JP2016126025A - Lens and projection image display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lens capable of suppressing an influence of back focus variation even if an environment changes although being inexpensive, and a projection image display device using the same.SOLUTION: Since a leg part LG of a collimator lens COL has its length T determined so that an expression (1) is satisfied, the leg part LG extends and contracts ((T±ΔT) as an ambient temperature varies, so that variation in back focus can be suppressed. Additionally, the collimator lens COL has a pair of cuts CT, so even after an end face of the leg part LG is bonded to a stem part ST, a laser chip CP is not sealed in the collimator lens COL and cooled with outside air via the cuts CT, so that the collimator lens COL can be suppressed from rising in temperature, thereby effectively suppressing variation in back focus. Here, BF≤T≤φ (1), where BF is a distance (mm) from a light source-side optical surface to a condensing point, and φ is a lens outer diameter (mm).SELECTED DRAWING: Figure 6

Description

  The present invention relates to a projection image display device and a lens used therefor.

  In recent years, for the purpose of reducing the size and weight, projection image display apparatuses using a semiconductor laser or LED (Light Emitting Diode) as a light source have been actively developed. Among projection image display devices using a semiconductor laser, in particular, a scanning projection image display device combining an RGB laser and a MEMS mirror can reduce the number of parts and can be relatively easily reduced in size. It is attracting attention because it can.

  The light beam emitted from the light source for projecting the image is converted into a parallel light beam by a collimating lens, and then illuminates a MEMS mirror having a function of two-dimensional scanning, and finally forms an image on the screen. To do. Since the collimating lens is made of plastic, a high-precision lens can be mass-produced at low cost, and a projection image display device can also be produced at low cost. However, a general plastic collimating lens has a problem due to environmental changes. Specifically, since the back focus of the collimating lens changes due to refractive index fluctuation or expansion / contraction of the plastic material due to environmental temperature changes, or wavelength shift of the light beam emitted from the light source, it is emitted from the collimating lens. The parallelism of the luminous flux changes, and as a result, the luminous flux diameter at a predetermined projection position also changes greatly. Therefore, when such a collimating lens is used in a projection image display device, there is a risk that image quality will deteriorate. To solve this problem, a collimating lens can be emitted from the collimating lens by moving the collimating lens in the optical axis direction according to the amount of back focus change caused by a temperature change using a driving actuator. There is a problem of increasing the number of parts and increasing the size of the apparatus.

  On the other hand, Patent Document 1 discloses a technique for reducing a back focus change amount and suppressing image quality deterioration in a projection image display device by providing a collimating lens with a diffractive structure even when the environmental temperature changes. Yes.

Japanese Patent No. 5488803 International Publication No. 2014/0733305

  However, when creating a collimating lens with a diffractive structure by injection molding using a mold, due to the difficulty in mold processing technology and molding technology, the ideal shape such as the tip sag or taper on the diffraction stepped portion This causes a problem that the actual diffraction efficiency is lowered from the design value. In particular, the larger the phase difference amount of the phase function that determines the diffractive structure, the more significant it becomes. In the collimating lens of Patent Document 1, a diffractive structure is provided to reduce back focus change. However, the diffraction step amount is set so that the diffraction efficiency is high with respect to the three wavelengths of RGB, and The number of diffraction zones is also increasing. That is, the number of diffraction stepped portions and the taper region are increased, and the diffraction efficiency is reduced due to the light loss. That is, since the utilization efficiency of the light beam emitted from the laser light source is lowered, it is necessary to make the laser light source have a higher output, which may further increase the temperature, increase the cost, and project the image display device. There is a risk of increasing the size.

  On the other hand, in Patent Document 2, the distance between the light source and the lens optical surface changes due to expansion / contraction of the plastic leg due to temperature change by fixing the lens leg on the substrate. That is, there is a description that it is advantageous for back focus change. However, it is not clearly shown how the length of the lens leg is advantageous for changing the back focus. In addition, since the lens disclosed in Patent Document 2 is a cap type, heat is trapped between the light source and the lens when used while being covered with a light source, leading to an increase in the temperature of the lens exceeding an assumed environmental temperature. Therefore, a material having higher heat resistance is required, which may increase the cost. Alternatively, in order to avoid the influence of the temperature rise of the lens exceeding the assumed environmental temperature, it is necessary to excessively increase the number of ring zones of the diffractive structure at the expense of diffraction efficiency.

  The present invention has been made in view of the problems of the prior art, and is a low-cost lens that can suitably suppress the influence of back focus change even when environmental changes occur, and a projection image display apparatus using the same The purpose is to provide.

