JPH07318985A - Optical scanner - Google Patents

Abstract

PURPOSE:To fix scanning light beam intensity in an optical scanner using an optical deflector. CONSTITUTION:The optical scanner is constituted of the optical deflector 1, a light source 7, a voltage control means 23 controlling a voltage applied to the optical deflector 1, an attitude variable mechanism 8 varying the attitude of the optical deflector 1, an attitude control means 24 controlling the attitude variable mechanism 8, a light receiving part 9 detecting zero-order light beam intensity transmitting through the optical deflector 1 and a light source control means 25 controlling the intensity of the light source 7. The attitude control means 24 controls the attitude variable mechanism 8 so that an incident angle of an incident light beam incident on the optical deflector 1 becomes the incident angle maximizing the diffraction efficiency of a scanning beam based on the magnitude of the voltage applied to the optical deflector 1 while referring to an incident angle table 21. The light source control means 25 controls the intensity of the light source 7 so that the scanning beam intensity is fixed based on the intensity of the zero-order light detected by the light receiving part 9 and the intensity of total transmission beam obtained by referring to an intensity table 22.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical scanning device.

[0002]

As is well known, a bar code reader, a laser printer and the like in a POS system are equipped with an optical scanning device. For example, in a bar code reader, an optical scanning device is used to deflect a light beam and scan the bar code.

The conventional optical scanning device is generally of the type that performs optical scanning by mechanically rotating a polygon mirror or a galvano mirror.

[0004]

As described above, the optical scanning device having the mechanically movable portion has poor controllability and causes a response delay, and the optical axis is displaced due to mechanical vibration. was there.

The present invention has been made in view of the above-mentioned problems of the prior art. It has no mechanically movable parts, is electrically controllable, has good controllability, and is capable of diffracting light other than scanning light. An object of the present invention is to provide an optical scanning device capable of reducing the intensity of light and making the intensity of scanning light constant.

[0006]

The present invention adopts the following means in order to solve the above problems.

<Summary of the Invention> The optical scanning device of the present invention comprises:
(A) A liquid crystal (5) is inserted between the transparent electrodes (2, 2) arranged opposite to each other, and when a voltage is applied between the transparent electrodes (2, 2), parallel stripes functioning as a diffraction grating are formed on the liquid crystal ( 5), the optical deflector (1) in which the pitch of the parallel stripes changes according to the magnitude of the applied voltage, and (b) the light source (7) that emits light toward the optical deflector (1). ), (C) voltage control means (23) for controlling the voltage applied to the optical deflector (1), and (d) the incident angle of light of the light source (7) with respect to the optical deflector (1). A posture changing mechanism (8) that changes the posture of the optical deflector (1) so that it changes (e)
Based on the magnitude of the voltage applied to the optical deflector (1), the incident angle of the incident light incident on the optical deflector (1) is an incident angle that maximizes the diffraction efficiency of the scanning light, Attitude control means (24) for controlling the attitude varying mechanism (8) is provided, and the light emitted from the light source (7) is deflected by the optical deflector (1) to be scanning light. Corresponding to claim 1]. The points of each configuration will be described below.

[Optical Deflector] When light is incident on the optical deflector (1), diffracted light is generated on the exit side. When any of the diffracted light is used as the scanning light, the incident light is deflected by the optical deflector (1) to become the scanning light.

As a typical example of the liquid crystal (5) used in the light deflector (1), there may be mentioned Chemical formula 1, but it is not limited to this.

[0010]

[Chemical 1]

[Light Source] The light emitted from the light source (7) is S
Linearly polarized light such as polarized light or P-polarized light is preferable. When the light emitted from the light source (7) is non-linearly polarized light, a polarizer is arranged between the light source (7) and the optical deflector (1) so that only the linearly polarized light component is ). However, the non-linearly polarized light may be directly incident on the optical deflector (1).

As the light source (7), a laser oscillator, an LED
(Light emitting diode), LD (laser diode), fluorescent lamp, CRT (cathode ray tube), PDP (plasma display), ELD (electroluminescence display), white lamp, halogen lamp and the like can be exemplified.

