JP2013045043A - Image display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image display device whose projection angle can be adjusted to direct the projection upward from a desktop mounting surface with a simple configuration.SOLUTION: An image display device built in a notebook computer includes a projector lens 28 comprising a lens portion 101 which is made object-side telecentric by combining concave and convex lenses, and a prism portion 102 located on the projection side, and comprising two prisms 103 and 104 combined such that the trapezoid cross-sections thereof are pointing to opposite directions, which slant the projection direction with respect to the optical axis C of the lens portion. By making the slant point above the optical axis of the lens portion, outgoing light beam from a side face of the device is directed upward without having to provide a hinge mechanism for folding the image display device to point the emission window upward, which simplifies the mechanism of image display devices capable of projecting images obliquely upward.

Description

  The present invention relates to an image display device built in various electronic devices.

  In recent years, a technique using a semiconductor laser as a light source of an image display device has attracted attention. This semiconductor laser has better color reproducibility, instantaneous lighting, longer life, and higher power consumption compared to mercury lamps that have been widely used in image display devices. It has various advantages, such as being able to be made and being easy to miniaturize.

  The advantage of such an image display device using a semiconductor laser is convenient when it is built in a portable electronic device. For example, a technique for incorporating an image display device using a semiconductor laser into a mobile phone terminal is known. (See Patent Document 1). When the image display device is built in the portable electronic device in this way, the screen can be enlarged and displayed on the screen as needed, so that convenience can be improved.

  As described above, an image display device using a semiconductor laser as a light source can improve convenience even when incorporated in a portable information processing device (so-called notebook personal computer). In this case, a main body on which a keyboard is disposed. It is conceivable to house the image display device inside the housing of the unit. When the image display device is built in the notebook computer as described above, the casing is formed flat, and the projected image is emitted from the side surface of the notebook computer toward the side.

  When such a notebook personal computer is placed on the desk, the image display device is brought close to the placement surface on the desk, and a part (lower side) of the laser beam emitted from the image display device is blocked by the placement surface. Sometimes. In such a state, the lower part of the screen displayed on the screen is missing, and there is a problem that the screen cannot be displayed properly on the screen.

  Therefore, when an electronic device with a built-in image display device is placed on the desk and used, it is avoided that the laser beam is blocked by the placement surface on the desk and the screen is not displayed on the screen. For example, a shift mechanism and a tilt mechanism are provided so that the projection direction can be changed (see Patent Document 2).

JP 2007-316393 A JP-A-2-195386

  On the other hand, in the case where the shift mechanism, the tilt mechanism, or the like is provided, the layout of other parts is restricted due to the provision of the mechanism. In the case of the tilt mechanism, it is necessary to hold the housing of the image display device at the tilted position. However, since the lens, the control device, and the like are heavy, increasing the strength of the holding device increases the cost of parts. There is also a problem of becoming.

  The present invention has been devised to solve such problems of the prior art, and its main purpose is to use an electronic device with a built-in image display device mounted on a desk. Another object of the present invention is to provide an image display device configured to be able to direct the projection angle upward from the mounting surface on the desk with a simple configuration.

  The image display device of the present invention is an image display device including a projection lens for projecting laser light emitted from a light source toward a screen means, and the projection lens enlarges an image of the laser light. And a prism portion for tilting the projection direction of the laser light emitted from the lens portion with respect to the optical axis of the lens portion, and the prism portion includes the light portion. A trapezoidal cross section viewed from a direction orthogonal to the axis is composed of two prisms combined in opposite directions.

  According to the present invention, since the prism is provided so that the outgoing light emitted from the lens portion is emitted with an inclination with respect to the optical axis of the lens portion, the inclination is above the optical axis of the lens portion. Thus, in the image display device provided so as to project from the side surface of the notebook computer to the side, without providing a hinge mechanism that folds the middle part and faces the exit window upward, Since the emitted light can be directed upward, the mechanism of the image display device that enables projection upward obliquely can be simplified, and the image display device can be made compact.

