JPH0488371A - Beam detecting device for image forming device - Google Patents

Abstract

PURPOSE:To attain strength with respect to environmental fluctuations and to easily carry out optical adjustment by carrying out digital output at a slice level different from the slice level of light whose incident light quantity is monitored. CONSTITUTION:When a photodiode 2 on which a reverse bias is applied by a resistance 14 is irradiated with the rays of the light, a photoelectric current is generated, and supplied to a current mirror 9, and a current in proportion to the size of the emitter of the transistor of the current mirror 9 flows from resistance 13 to the current mirror. At this time, a constant voltage drop occurs on the resistance 13, and a voltage that the dropped voltage is subtracted from a power source voltage is generated on a terminal 10. Then, the voltage given to a voltage follower 5 is outputted to a photoelectric current monitor signal terminal 4 as it is, and the voltage given to a hysteresis comparator 6 is compared with a reference voltage produced by resistance 7 and 8 and outputs a horizontal synchronizing signal to output 3 according to the compared result. Further, adjustment is carried out while monitoring the photoelectric current monitor signal 4 and recognizing that slicing is not curried out in a state where a margin does not exest, at the time of the adjustment. Thus, the strength with respect to the environmental fluctuations is attained and the optical adjustment is easily carried out.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a beam detection device for obtaining a horizontal synchronization signal of an image forming apparatus such as a laser beam printer.

[Conventional technology]

FIG. 6 is a perspective view showing a simplified configuration of a conventional laser beam printer, and its image forming operation will be described below. In the figure, 101 indicates an image signal (VDO signal), which is input to the laser unit 102.

Reference numeral 103 indicates a laser beam modulated on and off by the laser unit 102. 104 is a scanner motor that rotates a rotating polygon mirror 105 at a constant speed. 106 is an imaging lens, and a polygon mirror 10
A laser beam 107 deflected by 5 is focused on a photosensitive drum 108. Therefore, the laser beam 107 modulated by the image signal 101 is horizontally scanned (scanned in the main scanning direction) on the photosensitive drum 108. A beam detection port 109 takes in the laser beam from a slit-shaped entrance. The laser beam entering from this entrance passes through the optical fiber 110 and is guided to the photoelectric conversion element 111. The laser beam is converted into an electric signal by the photoelectric conversion element 111, and after being amplified by an amplifier circuit (not shown) on the controller 113, it becomes a horizontal synchronization signal (hereinafter referred to as an ED signal).

112 is a transfer paper, and a toner image obtained by visualizing the latent image formed on the photosensitive drum 108 by a developing device (not shown) is transferred to the transfer paper 11 by a transfer device (not shown).
Transferred to 2.

Among these optical systems, the laser unit 102 and the motor 1
04, the polygon mirror 105, the imaging lens 106, and the optical fiber 110 are individually adjusted as a scanner unit. For example, in order to reliably output the BD double signal, the beam detection port 109 needs to be placed at a predetermined position on the scanning path of the laser beam 107 during the adjustment process of the scanner unit.

For this purpose, it is necessary to use a special jig or device instead of the controller 113 to measure the amount of light incident on the fiber in an analog manner, and to arrange the detection port 109 at a desired position. Also, depending on the device, as shown in Figure 7,
In some cases, the laser beam is guided to the detection port 109 via the reflection mirror 114 for the D signal. In such a case, it is necessary to adjust the reflection mirror 114 so that the laser 107 is irradiated onto the detection port 109.

By using the optical fiber 110 in this way, there are advantages in that the detection port 109 and the controller 113 can be configured without being restricted by the arrangement position, and the noise resistance is improved.

However, the transmittance of optical fibers varies greatly (and in order to include this variation in the BD detection circuit, it is necessary to reduce the variation in other parts, such as reducing the variation in the amplification stage etc.) In addition, since the cost of the optical fiber itself is expensive, there are cases where the controller 113 is placed near the scanner unit, and a configuration that does not require the use of a fiber is sometimes adopted. The configuration is shown in Figure 8.115
is a BD consisting of a light receiving section 116, an amplifier, and a binarization circuit.
It is a signal detection circuit and outputs a BD signal 117.

