JPS595082A - Generating circuit for printing timing pulse - Google Patents

Abstract

PURPOSE:To prevent printing errors and quality degradation from occurring due to an irregularity in a linear scale, by providing a circuit means for correcting the DC level of a read signal to be constant when optically reading a linear scale. CONSTITUTION:Light emitted from a light-emitting diode 11 is received by a photo-transistor 31 through the linear scale 10 such as a steel scale provided with a slit pattern. The read signal (a) containing an increment or decrement is amplified by an amplifier 32 such as a differential amplifier. An output signal from the amplifier 32 is rectified and smoothed by a rectifying circuit 33, which sets a time constant for a C-R combination so as to leave only the increment or decrement (b) of the read signal (a). When the increment or decrement (b) is inputted to a page-side input terminal of the amplifier 32, an output (c) from the amplifier 32 is corrected so that the DC level becomes constant. The output (c) from the amplifier 32 is converted into a pulse by a comparator 34, which pulse is used as a printing timing pulse.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a print timing pulse generation circuit for a printer or the like.

Printers that print by reciprocating movement have a printing density (for example, 3 dots/rrrm or 6 dots) in order to print accurately and precisely at the same intervals on recording paper.
A commonly used method is to provide a linear scale with a black-and-white pattern or slits corresponding to (/rrrm), and to optically read this and use it as a timing signal for printing.

There are various methods of linear scales, each with their own advantages and disadvantages. For example, a resin film scale with a black and white pattern of 11 mm can be made with relatively high accuracy.

However, resin film scales lack long-term reliability, such as the occurrence of errors due to adhesion of dust from recording paper and ink mist from inkjet recording methods. Therefore, a 3-beam steel scale with a slit pattern etched on it is often used. However, in the case of steel scale,
Etching unevenness deteriorates the slit width accuracy, which appears as fluctuations in DC level and amplitude when read optically, and when converted to pulses, becomes waveform distortion, leading to printing errors and deterioration of printing quality. Therefore, it is necessary to correct this. This correction is usually performed by correcting amplitude fluctuations.

Generally, an AGC circuit is often used to correct amplitude fluctuations. An example of this is shown in FIG. light emitting diode 1
1 is received by a phototransistor 12 through a steel scale of 1°, and converted into a single frequency by a bandpass filter 13. This signal is amplified by an amplifier 14. The output of the amplifier 14 is rectified and smoothed by a rectifier circuit 17 and input to the light emitting side of the photoelectric conversion element 15. CdS of photoelectric conversion element 15
The side serves as a feedback resistor of the amplifier 14, and changes the degree of amplification according to fluctuations in the smoothed output so that the vibration output remains constant. A comparator 16 compares the output of the amplifier 14 with a predetermined value and generates a pulse accordingly.

In the case of an AGC circuit having such a configuration, the effect cannot be achieved unless the frequency is a single frequency, so a bandpass filter 3 is inserted for the purpose of achieving a single frequency.

Incidentally, in the case of a printer, the print head is often moved back and forth according to a speed diagram as shown in Figure 2a, but in this case, in order to increase the efficiency of the printer or to control the print position or motor, the print head must be decelerated. , a timing pulse for the acceleration section is required, and it is necessary to generate a timing pulse with a waveform as shown in FIG. However, the first
As shown in the figure, since a band pulse filter 13 is included in the timing pulse generation circuit, when using an AGC circuit, low frequencies are cut by the band pass filter 13 as shown in Figure 2C, It is not possible to obtain the waveform shown in Figure 2a.

The present invention eliminates these drawbacks.

A detailed explanation will be given below with reference to the drawings.

5 bekaoru? FIG. 3 is a circuit diagram showing an embodiment of the print timing pulse generating circuit according to the present invention, and FIGS. 4 a to 4 c are waveform diagrams of each part thereof.

Light from a light emitting diode 11 is received by a phototransistor 31 via a linear scale 10 such as a steel scale with a slit pattern.

The read signal A (see FIG. 4a) obtained from the phototransistor 31 and containing fluctuations is amplified by an amplifier 32, such as a differential amplifier. The output signal of the amplifier 32 is rectified and smoothed by a rectifier circuit 33. Rectifier circuit 33
The time constant of the CR is set so that only the fluctuation portion of the read signal A (see FIG. 4) remains. The amplifier 32
When input to the negative side input terminal of the amplifier 32, the output cover of the amplifier 32 is corrected so that the DC level becomes constant as shown in FIG. 4(C). The output of the amplifier 32 is compared with a voltage near the DC level by a comparator 34 and converted into a pulse.
Used as print timing pulse. In this case, for example, a zero-cross detector may be used as the comparator.

In the configuration shown in FIG. 3 on page 6, the amplitude is not corrected, but the DC level is corrected to a constant value, so by setting the comparison reference voltage of the comparator near that value, a stable print timing pulse can be obtained. In fact, unlike the case of an AGC circuit, there is no need to use a single frequency, so even low-frequency components are not cut, and timing pulses can be generated at a corresponding frequency.

As described above, the present invention optically reads a linear scale with a slit pattern, corrects the DC level of the read signal to be constant, and generates a print timing pulse based on this corrected signal. The printing timing pulse generation circuit configured to do this can reliably prevent printing errors and deterioration of printing quality caused by uneven etching during linear scale manufacturing.

Figures 2 &-'-C are waveform diagrams showing an example of the scanning speed of the print head and the read signal near foldback, and Figure 3 is a circuit diagram showing implementation example 1 of the print timing pulse generation circuit according to this standard. , FIGS. 4a-c are waveform diagrams of the circuit of FIG. 3.

10...Steel scale, 11...Light emitting diode, 31...Phototransistor, 32...
...Amplifier, 33... Rectifier circuit, 34...
···comparator.

Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure O Figure 2 tθ1 Figure 3/θ

Claims (1)

[Scope of Claims] 0) A circuit means for optically reading a linear scale provided with a slit pattern corresponding to the printing density, a circuit means for correcting the DC level of the read signal to a constant level, and a circuit means for correcting the DC level of the read signal to a constant level, 1. A print timing pulse generation circuit characterized by comprising circuit means for converting into. (2) The printing according to claim 1, wherein the correction circuit means comprises an amplifier, a rectifier circuit for rectifying the output of the amplifier, and means for applying the output of the rectifier circuit to the amplifier so as to subtract it. Timing pulse generation circuit. (3) The print timing pulse generation circuit according to claim 1, wherein the circuit means for converting into pulses is a voltage comparator that uses a voltage near a DC level as a reference voltage for comparison. (4) The print timing pulse generation circuit according to claim 1, wherein the voltage comparator is a zero-cross detector.