JP7618924B2 - Optical path control device, display device, and optical path control method - Google Patents

Description

The present invention relates to an optical path control device, a display device, and an optical path control method.

For example, as shown in Patent Document 1, an optical device is known that shifts the optical axis by swinging the optical section into which light enters. Patent Document 1 describes that by swinging the optical section to shift the optical path of the light passing through the optical section, it is possible to increase the resolution of the projected image beyond that of the light modulation device.

Patent No. 6451187

When shifting the optical path in this way, it is necessary to oscillate the optical section at high speed and then keep it stationary stably.

In view of the above problems, the present invention aims to provide an optical path control device, a display device, and an optical path control method that can oscillate an optical unit at high speed and stop it stably.

The light path control device according to one aspect of the present invention includes an oscillating unit including an optical member into which light is incident, an actuator for oscillating the oscillating unit, and a drive unit for applying to the actuator a drive signal having a waveform including a first period during which the current value is changed from a first current value to a second current value, and a second period that is continuous with the first period and during which the current value is maintained at the second current value, thereby causing the actuator to oscillate the oscillating unit and controlling the light path, and the drive unit applies the drive signal so that the length of the first period is a value that corresponds to the natural frequency of the oscillating unit.

A display device according to one aspect of the present invention includes the light path control device and an illumination device that illuminates the optical element with light.

An optical path control method according to one aspect of the present invention is an optical path control method for controlling an optical path by applying a drive signal to an actuator that oscillates an oscillating part including an optical member into which light is incident, and includes a step of applying to the actuator the drive signal having a waveform including a first period in which the current value is changed from a first current value to a second current value, and a second period that is continuous with the first period and in which the current value is maintained at the second current value, thereby causing the actuator to oscillate the oscillating part, and the length of the first period is set to a value corresponding to the natural frequency of the oscillating part.

According to the present invention, the optical part can be oscillated at high speed and then stably stopped.

FIG. 1 is a schematic diagram of a display device according to a first embodiment. FIG. 2 is a block diagram showing a schematic circuit configuration of the display device. FIG. 3 is a schematic diagram of the optical path control mechanism. FIG. 4 is a cross-sectional view taken along line AA of FIG. FIG. 5 is a graph illustrating the waveform of a drive signal according to the first embodiment. FIG. 6 is a graph illustrating a swing pattern of the optical portion according to the first embodiment. FIG. 7 is a block diagram illustrating a schematic circuit configuration of a display device according to the second embodiment. FIG. 8 is a graph illustrating the waveform of a drive signal according to the second embodiment. FIG. 9 is a graph illustrating a swing pattern of the optical portion according to the second embodiment. FIG. 10 is a graph illustrating the waveform of a drive signal according to the third embodiment. FIG. 11 is a graph illustrating a swing pattern of the optical portion according to the third embodiment.

The following describes in detail an embodiment of the present invention with reference to the drawings. Note that the present invention is not limited to the embodiment described below.

First Embodiment
(Display Device)
FIG. 1 is a schematic diagram of a display device according to the first embodiment. As shown in FIG. 1, the display device 1 according to the first embodiment has a light path control device 10 and an irradiation device 100. The irradiation device 100 is a device that irradiates light L for an image, and the light path control device 10 is a device that controls the optical path of the light L. In this embodiment, the light path control device 10 shifts the optical axis of the light L to shift the position of the image displayed by the light L, thereby making the resolution of the projected image higher than the resolution of the image by the irradiation device 100 (i.e., the number of pixels of a display element 106 described later).

As shown in FIG. 1, the irradiation device 100 includes a light source 101, polarizing plates 105R, 105G, and 105B, display elements 106R, 106G, and 106B, polarizing plates 107R, 107G, and 107B, a color synthesis prism 108, a projection lens 109, dichroic mirrors 120 and 121, reflecting mirrors 130 and 131, lenses 140 to 145, a polarization conversion element 150, and a video signal processing circuit 160. When there is no need to distinguish between the display elements 106R, 106G, and 106B, they are referred to as display elements 106.

The light source 101 is a light source that generates and irradiates light. The light source 101 irradiates incident light L0. In this embodiment, an example is shown in which one light source 101 is used as the light source that irradiates the incident light L0, but another optical device may be included to generate the incident light L0.

Incoming light L0 from light source 101 is incident on lens 140. Lenses 140 and 141 are, for example, fly-eye lenses. The illumination distribution of incident light L0 is homogenized by lenses 140 and 141, and the incident light is incident on polarization conversion element 150. Polarization conversion element 150 is an element that aligns the polarization of incident light L0, and has, for example, a polarizing beam splitter and a phase difference plate. For example, polarization conversion element 150 aligns incident light L0 to p-polarized light.

The incident light L0, whose polarization has been aligned by the polarization conversion element 150, is irradiated onto the dichroic mirror 120 via the lens 142. The lens 142 is, for example, a focusing lens.

The dichroic mirror 120 separates the incident light L0 into yellow light LRG and blue light LB that contains blue band components. The yellow illumination light LRG separated by the dichroic mirror 120 is reflected by the reflecting mirror 130 and enters the dichroic mirror 121.

The dichroic mirror 121 separates the incident yellow light LRG into red light LR containing red band components and green light LG containing green band components.

The red light LR separated by the dichroic mirror 121 is irradiated to the polarizing plate 105R via the lens 143. The green light LG separated by the dichroic mirror 121 is irradiated to the polarizing plate 105G via the lens 144. The blue light LB separated by the dichroic mirror 120 is reflected by the reflecting mirror 131 and irradiated to the polarizing plate 105B via the lens 145.

The polarizing plates 105R, 105G, and 105B have the property of reflecting either s-polarized light or p-polarized light and transmitting the other. For example, the polarizing plates 105R, 105G, and 105B reflect s-polarized light and transmit p-polarized light. The polarizing plates 105R, 105G, and 105B are also called reflective polarizing plates.

The p-polarized red light LR passes through the polarizing plate 105R and is irradiated onto the display element 106R. The p-polarized green light LG passes through the polarizing plate 105G and is irradiated onto the display element 106G. The p-polarized blue light LB passes through the polarizing plate 105B and is irradiated onto the display element 106B.

