JPH02257114A - Beam light scanner - Google Patents

Abstract

PURPOSE:To surely confirm that beam light scans the light receiving surface of a beam detecting means and to facilitate an adjustment operation by providing a 2nd beam detecting means to detect whether the beam light scans nearly the center of the light receiving surface of the 1st beam detecting means or not and an annunciating means which annunciates the result of this detection. CONSTITUTION:A driving means 16 is inputted with a modulation signal in accordance with the beam detection signal outputted from the 1st beam detecting means 14 and drives a laser oscillator 11 in accordance with the modulation signal thereof, thereby information recording in the prescribed position on a photosensitive body 13 is executed. The 2nd beam detecting means 15 detects whether the laser beam B scans nearly the center of the light receiving surface of the 1st beam detecting means 14 or not. A control means 17 controls the result of the detection thereof so as to annunciate the result by the annunciating means 18. The confirmation that the beam light scans the light receiving surface of the beam detecting means is surely executed in this way without requiring a special beam adjusting mark, measuring instrument, etc. The beam light scanner which facilitates the adjusting operation is thus obtd.

Description

Detailed Description of the Invention [Object of the Invention] (Industrial Application Field) The present invention relates to an image forming apparatus such as a laser printer that prints by scanning exposure using a scanned laser beam and an electrophotographic process, or a scanning The present invention relates to a beam light device suitable for use in an information reading device or the like that reads image information using a laser beam.

(Prior Art) Recently, laser printers have been developed that print by, for example, scanning exposure using a scanned laser beam and an electrophotographic process. This type of laser printer has a laser beam scanning system that mainly consists of a laser oscillator to obtain a laser beam (beam light) and a rotating mirror such as a polygon mirror that scans the laser beam output from the laser oscillator. equipment is used.

Now, such a beam light scanning device is provided with a beam detection means for detecting the position of the laser beam scanned by the rotating mirror, and the beam detection signal from this beam detection means is usually recorded. It is used as a horizontal synchronization signal for writing information signals from a predetermined position on the medium.

Since the beam detection means described above is required to have high-speed response,
Since a PIN diode with a very small light-receiving area is used, and the wavelength of the scanning laser beam is 780 nm, which is not visible light, the scanning laser beam must be visually observed using an infrared viewer, etc., to ensure that it passes through the light-receiving surface of the beam detection means. At the same time, adjustments were made so that the laser beam passed over the beam adjustment mark.

(Problem to be Solved by the Invention) However, in such an adjustment method, in order to confirm that the laser beam has scanned the light receiving surface of the beam detection means,
Special beam alignment marks and measuring instruments such as infrared viewers are required, and further adjustments require time. In addition, especially in a small optical system, the structure makes it difficult to visually observe the laser beam passing through the light receiving surface of the beam detection means, so there is a problem that adjustment is extremely difficult.

Therefore, the present invention does not require a special beam adjustment mark or measuring device, and can reliably detect the beam detection means even in an optical system in which it is difficult to visually observe the beam light passing through the light receiving surface of the beam detection means. It is an object of the present invention to provide a beam light scanning device that allows confirmation that a light beam has scanned a light receiving surface and allows very easy adjustment work.

[Structure J of the Invention (Means for Solving the Problems) The present invention provides a beam light scanning device that scans a surface to be scanned by scanning a beam light outputted from a beam light generating means. a first beam detection means for detecting the position of the light beam, a driving means for driving and controlling the light beam generation means based on a beam detection signal of the first beam detection means; and a drive means for controlling the light beam generation means based on a beam detection signal of the first beam detection means; placed in front or behind the light scanning direction,
A second beam detection means for detecting whether or not the beam light is scanning approximately the center of the light receiving surface of the first beam detection means, and a notification means for notifying the detection result of the second beam detection means. are doing.

