JPH03134613A - Resonance type light deflector - Google Patents

Abstract

PURPOSE:To reduce the frequency change due to the temperature change by detecting the temperature of a resonance type light deflector and controlling the resonance frequency of the deflector in accordance with this detection result. CONSTITUTION:A resonant scanner 10 is provided with a control circuit 14 and feeds back the detection result of the temperature of a scanner 12 dependent upon a thermistor 16 to apply it to a drive coil in accordance with this detection result, thereby adjusting the amplitude of a mirror 102. Thus, the resonance frequency of the mirror 102 is always fixed. Consequently, the scanner 10 having this constitution is applied to obtain an image recorder or reader where the image size in the subscanning direction is less varied.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention is applied to light beam scanning devices that require highly accurate optical scanning, such as image recording devices and image reading devices for printing plate making. This invention relates to a resonant optical deflector, a so-called resonant scanner.

Specifically, the present invention relates to a resonant optical deflector that can compensate for fluctuations in resonant frequency due to changes in operating temperature.

<Prior art> A light beam scanning device that two-dimensionally scans an object being scanned in the sub-scanning direction using a light beam reflected and deflected in the main-scanning direction is used in various image recording devices and image reading devices. Applied.

This light beam scanning device uses an optical deflector to reflect and deflect a light beam emitted from a light source such as a semiconductor laser in the main scanning direction. The scanned object is conveyed at a speed of 2
Image recording and image reading are performed by scanning dimensionally.

Various optical deflectors such as polygon mirrors and galvanometer mirrors are commonly used as optical deflectors for such optical beam scanning devices, but high-precision optical deflectors such as image recording devices and image reading devices for printing plate making A resonant optical deflector, a so-called resonant scanner, is suitably used in a light beam scanning device that requires scanning.

FIG. 3 shows a partially sectional perspective view of an example of this resonant scanner.

In the resonant scanner 100, a mirror 102 for reflecting a light beam is fixed to a rotor 104. Leaf springs 106 and 108 and leaf springs 110 and 112 are each fixed to the rotor 104 so as to form a cross shape, and each leaf spring is fixed to a housing 114 to support the rotor 104.

Further, a cylindrical magnet 118 is fixed to the right side of the rotor 104 in the figure via a fixing member 116. Also, the magnet 118 is inserted into the head 120 with a small gap.

A drive coil 122 and a pickup coil 124 are arranged in the head 120 as conceptually shown in FIG.
2 forms a motor that drives the resonant scanner 100.

Such a resonant scanner 100 rotates the magnet 118 in the direction of arrow a by passing an alternating current through the drive coil 122, that is, by a motor made up of the magnet 118 and the drive coil 122, and rotates the magnet 118 in the direction of the arrow a. The system consisting of the rotor 104 including the leaf springs 110 and 112 and the mirror 102 is set in a resonant state, and the rotor 104 is greatly oscillated, and the mirror 102 is oscillated in the direction of the arrow to reflect the light beam in the main scanning direction.
It is something that deflects.

Further, the amplitude of the mirror 102 is detected by detecting the bending electromotive force of the pickup coil 124 caused by a change in magnetic flux density due to the rotation of the magnet 118.

Resonant scanner 1 basically having such a configuration
00 is the natural vibration, or resonant frequency, of the system consisting of the rotor 104 including the leaf springs 106 and 108, the leaf springs 110 and 112, and the mirror 102, due to a small forcing force generated on the magnet 118 by the alternating current flowing through the drive coil 122. By forcing the rotor 104 to vibrate, the mirror 102 can be largely oscillated at the resonant frequency. Therefore, by setting the frequency of the alternating current flowing through the drive coil 122 to the resonance frequency, the frequency of optical scanning can be accurately controlled.

Furthermore, as described above, since the mirror 102 is oscillated by bringing the four leaf springs and the movable part such as the rotor 104 including the mirror 102 into a resonant state, the motor consisting of the magnet 118 and the drive coil 122 is used to provide additional power. The amplitude of the mirror 102 can be made very large relative to the magnitude of the external force applied. In other words, a large amplitude can be obtained with less power, that is, a small force.

