Optical modules and projectors

Abstract

We provide optical modules and projectors that can reduce speckle noise. [Solution] The optical module of the present invention comprises a light source including a first light-emitting unit that emits first light of a first wavelength, an optical scanning unit that scans the light emitted from the light source, and an optical modulation unit that modulates the scanned light from the optical scanning unit based on image information. The optical scanning unit uses an optical element that rotates around a rotation axis extending in a direction intersecting the direction of light incidence to change the optical path length of the scanned light incident at the same position in the optical modulation unit to be greater than or equal to the coherence length of the first light.

Description

Technical Field

[0001] The present invention relates to an optical module and a projector.

Background Art

[0002] As a light source device used in a projector, a light source device that illuminates a light modulation device by temporally scanning light emitted from a light emitting element on a light modulation device such as a liquid crystal panel has been proposed.

[0003] Patent Document 1 below discloses a projector including a light source device, a liquid crystal light valve, a polygon mirror provided between the light source device and the liquid crystal light valve, and a projection lens. In this projector, the polygon mirror reflects the light emitted from the light source device and scans it in the short-axis direction of the elliptical light beam cross section on the image formation region of the liquid crystal light valve.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the above projector, when a highly coherent light source such as a laser diode is used as the light source device, the scanned lights may interfere with each other and may be visually recognized as speckle noise.

Means for Solving the Problems

[0006] To solve the above problems, according to one aspect of the present invention, an optical module is provided comprising: a light source unit including a first light-emitting element that emits first light of a first wavelength; an optical scanning unit that scans the light emitted from the light source unit; and an image light generation unit that generates image light from the scanning light by the optical scanning unit, wherein the optical scanning unit changes the optical path length of the scanning light incident on the same point on the image light generation unit to be greater than or equal to the coherence length of the first light by an optical element that rotates about a rotation axis extending in a direction intersecting the direction of incidence of the light.

[0007] Furthermore, according to another aspect of the present invention, a projector is provided comprising an optical module as described above and a projection optical device that projects light emitted from the optical module. [Brief explanation of the drawing]

[0008] [Figure 1] This is a plan view showing the schematic configuration of the projector according to the first embodiment. [Figure 2] This diagram shows the configuration of the green light-emitting section. [Figure 3] This diagram shows the configuration of the green light-emitting section. [Figure 4A] This figure shows the behavior of green light when a transmissive optical element rotates. [Figure 4B] This figure is a continuation of Figure 4A. [Figure 4C] This figure is a continuation of Figure 4B. [Figure 4D] This figure is a continuation of Figure 4C. [Figure 4E] This figure is a continuation of Figure 4D. [Figure 5] This is a cross-sectional view of the light modulation section. [Figure 6] This diagram shows how transmitted light from a transmitted optical element is incident on the same position in the optical modulation section. [Figure 7] This is a plan view showing the main components of the image module of the second embodiment. [Figure 8] This diagram shows how reflected light is incident on the same location in the light modulation section. [Figure 9]This is a plan view showing the main components of the image module of the third embodiment. [Figure 10] This diagram shows how reflected light is incident on the same location in the light modulation section. [Figure 11] This diagram shows the configuration of the optical scanning unit according to a modified example of the third embodiment. [Modes for carrying out the invention]

[0009] Embodiments of the present invention will be described below with reference to the drawings. In the following drawings, the dimensions of each component may be shown on a different scale to make them easier to see.

[0010] (First Embodiment) Figure 1 is a plan view showing the schematic configuration of the projector according to this embodiment. As shown in Figure 1, the projector 1 of this embodiment comprises an image module 2 and a projection optical device 3. In this embodiment, the image module 2 corresponds to the "optical module" of the present invention.

[0011] The image module 2 comprises a light source 20, an optical scanning unit 21, and an optical modulation unit 22. The light source 20 includes a blue light-emitting unit 20B, a green light-emitting unit 20G, a red light-emitting unit 20R, a first reflecting element 17, and a second reflecting element 18. The optical scanning unit 21 has a transmissive optical element 14 and a rotational drive device 15. The optical modulation unit 22 has a liquid crystal panel 23 and an output polarizing plate 24.

[0012] In the following description, an XYZ orthogonal coordinate system is used as necessary. The X-axis is an axis parallel to the optical axis AX2 of the green light-emitting unit 20G. The optical axis AX2 of the green light-emitting unit 20G is defined as an axis along the principal ray of the green light LG emitted from the green light-emitting unit 20G. The Y-axis is an axis orthogonal to the X-axis and is an axis along the rotation axis C1 of the optical scanning unit 21. The Z-axis is an axis orthogonal to the X-axis and the Y-axis and is an axis parallel to the optical axis AX1 of the blue light-emitting unit 20B and the optical axis AX3 of the red light-emitting unit 20R. The optical axis AX1 of the blue light-emitting unit 20B is defined as an axis along the principal ray of the blue light LB emitted from the blue light-emitting unit 20B. The optical axis AX3 of the red light-emitting unit 20R is defined as an axis along the principal ray of the red light LR emitted from the red light-emitting unit 20R. That is, the optical axis AX1 of the blue light-emitting unit 20B and the optical axis AX3 of the red light-emitting unit 20R are located on the same axis. The optical axis AX2 of the green light-emitting unit 20G is orthogonal to the optical axis AX1 of the blue light-emitting unit 20B and the optical axis AX3 of the red light-emitting unit 20R.

[0013] The blue light-emitting unit 20B emits, for example, blue light LB having a central wavelength in a blue wavelength band of 450 nm, 450 nm ± 5 nm. The green light-emitting unit 20G emits, for example, green light LG having a central wavelength in a green wavelength band of 530 nm, 530 nm ± 5 nm. The red light-emitting unit 20R emits, for example, red light LR having a central wavelength in a red wavelength band of 650 nm, 650 ± 5 nm. The blue light-emitting unit 20B corresponds to the "first light-emitting unit" of the present invention, and the blue light LB corresponds to the "first light of the first wavelength" of the present invention. Further, the red light-emitting unit 20R corresponds to the "second light-emitting unit" of the present invention, and the red light LR corresponds to the "second light of the second wavelength" of the present invention.

[0014] The blue light-emitting unit 20B emits blue light LB toward the optical scanning unit 21. The green light-emitting unit 20G emits green light LG toward the optical scanning unit 21. The red light-emitting unit 20R emits red light LR toward the optical scanning unit 21.

[0015] Although the basic configurations of each light-emitting unit 20B, 20G, and 20R are similar, Figures 2 and 3 show the detailed configuration of the green light-emitting unit 20G. Therefore, the following explanation will use Figures 2 and 3 as an example to describe the configuration of the green light-emitting unit 20G.

