JPH04255815A - Scanning start end detecting mechanism - Google Patents

Abstract

PURPOSE:To provide the scanning start end detecting mechanism which detects the scanning start end position of an electronic printer and can set an accurate printing start position without considering the fitting position accuracy of a photodetection sensor by detecting the absolute position of a photosensitive drum. CONSTITUTION:A beltlike mark 21 which is different in reflection factor or reflection direction from other parts of the photosensitive drum 2 is formed on the peripheral surface of the photosensitive drum 2 at the scanning start end position P0 and reflected light B1 from the beltlike mark 21 is photodetected by the photodetection sensor 30a to generate a start end signal S0. Consequently, the photoreceiving sensor 30a can detect the absolute position of the photosensitive drum 2 regardless of its arrangement position accuracy.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical unit for an electronic printing apparatus, and more particularly to a scanning starting edge detection mechanism for detecting a scanning starting edge position.

0002

2. Description of the Related Art FIG. 5 shows a conventional example of an optical unit of an electronic printing apparatus. The laser beam B0 emitted from the laser emitter 1 is transmitted through a condensing lens 5 or a reflecting mirror 3,
By driving the optical polarizer 8 by a driving device (not shown), the laser beam B0 scans the photosensitive drum 2 in the axial direction via the condensing lens 6. It looks like this. A light receiving sensor 30b (with a reflecting mirror 7 interposed in the drawing) is arranged corresponding to this scanning start position P0.
0b directly receives the laser beam B0 from the optical polarizer 8, and as shown in FIG.
A start signal S0 representing the start point signal S0 is formed. This start signal S0
In response, the timing circuit 12 shown in FIG.
When a predetermined time T0 has elapsed since the rise of the bitmap memory 11, that is, when the laser beam B0 reaches the printing start position P1, the readout signal Sr of the bitmap memory 11 is
, input the video signal Vs from the bitmap memory 11 to the driver 10 of the laser emitter 1,
As shown in FIG. 7(b), the laser beam B0 is modulated. This makes it possible to print on paper A from the print start position P1.

Note that a laser diode 1D or a gas laser emitter can be used as the laser emitter 1, and when a gas laser emitter is used, it is necessary to interpose an AO modulator as a laser modulator in the optical path. . Further, a polygon mirror 8p can be used as the optical polarizer 8, and the rotation of the polygon mirror 8p is controlled by the control device 40.

0004

According to the above configuration, the position of the light receiving sensor 30b is the scanning start position P0, that is,
The printing start position P1 will be determined. However,
The light-receiving sensor 30b is configured to directly receive the light from the optical polarizer 8, and although its position corresponds to the scanning start position P0 of the photosensitive drum 2 as described above, strictly speaking, it is located at the position of the laser beam B0. It is merely placed at the predicted position of incidence on the starting end position P0. Moreover, since the light receiving window of the light receiving sensor 30b is small and the scanning speed is fast, in order to accurately match the light receiving sensor 30b to the scanning start position P0, the position must be corrected several times after temporary positioning. It has the disadvantage of being very time consuming.

The present invention was proposed in view of the above-mentioned conventional circumstances, and it is possible to accurately determine the printing start position by detecting the absolute position of the photosensitive drum without considering the accuracy of the mounting position of the light receiving sensor. This provides a scan start end detection mechanism that can be set.

[0006]

[Means for Solving the Problems] The present invention employs the following means to achieve the above object. That is, as shown in FIG. 1, a laser beam B0 emitted from a laser emitter 1 is scanned on a photosensitive drum 2, a starting edge signal S0 is generated corresponding to the starting edge position of the scanning, and the starting edge signal S0 is In a scan start edge detection mechanism of an electronic printing device that modulates a laser beam B0 with print data after a predetermined time T0 from generation to form a latent image on the photosensitive drum 2, a scan start edge detection mechanism of the electronic printing device modulates the laser beam B0 with print data to form a latent image on the photosensitive drum 2. A strip mark 21 having a different reflectance or reflection direction from other parts of the strip mark 21 is formed, and a light receiving sensor 30a receives reflected light B1 from the strip mark 21 to form a start signal S0.

[0007]

[Operation] At the band mark 21 on the photosensitive drum 2,
The reflectance or reflection direction is different from other parts of the photosensitive drum 2. Therefore, the reflected light B1 from that part becomes weaker (or stronger) than other parts, and by detecting this change with the light receiving sensor 3, the position corresponding to the strip mark 21 on the photosensitive drum 2, that is, the scanning This means that the starting position P0 has been detected.