(Function) A second beam detector is provided in front or behind the scanning direction of the beam light of the first beam detection means for detecting the position of the scanned beam light.
The beam detection means is arranged, and whether the beam light is scanned by the second beam detection means approximately at the center of the light receiving surface of the first beam detection means, whether it is scanning above or below, or whether it has completely deviated from the light receiving surface. It detects and notifies the detection results. This causes the beam light to
It is possible to easily and reliably confirm whether or not substantially the center of the light receiving surface of the beam detecting means is being scanned.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing an outline of a beam light scanning device according to the present invention. In the figure, reference numeral 11 denotes a laser oscillator as beam light generating means, which uses, for example, a semiconductor laser oscillator, and outputs a modulated laser beam (beam light) B as described later. Reference numeral 12 denotes a multifaceted rotating mirror such as a polygon mirror, which is rotated at high speed by a motor (not shown). The rotating mirror 12 that rotates at high speed reflects the laser beam B output from the laser oscillator 11 and scans the drum-shaped photoreceptor 13 as an image carrier, thereby forming an image on the photoreceptor 13. It looks like this.

Further, the laser beam B scanned by the rotating mirror 12 is detected by the first beam detection means 14 and the second beam detection means 15 in areas other than the recording area of the photoreceptor 3.

The driving means 16 inputs a modulation signal based on the beam detection signal output from the first beam detection means 14, and drives the laser oscillator 11 according to the modulation signal, thereby moving the laser beam to a predetermined position on the photoreceptor 13. It is designed to record information.

The second beam detection means 16 detects whether the laser beam B is scanning approximately the center of the light receiving surface of the second beam detection means 14, and the control means 17 transmits the detection result to the notification means 18. Control is performed to notify the user.

Next, an example in which an embodiment of the present invention is applied to a laser printer will be described.

FIG. 2 shows a schematic configuration of an electrophotographic monochrome laser printer. This laser printer is electrically connected to a host system (external device) such as a computer or word processor via a transmission control device (not shown), and accepts dot image data from the external device to modulate the laser beam. By doing so, writing is performed on the photoreceptor, and the written dot image data is developed and transferred onto paper.

That is, 100 is an apparatus main body, and a drum-shaped photoreceptor 101 is disposed within this main body 100, and this photoreceptor 101 is rotated in the direction of the arrow shown in the figure by a drive source (not shown). Around the photoconductor 101, along the direction of rotation thereof, there are provided a charge control type charger 102, an electrostatic latent image forming section (beam light scanning device) 103, a developer 104 that simultaneously performs development and cleaning, and a charger 102 for charging. Controlled transfer charger 105
are arranged in sequence.

A paper feed cassette l-1, OB is provided at the lower part of the main body 100, and paper P as a recording medium taken out from the paper feed cassette 106 by a paper feed roller 107 is transferred to the photoreceptor 101. A conveyance path 110 is formed that leads to a paper discharge tray 109 provided on the upper surface of the main body 100 via an image transfer section 108 between the image transfer unit 108 and the charger 105 . An aligning roller pair 111 is provided on the upstream side of the image transfer section 108 in the conveyance path 110, and a fixing device (heat roller) is provided on the downstream side.
112 and a pair of paper ejection rollers 113 are provided.

The electrostatic latent image forming unit 103 emits a laser beam B modulated according to dot image data from an external device (not shown).
A semiconductor laser oscillator (laser diode, etc.) that generates 1.14, a lens system 11.5 such as a collimator lens that focuses the laser beam B output from this laser oscillator 114, and a laser that is focused by this lens system 115. For example, a six-sided rotating mirror (polygon mirror) 11B that scans the beam B, a mirror motor 117 that rotates this rotating mirror 116 at high speed, an fθ lens 118 that passes the laser beam B scanned by the rotating mirror 11G, and this f
The laser beam B that has passed through the θ lens 118 is directed to the photoreceptor 10.
Reflection mirrors 09, L20, which reflect the light in the direction of
First beam detection that detects the laser beam B scanned by the correction lens 121 which passes the laser beam B reflected by the anti-J)t mirrors JJ, 9 and 120 and guides it to the surface of the photoreceptor 101, and the rotating mirror 116. vessel 122a, second
It is composed of a beam detector 122b (see FIG. 3) and the like.

In such a configuration, when a print start signal is received from an external device, the photoreceptor 101 rotates and the photoreceptor 1
01 is uniformly charged by the charging device 102 so that the surface potential becomes, for example, about -600 volts.

