JP2809400B2 - Laser printer output control method for laser printer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] The present invention relates to a laser light output control method of a laser printer for controlling an emission light level of a semiconductor laser for a light source. In the laser printer having two systems of light output control units for controlling the output light level of the semiconductor laser to a low level for printing and a high level for detecting a writing start position at the left end of the paper, the operation of the semiconductor laser for each line is performed during a printing period. In the previous time, the low-level light output control unit and the high-level light output control unit are sequentially operated one by one to control each light output level to a predetermined level, and the controlled predetermined level is set to the low level. It is characterized in that the light output control unit continuously holds the print output level for a print time of one line and sets the print level.

[Industrial applications]

The present invention relates to a laser light output control method for a laser printer that controls an emission light level of a semiconductor laser for a light source.

[Conventional technology]

In a laser printer device, the timing of the paper left end writing position is usually detected by a signal obtained by receiving scanning light with an optical sensor installed in front of the writing position.

FIG. 3 is a block diagram of a laser beam control system of a conventional laser printer. This laser light control system uses a normal feedback control system. In the drawing, reference numeral 1 denotes a semiconductor laser, 2 denotes a photodiode for monitoring a laser beam incorporated in the semiconductor laser 1, 3 denotes a transistor for driving the semiconductor laser 1, R denotes a resistor, and 4 denotes a drive voltage supply unit for the semiconductor laser 1. .

When a required voltage is applied from the drive voltage supply unit 4 to the base of the transistor 3, the transistor 3 is turned on and the resistor R is applied by the voltage + V applied to the semiconductor laser 1.
A current flows through the semiconductor laser 1 via the semiconductor laser 1, and a laser beam having an amount of light corresponding to the supply voltage of the drive voltage supply unit 4 is emitted.
A current proportional to the light amount of the light flows through the photodiode 2 that has received the laser light.

Reference numeral 5 denotes an optical output level detecting unit which converts the current flowing through the photodiode 2 into a voltage and detects the amount of emitted light, and outputs the converted voltage to one input terminal of the optical output level determining unit 6. provide feedback. Optical output level judging unit 6 is constituted by a comparator, holding control to the other to exit level of the laser light required to the input terminal the low level (so that the output of the optical output level detecting unit 5 becomes the voltage V ₁₎ optical output setting level V ₁ to be a reference to is always applied. The optical output setting level V ₁ was a set value that can be adjusted in response to printing density. The light output level judging unit 6 compares the two input levels and sets the light output set level.
Is higher than V _1, is outputted as a low or binary signal.

Reference numeral 7 denotes an optical output control unit, which has one input terminal connected to the output side of the optical output level determination unit 6 and the other input terminal receiving a timing signal A.

FIG. 4 is a time chart of each part in FIG. 3, in which the horizontal axis represents time, and the vertical axis represents level (however, only the light emitted from the semiconductor laser). FIG. 3 will be described below with reference to FIG.

The timing signal A is a pulse signal that is output for each line to detect the writing position at the left end of the sheet when the laser printer scans for each line, and the timing signal A becomes an effective level. The light output control unit 7 responds to the output of the light output level determination unit 6 so that the emission level of the laser light (ie, the output of the light output level detection unit 5) becomes equal to the light output set level V1 _only at the time. And a function of continuously controlling and outputting the controlled level through the driver amplifier 8 for a printing time of one line. V ₀ and T ₀ shown in the driver amplifier output C of the time chart indicate the held level and the holding time, respectively.

Reference numeral 9 denotes a buffer amplifier, and the print signal P is input to the drive voltage supply unit 4 via the buffer amplifier 9. The drive voltage supply unit 4 is a circuit that supplies an analog signal (voltage V ₀ ) output from the driver amplifier 8 to the base of the transistor 3 using the print signal P as a trigger signal, and is, for example, an open collector logic circuit or an analog switch. Is used. It is assumed that the timing signal A is superimposed on the print signal P.

As a result of driving the semiconductor laser 1 as described above, the emitted light LD emits an optical signal indicating the writing position of the left end of the sheet corresponding to the timing signal A for each line as shown in the time chart. from light sensor (not shown) receives light signals obtained waveform as shown in the time chart of detection signals S, it is possible to determine a line printing time T ₁ set in advance the detection signal as a reference.

[Problems to be Solved by the Invention] In recent years, as the price and size of laser printer devices have been reduced, the sensitivity of the photo-condrum has been successfully increased, and semiconductor lasers having a low output have been used. However, as the amount of light used decreases, the level of the photoelectrically converted electrical signal naturally decreases, making it difficult to distinguish between electrical noise and the electrical signal. As a result, there is a disadvantage that the printing start position fluctuates due to noise and the printing quality deteriorates.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional drawbacks, and controls the laser beam output control method of a laser printer to control the level to a low level at the time of printing and to control the level to a high level immediately before printing at the left end of the paper so as not to deteriorate the printing quality. For the purpose of providing.

[Means for solving the problem]

In order to achieve the above object, according to the present invention, as shown in FIG. 1, the emission light level of the semiconductor laser 1 for the light source is controlled to a low level for printing and a high level for detecting a writing start position at the left end of the sheet. In a laser printer having system light output control units 7 and 12, the low-level light output control unit 7 and the high-level light output control unit are operated at a time before a printing period when operating the semiconductor laser 1 line by line. 12 are operated one by one in order to control each light output level to a predetermined level, and the low level light output control unit 7 continuously holds the controlled predetermined level for only one line printing time. The printing level is adopted.

