulse of a detector provided at a scanning start position or an end position of laser light. The resolution measuring device according to the item.