Display element 106R, display element 106G, and display element 106B are, for example, reflective liquid crystal display elements. In this embodiment, the display element 106R, display element 106G, and display element 106B are reflective liquid crystal display elements, but they are not limited to reflective types and may be configured to use transmissive liquid crystal display elements. In addition, various applications are possible for configurations that use other display elements instead of liquid crystal display elements.

The display element 106R is controlled by the video signal processing circuit 160. The video signal processing circuit 160 drives and controls the display element 106R based on image data of the red component. The display element 106R optically modulates the p-polarized red light LR in accordance with the control of the video signal processing circuit 160 to generate s-polarized red light LR. The display element 106G is controlled by the video signal processing circuit 160. The video signal processing circuit 160 drives and controls the display element 106G based on image data of the green component. The display element 106G optically modulates the p-polarized green light LG in accordance with the control of the video signal processing circuit 160 to generate s-polarized green light LG. The display element 106B is controlled by the video signal processing circuit 160. The video signal processing circuit 160 drives and controls the display element 106B based on image data of the blue component. Display element 106B optically modulates p-polarized blue light LB based on image data of the blue component under the control of video signal processing circuit 160 to generate s-polarized blue light LB.

The polarizing plates 107R, 107G, and 107B have the property of transmitting either s-polarized light or p-polarized light and reflecting or absorbing the other. For example, the polarizing plates 107R, 107G, and 107B transmit s-polarized light and absorb unnecessary p-polarized light.

The s-polarized red light LR generated by the display element 106R is reflected by the polarizing plate 105R, passes through the polarizing plate 107R, and is irradiated to the color synthesis prism 108. The s-polarized green light LG generated by the display element 106G is reflected by the polarizing plate 105G, passes through the polarizing plate 107G, and is irradiated to the color synthesis prism 108. The s-polarized blue light LB generated by the display element 106B is reflected by the polarizing plate 105B, passes through the polarizing plate 107B, and is irradiated to the color synthesis prism 108.

The color synthesis prism 108 synthesizes the incident red light LR, green light LG, and blue light LB, and irradiates the projection lens 109 with the resulting light L for image display. The light L is projected via the projection lens 109 onto a screen (not shown) or the like.

The irradiation device 100 has the above-described configuration, but the configuration is not limited to the above description and may be any configuration.

The light path control device 10 has a light path control mechanism 12, a control circuit (control unit) 14, and a drive circuit (drive unit) 16. The light path control mechanism 12 is a mechanism that oscillates when driven by the drive circuit 16. The light path control mechanism 12 is provided between the color synthesis prism 108 and the projection lens 109 in a direction along the light path of the light L. The light path control mechanism 12 oscillates while receiving the light L from the color synthesis prism 108, shifting the traveling direction (light path) of the light L and outputting it toward the projection lens 109. In this way, the light path control device 10 controls the light path of the light L so that the light path of the light L is shifted. Note that the position at which the light path control mechanism 12 is provided is not limited to between the color synthesis prism 108 and the projection lens 109, and may be any position.

FIG. 2 is a block diagram showing a schematic circuit configuration of the display device. As shown in FIG. 2, the video signal processing circuit 160 controls the display elements 106R, 106B, and 106G. The video signal processing circuit 160 receives a video signal including image data for controlling the display elements 106R, 106B, and 106G and a synchronization signal. The video signal processing circuit 160 controls the display elements 106R, 106B, and 106G based on the image data while synchronizing the timing based on the synchronization signal. The control circuit 14 has a digital circuit 14A and a converter 14B. The synchronization signal from the video signal processing circuit 160 is input to the digital circuit 14A. The digital circuit 14A generates a digital drive signal for driving the optical path control mechanism 12 while synchronizing the timing based on the synchronization signal. The converter 14B is a DA converter that converts a digital signal into an analog signal. The converter 14B converts the digital drive signal generated by the digital circuit 14A into an analog drive signal. The drive circuit 16 receives an analog drive signal from the converter 14B, amplifies the analog drive signal, and outputs it to the actuator 12B of the optical path control mechanism 12, which will be described later. The actuator 12B is driven in response to the drive signal to oscillate the oscillating part 12A, which will be described later.

(Optical Path Control Mechanism)
The configuration of the light path control mechanism 12 will be described in more detail. Fig. 3 is a schematic diagram of the light path control mechanism, and Fig. 4 is a cross-sectional view taken along line A-A in Fig. 3. As shown in Figs. 3 and 4, the light path control mechanism 12 has a swinging section 12A including an optical member 20 onto which light L is incident, and an actuator 12B that swings the swinging section 12A. More specifically, the light path control mechanism 12 has the optical member 20, a movable section 22, a support section 24, a shaft section 25, a coil 26, a yoke 27, and a magnet 28.

The optical member 20 is a member that transmits the incident light L. The light L is incident on one surface of the optical member 20, the optical member 20 transmits the incident light L, and emits the light L from the other surface. In this embodiment, the optical member 20 is a glass plate, but the material and shape may be arbitrary.

The movable part 22 is a member that supports the optical member 20. The movable part 22 is fixed to the optical member 20. Specifically, the movable part 22 in this embodiment is a plate-shaped member with a through hole formed in the center. The optical member 20 is fixed to the movable part 22 in a state where it is fitted into the through hole of the movable part 22. Note that the optical member 20 is fixed to the movable part 22 via a fixing member or adhesive for fixing it to the movable part 22, but the method of fixing the optical member 20 to the movable part 22 may be arbitrary.

The support section 24 is a member that supports the movable section 22 on which the optical member 20 is provided so that the movable section 22 can swing. In this embodiment, the support section 24 is a frame-shaped member that is provided so as to surround the outer periphery of the movable section 22. The shaft section 25 is a member that connects the movable section 22 to the support section 24 so that the movable section 22 can swing. In this embodiment, two shaft sections 25 are provided. The shaft sections 25 are provided at positions near the vertices of the rectangular optical member 20 that face each other. The movable section 22 swings around the swing axis AX, which is an axis that connects the shaft sections 25. When the movable section 22 swings around the swing axis AX, the attitude of the optical member 20 provided on the movable section 22 changes, and the optical path of the light L that passes through the optical member 20 is shifted.

