Acousto-optical light deflector, light irradiation device, additive manufacturing device, light beam deflection method, light beam irradiation method, and processing method

Abstract

This acousto-optical light deflector has a first acousto-optical element (100a) and a second acousto-optical element (100b) that are disposed along the optical path of a light beam (LB). The first acousto-optical element includes a first optical element (10a) and a first transducer (20a) for generating an ultrasonic wave (21a) in the first optical element. The second acousto-optical element includes a second optical element (10b) and a second transducer (20b) for generating an ultrasonic wave (21b) in the second optical element. The first transducer and the second transducer are provided so as to sandwich the optical path of the light beam therebetween. The propagation direction of the ultrasonic wave traveling in the second optical element is inclined with respect to the propagation direction of the ultrasonic wave traveling in the first optical element.

Description

Acousto-optic light deflector, light irradiation device, additive manufacturing device, light beam deflection method, light beam irradiation method, and processing method

[0001] The present disclosure relates to an acousto-optical light deflector, a light irradiation device, an additive manufacturing device, a light beam deflection method, a light beam irradiation method, and a processing method.

[0002] An example of an acousto-optical light deflector that deflects a light beam using the acousto-optical effect is described in Patent Document 1.

[0003] U.S. Patent No. 6,665,112

[0004] In such an acousto-optical deflector, it is desirable to appropriately deflect the light beam.

[0005] An acousto-optical deflector according to one aspect of the present disclosure is an acousto-optical deflector having a first acousto-optical element and a second acousto-optical element arranged along the optical path of a light beam, wherein the first acousto-optical element includes a first optical element and a first transducer that generates ultrasonic waves within the first optical element, and the second acousto-optical element includes a second optical element and a second transducer that generates ultrasonic waves within the second optical element, the first transducer and the second transducer being arranged on either side of the optical path of the light beam, and the propagation direction of the ultrasonic waves traveling within the second optical element being inclined relative to the propagation direction of the ultrasonic waves traveling within the first optical element.

[0006] A light irradiation device according to one aspect of the present disclosure is a light irradiation device that irradiates a light beam onto an object, and includes an acousto-optical light deflector and a control device that controls the acousto-optical light deflector to change the irradiation position of the light beam relative to the light irradiation device.

[0007] An additive manufacturing apparatus according to one aspect of the present disclosure includes the light irradiation device and a material supply device that supplies material to the object.

[0008] An optical beam deflection method according to one aspect of the present disclosure includes: making an optical beam from a light source incident on a first acousto-optical element including a first optical element and a first transducer that generates ultrasonic waves within the first optical element; making the optical beam from the first acousto-optical element incident on a second acousto-optical element including a second optical element and a second transducer that generates ultrasonic waves within the second optical element; generating the ultrasonic waves in a first propagation direction within the first optical element by the first transducer; and generating the ultrasonic waves in a second propagation direction within the second optical element by the second transducer, wherein the second propagation direction is inclined with respect to the first propagation direction; and wherein the first transducer generates the ultrasonic waves from a first side with respect to an optical path of the optical beam, and the second transducer generates the ultrasonic waves from a second side with respect to the optical path of the optical beam that is opposite to the first side.

[0009] A light beam irradiation method according to one aspect of the present disclosure includes irradiating a light beam onto an object, and using the light beam deflection method to change the irradiation position of the light beam irradiated onto the object.

[0010] A processing method according to one aspect of the present disclosure includes irradiating the object with the light beam using the light beam irradiation method, and supplying material to the object.

[0011] FIG. 1A is a schematic diagram of an acousto-optical deflector 100r that operates using a random access method. FIG. 1B is a schematic diagram of an acousto-optical deflector 100s that operates using a scan method. It is a diagram for explaining the cylindrical effect. It is a diagram for explaining the properties of the cylindrical effect due to the difference between the positive and negative orders of diffracted light. It is a schematic diagram showing an acousto-optical deflector 100 according to a first embodiment. It is a diagram for explaining the angular relationship between the ultrasonic plane and incident light, and the positional relationship between the first acousto-optical element 100a and the second acousto-optical element 100b. It is an example of a graph showing that the deflection angle of the light beam LB in the acousto-optical deflector 100 according to the first embodiment is twice as large as that of either the first acousto-optical element 100a or the second acousto-optical element 100b. 1 is an example of a graph showing that by dividing the deflection angle obtained by either the first acousto-optic element 100a or the second acousto-optic element 100b between the first acousto-optic element 100a and the second acousto-optic element 100b, the deflection angles of the first acousto-optic element 100a and the second acousto-optic element 100b can be reduced to approximately half of the deflection angle of either the first acousto-optic element 100a or the second acousto-optic element 100b.

[0023] FIG. 1 is a schematic diagram of an acousto-optic optical deflector 100c configured by arranging two transducers 20a, 20b in a single optical element 10c, substantially facing each other across the optical path of the light beam LB.

[0024] FIG. 2 is a diagram summarizing the differences between the comparative example and the first embodiment.

[0025] FIG. 3 is a schematic diagram of an acousto-optic optical deflector 100d according to a second embodiment.

[0026] FIG. 4 is a schematic diagram of an acousto-optic optical deflector 100e according to a third embodiment. Fig. 1 is a schematic configuration diagram of an acousto-optical light deflector 100f according to embodiment 4. Fig. 2 is a schematic configuration diagram of an acousto-optical light deflector 100g according to embodiment 5. Fig. 3 is a diagram schematically showing the configuration of an additive manufacturing apparatus 1x. Fig. 4 is a flowchart showing a method for processing an object 110x. Fig. 5 is a flowchart showing a light beam deflection method.

[0012] An acousto-optical deflector according to the present embodiment will be described below with reference to the drawings. Note that the embodiment described below shows an example of how the present disclosure is implemented, and the present disclosure is not limited to the specific configuration described below. When implementing the present disclosure, a specific configuration according to the embodiment may be appropriately adopted. Note that the same reference numerals throughout the drawings indicate the same or corresponding parts, and their description may be omitted.

[0013] (Comparative Example) First, before describing the acousto-optic deflector (AOD) according to this embodiment, an acousto-optic deflector according to a comparative example will be described. Figures 1A and 1B are schematic configuration diagrams showing acousto-optic deflectors 100r and 100s according to the comparative examples, respectively. Figure 1A shows the acousto-optic deflector 100r that operates using a random access method, and Figure 1B shows the acousto-optic deflector 100s that operates using a scan method.

[0014] The acousto-optic deflector 100r shown in FIG. 1A includes an optical element 10, a transducer 20 that generates ultrasonic waves 21 within the optical element 10, and a driving circuit 30 that drives the transducer 20 by supplying an RF (radio frequency) signal to the transducer 20. The transducer 20 is attached to the optical element 10, which is made of an acousto-optic material such as tellurium dioxide (TeO), lead molybdate (PbMoO), or quartz crystal, or tellurite glass. The RF signal from the driving circuit 30 causes the transducer 20 to generate ultrasonic waves 21. The acousto-optic deflector 100r is an optically active element that generates a refractive index lattice within the optical element 10 by inputting an RF signal to the transducer 20, which generates a diffraction phenomenon through interaction with an incident light beam LB, and can deflect the light beam LB by sweeping the frequency of the RF signal to slightly change the diffraction angle. The modulator 200 controls ON / OFF of the light beam LB. The modulator 200 turns off the light beam LB until the ultrasonic waves 21 fill the light beam LB.

[0015] 1A, the driving circuit 30 randomly changes the frequency of the ultrasonic waves 21 generated within the optical element 10 to an arbitrary constant value (see the graph at the bottom right of FIG. 1A). This allows the light beam LB to be stationary at a position according to the value of the frequency of the ultrasonic waves 21 (see the diagram at the bottom left of FIG. 1A).

[0016] The scanning type acousto-optical deflector 100s shown in Fig. 1(B) further includes a cylindrical lens 40 arranged on the side where the light beam LB enters the acousto-optical deflector 100s. In the scanning type shown in Fig. 1(B), the driving circuit 30 drives the transducer 20 so as to change the frequency of the ultrasonic waves 21 generated within the optical element 10 (see the graph at the bottom left of Fig. 1(B)). This allows the light beam LB to be scanned as the frequency is swept.

[0017] The frequency gradient that occurs during frequency sweeping generates a gradient in the refractive index grating period within the optical element 10. Since this gradient in the refractive index grating period exists in the light beam LB that passes through the optical element 10, when the frequency is increased (decreased) to deflect the light beam, a so-called "cylindrical effect" occurs, in which the light beam LB emitted from the optical element 10 spreads or converges only in the sweep direction. For this reason, in the scanning-type acousto-optical deflector 100s, in order to prevent this cylindrical effect, a cylindrical lens 40 having a power (focal length) that cancels the cylindrical effect is disposed on the side where the light beam LB enters or exits the acousto-optical deflector 100s. This makes it possible to prevent the light beam LB from spreading or converging.