The lens according to claim 1 is a lens for a projection image display device,
The lens is made of integrally molded plastic, and has a lens part that converts a light beam emitted from the light source into parallel light or convergent light, and a leg part that holds the lens part,
The leg is fixed to at least a part of the end of the leg with respect to the base that supports the light source, and has an opening or a notch at least at one position of the leg,
The leg length T (mm) satisfies the following formula.
BF ≤ T ≤ φ (1)
However,
BF: Distance from light source side optical surface to condensing position (mm)
φ: Lens outer diameter (mm)

  According to the present invention, utilizing the fact that the leg portion holding the lens unit expands / contracts when the environmental temperature changes, the refractive index change and shape change of the lens unit that occur simultaneously, and the light emitted from the light source This works in the direction of canceling the change in the back focus caused by the wavelength shift of the lens, and suppresses the change in the emission angle of the light beam emitted from the lens. As a result, a change in beam diameter at the projection position can be suppressed. In particular, by setting the value T in the equation (1) to be equal to or less than the upper limit, the lens can be stably molded, which contributes to downsizing of the apparatus. Further, by setting the value T in the expression (1) to be equal to or higher than the lower limit, it is effective in reducing the beam diameter change at the projection position. Moreover, since the said leg part forms the opening or the notch in at least one place of the said leg part, ventilation can be performed between the exterior and the inside of the said leg part through the said opening or the said notch. Thereby, it is possible to prevent the lens portion from being overheated by suppressing the temperature rise inside the leg portion, and it becomes unnecessary to select a plastic material having high heat resistance. Moreover, since the temperature rise inside the leg portion can be suppressed, the length T of the leg portion can be made lower than the upper limit, and the increase in the size of the device and the difficulty in molding the lens can be suppressed. can do. In addition, it is preferable that the said opening or the said notch is arrange | positioned on the opposite side through an optical axis from a viewpoint of promoting the convection of air. Further, from the viewpoint of retaining air more efficiently, the notch is preferably open from the end surface of the leg portion to the height of the optical surface on the light source side.

  The lens according to claim 2 is characterized in that, in the invention according to claim 1, the leg portion is formed with at least two notches extending from the end portion toward the lens portion. And

  By forming the notches in at least two places, one notch can be used as an air inlet and the other notch can be used as an air outlet between the outside and the inside of the leg portion. Ventilation can be performed. Moreover, the moldability of the lens can be improved by forming the notches.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, the shape of the lens when viewed from the optical axis direction has at least two linear portions that are substantially parallel across the optical axis. It is characterized by.

  When the lens is viewed from the optical axis direction so that it has at least two linear portions that are substantially parallel across the optical axis, the heated air can be more easily removed and the lens can be removed. By using it in a projection image display device or the like, an effect that the height can be reduced is obtained. Note that “substantially parallel” means that the relative angle between two straight lines is within ± 5 degrees. Further, from the viewpoint of making the effect even more remarkable, it is preferable that the distance between two substantially parallel linear portions is in the range of 0.7 to 2 times the optical surface diameter of the lens.

  The lens according to a fourth aspect is characterized in that, in the invention according to any one of the first to third aspects, the thickness of the leg portion increases from the end portion toward the lens portion.

  In the case where the lens is molded with a mold, the releasability is enhanced by providing a so-called draft taper in which the thickness of the leg portion increases from the end portion toward the lens portion.

  A lens according to a fifth aspect is characterized in that, in the invention according to any one of the first to fourth aspects, a diffractive structure is formed in the lens portion.

  If the diffractive structure is provided in the lens unit, it is possible to adjust the back focus change due to the environmental temperature change. The change amount of the back focus can be adjusted by the phase difference amount of the phase function that determines the diffractive structure, and the change of the back focus can be more effectively suppressed in combination with the expansion / contraction of the leg portion. It is preferable that the diffraction efficiency of the diffractive structure is close to the design value when the lens is molded by injection molding.For example, when a diffraction step where the first-order diffracted light is generated within the effective diameter of the lens, the minimum width of the diffractive ring zone Is preferably a phase difference amount of 5 μm or more. In order to reduce the change in diffraction efficiency due to the environmental temperature, it is preferable that the diffraction order generated by the diffraction step is 5th order diffraction or less.

  A projection image display apparatus according to a sixth aspect uses the lens according to any one of the first to fifth aspects.

  A projection image display device according to a seventh aspect is the invention according to the sixth aspect, wherein a plurality of pairs of the light source and the lens are provided, and a straight line passing through a center of the adjacent light source is set in an optical axis direction of the lens. When moving in parallel to the leg side, the straight line moved by a predetermined amount passes through the opening or notch of the leg portion.

  According to the present invention, since the openings or notches of the leg portions of the adjacent lenses are provided at positions facing each other, for example, a forcible fan or the like is provided, and the straight line passes through the facing openings or notches. By ventilating a large amount of air per unit time along the, effective ventilation can be performed. In addition, it is desirable that two or more openings or notches are provided, and the straight line does not overlap with portions other than the openings or notches. For example, in the case where the same lens is arranged 90 degrees apart, if the heat from the light source of one lens hits only a part of the leg part of the adjacent lens, uneven temperature change in the leg part will occur. Inviting and affecting the optical characteristics is preferable because such a problem does not occur.