The coil 26 is attached to the movable part 22 and fixed to the movable part 22. The coil 26 is provided at each of both ends of the movable part 22. The yoke 27 is a member that forms a magnetic path. The yoke 27 is attached to the support part 24 and fixed to the support part 24. The coil 26 is provided at each of both ends of the movable part 22 corresponding to the coil 26. The magnet 28 is a permanent magnet. The magnet 28 is attached to the yoke 27 and fixed to the yoke 27. The magnet 28 is disposed in a position adjacent to each coil 26. A drive signal from the drive circuit 16 is input to the coil 26. In the example of FIG. 4, the magnet 28 is attached to one side of the U-shaped yoke 27, and an air gap is formed between the surface of the magnet 28 that is not attached and the opposing side of the U-shaped yoke 27. The coil 26 is disposed in this air gap. A drive signal is input to the coil 26. As a result, a current flows through coil 26, which is a conductor within the magnetic field of magnet 28, generating a force that causes movable part 22 (oscillating part 12A) fixed to coil 26 to oscillate. In other words, actuator 12B according to this embodiment can be said to be an electromagnetic actuator composed of coil 26, yoke 27, and magnet 28.

In this embodiment, since the movable part 22 on which the optical member 20 is provided oscillates in this manner, the optical member 20, the movable part 22, and the coil 26 can be said to constitute the oscillating part 12A. In other words, the part of the light path control mechanism 12 that oscillates relative to the support part 24 can be said to refer to the oscillating part 12A. Note that, if a fixing member or adhesive for fixing the optical member 20 to the movable part 22, or a substrate or lead wire for passing a current through the coil 26, is provided, these also oscillate relative to the support part 24, and are therefore included in the oscillating part 12A.

The actuator in this embodiment is a so-called moving coil type in which the coil 26 is disposed in the movable part 22, but is not limited thereto. For example, it may be a so-called moving magnet type in which the magnet 28 is disposed in the movable part 22 and the coil 26 is disposed in the support part 24. In this case, the magnet 28 is oscillated together with the optical member 20, so the magnet 28 is included in the oscillating part 12A instead of the coil 26.

The optical path control mechanism 12 is configured as described above, but is not limited thereto, and may have any configuration in which the optical part can shift the optical path of the light L by oscillating the optical part due to an actuator to which a drive signal is applied.

In the optical path control mechanism 12, the actuator 12B swings the oscillating unit 12A in response to the drive signal. That is, the actuator 12B swings the oscillating unit 12A in response to the drive signal so that the oscillating unit 12A repeats a change in posture from a first angle D1 to a second angle D2 around the oscillating axis AX and a change in posture from the second angle D2 to the first angle D1. By repeating the swinging of the oscillating unit 12A between the first angle D1 and the second angle D2, the optical axis of the light L repeatedly shifts from the first position to the second position and from the second position to the first position. In this embodiment, the image projected on the screen by the light L when the optical axis is at the first position and the image projected on the screen by the light L when the optical axis is at the second position are shifted by half a pixel. That is, the image projected on the screen repeatedly shifts by half a pixel and returns by half a pixel. This increases the apparent number of pixels, and the image projected on the screen can be made high-resolution. In this manner, since the shift amount of the optical axis in this embodiment is half a pixel of the image, the first angle D1 and the second angle D2 are set to angles that allow the image to be shifted by half a pixel. Note that the shift amount of the image is not limited to half a pixel, and may be any amount, such as ¼ or ⅛ of a pixel. The first angle D1 and the second angle D2 may also be set appropriately according to the shift amount of the image.

(Drive signal)
Next, the drive signal applied from the drive circuit 16 to the actuator 12B will be described.

Figure 5 is a graph illustrating the waveform of the drive signal according to the first embodiment. The drive signal applied from the drive circuit 16 to the actuator 12B is an electric signal, and as shown in Figure 5, the current value changes over time. Hereinafter, the waveform representing the change in the current value of the drive signal over time will be referred to as the drive signal waveform. In Figure 5, the drive signal waveform is shown by a solid line. In the first embodiment, the drive signal has the same waveform repeated every cycle T. The cycle T includes a period T1 and a period T2 that follows the period T1 and is continuous with the period T1. The period T1 corresponds to the period during which an image (here, an image that is not shifted by half a pixel) is displayed when the optical axis of the light L is at the first position, and the period T2 corresponds to the period during which an image (here, an image that is shifted by half a pixel) is displayed when the optical axis of the light L is at the second position.

In the first period TA1 of the period T1, the current value of the drive signal changes from the first current value A1 to the second current value A2. More specifically, in the first period TA1, the current value of the drive signal changes linearly over time from the first current value A1 to the second current value A2. That is, the drive signal has a current value of the first current value A1 at the start timing of the first period TA1, and then the current value changes linearly from the first current value A1 to the second current value A2 at the end timing of the first period TA1. The first current value A1 is a current value that can hold the oscillating part 12A at the first angle D1 and is set according to the numerical value of the first angle D1. The second current value A2 is a current value that can hold the oscillating part 12A at the second angle D2 and is set according to the numerical value of the second angle D2. The first current value A1 and the second current value A2 are current values whose positive and negative signs are opposite to each other, and their absolute values may be equal. FIG. 5 illustrates an example in which the first current value A1 is negative and the second current value A2 is positive.

The length of the first period TA1 is a value corresponding to the natural frequency of the oscillating part 12A. As described above, the oscillating part 12A refers to the part of the optical path control mechanism 12 that oscillates with respect to the support part 24 (the optical member 20, the movable part 22, and the coil 26 in the example of this embodiment). In other words, it can be said that the length of the first period TA1 is a value corresponding to the natural frequency of the part that oscillates with respect to the support part 24. More specifically, the length of the first period TA1 is preferably approximately the same value as the natural period of the oscillating part 12A, and more preferably the same value as the natural period. Here, the natural period is the reciprocal of the natural frequency. In addition, "approximately the same value" means that a value that deviates from the natural period by the degree of the error range is also acceptable. For example, when the deviation from the natural period is within 5% of the value of the natural period, it may be considered to be "approximately the same value". In the following description, the term "approximately the same value" has the same meaning. The value of the natural vibration (the inverse of the natural frequency) is expressed as "1/f" [s], where f [Hz] is the natural frequency.