[0018] FIG. 2 is a diagram illustrating the cylindrical effect. The acousto-optical deflector 100s′ shown in FIG. 2 is the scanning-type acousto-optical deflector 100s shown in FIG. 1B without the cylindrical lens 40. In the acousto-optical deflector 100s′, ultrasonic waves 21 of different frequencies are present within the optical element 10. Therefore, deflection of the light beam LB causes a phenomenon known as the cylindrical effect, in which the light beam LB converges or diverges only in one axial direction. As a result, the beam shape of the light beam LB becomes elliptical. The ellipticity increases with increasing distance from the acousto-optical deflector 100s′.

[0019] In a random access system in which the frequency of the ultrasonic waves 21 is instantaneously switched, the frequency remains constant except when the frequency is switched, and therefore the cylindrical effect does not occur. However, in a scan system in which the frequency of the ultrasonic waves 21 is increased (decreased) to deflect the light beam LB, the cylindrical effect occurs. For this reason, the scan-type acousto-optical deflector 100s employs a cylindrical lens 40 to suppress the cylindrical effect. Because the cylindrical lens 40 has a fixed focal length, it can effectively prevent the cylindrical effect when the sweep frequency range, increase / decrease direction, and sweep rate of the RF signal are kept constant. However, to effectively prevent the cylindrical effect, none of the sweep frequency range, increase / decrease direction, or sweep rate can be changed. As a result, the deflection range, deflection direction, and deflection rate of the light beam LB cannot be changed, and the scan-type acousto-optical deflector 100s cannot be operated in a random access system. Therefore, there are separate acousto-optical deflectors 100r dedicated to the random access method and acousto-optical deflectors 100s dedicated to the scanning method, and in the comparative example, it is not possible to perform both random access and beam scanning with a single acousto-optical deflector.

[0020] Therefore, in this embodiment, an acousto-optical light deflector is provided that can freely change the deflection range, deflection direction and deflection speed of the light beam LB, and can also stop the light beam LB.

[0021] First Embodiment Before describing the acousto-optical deflector 100 according to the first embodiment, the nature of the cylindrical effect due to the difference between the positive and negative orders of diffracted light will be described with reference to Fig. 3. In the following description, the modulator 200 will be omitted for the sake of simplicity, but this does not mean that the modulator 200 is unnecessary.

[0022] The acousto-optical deflector shown on the left side of FIG. 3 is the same as the acousto-optical deflector 100s' shown in FIG. 2, and the driving method of the transducer 20 is also the same as in FIG. 2. As shown on the left side of FIG. 3, when +1st-order diffracted light of the light beam LB due to Bragg diffraction is used, the diffracted light becomes an ellipse with its major axis in the diffraction direction. On the other hand, as shown on the right side of FIG. 3, when the transducer 20a is provided below the optical element 10 and the traveling direction of the ultrasonic waves 21 is reversed from that in the left side of FIG. 3, the optical element 10 of the acousto-optical deflector 100s'' generates -1st-order diffracted light of the light beam LB due to Bragg diffraction. When -1st-order diffracted light is used, the diffracted light becomes an ellipse with its minor axis in the diffraction direction. In this way, when +1st-order diffracted light due to Bragg diffraction is used and when -1st-order diffracted light is used, the deflection amount and deflection direction are the same and the amount of cylindrical effect is also the same, but the cylindrical effect is different. The direction of the cylindrical effect is reversed. The inventors discovered that by skillfully combining these two, the cylindrical effect can be canceled. Furthermore, the light deflection utilizes the fact that the refractive index sparse / dense diffraction grating generated in the optical element 10 by the ultrasonic waves 21 deviates from the Bragg angle (Bragg condition) for the incident light beam LB. Therefore, if the light beam LB is deflected significantly, the Bragg condition is significantly deviated from and the diffraction efficiency decreases. Therefore, if the light deflection angle is small and the frequency range is limited so as not to deviate significantly from the Bragg angle, the diffraction efficiency can be increased.

[0023] 4 is a schematic diagram showing an acousto-optical deflector 100 according to the first embodiment. The acousto-optical deflector 100 according to this embodiment includes a first acousto-optical element 100a and a second acousto-optical element 100b arranged along the optical path of the light beam LB. In the acousto-optical deflector 100 according to this embodiment, the first acousto-optical element 100a and the second acousto-optical element 100b are arranged in this order along the traveling direction of the light beam LB. The first acousto-optical element 100a includes a first optical element 10a and a first transducer 20a that generates an ultrasonic wave 21a within the first optical element 10a. The second acousto-optical element 100b includes a second optical element 10b and a second transducer 20b that generates an ultrasonic wave 21b within the second optical element 10b. Here, the acousto-optic material of the first optical element 10a of the first acousto-optic device 100a and the acousto-optic material of the second optical element 10b of the second acousto-optic device 100b are the same material. The acousto-optic deflector 100 according to this embodiment also includes a drive circuit 30 that drives the first transducer 20a and the second transducer 20b so as to change the frequencies of the ultrasonic waves 21a and 21b generated within the first optical element 10a and the second optical element 10b when the light beam LB passes through them. The drive circuit 30 drives the first and second transducers 20a and 20b, but this is not a limitation, and a separate drive circuit 30 may be provided for each transducer.

[0024] In the acousto-optical deflector 100 according to this embodiment, the drive circuit 30 drives the first transducer 20 a and the second transducer 20 b simultaneously at the same sweep frequency. This allows the first transducer 20 a and the second transducer 20 b to be connected to the same drive circuit 30, making it possible to provide an acousto-optical deflector 100 that can cancel the cylindrical effect with a simple configuration.

[0025] In addition, when the sweep frequency of the ultrasonic waves 21a emitted by the first transducer 20a is f1, the sweep frequency of the ultrasonic waves 21b emitted by the second transducer 20b is f2, and the sweep time of the first transducer 20a and the second transducer 20b is t, the drive circuit 30 may drive the first transducer 20a and the second transducer 20b so as to satisfy the following conditional expression (1): df1 / dt=df2 / dt (1)

[0026] In this way, the driving circuit 30 can cancel the cylindrical effect even if the first transducer 20a and the second transducer 20b are not driven simultaneously at the same sweep frequency, as long as the time change rate of the sweep frequency is the same.

[0027] The first transducer 20 a and the second transducer 20 b are arranged to sandwich the optical path of the light beam LB. The second acousto-optic device 100 b is arranged at an angle with respect to the first acousto-optic device 100 a so that the propagation direction of the ultrasonic wave 21 b traveling through the second optical device 10 b is inclined with respect to the propagation direction of the ultrasonic wave 21 a traveling through the first optical device 10 a.

[0028] Furthermore, the first acousto-optic element 100a and the second acousto-optic element 100b are arranged so that the axis along the propagation direction of the ultrasonic wave 21a emitted by the first transducer 20a and the axis along the propagation direction of the ultrasonic wave 21b emitted by the second transducer 20b are in the same plane.

[0029] Since the acousto-optical deflector 100 according to this embodiment has two stages of acousto-optic elements 100a and 100b, the light beam LB incident on the first acousto-optic element 100a is diffracted by the first acousto-optic element 100a, and the light beam LB diffracted by the first acousto-optic element 100a is diffracted by the second acousto-optic element 100b. More specifically, the first acousto-optic element 100a generates a −1st-order diffracted light of the incident light beam LB, and the second acousto-optic element 100b generates a +1st-order diffracted light of the light beam LB from the first acousto-optic element 100a.

[0030] As described above, in the acousto-optic deflector 100 according to this embodiment, the first acousto-optic element 100a uses −1st-order diffracted light of the light beam LB due to Bragg diffraction. The second acousto-optic element 100b is disposed at an angle with respect to the first acousto-optic element 100a so that the propagation direction of the ultrasonic waves 21b generated by the second transducer 20b in the second acousto-optic element 100b and the propagation direction of the ultrasonic waves 21a generated by the first transducer 20a in the first acousto-optic element 100a are substantially parallel (excluding parallelism in the strict sense). By disposing the second acousto-optic element 100b at an angle with respect to the first acousto-optic element 100a in this manner, the second acousto-optic element 100b uses +1st-order diffracted light of the light beam LB due to Bragg diffraction.

