JP4283390B2 - Beam light detector - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a beam light detection apparatus for detecting a scanning position and intensity of a beam light.
[0002]
[Prior art]
In an image forming apparatus such as a digital copying machine, an image bearing member is exposed and scanned with a laser beam to form an electrostatic latent image on the image bearing member, but the scanning position and intensity of the beam light are in an appropriate state. A light sensor is provided for the scanning path of the light beam, and the scanning position and intensity of the light beam are detected by performing signal processing such as amplification on the output of the light sensor, and the scanning position and intensity of the light beam are detected according to the detection result. To adjust.
[0003]
However, there is a problem that an offset value when the output of the optical sensor is signal-processed appears as a detection error.
[0004]
In order to eliminate such a detection error, conventionally, a signal processing output such as amplification (including an offset value) in a state where the beam light does not correspond to the optical sensor (including an offset value) is previously captured and stored in the control unit, Based on the stored contents, the actual detection result is corrected and calculated. In order to create a state in which the light beam does not correspond to the optical sensor, in the example of Japanese Patent Laid-Open No. 10-142535, the mirror is moved to shift the light beam from the original scanning position.
[0005]
[Problems to be solved by the invention]
As described above, if the control unit performs the correction calculation, a program for the correction calculation must be prepared.
[0006]
In order to shift the beam light from the original scanning position by moving the mirror, a program for the shift control is required, and a new optical sensor for confirming whether the beam light has been reliably shifted to the predetermined position is provided. It becomes necessary.
[0007]
The present invention takes the above circumstances into consideration, and the object of the present invention is to eliminate the detection error due to the offset value without requiring correction calculation in the control unit and without shifting the beam light from the original scanning position. It is an object of the present invention to provide a beam light detection apparatus with excellent reliability that can eliminate the problem and always accurately detect the scanning position or intensity of the beam light.
[0008]
[Means for Solving the Problems]
According to a first aspect of the present invention, there is provided a beam light detection apparatus including first and second optical sensors disposed across a path of the beam light in a direction perpendicular to the scanning direction of the beam light, and currents of these light sensors. First and second current / voltage conversion circuits for converting outputs to voltages, respectively, and differential amplification for amplifying the difference between the output voltage of the first current / voltage conversion circuit and the output voltage of the second current / voltage conversion circuit A circuit, an integration circuit for integrating the output of the differential amplifier circuit, a reset means for resetting the integration circuit before the scanning of the light beam reaches the corresponding position with each optical sensor, and at the time of reset by the reset means The connection between the differential amplifier circuit and the integration circuit is cut off once, and the offset value by each of the current-voltage conversion circuit and the differential amplifier circuit is detected during the cut-off. And a correction means in accordance with the Tsu preparative values allowed to correct the output of the differential amplifier circuit, a signal representative of the output scanning position of the light beam of the integrator circuit.
[0009]
According to a second aspect of the present invention, there is provided the beam light detecting apparatus according to the first aspect, wherein the reset means is sequentially disposed on the near side of the light beam scanning path from the positions where the first and second photosensors are disposed. The third and fourth photosensors are provided, and a reset signal for the integrating circuit is generated from when the third photosensor detects the beam light until the fourth photosensor detects the beam light.
[0010]
According to a third aspect of the present invention, there is provided the beam light detection device according to the first aspect, wherein the correction means detects the difference between the output voltage of the differential amplifier circuit at the time of reset and the reference voltage as an offset value, and cancels the reset. Thereafter, the detected offset value is held as correction data for the differential amplifier circuit.
[0011]
According to a fourth aspect of the present invention, in the invention according to the third aspect, the differential amplifier circuit controls the offset output of the differential amplifier circuit in accordance with the correction data held in the correction means. To do.
[0012]
According to a fifth aspect of the present invention, there is provided a light beam detection apparatus comprising: a light sensor provided on a light beam scanning path; a current-voltage conversion circuit that converts a current output of the light sensor into a voltage; A differential amplifier circuit for amplifying the difference between the output voltage and the reference voltage; an integration circuit for integrating the output of the differential amplifier circuit; and the integration before the scanning of the light beam reaches the corresponding position with the optical sensor. A reset means for resetting the circuit, and the connection between the differential amplifier circuit and the integration circuit at the time of reset by the reset means is temporarily cut off, and the offset value by the current-voltage conversion circuit and the differential amplifier circuit is set during the cutoff. And a correction means for correcting the output of the differential amplifier circuit in accordance with the detected offset value after reset is released, and the output of the integration circuit is a signal representing the intensity of the beam light. To.