This BD signal detection circuit 115 is provided in the scanner unit.

[Problem that the invention is trying to solve]

However, the conventional example shown in FIG. 8 has the following drawbacks.

FIG. 9 shows a state in which laser light passes through the light receiving section.

Reference numeral 120 represents a laser beam, and an arrow 1 points on the light receiving surface 122.
The light-receiving surface 122 is a photoelectric conversion element such as a photodiode, and when the laser beam passes over the light-receiving surface, a photocurrent shown as line 123 in FIG. 10 is generated. A line 125 shows the level when no light is shining on it, and a broken line 124 shows the level when it is judged that light is shining on it and outputs a D signal like 126.

Next, when the laser beam 127 passes through the position indicated by the arrow 128 as shown in FIG. Only a photocurrent is generated. Here, 132 indicates the level when no light is applied, and the broken line 131 indicates the slice level. Since the photocurrent 130 exceeds the slice level 131, the BD signal output is output as 133. Photocurrent 1
Looking at the relationship between 30 and the slice level 131, the photocurrent passes through the slice level almost immediately before reaching its peak.

In other words, since the slope of the rising waveform of the photocurrent is small,
It is easily affected by changes in slice level and light intensity. This effect acts in the direction of speeding up or slowing down the rise time of the BD double signal (therefore, it appears in the image as fluctuation (jitter) in the main scanning direction.In the worst case, due to environmental changes, etc., the photocurrent There is a drawback that a situation occurs in which the output level of the BD signal 133 changes and does not reach the slice level 131, and the BD signal 133 is not output.

Even if you try to make adjustments while measuring the analog level using a dedicated adjustment device like when using optical fiber, the light receiving section and its peripheral circuits are configured within the scanner unit, so only the peripheral circuits can be adjusted as described above. It cannot be replaced with a dedicated device.

Therefore, since the BD signal detection circuit 115 does not output a BD multiplied signal which is a digital signal,
Adjustments must be made while monitoring this BD double signal,
It is not possible to make adjustments that take sufficient margin into account.

[Means and effects for solving the problem] Therefore, according to the present invention, when the light-receiving element and its peripheral circuit are configured on one substrate or integrated as an IC (integrated circuit), binary In addition to the converted ED signal output, it also provides an analog output that can monitor the amount of incident light, or a digital output that uses a slice level different from the slice level of the light that can monitor that the amount of light that is incident is sufficient for the slice level. By providing an output, a beam detection device for an image forming apparatus that is resistant to environmental changes and can be easily optically adjusted is realized.

[First example] FIG. 1 shows a first embodiment of the invention.

In this embodiment, an example in which the present invention is applied to a BD detection IC (integrated circuit) will be described. Note that the overall configuration of the laser beam printer using the BD detection IC of this embodiment can be applied to any of the prior art configurations explained in FIGS. Explanation will be omitted. In FIG. 1, 1 is a BD detection IC, 2 is a photodiode which is a photoelectric conversion element, 3 is a BD multiplied signal 4 is a photocurrent monitor signal, 5 is a voltage follower, 6 is a hysteresis comparator, 7 and 8 are hysteresis comparators 9 is a current mirror 10 is a slice level setting terminal, 11 is a power supply terminal, 12 is a ground terminal, 13 is a slice level setting resistor, 14 is a reverse bias for photodiode 2 It is a resistance for

Next, the operation of each part will be explained.