Next, when receiving dot image data from an external device,
The electrostatic latent image forming unit 103 outputs a laser beam B modulated according to the dot image data, and scans and exposes the charged surface of the photoreceptor 101 with the laser beam B, thereby changing the surface of the photoreceptor 101. forms an electrostatic latent image. The electrostatic latent image formed on the photoreceptor 101 is reversely developed by the developing device 104, thereby being visualized and becomes a toner image. At this time, the developing device 104
Removal (cleaning) of transfer residual toner remaining on 01 is performed at the same time as development.

The toner image on the photoconductor 101 is transferred to an image transfer section 108.
Due to the action of the transfer charger 105, the paper feed cassette 1
The image is transferred onto the paper P conveyed from 06. The paper P on which the toner image has been transferred is conveyed to a fixing device 112, where the toner image is fixed, and then discharged onto a paper discharge tray 109 by a pair of paper discharge rollers 113.

Furthermore, after completing the image formation, the electrostatic latent image forming sections 1 and 03
The static electricity on the photoreceptor 10J is removed by the following steps.

That is, first, the transfer charger 105 is turned off. At this time, since the positive charge from the transfer charger 105 remains between the transfer charger 105 and the charger 102 of the photoreceptor 101, the photoreceptor 101 is uniformly charged with a negative charge by the charger 102. After charging, the charging device 102 is turned off.

Thereafter, the laser oscillator 114 is forced to emit light (no optical modulation is performed), and the rotating mirror II6 is rotated to fully expose the surface of the photoreceptor 101 with the laser beam B scanned by the rotating mirror 116. The photoreceptor 101 is neutralized, and then the rotation of the photoreceptor 101 is stopped to complete the process. These controls are performed by a control section that will be described later.

FIG. 3 shows the installation positions of the first beam detector 122a and the second beam detector 122b. That is, a portion of the laser beam reflected by the reflection mirror 120 is reflected by the beam detection mirror 249 and is then reflected by the first beam detector 12.
2a and the second beam detector 122b, respectively. Note that by adjusting the beam detection mirror 249, the first beam detector 122a and the second
The scanning position of the laser beam B incident on the beam detector 122b can be adjusted.

FIG. 4 shows the laser beam being scanned with the first beam detector 122a and the second beam detector 122b. That is, the second beam detector 122b is arranged in front of the first beam detector 122a in the laser beam scanning direction, and its light receiving surface has a shape similar to that of the second beam photodetector 122b.
is shorter in the direction perpendicular to the laser beam scanning direction. That is, the light receiving surface of the second beam detector 122b is formed in the shape of a narrow slit parallel to the laser beam scanning direction. And the first beam detector 1
22a and the second beam detector 122b are integrally housed within a single outer circumferential case 250.

In FIG. 4, laser beam B. +BIB2 indicates the state of the laser beam being scanned. Laser beam Bo is the normal state of the laser beam that is scanned normally, and laser beam B3 and laser beam B2 are due to maladjustment of the beam detection mirror 249, etc. , shows the state of the laser beam scanned in the upper and lower directions with respect to the laser beam Bo.

FIG. 5 shows the control section of the laser printer configured as described above. This control unit uses a CPU (Central Processing Unit) 201 as the control center, and a ROM (Read Read Memory) in which the system program is stored.
only memory) 202, ROM 203 in which the first data table is stored, RAM (Random Access Memory) 20 used as working memory
4. Rewritable non-volatile RAM 205 storing the second data table, timer 206, input/output port 2
07, print data write control circuit 208, interface control circuit 209 that controls the interface with external devices
It basically has the following.

The timer 206 is a general-purpose timer, and generates basic timing signals for controlling, for example, paper conveyance and processes around the photoreceptor.

The input/output capo 1-207 outputs display data to the operation display unit 210, inputs from various switch data, etc., inputs from various detectors (microswitches, sensors, etc.) 211, and a drive system (including the mirror motor 117). Various motors,
output to the drive circuit 213 that drives the clutch, solenoid, etc.) 212; input/output to the process control circuit 215 that controls the output of the high voltage power supply 214; Input/output to the heater control circuit 218 that inputs the output signal and controls the temperature of the heater lamp 217 of the fixing device 112, and the developing device]
Toner concentration sensor 219 that measures the toner concentration in 04
The output signal is input to and output from a toner concentration control circuit 221 that controls a toner replenishment solenoid 220 that replenishes toner to the developing device 104.