[0013]
According to a sixth aspect of the present invention, there is provided the beam light detecting device according to the fifth aspect of the present invention, wherein the reset means is arranged first and second sequentially on the front side of the position of the optical sensor in the beam light scanning path. An optical sensor is provided, and a reset signal is issued to the integrating circuit from when the first optical sensor detects the beam light until the second optical sensor detects the beam light.
[0014]
According to a seventh aspect of the present invention, in the invention according to the fifth aspect, the correction means detects the difference between the output voltage of the differential amplifier circuit at the time of reset and the reference voltage as an offset value, and cancels the reset. Thereafter, the detected offset value is held as correction data for the differential amplifier circuit.
[0015]
According to an eighth aspect of the present invention, there is provided the beam light detection device according to the seventh aspect, wherein the differential amplifier circuit controls the offset output of the differential amplifier circuit according to the correction data held in the correction means. To do.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
First, a configuration related to detection of the scanning position of the light beam is shown in FIG. Optical sensors 1, 2, and 3 are sequentially arranged at predetermined intervals along the scanning direction of beam lights B1 and B2 emitted from a laser unit 34 described later. Optical sensors S1 and S2 are disposed between the optical sensor 2 and the optical sensor 3 so as to sandwich the path of the beam light B1 in a direction perpendicular to the scanning direction of the beam light B1. Further, an optical sensor S3 is provided in addition to the optical sensor S2 so as to sandwich the path of the light beam B2 in a direction perpendicular to the scanning direction of the light beam B2.
[0017]
The optical sensors S1 and S2 are prepared for detecting a shift in the scanning position of the beam light B1. The optical sensor S3 is prepared together with the optical sensor S2 to detect a shift in the scanning position of the light beam B2.
[0018]
The optical sensors 1 and 2 are arranged in front of the arrangement positions of the optical sensors S1, S2 and S3 in the scanning paths of the beam lights B1 and B2, and are used as components of the reset signal generation circuit 11 described later. Function.
[0019]
The optical sensor 3 detects that the scanning of the light beams B1 and B2 has passed through the optical sensors S1, S2, and S3. With this detection, the offset value detection related to position detection is completed.
[0020]
FIG. 2 shows a configuration related to the detection of the intensity of the light beam. On the scanning path of the light beams B1 and B2, the optical sensor 4, the optical sensor 5, and the optical sensor 6 are sequentially arranged at predetermined intervals. Similarly, an optical sensor S4 is disposed on the scanning path between the optical sensor 5 and the optical sensor 6.
[0021]
The optical sensor S4 is prepared for detecting the intensity of each of the light beams B1 and B2.
[0022]
The optical sensors 4 and 5 are arranged in front of the arrangement position of the optical sensor S4 in the scanning path of the beam lights B1 and B2, and function as components of a reset signal generation circuit 21 described later.
[0023]
The optical sensor 6 detects that the scanning of the light beams B1 and B2 has passed through the optical sensor S4. With this detection, the offset value detection related to the intensity detection is completed.
[0024]
The number of light beams is not limited to two of B1 and B2, but may be three or more. Each time the light beam increases, the number of optical sensors increases by one in the arrangement direction of the optical sensors S1, S2, and S3.
[0025]
On the other hand, as shown in FIG. 3, the optical sensors 1, 2, 3, S 1, S 2, S 3 are connected to the light beam position detector 10, and the detection signal of the light beam position detector 10 is supplied to the controller 30. The Further, the optical sensors 4, 5, 6, S 4 are connected to the beam light intensity detection unit 20, and the detection signal of the beam light intensity detection unit 20 is supplied to the control unit 30.
[0026]
A laser unit 34 is connected to the control unit 30 through a laser drive unit 31, and a polygon mirror 35 and a galvano mirror 36 are connected through mirror drive units 32 and 33, respectively. The polygon mirror 35 is for scanning the light beams B1 and B2. The galvanometer mirror 36 is for moving the beam lights B1 and B2 in a direction perpendicular to the scanning direction.