The perspective view which shows the example which incorporated the image display apparatus by this invention in the portable information processing apparatus. The schematic block diagram of the optical engine part incorporated in an optical engine unit. The schematic diagram which shows the condition of the laser beam in a green laser light source device. The block diagram of each lens component of a projection lens. The table | surface which shows each item of the lens in FIG. Explanatory drawing which shows image height and object height. The figure which shows spherical aberration. The figure which shows astigmatism. The figure which shows a distortion aberration. The figure which shows chromatic aberration. 4A is a lateral aberration diagram showing coma aberration of P1, FIG. 4B is P2, FIG. 4C is P3 of FIG. 4, and FIG. 4D is P4 of FIG. The side view which shows the lens part and prism part of a projection lens. The figure which shows the chromatic aberration suppression point by a prism part. The figure corresponding to FIG. 12 which shows 2nd Embodiment. The figure which shows the point which changes the projection direction of 2nd Embodiment.

  1st invention made | formed in order to solve the said subject is an image display apparatus provided with the projection lens for projecting the laser beam radiate | emitted from a light source toward a screen means, Comprising: The said projection lens is the said A lens part that combines a concave lens and a convex lens to enlarge the image of the laser light, and a prism part for tilting the projection direction of the laser light emitted from the lens part with respect to the optical axis of the lens part, The prism portion includes two prisms in which trapezoidal cross sections viewed from a direction orthogonal to the optical axis are combined in directions opposite to each other.

  According to this, since the prism is provided so that the emitted light emitted from the lens portion is emitted with an inclination with respect to the optical axis of the lens portion, by setting the inclination above the optical axis of the lens portion, In the image display device provided to project from the side surface of the notebook computer to the side, the emitted light from the side surface is provided without providing a hinge mechanism that causes the intermediate portion to be folded and the output window to face upward. Therefore, the mechanism of the image display device that enables projection upward obliquely can be simplified, and the image display device can be made compact.

  According to a second invention, in the first invention, the lens portion includes at least three lens components so that the lens portion is telecentric on the object side (light modulator 25 side), and the conjugate of the lens portion. Each outer lens component disposed on both outer sides facing the point (screen S and light modulator 25) is a plastic lens, and the aperture position of the lens portion is between the outer lens components, and the lens portion A lens component other than the outer lens component that is closest to the aperture position is a glass lens.

  According to this, since the lens components on both outer sides of the lens portion are plastic lenses, the lens shape can be easily changed to a free shape, so the projection side lens component is an aspheric lens and a wide field of view is obtained. Both outer lens components can be easily processed so that the opposite outermost lens components can be telecentric and ensure a long back focus. The lens component close to the stop position where the chief rays that increase the energy density of the light are condensed is composed of a glass lens, thereby ensuring high light resistance (particularly light resistance of blue laser light) and relatively high energy. Since the lens component at a low density position (screen S and light modulator 25 side) is composed of a plastic lens, it can easily cope with a complex shape such as an aspheric surface, so that high resolution, high brightness, and long focal length are achieved. It is possible to configure a projection lens that enables a small number of lens components.

  According to a third invention, in the first or second invention, the prism portion is provided so as to be rotatable around an optical axis of the lens portion.

  According to this, when the optical axis of the lens portion is, for example, a direction horizontal to the mounting surface, it is possible to project obliquely in an arbitrary direction of 360 degrees around the optical axis with the axis inclined with respect to the optical axis as the emission direction. It is possible to project an image at an arbitrary position without moving the image display device, and it is easy to use.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a perspective view showing an example in which an image display device 1 according to the present invention is built in a portable information processing device 2. A portable information processing device (for example, a notebook personal computer) 2 has a main body 3 in which a control board (not shown) on which a CPU, a memory, and the like are mounted, and a display unit 4 having a liquid crystal panel. The body part 3 and the display part 4 are connected by a hinge part 5 so that the body part 3 and the display part 4 are overlapped to enhance portability.