The print data write control circuit 208 includes the laser oscillator 114
Video image data transferred from an external device is sent to a laser drive circuit 232 that drives the laser drive circuit 232 . At this time, the first beam detector 122a detects the laser beam B being scanned by the rotating mirror 116, and the first beam detection circuit 223a generates a horizontal synchronization signal by shaping the output signal of the laser beam B, This is sent to the print data write control circuit 208.

The light amount control circuit 231 transmits the output signal of the monitor diode 230 that detects (monitors) the amount of light of the laser beam B output from the laser oscillator 114 to the first beam detection circuit 22.
The laser drive circuit 2 performs sampling based on the horizontal synchronization signal output from the laser drive circuit 3a.
32, the amount of light of the laser beam B output from the laser oscillator 114 is controlled to be uniform.

The second beam detector 122b is for detecting whether the laser beam B is scanning approximately the center of the light receiving surface of the first beam detector 122a, and its output signal is sent to the second beam detection circuit 223b. The signal is waveform-shaped, then converted into a level output by a timer 270, and input to the input/output port 207.

The ink face control circuit 209 sends the horizontal synchronization signal generated by the first beam detection circuit 223a to an external device, inputs the video image data output from the external device in synchronization with the horizontal synchronization signal, and prints the print data. It is sent to the write control circuit 208. In addition, the interface control circuit 2
09 outputs status data to an external device and also receives command data from the external device.

FIG. 6 shows the first beam detector 122a in FIG.
First beam detection circuit 223a, second beam detector 122
b shows details of the second beam detection circuit 223b.

First, the first beam detector 122a and the first beam detection circuit 223a will be explained. First beam detector 12
2a uses, for example, a PIN diode with very fast response. The beam detection signal from the first beam detector 122a serves as a reference pulse when writing print data onto the photoreceptor 101, and the generation position of this pulse must always be stable.

Now, the anode of the first beam detector 122a is grounded via the load resistor R41,a, and the anode of the first beam detector 122a is connected to the ground via the load resistor R41,a.
It is connected to one (-) input terminal of the high-speed comparator 825a via a. A voltage divided by a resistor R42a and a resistor R43a is applied to the other (+) input terminal of the comparator 825a via a resistor R45a. A capacitor C1 for noise removal is connected to the resistor R43a.
, Oa are connected in parallel. Note that the resistor R48a is a positive feedback resistor for providing hysteresis characteristics, and the capacitor C11a is a feedback capacitor for applying feedback at high speed to improve the output waveform.

The operation in such a configuration will be explained. Leather beam B
When the beam passes over the first beam detector 122a at high speed, a pulse current flows through the first beam detector 122a, and a positive pulse voltage is generated at one (-) input terminal of the comparator 825a. This pulse voltage is applied to the comparator 825a.
is compared with the voltage at the other (+) input terminal of the comparator 825a, and a negative pulse horizontal synchronizing signal a is outputted from the output of the comparator 825a (see FIG. 8).

The details of the first beam detector J22a and the first beam detection circuit 223a have been described above.
22b and the second beam detection circuit 223b have similar configurations.

However, the second beam detector 122b detects the laser beam B
This is for detecting whether or not the laser beam is scanning approximately the center of the light-receiving surface of the first beam detector 122a. (See Figure 4).

Therefore, the output of the comparator 825b outputs the second beam detection signal f, which is a negative pulse that leads the output of the comparator 825a in phase (see FIG. 8).

FIG. 7 shows in detail the portions of the laser oscillator 4, monitor diode 230, light amount control circuit 231, and laser drive circuit 232 in FIG.

In FIG. 7, 809 is a high frequency transistor that performs optical modulation of the laser oscillator (laser diode) 114. Note that the resistor R29 is a current detection resistor.

807 and 808 are high-speed analog switches for modulating the laser oscillator 114, and when a high level voltage is applied to the gate (G) of each analog switch 807 and 808, the drain (D) and sos (S) There will be a low resistance between the two and the switch will turn on. Conversely, when a low level voltage is applied to the gate (G), it becomes high in resistance and turns off. Note that R21 is an analog switch 807
, 808 short-circuit protection resistance during on/off change, 813
, 814 are gate drivers for the analog switches 807 and 808, CO2 and CO3 are speed-up capacitors, and R24 and R25 are gate drivers 813 and 814.
is the input resistance of

815 and 816 are exclusive OR circuits (hereinafter abbreviated as FOR circuits), which change according to the output d of a two-man power AND circuit (hereinafter abbreviated as AND circuit) 820. AND
In the circuit 820, when either of the two inputs becomes low level, the output d becomes low level, and the FOR circuit 815
The output becomes low level, turning on the analog switch 807 and turning on the laser oscillator 114.