The natural frequency of the oscillating part 12A may be measured in advance. For example, a sine wave may be applied (swept) to the actuator 12B while gradually increasing the frequency from 0 Hz to measure the vibration of the oscillating part 12A, and the frequency at which the oscillating part 12A vibrates most strongly may be taken as the natural frequency of the oscillating part 12A. A microdisplacement meter may be used to measure the vibration. In this embodiment, the length of the first period TA1 is set based on the natural frequency of the oscillating part 12A measured in this manner, and the waveform of the drive signal is set so that the current changes from the first current value A1 to the second current value A2 during the first period TA1 of the set length.

In the second period TB1 of the period T1, the current value of the drive signal is held at the second current value A2. The second period TB1 is a period that follows the first period TA1 and is continuous with the first period TA1. It is preferable to increase the natural frequency of the oscillating part 12A, since it is possible to shorten the first period TA1 and lengthen the second period TB1 (for example, to make it longer than the first period TA1). It is not limited to the current value not strictly changing from the second current value A2, but may also include the current value deviating from the second current value A2 within a predetermined value range. The predetermined value here may be set arbitrarily, and may be, for example, 10% of the second current value A2.

In this way, during period T1, the current value of the drive signal gradually changes from the first current value A1 to the second current value A2, and when the current value reaches the second current value A2, the current value is maintained at the second current value A2.

In the third period TA2 of the period T2, the current value of the drive signal changes from the second current value A2 to the first current value A1. The third period TA2 is after the second period TB1 and can be said to be a period that follows the second period TB1. Furthermore, in the third period TA2, the current value of the drive signal changes linearly over time from the second current value A2 to the first current value A1. That is, at the start timing of the third period TA2, the current value of the drive signal is the second current value A2, and then the current value changes linearly from the second current value A2 to become the first current value A1 at the end timing of the third period TA2.

The length of the third period TA2 is a value that corresponds to the natural frequency of the oscillating part 12A. More specifically, the length of the third period TA2 is preferably approximately the same value as the natural period (the inverse of the natural frequency) of the oscillating part 12A, and more preferably the same value as the natural period. Third period TA2 In this embodiment, the length of the third period TA2 is equal to the length of the first period TA1.

In the fourth period TB2 of the period T2, the current value of the drive signal is held at the first current value A1. The fourth period TB2 is a period that follows the third period TA2 and is continuous with the third period TA2. The fourth period TB2 is a period that follows the first period TA1 and is continuous with the first period TA1. In this embodiment, the fourth period TB2 is equal to the second period TB1. By increasing the natural frequency of the oscillating part 12A, the third period TA2 can be shortened and the fourth period TB2 can be lengthened (for example, longer than the third period TA2), which is preferable. Note that being held at the first current value A1 is not limited to the current value not strictly changing from the first current value A1, and may also include the current value deviating from the first current value A1 within a range of a predetermined value. The predetermined value here may be set arbitrarily, and may be, for example, 10% of the first current value A1.

In this way, during period T2, the current value of the drive signal gradually changes from the second current value A2 to the first current value A1, and when the current value reaches the first current value A1, the current value is maintained at the first current value A1.

As described above, in the first embodiment, the waveform of the drive signal is trapezoidal, and the first periods TA1 and TA2 during which the current value changes correspond to the natural frequency of the oscillating part 12A.

The dashed lines in FIG. 5 indicate the periods during which light L is irradiated. It is preferable that the irradiation device 100 does not irradiate light L in the first period TA1, and irradiates light L in the second period TB1. It is also preferable that the irradiation device 100 does not irradiate light L in the third period TA2, and irradiates light L in the fourth period TB2.

(Swing pattern)
Next, the oscillation pattern of the oscillating unit 12A due to application of a drive signal will be described. Fig. 6 is a graph illustrating the oscillation pattern of the optical unit according to the first embodiment. The oscillation pattern of the oscillating unit 12A refers to the displacement angle (angle around the oscillation axis AX) of the oscillating unit 12A per unit time when a drive signal is applied to the actuator 12B. In Fig. 6, the oscillation pattern is shown by a solid line.

During the first period TA1, the current value of the drive signal changes from the first current value A1 to the second current value A2. As a result, the displacement angle of the oscillating part 12A changes from the first angle D1 to the second angle D2 during the first period TA1.

During the second period TB1, the drive signal has a current value held at the second current value A2. As a result, the displacement angle of the oscillating part 12A is held at the second angle D2 during the second period TB1. Note that being held at the second angle D2 does not necessarily mean that the displacement angle does not change strictly from the second angle D2, but may also include the displacement angle deviating from the second angle D2 within a predetermined range. The predetermined value here may be set arbitrarily, and may be, for example, 10% of the second angle D2.

During the third period TA2, the current value of the drive signal changes from the second current value A2 to the first current value A1. As a result, the displacement angle of the oscillating part 12A changes from the second angle D2 to the first angle D1 during the third period TA2.

During the fourth period TB2, the current value of the drive signal is held at the first current value A1. As a result, the displacement angle of the oscillating part 12A is held at the first angle D1 during the fourth period TB2. Note that being held at the first angle D1 does not necessarily mean that the displacement angle does not change strictly from the first angle D1, but may also include the displacement angle deviating from the first angle D1 within a predetermined range. The predetermined value here may be set arbitrarily, and may be, for example, a value of 10% of the first angle D1.

The light L is irradiated during the second periods TB1 and TB2. Therefore, during the second period TB1, the light L is irradiated onto the oscillating portion 12A held at the second angle D2, and the optical path of the light L is in the first position. During the fourth period TB2, the light L is irradiated onto the oscillating portion 12A held at the first angle D1, and the optical path of the light L shifts to the second position, causing the image to shift by half a pixel.

In an optical path control device that shifts the optical path by oscillating the optical unit, it is required to oscillate the optical unit stably. As a result of intensive research, the inventor has discovered that by setting the length of the first periods TA1 and TA2 to a value corresponding to the natural frequency of the oscillating unit 12A, it is possible to suppress the oscillation of the oscillating unit 12A in the second periods TB1 and TB2 and oscillate the oscillating unit 12A stably. That is, in this embodiment, the length of the first periods TA1 and TA2 is set to a value corresponding to the natural frequency of the oscillating unit 12A, so that the oscillation of the oscillating unit 12A in the second periods TB1 and TB2 can be suppressed and the oscillating unit 12A can be oscillated stably. Therefore, according to this embodiment, the oscillating unit 12A can be oscillated at high speed and stopped stably to suppress image degradation.

(effect)
As described above, the light path control device 10 according to this embodiment includes a swinging unit 12A including an optical member 20 on which light L is incident, an actuator 12B that swings the swinging unit 12A, and a drive circuit 16 (drive unit) that applies a drive signal to the actuator 12B to swing the swinging unit 12A and control the light path. The drive circuit 16 applies a drive signal to the actuator 12B, the drive signal having a waveform including a first period TA1 in which the current value is changed from a first current value A1 to a second current value A2, and a second period TB1 that is continuous with the first period TA1 and in which the current value is maintained at the second current value A2. The drive circuit 16 applies the drive signal so that the length of the first period TA1 corresponds to the natural frequency of the swinging unit 12A.

In this way, in the first embodiment, by setting the length of the first period TA1 to a value corresponding to the natural frequency of the oscillating part 12A, it is possible to suppress vibration of the oscillating part 12A in the second period TB1 and stably oscillate the oscillating part 12A. In addition, by changing the current value in the first period TA1, which has a length corresponding to the natural frequency of the oscillating part 12A, and then setting a waveform that maintains the current value in the subsequent second period TB1, it is possible to easily set a waveform that can stably oscillate the oscillating part 12A without complicating the waveform setting.

The drive circuit 16 also applies a drive signal so that the length of the first period TA1 is the reciprocal of the natural frequency of the oscillating part 12A. By making the length of the first period TA1 the reciprocal of the natural frequency of the oscillating part 12A, the oscillating part 12A can be oscillated more stably.

The drive circuit 16 also applies a drive signal so that the current value changes linearly from the first current value A1 to the second current value A2 during the first period TA1. By making the change in the current value during the first period TA1 linear, the oscillating part 12A can be oscillated more stably.

The display device 1 according to this embodiment also includes an optical path control device 10 and an irradiation device 100 that irradiates the oscillating portion 12A with light L. By including the optical path control device 10, the display device 1 according to this embodiment can stably oscillate the oscillating portion 12A and suppress image degradation.

In addition, the irradiation device 100 irradiates the oscillating portion 12A with light L during the second period TB1. By irradiating light L during the second period TB1, it becomes possible to appropriately shift the optical path.

The optical path control method according to this embodiment controls the optical path by applying a drive signal to actuator 12B, which swings oscillating portion 12A on which light L is incident. This method has a step of applying a drive signal having a waveform including a first period TA1, in which the current value is changed from a first current value A1 to a second current value A2, and a second period TB1, which is continuous with the first period TA1 and in which the current value is maintained at the second current value A2, to actuator 12B, thereby causing actuator 12B to swing oscillating portion 12A. In this method, the length of first period TA1 is set to a value corresponding to the natural frequency of oscillating portion 12A. According to this method, oscillating portion 12A can be stably oscillated.

Second Embodiment
Next, a second embodiment will be described. In the second embodiment, the waveform of the drive signal is different from that in the first embodiment. Description of the configuration of the second embodiment common to the first embodiment will be omitted.

Figure 7 is a block diagram showing a schematic circuit configuration of a display device in the second embodiment. As shown in Figure 7, the control circuit 14 in the second embodiment includes a digital circuit 14A, and does not have a DA converter (converter 14B) as in the first embodiment. In the second embodiment, a digital drive signal generated by the digital circuit 14A is input to the drive circuit 16, which amplifies the digital drive signal and outputs it to the actuator 12B. The actuator 12B is driven in response to the drive signal to oscillate the oscillating portion 12A. Thus, in the second embodiment, a digital drive signal is input to the drive circuit 16, but this is not limited thereto, and a drive signal converted to analog by the converter 14B may be input as in the first embodiment.

(Drive waveform)
8 is a graph illustrating the waveform of the drive signal according to the second embodiment. As shown in FIG. 8, in the second embodiment, the current value is held at zero during the first period TA1. In this embodiment, since the digital circuit 14A and the like include a digital switching circuit, the supply of current to the actuator 12B can be stopped, and the period during which the supply of current is stopped is the period during which the current value is set to zero.

The length of the first period TA1 is a value that corresponds to the natural frequency of the oscillating part 12A. More specifically, the length of the first period TA1 is preferably approximately the same as half the natural period (the reciprocal of the natural frequency) of the oscillating part 12A, and more preferably the same as half the natural period (the reciprocal of the natural frequency). Note that half the natural period is expressed as "1/(2·f)" [s], where the natural frequency is f [Hz].

In the second period TB1, the current value of the drive signal is held at the second current value A2. The second period TB1 is a period that follows the first period TA1 and is continuous with the first period TA1. That is, at the start timing of the second period TB1 (the timing when the first period TA1 switches to the second period TB1), the current value switches from zero to the second current value A2, and the current value is held at the second current value A2 until the end timing of the second period TB1.

In this way, in the second embodiment, the drive signal in period T1 has a current value held at zero during the first period TA1, the current value switches to the second current value A2 at the start of the second period TB1, and the current value is held at the second current value A2 during the second period TB1.

In the second embodiment, the current value is held at zero during the third period TA2. The third period TA2 is a period that follows the second period TB1 and is continuous with the second period TB1. That is, at the start timing of the third period TA2 (the timing when the second period TB1 switches to the third period TA2), the current value switches from the second current value A2 to zero, and is held at zero until the end timing of the third period TA2.

The length of the third period TA2 is a value that corresponds to the natural frequency of the oscillating part 12A. More specifically, the length of the third period TA2 is preferably approximately the same as half the natural period (the reciprocal of the natural frequency) of the oscillating part 12A, and more preferably the same as half the natural period (the reciprocal of the natural frequency). In this embodiment, the length of the third period TA2 is equal to the length of the first period TA1.

In the fourth period TB2, the current value of the drive signal is held at the first current value A1. The fourth period TB2 is a period that follows the third period TA2 and is continuous with the third period TA2. That is, at the start timing of the fourth period TB2 (the timing when the third period TA2 switches to the fourth period TB2), the current value switches from zero to the first current value A1, and the current value is held at the first current value A1 until the end timing of the fourth period TB2.

In this way, in the second embodiment, the drive signal in period T2 has a current value held at zero during the third period TA2, the current value switches to the first current value A1 at the start of the fourth period TB2, and the current value is held at the first current value A1 during the fourth period TB2.

In the first period TA1 following the fourth period TB2, the current value is held at zero as described above. That is, at the start of the first period TA1 (the timing when the fourth period TB2 switches to the first period TA1), the current value switches from the first current value A1 to zero, and is held at zero until the end of the first period TA1.

The dashed lines in FIG. 8 indicate the periods during which light L is irradiated. It is preferable that the irradiation device 100 does not irradiate light L in the first period TA1, and irradiates light L in the second period TB1. It is also preferable that the irradiation device 100 does not irradiate light L in the third period TA2, and irradiates light L in the fourth period TB2.

(Swing pattern)
Next, the oscillation pattern of the oscillation section 12A caused by application of a drive signal will be described with reference to Fig. 9. Fig. 9 is a graph illustrating the oscillation pattern of the optical section according to the second embodiment.

At the start of the first period TA1, the current value of the drive signal switches from the first current value A1 to zero, and the current value is maintained at zero until the end of the first period TA1. As a result, the displacement angle of the oscillating part 12A changes from the first angle D1 to the second angle D2 during the first period TA1. More specifically, the oscillating part 12A, which has been twisted to the first angle D1 and maintained at the first current value A1, is released from the twist and returns to the neutral position as the current becomes zero, and then the inertial force acts, twisting it to the second angle D2 on the opposite side, thereby reaching the second angle D2.

At the start of the second period TB1, the drive signal switches from a current value of zero to a second current value A2, and the current value is maintained at the second current value A2 until the end of the second period TB1. As a result, the displacement angle of the oscillating part 12A is maintained at the second angle D2 during the second period TB1. In other words, the force of the oscillating part 12A twisted to the second angle D2 balances the force exerted by the second current value A2 to return it to a neutral position, and the oscillating part 12A is maintained at the second angle D2.

At the start of the third period TA2, the current value of the drive signal switches from the second current value A2 to zero, and the current value is maintained at zero until the end of the third period TA2. As a result, the displacement angle of the oscillating part 12A changes from the second angle D2 to the first angle D1 during the third period TA2.

At the start of the fourth period TB2, the drive signal switches from a current value of zero to a first current value A1, and the current value is maintained at the first current value A1 until the end of the fourth period TB2. As a result, the displacement angle of the oscillating part 12A is maintained at the first angle D1 during the fourth period TB2.

In the second embodiment, the length of the first periods TA1 and TA2 during which the current value is switched to zero and maintained at zero corresponds to the natural frequency of the oscillating part 12A, so that the vibration of the oscillating part 12A during the second periods TB1 and TB2 can be suppressed and the oscillating part 12A can be oscillated stably. Therefore, according to this embodiment, image degradation can be suppressed. Furthermore, by setting the current value to zero during the first periods TA1 and TA2, it is possible to shorten the length of the first periods TA1 and TA2 and lengthen the length of the second periods TB1 and TB2, rather than gradually switching the current value as in the first embodiment, for example. This makes it possible to extend the period during which light L is irradiated, and more suitably suppress image degradation.

(effect)
As described above, the light path control device 10 according to the second embodiment includes a swinging unit 12A on which light L is incident, an actuator 12B that swings the swinging unit 12A, and a drive circuit 16 (drive unit) that applies a drive signal to the actuator 12B to swing the swinging unit 12A and control the light path. The drive circuit 16 applies a drive signal to the actuator 12B, the drive signal having a waveform including a first period TA1 in which the current value is zero, and a second period TB1 that follows the first period TA1 and is continuous with the first period TA1, and in which the current value is maintained at a second current value A2. The drive circuit 16 applies the drive signal so that the length of the first period TA1 corresponds to the natural frequency of the swinging unit 12A.

In this way, in the second embodiment, by setting the length of the first period TA1 to a value corresponding to the natural frequency of the oscillating part 12A, it is possible to suppress the oscillation of the oscillating part 12A in the second period TB1, and to stably oscillate the oscillating part 12A. In addition, by setting the current value to zero in the first period TA1, the length of which corresponds to the natural frequency of the oscillating part 12A, and then switching to and maintaining the second current value A2 in the subsequent second period TB1, it is possible to easily set a waveform that allows the oscillating part 12A to stably oscillate, without complicating the waveform settings.

The drive circuit 16 also applies a drive signal so that the length of the first period TA1 is approximately equal to half the natural period (the inverse of the natural frequency) of the oscillating part 12A. By setting the length of the first period TA1 to the inverse of the natural frequency of the oscillating part 12A, the oscillating part 12A can be oscillated more stably.

The drive circuit 16 also applies a drive signal so that the current value is maintained at the first current value A1, which is opposite in sign to the second current value A2, during a fourth period TB2 (third period) that precedes the first period TA1 and is subsequent to the first period TA1. In this way, by applying current values that are opposite in sign to the first period TA1 before and after the first period TA1, the oscillating portion 12A can be oscillated stably and appropriately.

Third Embodiment
Next, a third embodiment will be described. In the third embodiment, the waveform of the drive signal is different from that in the first embodiment. Description of the configuration of the third embodiment common to the first embodiment will be omitted.