  A keyboard 6 and a touch pad 7 are provided on the upper surface 8 a of the housing 8 of the main body 3. In addition, on the back surface side of the keyboard 6 in the housing 8 of the main body 3, an accommodation space in which a peripheral device such as an optical disk device is accommodated in a replaceable manner, a so-called drive bay, is formed. 1 is attached.

  The image display device 1 includes a housing 11 and a movable body 12 provided so as to be able to be taken in and out of the housing 11. The movable body 12 controls an optical engine unit (first unit) 13 in which an optical component for projecting the image Im by the laser light onto the screen S is accommodated, and an optical component in the optical engine unit 13. It is comprised with the control unit (2nd unit) 14 in which the board | substrate etc. were accommodated.

  FIG. 2 is a schematic configuration diagram of the optical engine unit 15 built in the optical engine unit 13. The optical engine unit 15 includes, as light sources, a green laser light source device 22 that outputs green laser light, a red laser light source device 23 that outputs red laser light, and a blue laser light source device 24 that outputs blue laser light. Prepare. The optical engine unit 15 includes a liquid crystal reflection type light modulator 25 that modulates the laser light from each of the laser light source devices 22 to 24 according to the video signal, and the laser light from each of the laser light source devices 22 to 24. Is reflected to irradiate the optical modulator 25 and transmits the modulated laser light emitted from the optical modulator 25, and the laser light emitted from each of the laser light source devices 22 to 24 is polarized light splitter 26. And a projection lens (projection optical system) 28 for projecting the image Im of the modulated laser light transmitted through the polarization beam splitter 26 onto the screen S. Each laser light source device 22-24 may use a semiconductor laser.

  The optical engine unit 15 displays a color image by a so-called field sequential method, and laser beams of each color are sequentially output from the laser light source devices 22 to 24 in a time-sharing manner, and an image by the laser beam of each color is visually displayed. It is recognized as a color image by the afterimage effect.

  The relay optical system 27 includes collimator lenses 31 to 33 that convert the laser beams of the respective colors emitted from the laser light source devices 22 to 24 into parallel beams, and the laser beams of the respective colors that have passed through the collimator lenses 31 to 33 in a predetermined direction. First and second dichroic mirrors 34 and 35 guided to, a diffusion plate 36 for diffusing the laser light guided by the dichroic mirrors 34 and 35, and a field lens for converting the laser light that has passed through the diffusion plate 36 into a convergent laser 37.

  Assuming that the side from which the laser light is emitted from the projection lens 28 toward the screen S is the front side, the blue laser light is emitted backward from the blue laser light source device 24, and a green laser is emitted with respect to the optical axis of the blue laser light. The green laser light and the red laser light are emitted from the green laser light source device 22 and the red laser light source device 23 so that the optical axis of the light and the optical axis of the red laser light are orthogonal to each other. And the green laser light are guided to the same optical path by the two dichroic mirrors 34 and 35. That is, the blue laser light and the green laser light are guided to the same optical path by the first dichroic mirror 34, and the blue laser light, the green laser light, and the red laser light are guided to the same optical path by the second dichroic mirror 35.

  The first and second dichroic mirrors 34 and 35 are formed with films for transmitting and reflecting laser light of a predetermined wavelength on the surface, and the first dichroic mirror 34 transmits blue laser light. And reflects the green laser light. The second dichroic mirror 35 transmits red laser light and reflects blue laser light and green laser light.

  Each of these optical members is supported by the housing 41. The housing 41 functions as a radiator that dissipates heat generated by the laser light source devices 22 to 24, and is formed of a material having high thermal conductivity such as aluminum or copper.

  The green laser light source device 22 is attached to an attachment portion 42 formed on the housing 41 in a state of protruding toward the side. The attachment portion 42 is provided in a state of protruding in a direction perpendicular to the side wall portion 44 from a corner portion where the front wall portion 43 and the side wall portion 44 that are respectively positioned in front and side of the accommodation space of the relay optical system 27 intersect. ing. The red laser light source device 23 is attached to the outer surface side of the side wall 44 while being held by the holder 45. The blue laser light source device 24 is attached to the outer surface side of the front wall portion 43 while being held by the holder 46.