[0016] As shown in Figures 2 and 3, the green light-emitting section 20G comprises a plurality of green light-emitting elements 26 and a substrate 29. Each green light-emitting element 26 is composed of a laser diode that emits a light ray LG0 in the green wavelength band. Therefore, the light ray LG0 emitted from the green light-emitting elements 26 is linearly polarized with coherence, has a narrow beam width, and is coherent light with high parallelism.

[0017] Multiple green light-emitting elements 26 are arranged in a row along the Y-axis direction, with predetermined intervals between them. In this embodiment, the green light-emitting section 20G is equipped with five green light-emitting elements 26, but the number of green light-emitting elements 26 is not particularly limited, and it is sufficient for multiple green light-emitting elements 26 to be arranged in a row along the Y-axis direction.

[0018] In this embodiment, since a light ray LG0 is emitted from each of the five green light-emitting elements 26, the green light LG emitted from the green light-emitting section 20G is the entire luminous beam containing the five light rays LG0. For this reason, the cross-sectional shape of the green light LG perpendicular to the principal ray is a band shape having a major axis extending along the Y-axis and a minor axis extending along the Z-axis.

[0019] The substrate 29 supports a plurality of green light-emitting elements 26. Although not shown in the figures, a heat sink for cooling the plurality of green light-emitting elements 26 may be provided on the side of the substrate 29 opposite to the side on which the plurality of green light-emitting elements 26 are provided.

[0020] As shown in Figure 1, the blue light-emitting section 20B comprises a plurality of blue light-emitting elements 25 and a substrate 29. The blue light-emitting elements 25 are composed of laser diodes that emit light rays LB0 in the blue wavelength band. Therefore, the light rays LB0 emitted from the blue light-emitting elements 25 are linearly polarized with coherence, have a narrow beam width, and are coherent light with high parallelism.

[0021] Multiple blue light-emitting elements 25 are arranged in a row along the Y-axis direction, with predetermined intervals between them. In this embodiment, the blue light-emitting section 20B is equipped with five blue light-emitting elements 25, but the number of blue light-emitting elements 25 is not particularly limited, and it is sufficient for multiple blue light-emitting elements 25 to be arranged in a row along the Y-axis direction.

[0022] The red light-emitting section 20R comprises a plurality of red light-emitting elements 27 and a substrate 29. The red light-emitting elements 27 are composed of laser diodes that emit light rays LR0 in the red wavelength band. Therefore, the light rays LR0 emitted from the red light-emitting elements 27 are linearly polarized with coherence, have a narrow beam width, and are coherent light with high parallelism.

[0023] Multiple red light-emitting elements 27 are arranged in a row along the Y-axis direction at predetermined intervals from each other. In this embodiment, the red light-emitting section 20R is equipped with five red light-emitting elements 27, but the number of red light-emitting elements 27 is not particularly limited, and it is sufficient for multiple red light-emitting elements 27 to be arranged in a row along the Y-axis direction.

[0024] The optical scanning unit 21 scans the light emitted from the light source 20. The transmissive optical element 14 is positioned where the optical axes AX1 and AX3 intersect with the optical axis AX2. The transmissive optical element 14 is made of a light-transmitting material such as optical glass such as BK7, quartz, or resin. The transmissive optical element 14 is rotatable about a rotation axis C1 that extends along the Y-axis. The rotation axis C1 is connected to a rotary drive device 15 consisting of a motor or the like. The transmissive optical element 14 rotates about the rotation axis C1 by the drive of the rotary drive device 15.

[0025] As shown in Figure 3, the transmissive optical element 14 has a first surface 14a and a second surface 14b that intersect the rotation axis C1, and four sides 14c1, 14c2, 14c3, and 14c4 that are perpendicular to the first surface 14a and the second surface 14b. That is, the shape of the transmissive optical element 14 is a quadrangular prism having six planes, including the first surface 14a, the second surface 14b, and the four sides 14c1, 14c2, 14c3, and 14c4. Hereinafter, sides 14c1 and 14c3 may be referred to as the first sides 14c1 and 14c3, and sides 14c2 and 14c4 as the second sides 14c2 and 14c4.

[0026] The first surfaces 14c1 and 14c3 have equal areas and are two parallel surfaces. The second surfaces 14c2 and 14c4 have equal areas and are two parallel surfaces. In a plane perpendicular to the rotation axis C1, the dimension S1 of the first side surfaces 14c1 and 14c3 is different from the dimension S2 of the second side surfaces 14c2 and 14c4. In this embodiment, dimension S1 is larger than dimension S2. In other words, the cross-sectional shape of the transmitted optical element 14 when cut by a plane perpendicular to the rotation axis C1 is rectangular.

[0027] In this specification, when referring to the two sides of the transmissive optical element 14 being parallel to each other, "parallel" refers to a case where the angle between the two sides is in the range of 0 ± 5 degrees, taking into consideration the processing accuracy of the glass material constituting the light-transmitting member, the allowable range of parallelism of light, etc.

[0028] The transmissive optical element 14 rotates around the rotation axis C1, transmitting the blue light LB, green light LG, and red light LR emitted from each of the light-emitting parts 20B, 20G, and 20R. Therefore, the side from which the light LB, LG, and LR of each color emitted from each of the light-emitting parts 20B, 20G, and 20R enter the transmissive optical element 14 is not fixed, but changes over time. In the transmissive optical element 14, the side from which the light LB, LG, and LR of each color emitted from each of the light-emitting parts 20B, 20G, and 20R enters is called the incident surface. The side from which the light LB, LG, and LR entering from the incident surface are emitted is called the exit surface. In this case, the incident surface and the exit surface change over time and are one of two parallel sides from among the four sides 14c1, 14c2, 14c3, and 14c4. In other words, in the transmissive optical element 14 of this embodiment, the incident surface and the exit surface are at least one of the two first sides 14c1, 14c3 and the two second sides 14c2, 14c4.

[0029] As shown in Figure 1, the blue light LB is incident on the first position P1 of the transmissive optical element 14. The green light LG is incident on the second position P2 of the transmissive optical element 14, which is different from the first position P1. The red light LR is incident on the third position P3 of the transmissive optical element 14, which is different from the first position P1 and the second position P2. In other words, the blue light LB, green light LG, and red light LR are incident on different positions of the transmissive optical element 14. In particular, in this embodiment, since each light-emitting unit 20B, 20G, and 20R is in a positional relationship rotated by 90 degrees around the intersection of optical axes AX1 and AX3 and optical axis AX2, the blue light LB, green light LG, and red light LR are incident on different sides of the transmissive optical element 14.