[0027]
The control unit 30 controls the galvanometer mirror 36 so that the scanning positions of the light beams B1 and B2 are in an appropriate state based on the detection signal from the light beam position detection unit 10, and the detection by the light beam intensity detection unit 20. And control means for controlling the output of the laser unit 34 based on the signal so that the intensities of the light beams B1 and B2 are in an appropriate state.
[0028]
[1] The light beam position detector 10 will be described below.
The light beam position detection unit 10 includes a reset signal generation circuit (reset means) 11 and offset correction circuits 12 and 13.
[0029]
As shown in FIG. 1, the reset signal generation circuit 11 is between the optical sensor 1 detecting the beam light B1 (B2) and the optical sensor 2 detecting the beam light B1 (B2), that is, the beam. Before the scanning of the light B1 (B2) reaches the corresponding position with the optical sensors S1 and S2, a reset signal (logic “1”) X is issued to the integration circuit 60 described later.
[0030]
A specific configuration of the light beam position detector 10 including the offset correction circuits 12 and 13 is shown in FIG.
The optical sensor S1 is a photodiode, and a current of a level corresponding to the distance from the light beam B1 flows when the light beam B1 is scanned.
[0031]
The optical sensor S2 is a photodiode, and a current of a level corresponding to the distance to the beam light B1 flows when the beam light B1 is scanned, and a level corresponding to the distance to the beam light B2 is scanned when the beam light B2 is scanned. Current flows.
[0032]
The optical sensor S3 is a photodiode, and a current of a level corresponding to the distance from the light beam B2 flows when the light beam B2 is scanned.
[0033]
First, at the time of scanning with the light beam B1, the current outputs of the optical sensors S1 and S2 are converted into voltages by the current-voltage conversion circuits (first and second current-voltage conversion circuits) 40a and 40b, respectively, to the differential amplifier circuit 50a. Entered. The current-voltage conversion circuits 40a and 40b are composed of an operational amplifier 41, a feedback capacitor 42, and a feedback resistor 43, and convert the output currents of the optical sensors S1 and S2 into voltages based on the reference voltage V, respectively.
[0034]
The differential amplifier circuit 50a includes an operational amplifier 51, input resistors 52 and 53, a reference voltage input resistor 54, and a feedback resistor 55, and the output voltages of the current-voltage conversion circuits 40a and 40b based on the current outputs of the optical sensors S1 and S2. Amplify the difference. The output of the differential amplifier circuit 50a is supplied to the integrating circuit 60 via the switch 70 of the offset correction circuit 12.
[0035]
At the time of scanning with the light beam B2, the current outputs of the optical sensors S2 and S3 are converted into voltages by current-voltage conversion circuits (first and second current-voltage conversion circuits) 40b and 40c, respectively, and input to the differential amplifier circuit 50b. The The current-voltage conversion circuit 40b includes an operational amplifier 41, a feedback capacitor 42, and a feedback resistor 43, and converts the output current of the optical sensor S3 into a voltage with reference to the reference voltage V.
[0036]
The differential amplifier circuit 50b amplifies the difference between the output voltages of the current-voltage conversion circuits 40b and 40c based on the current outputs of the optical sensors S2 and S3. The output of the differential amplifier circuit 50b is supplied to the integrating circuit 60 via the switch 80 of the offset correction circuit 13.
[0037]
The integration circuit 60 includes an operational amplifier 61, a feedback capacitor 62, a feedback resistor 63, and a reset switch 64. When the reset signal X of the reset signal generation circuit 11 is logic "0", the integration operation is performed by opening the reset switch 64. . At this time, if the switch 70 of the offset correction circuit 12 is closed, the output of the differential amplifier circuit 50a is integrated, and the integrated output is supplied to the control unit 30 as a signal (detection signal) indicating the scanning position of the light beam B1. Is done. If the switch 80 of the offset correction circuit 13 is closed, the output of the differential amplifier circuit 50b is integrated, and the integrated output is supplied to the control unit 30 as a signal (detection signal) indicating the scanning position of the beam light B2. When the reset signal X becomes logic “1”, the reset switch 64 is closed, a discharge circuit for the capacitor 62 is formed, and the integration circuit 60 is reset (initialized).