[Voltage Control Means] The voltage control means (23) temporally changes the magnitude of the voltage applied between the transparent electrodes (2, 2) of the optical deflector (1). The applied voltage can be a DC voltage or an AC voltage. By controlling the applied voltage by the voltage control means so that the temporal change rate of the deflection angle of the scanning light becomes constant, the scanning speed of the scanning light can be made constant.

[Attitude changing mechanism] The attitude changing mechanism (8) supports, for example, the optical deflector (1) rotatably via a rotating mechanism, and the rotating mechanism is driven by a stepping motor. Can be configured. However, the configuration of the attitude varying mechanism (8) is not limited to this, and in short, the optical deflector
It is sufficient that the posture of the light deflector (1) can be changed so as to change the incident angle of the light of the light source (7) with respect to (1).

[Attitude control means] The attitude control means (24) controls the attitude variable mechanism (8) and the attitude of the optical deflector (1) by utilizing the characteristics of the optical deflector (1). It was done like this. The characteristic is that the optical deflector (1) has an incident angle of light that maximizes the diffraction efficiency of the scanning light, and this incident angle depends on the magnitude of the voltage applied to the optical deflector (1). Changes accordingly,
That is.

The attitude control means (24) stores an incident angle table (21) in which the instantaneous value of the voltage applied to the optical deflector (1) and the incident angle that maximizes the diffraction efficiency of the scanning light are stored in correspondence with each other. It is also possible to prepare and to determine the incident angle from the instantaneous value of the voltage applied to the optical deflector (1) with reference to the incident angle table (21).

<Additional Constituent Elements of the Present Invention> The present invention comprises the above-mentioned basic constituent elements, but can be realized even if the following constitution is added. That is, (f) a light receiving section (9) for detecting the intensity of 0th-order light transmitted through the optical deflector (1)
(G) Based on the intensity of the 0th-order light detected by the light receiving section (9) and the intensity of the total transmitted light transmitted through the optical deflector (1), the intensity of the scanning light is kept constant. A light source control means (25) for controlling the intensity of the light source (7) is added (corresponding to claim 3).

[Light-Receiving Section] The light-receiving section (9) can be exemplified by a photodiode, a phototransistor, a CdS photoconductive cell and the like.

[Light Source Control Means] The light source control means (25) controls the intensity of the light source (7) so that the intensity of the scanning light becomes constant by utilizing another characteristic of the light deflector (1). It is a thing. The characteristic is that the diffraction efficiency of the diffracted light changes with the change in the magnitude of the voltage applied to the optical deflector.

The light source control means (25) stores the total transmitted light intensity, the light source (7) intensity, and the incident angle corresponding to the instantaneous value of the voltage applied to the optical deflector (1) in association with each other. Strength table (22)
Prepare and refer to this intensity table (22) and refer to the light source (7)
It is also possible to obtain the total transmitted light intensity from the intensity of the light and the incident angle corresponding to the instantaneous value of the voltage applied to the optical deflector (1).

The light source control means (25) stores an intensity table (corresponding to the intensity of the total transmitted light, the intensity of the light source (7) and the instantaneous value of the voltage applied to the optical deflector (1) in association with each other. 22) and refer to this intensity table (22) to obtain the total transmitted light intensity from the intensity of the light source (7) and the instantaneous value of the voltage applied to the optical deflector (1). It is also possible. This can increase the processing speed.

<Applicability of the Present Invention> The present invention can be applied to an optical scanning device incorporated in a bar code reader, a laser printer or the like.

[0023]

[Action]

<Operation of the present invention> When a voltage is applied to the transparent electrodes (2, 2) of the optical deflector (1), parallel stripes are generated in the liquid crystal (5), and the parallel stripes function as a diffraction grating. When the magnitude of this applied voltage is changed with time, the diffraction angle changes.

The light emitted from the light source (7) is incident on the optical deflector (1) to generate diffracted light on the emission side of the optical deflector (1).
Of the diffracted light, the + 1st order diffracted light is used as the scanning light. The attitude control means (24) controls the attitude variable mechanism (8) so that the incident angle of the incident light incident on the optical deflector (1) becomes the incident angle that maximizes the diffraction efficiency of the scanning light. At this incident angle, the diffraction efficiency of diffracted light other than the 0th order light and the scanning light becomes extremely small. Therefore, the diffracted light does not interfere with the scanning light.