The conditions for the output d of the AND circuit 820 to be low level are as follows:
Either the video image data b (see FIG. 8) from the print data writing control circuit 208 is at a low level, or the light amount sample signal C (the eighth (see figure) is at low level.

When both inputs of the AND circuit 820 are at high level, F
The output of the OR circuit 816 becomes low level, turning on the analog switch 808 and turning off the laser oscillator 114.

806 is an operational amplifier, which constitutes a voltage follower circuit. Dot is a Zener diode that regulates the output of the laser oscillator 114 to be within the maximum rating. The resistor R19 and the capacitor COI constitute an integrating circuit, and the resistors R1 and R9 are discharge resistors that discharge the charge of the capacitor Cot at a constant rate. Reference numeral 804 denotes an analog switch, the gate (G) of which is connected to an inverter 805, and the light amount sample signal C, which is the output of the OR circuit 261, is input to the input of the inverter 805.

803 is a transistor for level conversion, R22 is a base current limiting resistor of the transistor 803, and R18 is a current limiting resistor when charging the capacitor COI. 802
is a comparator, and this comparator 802 has a resistor R
14. Hysteresis characteristics are provided by the action of R15.

The output voltage of the operational amplifier 801 is applied to one (+) input terminal of the comparator 802 via a resistor R14. The operational amplifier 801 amplifies the output signal of the monitor diode 230 that detects the optical output from the laser oscillator 114. Resistors R12 and R13.

VR old is a resistor that regulates the amplification degree of the operational amplifier 801. Therefore, by changing the variable resistor VROI, the amplification degree of the operational amplifier 801 can be changed.

A resistor R1l is a load resistance of the monitor diode 230, and a voltage proportional to the output current of the monitor diode 230 is obtained across the resistor RLI. Since the output current of the monitor diode 230 is proportional to the optical output of the laser oscillator 114, the optical output of the monitor diode 114 can be adjusted by varying the variable resistor VROI.

The other (-) input terminal of the comparator 802 has two - The light amount setting voltage of the oscillator 114 is applied.

The light amount setting voltage is output from an operational amplifier 819 that constitutes a voltage follower. A voltage divided by an exposure adjustment volume 821 and a resistor R31 is input to one (+) input terminal of the operational amplifier 819.
By varying the exposure adjustment volume 821, the output voltage of the operational amplifier 819 can be changed.

The condition that the light amount sample signal C, which is the output of the OR circuit 261, becomes low level is when the laser-on signal e from the print data write control circuit 208 (see FIG. 8) and the output signal of the timer 260 both become low level. be. The timer 260 is, for example, a monostable timer, and the first
The operation starts at the rising edge of the first beam detection signal a, which is the output of the beam detection circuit 223a. Note that the time t2 set in the timer 260 is within one cycle of the first beam detection signal a. Therefore, the output of the timer 260 becomes one high level and one low level during one cycle of the first beam detection signal a, and is output in synchronization with the first beam detection signal a.

The timer 270 is, for example, a monostable timer, and starts operating at the rising edge of the second beam detection signal f, which is the output of the second beam detection circuit 223b. Note that the time t5 set in the timer 270 is longer than the period t4 of the second beam detection signal f. Therefore, the output g of the timer 270 is transmitted to the second beam detector 12 as shown in FIG.
2b is at a high level when it is detecting the laser beam B, and is at a low level when it is not being detected. and,
The output g of the timer 270 is input to the input/output port 207 and processed.

The operation shown in FIG. 7 in such a configuration will be explained. First, the laser on signal e from the print data write control circuit 208
goes from high level to low level, laser oscillator 1
1.4 has not emitted light yet, so the timer 260 does not operate and its output is at a low level. Therefore, the light amount sample signal C, which is the output of the OR circuit 261, becomes low level.

When the light amount sample signal C becomes low level, the analog switches 804 and 807 are turned on, but the capacitor CO
Since I is not charged, the output of the operational amplifier 806 is Ov, and the modulation transistor 809 is not turned on. Therefore, no current flows through the laser oscillator 114.