  A projection image display device according to an eighth aspect is the invention according to the seventh aspect, wherein a plurality of pairs of the light source and the lens are provided, and a straight line passing through a center of the adjacent light source in the optical axis direction of the lens. The straight line does not pass through the opening or notch of the leg when translated to the leg side.

  According to the present invention, since the openings or notches of the leg portions of the adjacent lenses are provided at positions that do not face each other, the heated air that has flowed out of one opening or notch, for example, by natural convection, Inflow to the opening or notch of the lens is suppressed, and the temperature rise of the other lens unit can be suppressed. Note that two or more openings or notches are provided from the viewpoint of air convection and miniaturization in the height direction of the projection image display device, and the shape of the lens viewed from the optical axis direction is at least the optical axis. It is desirable to have two straight lines substantially parallel to each other. For example, in the case where the same lens is arranged 90 degrees apart, if the heat from the light source of one lens hits only a part of the leg part of the adjacent lens, uneven temperature change in the leg part will occur. Inviting and affecting the optical characteristics is preferable because such a problem does not occur.

  According to the present invention, it is possible to provide a lens capable of suppressing the influence of a change in back focus even if an environmental change occurs, and a projection image display apparatus using the lens, which is inexpensive.

It is the figure which showed the state by which the projector by this embodiment was mounted in the mobile terminal. It is a figure for demonstrating the structure of the scanning optical system by this embodiment. It is a figure corresponding to the cross section along the III-III line of FIG. It is a top view of the scanning part of the scanning optical system shown in FIG. FIG. 5 is an enlarged cross-sectional view of a part (drive unit) of the scanning unit shown in FIG. 4. It is a figure which expands and shows the laser light source part 1-R. It is the figure which looked at the collimating lens COL used for the laser light source part 1-R from the light source side. It is the figure which cut | disconnected the structure of FIG. 7 by the VIII-VIII line, and looked at the arrow direction. It is a figure which shows the modification of this Embodiment. It is a figure which shows the modification of this Embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. With reference to FIG. 1, a projector 100 that is a projection image display device is preferably mounted on a mobile terminal 40 such as a mobile phone or a PDA (Personal Digital Assistant). Therefore, the projector 100 is miniaturized to such an extent that it can be stored in a small space in the mobile terminal 40.

  A semiconductor laser that generates laser light is used as the light source of the projector 100, and the laser light is scanned on the projection surface 41 in the horizontal direction (H direction) and the vertical direction (V direction) to be input to the projector 100. The obtained image information is projected onto the projection surface 41. The projection surface 41 may be a screen prepared separately, but may be other than a screen. For example, a wall surface or the like may be used as the projection surface 41.

  Further, the reproduction of the color tone of the image information input to the projector 100 is performed by intensity-modulating the red, green, and blue laser lights, which are the three primary colors of light, at high speed and combining them. In this case, the wavelength of the red laser beam is set to about 640 nm, for example, and the wavelength of the green laser beam is set to about 530 nm, for example. Further, the wavelength of the blue laser light is set to about 450 nm, for example.

  2 to 5, the scanning optical system 20 is configured to generate red, green, and blue laser beams, convert them into parallel light beams, and then synthesize and scan them. That is, the scanning optical system 20 includes a laser light source unit 1, a scanning unit 2, and a plurality of optical components such as mirrors, and these are housed in a predetermined case member (housing) 20a. It has become. 2 and 3, the laser beam is represented by a two-dot chain line.

  The laser light source unit 1 is for generating red, green and blue laser beams. Hereinafter, the laser light source unit 1 that generates red laser light is referred to as a laser light source unit 1-R, and the laser light source unit 1 that generates green laser light is referred to as a laser light source unit 1-G. The laser light source unit 1 that generates blue laser light is referred to as a laser light source unit 1-B.

  The laser light source unit 1-R is made of a red semiconductor laser having high emission intensity and capable of high-speed intensity modulation. The red semiconductor laser as the laser light source unit 1-R is a CAN package type, and a laser chip is attached to a heat dissipation base called a stem.

  FIG. 6 is an enlarged view of the laser light source unit 1-R. In FIG. 6, the laser light source unit 1-R is disposed at the center on the stem portion ST (base portion) ST obtained by applying nickel plating and gold plating to the SPC material, which is a metal metal, and the stem portion ST. A submount SM, a semiconductor laser chip (light source) CP disposed on the submount SM, and four leads LD each having one end attached to the stem portion ST (one is connected to the base of the submount SM) 2 are connected to the semiconductor laser chip CP, and the other is connected to a monitor (not shown). A collimating lens COL is attached to the laser light source unit 1-R. When power is supplied via the lead LD, the red semiconductor laser chip emits light, and the emitted light beam directly enters the collimating lens COL and is converted into a substantially parallel light beam.