<Operation when Additional Components are Added>
In the light source control means (25), the scanning light intensity is obtained from the total transmitted light intensity and the 0th-order light intensity detected by the light receiving portion, the intensity difference between this scanning light intensity and the target value is obtained, and the intensity difference is determined according to this intensity difference Control the intensity of the light source. That is, when the scanning light intensity is higher than the target value, the light source intensity is controlled to be smaller, and when the scanning light intensity is lower than the target value, the light source intensity is controlled to be higher. To do. Thereby, the intensity of the scanning light is always controlled to be constant (target value).

[0026]

【Example】

[V. G. M Phenomenon] Before describing the optical scanning device of the present invention, V. G. The M phenomenon and the optical deflector utilizing this phenomenon will be described.

It has been reported that when a certain kind of nematic liquid crystal molecule is sandwiched between transparent electrodes and a DC or AC voltage is applied, parallel stripes with a pitch of several μm appear when the voltage exceeds a certain threshold value. (BHSoffer et, a
L.Opt.Eng.22,6,1983). This phenomenon is G. M (Varia
ble Grating Mode). The parallel stripes are caused by the distribution of the secondary alignment in the liquid crystal, and the pitch of the parallel stripes (that is, the spatial frequency) changes depending on the magnitude of the applied voltage.

Many liquid crystals in which the VGM phenomenon occurs have a dielectric constant difference Δε <0. V. G. A typical example of a liquid crystal in which the M phenomenon occurs is shown in Chemical formula 2.

[0029]

[Chemical 2]

Since the fringes act as a diffraction grating, the diffraction angle can be changed by changing the applied voltage.
It is known that the pitch of the parallel stripes becomes narrower in proportion to the increase of the applied voltage and the diffraction angle becomes larger.

FIG. 3 shows this V. G. It is a basic block diagram of the optical deflector using the M phenomenon. In the optical deflector 1, a pair of transparent glass plates 4 and 4 provided with a transparent electrode 2 and an alignment film 3 on one surface are arranged to face each other, and a V. GM
A liquid crystal 5 in which a phenomenon occurs is inserted, and a drive circuit 6 is connected to the transparent electrodes 2 and 2 so that an AC voltage or a DC voltage can be applied.

[Principle of Optical Scanning Device] Next, the principle of the optical scanning device using the optical deflector 1 will be described with reference to FIGS. 4 to 7.

When the light emitted from the light source 7 enters the optical deflector 1, as shown in FIGS. 4 and 5, the transmitted light (0th order light) and the ± 1st, ± 2nd, ... Light appears (in the figure, high-order diffracted light of 3rd order or higher is omitted because its intensity is very small). Of these diffracted lights, the diffracted light with the highest intensity is used as the scanning light. Usually, the + 1st order diffracted light is often used as the scanning light.

Here, it is reported that when the incident light is linearly polarized, the polarization directions of the odd-order diffracted light and the zero-order light and the even-order diffracted light are orthogonal to each other (BHSoffer et, al. O.
pt.Eng.22,6,1983). That is, if the incident light is S-polarized light, the 0th-order light and the even-order diffracted light are S-polarized light, and the odd-order diffracted light is P-polarized light.

When a voltage whose magnitude changes with time is applied to the optical deflector 1 by the drive circuit 6, the light scans one straight line as shown in FIG. Figure 7
Shows an example of a voltage waveform applied to the optical deflector 1, FIG. 7 (A) shows the case of an AC voltage, and FIG. 7 (B).
Is the case of DC voltage. Although the AC signal is given as a pulse in this drawing, the present invention is not limited to this, and may be an AC signal whose voltage value continuously increases and decreases.

[Characteristics of Optical Deflector] The optical deflector 1 configured as described above has the following characteristics. 1. Relationship between Applied Voltage and Spatial Frequency There is a linear relationship between the applied voltage V applied to the optical deflector 1 and the spatial frequency fs of the parallel stripes generated in the optical deflector 11, as shown in FIG.