Furthermore, since the mirror 102 is fixed to the rotor 104 supported by four leaf springs, there is no occurrence of surface tilt that requires correction.

<Problems to be Solved by the Invention> However, such a resonant scanner has a problem in that the resonant frequency changes depending on temperature changes.

As mentioned above, the resonant scanner 1oo has a rotor 10.
Since the mirror 102 is oscillated by making the movable part No. 4 and the four leaf springs resonate, the moment of inertia of the movable part (including the rotor 104 and the mirror 102) is J.
, if the spring constant of the four leaf springs is k, then the resonant frequency f
is, and if the magnitude of the applied external force is M, the damping is proportional damping, and its constant is 0, then the amplitude θf in the resonant state is, and the resonant frequency and amplitude are the same as those of the leaf spring. It is greatly influenced by the spring constant. However, as is well known, the spring constant changes slightly depending on the temperature, and the magnetic flux of the magnet also changes slightly depending on the temperature.

Therefore, the resonant frequency and amplitude of the mirror 102 change depending on the temperature, and the resonant frequency of the resonant scanner 100 has a temperature dependence, for example, (Δf/f)/ΔT−2.
A frequency change of about X10-'/°C occurs.
One of the main causes of this is the above-mentioned temperature change in the spring characteristics, but another major factor is thought to be a change in the swing angle of the scanner. The cause of the change in frequency due to the change in swing angle is that the spring constant decreases as the deformation of the leaf spring increases.

Therefore, in a light beam scanning device that uses a resonant scanner, the main scanning frequency of the light beam changes depending on the operating temperature, the spacing between scanning lines changes, and the image size in the sub-scanning direction becomes incorrect. This is a problem in fields such as the color printing and plate-making field, which require image size accuracy on the order of several tens of micrometers.

In order to solve these problems, we have developed a resonant scanner in which two leaf springs that are combined in a cross shape have different temperature characteristics, one whose spring constant increases and one whose spring constant decreases as the temperature rises. Resonant scanners and the like have been proposed that have a magnetic spring that acts as a spring to compensate for changes in the spring constant of a leaf spring.

However, the former type of resonant scanner has problems with the durability of the leaf springs, and the combination of leaf springs with different temperature characteristics results in unbalanced rotor swings, making it difficult to scan the light beam accurately. The problem is that it cannot be done. In addition, the latter type of resonant scanner has a complicated device, and since magnetic springs, that is, springs based on magnetic circuits, always have hysteresis loss, the vibration of the mirror due to resonance becomes small, and the impact on the drive coil 122 is reduced. It is necessary to increase the applied current, which eliminates the advantage of the resonant scanner that a large mirror swing angle can be obtained with small electric power.

SUMMARY OF THE INVENTION An object of the present invention is to solve the problems of the prior art described above, and to provide a resonant scanner which has a small frequency change due to temperature change and has a simple configuration.

Means for Solving the Problems> In order to achieve the above object, the present invention includes a working temperature detection means, a reflecting mirror that vibrates at a predetermined resonance frequency and reflects and deflects incident light in a one-dimensional direction. A resonant optical deflector is provided, comprising: control means for controlling the swing angle of the reflecting mirror according to a detection result by the temperature detecting means, and controlling the resonant frequency.

<Operation of the Invention> The resonant optical deflector (hereinafter referred to as a resonant scanner) of the present invention includes a temperature detection means and a control means for controlling the resonant frequency according to the detection result by the temperature detection means. It is something.

A resonant scanner uses the frequency of an external force (forced force) applied by a motor consisting of a drive coil and a magnet as the natural frequency of a system consisting of a movable part including a mirror and a leaf spring. By bringing these into a resonant state, it is possible to obtain a large amplitude with small electric power. However, since the spring constant of the leaf spring is temperature dependent, the resonant frequency of the resonant scanner is temperature dependent.