[0031] FIG. 5 is a diagram illustrating the angular relationship between the ultrasonic wave plane and the incident light, and the positional relationship between the first acousto-optic element 100a and the second acousto-optic element 100b. Note that the driving circuit 30 is omitted from FIG. 5 . In FIG. 5 , La denotes the incident ray of the light beam LB incident on the acousto-optic deflector 100, and indicates the optical axis at the center frequency of the sweep frequency of the ultrasonic waves 21a oscillated by the first transducer 20a. Lb denotes the tilt of the ultrasonic wave plane of the ultrasonic waves 21a traveling within the first optical element 10a. Lc denotes the exit ray of the light beam LB emitted from the first acousto-optic element 100a, and indicates the incident ray of the light beam LB incident on the second acousto-optic element 100b. Ld denotes the tilt of the ultrasonic wave plane of the ultrasonic waves 21b traveling within the second optical element 10b. Le is the emission ray of the light beam LB emitted from the second acousto-optic element 100b. θ1 is the Bragg angle at the center frequency of the sweep frequency f1 of the ultrasonic waves 21a oscillated by the first transducer 20a. θ2 is the Bragg angle at the center frequency of the sweep frequency f2 of the ultrasonic waves 21b oscillated by the second transducer 20b. The ultrasonic plane Lb in the first optical element 10a is inclined by θ1 with respect to the incident light beam La. Furthermore, the ultrasonic plane Ld in the second optical element 10b is inclined by 2θ1 + θ2 with respect to the incident light beam La. The propagation directions of the ultrasonic waves 21a traveling within the first optical element 10a and the ultrasonic waves 21b traveling within the second optical element 10b are approximately opposite to each other, and the ultrasonic plane Ld is inclined by θ1 + θ2 with respect to the ultrasonic plane Lb. That is, the second acousto-optic device 100b is disposed at an angle θ1+θ2 with respect to the first acousto-optic device 100a.

[0032] With the above configuration, the cylindrical effect generated in the light beam LB due to interaction with the ultrasonic waves 21 a from the first transducer 20 a can be canceled by interaction with the ultrasonic waves 21 b from the second transducer 20 b, and with the cylindrical effect canceled, the deflection range, deflection direction, and deflection speed of the light beam LB can be freely changed. Note that, in anticipation of the cylindrical effect generated in the second acousto-optic device 100 b, the first acousto-optic device 100 a can also be considered to function as a cylindrical lens.

[0033] In the acousto-optical deflector 100 according to this embodiment, the deflection angle of the light beam LB is the sum of the deflection angles obtained by the first acousto-optical element 100 a or the second acousto-optical element 100 b. Therefore, compared to when using either the first acousto-optical element 100 a or the second acousto-optical element 100 b, the acousto-optical deflector 100 according to this embodiment can approximately double the deflection angle of the light beam LB while suppressing the occurrence of the cylindrical effect.

[0034] On the other hand, because the first acousto-optic element 100 a and the second acousto-optic element 100 b both deflect the light beam LB in the same direction, if the deflection angle obtained by either the first acousto-optic element 100 a or the second acousto-optic element 100 b is shared between the first acousto-optic element 100 a and the second acousto-optic element 100 b, the deflection angles of the first acousto-optic element 100 a and the second acousto-optic element 100 b can be made approximately half of the deflection angle of either one of the acousto-optic elements, thereby reducing the amount of deviation from the respective Bragg angles and suppressing a decrease in the diffraction efficiency of the acousto-optic deflector 100. Therefore, the acousto-optic deflector 100 according to this embodiment can deflect a light beam while suppressing the occurrence of the cylindrical effect and maintaining high diffraction efficiency.

[0035] FIG. 6 is an example of a graph showing that the acousto-optical light deflector 100 according to this embodiment has a deflection angle of the light beam LB that is twice as large as that of either the first acousto-optical element 100a or the second acousto-optical element 100b.

[0036] FIG. 7 is an example of a graph showing that by sharing the deflection angle obtained by either the first acousto-optic element 100a or the second acousto-optic element 100b between the first acousto-optic element 100a and the second acousto-optic element 100b, the deflection angles of the first acousto-optic element 100a and the second acousto-optic element 100b can be reduced to approximately half of the deflection angle of either the first acousto-optic element 100a or the second acousto-optic element 100b.

[0037] 6 and 7, the horizontal axis represents elapsed time (μsec), and the vertical axis represents sweep frequency (MHz) (left) or deflection angle (°) (right). In each graph, Gf represents the transducer sweep frequency (MHz) versus time, Ga represents the deflection angle (°) versus time, and Ge represents the beam divergence angle (°) of the light beam LB versus time.

[0038] The graph on the left side of Figure 6 shows the case of either the first acousto-optical device 100a or the second acousto-optical device 100b. The transducer frequency is swept from approximately 80 MHz to approximately 120 MHz in approximately 60 μs, during which the light beam LB is deflected by approximately 2°. However, the light beam LB emitted from the acousto-optical device has a beam divergence angle of approximately 0.3°, which indicates a cylindrical effect.

[0039] The graph on the right side of FIG. 6 shows the case of the acousto-optic deflector 100 according to this embodiment. As with the graph on the left side of FIG. 6, the transducer frequency is swept from approximately 80 MHz to approximately 120 MHz in approximately 60 μs. During this time, the acousto-optic deflector 100 according to this embodiment can deflect the light beam LB by approximately 4°. In other words, compared to either the first acousto-optic element 100a or the second acousto-optic element 100b, the acousto-optic deflector 100 according to this embodiment has a deflection angle that is twice as large. Furthermore, the emitted light beam LB has a beam divergence angle of 0°, thereby canceling the cylindrical effect.

[0040] The graph on the left side of Figure 7 shows the case where the frequency sweep width of the transducer of either the first acousto-optic device 100a or the second acousto-optic device 100b is reduced and swept from approximately 80 MHz to approximately 100 MHz in approximately 60 μs. During this sweep, either the first acousto-optic device 100a or the second acousto-optic device 100b can deflect the light beam LB by approximately 1°. However, the emitted light beam LB has a beam divergence angle of approximately 0.15°, which indicates a cylindrical effect.

[0041] The graph on the right side of Fig. 7 is a graph showing the case where the transducer frequency is swept from about 80 MHz to about 100 MHz in about 60 μs in the acousto-optical deflector 100 according to this embodiment, similar to the graph on the left side of Fig. 7. With a frequency sweep width (20 MHz = 100 MHz - 80 MHz) that is half the frequency sweep width (40 MHz = 120 MHz - 80 MHz) in Fig. 6, the light beam LB can be deflected by about 2°, similar to the case of Fig. 6. The emitted light beam LB has a beam divergence angle of 0°, and the cylindrical effect is canceled.

[0042] In the acousto-optical deflector 100 according to this embodiment, the first optical element 10a and the second optical element 10b are separate elements. However, the first optical element 10a and the second optical element 10b may be integrated. That is, the first transducer 20a and the second transducer 20b may be disposed substantially opposite each other on one optical element 10c (e.g., one crystal) with the optical path of the light beam LB interposed therebetween. FIG. 8 is a schematic diagram of an acousto-optical deflector 100c configured by disposing two transducers 20a and 20b substantially opposite each other on one optical element 10c with the optical path of the light beam LB interposed therebetween. As shown in FIG. 8, such an acousto-optical deflector 100c can be realized with a simple configuration because the two acousto-optical elements 100a and 100b can be configured using a single optical element.

[0043] In the acousto-optical deflector 100 according to this embodiment, the first acousto-optical element 100a generates −1st-order diffracted light, and the second acousto-optical element 100b generates +1st-order diffracted light. However, the first acousto-optical element 100a may generate +1st-order diffracted light, and the second acousto-optical element 100b may generate −1st-order diffracted light. Furthermore, the cylindrical effect can be canceled not only by using ±1st-order diffracted light, but also by using the first acousto-optical element 100a to generate nth-order diffracted light and the second acousto-optical element 100b to generate −nth-order diffracted light. Here, n is an integer other than 0. However, using ±1 as the value of n, i.e., ±1st-order diffracted light, is preferable because it can achieve higher diffraction efficiency.

[0044] Although only the scanning method for sweeping the frequency has been described in this embodiment, the acousto-optical deflector 100 according to this embodiment can also be driven by a random access method. In this case, unlike the acousto-optical deflector 100r according to the comparative example, there is no need to instantaneously change the frequency to an arbitrary value. Instead, the frequency can be changed at high speed to move the light beam LB to the target position at high speed, and the light beam LB can be stopped at that position. This is because the cylindrical effect can be canceled in the acousto-optical deflector 100 according to this embodiment.