7 is a view of the collimating lens COL used in the laser light source unit 1-R as viewed from the light source side, and FIG. 8 is a view of the configuration of FIG. 7 cut along the line VIII-VIII and viewed in the direction of the arrow. is there. In the drawing, a collimating lens (lens) COL is obtained by integrally molding a transparent polyolefin resin (but not limited to this), and is formed in the direction orthogonal to the optical axis from the central lens portion LS and its periphery. It consists of an extending flange portion FL and a pair of leg portions LG extending from the flange portion FL in the optical axis direction. When the collimator lens COL is viewed in the optical axis direction, a portion facing the optical axis of the flange portion FL (a portion sandwiched between the leg portions LG) is a substantially parallel straight portion LN. In addition, a pair of notches CT extending from the leg portion LG to the flange portion FL toward the lens portion LS is formed in a line-symmetric position between the pair of leg portions LG. The thickness of the leg part LG gradually increases from the end part to the flange part FL. Thus, by forming a taper in the leg LG, the collimating lens COL can be easily removed from the mold during injection molding. Here, a distance T (mm) from the light source side surface apex of the lens portion LS to the end portion of the leg portion LG is defined as the length of the leg portion LG. The length T (mm) of the leg satisfies the following formula.
BF ≤ T ≤ φ (1)
Note that BF represents the distance (mm) from the light source side optical surface to the condensing position, and φ represents the lens outer diameter (mm).

  In FIG. 6, the lens part LS is arranged so that the optical axis of the lens part LS overlaps the center of the emission port of the semiconductor laser chip CP, and the end face of the leg part LG is bonded to the surface FP of the stem part ST. Since the back focus of the lens part LS is appropriately set with respect to the length T of the leg part LG, the end face of the leg part LG is simply bonded and fixed to the surface FP of the stem part ST, and the semiconductor laser chip CP is used. The emitted light beam enters the lens unit LS, is converted to a specific magnification, and is emitted. Note that a diffractive structure may be provided in the lens portion LS.

  In FIG. 2, a laser light source unit 1-G is made of a CAN package type green semiconductor laser having high emission intensity and capable of high-speed intensity modulation, and its structure is substantially the same as the laser light source unit 1-R. However, the shape of the lens portion LS of the collimating lens COL may be changed according to the light source wavelength of the green semiconductor laser.

  The laser light source unit 1-B is made of a CAN package type blue semiconductor laser having high emission intensity and capable of high-speed modulation of intensity, and its structure is substantially the same as the laser light source unit 1-R. The shape of the lens portion LS of the collimating lens COL may be changed according to the light source wavelength of the blue semiconductor laser.

  The scanning unit 2 is for two-dimensionally scanning the laser beam after being converted into a parallel light beam and synthesized, and reflects the synthesized laser beam toward the projection surface 41 (see FIG. 1). At least a scanning mirror 3 is provided. The tilt angle (reflection angle) of the scanning mirror 3 can be changed. By changing the tilt angle of the scanning mirror 3, two-dimensional scanning of the combined laser beam by the scanning unit 2 is performed.

  Here, in this embodiment, the scanning mirror 3 is incorporated in a MEMS (micro electro mechanical system), and the MEMS in which the scanning mirror 3 is incorporated is used as the scanning unit 2. In addition, the scanning unit 2 is substantially flat and has a small thickness, and the outer shape thereof is a substantially square shape (the length of one side is about 1 cm) in plan view (see FIG. 2).

  As a specific structure, as shown in FIG. 4, the scanning unit 2 is formed of a structure obtained by performing an etching process or the like on the silicon substrate. In addition to the scanning mirror 3, the fixed frame 4, The drive unit 5 and the movable frame 6 are integrally provided. In the following description, an axis that crosses the center of the scanning mirror 3 in the horizontal direction in FIG. 4 is an X axis, and an axis that crosses the center of the scanning mirror 3 in the vertical direction in FIG. In other words, the point where the X axis and the Y axis are orthogonal to each other is the center of the scanning mirror 3.

  The fixed frame 4 is a part corresponding to the outer edge of the scanning unit 2 and surrounds other parts (such as the scanning mirror 3, the drive unit 5, and the movable frame 6).

  The drive unit 5 is separated from the fixed frame 4 in the X-axis direction and is connected to the fixed frame 4 in the Y-axis direction. Furthermore, the drive unit 5 includes four unimorph structures, and the four unimorph structures are arranged so as to be symmetric with respect to each of the X axis and the Y axis and are separated from each other. . Further, as shown in FIG. 5, the unimorph structure as the drive unit 5 includes a piezoelectric element (a material obtained by polarization of a sintered body made of PZT or the like) 5a sandwiched between a pair of electrodes 5b, and a silicon substrate. It is formed by pasting on the region to be the driving unit 5.

  In such a drive unit 5, when a voltage is applied to the pair of electrodes 5b, the piezoelectric element 5a sandwiched between the pair of electrodes 5b expands or contracts. When the piezoelectric element 5a expands or contracts, the region serving as the driving unit 5 of the silicon substrate expands or contracts accordingly. That is, the drive unit 5 is driven by being supplied with electric power.