In contrast, the temperature of the resonant scanner is detected by the resonant scanner temperature detection means of the present invention, and the control means controls the swing angle of the mirror according to the detected temperature to control the resonance frequency, so the operating temperature changes. Even in this case, it is possible to scan the optical beam at a constant frequency.

Therefore, the light beam scanning device to which the resonant scanner of the present invention is applied can always record images of a constant image size and read images with high precision even when the operating temperature changes, so it is particularly useful. It is suitably applicable to fields that require high accuracy in image size, such as the field of color printing plate making.

<Embodiments> Hereinafter, a resonant optical deflector (hereinafter referred to as a resonant scanner) according to the present invention will be described in detail based on preferred embodiments shown in the accompanying drawings.

FIG. 1 shows a conceptual diagram of a preferred embodiment of the resonant scanner of the present invention.

The resonant scanner 10 shown in FIG. 1 basically consists of a scanner 12 and a control circuit 14. Further, a thermistor 16 as a temperature detection means is arranged in the head 120 of the scanner 12.

In addition, in the resonant scanner 10 shown in the illustrated example, the scanner 12 is basically the resonant scanner shown in FIG. 3 described above, except that the thermistor 16 is arranged. 00, the same members are given the same numbers and their explanations will be omitted.

In the resonant scanner 10 of the present invention, the temperature is detected by the thermistor 16, and the control circuit 1
4, the resonance frequency is controlled by adjusting the swing angle, that is, the amplitude, of the mirror 102, making it possible to obtain a constant resonance frequency even when the operating temperature changes.

The temperature detection means is not limited to the thermistor 16 shown in the illustrated example, and various temperature detection means such as a resistance temperature detector can be used.

Further, the location of the temperature detection means is also different from that of the head 12 in the illustrated example.
The temperature of the scanner 12, such as the vicinity of the housing 114 or the leaf spring inside the scanner 12, is not limited to 0.
In particular, various locations where the temperature of the leaf spring and the temperature of the head 120 can be suitably measured can be used.

The resonant scanner 10 of the present invention uses this thermistor 1.
The swing angle of the mirror 102 is controlled by the control circuit 14 in accordance with the temperature measurement result obtained by the control circuit 14 so that the resonance frequency is constant.

As mentioned above, the scanner 12 has a temperature dependence on its resonant frequency, and the temperature change in its resonant frequency is approximately (Δf/f)/ΔT=-2X10-'/'e. It is.

The causes of such frequency fluctuations due to temperature changes include changes in the spring characteristics of the leaf spring due to temperature changes, changes in the magnetic flux of the magnet 118, and changes in the rotor 10 caused by these changes.
4 (Mirror) 02) The main cause is a change in amplitude.

In other words, the spring constant of a leaf spring for boat fishing decreases as the temperature rises. Therefore, as the temperature at which the resonant scanner 10 is used changes, the spring constants of the leaf springs 106 and 108 and the leaf springs 110 and 112 change. Here, the resonant frequency of the resonant scanner 10 is a function of the spring constant of the leaf spring, as shown by the following formula,
The resonant frequency also changes depending on the temperature change.

Furthermore, if the electric power applied to the coil made up of the magnet 118 and the drive coil 122 is constant, the amplitude will change due to changes in the spring constant of the leaf spring or changes in the magnetic flux of the magnet 118. The resonant frequency also changes.

The illustrated resonant scanner 10 monitors the temperature of the scanner 12 using the thermistor 16 described above, and adjusts the current applied to the drive coil 122 according to the result, thereby adjusting the amplitude of the rotor 104, as described above. Compensates for changes in resonant frequency and controls the resonant frequency to a constant value. That is, by feeding back the measurement results of the thermistor 16, the resonance frequency is controlled to be constant.

In the illustrated resonant scanner 10, the thermistor 16 is connected to a thermistor output amplifier 20, which in turn is connected to a multiplier 22. This multiplier 22 multiplies the output signal of the thermistor 16 by 1 to a predetermined coefficient, and this coefficient Kl is
6 and 108 and the spring materials of leaf springs 110 and 112,
It is set according to the temperature characteristics, the temperature characteristics of the magnet 118, etc.