At this time, no current flows through the monitor diode 230, so the output of the comparator 802 becomes low level.
Since the transistor 803 is turned off, the resistors R18 and R
The capacitor COI is charged through 19. When charging, resistor R18゜R19, capacitor C
The time constant of 01 is selected to be about several tens of times the line period. If the value of this time constant is very small, the response of the stabilizing circuit will be too fast, and the fluctuations in the optical output level of the laser oscillator 114 will become large. In addition, if it is too large, the response will be poor and it will take time for the optical output of the laser oscillator 114 to stabilize.
The output voltage of the operational amplifier 806 also gradually increases. Therefore, as the base voltage of the laser modulation transistor 809 increases, a current flows to the collector. When this collector current exceeds the threshold current of the laser oscillator 114, the laser oscillator 114 starts to oscillate. When the laser oscillator 114 oscillates, current flows through the monitor diode 230, and one of the operational amplifiers 801 (
The voltage at the input terminal (+) increases, and the output voltage is also an amplified value of the input voltage.

Then, the output voltage of the operational amplifier 801 is determined by the comparator 80.
When the voltage at the other (=) input terminal of 2, that is, the laser light amount setting voltage or higher, the output of the comparator 802 changes from low level to high level, and the output of the transistor 80
3 is turned on, and the capacitor C01 is discharged through the resistive layer 9.

Therefore, the base voltage of the modulation transistor 809 also decreases, and the optical output of the ray→no'' oscillator 114 decreases.

When the optical output of the laser oscillator 114 decreases, the voltage at one (→-) input terminal of the comparator 802 also becomes lower than the laser light intensity setting voltage, and the L transistor 803 is turned off again, and the capacitor COI is charged again through the resistor R18°R19. Will be uploaded. In this way, the laser oscillator 11
Once the optical output of No. 4 reaches the laser beam intensity setting voltage, the comparator 802 gradually repeats on and off around the laser beam intensity setting voltage, and the optical output of the laser oscillator 114 becomes stable.

At this time, since the mirror motor 117 has been driven in advance, the rotating mirror 116 is rotating.

Therefore, the laser beam B output from the laser oscillator 114 is scanned by the rotating mirror 116 and is incident on the first beam detector 122a and the second beam detector 122b. The case of the incident laser beam B or the laser beam Bo shown in FIG. 4 will be explained below.

First beam detector 122a, second beam detector 122b
When the laser beam is incident on the laser beam, the first beam detection circuit 223a outputs a first beam detection signal (horizontal synchronization signal) a, and the second beam detection circuit 223b outputs a second beam detection signal f. When the first beam detection signal a is output, the timer 260 starts operating. At this time, OR
Since the laser-on signal e, which is one input of the circuit 261, is at a low level, the output of the timer 260 appears as it is in the light amount sample signal C that is its output.

When the first beam detection signal a is input to the timer 260,
The output changes from low level to high level, and the light amount sample signal C output from the OR circuit 261 also changes from low level to high level, so the analog switch 807 is turned off.
The analog switch 808 is turned on, and the laser oscillator 1
14 stops the oscillation operation. On the other hand, analog switch 8
04 is turned off, the capacitor COI is not charged or discharged, and the light amount stabilizing operation of the laser oscillator 114 is completed. While the timer 260 is operating (t
l) continues this state.

When timer 260 has finished operating, its output is
Fixed period (t3) until beam detection signal a is output
, becomes low level, and the analog switches 804, 80
7 is turned on to stabilize the light amount of the laser oscillator 114.

Therefore, a portion of the laser beam B from the laser oscillator 114 is detected line by line based on the first beam detection signal a, and a portion of the laser beam B from the laser oscillator 114 is detected by the monitor diode 230, and
The amount of light is controlled uniformly.

Next, when the horizontal synchronizing signal a output from the first beam detection circuit 223a is output to the print data write control circuit 208, the video image data b from the external device is sent to the AND circuit 820 after a predetermined time (tl). Send. Then,
The AND circuit 820 outputs a laser drive signal d as shown in FIG.
14 is modulated to write dot image data on the photoreceptor 101.