[0045] The differences between the comparative example and this embodiment are summarized in FIG. 9 . In the comparative example, different acousto-optical deflectors were required depending on the drive method. That is, an acousto-optical deflector 100r dedicated to the random access method and an acousto-optical deflector 100s dedicated to the scan method were required. When the acousto-optical deflector 100r dedicated to the random access method is driven by the scan method, a cylindrical effect occurs. Similarly, when the acousto-optical deflector 100s dedicated to the scan method is driven by the random access method, a cylindrical effect occurs. Furthermore, the acousto-optical deflector 100s dedicated to the scan method cannot change the deflection range, deflection direction, or deflection speed of the light beam LB.

[0046] On the other hand, the acousto-optical deflector 100 according to this embodiment can be driven by both the random access method and the scan method. Furthermore, the acousto-optical deflector 100 according to this embodiment can deflect the light beam LB by increasing the sweep frequency of the transducer, and can deflect the light beam LB in the opposite direction by decreasing the frequency. The deflection range, deflection direction, and deflection speed of the light beam LB can be freely changed without generating a cylindrical effect, except for a moment when the sweep frequency of the transducer is switched, and the light beam LB can also be accelerated, decelerated, and stopped.

[0047] Second Embodiment Next, an acousto-optical deflector 100d according to a second embodiment will be described with reference to Fig. 10. Fig. 10 is a schematic diagram of the acousto-optical deflector 100d according to this embodiment.

[0048] The acousto-optical deflector 100d according to this embodiment, like the acousto-optical deflector 100 according to the first embodiment, includes a first acousto-optical element 100a and a second acousto-optical element 100b arranged along the optical path of the light beam LB, with the first acousto-optical element 100a and the second acousto-optical element 100b arranged in this order along the traveling direction of the light beam LB. The first acousto-optical element 100a includes a first optical element 10a and a first transducer 20a that generates an ultrasonic wave 21a within the first optical element 10a. The second acousto-optical element 100b includes a second optical element 10b and a second transducer 20b that generates an ultrasonic wave 21b within the second optical element 10b. The acousto-optical deflector 100d according to this embodiment also includes a drive circuit 30 that drives the first transducer 20a and the second transducer 20b so as to change the frequencies of the ultrasonic waves 21a and 21b generated within the first optical element 10a and the second optical element 10b when the light beam LB passes through the first optical element 10a and the second optical element 10b.

[0049] The first transducer 20 a and the second transducer 20 b are arranged to sandwich the optical path of the light beam LB. The second acousto-optic device 100 b is arranged at an angle with respect to the first acousto-optic device 100 a so that the propagation direction of the ultrasonic wave 21 b traveling through the second optical device 10 b is inclined with respect to the propagation direction of the ultrasonic wave 21 a traveling through the first optical device 10 a.

[0050] Furthermore, the first acousto-optic element 100a and the second acousto-optic element 100b are arranged so that the axis along the propagation direction of the ultrasonic wave 21a emitted by the first transducer 20a and the axis along the propagation direction of the ultrasonic wave 21b emitted by the second transducer 20b are in the same plane.

[0051] In the acousto-optic deflector 100d according to this embodiment, the first acousto-optic element 100a and the second acousto-optic element 100b operate in a shear mode. When the first acousto-optic element 100a and the second acousto-optic element 100b operate in a shear mode in which the light beam LB is emitted with a polarization orthogonal to the incident polarization and the deflection angle of the light beam LB is large, the polarization direction of the light beam LB, which is the emitted light diffracted by the first acousto-optic element 100a, changes by 90° with respect to the polarization direction of the light beam LB incident on the acousto-optic deflector 100d. If the polarization direction remains changed, the diffraction efficiency of the light beam LB will decrease when it passes through the second acousto-optic element 100b. Therefore, the acousto-optical deflector 100d according to this embodiment further includes a polarization plane rotator 50 arranged along the optical path of the light beam LB between the first acousto-optical element 100a and the second acousto-optical element 100b to rotate the polarization plane of the light beam LB in order to restore the original deflection direction of the light beam LB incident on the second acousto-optical element 100b. As an example, a ½λ plate or the like is used as the polarization plane rotator 50. The other configurations are the same as those in the first embodiment, and therefore description thereof will be omitted.

[0052] Third Embodiment Next, an acousto-optical deflector 100e according to a third embodiment will be described with reference to Fig. 11. Fig. 11 is a schematic diagram of the acousto-optical deflector 100e according to this embodiment.

[0053] The acousto-optical deflector 100e according to this embodiment includes a first acousto-optical element 100a, a second acousto-optical element 100b, a third acousto-optical element 100a', and a fourth acousto-optical element 100b', which are arranged along the optical path of the light beam LB. In the acousto-optical deflector 100e according to this embodiment, the first acousto-optical element 100a, the second acousto-optical element 100b, the third acousto-optical element 100a', and the fourth acousto-optical element 100b' are arranged in this order along the traveling direction of the light beam LB. The first acousto-optical element 100a includes a first optical element 10a and a first transducer 20a that generates an ultrasonic wave 21a within the first optical element 10a. The second acousto-optical device 100b includes a second optical element 10b and a second transducer 20b that generates an ultrasonic wave 21b within the second optical element 10b. The third acousto-optical device 100a' includes a third optical element 10a' and a third transducer 20a' that generates an ultrasonic wave 21a' within the third optical element 10a'. The fourth acousto-optical device 100b' includes a fourth optical element 10b' and a fourth transducer 20b' that generates an ultrasonic wave 21b' within the fourth optical element 10b'. The acousto-optical deflector 100e according to this embodiment also includes a drive circuit 30 that drives the first transducer 20a, the second transducer 20b, the third transducer 20a', and the fourth transducer 20b' so as to change the frequencies of the ultrasonic waves 21a, 21b, 21a', and 21b' generated in the first optical element 10a, the second optical element 10b, the third optical element 10a', and the fourth optical element 10b' when the light beam LB passes through the first optical element 10a, the second optical element 10b, the third optical element 10a', and the fourth optical element 10b'. The drive circuit 30 drives the first to fourth transducers 20a, 20b, 20a', and 20b', but this is not limiting, and a drive circuit 30 may be provided individually for each transducer.

[0054] The first transducer 20 a and the second transducer 20 b are arranged to sandwich the optical path of the light beam LB. The second acousto-optic device 100 b is arranged at an angle with respect to the first acousto-optic device 100 a so that the propagation direction of the ultrasonic wave 21 b traveling through the second optical device 10 b is inclined with respect to the propagation direction of the ultrasonic wave 21 a traveling through the first optical device 10 a.

[0055] Furthermore, the first acousto-optic element 100a and the second acousto-optic element 100b are arranged so that the axis along the propagation direction of the ultrasonic wave 21a emitted by the first transducer 20a and the axis along the propagation direction of the ultrasonic wave 21b emitted by the second transducer 20b are in the same plane.

[0056] The third transducer 20 a′ and the fourth transducer 20 b′ are disposed on either side of the optical path of the light beam LB. The fourth acousto-optic device 100 b′ is disposed at an angle with respect to the third acousto-optic device 100 a′ so that the propagation direction of the ultrasonic wave 21 a′ traveling through the third optical device 10 a′ is inclined with respect to the propagation direction of the ultrasonic wave 21 b′ traveling through the fourth optical device 10 b′.

[0057] The propagation direction of the ultrasonic wave 21a propagating through the first optical element 10a by the first transducer 20a of the first acousto-optic device 100a and the propagation direction of the ultrasonic wave 21a' propagating through the third optical element 10a' by the third transducer 20a' of the third acousto-optic device 100a' are mutually different. That is, the propagation direction of the ultrasonic wave 21a propagating through the first optical element 10a by the first transducer 20a of the first acousto-optic device 100a and the propagation direction of the ultrasonic wave 21a' propagating through the third optical element 10a' by the third transducer 20a' of the third acousto-optic device 100a' are non-parallel to each other.

[0058] In the acousto-optic deflector 100e according to this embodiment, the propagation direction of the ultrasonic wave 21a' traveling through the third optical element 10a' is substantially perpendicular to the propagation direction of the ultrasonic wave 21a traveling through the first optical element 10a. Furthermore, the axis along the propagation direction of the ultrasonic wave 21a' generated by the third transducer 20a' and the axis along the propagation direction of the ultrasonic wave 21b' generated by the fourth transducer 20b' are in the same plane. Therefore, the ultrasonic wave 21a' generated by the third transducer 20a' propagates toward the back of the paper, and the ultrasonic wave 21b' generated by the fourth transducer 20b' propagates toward the front of the paper.