[0038]
The offset correction circuit 12 includes a switch (op-amp) 71 that outputs a voltage corresponding to the difference between the output voltage of the switch 70 and the differential amplifier circuit 50a and the reference voltage V, an output of the switch 72, and the comparator 71. And an inverter circuit 74 that inverts the reset signal X, and an AND circuit 75 that effectively outputs the output of the inverter circuit 74 when the select signal Y1 from the control unit 30 is logic "1". . The switch 70 opens when the reset signal X is logic “1” and closes when the reset signal X is logic “0”. The select signal Y1 becomes logic “1” when the beam light B1 is scanned, and is supplied from the control unit 30.
[0039]
In short, the offset correction circuit 12 detects the difference between the output voltage of the differential amplifier circuit 50a and the reference voltage V as an offset value by the comparator 71 when the integration circuit 60 is reset (the switch 70 is open and the switch 72 is closed). Then, after the reset of the integrating circuit 60 is released (the switch 70 is closed and the switch 72 is opened), the detected offset value is held in the capacitor 73 as correction data for the differential amplifier circuit 50a.
[0040]
The operational amplifier 51 of the differential amplifier circuit 50 a has a function of controlling the offset output in accordance with the correction data held in the capacitor 73.
[0041]
The offset correction circuit 13 includes a switch (op-amp) 81 that outputs a voltage at a level corresponding to the difference between the output voltage of the switch 80 and the differential amplifier circuit 50b and the reference voltage V, an output of the switch 82, and the output of the comparator 81. A capacitor 83 applied via 82, an inverter circuit 84 for inverting the reset signal X, and an AND circuit 85 for effectively outputting the output of the inverter circuit 84 when the select signal Y2 from the control unit 30 is logic "1". . The switch 80 opens when the reset signal X is logic “1” and closes when the reset signal X is logic “0”. The select signal Y2 becomes a logic “1” when the beam light B2 is scanned, and is supplied from the control unit 30.
[0042]
That is, the offset correction circuit 13 detects the difference between the output voltage of the differential amplifier circuit 50b and the reference voltage V as an offset value by the comparator 81 when the integration circuit 60 is reset (the switch 80 is open and the switch 82 is closed). After the reset of the integrating circuit 60 is released (the switch 80 is closed and the switch 82 is opened), the detected offset value is held in the capacitor 83 as correction data for the differential amplifier circuit 50b.
[0043]
The operational amplifier 51 of the differential amplifier circuit 50 b has a function of controlling the offset output according to the correction data held in the capacitor 83.
[0044]
The operation will be described.
When the beam light B1 is scanned (select signal Y1 is logic “1”), the reset signal X becomes logic “1” at the timing when the beam light B1 passes through the optical sensor S1. At this time, the reset switch 64 is closed and the output of the integrating circuit 60 is initialized to the level of the reference voltage V. At the same time, the switch 70 is opened and the connection between the differential amplifier circuit 50a and the integrating circuit 60 is cut off.
[0045]
At this time, the beam light B1 has not yet reached the corresponding position with the optical sensors S1 and S2, and therefore only the offset value is amplified in the differential amplifier circuit 50a, and the output voltage and the reference voltage of the differential amplifier circuit 50a are amplified. The difference from V is detected by the comparator 71 as an offset value. At this time, since the switch 72 is closed, the offset value detected by the comparator 71 is held in the capacitor 73 as correction data for the differential amplifier circuit 50b.
[0046]
When the light beam B1 passes through the optical sensor S2, the reset signal X becomes logic “0”, the switch 70 is closed, the output of the differential amplifier circuit 50b is supplied to the integrating circuit 60, and the integrating circuit 60 is reset by the reset switch 64. Is opened to integrate the output of the differential amplifier circuit 50b.
[0047]
At the same time, the switch 72 is opened, and the offset output of the differential amplifier circuit 50 a is controlled based on the correction data held in the capacitor 73. Thereby, the offset value is eliminated.