[0008] Therefore, from this position, the printing start position P1
By outputting the print data after the time T0 corresponding to the distance up to this point has elapsed, printing can be started from the desired position on paper A.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of the present invention. The same members as in the conventional configuration will be described using the same reference numerals. The configuration of the optical system is substantially the same as the conventional optical system, except that the conventional light receiving sensor 30b is not placed in the conventional optical unit, so a detailed explanation will be omitted.

On the circumferential surface of the photosensitive drum 2, there is a scanning start position P.
A strip mark 21 indicating that the value is 0 is provided. For example, as shown in FIG. 1, the band-like mark 21 may be colored with a color that has a lower (or higher) reflectance than other parts, or as shown in FIG. The structure is such that the reflection direction is different by tilting the surface to the opposite direction.

A light receiving sensor 30a is arranged at a position where the reflected light B1 from the strip mark 21 on the photosensitive drum 2 is incident. When the band-shaped mark 21 has a different reflection direction from other parts as shown in FIG. A light receiving sensor 30a is arranged at the incident position of the light.

In this configuration, when the polygon mirror 8p, which is the optical polarizer 8, is rotationally driven by the control device 40, the photosensitive drum 2 is scanned by the laser beam B0. The laser beam B0 is emitted from a position slightly before the scanning start position P0, and when it crosses the strip mark 21, the reflected light B1 that enters the light receiving sensor 30a becomes weak. Therefore, the output is as shown in FIG. 4(a).
The light receiving sensor output signal Ss is "0" corresponding to 1, and "1" corresponding to other parts. On the other hand, the timing circuit 12 shown in FIG.
A gate signal Sg is output in the vicinity where the laser beam B0 passes through the strip mark 21, and a signal obtained by inverting the light receiving sensor output signal Ss by the inverter 32 and the gate signal Sg are used by the AND gate 31 to generate the signal shown in FIG. 4(c). A start signal S0 shown in FIG. 1 is output and input to the timing circuit 12. Furthermore, the timing circuit 12 receives this start signal S0.
A read signal Sr for the bitmap memory 11 is formed after a predetermined time T0 from the rise (fall) of
A video signal Vs is input from the bitmap memory 11 to the driver 10, and modulates the laser emitted from the laser diode 1D.

With the above configuration, the light receiving sensor 30a detects the absolute position of the photosensitive drum 2 (the position of the strip mark 21), and even if the positional accuracy of the light receiving sensor 30a is not very high, the laser beam B0 is detected in the strip shape. To surely output a start signal S0 at the timing when a mark 21 is irradiated. That is, since the output timing of the start end signal S0 depends only on the position of the band-shaped mark 21, as long as the processing precision at the time of manufacturing the photosensitive drum 2 is sufficient, the output timing of the start end signal S0 is not affected much by the placement position of the light receiving sensor 30a, and can achieve the purpose. Printing can be started from the position (print start position P1).

[0014]

As explained above, the present invention uses reflected light from a predetermined position of the photosensitive drum to form a scanning start signal, so that the printing start determined based on the start signal is This has the effect that the position can be determined accurately without being greatly influenced by the positional accuracy of the light receiving sensor that forms the starting edge signal.

[Brief explanation of the drawing]

FIG. 1 is a conceptual diagram showing the configuration of the present invention.

FIG. 2 is a conceptual diagram showing a band-like mark of the present invention.

FIG. 3 is a block diagram showing a circuit of the present invention.

FIG. 4 is a timing chart of the present invention.

FIG. 5 is a conceptual diagram of a conventional example.

FIG. 6 is a block diagram showing a conventional circuit.

FIG. 7 is a timing chart of a conventional example.

[Explanation of symbols]

1 Laser emitter 2 Photosensitive drum 21 Band-shaped mark 30a Light receiving sensor B0 Laser beam B1 Reflected light P0 Scan start position S0 Start signal T0 Predetermined time

Claims (2)

[Claims] 1. Scanning a laser beam (B0) emitted from a laser emitter (1) on a photosensitive drum (2) to generate a start signal (S0) corresponding to the start position of the scan, A predetermined time (T
0) Later modulate the laser beam (B0) with print data,
In a scan start edge detection mechanism of an electronic printing device that forms a latent image on a photosensitive drum (2), the peripheral surface of the scan start edge position (P0) of the photosensitive drum (2) has a reflectance that differs from that of other parts of the photosensitive drum (2). Or a strip mark with different reflection directions (21
), and the reflected light (B1
) is received by the light receiving sensor (30a) and the start end signal (S0
). 2. The scan start end detection mechanism according to claim 1, wherein the band-shaped mark (21) has a reflective surface that is inclined with respect to the surface of the photosensitive drum (2).