  The red laser light source device 23 and the blue laser light source device 24 are configured by a so-called CAN package, and the optical axis is positioned on the central axis of the can-shaped exterior portion with the laser chip that outputs the laser light supported by the stem. The laser beam is emitted from a glass window provided in the opening of the exterior part. The red laser light source device 23 and the blue laser light source device 24 are fixed to the holders 45 and 46 by, for example, press-fitting into the mounting holes 47 and 48 formed in the holders 45 and 46. The heat generated by the laser chips of the blue laser light source device 24 and the red laser light source device 23 is transmitted to the housing 41 through the holders 45 and 46 to be dissipated, and each of the holders 45 and 46 has a thermal conductivity such as aluminum or copper. It is made of a high material.

  The green laser light source device 22 includes a semiconductor laser 51 that outputs excitation laser light, a FAC (Fast-Axis Collimator) lens 52 that is a condensing lens that condenses the excitation laser light output from the semiconductor laser 51, and a rod. A lens 53, a solid-state laser element 54 that outputs a basic laser beam (infrared laser beam) when excited by an excitation laser beam, and converts a wavelength of the basic laser beam to output a half-wavelength laser beam (green laser beam) A wavelength conversion element 55, a concave mirror 56 that forms a resonator together with the solid-state laser element 54, a glass cover 57 that prevents leakage of excitation laser light and fundamental wavelength laser light, and a base 58 that supports each part, And a cover body 59 that covers each part.

  The green laser light source device 22 is fixed by attaching the base 58 to the mounting portion 42 of the housing 41, and a required width (for example, 0.5 mm) between the green laser light source device 22 and the side wall portion 44 of the housing 41. The following gaps are formed. This makes it difficult for the heat of the green laser light source device 22 to be transmitted to the red laser light source device 23, suppresses the temperature rise of the red laser light source device 23, and allows the red laser light source device 23 with poor temperature characteristics to operate stably. Can do. Further, in order to secure a required optical axis adjustment allowance (for example, about 0.3 mm) of the red laser light source device 23, a required width (for example, 0.3 mm or more) is provided between the green laser light source device 22 and the red laser light source device 23. ) Is provided.

  FIG. 3 is a schematic diagram showing the state of laser light in the green laser light source device 22. The laser chip 61 of the semiconductor laser 51 outputs excitation laser light having a wavelength of 808 nm. The FAC lens 52 reduces the spread of the first axis of the laser beam (the direction perpendicular to the optical axis direction and along the drawing sheet). The rod lens 53 reduces the spread of the slow axis of laser light (in the direction perpendicular to the drawing sheet).

The solid-state laser element 54 is a so-called solid-state laser crystal, and is excited by excitation laser light having a wavelength of 808 nm that has passed through the rod lens 53 to output fundamental wavelength laser light (infrared laser light) having a wavelength of 1064 nm. This solid-state laser element 54 is obtained by doping an inorganic optically active substance (crystal) made of Y (yttrium) VO ₄ (vanadate) with Nd (neodymium), and more specifically, YVO _{4 as} a base material. The Y is doped by substitution with Nd ⁺³ which is an element that emits fluorescence.

  On the side of the solid-state laser element 54 facing the rod lens 53, a film having a function of preventing reflection of excitation laser light having a wavelength of 808 nm and high reflection of fundamental wavelength laser light having a wavelength of 1064 nm and half-wavelength laser light having a wavelength of 532 nm. 62 is formed. On the side of the solid-state laser element 54 facing the wavelength conversion element 55, a film 63 having an antireflection function for a fundamental wavelength laser beam having a wavelength of 1064 nm and a half wavelength laser beam having a wavelength of 532 nm is formed.