  Further, as shown in FIG. 4, the movable frame 6 is a substantially rhombus-shaped frame located inside the drive unit 5. Both ends of the movable frame 6 on the X axis are connected to the drive unit 5, and the other parts are separated from the drive unit 5. Thereby, the movable frame 6 can be rotated around the X axis.

  A pair of torsion bars 7 extending along the Y-axis direction are provided inside the movable frame 6. The pair of torsion bars 7 are arranged so as to overlap the Y axis and be symmetric with respect to the X axis. Further, one end of each of the pair of torsion bars 7 is connected to an end of the movable frame 6 on the Y axis.

  The scanning mirror 3 is disposed between the other ends of the pair of torsion bars 7 and is supported by the other end. For this reason, the scanning mirror 3 is rotated around the X axis together with the movable frame 6 and is rotated around the Y axis using the torsion bar 7 as a rotation axis. Note that the scanning mirror 3 is formed in a substantially circular shape, and is obtained by sticking a reflective film made of gold, aluminum, or the like on a region to be the scanning mirror 3 of the silicon substrate.

  The scanning unit 2 of the present embodiment has the above structure. The scanning operation of the scanning unit 2 is performed by adjusting the timing for driving (stretching) the four driving units 5 and vibrating the scanning mirror 3 around the X axis and the Y axis. For example, the frequency when vibrating around the X axis is set to about 60 Hz, and the frequency when vibrating around the Y axis is set to about 30 kHz.

  More specifically, each of the four drive units 5 is denoted by reference numerals 5-1 to 5-4. When the scanning mirror 3 is vibrated around the X axis, the drive units 5-1 and 5-3 are provided. , And the drive units 5-2 and 5-4 as the other set, the polarity of the voltage applied to each of the one set and the other set is reversed. In this case, when the driving units 5-1 and 5-3 that are one set are deformed in the extending direction, the driving units 5-2 and 5-4 that are the other set are deformed in a contracting direction. When the drive units 5-1 and 5-3 are deformed in the contracting direction, the other drive units 5-2 and 5-4 are deformed in the extending direction. As a result, the scanning mirror 3 vibrates around the X axis together with the movable frame 6, and the inclination of the scanning mirror 3 varies around the X axis. Since the torsion bar 7 is twisted in a direction perpendicular to the vibration direction around the X axis, the vibration of the scanning mirror 3 around the X axis is not affected.

  Further, when the scanning mirror 3 is vibrated around the Y axis, the drive units 5-1 and 5-2 are set as one set, and the drive units 5-3 and 5-4 are set as the other set. The polarity of the voltage applied to each of the set and the other set is reversed. In this case, when the driving units 5-1 and 5-2 that are one set are deformed in the extending direction, the driving units 5-3 and 5-4 that are the other set are deformed in a contracting direction, When the drive units 5-1 and 5-2 are deformed in a contracting direction, the other drive units 5-3 and 5-4 are deformed in an extending direction. Thereby, the scanning mirror 3 vibrates around the Y axis together with the movable frame 6, and the inclination of the scanning mirror 3 varies around the Y axis.

  At this time, if the scanning mirror 3 is tilted around the Y axis only by deforming the drive unit 5, the fluctuation of the tilt of the scanning mirror 3 around the Y axis becomes small. For this reason, when actually performing the scanning operation, the frequency of the voltage applied to the drive unit 5 is set so that the scanning mirror 3 resonates with the frequency of the voltage applied to the drive unit 5. That is, the vibration around the Y axis of the scanning mirror 3 is made with the torsion bar 7 as a reference.

  By operating the scanning unit 2 as described above, the scanning mirror 3 can be rotated around two axes orthogonal to each other, and the combined laser beam is two-dimensionally scanned by the single scanning mirror 3. Is possible. Therefore, the red, green, and blue laser light source units can be blinked in synchronization with each other in accordance with an image signal input to the projector, and a color image can be displayed on the projection plane 41 by a combination of the emitted laser beams.

  By the way, in this embodiment, red, green, and blue laser beams are configured to take optical paths (two-dot chain lines in the drawings) as shown in FIGS. That is, red, green, and blue laser beams are collimated and then reflected by a plurality of optical components so that the red, green, and blue laser beams travel toward the scanning mirror 3. Further, when one optical path is formed between two different optical components, at least two optical paths with respect to the normal direction N (see FIG. 3) of the reflecting surface 3a of the scanning mirror 3 in the non-driven state. The planes including are orthogonal. Hereinafter, the optical paths of the red, green, and blue laser beams will be described in detail.

  First, in the case member 20a, the laser light source units 1-G, 1-R, and 1-B are arranged in this order from the upper side to the lower side in FIG. Further, the laser light source units 1-R, 1-G, and 1-B have the same emission directions, and the emission directions are parallel to the reflecting surface 3a of the scanning mirror 3 in the non-driven state. It is arranged to become. The laser light source units 1-R, 1-G, and 1-B are partially overlapped with the scanning unit 2 in plan view (see FIG. 2). Among them, the laser light source units 1-R1-G and 1-B are in a state where most of the respective light emission sides are completely overlapped with the scanning unit 2.

