JP4735608B2 - Image display device - Google Patents

Description

  The present invention relates to an optical scanning device and an image display device, and in particular, an optical scanning device for scanning a laser beam modulated in accordance with an image signal (hereinafter referred to as “modulation”) and an image using the optical scanning device. The present invention relates to display device technology.

  FIG. 2 of Japanese Patent Application Laid-Open No. 2003-29182 has a problem that the phase range in which linearity can be obtained is narrow as a problem of resonance vibration, and in order to solve this problem, projection optics having f · θ characteristics. Further, there is disclosed a technique that corrects the bending of the scanning line as an adverse effect of using the f · θ lens by devising the amplitude of the vertical scanning unit.

  Japanese Patent Laid-Open No. 2006-201220 has an object to instantaneously return the scanning position of the laser beam after performing a two-dimensional scanning from the scanning start position to the scanning end position, and solves this problem. For this reason, a technique is disclosed in which laser light is divided into two systems using a diffraction grating, and the other scanning unit is returned to the initial position while one scanning unit performs two-dimensional scanning.

JP 2003-29182 A JP 2006-20220 A

  However, Japanese Patent Laid-Open No. 2003-29182 uses a projection optical system having an f · θ lens, which leads to an increase in the size of a system in a scanning image display apparatus. In addition, the f · θ lens is a rotationally asymmetric lens, and is generally expensive and increases the cost.

  Further, in Example 1 of Japanese Patent Application Laid-Open No. 2006-201220, when laser light is divided by a diffraction grating and scanning is performed using one of the divided parts, the other is not used, and the light use efficiency is reduced. To do. Further, as disclosed in Example 2 of Japanese Patent Application Laid-Open No. 2006-201220, when a plurality of laser light sources are used, power consumption is increased and there is a concern about cost increase.

  The present invention has been made in view of the above-described problems. An optical scanning device having excellent light utilization efficiency as an image display device and scanning characteristics excellent in linearity, and an image display device using the optical scanning device. The purpose is to provide.

  According to one aspect of the present invention, the polarization direction of light is switched after the first main scanning unit is scanned once, and the polarization direction of light is switched after the second main scanning unit is scanned once. A control unit for controlling the electro-optic modulator is provided.

  According to the present invention, it is possible to provide an optical scanning device having scanning characteristics with excellent linearity and excellent light utilization efficiency, and an image display device using the optical scanning device.

  Embodiments will be described below with reference to the drawings. In the drawings, elements having common functions are denoted by the same reference numerals, and repeated descriptions of elements once described are omitted.

  First, the basic configuration of the optical scanning device of the present invention will be described with reference to FIGS. Next, based on the basic configuration of the conventional optical scanning device and the description of the problems, the main points that the inventor newly noticed and reached the present invention will be described. Finally, the operation of the present invention will be described.

  The basic configuration of the optical unit of the optical scanning device according to the first embodiment will be described with reference to FIG.

  FIG. 1 is a basic configuration diagram of an optical unit showing a first embodiment of a multi-scanning system.

  As shown in FIG. 1, an optical unit 900 constituting the optical system of the optical scanning device according to the first embodiment performs light intensity modulation according to a light source unit 30 that emits a light beam and an image signal (not shown). An acousto-optic modulator (hereinafter abbreviated as “AOM”) 60, an electro-optic modulator 41 that converts the polarization direction of linearly polarized light by 90 degrees, a polarization beam splitter 42, a first A first system scanning unit 51 including a first main scanning mirror 11 as a main scanning unit and a first sub scanning mirror 21 as a first sub scanning unit; a second main scanning mirror 12 as a second main scanning unit; A second system scanning unit 52 including a second sub-scanning mirror 22 as a second sub-scanning unit, and a reflection mirror 43 that reflects the polarized light polarized and separated by the polarization beam splitter 42 toward the second main scanning mirror 12. And comprising.

  The light source unit 30 is, for example, a semiconductor laser. The semiconductor laser emits a light beam of predetermined linearly polarized light (here, it is assumed that the light is P-polarized light for the polarization beam splitter 42 for convenience). The laser light emitted from the light source unit 30 is modulated by the AOM 60 according to the image signal and enters the electro-optic modulator 41 as a polarization switching unit.

  The electro-optic modulator 41 includes a crystal having an electro-optic effect as described in, for example, Japanese Patent Application Laid-Open No. 2006-95566, and linearly polarized light passing through the crystal by applying a predetermined voltage. Can be rotated by 90 degrees. That is, the electro-optic modulator 41 outputs the P-polarized light (light having the first polarization direction) from the light source unit 30 as it is, or the P-polarized light (first polarization light) as the S-polarized light (second light). (Of course, when the S-polarized light is emitted from the light source unit 30, the reverse operation is performed). The polarization light switching control by the electro-optic modulator 41 will be described later.

  The laser light emitted from the electro-optic modulator 41 enters the polarization beam splitter 42. The polarization beam splitter 42 has a function of causing the laser light to go straight or reflected depending on the polarization state of the incident laser light. Therefore, the electro-optic modulator 41 and the polarization beam splitter 42 constitute an optical path switching unit that switches the polarization state of the laser light from the light source unit 30 and switches the optical path in two orthogonal directions in the polarization state after switching. I can say that.

  The AOM 60 is a device that modulates the laser light emitted from the light source unit 30 in accordance with the image signal, and reduces or blanks the laser light, and can also be used for color control. When full color control is performed, the color balance is determined by using the AOM 60 separately for at least the R light, G light, and B light. Thereafter, the R light, G light, and B light modulated using known optical components are combined into one light beam. In recent years, white lasers have been developed actively, and PCAOM (Polychromatic Acoustro-Optic Modulator) is used as the color modulation of the white laser. PCAOM is an apparatus that can detect an arbitrary wavelength from white laser light at an arbitrary ratio and create a specific color. PCAOM is also a kind of AOM using a special principle.