[0059] Since the acousto-optic deflector 100e according to this embodiment has four stages of acousto-optic elements 100a, 100b, 100a', and 100b', the light beam LB incident on the first acousto-optic element 100a is diffracted by the first acousto-optic element 100a, and the light beam LB diffracted by the first acousto-optic element 100a is diffracted by the second acousto-optic element 100b. Furthermore, the light beam LB passing through the second acousto-optic element 100b is incident on the third acousto-optic element 100a'. The light beam LB from the second acousto-optic element 100b incident on the third acousto-optic element 100a' is diffracted by the third acousto-optic element 100a', and the light beam LB from the third acousto-optic element 100a' incident on the fourth acousto-optic element 100b' is diffracted by the fourth acousto-optic element 100b'. More specifically, the first acousto-optic device 100a generates a −1st-order diffracted light of the incident light beam LB, the second acousto-optic device 100b generates a +1st-order diffracted light of the light beam LB from the first acousto-optic device 100a, the third acousto-optic device 100a' generates a −1st-order diffracted light of the light beam LB from the second acousto-optic device 100b, and the fourth acousto-optic device 100b' generates a +1st-order diffracted light of the light beam LB from the third acousto-optic device 100a'.

[0060] With the above configuration, the acousto-optical deflector 100e according to this embodiment can cancel the cylindrical effect in the X-axis direction generated in the light beam LB by interaction with the ultrasonic waves 21a from the first transducer 20a through interaction with the ultrasonic waves 21b from the second transducer 20b. Furthermore, the cylindrical effect in the Y-axis direction, perpendicular to the X-axis, generated in the light beam LB by interaction with the ultrasonic waves 21a' from the third transducer 20a' can be canceled through interaction with the ultrasonic waves 21b' from the fourth transducer 20b'. Thus, the acousto-optical deflector 100e according to this embodiment can freely change the deflection range, deflection direction, and deflection speed of the light beam LB in both the X-axis and Y-axis directions while canceling the cylindrical effects in the X-axis and Y-axis directions.

[0061] However, when the acousto-optic deflector 100e operates in the longitudinal mode, particularly when polarization-dependent crystals such as tellurium dioxide (TeO2) and lead molybdate (PbMoO4) are used for the first through fourth optical elements 10a, 10b, 10a', and 10b', it is necessary to adjust the polarization direction of the incident light beam LB to match the deflection direction of the light beam LB at the third acousto-optic element 100a' and the fourth acousto-optic element 100b'. Therefore, a polarization plane rotator 60, such as a half-wave plate, is inserted between the second acousto-optic element 100b and the third acousto-optic element 100a' to rotate the polarization plane of the light beam from the second acousto-optic element 100b. Of course, if polarization-independent acousto-optic materials are used for the first through fourth optical elements 10a, 10b, 10a', and 10b', the polarization plane rotator 60 is not necessary.

[0062] In the acousto-optic deflector 100e according to this embodiment, the first optical element 10a, the second optical element 10b, the third optical element 10a', and the fourth optical element 10b' are each separate. However, the first optical element 10a and the second optical element 10b may be integrated, and the third optical element 10a' and the fourth optical element 10b' may be integrated. That is, the first transducer 20a and the second transducer 20b may be provided in one optical element (e.g., one crystal) so as to face each other across the optical path of the light beam LB, and the third transducer 20a' and the fourth transducer 20b' may be provided in another optical element (e.g., one crystal) so as to face each other across the optical path of the light beam LB.

[0063] In the acousto-optical deflector 100e according to this embodiment, the first acousto-optic element 100a generates −1st-order diffracted light, the second acousto-optic element 100b generates +1st-order diffracted light, the third acousto-optic element 100a' generates −1st-order diffracted light, and the fourth acousto-optic element 100b' generates +1st-order diffracted light. However, the first acousto-optic element 100a may be configured to generate +1st-order diffracted light, the second acousto-optic element 100b generates −1st-order diffracted light, the third acousto-optic element 100a' generates +1st-order diffracted light, and the fourth acousto-optic element 100b' generates −1st-order diffracted light. Furthermore, the present invention is not limited to the case where ±1st-order diffracted light is used. Alternatively, the first acousto-optic element 100a may generate nth-order diffracted light, the second acousto-optic element 100b may generate −nth-order diffracted light, the third acousto-optic element 100a' may generate mth-order diffracted light, and the fourth acousto-optic element 100b' may generate −mth-order diffracted light. This configuration also allows the cylindrical effect to be canceled. Here, n and m are integers other than 0. However, it is preferable to use ±1 as the values ​​of n and m, i.e., ±1st-order diffracted light, because this allows for higher diffraction efficiency.

[0064] Although only the scanning method for sweeping the frequency has been described in this embodiment, the acousto-optical deflector 100e according to this embodiment can also be driven by a random access method.

[0065] Fourth Embodiment Next, an acousto-optical deflector 100f according to a fourth embodiment will be described with reference to Fig. 12. Fig. 12 is a schematic diagram of the acousto-optical deflector 100f according to this embodiment.

[0066] The acousto-optical deflector 100f according to this embodiment, like the acousto-optical deflector 100e according to the third embodiment, has a first acousto-optical element 100a, a second acousto-optical element 100b, a third acousto-optical element 100a', and a fourth acousto-optical element 100b' arranged along the optical path of the light beam LB, and the first acousto-optical element 100a, the second acousto-optical element 100b, the third acousto-optical element 100a', and the fourth acousto-optical element 100b' are arranged in this order along the traveling direction of the light beam LB. The first acousto-optical element 100a includes a first optical element 10a and a first transducer 20a that generates an ultrasonic wave 21a within the first optical element 10a. The second acousto-optical device 100b includes a second optical element 10b and a second transducer 20b that generates an ultrasonic wave 21b within the second optical element 10b. The third acousto-optical device 100a' includes a third optical element 10a' and a third transducer 20a' that generates an ultrasonic wave 21a' within the third optical element 10a'. The fourth acousto-optical device 100b' includes a fourth optical element 10b' and a fourth transducer 20b' that generates an ultrasonic wave 21b' within the fourth optical element 10b'. The acousto-optical deflector 100f according to this embodiment also includes a drive circuit 30 that drives the first transducer 20a, the second transducer 20b, the third transducer 20a', and the fourth transducer 20b' so as to change the frequencies of the ultrasonic waves 21a, 21b, 21a', and 21b' generated in the first optical element 10a, the second optical element 10b, the third optical element 10a', and the fourth optical element 10b' when the light beam LB passes through the first optical element 10a, the second optical element 10b, the third optical element 10a', and the fourth optical element 10b'. The drive circuit 30 drives the first to fourth transducers 20a, 20b, 20a', and 20b', but this is not limiting, and a drive circuit 30 may be provided individually for each transducer. In FIG. 12, the first to fourth optical elements 10a, 10b, 10a', and 10b' and the drive circuit 30 are omitted.

[0067] The first transducer 20 a and the second transducer 20 b are arranged to sandwich the optical path of the light beam LB. The second acousto-optic device 100 b is arranged at an angle with respect to the first acousto-optic device 100 a so that the propagation direction of the ultrasonic wave 21 b traveling through the second optical device 10 b is inclined with respect to the propagation direction of the ultrasonic wave 21 a traveling through the first optical device 10 a.

[0068] Furthermore, the first acousto-optic element 100a and the second acousto-optic element 100b are arranged so that the axis along the propagation direction of the ultrasonic wave 21a emitted by the first transducer 20a and the axis along the propagation direction of the ultrasonic wave 21b emitted by the second transducer 20b are in the same plane.

[0069] The third transducer 20 a′ and the fourth transducer 20 b′ are disposed on either side of the optical path of the light beam LB. The fourth acousto-optic device 100 b′ is disposed at an angle with respect to the third acousto-optic device 100 a′ so that the propagation direction of the ultrasonic wave 21 a′ traveling through the third optical device 10 a′ is inclined with respect to the propagation direction of the ultrasonic wave 21 b′ traveling through the fourth optical device 10 b′.

[0070] The propagation direction of the ultrasonic wave 21a propagating through the first optical element 10a by the first transducer 20a of the first acousto-optic device 100a and the propagation direction of the ultrasonic wave 21a' propagating through the third optical element 10a' by the third transducer 20a' of the third acousto-optic device 100a' are mutually different. That is, the propagation direction of the ultrasonic wave 21a propagating through the first optical element 10a by the first transducer 20a of the first acousto-optic device 100a and the propagation direction of the ultrasonic wave 21a' propagating through the third optical element 10a' by the third transducer 20a' of the third acousto-optic device 100a' are non-parallel to each other.

[0071] In the acousto-optic deflector 100f according to this embodiment, the propagation direction of the ultrasonic wave 21a' traveling through the third optical element 10a' is substantially perpendicular to the propagation direction of the ultrasonic wave 21a traveling through the first optical element 10a. Also, the axis along the propagation direction of the ultrasonic wave 21a' generated by the third transducer 20a' and the axis along the propagation direction of the ultrasonic wave 21b' generated by the fourth transducer 20b' are in the same plane.