The control circuit 14 according to the third embodiment includes a digital circuit 14A, as in the second embodiment, and does not need to have a DA converter (converter 14B) as in the first embodiment. That is, in the third embodiment, a digital drive signal generated by the digital circuit 14A is input to the drive circuit 16, and the drive circuit 16 switches the positive and negative current of the drive signal using a switching circuit (not shown), i.e., switches the current so that the direction is reversed but the current value is the same, and outputs it to the actuator 12B. In this way, in the third embodiment, a digital drive signal is input to the drive circuit 16, but this is not limited thereto, and a drive signal converted to analog by the converter 14B may be input as in the first embodiment.

(Drive waveform)
10 is a graph illustrating the waveform of the driving signal according to the third embodiment. As shown in FIG. 10, in the third embodiment, in the first period TA1, the current value is held at the second current value A2, and then the current value is held at the first current value A1. That is, in the period TA1a of the first period TA1, the current value is held at the second current value A2, and in the period TA1b of the first period TA1, the current value is held at the first current value A1. The period TA1b is a period that follows the period TA1a and is continuous with the period TA1a. That is, at the start timing of the period TA1b (the timing when the period TA1a switches to the period TA1b), the current value switches from the second current value A2 to the first current value A1, and the current value is held at the first current value A1 until the end timing of the period TA1b.

The length of the first period TA1 is a value that corresponds to the natural frequency of the oscillating part 12A. The length of the first period TA1 is preferably approximately the same as one-third of the natural period (the reciprocal of the natural frequency) of the oscillating part 12A, and more preferably the same as one-third of the natural period. Note that one-third of the natural period (the reciprocal of the natural frequency) is expressed as "1/(3·f)" [s], where the natural frequency is f [Hz].

More specifically, the length of period TA1a and the length of period TA1b in the first period TA1 correspond to the natural frequency of the oscillating part 12A. It is preferable that the length of period TA1a and the length of period TA1b are the same. More specifically, it is preferable that the length of period TA1a and the length of period TA1b are approximately the same as one-sixth of the natural period (the reciprocal of the natural frequency) of the oscillating part 12A, and it is more preferable that they are the same as one-sixth of the natural period. Note that, when the natural frequency is f [Hz], one-sixth of the reciprocal of the natural frequency is expressed as "1/(6·f)" [s].

In the second period TB1, the current value of the drive signal is held at the second current value A2. The second period TB1 is a period that follows the first period TA1 (period TA1b) and is continuous with the first period TA1 (period TA1b). That is, at the start timing of the second period TB1 (the timing when period TA1b switches to the second period TB1), the current value switches from the first current value A1 to the second current value A2, and the current value is held at the second current value A2 until the end timing of the second period TB1.

Thus, in the third embodiment, the drive signal in period T1 has a current value held at the second current value A2 in period TA1a, a current value switched to and held at the first current value A1 in period TA1b, and a current value switched to and held at the second current value A2 in the second period TB1.

In the third embodiment, in the third period TA2, the current value is held at the first current value A1, and then held at the second current value A2. That is, at the start timing of period TA2a of the third period TA2 (the timing when the second period TB1 switches to period TA2a), the current value switches from the second current value A2 to the first current value A1, and is held at the first current value A1 until the end timing of period TA2a. Period TA2b is a period that follows period TA2a and is continuous with period TA2a. That is, at the start timing of period TA2b (the timing when period TA2a switches to period TA2b), the current value switches from the first current value A1 to the second current value A2, and is held at the second current value A2 until the end timing of period TA2b.

The length of the third period TA2 corresponds to the natural frequency of the oscillating part 12A. The length of the third period TA2 is preferably approximately equal to one-third of the natural period (the inverse of the natural frequency) of the oscillating part 12A, and more preferably equal to one-third of the natural period. In this embodiment, the length of the third period TA2 is equal to the length of the first period TA1.

Moreover, the length of period TA2a and the length of period TA2b in the third period TA2 correspond to the natural frequency of the oscillating part 12A. It is preferable that the length of period TA2a and the length of period TA2b are the same. More specifically, it is preferable that the length of period TA2a and the length of period TA2b are approximately the same as one-sixth of the reciprocal of the natural frequency of the oscillating part 12A, and more preferably the same as one-sixth of the natural period. In this embodiment, the length of period TA2a is equal to the length of period TA1a, and the length of period TA2b is equal to the length of period TA1b.

In the fourth period TB2, the current value of the drive signal is held at the first current value A1. The fourth period TB2 is a period that follows the third period TA2 (period TA2b) and is continuous with the third period TA2 (period TA2b). That is, at the start of the fourth period TB2 (the timing when period TA2b switches to the fourth period TB2), the current value switches from the second current value A2 to the first current value A1, and is held at the first current value A1 until the end of the fourth period TB2.

Thus, in the third embodiment, the current value of the drive signal in period T2 is held at the first current value A1 in period TA2a, the current value switches to and is held at the second current value A2 in period TA2b, and the current value switches to and is held at the first current value A1 in the fourth period TB2.

In the period TA1a following the fourth period TB2, the current value is held at the second current value A2 as described above. That is, at the start of the period TA1a (the timing when the fourth period TB2 switches to the period TA1a), the current value switches from the first current value A1 to the second current value A2, and is held at the second current value A2 until the end of the period TA1a.

The dashed lines in FIG. 10 indicate the periods during which light L is irradiated. It is preferable that the irradiation device 100 does not irradiate light L in the first period TA1, and irradiates light L in the second period TB1. It is also preferable that the irradiation device 100 does not irradiate light L in the third period TA2, and irradiates light L in the fourth period TB2.

(Swing pattern)
Next, the oscillation pattern of the oscillation section 12A caused by application of a drive signal will be described below. Fig. 11 is a graph illustrating the oscillation pattern of the optical section according to the third embodiment.