At this time, the second beam detection signal f is output as shown in FIG. 8, and the timer 270 starts operating at the rising edge of the second beam detection signal f. When the timer 270 starts operating, its output g changes from low level to high level and continues at high level for a set time t5. Then, the second beam detector 1 is restarted every time the next second beam detection signal f is input before reaching time t5.
While 22b is detecting laser beam B, timer 27
The output g of 0 becomes a high level as shown in FIG.

Next, the first beam detector 122a, the second beam detector 1
The laser beam B incident on 22b is the laser beam B1.22b in FIG. Case B2 will be explained.

In this case, since the laser beam is off the light receiving surface of the second beam detector 122b, the second beam detection circuit 223b
The second beam detection signal f remains at a high level. Therefore, timer 270 does not operate and its output g remains at low level. The output g of this timer 270 is taken into the CPU 201 via the input/output port 207, and the operation display section 210 displays the result (if the laser beam deviates upward or downward from the light-receiving surface of the first beam detector 122a). The system will notify you by displaying the following information:

With this configuration, there is no need for special beam adjustment marks or measuring instruments like in the past, and it can be used in small laser optical systems where it is difficult to visually see the laser beam passing through the light receiving surface of the beam detector. Also, it can be confirmed with certainty that the laser beam has scanned the light receiving surface of the beam detector (first beam detector). Therefore, it becomes very easy to adjust the position of the laser beam passing through the beam detector.

In the above embodiment, the second beam detector is placed in front of the first beam detector, but it may be placed behind the first beam detector.

Furthermore, in the embodiment described above, the case where the beam light generating means is a laser oscillator that outputs a laser beam is explained.
It may be possible to output other beam light.

Furthermore, in the above embodiments, a case has been described in which the invention is applied to a beam light scanning device used in an image forming apparatus such as a laser printer, but the present invention is not limited thereto. The present invention can be similarly applied to a beam light scanning device used in an information reading device that optically reads image information using a beam.

Effects of the Invention As detailed above, according to the present invention, there is no need for special beam adjustment marks or measuring instruments, and it is difficult to visually observe the beam light passing through the light receiving surface of the beam detection means. Also in the optical system, it is possible to provide a beam light scanning device in which it can be confirmed with certainty that the light beam has scanned the light receiving surface of the beam detection means, and adjustment work is extremely easy.

[Brief explanation of drawings]

The drawings are for explaining one embodiment of the present invention, and FIG. 1 is a block diagram showing an overview of a beam light scanning device according to the present invention, and FIG. 2 is a block diagram showing an outline of a beam light scanning device according to the present invention. Figure 3 is a schematic configuration diagram of a laser printer.
．． A perspective view illustrating the installation position of the second beam detector, the fourth
Figure 1. FIG. 5 is a block diagram showing the configuration of the control section, and FIG. 6 is a diagram showing the relationship between the second beam detector and the scanned laser beam. FIG. 7 is a detailed configuration diagram showing the second beam detector and the first and second beam detection circuits; FIG. FIG. 8 is a timing chart explaining the operation. 11... Laser oscillator (beam light generating means), 12...
...Rotating mirror, 13...Photoreceptor (scanned surface), ]4
... first beam detection means, I5 ... second beam detection means, 1G ... drive means, 17 ... control means, 18 ... notification means,
101... Photoreceptor, 102... Charger, ]03...
・Electrostatic latent image forming unit (beam light scanning device'), 104・
...Developer, 114...Semiconductor laser oscillator, 116
...Rotating mirror, 122a...First beam detector,
122b...Second beam detector, 201...CP
U, 223a...first beam detection circuit, 223b.
...Second beam detection circuit, 232...Laser drive circuit. Applicant's agent Patent attorney Takehiko Suzue 1071 Figure

Claims (1)

[Scope of Claims] In a beam light scanning device that scans a surface to be scanned by scanning a beam light output from a beam light generating means, a first beam detection means detects the position of the scanned beam light. and a driving means for driving and controlling the beam light generating means based on the beam detection signal of the first beam detecting means, and a driving means disposed in front or behind the scanning direction of the beam light of the first beam detecting means. , a second beam detection means for detecting whether or not the beam light is scanning approximately the center of the light receiving surface of the first beam detection means; and a notification means for notifying the detection result of the second beam detection means. A beam light scanning device comprising: