JPS6151822B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical scanning device used in facsimile machines and the like, and more particularly to an optical scanning device with an improved light amount correction circuit.

In optical scanning devices that use rotating mirrors, galvano mirrors, etc., in order to correct physical scanning errors such as division angle error of the rotating mirror and deflection angle error of the galvano mirror, it is necessary to set a fixed position on the optical scanning surface. must be detected as a phase synchronization signal by photoelectric conversion, and phase synchronization must be performed based on this phase synchronization signal.

In this case, since the phase synchronization signal is detected by photoelectric conversion, if the amount of light of the scanning light flux changes at the phase synchronization signal detection position on the optical scanning surface, it will immediately affect the accuracy of the signal. The amount of light of the scanning light beam at the detection position must always be maintained at a constant value.

However, in the optical scanning device, there is a possibility that unintended fluctuations in the amount of light of the scanning light beam may occur due to various factors.

For example, when modulating light from a light source with an ultrasonic optical modulator in the process of obtaining a scanning light beam, the level within the drive band caused by the high frequency amplifier that drives the ultrasonic optical modulator or the optical modulator itself If there is a fluctuation, the modulated light and, ultimately, the amount of light of the scanning light beam will fluctuate.

Further, when a rotating mirror is used, each reflecting surface of the rotating mirror often does not have a uniform reflectance due to manufacturing reasons, and this also causes variations in the amount of light of the scanning light beam.

Therefore, conventionally, some optical scanning devices have been provided with a light amount correction circuit that corrects the light amount so that the fluctuation in the light amount does not occur. However, the light amount correction circuit in this conventional device uniformly corrects the light amount of the scanning light beam over the entire section of the optical scanning surface.

However, in an optical scanning device installed in a facsimile device or the like to read or record images, in the image section where the image is processed,
There is a demand for freely varying the light quantity of the scanning light beam, and this demand is essential, especially in image recording apparatuses, since the light quantity is directly related to the recording density.

For this reason, if the light intensity of the scanning light beam is uniformly corrected over the entire section of the optical scanning surface as in the conventional optical scanning device, if the light intensity of the scanning light beam in the image section is changed, the phase synchronization The light intensity of the scanning light beam at the signal detection position also changes, resulting in a drawback that the light intensity cannot be maintained constant.

The present invention has been made to solve the above-mentioned conventional drawbacks, and even if the light intensity of the scanning light beam changes in other sections, the light intensity of the scanning light beam is always maintained at a constant value at the phase synchronization signal detection position. It is an object of the present invention to provide an optical scanning device that can detect a more accurate phase synchronization signal and perform highly accurate optical scanning.

The present invention will be explained below based on embodiments shown in the drawings.

In FIG. 1, reference numeral 1 denotes a light source such as a laser device, and the amount of light emitted can be adjusted manually or automatically by a light source control device 2. The light flux emitted from the light source 1 has its light intensity adjusted by an attenuator 3, and then enters an ultrasonic light modulator 4. This incident light flux is transmitted to the optical modulator drive circuit 5
A high frequency signal a input to the ultrasonic optical modulator 4 from
Based on this, the light is diffracted into a zero-order beam I ₀ and other first-order beams I ₁ , etc. Since there is a correspondence relationship (non-linear relationship) between the light amount of the diffracted light beam such as the first-order light beam _I1 and the power amount of the high-frequency signal a, if the power amount of the high-frequency signal a is changed, the first-order The amount of diffracted light beams such as the light beam I ₁ also changes.

In this embodiment, the first-order light beam of the diffracted light beam is
I ₁ is incident on the rotating mirror 6. This primary luminous flux I ₁
The reflected light flux is the scanning light flux I′ ₁ , and the scanning light flux I′ ₁
The rotating mirror 6 is rotated by the motor 7 to scan the optical scanning surface 8 . This optical scanning surface 8
is divided into an image section A for image processing, a phase synchronization section B for performing phase synchronization, and a blank section C that is neither image section A nor phase synchronization section B.

A phase synchronization detector 9 is provided in the phase synchronization section B, and when the phase synchronization detector 9 detects the scanning light beam _I'1 , it outputs a detection signal b. This detection signal b is amplified by a phase synchronization amplifier 10 and made into an amplified detection signal d, which is then input to a phase signal detection circuit 11, which converts it into a rectangular phase synchronization signal e, and then a mirror synchronization circuit. 12 is input.

The rotation of the motor 7 is detected by a motor synchronization detector 13 and converted into a motor synchronization detection signal f, which is also input to the mirror synchronization circuit 12.
This mirror synchronization circuit 12 generates a mirror synchronization signal gi (i=1,
2..., N) is created. Note that N is the number of mirror surfaces of the rotating mirror 6.