[0030] In this embodiment, the transmissive optical element 14 has four sides, but the number of sides does not necessarily have to be four; it is preferable that there be 2 × m (m: a natural number greater than or equal to 2). That is, the number of sides can be an even number, such as 6 or 8. If the number of sides is even, each of the sides is parallel to the side opposite it, and there are no non-parallel sides. As a result, the generation of stray light in the transmissive optical element 14 is reduced, and the light utilization efficiency can be increased.

[0031] For example, if there are six sides, the six sides will consist of two parallel first sides and two parallel second sides. Since the dimensions of the first and second sides are different, the cross-sectional shape of the transmitted optical element will be a deformed hexagon rather than a regular hexagon. The deformation of the hexagon must be set to such an extent that light incident from one of two opposing sides is emitted from the other side.

[0032] The transmissive optical element 14 may be made of quartz. In the transmissive optical element 14, as the amount of light transmitted through the translucent member increases, the amount of light absorbed by the translucent member also increases, which may cause thermal distortion in the translucent member. In this case, the polarization direction of the respective color lights LB, LG, and LR emitted from each light-emitting part 20B, 20G, and 20R becomes disordered, and the linearly polarized light incident on the translucent member becomes elliptically polarized light and is emitted from the translucent member. As a result, the effect of obtaining a predetermined contrast without providing an incident polarizer by using laser diodes in each light-emitting element in the projector 1 is not obtained. That is, even though laser diodes are used in each light-emitting element, it becomes necessary to use an incident polarizer to align the polarization direction. Therefore, in order to obtain the above effect, it is desirable to use a glass material with a large Young's modulus and a small coefficient of thermal expansion as a glass material with low thermal distortion, and as an example, it is desirable to use quartz.

[0033] The behavior of each color light LB, LG, and LR as they pass through the transmitting optical element 14 will be described below. Although the incident and emission directions of each color light LB, LG, and LR are different, their behavior is common to each other. Therefore, the explanation will use the green light LG emitted from the green light-emitting section 20G.

[0034] Figures 4A to 4E are schematic diagrams illustrating the behavior of the green light LG as the transmissive optical element 14 rotates. In this example, viewed from the +Y side, the transmissive optical element 14 rotates clockwise around the rotation axis C1, and the diagrams show the progression of time from Figure 4A to Figure 4E.

[0035] In Figures 4A to 4E, the rotation angle ω of the transmitting optical element 14 is defined as the angle between the optical axis AX2 and the straight line M that passes through the rotation axis C1 and connects the intersection points of the sides 14c1 and 14c4 of the transmitting optical element 14 to the rotation axis C1. In reality, the green light LG has a predetermined luminous flux width in the Z-axis direction, but here we will focus on the behavior of the light ray LG0 traveling along the optical axis AX2.

[0036] Figure 4A shows that the rotation angle ω of the transmitted optical element 14 is 0 degrees, and the light ray LG0 is on the side surface 14c1. The ray LG0 enters the end on the side connecting to the side 14c4. At this time, the ray LG0 is refracted in the direction shown in the figure (-Z side) and travels inside the transparent optical element 14. Next, the ray LG0 is also incident on the side 14c3 at a predetermined angle of incidence, so it is refracted at the side 14c3 and emitted from the transparent optical element 14. At this time, since the side 14c1 and the side 14c3 are parallel to each other, the angle of incidence of the ray LG0 with respect to the side 14c1 is equal to the angle of incidence of the ray LG0 with respect to the side 14c3, and the angle of refraction of the ray LG0 incident on the side 14c1 and the angle of refraction of the ray LG0 emitted from the side 14c3 have opposite signs but equal absolute values. As a result, the angle of refraction of the ray LG0 when it enters the side 14c1 and the angle of refraction when it is emitted from the side 14c3 cancel each other out. As a result, the ray LG0 travels parallel to the optical axis AX2 at a position displaced by an amount d toward the -Z side from the optical axis AX2. Note that when the rotation angle ω is 0 degrees, the amount d of the displacement of the ray LG0 toward the -Z side is maximum.

[0037] Next, as shown in Figure 4B, when the rotation angle ω of the transmission optical element 14 becomes larger than that in Figure 4A, the incident angle of the light ray LG0 decreases, and the refraction angle decreases. Therefore, the displacement d of the light ray LG0 from the optical axis AX2 becomes smaller than in Figure 4A. Also, the state in which the light ray LG0 travels parallel to the optical axis AX2 is always maintained. From the rotation angle ω from 0 degrees to the state shown in Figure 4C, the displacement d decreases monotonically with increasing rotation angle ω.

[0038] Next, as shown in Figure 4C, when the rotation angle ω of the transmissive optical element 14 is approximately 45 degrees, the light ray LG0 is incident perpendicular to the side surface 14c1, and therefore travels through the interior of the transmissive optical element 14 along the optical axis AX2 without being refracted by the side surface 14c1. The light ray LG0 is also incident perpendicular to the side surface 14c3, which is parallel to the side surface 14c1. Therefore, the light ray LG0 is emitted from the transmissive optical element 14 without being refracted by the side surface 14c3 and travels along the optical axis AX2.

[0039] Next, as shown in Figure 4D, when the transmissive optical element 14 rotates by a rotation angle ω, the light ray LG0 is refracted in the direction shown in the figure (towards +Z) and travels inside the transmissive optical element 14. As a result, the light ray LG0 travels parallel to the optical axis AX2 at a position displaced by a displacement amount d towards the +Z side from the optical axis AX2.

[0040] Next, as shown in Figure 4E, when the rotation angle ω of the transmission optical element 14 becomes larger than that in Figure 4D, the incident angle of the light ray LG0 increases, and the refraction angle increases. Therefore, the displacement d of the light ray LG0 from the optical axis AX2 becomes larger than in Figure 4D. Thus, between a rotation angle ω of 45 degrees and 90 degrees, the displacement d to the +Z side increases monotonically with increasing rotation angle ω. Note that the displacement d of the light ray LG0 to the +Z side is maximum when the rotation angle ω is as shown in Figure 4E.

[0041] As described above, since the incident surface and the exit surface of the transmissive optical element 14 in this embodiment are parallel to each other, the direction of propagation of the light ray LG0 does not change regardless of the rotation angle ω of the transmissive optical element 14, and the light ray LG0 moves in a direction parallel to the optical axis AX2 over time. The light ray LG0 repeats the above behavior on the other sides 14c2, 14c3, and 14c4. Therefore, when the transmissive optical element 14 rotates once, the displacement amount d of the light ray LG0 repeats the above cycle four times. The displacement amount of the light ray LG0 can be appropriately set by adjusting parameters such as the refractive index and size of the transmissive optical element 14.