  The wavelength conversion element 55 is a so-called SHG (Second Harmonics Generation) element, which converts the wavelength of a fundamental wavelength laser beam (infrared laser beam) having a wavelength of 1064 nm output from the solid-state laser element 54 to a half-wavelength laser having a wavelength of 532 nm. Light (green laser light) is generated.

  On the side of the wavelength conversion element 55 facing the solid-state laser element 54, a film 64 having functions of preventing reflection of the fundamental wavelength laser light having a wavelength of 1064 nm and highly reflecting the half wavelength laser light having a wavelength of 532 nm is formed. On the side of the wavelength conversion element 55 facing the concave mirror 56, a film 65 having an antireflection function for the fundamental wavelength laser beam having a wavelength of 1064 nm and the half wavelength laser beam having a wavelength of 532 nm is formed.

  The concave mirror 56 has a concave surface on the side facing the wavelength conversion element 55, and this concave surface has a function of high reflection with respect to a fundamental wavelength laser beam with a wavelength of 1064 nm and antireflection with respect to a half wavelength laser beam with a wavelength of 532 nm. A film 66 is formed. As a result, the fundamental wavelength laser beam having a wavelength of 1064 nm resonates and is amplified between the film 62 of the solid-state laser element 54 and the film 66 of the concave mirror 56.

  In the wavelength conversion element 55, a part of the fundamental wavelength laser light having a wavelength of 1064 nm incident from the solid-state laser element 54 is converted into a half-wavelength laser light having a wavelength of 532 nm, and the fundamental wavelength of 1064 nm that has passed through the wavelength conversion element 55 without being converted is converted. The wavelength laser beam is reflected by the concave mirror 56 and is incident on the wavelength conversion element 55 again, and is converted into a half-wavelength laser beam having a wavelength of 532 nm. The half-wavelength laser light having a wavelength of 532 nm is reflected by the film 64 of the wavelength conversion element 55 and emitted from the wavelength conversion element 55.

  Here, the laser beam B1 incident on the wavelength conversion element 55 from the solid-state laser element 54, converted in wavelength by the wavelength conversion element 55, and emitted from the wavelength conversion element 55, and once reflected by the concave mirror 56 and converted in wavelength. In the state where the laser beam B2 incident on the element 55, reflected by the film 64 and emitted from the wavelength conversion element 55 overlaps with each other, the half-wavelength laser light having a wavelength of 532 nm and the fundamental wavelength laser light having a wavelength of 1064 nm interfere with each other. Cause output to drop.

  Therefore, here, the wavelength conversion element 55 is inclined with respect to the optical axis direction so that the laser light beams B1 and B2 do not overlap each other by the refraction action on the entrance surface and the exit surface. Interference between the wavelength laser beam and the fundamental wavelength laser beam having a wavelength of 1064 nm is prevented, so that a decrease in output can be avoided.

  The glass cover 57 shown in FIG. 2 is formed with a film that does not transmit these laser beams in order to prevent the excitation laser beam having a wavelength of 808 nm and the fundamental wavelength laser beam having a wavelength of 1064 nm from leaking to the outside. ing.

  Each housing of the optical engine unit 13 and the control unit 14 constituting the movable body 12 has a flat box shape with a short dimension in the height direction. Sliders that slide along guide rails provided in the housing 11 are provided on both side edges of the housings of the optical engine unit 13 and the control unit 14 (not shown). Then, as indicated by an arrow A, the movable body 12 is inserted into and removed from the housing 11. An exit window 74 is provided at the end of the optical engine unit 13 corresponding to the side surface of the notebook computer 2, and the exit window 74 passes through the projection lens 28 (see FIG. 2) of the optical engine unit 15. The emitted laser beam is emitted.

  Next, with reference to FIG. 4, a specific configuration of each lens component showing the first embodiment of the projection lens 28 to which the present invention is applied will be described. In addition, although each lens component is shown with sectional drawing, hatching is abbreviate | omitted from legibility. Further, the modulated outgoing light emitted from the right polarization beam splitter 26 in FIG. 4 is projected toward the screen S disposed on the left side of the drawing via the projection lens 28.