At the start of the period TA1a, the drive signal switches from the first current value A1 to the second current value A2, and the current value is maintained at the second current value A2 until the end of the period TA1a. At the start of the period TA1b, the current value switches from the second current value A2 to the first current value A1, and the current value is maintained at the first current value A1 until the end of the period TA1b. As a result, the displacement angle of the oscillating part 12A changes from the first angle D1 to the second angle D2 during the first period TA1 (periods TA1a and TA1b). More specifically, a force is applied in the direction of return at the second current value A2 to the force that tries to twist back at the first angle D1, and the oscillating part 12A is accelerated in the direction of the second angle D2. If it is left as is, it will be twisted further than the second angle D2 due to inertia, so in this embodiment, the brake is applied by passing the first current value A1 after that. This allows it to swing even faster than the second embodiment.

At the start of the second period TB1, the current value of the drive signal switches from the first current value A1 to the second current value A2, and the current value is maintained at the second current value A2 until the end of the second period TB1. As a result, the displacement angle of the oscillating part 12A is maintained at the second angle D2 during the second period TB1.

At the start of period TA2a, the drive signal switches from the second current value A2 to the first current value A1, and maintains the current value at the first current value A1 until the end of period TA2a. At the start of period TA2b, the drive signal switches from the first current value A1 to the second current value A2, and maintains the current value at the second current value A2 until the end of period TA2b. As a result, the displacement angle of the oscillating part 12A changes from the second angle D2 to the first angle D1 during the third period TA2 (periods TA2a and TA2b).

At the start of the fourth period TB2, the current value of the drive signal switches from the second current value A2 to the first current value A1, and the current value is maintained at the first current value A1 until the end of the fourth period TB2. As a result, the displacement angle of the oscillating part 12A is maintained at the first angle D1 during the fourth period TB2.

In the third embodiment, the length of the first periods TA1 and TA2 during which the current value is switched between positive and negative corresponds to the natural frequency of the oscillating part 12A, so that the vibration of the oscillating part 12A during the second periods TB1 and TB2 can be suppressed, and the oscillating part 12A can be oscillated stably. Therefore, according to this embodiment, image degradation can be suppressed. Furthermore, by switching the current value between positive and negative during the first periods TA1 and TA2, the length of the first periods TA1 and TA2 can be made shorter and the length of the second periods TB1 and TB2 can be made longer than in the first and second embodiments, for example. This makes it possible to extend the period during which light L is irradiated, and more suitably suppress image degradation.

(effect)
As described above, the light path control device 10 according to the third embodiment includes a swinging unit 12A on which light L is incident, an actuator 12B that swings the swinging unit 12A, and a drive circuit 16 (drive unit) that applies a drive signal to the actuator 12B to swing the swinging unit 12A and control the light path. The drive circuit 16 applies a drive signal to the actuator 12B, the drive signal having a waveform including a first period TA1 in which the current value is held at the second current value A2 and then a first current value A1 having a polarity opposite to that of the second current value A2, and a second period TB1 that is continuous with the first period TA1 and in which the current value is held at the second current value A2. The drive circuit 16 applies the drive signal so that the length of the first period TA1 corresponds to the natural frequency of the swinging unit 12A.

In this way, in the third embodiment, by setting the length of the first period TA1 to a value corresponding to the natural frequency of the oscillating part 12A, it is possible to suppress the oscillation of the oscillating part 12A in the second period TB1, and to stably oscillate the oscillating part 12A. In addition, by switching the positive and negative current values in the first period TA1, which has a length corresponding to the natural frequency of the oscillating part 12A, and then switching to and maintaining the second current value A2 in the subsequent second period TB1, it is possible to easily set a waveform that allows the oscillating part 12A to stably oscillate, without complicating the waveform settings.

The drive circuit 16 also applies a drive signal so that the length of the period TA1a during which the current is held at the second current value A2 in the first period TA1 is the same as the length of the period TA1b during which the current is held at the first current value A1 in the first period TA1. By making the lengths of the periods TA1a and TA1b equal, the oscillating portion 12A can be oscillated more stably.

The drive circuit 16 also applies a drive signal so that the length of the period TA1a during which the current is held at the second current value A2 in the first period TA1 and the length of the period TA1b during which the current is held at the first current value A1 in the first period TA1 are approximately equal to one-sixth of the reciprocal of the natural frequency of the oscillating part 12A. By setting the length of the first period TA1 within this range, the oscillating part 12A can be oscillated more stably.

Although the embodiments of the present invention have been described above, the contents of these embodiments do not limit the embodiments. The above-mentioned components include those that a person skilled in the art can easily imagine, those that are substantially the same, and those that are within the so-called equivalent range. Furthermore, the above-mentioned components can be combined as appropriate, and the configurations of each embodiment can also be combined. Furthermore, various omissions, substitutions, or modifications of the components can be made without departing from the spirit of the above-mentioned embodiments.

REFERENCE SIGNS LIST 1 display device 10 light path control device 12 light path control mechanism 12A optical section 12B actuator 16 drive circuit (drive section)
100 Irradiation device A1 First current value A2 Second current value D1 First angle D2 Second angle L Light TA1, TA2 First period TB1, TB2 Second period

Claims (5)

a swinging portion having an optical member to which light is incident;
An actuator that swings the swinging portion;
a drive unit that applies to the actuator a drive signal having a waveform including a first period during which a current value is changed from a first current value to a second current value, and a second period that is continuous with the first period and during which the current value is maintained at the second current value, thereby causing the actuator to swing the swing unit and controlling the optical path;
having
The drive unit applies the drive signal so that a length of the first period has the same value as an inverse of a natural frequency of the oscillator.
Optical path control device. 2 . The light path control device according to claim 1 , wherein the drive section applies the drive signal such that a current value changes linearly from the first current value to the second current value during the first period. 3. A light path control device comprising: the light path control device according to claim 1 or 2 ; and an irradiation device that irradiates the optical member with light.
Display device. The display device according to claim 3 , wherein the irradiation device irradiates the optical member with light during the second period. An optical path control method for controlling an optical path by applying a drive signal to an actuator that oscillates an oscillating unit including an optical member into which light is incident, comprising:
a step of applying to the actuator the drive signal having a waveform including a first period during which a current value is changed from a first current value to a second current value, and a second period subsequent to the first period during which the current value is maintained at the second current value, thereby causing the actuator to swing the swinging portion;
The length of the first period is set to the same value as the reciprocal of the natural frequency of the oscillation portion.
Optical path control method.

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