[0072] In the acousto-optical deflector 100f according to this embodiment, the first acousto-optic element 100a, the second acousto-optic element 100b, the third acousto-optic element 100a', and the fourth acousto-optic element 100b' operate in a shear mode. When the first acousto-optic element 100a, the second acousto-optic element 100b, the third acousto-optic element 100a', and the fourth acousto-optic element 100b' operate in the shear mode, in which the light beam LB is emitted with a polarization orthogonal to the incident polarization and the deflection angle of the light beam LB can be increased, the polarization direction of the light beam LB changes by 90° each time it passes through the first to fourth acousto-optic elements 100a, 100b, 100a', and 100b'. To prevent a decrease in diffraction efficiency, the acousto-optic deflector 100f according to this embodiment further includes a first polarization plane rotator 70 disposed between the first acousto-optic element 100a and the second acousto-optic element 100b for rotating the polarization plane of the light beam LB from the first acousto-optic element 100a, and a second polarization plane rotator 80 disposed between the third acousto-optic element 100a' and the fourth acousto-optic element 100b' for rotating the polarization plane of the light beam LB from the third acousto-optic element 100b'. For example, a half-lambda plate or the like is used for the first polarization plane rotator 70 and the second polarization plane rotator 80. The remaining configuration is the same as that of the third embodiment, and therefore a description thereof will be omitted.

[0073] Fifth Embodiment Next, an acousto-optical deflector 100g according to a fifth embodiment will be described with reference to Fig. 13. Fig. 13 is a schematic diagram of the acousto-optical deflector 100g according to this embodiment.

[0074] The acousto-optical deflector 100g according to this embodiment includes a first acousto-optical element 100a, a second acousto-optical element 100b, a third acousto-optical element 100a', and a fourth acousto-optical element 100b' arranged along the optical path of the light beam LB. The first acousto-optical element 100a, the third acousto-optical element 100a', the second acousto-optical element 100b, and the fourth acousto-optical element 100b' are arranged in this order along the traveling direction of the light beam LB. The first acousto-optical element 100a includes a first optical element 10a and a first transducer 20a that generates an ultrasonic wave 21a within the first optical element 10a. The second acousto-optical element 100b includes a second optical element 10b and a second transducer 20b that generates an ultrasonic wave 21b within the second optical element 10b. The third acousto-optical device 100a' includes a third optical element 10a' and a third transducer 20a' that generates an ultrasonic wave 21a' within the third optical element 10a'. The fourth acousto-optical device 100b' includes a fourth optical element 10b' and a fourth transducer 20b' that generates an ultrasonic wave 21b' within the fourth optical element 10b'. The acousto-optical deflector 100g according to this embodiment also includes a drive circuit 30 that drives the first transducer 20a, the second transducer 20b, the third transducer 20a', and the fourth transducer 20b' so as to change the frequencies of the ultrasonic waves 21a, 21b, 21a', and 21b' generated in the first optical element 10a, the second optical element 10b, the third optical element 10a', and the fourth optical element 10b' when the light beam LB passes through the first optical element 10a, the second optical element 10b, the third optical element 10a', and the fourth optical element 10b'. The drive circuit 30 drives the first to fourth transducers 20a, 20b, 20a', and 20b', but this is not limiting, and a drive circuit 30 may be provided individually for each transducer. In FIG. 13, the first to fourth optical elements 10a, 10b, 10a', and 10b' and the drive circuit 30 are omitted.

[0075] The first transducer 20 a and the second transducer 20 b are arranged to sandwich the optical path of the light beam LB. The second acousto-optic device 100 b is arranged at an angle with respect to the first acousto-optic device 100 a so that the propagation direction of the ultrasonic wave 21 b traveling through the second optical device 10 b is inclined with respect to the propagation direction of the ultrasonic wave 21 a traveling through the first optical device 10 a.

[0076] Furthermore, the first acousto-optic element 100a and the second acousto-optic element 100b are arranged so that the axis along the propagation direction of the ultrasonic wave 21a emitted by the first transducer 20a and the axis along the propagation direction of the ultrasonic wave 21b emitted by the second transducer 20b are in the same plane.

[0077] The third transducer 20 a′ and the fourth transducer 20 b′ are disposed on either side of the optical path of the light beam LB. The fourth acousto-optic device 100 b′ is disposed at an angle with respect to the third acousto-optic device 100 a′ so that the propagation direction of the ultrasonic wave 21 a′ traveling through the third optical device 10 a′ is inclined with respect to the propagation direction of the ultrasonic wave 21 b′ traveling through the fourth optical device 10 b′.

[0078] The propagation direction of the ultrasonic wave 21a propagating through the first optical element 10a by the first transducer 20a of the first acousto-optic device 100a and the propagation direction of the ultrasonic wave 21a' propagating through the third optical element 10a' by the third transducer 20a' of the third acousto-optic device 100a' are mutually different. That is, the propagation direction of the ultrasonic wave 21a propagating through the first optical element 10a by the first transducer 20a of the first acousto-optic device 100a and the propagation direction of the ultrasonic wave 21a' propagating through the third optical element 10a' by the third transducer 20a' of the third acousto-optic device 100a' are non-parallel to each other.

[0079] In the acousto-optical deflector 100g according to this embodiment, the propagation direction of the ultrasonic wave 21a' traveling through the third optical element 10a' is approximately perpendicular to the propagation direction of the ultrasonic wave 21a traveling through the first optical element 10a. The propagation direction of the ultrasonic wave 21b' traveling through the fourth optical element 10b' is approximately perpendicular to the propagation direction of the ultrasonic wave 21b traveling through the second optical element 100b. Furthermore, an axis along the propagation direction of the ultrasonic wave 21a' generated by the third transducer 20a' and an axis along the propagation direction of the ultrasonic wave 21b' generated by the fourth transducer 20b' are in the same plane.

[0080] In the acousto-optical light deflector 100g according to this embodiment, the third acousto-optical element 100a' is arranged in the optical path of the light beam LB between the first acousto-optical element 100a and the second acousto-optical element 100b, and the second acousto-optical element 100b is arranged in the optical path of the light beam LB between the third acousto-optical element 100a' and the fourth acousto-optical element 100b'.

[0081] In the acousto-optical deflector 100g according to this embodiment, the light beam LB incident on the first acousto-optic element 100a is diffracted by the first acousto-optic element 100a, and the light beam LB diffracted by the first acousto-optic element 100a is incident on the third acousto-optic element 100a' and diffracted by the third acousto-optic element 100a'. The light beam LB passing through the third acousto-optic element 100a' is incident on the second acousto-optic element 100b. The light beam LB from the third acousto-optic element 100a' is incident on the second acousto-optic element 100b, is diffracted by the second acousto-optic element 100b, and then is incident on the fourth acousto-optic element 100b'. The light beam LB from the second acousto-optic element 100b is diffracted by the fourth acousto-optic element 100b'. More specifically, the first acousto-optic device 100a generates a +1st-order diffracted light of the incident light beam LB, the third acousto-optic device 100a' generates a -1st-order diffracted light of the light beam LB from the first acousto-optic device 100a, the second acousto-optic device 100b generates a -1st-order diffracted light of the light beam LB from the third acousto-optic device 100a', and the fourth acousto-optic device 100b' generates a +1st-order diffracted light of the light beam LB from the third acousto-optic device 100a'.

[0082] In the acousto-optic light deflector 100g according to this embodiment, the first acousto-optic element 100a generates +1st-order diffracted light, the second acousto-optic element 100b generates −1st-order diffracted light, the third acousto-optic element 100a' generates −1st-order diffracted light, and the fourth acousto-optic element 100b' generates +1st-order diffracted light. However, the first acousto-optic element 100a may be configured to generate −1st-order diffracted light, the second acousto-optic element 100b generates +1st-order diffracted light, the third acousto-optic element 100a' generates +1st-order diffracted light, and the fourth acousto-optic element 100b' generates −1st-order diffracted light. Furthermore, instead of ±1st-order diffracted light, the first acousto-optic element 100a may generate nth-order diffracted light, the second acousto-optic element 100b may generate −nth-order diffracted light, the third acousto-optic element 100a′ may generate mth-order diffracted light, and the fourth acousto-optic element 100b′ may generate −mth-order diffracted light. This configuration also allows the cylindrical effect to be canceled. Here, n and m are integers other than 0. However, it is preferable to use ±1 as the values ​​of n and m, i.e., ±1st-order diffracted light, because this allows for higher diffraction efficiency.