  The projection lens 28 includes a first lens (first lens component) L1, a second lens (second lens component) L2, a third lens (third) in order from the first conjugate point side on the projection side (left side in FIG. 4). A lens component L3 and a fourth lens (fourth lens component) L4 are arranged coaxially. The first and fourth lenses L1 and L4 are plastic lenses formed of a synthetic resin material, and the second and third lenses L2 and L3 are glass lenses formed of a glass material.

  The first lens L1 is formed in a pseudo concave meniscus shape whose central portion protrudes toward the projection side and has negative refractive power. The second lens L2 is a biconvex spherical lens, and the third lens L3 is a biconcave spherical lens. The fourth lens L4 is formed in a pseudo biconvex shape and has a positive refractive power.

  Table 1 shown in FIG. 5 shows the specifications of the lens in FIG. The conditions for setting the lens data in Table 1 are as follows: the F value is 2.8, the focal length is 7.3 mm, the image height of the light modulator 25 is 2.794 mm, and the object height of the projection image Im on the screen S is 385. The distance between the center of the lens surface on the screen S side of the first lens L1 and the screen S is 1000 mm. As shown in FIG. 6, the image height is the height H of the image on the diagonal line from the center Pc of the rectangular irradiation surface of the optical modulator 25 toward the corner portion Pe, and the above numerical value is the maximum value. Similarly, the object height is the height H of the image on the diagonal line from the center Pc of the rectangular projection surface (Im) on the screen S to the corner Pe, and the above numerical value is the maximum value. The weighting of each color laser beam is set to 1 for blue laser beam and red laser beam, and 2 for green laser beam.

  The surface numbers in Table 1 correspond to f2 to f11 shown in FIG. 4, correspond to the order of the lens surfaces from the projection side (f1 corresponds to the screen S, f12 corresponds to the light modulator 25), and STO is Indicates the aperture. The stop STO is provided at the focal position. The surface shape indicates whether the lens surface is spherical or aspherical, r is the radius of curvature of each lens surface, and d is from each optical surface f (n) to the next optical surface f (n + 1). (N is 1 to 10), nd is the refractive index with respect to the d-line (wavelength 587.6 nm), νd is the Abbe number with respect to the d-line, D is the aperture diameter, and Co is The conic number of the aspheric lens is shown respectively. The unit of length is “mm” unless otherwise specified.

  Next, aspheric data is described. The fourth-order, sixth-order, eighth-order, tenth-order, and twelfth-order coefficients of the aspheric coefficient CEn are represented by CE4, CE6, CE8, CE10, and CE12, respectively.

In face number f2,
CE4 = −0.00019292138
CE6 = 1.7519259e-5
CE8 = −2.6333344e−7
CE10 = −2.897131e−8
CE12 = 1.0282375e-9
It is.

In surface number f3,
CE4 = 0.00048703321
CE6 = −0.00021337964
CE8 = 9.3720993e-6
CE10 = 2.6656592e-6
CE12 = −3.532074e−7
It is.

In surface number f8,
CE4 = −0.00144457748
CE6 = 5.699218e-5
CE8 = -9.94124343e-7
CE10 = -4.38446295e-8
CE12 = 2.2483199e-9
It is.

In face number f9,
CE4 = −6.1165958e−5
CE6 = 7.5395918e-6
CE8 = −6.155347e−8
CE10 = −6.908151e−9
CE12 = 6.04556066e-10
It is.

  In the first embodiment, as shown in FIG. 4, distances R1 to R4 between the principal ray passing through the optical axis C and the points where the principal ray having the highest field angle passes through the lenses L1 to L4 are defined as radii. Assuming that the area of the circle to be irradiated is the irradiation range of each of the lenses L1 to L4, for example, assuming that laser light having a wattage of W1 is irradiated, the energy densities E1 to E4 of the lenses L1 to L4 En = W1 / (π × Rn × Rn).