[Action]

Before printing one line, the laser light output for printing is determined by the control of the low-level light output control unit, and the writing start detection at the left end of the paper is detected by the high-level emission light by the control of the high-level light output control unit. Can be done accurately. Therefore, printing can be started from an accurate writing position with a predetermined laser beam output, and a high quality printing result is obtained.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition,
To facilitate understanding of the description of the configuration and operation, the same portions are denoted by the same reference numerals throughout the drawings, and redundant description will be omitted.

FIG. 1 is a block diagram showing the configuration of the present invention. In the figure, an analog switch 10 is provided as a switching means 10 on the output side of the optical output level detector 5, and an analog switch 13 is provided as a level switching means 13 on the input side of the driver amplifier 8. Each of the analog switches 10 and 13 is driven in conjunction with the timing signal B.

FIG. 2 is a time chart of each part in FIG. 1, and FIG. 1 will be described below with reference to FIG. The timing signal B is a signal which rises at the falling edge of the timing signal A as shown in the time chart. The timing signal B is intended to synchronize with the timing signal B to obtain a high-level laser beam at the left end writing position of the sheet. is there. It is also assumed that timing signals A and B are superimposed on the print signal P 'shown in the time chart.

Reference numeral 11 denotes an optical output high level determining unit, and 12 denotes an optical high output control unit, each of which has a configuration of a conventional optical output level determining unit.
6 is the same as the optical output control unit 7, the former is high enough for the required level is set higher than the voltage V ₂ is the voltage V ₁ applied as an optical output setting level, the latter timing signals B Is applied. For convenience of description, the light output level determination unit 6 and the light output control unit 7 of the conventional example will be referred to as a light output low level determination unit 6 and a light low output control unit 7, respectively.

First, the analog switches 10 and 13 are connected to the contact a
When it is tilted to the side, it is the same as the conventional laser light control method described with reference to FIG. Next, when the pulse of the timing signal B is inputted, the analog switches 10 and 13 are respectively tilted to the contact b side, and the optical output high level judging section 11 outputs the level fed back from the optical output level detecting section 5 and the optical output set level V Outputs the difference from ₂ . Reference numeral 12 denotes a high output control unit, which has one input terminal connected to the output side of the optical output high level determination unit 11 and the other input terminal connected to a timing signal B.
Is entered.

The timing signal B is a pulse signal added to the timing signal A output for each line to detect the writing position at the left end of the paper when the laser printer scans for each line. B is emitted level of the laser beam and out only when it becomes an effective level that is, the optical high-power controller 12 so that the output of the optical output level detection unit 5 is equal to the light output set level V ₂ performs the level control The high-level emission light is output from the semiconductor laser 1 via the driver amplifier 8.

When the timing signal B becomes an invalid level, the optical output control is stopped, and the analog switches 10 and 13 are switched to the contact a side in conjunction with each other, and the driver is controlled by the control voltage held in the optical low output control unit 7 as before. through the amplifier 8 and supplies a control voltage V ₀ to a driving voltage supply unit 4 as shown in the time chart C 'only in T ₀ 1 line of printing time.

That is, the time during which the light output control is performed at a high level is a short time corresponding to the pulse width of the timing signal B as shown in the time chart LD ', and the high level emission time is used to detect the writing position at the left end of the sheet. It is adjusted to cover the period during which the detector is irradiated with light. By receiving the high-level laser light by an optical sensor (not shown), a good S / N detection signal can be obtained as shown in a time chart S '. This detection signal is used as a reference for the writing position at the left end of the sheet. Can be used as

By adopting this method, when printing, the semiconductor laser emits light at a low output level according to the print density, and at the writing position at the left end of the paper, emits at a high output level, so that a good S / N detection signal can be obtained. Since the light output control is performed even at the time of light emission at a high output level, a stable detection signal can be obtained.

〔The invention's effect〕

As is apparent from the above description, according to the present invention, the light output level for printing is determined in advance before printing one line, and the light amount of the semiconductor laser is increased so that a stable detection signal can be obtained. Therefore, printing can be performed from a correct writing position with a constant laser beam, and there is an effect of improving quality.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the configuration of the present invention, FIG. 2 is a time chart of each part in FIG. 1, FIG. 3 is a block diagram of a laser beam control system of a conventional laser printer, and FIG. 3 shows a time chart. In FIG. 1, 1 is a semiconductor laser, 7 is an optical output control unit (optical low output control unit), 10 is a switching unit, 12 is an optical output control unit (optical high output control unit), and 13 is a level switching unit. Show.

Continuing from the front page (72) Inventor Yasuo Numata 1015 Uedanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture Inside Fujitsu Limited (72) Inventor Mitsuhiko Kobayashi 1015 Uedanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture Fujitsu Limited (56) References JP-A-60-245364 (JP, A)

Claims (1)

(57) [Claims] 1. A laser printer comprising two systems of light output control units for controlling the emission light level of a semiconductor laser for a light source to a low level for printing and a high level for detecting a writing start position at the left end of a sheet. At the time before the printing period in the operation for each line, the low-level light output control unit and the high-level light output control unit are sequentially operated one by one to control each light output level to a predetermined level. A laser light output control method for a laser printer, wherein the low-level light output control unit continuously holds the controlled predetermined level for a printing time of one line and sets it as a printing level.