When the photodiode 2 reverse-biased by the resistor 14 is irradiated with light, a photocurrent is generated and the current mirror 9
supplied to. A current proportional to the emitter size of the transistor constituting the current mirror 9 flows from the resistor 13 to the current mirror via the terminal 10. At this time, a voltage drop corresponding to the current occurs across the resistor 13, and a voltage obtained by subtracting the voltage drop from the power supply voltage is generated at the terminal 10. This voltage is determined in part by the hysteresis comparator 6.
1 to the inverted input. The other one is given to voltage follower 5. The voltage applied to the voltage follower 5 is directly output to the photocurrent monitor signal terminal 4. Further, the voltage applied to the hysteresis comparator 6 is compared with a reference voltage created by a resistor 7.8, and a BD multiplied signal is outputted to the output 3 according to the comparison result.

At the time of adjustment, the adjustment is made while monitoring the photocurrent monitor signal 4 and confirming that slicing is not performed with no margin.

That is, when the photocurrent monitor signal 4 is monitored as shown by line 130 in FIG. 4, the laser beam is scanning the end of the light receiving surface of the photoelectric conversion element 2. And BD detection I
The fixed position of C is adjusted so that the photocurrent monitor signal 4 is as shown by line 123 in FIG. Thereby, the position of the BD detection IC can be adjusted so that the laser beam scans the center of the light receiving surface of the photoelectric conversion element 2 without using a special jig.

The output range of this photocurrent monitor signal 4 does not necessarily have to be able to monitor the photocurrent from 0% to 100% (it must at least have a range that can monitor the necessary margin for the slice level). Also, current mirror 9, voltage follower 5
, and the hysteresis comparator 6 are one means for realizing the functions of the present invention, and the present invention is not limited by the contents of these individual circuit configurations.

[Example 2] Next, a second example of the present invention will be described. In this embodiment, the margin for the slice level is not monitored in an analog manner, but can be monitored digitally.

The second figure is a circuit diagram showing the configuration of the BD detection IC of the second embodiment. In the figure, 2 is a photodiode which is a photoelectric conversion element, 3 is a BD signal output terminal, 6.26 is a hysteresis comparator, 9 is a current mirror, and 10
is a slice level setting terminal, 11 is a power supply terminal, 12 is a ground terminal, 13 is a resistor for slice level setting, 14 is a resistor for applying reverse bias to the photodiode 2, 23, 24, 25 is a comparator 26.6 A resistor 22 for providing a reference voltage for comparison is an output terminal for outputting a detection signal based on a second slice level in order to allow for a margin with respect to the slice level for BD detection.

Next, the operation of these circuits will be explained. The photocurrent generated in the photodiode 2 is amplified by the current mirror 9, and the voltage given by the voltage drop generated by the resistor 13 is amplified by the resistor 23.24 by two comparators 6.26.
．． 25 is compared with a two-level reference voltage created by .

FIG. 3 shows an example of the waveform.

123 is a photocurrent flowing in proportion to the amount of incident light, 124 is a slice level, and 126 is a BD multiplied signal that is compared with the slice level 124 and output. Slice level 15 is a level compared by comparator 26 and is a slice level for recognizing whether there is a sufficient margin with respect to slice level 124 for BD signal generation.

Next, a case where there is no margin in the amount of incident light will be explained.

FIG. 4 shows each signal when the amount of incident light is about the slice level. 130 is photocurrent and 131 is BD
This is the slice level for signal generation. Since the photocurrent 130 exceeds the slice level 131, the BD signal 13
3 is output. However, since there is no margin, there is a possibility that the output will not be output due to environmental changes. In order to determine such a state, the slice level 17 of the comparator 26 is
are compared and an output 18 is output. Looking at this output, there is no output because slice level 17 has not been reached. Therefore, by looking at this output, it can be seen that there is no margin.

This output terminal 22 can be directly measured using a measuring device, but the output terminal 22 is connected to a controller 32 that controls image formation.
But it can be done. An example is shown in FIG.