On the other hand, the pickup coil 124 is connected to a pickup coil output amplifier 24, and this pickup coil output amplifier 24 is connected to a peak hold circuit 26.

A reference voltage 28 for adjusting the amplitude of the mirror 102 of the resonant scanner 10, a voltage value detected by the thermistor output amplifier 20 and multiplied by 0 by the multiplier 22, and detected by the pickup coil output amplifier 24. The peak voltage value (corresponding to the maximum amplitude of the motor, that is, the swing angle of the mirror 102) is compared, and the difference is sent to the PID controller 30.

This voltage value is subjected to PID calculation by the PID controller 30 into a voltage value with an amplitude correction amount necessary to compensate for frequency changes due to temperature changes, and then sent to a multiplier 32 .

On the other hand, in the pickup output voltage signal from the pickup coil output amplifier 24, a phase compensation circuit 34 compensates for a phase shift caused by waveform shaping, amplification, etc. of the pickup output signal.

In the multiplier 32, the phase-compensated pickup output signal is multiplied by the amplitude correction voltage value from the PID controller 30 to obtain a drive current with an appropriate amplitude so that the resonance frequency is always constant. The output current is sent to the output amplifier 36 as an output current, amplified by the output amplifier 36, and a drive current with an appropriate amplitude is applied to the drive coil 122.

The illustrated resonant scanner 10 has a control circuit 14 configured as described above, and controls the mirror 1 by feeding back the temperature detection result by the thermistor 16 and adjusting the current applied to the drive coil 122.
By adjusting the amplitude of the mirror 102, the resonance frequency of the mirror 102 can be kept constant. Therefore, by applying the resonant scanner 10 of the present invention, it is possible to realize an image recording device and an image reading device that can record images with less deviation in image size in the sub-scanning direction.

FIG. 2 shows an example in which the above-described resonant scanner 10 is applied to an image recording apparatus.

The image recording device 40 shown in FIG. 2 is a character/line image recording device that uses the resonant scanner 10 of the present invention as an optical deflector and performs raster scanning.
Basically, a recording unit 42 that emits a recording laser beam 42a (hereinafter referred to as recording beam 4.2a);
Grating laser beam 44a (hereinafter referred to as grating beam 44a)
) and a grating unit 44 that emits the fθ lens 4.
6, an exposure drum 48 for holding the recording material A in a predetermined position, nip rollers 50 and 52 that nip and convey the recording material A together with the exposure drum 48, and a grating beam 44.
It is composed of a long mirror 54 that reflects the light a in a predetermined direction, a grating 56 and a condensing bar 58, which are image synchronization signal generating means.

In such an image recording device 40, the recording beam 42a and grating beam 44a emitted from each light beam unit are reflected and deflected in the main scanning direction indicated by arrow C by the resonant scanner 10, and then reflected and deflected by the fθ lens 46. The recording beam 42a is adjusted to form a predetermined beam spot on the recording material A, and the recording beam 42a is applied to the recording material A which is nipped and conveyed in the sub-scanning direction indicated by the arrow d by the exposure drum 48 and nip rollers 50 and 52.
An image is formed on the surface, and the image is recorded by scanning and exposing the image two-dimensionally.

On the other hand, the grating beam 44a is reflected by the elongated mirror 54 and scans the grating 56, and the position detection signal of the recording beam 42a,
In other words, it is an image synchronization signal.

The recording unit 42 emits a recording beam 42a, and is configured by integrally uniting a semiconductor laser that emits a recording light beam and a collimator lens that shapes the laser beam emitted from this semiconductor laser. It is something that

On the other hand, the grating unit 44 emits a grating beam 44a, and has basically the same configuration as the recording unit 42 described above, and includes a semiconductor laser as a grating scanning light beam source and a grating beam emitted from the semiconductor laser. A collimator lens for shaping a laser beam is integrated into a unit.

, the recording beam 42a and the grating beam 44a emitted from the respective light beam units are then reflected and deflected in the main scanning direction indicated by arrow C by the resonant scanner 10 of the present invention.