  Near the upper part of the scanning mirror 3 (see FIG. 3), although not shown in FIG. 2, a projection mirror 8 for projecting the combined laser beam onto the scanning mirror 3 is arranged. That is, the combined laser beam is reflected by the projection mirror 8 toward the scanning mirror 3.

  As a specific optical path, red laser light is emitted from the laser light source unit 1-R, and then collimated lens COL, dichroic mirror 22, dichroic mirror 23, folding mirror 24, folding mirror 25 and projection mirror 8 are passed through this. The light passes through in order and is incident on the scanning mirror 3 by being reflected by the projection mirror 8.

  The collimating lens COL is used to change the laser light from diverging light to substantially parallel light. The bending mirrors 24 and 25 are for simply changing the traveling direction of the laser light. The dichroic mirror 22 transmits green laser light and reflects red laser light. The dichroic mirror 22 has a function of combining green and red laser light by being arranged as shown in FIG. The dichroic mirror 23 transmits green and red laser light and reflects blue laser light, and has a function of combining green, red, and blue laser light by arranging as shown in FIG. Have.

  In this red laser beam, after being collimated by the collimating lens COL, the optical path except for the front and rear of the projection mirror 8 (after the folding mirror 25) is placed in the same plane. That is, after the red laser light is made substantially parallel light by the collimator lens COL, it passes through the dichroic mirror 22, the dichroic mirror 23, the folding mirror 24, and the folding mirror 25 in this order in the same plane.

  The green laser light is emitted from the laser light source unit 1-G and passes through the collimating lens COL, the bending mirror 27, the dichroic mirror 22, the dichroic mirror 23, the bending mirror 24, the bending mirror 25, and the projection mirror 8 in this order. The light is incident on the scanning mirror 3 by being reflected by the projection mirror 8.

  The bending mirror 27 is for simply changing the traveling direction of the laser light.

  In the green laser light, after being collimated by the collimating lens COL, the optical path except for the front and rear of the projection mirror 8 (after the folding mirror 25) is placed in the same plane. That is, the green laser light is made substantially parallel light by the collimating lens COL, and then passes through the bending mirror 27, the dichroic mirrors 22, 23, the bending mirror 24, and the bending mirror 25 in this order in the same plane. Yes.

  After the blue laser light is emitted from the laser light source unit 1-B, it passes through the collimating lens COL, the dichroic mirror 23, the folding mirror 24, the folding mirror 25, and the projection mirror 8 in this order, and is reflected by the projection mirror 8. Is incident on the scanning mirror 3. The collimating lens COL is used to change the laser light from diverging light to substantially parallel light.

  In this blue laser light, after being collimated by the collimating lens COL, the optical path except for the front and rear of the projection mirror 8 (after the folding mirror 25) is placed in the same plane. That is, after the blue laser light is made substantially parallel light by the collimating lens COL, it passes through the dichroic mirror 23, the bending mirror 24, and the bending mirror 25 in this order in the same plane.

  In this embodiment, the optical paths except for the front and rear of the projection mirror 8 (after the folding mirror 25) are in the same plane in all of the red, green and blue laser beams, and the plane is scanned in the non-driven state. The mirror 3 is perpendicular to the normal direction N (see FIG. 3) of the reflecting surface 3a. Then, at least a part of the optical path included in the plane is arranged in a region on the scanning unit 2. However, all the red, green, and blue laser beams take an optical path in the region on the scanning unit 2 until slightly before entering the bending mirror 24, and after being reflected by the bending mirror 25, again on the scanning unit 2. An optical path is taken in the area.

  Further, by arranging various optical components so as to be in the state shown in FIGS. 2 and 3, red, green and blue laser beams are reflected four times each before entering the scanning mirror 3. It will be. That is, since the red laser light is reflected in the order of the dichroic mirror 22, the bending mirror 24, the bending mirror 25, and the projection mirror 8, the number of reflections is four. Since the green laser light is reflected in the order of the bending mirror 27, the bending mirror 24, the bending mirror 25, and the projection mirror 8, the number of reflections is four. Since the blue laser light is reflected in the order of the dichroic mirror 23, the bending mirror 24, the bending mirror 25, and the projection mirror 8, the number of reflections is four. Note that red, green, and blue laser beams are reflected three times each in a plane orthogonal to the normal direction N of the reflecting surface 3a of the scanning mirror 3 in the non-driven state.

  Further, a part of each of the laser light source units 1-R, 1-G, and 1-B is overlapped with the scanning unit 2 in plan view (see FIG. 2). In particular, most of the light emission sides of the laser light source units 1-R, 1-G, and 1-B are completely overlapped with the scanning unit 2. Therefore, all of the red, green and blue laser beams take optical paths in the region on the scanning unit 2 immediately after emission.