[0042] The above explanation focused only on the light ray LG0 traveling along the optical axis AX2. However, in reality, as shown in Figure 3, the green light LG extends linearly in the Y-axis direction, which is perpendicular to the Z-axis direction in which the green light LG is displaced. Therefore, the green light LG scans within a two-dimensional illuminated region Q on the light modulation unit 22, which is the illuminated surface. The blue light LB and red light LR have different emission directions than the green light LG, but after being reflected by the respective reflective elements 17 and 18 (described later), they scan within a two-dimensional illuminated region Q on the light modulation unit 22, similar to the green light LG. In this way, the light scanning unit 21 rotates the transmission optical element 14 around the rotation axis C1, scanning the blue light LB, green light LG, and red light LR in directions perpendicular to the Y-axis direction, thereby scanning them within a two-dimensional illuminated region Q on the illuminated surface.

[0043] As shown in Figure 1, the first reflecting element 17 is positioned on the optical path of the blue light LB emitted from the blue light-emitting section 20B between the blue light-emitting section 20B and the transmissive optical element 14. The first reflecting element 17 is composed of a dichroic mirror that reflects red light and transmits blue light. Therefore, the first reflecting element 17 reflects the red light LR emitted from the transmissive optical element 14 and transmits the blue light LB emitted from the blue light-emitting section 20B. The angle between the first reflecting element 17 and the Z-axis is referred to as the inclination angle θ1 of the first reflecting element 17. The inclination angle θ1 of the first reflecting element 17 is greater than 45 degrees.

[0044] The second reflecting element 18 is positioned in the optical path of the red light LR emitted from the red light-emitting section 20R between the red light-emitting section 20R and the transmissive optical element 14. The second reflecting element 18 is composed of a dichroic mirror that reflects blue light and transmits red light. Therefore, the second reflecting element 18 reflects the blue light LB emitted from the transmissive optical element 14 and transmits the red light LR emitted from the red light-emitting section 20R. The angle between the second reflecting element 18 and the Z-axis is referred to as the inclination angle θ2 of the second reflecting element 18. The inclination angle θ2 of the second reflecting element 18 is greater than 45 degrees.

[0045] Because the tilt angle θ2 of the second reflecting element 18 is set to be greater than 45 degrees, the blue light LB reflected by the second reflecting element 18 travels diagonally with respect to the optical axis AX2 so as to approach the optical axis AX2. Similarly, because the tilt angle θ1 of the first reflecting element 17 is set to be greater than 45 degrees, the red light LR reflected by the first reflecting element 17 travels diagonally with respect to the optical axis AX2 so as to approach the optical axis AX2.

[0046] As a result, the blue light LB reflected by the second reflecting element 18, the green light LG emitted from the transmitting optical element 14, and the red light LR reflected by the first reflecting element 17 are incident on the first microlens array 43 preceding the optical modulation unit 22 from different directions, as will be described later, and overlap on the first microlens array 43. In this embodiment, the incident angle of the green light LG on the first microlens array 43 is 0 degrees. In other words, the green light LG is incident perpendicularly to the first microlens array 43. The incident angle of the blue light LB on the first microlens array 43 is α1. The incident angle of the red light LR on the first microlens array 43 is α2.

[0047] The optical modulation unit 22 is located on the optical axis AX2 on the light emission side of the light source 20. The optical modulation unit 22 modulates the blue light LB, green light LG, and red light LR emitted from the light source 20 according to image information to form image light. A transmissive liquid crystal panel 23 is used as the optical modulation unit 22. The liquid crystal panel does not have a color filter. The driving method for the liquid crystal panel is not particularly limited and may include twisted nematic (TN) method, vertical alignment (VA) method, transverse field (IPS) method, etc.

[0048] Figure 5 is a cross-sectional view of the light modulation section 22. As shown in Figure 5, the liquid crystal panel 23 constituting the light modulation section 22 has a light modulation region in which a plurality of blue subpixels PX1, a plurality of green subpixels PX2, and a plurality of red subpixels PX3 are periodically arranged in a matrix. The blue subpixels PX1 modulate blue light LB. The green subpixels PX2 modulate green light LG. The red subpixels PX3 modulate red light LR. One pixel, which is the smallest unit of an image, is composed of one blue subpixel PX1, one green subpixel PX2, and one red subpixel PX3. A light-shielding film 55 called a black matrix is ​​provided between two adjacent subpixels.

[0049] The first microlens array 43 is provided on the light incident side of the first substrate 57 that constitutes the liquid crystal panel 23. The first microlens array 43 has a configuration in which a plurality of first microlenses 431 are arranged in a matrix. The first microlens array 43 collects blue light, green light, and red light, respectively, and guides them to the subpixels PX1, PX2, and PX3 of the light modulation unit 22. One first microlens 431 is composed of a lenticular lens and is arranged across one pixel, that is, three subpixels PX1, PX2, and PX3 of different colors that are aligned in one direction. In this embodiment, a lenticular lens is given as the first microlens 431, but it is not limited to this, and microlenses with rectangular lenses arranged in a brick-like pattern, microlenses with lenses arranged to correspond to delta-arranged subpixels, or honeycomb-structured microlens arrays may also be used.

[0050] As described above, the blue light LB, green light LG, and red light LR are incident on the first microlens 431 at different angles of incidence, so they travel in different directions and are focused. As a result, the blue light LB is incident on the blue subpixel PX1, the green light LG is incident on the green subpixel PX2, and the red light LR is incident on the red subpixel PX3. In other words, the first microlens array 43 causes the blue light LB emitted from the second reflecting element to be incident on the blue subpixel PX1, the green light LG emitted from the transmitting optical element to be incident on the green subpixel PX2, and the red light LR emitted from the first reflecting element to be incident on the red subpixel PX3.

[0051] The second microlens array 44 is provided on the light emission side of the second substrate 58 that constitutes the liquid crystal panel 23. The second microlens array 44 has a configuration in which a plurality of second microlenses 441 are arranged in a matrix. The second microlens array 44 parallelizes each color of light emitted from the liquid crystal panel 23. A second microlens 441 is provided for each subpixel. In this embodiment, an example is given in which the parallelization of each color of light is performed after it is emitted from the liquid crystal panel 23, but instead of this configuration, the second microlens array 44 may be placed on the light incidence side of the liquid crystal panel 23, and the parallelization of each color of light may be performed before it is incident on the liquid crystal panel 23.

[0052] As shown in Figure 1, the ejection-side polarizer 24 is provided between the optical modulation unit 22 and the projection optical device 3 on the optical axis AX2. The ejection-side polarizer 24 transmits linearly polarized light in a specific direction emitted from the optical modulation unit 22 toward the projection optical device 3. In this embodiment, since laser diodes are used in each light-emitting element, linearly polarized light is emitted from the light source 20. Therefore, the incident-side polarizer provided on the light incidence side of the optical modulation unit 22 is unnecessary. However, an incident-side polarizer may be provided to improve contrast.