Each light beam reflected and deflected by the resonant scanner 10 then enters the fθ lens 46 and is adjusted so as to form an image at a predetermined position with a predetermined beam spot shape.

The grating beam 44 a that has passed through the fθ lens 46 is reflected upward by the elongated mirror 54 and scans the grating 56 .

The grating beam 44a that has passed through the grating 56 is directed to a condensing bar 58.
The light is focused by the photo multiplier.
The photometer is measured by a photodetector 60 such as the photodetector 60, and converted into an electrical signal.

The grating beam 44a incident on the grating 56 is reflected in the main scanning direction indicated by the arrow C by the resonant scanner 10 in exactly the same way as the recording beam 42a scanning the recording material A.
It is biased. Therefore, a synchronization signal for detecting the accurate position of the recording beam 42a can be obtained from an electrical signal obtained from periodic changes in light intensity in accordance with the scanning of the grating 56 by the grating beam 44a, and from this synchronization signal. The main scanning of the recording beam 42a on the recording material A can be made more precise.

On the other hand, the recording beam 42a that has passed through the fθ lens 46 is
While being held at a predetermined image recording position by the exposure drum 48 and nip rollers 50 and 52, an image is formed on the recording material A that is nipped and conveyed in the sub-scanning direction shown by the arrow d, so that the recording material A is two-dimensionally Scanning exposure is performed to record an image.

Since such an image recording apparatus 40 applies the resonant scanner 10 of the present invention, the main scanning frequency of the recording material A does not change due to temperature changes.
It is possible to record an image with an accurate image size in the sub-scanning direction. Therefore, it is suitably applied to an image recording apparatus for printing plate making, especially color printing plate making, which requires high accuracy in image size.

Above, the resonant optical deflector, that is, the resonant scanner according to the present invention has been described in detail based on the preferred embodiments shown in the attached drawings, but the present invention is not limited thereto, and the gist of the present invention Of course, various changes and improvements can be made without changing the above.

<Effects of the Invention> As explained in detail above, the resonant optical deflector of the present invention detects the temperature of the resonant optical deflector, and adjusts the drive current according to the detection result to adjust the resonant optical deflector. By adjusting the amplitude of the optical deflector, it is possible to always obtain a constant resonant frequency.

Therefore, by applying the resonant optical deflector of the present invention, it is possible to realize an image recording device and an image reading device that have an accurate image size, especially in the sub-scanning direction. It can be suitably applied to fields that require the following.

[Brief explanation of the drawing]

FIG. 1 is a conceptual diagram showing a resonant optical deflector according to the present invention. FIG. 2 is a schematic perspective view of an image recording apparatus to which the resonant optical deflector shown in FIG. 1 is applied. FIG. 3 is a schematic perspective view showing a conventional resonant optical deflector. FIG. 4 is a diagram conceptually showing the head section of the resonant optical deflector shown in FIG. 3. Explanation of symbols 10.100... Resonant scanner, 12... Scanner, 14... Control circuit, 16... Thermistor, 20... Thermistor output amplifier, 22... Multiplier, 32... Multiplier, 24... Pickup coil output amplifier, 26... Peak hold circuit, 28... Reference voltage, 30... PID controller, 32... Multiplier, 34... Phase compensation circuit, 36 ... Output amplifier, 40... Image recording device, 42... Recording unit, 42a... Laser beam for recording, 44... Grating unit, 44a... Laser beam for grating, 46... - fθ lens, 48... exposure drum, 50.52... nip roller, 54... long mirror 56... grating, 58... condensing bar 60... photodetector, 102...・Mirror 104... Rotor, 106.108, 110.11 114... Housing, 116... Fixing member, 118... Magnet, 120... Head, 122... Drive coil, 124...・Pickup coil, A... Recording material 2... Leaf spring, FIG, 1

Claims (1)

[Claims] (1) Use temperature detection means, a reflection mirror that vibrates at a predetermined resonance frequency and reflects and deflects incident light in a one-dimensional direction, and a swing angle of the reflection mirror according to the detection result by the temperature detection means. and a control means for controlling the resonant frequency.