The mirror synchronization signal g-i indicates the period during which the primary light beam _I1 is incident on each mirror surface of the rotating mirror 6, and the mirror surface synchronization signal g-i determines the amount of light on each surface in the image section, which will be explained next. A correction circuit 14 and a surface light amount correction circuit 15 for each phase synchronization section are synchronized with each of the mirror surfaces.

The surface light amount correction circuit 14 for each image section has one terminal connected to the input terminal 16 in common, and the other terminal of each surface level adjuster 17-i (i=1, 2..., N) connected to an analog terminal. Switch 18-i (i
=1, 2...,N), and are commonly connected to the output terminal 19 via the analog switches 18-i
is AND gate 20-i (i=1, 2..., N)
It is turned on and off by the output.

The mirror synchronization signal gi is input to one input terminal of each AND gate 20-i, and the image section signal h is input to the other input terminal. This image section signal h is generated from the motor synchronization signal b and other reference clock signals by a circuit not shown, and is output only while the scanning light beam _I'1 scans the image section A.

On the other hand, each surface light amount correction circuit 15 in the phase synchronization section
is a surface level adjuster 22-i (i=1, 2...,
Connect the other terminal of N) to analog switch 2.
3-i (i=1, 2..., N), and each analog switch 23-i is connected to the output terminal 24 through an AND gate 25-i (i=1, . . . , N).
2, . . . , N) are turned on and off by the output.

The mirror synchronization signal g-i is input to one input terminal of each AND gate 25-i, and the phase synchronization interval signal k is input to the other input terminal. This phase synchronization interval signal k is generated by a circuit not shown from the motor synchronization signal f and other reference clock signals, and is
_I'1 is output only while scanning the phase synchronization section B.

Therefore, while the scanning light beam I' ₁ by the i-th mirror surface of the rotating mirror 6 scans the image section A,
Both the specular synchronization signal g-i and the image section signal h are output, and as a result of opening the AND gate 20-i, the analog switch 18-i of the surface light amount correction circuit 14 for each image section is turned on, while the scanning light flux While _I1 ' scans the phase synchronization section B, the mirror surface synchronization signal g-i and the phase synchronization section signal k are both output, and as a result of the AND gate 25-i being opened, the surface light amount correction circuit for each phase synchronization section 15 analog switches 23-i are turned on. During that time, other analog switches 18-j, 23-j (j
=i) is off.

Note that each surface level adjuster 17-i and 2
In 2-i, the level adjustment degree is preset so as to correct the non-uniformity of the reflectance of each of the corresponding mirror surfaces, which is determined in advance.

The output of the full surface level adjuster 26 is input to the input terminal 16 of the surface light amount correction circuit 14 for each image section. On the other hand, the input terminal 21 of the surface light amount correction circuit 15 for each phase synchronization section has the following input. That is, the amplified detection signal d output from the phase synchronized amplifier 10 is also input to the sample hold circuit 27. This sample-and-hold circuit 27 holds the signal level of the amplified detection signal d based on a sample-and-hold signal input from a sample-and-hold signal generation circuit (not shown), and outputs this hold level m to the level comparator 28.

The sample hold signal is created based on the motor synchronization signal f and other reference clock signals, and is a reference position signal of the phase synchronization signal e (meaning the true phase detection position on the optical scanning surface 8 among the phase synchronization signals e). However, in reality, the time width is set slightly wider before and after the width of the rise or fall time of the phase synchronization signal e. The meaning of this wide range will be discussed later.

The level comparator 28 is a reference level adjuster 2
The reference level n preset in step 9 is compared with the hold level m, and if it is lower than the hold level m or reference level n, the output o is increased in proportion to the comparison, and conversely, if the hold level m is higher than the reference level n. Lower the output o.

The output o of the level comparator 28 is amplified by a buffer amplifier 30, adjusted by a surface level adjuster 31, and then inputted to the input terminal 21 of each surface light amount correction circuit 15 in the phase synchronization section.

Therefore, while the scanning light beam I' ₁ by the i-th mirror surface of the rotating mirror 6 scans the image section A, the analog switch 18-i is turned on as described above, and the output of the entire surface level adjuster 26 is It is corrected by each surface level adjuster 17-i according to the reflectance of the same mirror surface and output to the output terminal 19 of each surface light amount correction circuit 14 for the image section.

Similarly, while the scanning light beam I' ₁ by the i-th mirror surface of the rotating mirror 6 scans the phase synchronization section B, the analog switch 23-i is switched as described above.
is turned on, the output of the entire surface level adjuster 31 is corrected by each surface level adjuster 22-i according to the reflectance of the same mirror surface, and the output of the surface light amount correction circuit 15 for each phase synchronized section is corrected according to the reflectance of the mirror surface.
It is output to the output terminal 24 of.

The surface light amount correction circuit 14 for each image section and the surface light amount correction circuit 1 for each phase synchronization section obtained in this way
The outputs of 5 are temporally synthesized by a signal addition circuit 32 to form a light intensity correction baseband signal p, and the signal p is converted by a nonlinear correction amplifier 33 into a signal between the high frequency signal a and the light intensity of the primary beam I. After compensating for nonlinear relationships, the signal is input to the amplitude modulation circuit 34 of the optical modulator drive circuit 5.

Based on this input, the amplitude modulation circuit 34 amplitude modulates the carrier wave for driving the ultrasonic optical modulator 4,
Create a modulated signal. This modulation signal is amplified by the high frequency amplifier circuit 35 to become the high frequency signal a, which is input to the ultrasonic optical modulator 4 as described above to control the light amount of the primary light beam _I1 .

Therefore, in the apparatus of this embodiment, the image section A
The amount of light of the scanning light beam I' ₁ in the image area is corrected by the variation due to the non-uniformity by changing the high-frequency signal a according to the non-uniformity of the reflectance of each mirror surface by the image section each surface light amount correction circuit 14. Corrected so that this does not occur.

Furthermore, by changing the output of the overall level adjuster 26, the light amount of the scanning light beam _I'1 in the image section A is changed entirely.

On the other hand, the light intensity of the scanning beam I' ₁ in the phase-locked section B is determined by a phase-locked section light amount correction circuit comprising a sample hold circuit 27, a level comparator 28, a reference level adjuster 29, a phase-locked section light amount correction circuit 15, etc. By controlling the high frequency signal a by
This will be corrected independently of the light intensity of I′ ₁ .

In this correction, the non-uniformity of the reflectance of each mirror surface is corrected by the surface light amount correction circuit 15 in each phase synchronization section, but the light amount of the scanning light flux I' ₁ through all the mirror surfaces corresponds to the same light amount. The hold level m and the reference level n are compared by the level comparator 28, and the output o of the same level comparator 28, and thus the high frequency signal a, are changed according to the comparison result, so that the output corresponds to the reference level n. It is automatically corrected to a constant value.

Since the light amount correction by this phase synchronized section light amount correction circuit is performed independently of the light amount of the scanning light beam I' ₁ in the image section A as described above, the output of the overall level adjuster 26 is changed, and the image section Even if the light intensity of the scanning beam I′ ₁ at A is changed,
The scanning light beam I' ₁ in the phase synchronization period B is always maintained at a constant value.

Further, even if the light source control device 2 changes the light intensity of the light source 1 or the attenuator 3 changes the light intensity of the output light beam of the attenuator 3, the scanning light beam I' ₁ in the phase synchronization period B is always maintained at a constant value. Ru.

As mentioned above, the sample and hold signal has a slightly wider temporal width before and after the reference position signal width of the phase synchronization signal e, but this is because, in the case of this device, the reference position signal is accurately detected. In order to do this, the light intensity correction by the phase synchronized interval light intensity correction circuit must have been completely completed by the time the reference position signal is detected, and there is also a time delay in the loop system of the light intensity correction circuit. This is due to the fact that you have to take your time with consideration.

Furthermore, if the light intensity correction circuit for the image section A is provided with a function of maintaining the light intensity constant in the same way as the phase synchronization section light intensity correction circuit, the light intensity of the scanning luminous flux I ₁ ' in the image section A can also be maintained constant. Needless to say.

Furthermore, when a galvanometer mirror is used instead of the rotating mirror 6, the mirror synchronization circuit 12 and the surface light amount correction circuits 14 and 15 are no longer necessary.

As described above, the optical scanning device according to the present invention has a phase synchronization section light amount correction circuit that corrects the light amount of the scanning light beam in the phase synchronization period so that it always has a constant value, independently of the light amount in other sections such as the image section. By providing a It is possible to obtain the excellent effect of being able to perform optical scanning with high precision.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of a main part of an embodiment of an optical scanning device according to the present invention, and FIG. 2 is a timing waveform diagram showing signals of the main part of this embodiment. 6... Rotating mirror, 8... Optical scanning surface, 9... Phase synchronization detector, 12... Mirror surface synchronization circuit, 14... Image section each surface light amount correction circuit, 15... Phase synchronization section each surface light amount correction circuit, 27...Sample hold circuit, 28...Level comparator, 29...Reference level adjuster.

Claims (1)

[Claims] 1. An optical scanning device that scans an optical scanning surface by moving a scanning beam using a rotating mirror, which includes a phase signal detector and holds the level of the signal detected by the phase signal detector. A sample and hold circuit, a reference level adjuster that outputs a signal at a preset level, and a signal that compares the outputs of the sample and hold circuit and the reference level adjuster and outputs a signal at a level according to the result. a level comparator, and a phase synchronization interval each surface light amount correction circuit having a level adjuster into which a correction coefficient for each surface is input in advance in order to correct the non-uniformity of reflectance of each mirror surface of the rotating mirror. An optical scanning device comprising: inputting a level signal automatically adjusted by the level comparator to each surface light amount correction circuit in the phase synchronization section.