[0083] In the acousto-optic deflector 100g according to this embodiment, the first acousto-optic element 100a, the second acousto-optic element 100b, the third acousto-optic element 100a', and the fourth acousto-optic element 100b' operate in a shear mode. In this mode, the light beam LB is emitted with a polarization orthogonal to the incident polarization, and a large deflection angle of the light beam LB can be achieved. By arranging the first acousto-optic element 100a, the third acousto-optic element 100a', the second acousto-optic element 100b, and the fourth acousto-optic element 100b' in this order along the traveling direction of the light beam LB, the light beam LB can be deflected in two axial directions without using a polarization plane rotator such as a half-lambda plate. As a result, the acousto-optical deflector 100g according to this embodiment can contribute to space saving and cost reduction compared to the acousto-optical deflector 100f according to the fourth embodiment.

[0084] On the other hand, the light beam LB is incident on the second acousto-optic element 100b and the fourth acousto-optic element 100b', which are responsible for the correction, at deflection angles in the X-axis and Y-axis directions, respectively, with respect to the propagation directions of the ultrasonic waves 21a and 21a' of the first acousto-optic element 100a and the third acousto-optic element 100a', so there is a slight misalignment between the axis direction in which the cylindrical effect is generated and the axis of the correction direction. For this reason, the acousto-optic light deflector 100g according to this embodiment performs correction taking this angular misalignment into account. The remaining configuration is the same as in embodiment 3, so a description thereof will be omitted.

[0085] (Layered Manufacturing Apparatus) Next, with reference to FIG. 14, an embodiment of an layered manufacturing apparatus using the acousto-optical deflectors 100a to 100g (hereinafter referred to as acousto-optical deflector 100x) according to each embodiment will be described.

[0086] 14 is a diagram schematically illustrating the configuration of an additive manufacturing apparatus 1x according to this embodiment. As illustrated in FIG. 14, the additive manufacturing apparatus 1x includes a stage 11x, a light irradiation device 12x, a moving device 13x, a material supply device 14x, a gas supply device 15x, a light source 16x, and a control device 20x. The additive manufacturing apparatus 1x can manufacture an additive manufacturing object 1000x having a predetermined shape by using a material 121x, such as a powdered metal material, supplied to an object 110x disposed on the stage 11x from the light irradiation device 12x and the material supply device 14x together with a laser beam 120x as a light beam LB.

[0087] The light irradiation device 12x can irradiate the object 110x with laser light 120x as an energy beam and can selectively supply a predetermined amount of material 121x toward the object 110x on the stage 11x. The light irradiation device 12x includes a housing 21x, a nozzle 22x housed in the housing 21x, and an optical system 23x housed in the housing 21x.

[0088] The light irradiation device 12x can be moved relative to the stage 11x by a moving device 13x. The nozzle 22x is connected to a material supply device 14x and a gas supply device 15x via supply pipes 97x. The nozzle 22x includes a light passage 31x through which a laser beam 120x emitted from an optical system 23x passes, a material ejection port 32x from the tip of the light passage 31x, and a gas ejection port 33x from the tip of the material ejection port 32x.

[0089] As shown in FIG. 14 , the light passage 31x has an inner diameter that allows the laser beam 120x to pass through and to be irradiated from the optical system 23x onto the target 110x within a predetermined angular range. The material 121x supplied from the material supply device 14x is injected onto the target 110x from the material injection port 32x. The material 121x may be injected into a molten pool formed on the target 110x by the irradiation of the laser beam 120x onto the target 110x and melted in the molten pool, or may be melted by the laser beam 120x on its way from the material supply device 14x to the target 110x. The gas injection port 33x injects a gas 122x supplied from the gas supply device 15x. The gas 122x supplied by the gas supply device 15x is used to prevent oxidation of the material 121x injected from the nozzle 22x onto the target 110x and the formation of other compounds when the material 121x is melted to form a layer on the target 110x.

[0090] The optical system 23x is connected to the light source 16x via an optical fiber 98x. The optical system 23x includes a lens device 41x provided on the exit side of the optical fiber 98x, a mirror 42x provided on the exit side of the lens device 41x, an acousto-optical deflector 100x provided on the exit side of the mirror 42x, and an Fθ lens 43x provided on the exit side of the acousto-optical deflector 100x.

[0091] The lens device 41x converts the laser beam 120x emitted from the light source 16x via the optical fiber 98x into a parallel beam. The mirror 42x guides the laser beam 120x from the lens device 41x to the acousto-optical deflector 100x.

[0092] The acousto-optical deflector 100x diffracts the incident laser beam 120x and emits the diffracted laser beam 120x to an Fθ lens 43x. The acousto-optical deflector 100x can deflect the laser beam 120x in two axial directions: an X direction along the horizontal direction and a Y direction perpendicular to the X direction.

[0093] The Fθ lens 43x emits the laser light 120x incident within a predetermined angular range into the light passage 31x. The Fθ lens 43x irradiates the laser light 120x with the laser light 120x focused on the object 110x.

[0094] The moving device 13x is capable of moving the light irradiation device 12x in the horizontal direction. The material supply device 14x supplies the material 121x to the object 110x and is capable of adjusting the supply amount of the material 121x to be supplied and the ejection speed (supply rate) of the material 121x ejected from the nozzle 22x. The gas supply device 15 supplies the gas 122x to the object 110x and is capable of adjusting the supply amount of the gas 122x to be supplied and the ejection speed (supply rate) of the gas 122x ejected from the nozzle 22x.

[0095] The light source 16x is a supply source of the laser beam 120x that emits the laser beam 120x to the optical fiber 98x at a power density sufficient to melt the material 121x. The light source 16x is also capable of changing the power density of the emitted laser beam 120x.

[0096] The control device 20x controls the moving device 13x, the material supply device 14x, the gas supply device 15x, the light source 16x, and the acousto-optical light deflector 100x.

[0097] The control device 20x is configured to be able to move the nozzle 22x in three axial directions, namely, the X direction, the Y direction, and the Z direction perpendicular to the X direction and the Y direction, by controlling the movement device 13x. The control device 20x is able to adjust the supply of the material 121x and the supply amount and supply speed of the material 121x by controlling the material supply device 14x. The control device 20x is able to adjust the supply of the gas 122x and the supply amount and supply speed of the gas 122x by controlling the gas supply device 15x. The control device 20x is able to adjust the power of the laser light 120x emitted from the light source 16x by controlling the light source 16x.

[0098] The control device 20x controls the acousto-optical light deflector 100x to adjust the emission angle of the laser beam 120x emitted from the nozzle 22x and change the irradiation position of the laser beam 120x with respect to the light irradiation device 12x. The control device 20x also includes a memory unit 20ax. The memory unit 20ax stores the shape of the layered object 100x to be manufactured.

[0099] Next, a method for processing the target object 110x using the layered manufacturing apparatus 1x configured as above will be described with reference to FIG.

[0100] 15 is a flowchart showing a method for processing the object 110x. First, in step S1501, the object 110x is irradiated with a laser beam 120x from a light source 16x via a light irradiation device 12x.

[0101] Next, in step S1502, the control device 20x controls the acousto-optical deflector 100x to change the irradiation position of the laser beam 120x irradiated onto the object 110x.

[0102] In step S1503, the control device 20x controls the material supply device 14x and the gas supply device 15x to supply the material 121x and the gas 122x to the object 110x. As a result, the material 121x supplied to the object 110x is melted by the laser beam 120x to form a layer on the object 110x. By repeating these steps, the layered object 100x is manufactured. Step S1502 is a light beam deflection method for deflecting the laser beam 120x, which is a light beam. This light beam deflection method will be described in detail with reference to FIG. 16 .

[0103] 16 is a flowchart showing a light beam deflection method. Note that the explanation here will be given for the case where the acousto-optical deflector 100 according to the first embodiment is used. The same applies to the cases where the acousto-optical deflectors according to the other embodiments are used.

[0104] In step S1601, a laser beam 120x from a light source 16x is incident on a first acousto-optical device 100a including a first optical element 10a and a first transducer 20a that generates an ultrasonic wave 21a within the first optical element 10a.

[0105] In step S1602, the laser light 120x from the first acousto-optical element 100a is incident on a second acousto-optical element 100b including a second optical element 10b and a second transducer 20b that generates an ultrasonic wave 21b within the second optical element 10b.

[0106] In step S1603, an ultrasonic wave 21a is generated in the first optical element 10a by the first transducer 20a in a first propagation direction.

[0107] In step S1604, an ultrasonic wave 21b is generated in the second optical element 10b by the second transducer 20b in a second propagation direction.

[0108] Here, the second propagation direction is inclined with respect to the first propagation direction, and the first transducer 20a generates ultrasonic waves 21a from a first side with respect to the optical path of the laser light 120x, and the second transducer 20b generates ultrasonic waves 21b from a second side opposite to the first side with respect to the optical path of the laser light 120x.