2. Relationship between Applied Voltage and Diffraction Efficiency The diffraction efficiency of the diffracted light changes as the voltage value applied to the optical deflector 1 changes. FIG. 9 shows the relationship between the applied voltage V and the diffraction efficiency Ed of the + 1st order diffracted light. Therefore, when the intensity of the incident light on the optical deflector 1 is constant, the intensity of the + 1st order diffracted light, which is the scanning light, changes with the change in the applied voltage.

3. Relationship between Incident Angle and Diffraction Efficiency When the incident angle of the incident light on the optical deflector 1 changes, the diffraction efficiency of the diffracted light changes. FIG. 10 shows the relationship between the incident angle θ and the diffraction efficiency Ed of each diffracted light when the optical deflector 1 has a predetermined spatial frequency. As described above, the optical deflector 1 has the incident angle θp that maximizes the diffraction efficiency of the + 1st order diffracted light, and at this incident angle θp, the diffracted light other than the + 1st order and 0th order diffracted light is negligible. Be efficient. Figure 11
Shows the state of the diffracted light at this time. It has been confirmed that the value of the incident angle θp changes according to the magnitude of the applied voltage applied to the optical deflector 1.

[Control Principle of Optical Scanning Apparatus of the Present Invention] In the optical scanning apparatus of the present invention, the intensity of the scanning light is controlled to be constant by skillfully utilizing the characteristics of the optical deflector 1. The control principle will be described below.

Intensity I of light incident on the optical deflector 1_iAnd the reflection
Light intensity I_rAnd the intensity of transmitted light I_tThe following equation holds between
stand. I_i= I_r + I_t A voltage was applied to the optical deflector 1 to function as a diffraction grating.
In case of transmitted light intensity I _tIs the sum of the intensities of all diffracted light
Therefore, the following equation holds. I_t= (I₀) + (I₊₁) + (I_-1) + (I₊₂) + (I_-2) ＋ …… ＋
(I_{+ n}) + (I_-n) Where I₀Is the intensity of 0th order light, I₊₁Is the intensity of the + 1st order diffracted light
Degree, I_-1Is the intensity of the −1st order diffracted light, I₊₂Is the + 2nd order diffracted light
Strength, I_-2Is the intensity of the −2nd order diffracted light, I_{+ n}Is the + nth order diffracted light
Strength of I_-nIs the intensity of the -nth order diffracted light.

Further, at the incident angle θp where the diffraction efficiency of the + 1st-order diffracted light is maximum, the intensity of the diffracted light other than the + 1st-order diffracted light and the 0th-order diffracted light is so negligible that the following approximate expression holds. I _tp = (I _0p ) + (I _{+ 1p} ), where I _tp , I _0p , and I _{+ 1p} are the total transmitted light intensity, the 0th-order light intensity, and the + 1st-order diffracted light at the incident angle θp, respectively. Strength. From this, the following equation is obtained. I _{+ 1p} = (I _tp ) − (I _0p ) That is, if the intensity I _tp of the total transmitted light and the intensity I _0p of the 0th-order light are known, the intensity I _{+ 1p} of the _{+ 1st-order} diffracted light that is the scanning light can be obtained. it can.

Therefore, the intensity Ic of the scanning light can be made constant by controlling the intensity of the light source so that the intensity I _{+ 1p} of the _{+ 1st order} diffracted light thus obtained becomes constant.

[First Embodiment] Next, a first embodiment of the optical scanning device according to the present invention will be described with reference to the drawings of FIGS. 12 is a block diagram of an optical scanning device in this embodiment, and FIG. 13 is a block diagram of a control system.
4 is a flow chart.

The optical scanning device comprises an optical deflector 1 and a drive circuit 6.
A laser oscillator (light source) 7, a posture control motor (posture changing mechanism) 8, a photodiode (light receiving unit) 9, and a control unit 20. The control unit 20 includes a first memory 21, a second memory 22, a voltage control unit (voltage control unit) 23, an attitude control unit (posture control unit) 24, and a light source control unit (light source control unit) 25. I have it.