[0048]
When the light beam B1 passes between the optical sensor S1 and the optical sensor S2, the output voltage of the differential amplifier circuit 50a is at the same level as the reference voltage V if the passing position is exactly in the middle of each optical sensor. Accordingly, the output voltage of the integrating circuit 60 becomes the same as the level of the reference voltage V. In this case, the control unit 30 does not control the galvanometer mirror 36 under the determination that the scanning position of the light beam B1 is appropriate in the direction orthogonal to the scanning direction. The offset value of the operational amplifier 61 itself of the integrating circuit 60 is neglected here because it is sufficiently smaller than the offset error amplified by the differential amplifier circuit 50a.
[0049]
If the passing position of the light beam B1 is set to one of the centers of the optical sensors, the output voltage of the integrating circuit 60 is in a state higher (or lower) than the level of the reference voltage V. In this case, the control unit 30 moves the galvanometer mirror 36 so that the output voltage of the integrating circuit 60 becomes the level of the reference voltage V, that is, the scanning position of the light beam B1 is in an appropriate state in the direction perpendicular to the scanning direction. Control.
[0050]
As described above, when the integration circuit 60 is reset, the offset value is detected, and the differential amplifier circuit 50a is controlled in such a direction that the detected offset value is eliminated. The state has already been eliminated, so that the scanning position of the light beam can always be accurately detected, and the reliability can be improved.
[0051]
The output of the integration circuit 60 when the offset correction circuit 12 has the correction function and the output of the integration circuit 60 when the offset correction circuit 12 does not have the correction function are shown in FIG. Since the offset correction circuit 12 has a correction function, it is possible to perform appropriate detection without error.
[0052]
In particular, it is not necessary to perform a correction calculation in the control unit 30 as in the prior art, and thus a program for the correction calculation is not required, thereby reducing the cost. Further, it is not necessary to shift the light beam from the original scanning position as in the conventional example, and the control can be simplified in this respect.
The same detection is performed when scanning the light beam B2.
[0053]
[2] Next, the light beam intensity detector 20 will be described.
The beam light intensity detector 20 includes a reset signal generation circuit (reset means) 21 and an offset correction circuit 22.
[0054]
As shown in FIG. 2, the reset signal generation circuit 21 is between the optical sensor 4 detecting the beam light B1 (B2) and the optical sensor 5 detecting the beam light B1 (B2), that is, the beam. Before the scanning of the light B1 (B2) reaches the position corresponding to the optical sensor S4, a reset signal (logic “1”) Z is issued to the integration circuit 110 described later.
[0055]
A specific configuration of the beam light intensity detector 20 including the offset correction circuit 22 is shown in FIG.
The optical sensor S4 is a photodiode, and a current of a level corresponding to the intensity of the light beam B1 (B2) flows while the light beam B1 (B2) is hit.
[0056]
The current output of the optical sensor S4 is converted into a voltage by the current-voltage conversion circuit 90 and input to the differential amplifier circuit 100. The current-voltage conversion circuit 90 includes an operational amplifier 91, a feedback capacitor 92, and a feedback resistor 93, and converts the output current of the optical sensor S4 into a voltage using the reference voltage V as a reference.
[0057]
The differential amplifier circuit 100 includes an operational amplifier 101, an input resistor 102, a reference voltage input resistor 103, and a feedback resistor 104, and calculates a difference between the output voltage of the current-voltage conversion circuit 90 based on the current output of the optical sensor S4 and the reference voltage V. Amplify. The output of the differential amplifier circuit 100 is supplied to the integrating circuit 110 via the switch 120 of the offset correction circuit 22.
[0058]
The integration circuit 110 includes an operational amplifier 111, a feedback capacitor 112, a feedback resistor 113, and a reset switch 114. When the reset signal Z of the reset signal generation circuit 1 is logic "0", the integration operation is performed by opening the reset switch 114. . At this time, if the switch 120 of the offset correction circuit 22 is closed, the output of the differential amplifier circuit 100 is integrated, and the integrated output is a signal (detection signal) representing the intensity of the beam light B1 (B2). To be supplied. When the reset signal Z becomes logic “1”, the reset switch 114 is closed, a discharge circuit for the capacitor 112 is formed, and the integration circuit 110 is reset (initialized).