[0053] The projection optical device 3 is composed of multiple lenses. The projection optical device 3 projects the image light modulated by the light modulation unit 22 toward a projection surface such as a screen. As a result, an image is displayed on the projection surface.

[0054] In the image module 2 of this embodiment, the cross-sectional shape of the transmissive optical element 14 is rectangular as described above, and the dimensions of the first side surfaces 14c1, 14c3 and the second side surfaces 14c2, 14c4 are different from each other. The effects resulting from the rectangular cross-sectional shape of the transmissive optical element 14 will be explained below.

[0055] Figure 6 shows how light transmitted through different sides of the transmissive optical element 14 is incident on the same position in the optical modulation section 22. Specifically, Figure 6 compares two states: one in which a light ray LG0 incident from the first side surface 14c1 is emitted from the first side surface 14c3 and incident on a predetermined position 22P in the optical modulation section 22, and another in which a light ray LG0 incident from the second side surface 14c2 is emitted from the second side surface 14c4 and incident on a predetermined position P in the optical modulation section 22. In other words, for the light ray LG0 to be incident on the same position in the optical modulation section 22 in the two states means that the displacement amount d of the light ray LG0 when emitted from the first side surface 14c3 and the second side surface 14c4 is equal.

[0056] As shown in Figure 6, the rotation state of the transmitted optical element 14 differs when the light ray LG0 is incident on the predetermined position P of the optical modulation unit 22 via the first sides 14c1 and 14c3, and when the light ray LG0 is incident on the predetermined position P of the optical modulation unit 22 via the second sides 14c2 and 14c4. This is because the cross-sectional shape of the transmitted optical element 14 is rectangular, not square.

[0057] Therefore, when the rotation state of the transmissive optical element 14 is different, the angle of incidence of the light ray LG0 to the transmissive optical element 14 is different, and the optical path of the light ray LG0 passing through the inside of the transmissive optical element 14 is different. In other words, with the transmissive optical element 14 of this embodiment, the optical path length of the green light LG incident at the same position in the light modulation unit 22 can be made different. The amount of change in the optical path length of the green light LG incident at the same position in the light modulation unit 22 can be adjusted, for example, by the refractive index and size of the transmissive optical element 14.

[0058] Because green light LG, which is coherent light, has high coherence, it may be visible as speckle noise. The inventors focused on the fact that interference fringes become invisible depending on the wavelength width of the light, and that even if laser light emitted from the same light-emitting element is combined at a distance greater than the coherence length, interference fringes will not be generated. The inventors then completed the configuration of projector 1 in this embodiment.

[0059] In the image module 2 of this embodiment, by making the cross-sectional shape of the transmitted optical element 14 of the optical scanning unit 21 rectangular, the optical path length of the light ray LG0 incident at the same position in the optical modulation unit 22 can be changed to be greater than or equal to the coherence length of the green light LG.

[0060] The coherence length Lh is given by Lh = λ 2 It is defined by the formula / Δλ, where λ is the central wavelength and Δλ is the wavelength bandwidth. For example, with a central wavelength of 632.8 nm and a wavelength bandwidth of 5 nm, the coherence length is approximately 80 μm.

[0061] Thus, according to the image module 2 of this embodiment, the optical path length of the green light LG incident on the same coordinate of the light modulation unit 22 changes over time, so that light with an optical path length greater than or equal to the coherence length can be superimposed at the same position of the light modulation unit 22. Therefore, the projector 1 of this embodiment can suppress the generation of interference fringes of the green light LG incident on each position of the light modulation unit 22.

[0062] In this embodiment, the image module 2 also behaves similarly to the green light LG for the blue light LB and the red light LR. In this embodiment, the three colored lights LB, LG, and LR are incident on the transmission optical element 14. As can be seen from the above formula, the coherence length increases with the central wavelength of the incident light. In other words, if a path difference greater than or equal to the coherence length can be generated for the red light LR, it means that both the blue light LB and the green light LG will have a path difference greater than or equal to the coherence length.

[0063] In the image module 2 of this embodiment, the amount of change in the optical path length of the scanning light consisting of each color light LB, LG, and LR scanned on the optical modulation unit 22 by the optical scanning unit 21 is changed to be greater than or equal to the coherence length of the red light LR, which has the longest central wavelength among the light incident on the transmission optical element 14.

[0064] According to the image module 2 of this embodiment, the generation of interference fringes of each color light LB, LG, and LR scanning on the light modulation unit 22 can be suppressed. This makes it possible to suppress speckle in the image light generated by the image module 2.

[0065] The projector 1 of this embodiment comprises the image module 2 and a projection optical device 3 that projects speckle-suppressed image light emitted from the image module 2. Therefore, according to the projector 1 of this embodiment, since speckle-suppressed image light is projected onto the screen, it is possible to project a high-quality image with suppressed speckle noise.

[0066] (Second Embodiment) Next, an image module according to the second embodiment will be described. The image module of this embodiment differs from the first embodiment in that it uses a reflective optical element as the optical element of the optical scanning unit. The configuration of the optical scanning unit will be mainly described below. Components common to the first embodiment are denoted by the same reference numerals, and detailed explanations will be omitted.

[0067] Figure 7 is a plan view showing the main components of the image module of this embodiment. As shown in Figure 7, the image module 102 of this embodiment includes a light source 120 that emits light L consisting of laser light, an optical scanning unit 121, and an optical modulation unit 122. The optical scanning unit 121 of this embodiment includes a reflective optical element 114, a rotary drive device 15, and a rotary fixing unit 16. The reflective optical element 114 reflects the light L incident from the light source 120. The light source 120 of this embodiment emits, for example, monochromatic light L. The rotary fixing unit 16 fixes the reflective optical element 114 to the rotary drive device 15 so that it can rotate around the rotation axis C1. Furthermore, unlike the light modulation unit 22 of the first embodiment, the light modulation unit 122 does not employ a configuration in which three colored lights are incident on the subpixels of the liquid crystal panel 23 from three directions, and therefore has a general liquid crystal panel that does not have a first microlens array 43 or a second microlens array 44.

[0068] The central axis 114C passing through the center of the reflective optical element 114 is offset from the rotation axis C1 passing through the center of the rotation fixing part 16. In other words, the reflective optical element 114 is eccentric with respect to the rotation axis C1.

[0069] The reflective optical element 114 has a first surface 114a and a second surface 114b that intersect the axis of rotation C1, and six sides 114c1, 114c2, 114c3, 114c4, 114c5, and 114c6 that are perpendicular to the first surface 114a and the second surface 114b. In other words, the shape of the reflective optical element 114 is a regular hexagonal prism having eight planes, including the first surface 114a, the second surface 114b, and the six sides 114c1, 114c2, 114c3, 114c4, 114c5, and 114c6.

[0070] The rotating fixing part 16 has a notch 16K. The notch 16K is formed on the imaginary line KM connecting the central axis 114C and the rotation axis C1, on the side opposite to the rotation axis C1 with respect to the central axis 114C. With this configuration, the combined center of gravity of the rotating fixing part 16 and the reflective optical element 114 approaches the rotation axis C1, thereby suppressing the generation of vibrations and noise due to surface wobble when the rotating fixing part 16 and the reflective optical element 114 rotate around the rotation axis C1.

[0071] The following describes the effects that occur when the reflective optical element 114 is positioned eccentrically with respect to the rotation axis C1. Figure 8 shows how light reflected by the reflective optical element 114 is incident on the same position in the light modulation section. In Figure 8, for example, the state in which light L reflected from the side surface 114c1 is incident on a predetermined position 122P of the light modulation section 122, and the state in which light L reflected from the side surface 114c2 is incident on a predetermined position 122P of the light modulation section 122.

[0072] As shown in Figure 8, when comparing the two states, the positions of side surfaces 114c1 and 114c2 are different in the direction along the optical axis of light L. This is due to the eccentricity of the reflective optical element 114 with respect to the rotation axis C1.

[0073] Thus, the optical path lengths of the light L reflected by side surfaces 114c1 and 114c2, which are located at different positions along the optical axis, are different. In other words, according to the optical scanning unit 121 of this embodiment, the optical path lengths of the light incident on the same position in the optical modulation unit 122 can be made different. The amount of change in the optical path length of the light incident on the same position in the optical modulation unit 122 can be adjusted, for example, by the size of the reflective optical element 114.

[0074] As described above, the image module 102 of this embodiment allows the reflective optical element 114 to be eccentric with respect to the rotation axis C1, thereby making the position of the side surface that reflects light L incident on the same coordinate of the light modulation unit 122 different in the direction along the optical axis of the light L. This changes the optical path length of the light L incident on the same coordinate of the light modulation unit 122 to be greater than or equal to the coherence length, and allows light with an optical path length greater than or equal to the coherence length to be superimposed at the same position of the light modulation unit 122. Therefore, the image module 102 of this embodiment suppresses the generation of interference fringes of light L incident on each position of the light modulation unit 122, thereby suppressing speckle in the image light. Therefore, with the projector using the image module 102 of this embodiment, since image light with suppressed speckle is projected onto the screen, it is possible to project a high-quality image with suppressed speckle noise.

[0075] In this embodiment, the image module 102 may also be configured so that the optical scanning unit 121 scans two different colored lights with respect to the optical modulation unit 122. In this case, speckle noise of the two colored lights can be suppressed by creating an optical path difference greater than or equal to the coherence length of the longer wavelength light among the two colors. Furthermore, by combining three image modules 102 of this embodiment, it may be applied to a three-chip projector like the one in the first embodiment.

[0076] In this embodiment, the cross-sectional shape of the reflective optical element 114 is not limited to a regular hexagon, as long as the reflective optical element 114 is eccentric with respect to the rotation axis C1. The shape of the reflective optical element may be an even-sided shape such as a square, or a rectangle as in the first embodiment. However, it is most desirable for the cross-sectional shape of the reflective optical element 114 to be a regular hexagon as in this embodiment. The first reason is that, as with the case of a square, the sides facing each other are parallel, resulting in excellent processability and the ability to suppress the generation of stray light and improve light utilization efficiency. The second reason is that, compared to the case of a square, the amount of reflected light returning to the light source 120 can be reduced. Reflected light returning to the light source 120 becomes stray light, so it becomes necessary to turn off the light source 120 during the period when reflected light returns to the light source 120, which reduces the light utilization efficiency of the light source 120. By using a regular hexagon, the off time of the light source 120 can be shortened compared to the case of a square, and the light utilization efficiency of the light source 120 can be improved. Furthermore, a third reason is that as the number of sides of a reflective optical element increases, the amount of light incident from the light source crosses over the vertices of the optical element, increasing the reflection component toward the light source. In other words, if the cross-sectional shape is a regular octagon or regular decagon, which has more sides than a regular hexagon, the width of the light beam emitted from the light source becomes smaller, which may make optical axis alignment more complicated. In addition, additional optical components may be required to increase the width of the light beam emitted from the light source. In contrast, if the cross-sectional shape is a regular hexagon, problems such as the complexity of optical axis alignment and the need for additional components are less likely to occur.

[0077] (Third embodiment) Next, the image module according to the third embodiment will be described. The difference between this embodiment and the second embodiment lies in the configuration of the optical scanning unit. The configuration of the optical scanning unit will be mainly described below. Components common to the second embodiment are denoted by the same reference numerals, and detailed explanations will be omitted.

[0078] Figure 9 is a plan view showing the main components of the image module of this embodiment. As shown in Figure 9, the image module 202 of this embodiment includes a light source 120 that emits light L consisting of laser light, an optical scanning unit 221, and an optical modulation unit 122. The optical scanning unit 221 of this embodiment includes a reflective optical element 214 and a rotational drive device 15. The reflective optical element 214 reflects the light L incident from the light source 120.

[0079] In this embodiment, the central axis 214C of the reflective optical element 214 coincides with the rotation axis C1 of the rotary drive device 15. In other words, the reflective optical element 214 in this embodiment differs from that of the second embodiment in that it is not eccentric with respect to the rotation axis C1.

[0080] The reflective optical element 214 has a first surface 214a and a second surface 214b that intersect the axis of rotation C1, and six sides 214c1, 214c2, 214c3, 214c4, 214c5, and 214c6 that are perpendicular to the first surface 214a and the second surface 214b. In other words, the shape of the reflective optical element 214 is a hexagonal prism having eight planes, including the first surface 214a, the second surface 214b, and the six sides 214c1, 214c2, 214c3, 214c4, 214c5, and 214c6. Hereinafter, of the six sides 214c1, 214c2, 214c3, 214c4, 214c5, and 214c6, sides 214c1 and 214c4 may be referred to as the third side 214c1 and 214c4, sides 214c2 and 214c5 as the fourth side 214c2 and 214c5, and sides 214c3 and 214c6 as the fifth side 214c3 and 214c6.

[0081] The third side surfaces 214c1 and 214c4 have the same area and are two parallel surfaces. The fourth side surfaces 214c2 and 214c5 have the same area and are two parallel surfaces. The fifth side surfaces 214c3 and 214c6 have the same area and are two parallel surfaces. In the plane perpendicular to the rotation axis C1, the dimension S3 of the third side surfaces 214c1 and 214c4 is different from the dimension S4 of the fourth side surfaces 214c2 and 214c5. The dimension of the fifth side surfaces 214c3 and 214c6 is equal to the dimension S3 of the third side surfaces 214c1 and 214c4. In this embodiment, dimension S4 is larger than dimension S3. In other words, the cross-sectional shape of the reflective optical element 214 when cut by a plane perpendicular to the rotation axis C1 is a deformed hexagon in which one of the six sides is extended.

[0082] Figure 10 shows how light reflected by the reflective optical element 214 is incident on the same position in the light modulation section. In Figure 10, for example, the state in which light L reflected from the third side surface 214c1 is incident on a predetermined position 122P of the light modulation section 122, and the state in which light L reflected from the fourth side surface 214c2 is incident on a predetermined position 122P of the light modulation section 122.

[0083] As shown in Figure 10, when comparing the two states, the positions of the third side surface 214c1 and the fourth side surface 214c2 are different in the direction along the optical axis of light L. This is because the reflective optical element 214 is a deformed hexagon, and therefore the distance to the central axis 214C differs for each side surface.

[0084] Thus, the optical path lengths of the light L reflected by the third side surface 214c1 and the fourth side surface 214c2, which are located at different positions along the optical axis, are different. In other words, according to the optical scanning unit 221 of this embodiment, the optical path lengths of the light incident on the same position in the optical modulation unit 122 can be varied. The amount of change in the optical path length of the light incident on the same position in the optical modulation unit 122 can be adjusted, for example, by the degree and size of deformation of the reflective optical element 214.

[0085] Thus, according to the image module 202 of this embodiment, the optical path length of the light L incident on the same coordinate of the light modulation unit 122 is changed to be greater than or equal to the coherence length, so that light with an optical path length greater than or equal to the coherence length can be superimposed at the same position of the light modulation unit 122. As a result, according to the image module 202 of this embodiment, the generation of interference fringes of the light L incident on each position of the light modulation unit 122 can be suppressed, thereby suppressing speckle in the image light. Therefore, with the projector using the image module 202 of this embodiment, since image light with suppressed speckle is projected onto the screen, it is possible to project a high-quality image with suppressed speckle noise.

[0086] In addition, in the image module 202 of this embodiment, the optical scanning unit 221 may scan two different colored lights with respect to the optical modulation unit 122. In this case, speckle noise of the two colored lights can be suppressed by generating an optical path difference greater than or equal to the coherence length of the longer wavelength light among the two colors. Furthermore, by combining three of the image modules 202 of this embodiment, it may be applied to a three-chip projector like the one in the first embodiment.

[0087] Figure 11 shows the configuration of the optical scanning unit 222 according to a modified example of this embodiment. The optical scanning unit 222 shown in Figure 11 includes a reflective optical element 214, a rotational drive device 15, and a vibrating unit 223. The vibrating unit 223 vibrates the reflective optical element 214 in a plane perpendicular to the rotation axis C1.

[0088] In this modified optical scanning unit 222, the vibration unit 223 vibrates the reflective optical element 214 in a plane perpendicular to the rotation axis C1, thereby increasing the variation in the optical path length of the light reflected from each side of the reflective optical element 214 and incident on the same position in the optical modulation unit 122. This more effectively suppresses the generation of interference fringes of the light incident on each position in the optical modulation unit 122, and further reduces speckle in the image light. Therefore, a projector using an image forming module including the optical scanning unit 222 in this modified example can further improve the image quality of the projected image by further reducing speckle noise.

[0089] The technical scope of the present invention is not limited to the embodiments described above, and various modifications can be made without departing from the spirit of the invention. For example, in the first embodiment, an optical module that scans three colored lights on a single liquid crystal panel 23 was given as the image module 2, but it may also be applied to an image module that scans a single color of light on a single liquid crystal panel. When scanning a single color of light on a single liquid crystal panel, the optical scanning unit should be configured to change the optical path length of the scanning light incident on the same position on the liquid crystal panel to be greater than or equal to the coherence length of the single color of light. When scanning a single color of light on a single liquid crystal panel, a general liquid crystal panel without a first microlens array 43 or a second microlens array 44 can be used. Alternatively, a three-panel projector may be configured by combining three image modules corresponding to each of the RGB colors. Furthermore, the specific details regarding the shape, number, arrangement, materials, etc., of each component of the optical module and projector are not limited to the above embodiment and can be modified as appropriate.

[0090] A summary of this disclosure is provided below.

[0091] (Note 1) A light source including a first light-emitting section that emits first light of a first wavelength, A light scanning unit that scans the light emitted from the aforementioned light source, The optical modulation unit modulates the scanning light from the optical scanning unit based on image information, The optical scanning unit uses an optical element that rotates around a rotation axis extending in a direction intersecting the direction of incidence of the light to change the optical path length of the scanning light incident at the same position in the optical modulation unit to be greater than or equal to the coherence length of the first light. Optical module.

[0092] With this optical module configuration, the change in the optical path length of the scanning light scanned on the optical modulation section by the optical scanning section is made to be greater than the coherence length of the light incident on the transmitted optical element. This suppresses the generation of interference fringes in the scanning light scanning on the optical modulation section. As a result, speckle can be suppressed in the image light generated by the optical module.

[0093] (Note 2) The optical element is a transmissive optical element having an incident surface into which light from the light source is incident and an exit surface that emits the light incident from the incident surface. The transmitted optical element has 2 × m (m: a natural number of 2 or more) side surfaces that intersect and touch the surface perpendicular to the axis of rotation, The 2 × m sides include two first sides parallel to each other and two second sides parallel to each other. In a plane perpendicular to the axis of rotation, the dimension of the first side surface differs from the dimension of the second side surface. The incident surface and the ejection surface are at least one of the two first side surfaces and the two second side surfaces among the 2 × m side surfaces. The optical module described in Appendix 1.

[0094] This configuration allows the cross-sectional shape of the transmissive optical element, determined by a plane perpendicular to the rotation axis, to be a modified form of an equilateral polygon. This makes it possible to make the rotation state of the transmissive optical element different when light is incident on a predetermined position in the optical modulation section via the first side surface compared to when light is incident on a predetermined position in the optical modulation section via the second side surface. When the rotation state of the transmissive optical element is different, the angle of incidence to the side surface of the transmissive optical element is different, resulting in a difference in the optical path length of the light passing through the interior of the transmissive optical element. Therefore, with a transmissive optical element of this shape, the optical path length of light incident on the same position in the optical modulation section can be changed to a length greater than or equal to the coherence length. Furthermore, since each of the first and second sides is parallel to the side opposite to it, and there are no non-parallel sides, the generation of stray light in the transmitted optical element is reduced, and the light utilization efficiency can be improved.