The BD signal detection circuit 21 is the same as that explained in FIG. 2, and outputs an adjustment signal from the terminal 3 and the ED double signal terminal 22. These BD multiplication signals and adjustment signals are transferred to the controller 32 via lines 29 and 30, respectively. 27 is a selector for selecting one of the BD double signal adjustment signals. 28 is a select signal for the selector 27, and 31 is a control section. The control unit 31 originally has a function of determining the presence or absence of a BD double signal. Therefore, during adjustment, the select signal 28 is operated so that the selector 27 selects the adjustment signal. This allows adjustment to be made without the use of special jigs or measuring instruments.

In the above description, the case where the ED detection circuit is implemented as an IC has been explained as an example, but the same applies to the case where it is implemented using discrete components. Further, there may be a plurality of digital outputs of the adjustment signal, or they may be mixed with the analog output of the first embodiment.

〔Effect of the invention〕

As explained above, by using the present invention, it is possible to realize an inexpensive D detection section that does not use an optical fiber and without being susceptible to environmental changes.

Furthermore, there is an effect that the optical adjustment of the BD detection section is also facilitated.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing the configuration of a BD detection IC according to a first embodiment of the present invention. FIG. 2 is a circuit diagram showing the configuration of a BD detection IC according to a second embodiment of the present invention. The figure shows each signal when the laser beam scans the center of the light-receiving surface of the photoelectric conversion element, and Figure 4 shows each signal when the laser beam scans the edge of the light-receiving surface of the photoelectric conversion element. FIG. 5 is a diagram representing B of the second embodiment of the present invention.
A diagram showing an example of a configuration when performing adjustment using a D detection IC,
FIG. 6 is a perspective view showing an example of a simplified configuration of a laser beam printer, FIG. 7 is a perspective view showing an example of a simplified configuration of another laser beam printer, and FIG. 8 is a perspective view showing an example of a simplified configuration of another laser beam printer. A perspective view, FIG. 9 is a diagram showing that the central part of the light-receiving surface of the photoelectric conversion element is scanned with a laser beam, FIG. 10 is a diagram showing each signal in the BD detection IC in the case of FIG. 9, FIG. 11 is a diagram showing that the edge of the light-receiving surface of the photoelectric conversion element is scanned with a laser beam, and FIG. 12 is a diagram showing each signal in the BD detection IC in the case of FIG. 11. 1.21...RC for ED detection 2...Photoelectric conversion element (photodiode) 3...B
D times signal...Photocurrent monitor signal 5...Voltage follower 6.26...Hysteresis comparator pnzz

Claims (3)

[Claims] (1) In a beam detection device of an image forming apparatus that scans a photoreceptor with a laser beam modulated based on an image signal to form an image, the beam detection device includes a photoelectric conversion element that receives the laser beam and generates a horizontal synchronization signal. In order to do this, a first comparison means for comparing the output of the photoelectric conversion element with a first threshold value, and a second comparison means for comparing the output of the photoelectric conversion element with a second threshold value different from the first threshold value. A beam detection device for an image forming apparatus, comprising: (2) In a beam detection device of an image forming apparatus that forms an image by scanning a photoreceptor with a laser beam modulated based on an image signal, a photoelectric conversion element that receives the laser beam and generates a horizontal synchronization signal. A beam of an image forming apparatus characterized in that the image forming apparatus comprises: a comparison means for comparing the output of the photoelectric conversion element with a predetermined threshold; and an output means for outputting a level signal according to the output of the photoelectric conversion element. Detection device. (3) A beam detection circuit for generating a horizontal synchronizing signal for a laser beam printer that scans a laser beam modulated by an image signal onto a photoreceptor to form an image, the beam detection circuit having a first intensity slice level; a first output means for outputting a digital signal that becomes effective when a beam having an intensity equal to or higher than a first intensity slice level is irradiated onto the light receiving section; and a level proportional to the intensity of the beam irradiated onto the light receiving section. a second output means for outputting an analog signal;
and third output means for outputting a digital signal that becomes effective when a beam having an intensity equal to or higher than the second slice level is irradiated. Beam detection device for laser beam printers.