The optical deflector 1 is the same as the above-mentioned optical deflector, and when a voltage is applied, parallel stripes functioning as a diffraction grating appear, and the pitch of the parallel stripes changes according to the magnitude of the applied voltage. , The diffraction angle changes. The characteristics of the applied voltage V and the spatial frequency f _s , and the characteristics of the applied voltage V and the diffraction efficiency Ed of the + 1st order diffracted light in this optical deflector 1 are as shown in FIGS. 8 and 9, respectively.

The optical deflector 1 is supported via a rotation mechanism (not shown), and is rotated by the attitude control motor 8 so that the incident angle of the laser light emitted from the laser oscillator 7 can be changed. . In the optical deflector 1, the rotation angle from the reference position is detected by an angle sensor (not shown), and the incident angle θ to the optical deflector is detected by this.

The drive circuit 6 includes the transparent electrodes 2 of the optical deflector 1.
2 is a circuit for applying a voltage whose magnitude changes periodically, and by changing the magnitude of the voltage with time, the deflection angle of the light by the optical deflector 1 is changed, It can be scanned.

The laser oscillator 7 emits S-polarized laser light toward the optical deflector 1. The laser oscillator 7 is capable of adjusting the intensity of emitted light, and the light source controller 2 of the controller 20.
Controlled by 5.

The attitude control motor 8 is a stepping motor, and the attitude control unit 24 of the control unit 20 controls the rotation of the laser light so that the laser light enters the optical deflector 1 at an optimum incident angle.

The photodiode 9 receives the 0th order light of the laser light transmitted through the optical deflector 1 and detects the intensity of the 0th order light. The output signal of the photodiode 9 is controlled. It is input to the light source control unit 25 of the unit 20.

In the first memory 21, as shown in FIG. 15, the magnitude (instantaneous value) V of the voltage applied to the optical deflector 1 is V.
And an incident angle table in which the incident angles θp at which the diffraction efficiency of the + 1st order diffracted light is maximized are stored in association with each other.

In the second memory, as shown in FIG. 16, the intensity I _{i of the} light emitted from the laser oscillator 7, the incident angle θ p, and
Intensity table stored corresponding to the total transmitted light intensity I _tp at an incident angle θp is stored. The contents of these incident angle table and intensity table are obtained in advance by experiments.

The contents of the strength table can be obtained as follows. The voltage applied to the optical deflector 1 is held at 0, and the incident angle θp of the light to the optical deflector 1 and the emission light intensity I _i of the laser oscillator 7 are changed, and the photodiode 9 changes Detect intensity. The intensity of the 0th-order light detected by the photodiode 9 is set as the total transmitted light intensity _Itp .

[Control of Incident Angle] Control of the incident angle is performed as follows. A voltage V, which is controlled by the voltage controller 23 to change its magnitude in a predetermined cycle, is applied to the optical deflector 1 via the drive circuit 6.

The instantaneous value V of the voltage applied to the optical deflector 1 is read by the voltage control unit 23 (step 101), and this instantaneous value V is input from the voltage control unit 23 to the attitude control unit 24.

Then, the incident angle θp corresponding to the instantaneous value V of the voltage applied to the optical deflector 1 is read by referring to the incident angle table of the first memory 21 (step 102), and the voltage controller 23. At, the angle difference between this incident angle θp and the present incident angle θ is calculated (step 103).

Next, the attitude control unit 24 outputs the attitude control motor 8 so that the optical deflector 1 rotates by a predetermined angle (step 10).
Four). As a result, the laser light emitted from the laser oscillator 7 is controlled so as to always enter the optical deflector 1 at the incident angle θp.

[Control of Scanning Light Intensity] The scanning light intensity is controlled as follows. First, the initial value of the emission light intensity I _i of the laser oscillator 7 is set (step 201).

The light source control unit 24 reads out the emission light intensity I _i of the laser oscillator 7 at the present time (step 202), and this emission light intensity I _i is input to the light source control unit 25. The photodiode 9 detects the intensity I _0p of the 0th-order light (step 203), and the intensity I _0p of the 0th-order light is input to the light source controller 25.

The incident angle θp read out in step 102 of the incident angle control is input to the light source control section 25. Then, the incident angle θp, the current emission light intensity I _i and the 0th order light intensity I _0p. The total transmitted light intensity _Itp corresponding to
6 is read out by referring to the intensity table (step 20)
Four).