[0059]
The offset correction circuit 22 includes a switch 120, a comparator (op-amp) 121 that outputs a voltage corresponding to the difference between the output voltage of the differential amplifier circuit 100 and the reference voltage V, an output of the switch 122, and the comparator 121. A capacitor 123 applied via 122 and an inverter circuit 124 for inverting the reset signal Z are provided. The switch 120 opens when the reset signal Z is logic “1”, and closes when the reset signal Z is logic “0”.
[0060]
In short, the offset correction circuit 22 detects the difference between the output voltage of the differential amplifier circuit 100 and the reference voltage V as an offset value when the integration circuit 110 is reset (the switch 120 is open and the switch 122 is closed). After the reset of the integrating circuit 110 is released (the switch 120 is closed and the switch 122 is opened), the detected offset value is held in the capacitor 123 as correction data for the differential amplifier circuit 100.
[0061]
The operational amplifier 51 of the differential amplifier circuit 100 has a function of controlling the offset output in accordance with the correction data held in the capacitor 73.
[0062]
The operation will be described.
During the scanning of the light beam B1, the reset signal Z becomes logic “1” at the timing when the light beam B1 passes through the optical sensor S4. At this time, the reset switch 114 is closed and the output of the integrating circuit 110 is initialized to the level of the reference voltage V. At the same time, the switch 120 is opened and the connection between the differential amplifier circuit 100 and the integrating circuit 110 is cut off.
[0063]
At this time, the light beam B1 has not yet reached the optical sensor S4, so that only the offset value is amplified in the differential amplifier circuit 100, and the difference between the output voltage of the differential amplifier circuit 100 and the reference voltage V is compared. It is detected as an offset value by the device 121. At this time, since the switch 122 is closed, the offset value detected by the comparator 121 is held in the capacitor 123 as correction data for the differential amplifier circuit 100.
[0064]
When the light beam B1 passes through the optical sensor S5, the reset signal Z becomes logic “0”, the switch 120 is closed, the output of the differential amplifier circuit 100 is supplied to the integrating circuit 110, and the integrating circuit 110 is reset by the reset switch 114. Is opened to integrate the output of the differential amplifier circuit 100.
[0065]
At the same time, the switch 122 is opened, and the offset output of the differential amplifier circuit 100 is controlled based on the correction data held in the capacitor 123. Thereby, the offset value is eliminated.
[0066]
While the light beam B1 strikes the optical sensor S4, a voltage having a level corresponding to the intensity of the light beam B1 is output from the differential amplifier circuit 100 and integrated by the integrating circuit 110. If the time during which the light beam B1 strikes the optical sensor S4 is always constant, the level of the output voltage of the integrating circuit 110 increases as the intensity of the light beam B1 increases. The intensity of the beam light B1 can be detected from this voltage level. The control unit 30 controls the output of the laser unit 34 so that the detected intensity becomes a constant set value. Note that the offset value of the operational amplifier 111 itself of the integrating circuit 110 is neglected here because it is sufficiently smaller than the offset error amplified by the differential amplifier circuit 90.
[0067]
As described above, when the integration circuit 110 is reset, the offset value is detected, and the differential amplifier circuit 100 is controlled in such a direction that the detected offset value is eliminated, so that the signal input to the integration circuit 110 has an offset value. This has already been solved, so that the intensity of the light beam can always be accurately detected, and the reliability can be improved.
[0068]
In particular, it is not necessary to perform a correction calculation in the control unit 30 as in the prior art, and thus a program for the correction calculation is not required, thereby reducing the cost. Further, it is not necessary to shift the light beam from the original scanning position as in the conventional example, and the control can be simplified in this respect.
The same detection is performed when scanning the light beam B2.
[0069]
In the above embodiment, application to a digital copying machine has been described. However, as long as a laser beam is used, the present invention can be similarly applied to other devices.
In addition, the present invention is not limited to the above embodiment, and various modifications can be made without departing from the scope of the invention.
[0070]
【The invention's effect】
As described above, according to the present invention, the offset value is detected at the time of resetting the integrating circuit, the differential amplifier circuit is controlled in a direction in which the detected offset value is canceled, and the signal in the state where the offset value has already been canceled. Is provided to the integration circuit, so that the detection error due to the offset value is eliminated without requiring correction calculation in the control unit and without shifting the beam light from the original scanning position. Alternatively, it is possible to provide a highly reliable beam light detection apparatus that can always accurately detect the intensity.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating an example of a signal waveform based on an arrangement of optical sensors related to beam light position detection and detection of the optical sensor according to one embodiment.