  Laser light emitted as P-polarized light from the electro-optic modulator 41 passes through the polarization beam splitter 42 and enters the first main scanning mirror 11 as the first main scanning unit in the horizontal direction. Details of the first main scanning mirror 11 that performs the scanning action by resonance vibration will be described later with reference to FIGS. Then, the laser beam subjected to the horizontal scanning action by the first main scanning mirror 11 enters the first sub-scanning mirror 21 as the first sub-scanning unit in the vertical direction. Since the first sub-scanning mirror 21 is driven so that the first galvanometer 210 performs the vertical scanning action, the laser light subjected to the vertical scanning action by the first sub-scanning mirror 21 is irradiated ( For example, the image is scanned two-dimensionally in the image display area 70 of the screen. For convenience of explanation, this scanning is referred to as a first system scanning, and a scanning unit composed of the first main scanning mirror 11 and the first sub-scanning mirror 21 is defined as a first system scanning unit 51.

  Next, the laser light emitted as S-polarized light from the electro-optic modulator 41 is reflected by the polarization beam splitter 42, then reflected by the reflecting mirror 43, and after changing the emission direction, the horizontal second main light is then reflected. The light enters the second main scanning mirror 12 as a scanning unit. Similar to the first main scanning mirror 11, the second main scanning mirror 12 performs scanning action by resonance vibration. The laser beam subjected to the horizontal scanning action by the second main scanning mirror 12 is incident on a second sub scanning mirror 22 as a second sub scanning unit in the vertical direction. Since the second sub-scanning mirror 22 is driven so as to perform the vertical scanning action by the second galvanometer 220, the laser light subjected to the vertical scanning action by the second sub-scanning mirror 22 is used in the image display area 70. Is scanned two-dimensionally. Similarly, this scanning is referred to as a second system scanning for convenience of explanation, and a scanning unit composed of the second main scanning mirror 12 and the second sub-scanning mirror 22 is defined as a second system scanning unit 52.

  In the image display area 70, the first horizontal scanning line 51 draws the first horizontal line L1 with P-polarized light in the forward path of the first main scanning mirror 11 by the first system scanning unit 51, and then the second system scanning unit 52 performs the second scanning. On the forward path of the main scanning mirror 12, the second horizontal line L2 is drawn with S-polarized light. Then, the first horizontal scanning line 51 draws the third horizontal line L3 with P-polarized light in the return path of the first main scanning mirror 11 by the first system scanning unit 51, and then the return path of the second main scanning mirror 12 by the second system scanning unit 52. The fourth horizontal line L4 is drawn with S-polarized light. Thereafter, the same operation is periodically repeated from the upper part to the lower part of the image display area 70 to draw one frame image. Details of such multi-scanning will be described later.

  In the image display area 70, as described above, an image is drawn with S-polarized light and P-polarized light. Therefore, if the screen that is the image display area 70 is, for example, a polarizing screen, the brightness changes for each scanning line. Therefore, in such a case, the polarization state may be changed by a phase difference plate (not shown) disposed in the optical path between the polarization beam splitter 42 and the image display region 70. Specifically, a quarter-wave plate is disposed and P-polarized light and S-polarized light are converted into circularly polarized light, or a half-wave plate is disposed in one optical path to match the other polarization state. It is effective. Note that as the resolution is increased, the number of scanning lines increases, so the width of the scanning lines becomes relatively narrow, and the difference in brightness between the P-polarized light and the S-polarized light becomes inconspicuous.

  It should be noted that the first main scanning mirror 11 and the second main scanning mirror 12 have the same configuration, and when the common functions of the first main scanning mirror 11 and the second main scanning mirror 12 are described, the main scanning mirror 10 having the same configuration will be used hereinafter unless doubts arise. Will be described. Similarly, the first sub-scanning mirror 21 and the second sub-scanning mirror 22 have the same configuration, and when the common functions of the first sub-scanning mirror 21 and the second sub-scanning mirror 22 are described, the sub-scanning mirror having the same configuration will be used unless a doubt arises. 20 will be described.

  Here, the details of the scanning action of the scanning unit will be described with reference to FIGS.

  FIG. 2 is a main part configuration diagram of the main scanning mirror according to the first embodiment.

  As is clear from FIG. 2, the main scanning mirror 10 is provided with a mirror portion 101 made of a highly reflective member inside the support 107. The support 107 and the mirror unit 101 are connected by torsion springs 105 and 106 disposed on the same axis and facing each other with the mirror unit 101 interposed therebetween. The mirror unit 101 incorporates a coil 102 formed substantially parallel to the mirror surface 101a. In the vicinity of the mirror unit 101, permanent magnets 103 and 104 are provided at positions that are substantially symmetrical with respect to the torsion springs 105 and 106, respectively. The permanent magnets 103 and 104 generate a magnetic field substantially parallel to the mirror surface 101a when the main scanning mirror 10 is in a stationary state. When a current is passed through the coil 102, a Lorentz force in a direction substantially perpendicular to the mirror surface 101a is generated according to Fleming's left-hand rule.

  The mirror unit 101 rotates about an axis (hereinafter referred to as a horizontal rotation axis) 10a connecting the torsion spring 105 and the torsion spring 106 to a position where the Lorentz force and the restoring force of the torsion springs 105 and 106 are balanced. Move. By supplying an alternating current to the coil 102 at the resonance frequency of the mirror unit 101, the mirror unit 101 performs a resonance operation. Note that the driving force is not limited to electromagnetic force, and an electrostatic force or a configuration using a piezoelectric element may be used.

  FIG. 3 is an explanatory diagram of horizontal scanning and vertical scanning according to the first embodiment. FIG. 3A shows the horizontal scanning of the main scanning mirror in the horizontal direction of the main scanning mirror displayed in a straight line by omitting the sub-scanning mirror and further omitting the optical path folding. It is the top view seen from the parallel direction. FIG. 3B is a side view of the vertical scanning of the sub-scanning mirror in the image display region viewed from a direction parallel to the rotation axis of the sub-scanning mirror. In FIG. 3, for the convenience of explanation, local orthogonal coordinate axes at each point are introduced. That is, the direction corresponding to the horizontal direction which is the longitudinal direction in the image display area 70 is the X-axis direction, the direction corresponding to the vertical direction which is a short direction perpendicular to the X-axis direction is the Y-axis direction, and the image display area 70 method. The direction corresponding to the line direction is taken as the Z-axis direction.

  As described above, the main scanning mirror 10 performs horizontal scanning in the image display region 70, and the sub scanning mirror 20 performs vertical scanning. At this time, a horizontal scanning position (also referred to as a projection position) is obtained by Equation 1.

Scanning position X = L · tan β (Expression 1)
Here, L is a distance between the main scanning mirror 10 and the image display area 70, which is a so-called projection distance. The angle β is the swing angle of the main scanning mirror 10, and the mirror surface (hereinafter referred to as “reference surface”) S101 when the Lorentz force does not act on the mirror unit 101 and the amplitude of the resonance vibration of the mirror unit 101 is zero. With reference to the position, it refers to an angle formed by the vibrating mirror surface 101a with respect to the reference surface S101. This swing angle β is equal to the angle formed by the normal line of the main scanning mirror 10 and the Z axis.

  FIG. 4 is a diagram for explaining the relationship between the resonance vibration and the horizontal scanning angle in the main scanning mirror, and schematically shows the relationship between the swing angle β of the main scanning mirror 10 and the phase θ of the resonance vibration of the main scanning mirror 10. FIG.

  As is apparent from FIG. 4, the swing angle β changes according to resonance vibration, not equal intervals. If the swing angle of the main scanning mirror 10 is β, the distance from the center of rotation is r, the phase of the resonance vibration is θ, and the amplitude is A, Equation 2 is obtained.

r · sin β = A · sin θ (Expression 2)
Since β = βmax when θ = 90 degrees, Equation 3 is obtained by substituting A = r · sinβmax into Equation 2.

sin β = (sin βmax) sin θ (Equation 3)
Therefore, when drawing on an image display area 70 of 60 inches and an aspect ratio (aspect ratio) of 4: 3 at a projection distance L = 2.9 m, the resonance vibration amplitude sin θ and the horizontal direction of the resonance vibration phase θ Numerical data of tan β as the projection position is shown in Table 1, and corresponding figures are shown in FIGS.

  FIG. 5 is a diagram showing the amplitude of the resonance vibration sin θ, FIG. 6 is a diagram showing tan β relating to the projection position in the horizontal direction, and FIG. FIG.

  As is apparent from FIGS. 5 and 6, both sin θ and tan β have sinusoidal amplitudes at a swing angle βmax = ± 12 degrees corresponding to the horizontal scanning end. Further, as is apparent from FIG. 7, it can be seen that sin θ and tan β are in a substantially linear relationship. Therefore, it can be said from Equation 1 that the horizontal scanning position is proportional to sin θ, and sin θ represents the resonance vibration amplitude from Equation 3. As a result, it can be said that the horizontal scanning position in the image display area is proportional to the amplitude of the resonance vibration. That is, it was found that the amplitude of the resonance vibration represents the scanning position in the substantially horizontal direction.

  With the scanning method described above, the first system scanning unit 51 and the second system scanning unit 52 can scan the image display area 70 two-dimensionally, respectively, but in the first embodiment, as shown in FIG. For example, odd-numbered scanning lines (●: L1, L3, L5, L7,...) Scanned by the scanning unit and for example even-numbered scanning lines (■: L2, L4, L6, L8,...) Scanned by the second-system scanning unit. Each of the scanning units is driven so as to scan alternately. This switching of the scanning lines is performed by guiding laser light emitted from the light source unit 30 to the first system scanning unit 51 side by an optical path switching unit composed of the electro-optic modulator 41 and the polarization beam splitter 42, or Can be realized by guiding or switching to the second system scanning unit 52 side.

  Next, before describing the details of the driving method, which is the main part of the first embodiment, the basic configuration and problems of the conventional optical scanning method will be described, and the inventor newly noticed and reached the present invention. This will be described with reference to FIGS.

  FIG. 19 is a basic configuration diagram of an optical unit 900A of a conventional optical scanning apparatus having a main scanning mirror 10 as a horizontal scanning unit and a sub-scanning mirror 20 as a vertical scanning unit.

  In FIG. 19, the laser light emitted from the light source unit 30 enters the main scanning mirror 10 as a horizontal scanning unit through an AOM 60 that performs a modulation action according to an image signal. The laser beam that has been subjected to the horizontal scanning action by the main scanning mirror 10 is incident on the sub-scanning mirror 20 as a vertical scanning unit. Since the sub-scanning mirror 20 is driven to perform a vertical scanning action by the galvanometer 200, the laser light that has been subjected to the vertical scanning action by the sub-scanning mirror 20 is scanned two-dimensionally in the image display region 70. Is done. As described in FIG. 2 of Japanese Patent Laid-Open No. 2003-29182, as shown in the auxiliary diagram of FIG. 19, the amplitude of the main scanning mirror 10 changes in a sine wave shape. For example, if the amplitude of the main scanning mirror 10 is sin θ, Δ amplitude = 0.707 (approximately 70% of the image height) in the phase ranges of −45 degrees <θ <0 degrees and 0 degrees <θ <45 degrees, respectively. ) And an amplitude characteristic close to linear with respect to the phase change is obtained. However, in the phase ranges of 45 degrees <θ <90 degrees and 90 degrees <θ <135 degrees, the amplitude changes are returned at Δ amplitude = 0.293. Here, when the laser beam is irradiated at a constant interval, the irradiation position of the laser beam on the image display region 70 is as described above in the phase ranges of −45 degrees <θ <0 degrees and 0 degrees <θ <45 degrees. Thus, since it can be represented almost by the amplitude of the resonance vibration, it changes at almost equal intervals. However, in the phase range of 45 ° <θ <90 ° and 90 ° <θ <135 °, the interval between the projected images of the laser light is It becomes dense and uneven brightness occurs in the image display area 70.

  Therefore, if scanning is performed only in the phase range (outward path) of −45 degrees <θ <45 degrees excellent in linearity, the laser beam in the phase range of 45 degrees <θ <135 degrees cannot be used, so that it becomes dark. . Since the scanning is performed in a reciprocating manner, scanning is performed in the phase range (return path) of 135 degrees <θ <225 degrees after 180 degrees. Similarly, laser light is used in the phase range of 225 degrees <θ <315 degrees. Can not. That is, in this example, the laser beam can be effectively used only in half of the phase range (half time).

  In Japanese Patent Application Laid-Open No. 2003-29182, this problem is solved by using an f · θ lens that is easier to design than an arc sine lens. However, the f · θ lens is also in terms of size and manufacturing cost. I want to solve the problem without using it.

  Here, to summarize the main points of the problem, in order to make the pixel size formed by projecting the laser light constant, it is desired to use only a phase range having a good linearity in the amplitude of the sine wave. However, from the point of brightness, we want to make effective use of laser light in the entire phase range.

  As a method for solving this new problem, in the auxiliary diagram of FIG. 19, scanning in a phase range with good linearity in the amplitude of the sine wave (for example, −45 degrees <θ <45 degrees, 135 degrees <θ <225 degrees). After adding, add another sine wave with a more linear phase range (that is, replace it with a sine wave with another more linear phase range) and scan with that new sine wave. It is possible to realize scanning in a phase range with excellent characteristics. Since the sine wave is a repetitive function (periodic function) in which the amplitude is repeated every 360 degrees, if the above-described replacement of the sine wave can be realized, scanning with excellent linearity can be performed continuously by the repetition. This is the point of interest of the inventor.

  As described in the background art, since a large horizontal scanning frequency is required, if scanning is performed by reciprocal sinusoidal waves, scanning for one scanning line is basically 180 degrees in phase. In this 180 degree phase range, another sine wave is added, but in order to realize a state where not only a specific 180 degree range but also another sine wave is repeatedly added, it is added ( The sine wave to be replaced was also determined at the same frequency and a phase difference of 90 degrees.

  By the way, Japanese Patent Application Laid-Open No. 2006-201220 discloses a technique for instantaneously moving a laser beam scanning position from a scanning end position to a scanning start position in a two-dimensional scanning region. FIG. 20 is a basic configuration diagram of the optical unit 900B of the optical scanning device in the multi-scanning method, and FIG. 21 is an explanatory diagram of control signals.

  The laser beam emitted from the light source unit 30 is divided by the diffraction element 53 and guided to the first system scanning unit 51B and the second system scanning unit 52B, respectively.

  In the first system scanning unit 51B, the laser light is modulated by the first AOM 61 in accordance with the image signal. When the pulse signal of the first AOM 61 is ON, the laser beam reaches the first main scanning mirror 11 and undergoes a horizontal scanning action, and then receives a vertical scanning action by the first sub-scanning mirror 21, respectively. The image display area 70 is scanned two-dimensionally. The same applies to the second system scanning unit 52B.

  As shown in FIG. 21, the first system scanning unit 51B and the second system scanning unit 52B scan the first sub-scanning mirror 21 when the pulse signal of the first AOM 61 is ON, and conversely, the second AOM 62 The second sub-scanning mirror 22 is scanned when the pulse signal is ON, and the laser light is divided into two by the diffraction element in advance, so that only half the amount of the laser light can be used.

  Therefore, a technique for branching rather than dividing the laser beam is required. In contrast, by applying the “electro-optic modulator that synthesizes two laser beams with the same wavelength as linearly polarized light” disclosed in Japanese Patent Application Laid-Open No. 2006-95566, The inventor was able to realize the present invention.

  The main points of the present invention will be described below.

  As described above with reference to FIG. 1, the laser light can be switched between P-polarized light and S-polarized light by the electro-optic modulator 41. However, as shown in FIG. 1, a device for efficiently scanning P-polarized light and S-polarized light alternately is required.

  First, the amplitude X1 of the first main scanning mirror 11 that resonates and the amplitude X2 of the second main scanning mirror 12 are defined by equations 4 and 5.

X1 = sin θ (Expression 4)
X2 = sin (θ−α) (Equation 5)
Here, since the scanning is performed by reciprocal resonance vibration, the basic phase is 180 degrees. Another vibration is applied during the 180-degree phase, and the vibration has the same frequency and the phase difference can be determined as α = 180 degrees / 2 = 90 degrees.

  Accordingly, the scanning range of the point sequence obtained by correcting the phase range of −α / 2 <θ <α / 2 by the increment δ = α / n divided by the division number n is obtained by Equation 6. Here, since it is easier to understand when the number of point sequences to be scanned is smaller, an example in which the scanning range is divided into nine is shown in FIGS.

-Α / 2 + δ / 2 <θ <α / 2-δ / 2 (δ = α / n) (Equation 6)
Since δ = 90/9 = 10 degrees, −40 degrees <θ <40 degrees, and a step of 10 degrees is a scanning point sequence in the basic scanning range. In FIG. 8 that represents Equations 4 and 5 with a step δ = 10 degrees, Equation 4 has a sequence of points at almost equal intervals in the phase range of −40 degrees <θ <40 degrees, but 50 degrees <θ <. In the phase range of 130 degrees, the point sequence is closely arranged. On the other hand, focusing on Equation 5, the point sequence is dense in the phase range of −40 degrees <θ <40 degrees, but the point sequence is arranged at almost equal intervals in the phase range of 50 degrees <θ <130 degrees. I understand. In other words, by switching the amplitudes in Equations 4 and 5, scanning in a phase range with always excellent linearity can be realized.

  FIG. 9 is a diagram in which only the point sequence related to scanning is extracted from FIGS. In the forward path, one scan is performed at the number 4 (−40 degrees <θ <40 degrees), and then the next one scan is performed at the number 5 (50 degrees <θ <130 degrees). Then, in the return path, one scan is performed at Formula 4 (140 degrees <θ <220 degrees), and then the next scan is performed at Formula 5 (230 degrees <θ <310 degrees). It can be seen that by performing such scanning sequentially, scanning with excellent linearity is realized.

  Here, Table 2 compares the amplitudes of Formula 5 when the phase difference α in FIG. 9 is changed from 90 degrees to 91 degrees. When Equation 4 is used in the phase range of −40 degrees <θ <40 degrees and Equation 5 is similarly used in the phase range of 50 degrees <θ <130 degrees, the amplitude range of Equation 5 is shifted, but linearity It can be seen that even a phase difference deviating from 90 degrees can be applied. However, it is preferable to use a phase range with better linearity, and that the first system scanning unit 51 and the second system scanning unit 52 differ only in phase and can perform the same control.

  Here, in the case of scanning an image with an actual resolution SVGA (800 × 600 pixels), since δ = 90 / 800≈0.1 degrees, in the phase range of −44.9 degrees <θ <44.9 degrees. Scanning. Further, even when the resolution is high (n → ∞), scanning is performed up to a phase range of −45 degrees <θ <45 degrees. This is shown in FIG. Since the number of dot sequences is ∞, the scanning range is represented by a thick line.

  US Pat. No. 5,467,104 discloses a resonant mirror that performs horizontal scanning, having a frequency of several tens of kHz. The relationship between the horizontal frequency and the resolution will be described.

  In order to scan an image with a resolution of SVGA (800 × 600 pixels) at a vertical frequency of 60 Hz, scanning is performed at a resonance vibration frequency of 60 × 600/2 = 18 kHz or higher if scanning is performed in a reciprocating manner in the conventional scanning method. Is possible.

  On the other hand, since the present invention is a multi-scanning system that performs a plurality of scans in the same phase range, scanning is possible if the resonance frequency is 18 kHz / 2 = 9 kHz or more. In other words, even if the same resonance vibration frequency as in the prior art is used, the number of scanning lines in the vertical direction can be doubled, that is, scanning with a high resolution of twice can be performed.

  Finally, the scanning action using the vertical galvanometer will be described with reference to FIG. FIG. 11 is an explanatory diagram of vertical scanning according to the first embodiment. The diagram (a) shows the driving waveform of the first sub-scanning mirror, the diagram (b) shows the driving waveform of the second sub-scanning mirror, and the diagram (c) shows the driving waveform of the first sub-scanning mirror and the second sub-scanning mirror. Is also written.

  As shown in FIG. 11A, the first sub-scanning mirror 21 is DC-driven with a stepped waveform, so that the first sub-scanning mirror 21 is held at a predetermined angle at a thick line, Scanning in the horizontal direction by one main scanning mirror 11 is performed. Similarly, as shown in FIG. 11B, the second sub-scanning mirror 22 is DC-driven with a stepped waveform, so that the second sub-scanning mirror 22 is held at a predetermined angle at a thick line, In addition, horizontal scanning by the second main scanning mirror 12 is performed.

  As shown in FIG. 11C, the driving waveform of the first sub-scanning mirror 21 and the driving waveform of the second sub-scanning mirror 22 are the phase difference of one horizontal scanning line and the horizontal scanning line. Amplitudes differ by the vertical interval. In FIG. 11, the first sub-scanning mirror 21 and the second sub-scanning mirror 22 each give a predetermined amplitude so as to perform horizontal scanning at a portion where the amplitude is stable. If the state where the amplitude is unstable immediately after the movement is avoided, there is no problem even in the central portion of the same amplitude. In addition, the phase difference between the first sub-scanning mirror 21 and the second sub-scanning mirror 22 in the vertical direction is also different from the phase difference of one horizontal scanning line before the horizontal scanning. The sub-scanning mirror may be in time.

  In addition, the first sub-scanning mirror 21 and the second sub-scanning mirror 22 are driven by a substantially sawtooth (non-isosceles triangle) waveform signal, which corresponds to a scanning method in which vertical scanning is performed only in the forward path. . On the other hand, the effect of the present invention can also be obtained by a method of driving with a waveform signal having a substantially isosceles triangle shape, that is, scanning in a reciprocating manner in the vertical direction.

  Next, the operation including the control method will be described again with reference to FIG. FIG. 12 is a block diagram of a main part of the optical scanning device according to the first embodiment.

  As shown in FIG. 12, the optical scanning device 90 includes an optical unit 900, a laser control unit 910, a scanning control unit 920, a polarization control unit 930, and an image signal 940.

  The laser control unit 910 includes a drawing control unit 911 and a laser modulation control unit 912. In the laser control unit 910, the drawing control unit 911 performs drawing control of R, G, B, etc. based on the image signal 940, and the laser modulation control unit 912 based on a synchronization signal from a scanning control unit 920 described later. The AOM 60 of the optical unit 900 is controlled.

  The scanning control unit 920 includes a drive waveform generation unit 921, a synchronization signal generation unit 922, a main demultiplexing unit 923, and a sub demultiplexing unit 924.

  Based on the drive waveform generated by the drive waveform generation unit 921, the scanning control unit 920 includes a main branching unit 923 as a horizontal phase difference control unit using resonance vibration, and a vertical phase difference control unit using DC drive. The sub-demultiplexing unit 924 is controlled. That is, the horizontal scanning of the first main scanning mirror 11 and the second main scanning mirror 12 is controlled by the waveform signal of the resonance vibration having a phase difference of about 90 degrees generated by the main branching unit 923. Further, in synchronization with the horizontal scanning of the first main scanning mirror 11 and the second main scanning mirror 12, the phase difference generated by the sub-demultiplexing unit 924 is changed to the first by the waveform signal of the DC drive for one horizontal scanning line. The sub-scanning mirror 21 and the second sub-scanning mirror 22 are controlled. At the same time, a synchronization signal is sent from the synchronization signal generation unit 922 to the laser modulation control unit 912 and the polarization control unit 930 based on the signal of the drive waveform generation unit 921.

  In response to the synchronization signal from the synchronization signal generation unit 922, the laser modulation control unit 912 causes the AOM 60 to perform modulation. The polarization controller 930 controls the switching (conversion) of the polarization state of the light from the light source unit 30 with respect to the electro-optic modulator 41, guides the laser light to the first system scanning unit 51 side, The light guide to the second system scanning unit 52 is switched.

  Since the operation of the optical unit 900 has already been described, the description thereof is omitted here.

  As described above, in the optical scanning device according to the first embodiment, every time the phase of the resonance vibration of the first main scanning mirror 11 and the second main scanning mirror 12 changes by about 90 degrees, the first system scanning unit 51 The scanning is switched between the second system scanning unit 52 and the second system scanning unit 52.

  As a result, a phase range with good linearity (for example, −45 degrees to 45 degrees, 135 degrees to 135 degrees) with reference to the phase when the resonance vibration amplitude of each main scanning mirror is zero (when the Lorentz force is not acting). Each system scanning section can perform scanning within a range of 225 degrees or the like.

  Therefore, unlike the conventional example, a projection optical system having, for example, an f · θ lens is not used while a good image without distortion is realized, so that the size of the optical scanning device can be reduced and the cost can be reduced. it can.

  Further, in the first embodiment, the light from the light source unit is scanned in the first system alternately by using an optical path switching unit composed of an electro-optic modulator 41 and a polarization beam splitter 42 using the property of polarization. Branching to the scanning side and the second system scanning unit side. Therefore, unlike the prior art, the light utilization efficiency is excellent.

  FIG. 13 shows a basic configuration of an image display device 80 using the optical scanning device 90 according to the first embodiment. Based on the image signal 940, the laser light emitted from the optical scanning device 90 passes through the emission window 850 and is scanned two-dimensionally into the image display region 70. The exit window 850 has a hermetically sealed structure such as a glass plate in order to prevent dust and the like from entering from the laser beam exit section and accumulating on the mirror surface of the scanning mirror.

  In the first embodiment described above, the main scanning mirror and the sub-scanning mirror are disposed separately, but the present invention is not limited to this. Although common to other embodiments described later, the optical scanning device can be configured with a simpler structure by structurally integrating the main scanning mirror and the sub-scanning mirror. Specifically, when the resolution becomes high, the horizontal scanning frequency needs to be increased. Therefore, in order to increase the resonance frequency of the main scanning mirror, if the main scanning mirror is reduced, the resonance vibration structure itself of the main scanning mirror is fixed to the vibration part of the galvanometer, thereby An integral structure is possible.

Further, for example, a MEMS (Micro Electro Mechanical System) mirror capable of two-dimensional scanning can be used. If the vertical direction is also resonant vibration, the trajectory of the beam becomes sinusoidal. However, during the scanning of one horizontal scanning line, the distance is moved in the vertical direction. For example, 4 × 3 mm In the case of SVGA, the gradient is tan ⁻¹ (3/600/4) = 0.07 degrees. Here, 3% of TV distortion obtained by standardizing the value of ΔY = 3/600 with a reference length of 3 mm is a large value for TV use, but is a value applicable to a portable display. Further, in the future, by further increasing the resolution (for example, 768 XGA), this TV distortion will be reduced. Therefore, driving using vibration such as resonance vibration to the vertical sub-scanning unit can be applied. Become.

  In the above description, the meanings of the horizontal direction and the vertical direction basically mean the longitudinal direction and the short direction of the image in the image display area, respectively. The long direction and the short direction generally correspond to the horizontal direction and the vertical direction of the image, respectively.

  The meaning of this explanation is that it is possible to replace the correspondence between the scanning direction in the scanning unit and the scanning direction in the image display region by arranging an optical path bending mirror between the scanning unit and the image display region. It is. Further, depending on the display application other than the TV application, there is a vertically long image display area.

  Next, Example 2 will be described with reference to FIG.

  FIG. 14 is a basic configuration diagram of a multi-scan method according to the second embodiment. The difference from the first embodiment is that the vertical scanning is performed by the sub-scanning mirror and then the horizontal scanning is performed by the main scanning mirror.

  Since the area of the scanning mirror surface is smaller when scanning first, and the area of the scanning mirror is larger when scanning later, the main scanning section that performs resonance vibration that vibrates at high speed is usually arranged first. Is more advantageous. However, when the resolution performance for scanning is low, it is necessary to reduce the resonance frequency (also referred to as the natural frequency) for the resonance vibration. Therefore, it is necessary to make the resonance mirror large to some extent. Two configurations are applicable.

  Next, Example 3 which is a modification of Example 1 will be described with reference to FIG.

  FIG. 15 is a diagram illustrating the arrangement of main scanning mirrors according to the third embodiment. The (a) figure is a top view seen from the direction parallel to the horizontal rotation axis | shaft of a main scanning mirror, (b) figure is sectional drawing along the AA line in (a) figure. In the third embodiment, the first main scanning mirror 11 and the second main scanning mirror 12 are arranged so that the traveling directions of the P-polarized light and the S-polarized light are the same without using the reflection mirror 43 of the first embodiment. It is a devised one.

  In FIG. 15, if the angle γ formed by the reference plane when the resonance vibration amplitude of the first main scanning mirror 11 is zero and the reference plane of the second main scanning mirror 12 is about 135 degrees, each main scanning mirror The rays reflected by can be made parallel to each other. As a result, the reflection mirror 43 can be deleted, and the cost can be reduced compared to the first embodiment.

  Next, Example 4 will be described with reference to FIGS.

  FIG. 16 shows the configuration of the main part of a three-branch optical path switching unit according to the fourth embodiment.

  As shown in FIG. 16, the optical path switching unit according to the fourth embodiment includes two sets of the optical path switching units according to the first embodiment including the electro-optic modulator 41 and the polarization beam splitter 42. That is, the configuration is such that the original laser beam is branched into three by performing optical path switching using polarized light in two stages. Specifically, the optical path of the S-polarized light and the P-polarized light is branched by the first optical path switching unit, and the optical path of the P-polarized light is further changed to the optical path of the S-polarized light and the P-polarized light by the optical path switching unit in the next stage. The light is branched and the result is branched into three optical paths. The reflection mirror 43 is for making the three branched light paths parallel. Although not shown in the figure, in the same manner as in the first embodiment, a half-wave plate is provided to increase the resolution by converting the polarization direction of the light transmitted through the second set of polarization beam splitters by 90 degrees. Since the number of scanning lines increases, the width of the scanning lines becomes relatively narrow, and the difference in brightness between P-polarized light and S-polarized light becomes inconspicuous. Further, it goes without saying that the same effect can be obtained even if a quarter plate is provided for each of the three branched optical paths.

  The phase difference in the case of the three branches will be described with reference to FIG. FIG. 17 is an explanatory diagram of a phase difference in horizontal scanning according to the fourth embodiment.

  In the description of the first embodiment, the phase difference of 90 degrees is obtained by dividing 180 degrees by 2 in the case of two branches, but the phase difference of 60 degrees is obtained by dividing 180 degrees by 3 in the case of three branches. Therefore, since the basic phase range is half of 60 degrees and ± 30 degrees, the amplitude sin30 = 0.5 is half of the maximum amplitude, and only a range with better linearity can be used.

  Accordingly, FIG. 18 shows a relationship diagram between sin θ and tan β at βmax = ± 34 degrees corresponding to horizontal scanning of the image display area 70 with a projection distance L = 0.9 m and an aspect ratio of 4: 3. As is clear from FIG. 18, the linearity of sin θ and tan β is deteriorated as compared with FIG. 7, but in Example 4 with three branches, the amplitude to be used is half (0.5) of the maximum amplitude. Scanning in a range with excellent linearity is possible.

It is a basic block diagram of the optical part which shows Example 1 of a multi-scanning system. FIG. 3 is a main part configuration diagram of a main scanning mirror according to Embodiment 1; 3 is an explanatory diagram of horizontal scanning and vertical scanning according to the first embodiment. FIG. FIG. 6 is a relationship diagram between resonance vibration and horizontal scanning angle in the main scanning mirror. It is a figure which shows amplitude sin (theta) of resonance vibration. It is a change figure of a projection position. FIG. 6 is a relationship diagram between resonance vibration and a horizontal scanning position. It is explanatory drawing of the point row | line | column used as the origin of odd-numbered 9 division | segmentation of a horizontal scanning range. It is explanatory drawing of the scanning point row | line | column in odd-numbered 9 division of a horizontal scanning range. It is a conceptual diagram of the scanning point sequence in the ∞ division of the horizontal scanning range. FIG. 6 is an explanatory diagram of vertical scanning according to the first embodiment. 1 is a block diagram of a main part of an optical scanning device according to Embodiment 1. FIG. 1 is a basic configuration diagram of an optical scanning device and an image display device according to Embodiment 1. FIG. FIG. 5 is a basic configuration diagram of a multi-scan method according to a second embodiment. FIG. 10 is a diagram illustrating the arrangement of main scanning mirrors according to a third embodiment. 4 is a main configuration of three branches according to a fourth embodiment. It is explanatory drawing of the phase difference of the horizontal scanning by Example 4. FIG. FIG. 10 is a relationship diagram between resonance vibration and horizontal scanning position according to the fourth embodiment. It is a basic block diagram of the optical part of the conventional optical scanning device. It is a basic block diagram of the conventional multi-scanning system. It is explanatory drawing of the control signal in the conventional multi-scan system.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Main scanning part, 2 ... Sub scanning part, 10 ... Main scanning mirror, 10a ... Horizontal rotation axis, 11 ... 1st main scanning mirror, 12 ... 2nd main scanning mirror, 20 ... Sub scanning mirror, 21 ... 1st DESCRIPTION OF SYMBOLS 1 subscanning mirror, 22 ... 2nd subscanning mirror, 30 ... Light source part, 41 ... Electro-optic modulator, 42 ... Polarizing beam splitter, 43 ... Reflection mirror, 51 ... 1st system scanning part, 52 ... 2nd system scanning , 53 ... Diffraction grating, 60 ... AOM, 61 ... First AOM, 62 ... Second AOM, 70 ... Image display area, 80 ... Image display device, 90 ... Optical scanning device, 101 ... Mirror unit, 101a ... Mirror surface, S101 Reference plane, 102, coil, 103, 104 ... permanent magnet, 105, 106 ... torsion spring, 107 ... support, 200 ... galvanometer, 201 ... first galvanometer, 202 ... second galvanometer, 850 Exit window, 900 ... Optical unit, 910 ... Laser control unit, 911 ... Drawing control unit, 912 ... Laser modulation control unit, 920 ... Scanning control unit, 921 ... Drive waveform generation unit, 922 ... Synchronization signal generation unit, 923 ... Horizontal Direction demultiplexing unit (phase difference control unit), 924... Vertical direction demultiplexing unit (phase difference control unit), 930... Polarization control unit, 940.

Claims (14)

An image display device that projects light onto a screen,
A light source that emits light;
An acousto-optic modulator that modulates light intensity of the light from the light source in accordance with an image signal;
An electro-optic modulator that converts the polarization direction of light from the acousto-optic modulator into a first polarization direction or a second polarization direction;
A polarization beam splitter that transmits light having the first polarization direction and reflects light having the second polarization direction out of light from the electro-optic modulator;
A first main scanning unit that scans light having the first polarization direction transmitted through the polarization beam splitter in a horizontal direction of the screen;
A second main scanning unit that scans light having the second polarization direction reflected by the polarization beam splitter in a horizontal direction of the screen;
A first sub-scanning unit that scans light scanned by the first main scanning unit in a vertical direction of the screen;
A second sub-scanning unit that scans light scanned by the second main scanning unit in a vertical direction of the screen;
The electric polarization direction of the light is switched after the first main scanning unit is scanned once, and the electric polarization direction of the light is switched after the second main scanning unit is scanned once. An image display device comprising a control unit for controlling an optical modulator. The image display device according to claim 1,
The image display apparatus, wherein the light source is a semiconductor laser or an LED. The image display device according to claim 1,
An image display, wherein a reflection mirror that reflects light is disposed between the polarizing beam splitter and the first sub-scanning unit, or between the polarizing beam splitter and the second sub-scanning unit. apparatus. The image display device according to claim 1,
The reference plane of the first main scanning section and the reference plane of the second main scanning section are formed when the amplitude of resonance vibration of the first main scanning section and the second main scanning section is zero. An image display device characterized in that the angle is about 135 degrees. The image display device according to claim 1,
The phase difference between the driving waveform of the first main scanning unit and the driving waveform of the second main scanning unit is set to about 90 degrees, and the first main scanning unit and the second main scanning unit are An image display device comprising a main branching unit that is driven at substantially the same frequency. The image display device according to claim 5,
The phase difference between the driving waveform of the first sub-scanning unit and the driving waveform of the second sub-scanning unit is a phase difference that the first or second main scanning unit scans once in the horizontal direction. An image display device comprising a sub-demultiplexing unit to be driven. The image display device according to claim 6,
Each of the first sub-scanning unit and the second sub-scanning unit is a galvanometer. The image display device according to claim 1,
The image display apparatus according to claim 1, wherein the first main scanning unit and the first sub-scanning unit are integrated MEMS mirrors. The image display device according to claim 1,
The image display apparatus, wherein the second main scanning unit and the second sub-scanning unit are an integral MEMS mirror. The image display device according to claim 1,
A half-wave plate between the polarizing beam splitter and the projection surface of the screen, either on the optical path of light having the first polarization direction or on the optical path of light having the second polarization direction An image display device characterized by the arrangement. The image display device according to claim 1,
A quarter-wave plate is disposed between the polarizing beam splitter and the projection surface of the screen and on the optical path of the light having the first polarization direction and on the optical path of the light having the second polarization direction. An image display device characterized by that. An image display device that projects light onto a screen,
A light source that emits light;
An acousto-optic modulator that modulates light intensity of the light from the light source in accordance with an image signal;
A first electro-optic modulator that converts a polarization direction of light from the acousto-optic modulator into a first polarization direction or a second polarization direction;
A first polarization beam splitter that transmits light having the first polarization direction out of light from the first electro-optic modulator and reflects light having the second polarization direction;
A second electro-optic modulator that converts a polarization direction of light transmitted through the first polarization beam splitter into a first polarization direction or a second polarization direction;
A second polarization beam splitter that transmits light having the first polarization direction out of light from the second electro-optic modulator and reflects light having the second polarization direction;
A first main scanning unit that scans light having the second polarization direction reflected by the first polarization beam splitter in a horizontal direction of the screen;
A second main scanning unit that scans light having the first polarization direction transmitted through the second polarization beam splitter in a horizontal direction of the screen;
A third main scanning unit that scans light having the second polarization direction reflected by the second polarization beam splitter in a horizontal direction of the screen;
A first sub-scanning unit that scans light scanned by the first main scanning unit in a vertical direction of the screen;
A second sub-scanning unit that scans light scanned by the second main scanning unit in a vertical direction of the screen;
A third sub-scanning unit that scans light scanned by the third main scanning unit in a vertical direction of the screen;
After the first main scanning unit is scanned once, the polarization direction of the light is switched, and after the second main scanning unit is scanned once, the polarization direction of the light is switched, and the first An image display apparatus comprising: a control unit that controls the first and second electro-optic modulators so as to switch a polarization direction of the light after the three main scanning units are scanned once. The image display device according to claim 12,
The phase difference between the driving waveform of the first main scanning unit, the driving waveform of the second main scanning unit, and the third main scanning unit is set to about 60 degrees, and the first, second, and An image display device comprising: a main branching unit that drives the third main scanning unit at substantially the same frequency. The image display device according to claim 13,
An image display device, wherein a half-wave plate is disposed on an optical path transmitted through the second polarizing beam splitter.

Images