Further, in the light source control section 25, the difference between the total transmitted light intensity _Itp read out and the intensity I _0p of the 0th order light is calculated, and from this, the intensity of the + 1st order diffracted light which is the intensity of the scanning light at the present time is calculated. Knowing I _{+ 1p} , the difference between the present scanning light intensity I _{+ 1p} and the preset target value Is of the scanning light intensity is calculated (step 205).

When the intensity I _{+ 1p} of the _{+ 1st order} diffracted light obtained by the calculation is larger than the target value Is, the intensity I _i of the light emitted from the laser oscillator 7 is reduced by the light source controller 25. When the intensity I _{+ 1p} of the + 1st-order diffracted light output to the laser oscillator 7 is smaller than the target value Is, the light source controller 25 causes the laser oscillator 7 to increase the intensity I _i of the light emitted from the laser oscillator 7. Output to (step 20
6). In this manner, the intensity Ic (= I _{+ 1p} ) of the scanning light is controlled so as to always be the target value Is.

As described above, in this optical scanning device, the laser light emitted from the laser oscillator 7 always enters the optical deflector 1 at the incident angle θp, and as a result,
The intensity of the diffracted light excluding the scanning light (+ 1st-order diffracted light) and the 0th-order light can be made extremely small. This improves the performance of the optical scanning device.

For example, when the optical scanning device is used as a bar code reader, the −1st order diffracted light or ±
When the intensity of the diffracted light such as the second-order diffracted light is high, the reflected light of the diffracted light other than the scanning light reflected by the bar code may enter the photodetector for reading, and the reading accuracy may deteriorate. This is not the case with the optical scanning device of the present invention.

Further, in this scanning device, the intensity of the scanning light can always be made constant, which also improves the performance of the optical scanning device. For example, when the optical scanning device is used for a bar code reader, the reflected light of the scanning light reflected by the bar code is always incident on the photodetector for reading with a constant intensity, so that a reading error is eliminated. The reading accuracy is improved.

[Scanning Speed of Scanning Light] The scanning speed of scanning light is determined by the temporal change rate of the voltage V applied to the optical deflector 1. Consider this.

The wavelength λ of the incident light entering the optical deflector 1,
The diffraction angle α (see FIG. 11) of the + 1st-order diffracted light when incident at the incident angle θp and the spatial frequency f _s have the following relationship. sinθp + sinα = whereas f _s · lambda, a spatial frequency f _s of parallel fringes generated voltage V and the light deflector 1 to be applied to the optical deflector 1 has a linear relationship, f _s =
Since it can be expressed as BV (B is a constant), the previous equation is as follows. sin θp + sin α = BVλ Here, since Bλ is a constant, if it is replaced with Bλ = K, sin θp + sin α = KV Therefore, when the diffraction angle α of the + 1st order diffracted light is represented by the applied voltage V and the incident angle θp, α = sin ⁻¹ {KV− sin θp} ... (1) Since the diffraction angle of the + 1st order diffracted light is the deflection angle of the scanning light, the temporal change of the deflection angle α of the scanning light given by the above equation (1) should be constant. When the voltage control unit 23 controls the voltage value applied to the optical deflector 1, the scanning speed of the scanning light can be made constant.

FIG. 17 shows the distance from the starting point to the scanning point and the intensity Ic of the scanning light when the applied voltage is controlled in this way.
The relationship with and is expressed as time on the horizontal axis.

[Second Embodiment] Next, a second embodiment of the optical scanning device according to the present invention will be described with reference to the drawings of FIGS. FIG. 18 is a block diagram of a control system in the second embodiment, FIG. 19 is a flowchart, and FIG. 20 is a diagram showing a strength table.

The overall structure of the optical scanning device of the second embodiment, and the incident angle table (the magnitude V of the voltage applied to the optical deflector 1 and the diffraction efficiency of the + 1st order diffracted light) stored in the first memory 21. The table in which the incident angle .theta.p that maximizes .gamma. Is associated is the same as that in the first embodiment, so FIGS. 12 and 15 are referred to for these.