  As described above, it is possible to further reduce the size by arranging a part of each of the optical paths of the red, green, and blue laser beams (the optical path just before the folding mirror 24) in the region on the scanning unit 2. The scanning optical system 20 can be obtained. The scanning optical system 20 has an outer size of about 18 mm × about 24 mm in a plan view (see FIG. 2) and a thickness of about 7 mm.

  In this embodiment, the dichroic mirror is a folding mirror, but the means for combining the laser beams may be a dichroic prism or a reflecting prism.

  In the present embodiment, as described above, the red, green, and blue laser lights are reflected four times each before entering the scanning mirror 3, thereby making it easy to make the optical path compact. It can be carried out. In addition, after the red, green, and blue laser beams are easily combined, the combined laser beam can be incident on the scanning mirror 3.

  In the present embodiment, as described above, the scanning unit 2 can be made thin by configuring the scanning unit 2 with the MEMS in which the scanning mirror 3 is incorporated. Therefore, the scanning optical system 20 is thinned. It becomes easy.

  In the present embodiment, as described above, the scanning mirror 3 can be rotated around two axes that are orthogonal to each other, so that the two-dimensional scanning of the combined laser beam is 1 The two scanning mirrors 3 can be used, and it is not necessary to perform two-dimensional scanning of the combined laser beam with two scanning mirrors. Thereby, the installation space for the scanning mirror is reduced, so that the scanning optical system 20 can be further downsized.

  In the present embodiment, as described above, the scanning mirror 3 is driven by the piezoelectric element 5a, so that the piezoelectric element 5a can vibrate the scanning mirror 3 with a thin structure. The drive-type scanning unit 2 is very thin.

  In the present embodiment, as described above, the emission directions of the laser light source units 1-R, 1-G, and 1-B are parallel to the reflecting surface 3a of the scanning mirror 3 in the non-driven state. With this configuration, it is possible to easily arrange at least two optical paths in a plane orthogonal to the normal direction N of the reflecting surface 3a of the scanning mirror 3 in the non-driven state. In addition, by superposing a part of each of the laser light source units 1-R, 1-G, and 1-B on the scanning unit 2, the plane area of the scanning optical system 20 can be easily reduced.

  Further, in the present embodiment, as described above, the laser light source units 1-R, 1-G, and 1-B are configured by a red semiconductor laser, a green semiconductor laser, and a blue semiconductor laser, respectively, so that the semiconductor laser is small. Therefore, the laser light source units 1-R, 1-G, and 1-B can be made small. For this reason, the plane area and thickness of the scanning optical system 20 can be easily reduced.

  Referring to FIG. 1, assuming that the mobile terminal 40 is installed on an installation base (not shown) and projection is performed, laser light is emitted from a surface 40 a that faces the opposite side to the installation base side. By doing so, the laser light can be advanced toward the projection surface 41 while the mobile terminal 40 is kept thin. In this case, it is not necessary to tilt the mobile terminal 40 during projection.

  Here, when the environmental temperature rises, the back focus changes due to a decrease in the refractive index and thermal expansion of the collimating lens COL. Therefore, when the divergent light beam emitted from the laser light source is emitted from the lens portion LS of the collimator lens COL, the divergent light beam may not be a predetermined substantially parallel light beam but may be a noticeable finite light beam. On the other hand, according to the present embodiment, the leg length T of the collimating lens COL is determined so as to satisfy the expression (1), so that the leg LG expands and contracts (T ±) according to the environmental temperature change. ΔT), so that the change in back focus can be canceled and the collimating lens COL can emit a predetermined substantially parallel light beam even when the environmental temperature changes.

  Furthermore, since the collimating lens COL has a pair of cutouts CT, the laser chip CP is not sealed by the collimating lens COL and is not sealed to the collimating lens COL even after the end surface of the leg LG is bonded to the stem ST. Then, it is cooled by the external air that is evoked and the temperature rise of the collimating lens COL can be suppressed, so that the influence of the change in back focus can be effectively suppressed.

  Further, when a plurality of laser light source units are used side by side as in the present embodiment, the cooling effect can be further enhanced by devising the arrangement of adjacent collimating lenses COL. Here, a collimating lens COL is arranged as shown in FIG. For example, in the arrangement example shown in FIG. 9, when the straight line L passing through the center of the adjacent laser chip CP is translated to the leg LG side within the height of the cutout CT, the cutout of the collimating lens COL facing the laser chip CP is obtained. Passes CT. When the collimating lens COL is arranged in this way, a ventilation path can be formed along the straight line L, so that the heated air in the collimating lens COL is removed from the notch CT by performing ventilation using a not-shown forced fan or the like. It is easy to escape and ventilation performance improves. By taking such a heat countermeasure, the leg LG can be shortened, and a compact projection image display apparatus can be provided.

  On the other hand, in the arrangement example shown in FIG. 10, when the straight line L passing through the center of the adjacent laser chip CP is translated toward the leg LG side, the position (notch) of the leg LG of the collimating lens COL facing the laser chip CP is obtained. It passes through a position other than CT). When using natural convection, air heated in the collimating lens COL does not escape along the straight line L, but is discharged from the notch CT intersecting with the air, so that there is little possibility of entering the adjacent collimating lens COL. A uniform temperature rise of each collimating lens can be secured. By taking such a heat countermeasure, the leg LG can be shortened, and a compact projection image display apparatus can be provided.