FIG. 2 is a view showing an example of a signal waveform based on an arrangement of optical sensors related to detection of light intensity of an embodiment and detection of the optical sensor.
FIG. 3 is a block diagram illustrating a configuration of a control circuit according to an embodiment.
FIG. 4 is a block diagram showing a specific configuration of a light beam position detection unit according to an embodiment.
FIG. 5 is a block diagram illustrating a specific configuration of a beam light intensity detection unit according to an embodiment.
[Explanation of symbols]
1, 2, 3 ... Optical sensor
S1, S2, S3, S4 ... Optical sensor
B1, B2 ... Beam light
10: Beam light position detector
11 ... Reset signal generation circuit
12, 13 ... Offset correction circuit
20: Beam light intensity detector
21 ... Reset signal generation circuit
22 ... Offset correction circuit
30 ... Control unit
40a, 40b, 40c, 90 ... current-voltage conversion circuit
50a, 50b, 100 ... differential amplifier circuit
60, 110 ... integration circuit

Claims (8)

First and second optical sensors disposed across the path of the light beam in a direction perpendicular to the scanning direction of the light beam;
First and second current-voltage conversion circuits for converting the current outputs of these photosensors into voltages, respectively;
A differential amplifier circuit for amplifying a difference between an output voltage of the first current-voltage converter circuit and an output voltage of the second current-voltage converter circuit;
An integration circuit for integrating the output of the differential amplifier circuit;
Resetting means for resetting the integrating circuit before the scanning of the light beam reaches the corresponding position with each optical sensor;
During the reset by the reset means, the connection between the differential amplifier circuit and the integration circuit is temporarily interrupted, and during the disconnection, the offset value by each of the current-voltage conversion circuit and the differential amplifier circuit is detected, and after reset release, Correction means for correcting the output of the differential amplifier circuit according to the detected offset value,
A beam light detection apparatus characterized in that an output of the integration circuit is used as a signal representing a scanning position of the beam light. The reset means includes third and fourth photosensors sequentially arranged on the near side of the first and second photosensors in the beam light scanning path, and the third photosensors The beam light detection apparatus according to claim 1, wherein a reset signal for the integration circuit is issued from when the beam light is detected until the fourth light sensor detects the beam light. The correction means detects a difference between the output voltage of the differential amplifier circuit at reset and a reference voltage as an offset value, and holds the detected offset value as correction data for the differential amplifier circuit after reset is released The light beam detection apparatus according to claim 1. 4. The beam light detection apparatus according to claim 3, wherein the differential amplifier circuit controls an offset output of the differential amplifier circuit in accordance with correction data held in the correction unit. An optical sensor provided on the beam light scanning path;
A current-voltage conversion circuit that converts the current output of the photosensor into a voltage;
A differential amplifier circuit that amplifies the difference between the output voltage of the current-voltage conversion circuit and a reference voltage;
An integration circuit for integrating the output of the differential amplifier circuit;
Reset means for resetting the integration circuit before the scanning of the light beam reaches a corresponding position with the optical sensor;
When resetting by the reset means, the connection between the differential amplifier circuit and the integrating circuit is once cut off, and during the cutoff, the offset value by the current-voltage conversion circuit and the differential amplifier circuit is detected, and after the reset is released, the detection is performed. Correction means for correcting the output of the differential amplifier circuit according to the offset value,
A beam light detection apparatus characterized in that the output of the integration circuit is a signal representing the intensity of beam light. The reset means includes first and second optical sensors sequentially arranged on the front side of the position of the optical sensor in the beam light scanning path, and the first optical sensor detects the beam light. 6. The beam light detection apparatus according to claim 5, wherein a reset signal for the integration circuit is issued until the second optical sensor detects the beam light. The correction means detects a difference between the output voltage of the differential amplifier circuit at reset and a reference voltage as an offset value, and holds the detected offset value as correction data for the differential amplifier circuit after reset is released The light beam detection apparatus according to claim 5. 8. The beam light detection apparatus according to claim 7, wherein the differential amplifier circuit controls an offset output of the differential amplifier circuit according to correction data held in the correction unit.

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