The difference between the optical scanning device of the second embodiment and that of the first embodiment will be described below. In the second memory 22 in the second embodiment, as shown in FIG. 20, the intensity I _i of the emitted light of the laser oscillator 7, the magnitude (instantaneous value) V of the voltage applied to the optical deflector 1, This instantaneous value V is the optical deflector 1
An intensity table is stored in which the total transmitted light intensity _Itp when applied to is stored correspondingly. That is, this intensity table is the incident angle θp of the intensity table in the first embodiment.
, The instantaneous value V of the applied voltage corresponding to each incident angle θp
Is stored. The contents of the strength table are obtained in advance by experiments in the same manner as in the case of the first embodiment.

In the second embodiment, when the instantaneous value V of the voltage applied to the optical deflector 1 is read by the voltage controller 23, the instantaneous value V is changed from the voltage controller 23 to the attitude controller 24 and the light source controller 25. (See FIG. 18).

[Control of Incident Angle] The control of the incident angle is shown in FIG.
Step 101, Step 102, Step 103, Step 1
The laser beam emitted from the laser oscillator 7 is controlled so as to always enter the optical deflector 1 at the incident angle θp. Since steps 101 to 104 are the same as those in the first embodiment, the description thereof will be omitted.

[Control of Scanning Light Intensity] In the second embodiment, the scanning light intensity is controlled as follows. First, the initial value of the emission light intensity I _i of the laser oscillator 7 is set (step 201).

The emission light intensity I _i of the laser oscillator 7 at the present time is read by the light source control unit 25 (step 202), and this emission light intensity I _i is input to the light source control unit 25. The photodiode 9 detects the intensity I _0p of the 0th-order light (step 203), and the intensity I _0p of the 0th-order light is input to the light source controller 25.

In the control of the incident angle, the instantaneous value V of the applied voltage to the optical deflector 1 read in step 101 is input to the light source controller 25. Then, the instantaneous value V of these applied voltages, the intensity I _i of the emitted light at the present time, and the intensity I _{0p of the} 0th-order light.
The total transmitted light intensity _Itp corresponding to is read with reference to the intensity table of FIG. 20 (step 214).

The subsequent steps are the same as in the case of the first embodiment. That is, in the light source control unit 25, the difference between the total transmitted light intensity is read I _tp and 0-order light intensity I _0p is calculated, which is now the intensity of the scanning light current order diffracted light intensity I _{+ 1p} Then, the difference between the present scanning light intensity I _{+ 1p} and the preset target value Is of the scanning light intensity is calculated (step 205).

When the intensity I _{+ 1p} of the _{+ 1st order} diffracted light obtained by the calculation is larger than the target value Is, the intensity I _i of the light emitted from the laser oscillator 7 is reduced by the light source controller 25. When the intensity I _{+ 1p} of the + 1st-order diffracted light output to the laser oscillator 7 is smaller than the target value Is, the light source controller 25 causes the laser oscillator 7 to increase the intensity I _i of the light emitted from the laser oscillator 7. Output to (step 20
6). In this manner, the intensity Ic (= I _{+ 1p} ) of the scanning light is controlled so as to always be the target value Is.

Also according to the optical scanning device of the second embodiment,
The laser light emitted from the laser oscillator 7 is always incident on the optical deflector 1 at the incident angle θp, and the intensity Ic of the scanning light can be kept constant, so that the performance of the optical scanning device is improved.

In the second embodiment, the instantaneous value V of the applied voltage to the optical deflector (1) is input to the light source controller (25), and the intensity table is immediately referred to determine the total transmitted light intensity _Itp. Therefore, the processing speed becomes faster than that of the first embodiment.

[0081]

As described above, according to the present invention,
By including the optical deflector, the light source, the voltage control means, the attitude changing mechanism, and the attitude control means, the incident angle of the incident light entering the optical deflector is always kept and the diffraction efficiency of the scanning light is maximized. Angle of incidence that results in
The excellent effect that the diffracted light other than the scanning light does not interfere with the scanning light and the performance of the optical scanning device is improved is achieved.

Further, when the light receiving section and the light source control means are added, the excellent effect that the intensity of the scanning light can be always kept constant is exhibited.

[Brief description of drawings]

FIG. 1 is a block diagram of the present invention.