[0109] Through the above steps, the laser light 120x from the light source 16x is deflected by the acousto-optical deflector 100 without generating the cylindrical effect.

[0110] Furthermore, the flow described above is an example, and unnecessary steps may be deleted, new steps may be added, the processing order may be changed, or steps may be performed in parallel, within the scope of the present disclosure.

[0111] Although the preferred embodiments of the present disclosure have been described above, the present disclosure is not limited to these embodiments, and various modifications and changes are possible within the scope of the gist of the present disclosure.

[0112] 100 Acousto-optical light deflector LB Light beam 100a First acousto-optical element 10a First optical element 20a First transducer 100b Second acousto-optical element 10b Second optical element 20b Second transducer 100a' Third acousto-optical element 10a' Third optical element 20a' Third transducer 100b' Fourth acousto-optical element 10b' Fourth optical element 20b' Fourth transducer

Claims

1. An acousto-optical deflector having a first acousto-optical element and a second acousto-optical element arranged along the optical path of a light beam, wherein the first acousto-optical element includes a first optical element and a first transducer that generates ultrasonic waves within the first optical element, and the second acousto-optical element includes a second optical element and a second transducer that generates ultrasonic waves within the second optical element, the first transducer and the second transducer are arranged to sandwich the optical path of the light beam, and the propagation direction of the ultrasonic waves traveling within the second optical element is inclined relative to the propagation direction of the ultrasonic waves traveling within the first optical element.

2. An acousto-optical deflector according to claim 1, wherein the light beam incident on the first acousto-optical element is diffracted by the first acousto-optical element, and the light beam diffracted by the first acousto-optical element is diffracted by the second acousto-optical element.

3. An acousto-optical deflector according to claim 1 or 2, wherein the first acousto-optical element generates n-th order diffracted light of the incident light beam, and the second acousto-optical element generates -n-th order diffracted light of the light beam from the first acousto-optical element, where n is an integer excluding 0.

4. An acousto-optical deflector according to claim 3, wherein n=1 or n=-1.

5. An acousto-optical deflector according to any one of claims 1 to 4, further comprising a drive circuit for driving the first transducer and the second transducer so as to change the frequency of ultrasonic waves generated within the first optical element and the second optical element when the light beam passes through the first optical element and the second optical element.

6. An acousto-optical deflector as claimed in claim 5, wherein said drive circuit drives said first transducer and said second transducer simultaneously at the same sweep frequency.

7. An acousto-optical deflector according to claim 5, which satisfies the condition df1 / dt=df2 / dt, where f1 is the sweep frequency of the ultrasonic waves emitted by the first transducer, f2 is the sweep frequency of the ultrasonic waves emitted by the second transducer, and t is the sweep time of the first transducer and the second transducer.

8. An acousto-optical deflector according to any one of claims 5 to 7, wherein the second acousto-optical element is arranged at an inclination of θ1 + θ2 with respect to the first acousto-optical element, where θ1 is the Bragg angle at the center frequency of the sweep frequency of the ultrasonic waves emitted by the first transducer, and θ2 is the Bragg angle at the center frequency of the sweep frequency of the ultrasonic waves emitted by the second transducer.

9. An acousto-optical deflector according to any one of claims 1 to 8, wherein an axis along the propagation direction of the ultrasonic waves generated by the first transducer and an axis along the propagation direction of the ultrasonic waves generated by the second transducer are in the same plane.

10. An acousto-optical deflector according to any one of claims 1 to 9, wherein the first optical element and the second optical element are integral.

11. An acousto-optical deflector according to any one of claims 1 to 9, wherein the first acousto-optical element and the second acousto-optical element operate in a shear mode, and further comprising a polarization rotator arranged along the optical path of the light beam between the first acousto-optical element and the second acousto-optical element for rotating the polarization plane of the light beam.

12. An acousto-optical deflector according to any one of claims 1 to 11, further comprising a third acousto-optical element and a fourth acousto-optical element arranged along the optical path of the light beam, wherein the third acousto-optical element includes a third optical element and a third transducer that generates ultrasonic waves within the third optical element, and the fourth acousto-optical element includes a fourth optical element and a fourth transducer that generates ultrasonic waves within the fourth optical element, the third transducer and the fourth transducer being arranged to sandwich the optical path of the light beam, and the propagation direction of the ultrasonic waves propagating within the first optical element by the first transducer of the first acousto-optical element and the propagation direction of the ultrasonic waves propagating within the third optical element by the third transducer of the third acousto-optical element being mutually different.

13. An acousto-optical deflector as described in claim 12, wherein the propagation direction of the ultrasonic waves traveling within the fourth optical element is inclined relative to the propagation direction of the ultrasonic waves traveling within the third optical element, and the propagation direction of the ultrasonic waves traveling within the third optical element is approximately perpendicular to the propagation direction of the ultrasonic waves traveling within the first optical element.

14. An acousto-optical deflector according to claim 12 or 13, wherein the light beam having passed through the second acousto-optical element is incident on the third acousto-optical element.

15. An acousto-optical deflector according to any one of claims 12 to 14, wherein the light beam from the second acousto-optical element that is incident on the third acousto-optical element is diffracted by the third acousto-optical element, and the light beam from the third acousto-optical element that is incident on the fourth acousto-optical element is diffracted by the fourth acousto-optical element.

16. An acousto-optical deflector according to any one of claims 12 to 15, wherein the third acousto-optical element generates m-th order diffracted light of the light beam from the second acousto-optical element, and the fourth acousto-optical element generates -m-th order diffracted light of the light beam from the third acousto-optical element, where m is an integer excluding 0.

17. An acousto-optical deflector according to claim 16, wherein m=1 or m=-1.

18. An acousto-optical deflector according to any one of claims 12 to 17, further comprising a polarization plane rotator disposed between the second acousto-optical element and the third acousto-optical element, for rotating the polarization plane of the light beam from the second acousto-optical element.

19. An acousto-optical deflector according to any one of claims 12 to 17, wherein the first to fourth acousto-optical elements operate in a shear mode, and further comprising: a first polarization plane rotator disposed between the first acousto-optical element and the second acousto-optical element, for rotating the polarization plane of the light beam from the first acousto-optical element; and a second polarization plane rotator disposed between the third acousto-optical element and the fourth acousto-optical element, for rotating the polarization plane of the light beam from the third acousto-optical element.

20. An acousto-optical deflector as described in claim 12 or 13, wherein the third acousto-optical element is disposed in the optical path of the light beam between the first acousto-optical element and the second acousto-optical element, and the second acousto-optical element is disposed in the optical path of the light beam between the third acousto-optical element and the fourth acousto-optical element.

21. An acousto-optical deflector as described in claim 20, wherein the propagation direction of the ultrasonic waves traveling within the fourth optical element is inclined relative to the propagation direction of the ultrasonic waves traveling within the third optical element, and the propagation direction of the ultrasonic waves traveling within the fourth optical element is approximately perpendicular to the propagation direction of the ultrasonic waves traveling within the second optical element.

22. An acousto-optical deflector according to claim 21, wherein the third acousto-optical element generates m-th order diffracted light of the light beam from the first acousto-optical element, and the fourth acousto-optical element generates -m-th order diffracted light of the light beam from the second acousto-optical element, where m is an integer excluding 0.

23. The acousto-optical deflector of claim 22, wherein m=1 or m=-1.

24. A light irradiation device for irradiating an object with a light beam, comprising: an acousto-optical light deflector according to any one of claims 1 to 23; and a control device for controlling the acousto-optical light deflector to change the irradiation position of the light beam relative to the light irradiation device.

25. An additive manufacturing apparatus comprising: the light irradiation device according to claim 24; and a material supply device that supplies material to the object.

26. A method for deflecting an optical beam, comprising: making an optical beam from a light source incident on a first acousto-optical element including a first optical element and a first transducer that generates ultrasonic waves in the first optical element; making the optical beam from the first acousto-optical element incident on a second acousto-optical element including a second optical element and a second transducer that generates ultrasonic waves in the second optical element; generating the ultrasonic waves in a first propagation direction in the first optical element by the first transducer; and generating the ultrasonic waves in a second propagation direction in the second optical element by the second transducer, wherein the second propagation direction is inclined with respect to the first propagation direction; and wherein the first transducer generates the ultrasonic waves from a first side with respect to an optical path of the optical beam, and the second transducer generates the ultrasonic waves from a second side with respect to the optical path of the optical beam, opposite to the first side.

27. A light beam irradiation method comprising: irradiating an object with a light beam; and changing the irradiation position of the light beam irradiated onto the object using the light beam deflection method described in claim 26.

28. A processing method comprising: irradiating the object with the light beam using the light beam irradiation method described in claim 27; and supplying material to the object.

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