[0095] (Note 3) The optical scanning unit further comprises a rotational drive device for rotating the optical element and a rotational fixing unit for rotatably fixing the optical element with respect to the rotational drive device, The optical element is a reflective optical element that reflects light from the light source, The central axis passing through the center of the reflective optical element is offset from the rotation axis passing through the center of the rotation fixing part. The optical module described in Appendix 1 or Appendix 2.

[0096] With this configuration, by offsetting the reflective optical element with respect to the axis of rotation, the position of the side surface that reflects light incident on the same coordinate of the optical modulation section can be made to differ in the direction along the optical axis of the light. As a result, the optical path length of light incident on the same coordinate of the optical modulation section can be changed to a length greater than the coherence length.

[0097] (Note 4) The rotation fixing portion has a notch formed on the opposite side of the rotation axis from the central axis, on a virtual line connecting the central axis and the rotation axis. The optical module described in Appendix 3.

[0098] With this configuration, the combined center of gravity of the rotating fixing part and the reflective optical element 4 approaches the axis of rotation, thereby suppressing vibrations and noise caused by surface wobble when the rotating fixing part and the reflective optical element rotate around the axis of rotation.

[0099] (Note 5) The optical element is a reflective optical element that reflects light from the light source, The reflective optical element has a plurality of sides that intersect and are in contact with a surface perpendicular to the axis of rotation, The plurality of sides include two third sides parallel to each other and two fourth sides parallel to each other. In a plane perpendicular to the axis of rotation, the dimension of the third side is different from the dimension of the fourth side. The optical module described in any one of the appendices 1 through 4.

[0100] With this configuration, the position of the third side surface in the direction along the optical axis of the light when it is reflected by the third side surface and incident on the predetermined position of the light modulation section can be made different from the position of the fourth side surface in the direction along the optical axis of the light when it is reflected by the fourth side surface and incident on the predetermined position of the light modulation section. Therefore, with a reflective optical element of this shape, the optical path length of the light incident on the same position of the light modulation section can be changed to a length greater than or equal to the coherence length.

[0101] (Note 6) The optical scanning unit has a vibrating unit that vibrates the reflective optical element in a plane perpendicular to the rotation axis. The optical module described in Appendix 5.

[0102] This configuration allows for increased variation in the optical path length of light reflected from each side of the reflective optical element and incident at the same position in the optical modulation section. This further reduces the speckle of the image light generated in the optical modulation section.

[0103] (Note 7) The light source further includes a second light-emitting section that emits a second light having a second wavelength longer than the first wavelength, The change in the optical path length of the scanning light is greater than or equal to the coherence length of the second light. The optical module described in any one of the appendices 1 through 6.

[0104] With this configuration, by generating an optical path difference greater than or equal to the coherence length of the long-wavelength second light, it is possible to achieve an optical path difference greater than or equal to the coherence length for the first light as well. Therefore, speckle noise can be suppressed for both the first and second light. (Note 8) An optical module described in any one of the appendices 1 through 7, The system comprises a projection optical device that projects light emitted from the optical module, projector.

[0105] With this projector configuration, the optical module generates image light with suppressed speckle, allowing for the projection of high-quality images with reduced speckle noise. [Explanation of symbols]

[0106] 1...Projector, 3...Projection optical device, 14...Transmission optical element, 14c, 14c1, 14c2, 14c3, 14c4, 114c1, 114c2, 214c1, 214c2, 214c3...Side view, 15...Rotation drive device, 16...Rotation fixing part, 16K...Notch, 20, 120...Light source, 20B...Light-emitting part, 21, 121, 221, 222...Optical path Inspection part, 22,122...Optical modulation part, 114,214...Reflective optical element, 114C,214C...Central axis, 14c1,14c3...First side surface, 14c2,14c4...Second side surface, 223...Vibration part, 214c1...Third side surface, 214c2...Fourth side surface, C1...Rotation axis, KM...Visible line, L...Light, Lh...Coherence length, S1,S2,S3,S4...Dimensions.

Claims

1. A light source including a first light-emitting section that emits first light of a first wavelength, A light scanning unit that scans the light emitted from the aforementioned light source, The optical modulation unit modulates the scanning light from the optical scanning unit based on image information, The optical scanning unit uses an optical element that rotates around a rotation axis extending in a direction intersecting the direction of incidence of the light to change the optical path length of the scanning light incident at the same position in the optical modulation unit to be greater than or equal to the coherence length of the first light. Optical module.

2. The optical element is a transmissive optical element having an incident surface into which light from the light source is incident and an exit surface that emits the light incident from the incident surface. The transmitted optical element has 2 × m (m: a natural number of 2 or more) side surfaces that intersect and touch the surface perpendicular to the axis of rotation, The 2 × m sides include two first sides parallel to each other and two second sides parallel to each other. In a plane perpendicular to the rotation axis, the dimension of the first side surface differs from the dimension of the second side surface. The incident surface and the ejection surface are at least one of the two first side surfaces and the two second side surfaces among the 2 × m side surfaces. The optical module according to claim 1.

3. The optical scanning unit further comprises a rotational drive device for rotating the optical element and a rotational fixing unit for rotatably fixing the optical element with respect to the rotational drive device, The optical element is a reflective optical element that reflects light from the light source, The central axis passing through the center of the reflective optical element is offset from the rotation axis passing through the center of the rotation fixing part. The optical module according to claim 1.

4. The rotation fixing portion has a notch formed on the opposite side of the rotation axis from the central axis, on a virtual line connecting the central axis and the rotation axis. The optical module according to claim 3.

5. The optical element is a reflective optical element that reflects light from the light source, The reflective optical element has a plurality of sides that intersect and are in contact with a surface perpendicular to the axis of rotation, The aforementioned plurality of sides include two third sides parallel to each other and two fourth sides parallel to each other. In a plane perpendicular to the rotation axis, the dimension of the third side is different from the dimension of the fourth side. The optical module according to claim 1.

6. The optical scanning unit has a vibrating unit that vibrates the reflective optical element in a plane perpendicular to the rotation axis. The optical module according to claim 5.

7. The light source further includes a second light-emitting unit that emits a second light having a second wavelength longer than the first wavelength, The change in the optical path length of the scanning light is greater than or equal to the coherence length of the second light. The optical module according to claim 1.

8. An optical module according to any one of claims 1 to 7, The system comprises a projection optical device that projects light emitted from the optical module, projector.

Images