FIG. 2 is a block diagram of the present invention.

FIG. 3 is a basic configuration diagram of an optical deflector used in the optical scanning device of the present invention.

FIG. 4 is a principle diagram of the most basic optical scanning device.

FIG. 5 is a principle diagram of the most basic optical scanning device.

FIG. 6 is a diagram showing a scanning state of the optical scanning device.

FIG. 7 is a diagram showing an example of a voltage waveform applied to an optical deflector.

FIG. 8 is a characteristic diagram of an applied voltage and a spatial frequency.

FIG. 9 is a characteristic diagram of applied voltage and diffraction efficiency of + 1st order diffracted light.

FIG. 10 is a characteristic diagram of incident angle and diffraction efficiency.

FIG. 11 is a diagram showing an incident angle and a state of diffracted light.

FIG. 12 is a configuration diagram of an optical scanning device according to a first embodiment of the present invention.

FIG. 13 is a block diagram of a control system in the first embodiment of the optical scanning device according to the present invention.

FIG. 14 is a flowchart in the first embodiment of the optical scanning device according to the present invention.

FIG. 15 is a diagram showing an incident angle table in the first embodiment of the optical scanning device according to the present invention.

FIG. 16 is a diagram showing an intensity table in the first embodiment of the optical scanning device according to the present invention.

FIG. 17 is a diagram showing the distance from the starting point to the scanning point and the intensity of the scanning light.

FIG. 18 is a block diagram of a control system in a second embodiment of the optical scanning device according to the present invention.

FIG. 19 is a flowchart in a second embodiment of the optical scanning device according to the present invention.

FIG. 20 is a diagram showing an intensity table in a second embodiment of the optical scanning device according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Optical deflector 2 Transparent electrode 5 Liquid crystal 6 Drive circuit 7 Laser oscillator (light source) 8 Attitude control motor (attitude variable mechanism) 9 Photodiode (light receiving part) 21 First memory (incident angle table) 22 Second memory (intensity table) ) 23 voltage control section (voltage control means) 24 attitude control section (posture control means) 25 light source control section (light source control means)

Claims (4)

[Claims] 1. (a) A liquid crystal (5) is inserted between transparent electrodes (2, 2) arranged facing each other, and when a voltage is applied between the transparent electrodes (2, 2), the parallel electrodes function as a diffraction grating. The stripe is the liquid crystal
An optical deflector (1) that occurs in (5) and in which the pitch of the parallel stripes changes according to the magnitude of the applied voltage, and (b) a light source that emits light toward the optical deflector (1) ( 7), and (c) voltage control means (23) for controlling the voltage applied to the optical deflector (1).
(D) A posture changing mechanism (8) for changing the posture of the light deflector (1) so as to change the incident angle of the light of the light source (7) with respect to the light deflector (1), and (e) the light Based on the magnitude of the voltage applied to the deflector (1), the incident angle of the incident light incident on the optical deflector (1), the attitude so that the incident angle that maximizes the diffraction efficiency of the scanning light Attitude control means (2 for controlling the variable mechanism (8)
4) and, wherein the light emitted from the light source (7) is deflected by the light deflector (1) to be scanning light. 2. The optical scanning device according to claim 1,
The incident angle that maximizes the diffraction efficiency of scanning light is the optical deflector (1).
An optical scanning device characterized in that it is determined by referring to an incident angle table (21) stored corresponding to the instantaneous value of the voltage applied to the. 3. The optical scanning device according to claim 1, wherein (f) a light receiving section (9) for detecting the intensity of 0th-order light transmitted through the optical deflector (1), and (g) the The intensity of the light source (7) is adjusted so that the intensity of the scanning light becomes constant based on the intensity of the 0th-order light detected by the light receiving section (9) and the intensity of the total transmitted light transmitted through the optical deflector (1). And a light source control means (25) for controlling the optical scanning device. 4. The optical scanning device according to claim 3,
Refer to the intensity table (22) in which the intensity of the total transmitted light is stored in correspondence with the intensity of the light source (7) and the instantaneous value of the voltage applied to the optical deflector (1) or the incident angle corresponding to this. An optical scanning device characterized by being determined by.