Hereinafter, examples suitable for the above-described embodiment will be described. The following are the specifications of this example.
(Light source specifications)
Light source wavelength: 450nm
Horizontal beam divergence angle θ // (full width at half maximum): 8.5 °
Vertical beam divergence angle θ⊥ (full width at half maximum): 23.0 °
Wavelength change with respect to temperature change (dλ / dT): 0.05 nm / ° C
(Specifications of collimating lens)
Lens outer diameter (φ): 4.0mm
Leg length (T): 2.0mm
Focal length: 1.6mm
Distance from light source side optical surface to condensing position (BF): 1.516mm
Numerical aperture: 0.4
(Characteristics of collimating lens resin material)
Refractive index change with respect to temperature change (dn / dT): -9.0 × 10 ^-5 / ° C
Linear expansion coefficient: 7.0 × 10 ^-5

Table 1 shows lens data of this example. In the table, Ri is the radius of curvature, di is the position in the optical axis direction from the i-th surface to the (i + 1) -th surface, and ni is the refractive index of each surface. In the following (including lens data in the table), a power of 10 (for example, 2.5 × 10 ⁻³ ) may be expressed using E (for example, 2.5 × E−3). When the coordinates of the center of the light exit surface of the light source (laser chip) are the origin, and the optical axis is a line passing through the origin and perpendicular to the exit surface, the optical surfaces of the collimating lens are expressed by the following equation (1). The aspherical surface is axisymmetric about the optical axis, which is defined by a mathematical formula in which the coefficient shown in 2 is substituted.

  Here, X (H) is the distance from the origin in the optical axis direction, κ is the conical coefficient, Ai is the aspherical coefficient, H is the distance (radius) from the optical axis in the direction perpendicular to the optical axis, and r is the radius of curvature.

  The beam diameter at the projection position when the temperature rises by 30 ° C. from the design temperature is compared with Table 3 for the above-described embodiment and a comparative example in which the specifications are the same as the embodiment but only the leg portion is not provided. Show. In this embodiment, the leg portions are provided on the collimating lens, whereby the distance between the light source side optical surface and the condensing position increases by 0.0042 mm due to expansion when the temperature rises by 30 ° C. Thus, as shown in Table 3, it can be seen that in this example, the change in the beam diameter before and after the temperature change can be effectively suppressed as compared with the comparative example.

DESCRIPTION OF SYMBOLS 1 Laser light source part 2 Scan part 3 Scan mirror 3a Reflective surface 4 Fixed frame 5 Drive part 5a Piezoelectric element 5b Electrode 6 Movable frame 7 Torsion bar 8 Projection mirror 20 Scan optical system 20a Case member 22 Dichroic mirror 23 Dichroic mirror 24 Mirror 25 Mirror 27 Mirror 40 Mobile terminal 40a Surface 41 Projection surface 100 Projector BF Distance from light source side optical surface to condensing position COL Collimating lens CP Semiconductor laser chip CT Notch FL Flange FP Surface FR Frame L Straight LD Semiconductor laser LG Leg LS Lens Part SM Submount ST Stem part T Leg length

Claims (8)

A lens for a projection image display device,
The lens is made of integrally molded plastic, and has a lens part that converts a light beam emitted from a light source into parallel light or convergent light, and a leg part that holds the lens part,
The leg is fixed to at least a part of the end of the leg with respect to the base that supports the light source, and has an opening or a notch at least at one position of the leg,
A length T (mm) of the leg portion satisfies the following expression.
BF ≤ T ≤ φ (1)
However,
BF: Distance from light source side optical surface to condensing position (mm)
φ: Lens outer diameter (mm)   The lens according to claim 1, wherein the leg portion is formed with at least two notches extending from the end portion toward the lens portion.   3. The lens according to claim 1, wherein a shape of the lens when viewed from the optical axis direction includes two linear portions that are substantially parallel with at least the optical axis interposed therebetween.   The lens according to claim 1, wherein a thickness of the leg portion increases from the end portion toward the lens portion.   The lens according to claim 1, wherein a diffractive structure is formed in the lens portion.   A projection image display device using the lens according to claim 1.   A plurality of pairs of the light source and the lens are provided, and when the straight line passing through the center of the adjacent light source is translated to the leg side in the optical axis direction of the lens, the straight line moved by a predetermined amount is the leg. The projection image display device according to claim 6, wherein the projection image display device passes through an opening or notch of the portion.   A plurality of pairs of the light source and the lens are provided, and when the straight line passing through the center of the adjacent light source is translated to the leg side in the optical axis direction of the lens, the two lenses adjacent to the straight line The projection image display device according to claim 6, wherein the projection image display device does not pass through an opening or a notch of the leg.

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