  Here, as shown in FIG. 4, the sizes of R1 to R4 are R4> R1> R3> R2. Therefore, the energy density of the second lens L2 is the highest. As described above, the second lens L2 is a glass lens, and the second lens L2, which is a lens component arranged at a position where the energy density is high, is a glass lens, thereby ensuring a large light resistance of the second lens L2. Is done.

  In recent projectors, when the amount of light from the light source is increased in response to a request to project a brighter image, the energy density (light power density) increases accordingly, and the light irradiation area is reduced in the vicinity of the stop STO. In addition to an increase in energy density, the stop STO is located at a conjugate position of the light source in the projector optical system, and a portion where the amount of laser light from the laser light source devices 22 to 24 is concentrated appears at the position of the stop STO. .

  In the case of blue laser light, the energy density of the central portion at the stop STO position, that is, the energy density of the principal ray portion at the projection lens 28 increases due to the Gaussian distribution as the far field pattern. In such a case, if a plastic lens is disposed in the vicinity of the stop STO, the energy density at the center of the lens increases, and the photodegradation of the resin of the lens is accelerated. When the transmittance of the resin such as yellowing color is lowered or the resin itself is burnt due to light deterioration, the function as a lens is greatly lowered.

  On the other hand, in the lens at a position far away from the vicinity of the stop STO, the chief ray spreads greatly, so that the light quantity distribution of the laser light is widened, and the light quantity distribution becomes more uniform, and the energy density incident on the lens is reduced. is there. The first and fourth lenses L1 and L4 made of plastic lenses are arranged at such positions, and the deterioration of the resin material of the first and fourth lenses L1 and L4 is suppressed. The light source is not limited to the semiconductor laser, and any light source having a function of illuminating the light modulator 25 such as an LED (light emitting diode) OLED (organic EL) may be used.

  In addition, only a limited resin material can be used as a lens material for blue laser light that greatly affects the deterioration of the resin material. However, in a lens processed with the lens material, a combination of the refractive index and the Abbe number (dispersion) is limited, and a lens intended for a so-called achromatic lens for reducing chromatic aberration cannot be obtained. In addition, there may be a demand to increase the light quantity of the light source in the future.

  Therefore, it is effective to configure the achromatic lens with a glass lens. In addition, since the achromatic lens made of glass can be used without worrying about light resistance like a plastic lens, it can be arranged at a position close to the stop STO (high energy density) of the projection lens 28. is there. Then, as described above, the third lens L3 made of a glass lens is disposed at a position close to the stop STO, and an achromatic lens having a two-lens configuration is provided by using the fourth lens L4 made of another glass lens. ing.

  Next, each aberration of the projection lens 28 in the first embodiment will be described.

  First, FIG. 7 shows spherical aberration. In the figure, the vertical axis indicates the position of the image height H, the horizontal axis indicates the magnitude of deviation, the spherical aberration is 0, the solid line is blue laser light, the two-dot chain line is green laser light, and the broken line Is red laser light. The description of these figures is the same for other similar figures, and the description thereof is omitted. The spherical aberration in FIG. 7 is expressed as a function of image height at each wavelength of each color.

  FIG. 8 is a diagram showing field curvature and astigmatism. Each curve on the left side in the figure is sagittal data (Sd in the figure), each curve on the right side is tangential data Td, and ST is astigmatism. In the figure, the distance from the image plane to the paraxial image plane is expressed as a function of field coordinates.

FIG. 9 is a diagram showing distortion aberration. In the figure, the horizontal axis represents the distortion magnitude Dy as a percentage. The distortion magnitude Dy is given by the following equation, where Yc is the actual principal ray height and Yr is the reference ray height.
Dy = 100 × (Yc−Yr) / Yr

  FIG. 10 is a diagram showing lateral chromatic aberration. In the figure, the chromatic aberration of magnification is expressed as a function of the field of view, and the chromatic aberration of magnification of the blue and red laser beams when the green laser beam is used as a reference (the deviation is 0) is shown.

  FIG. 11 is a lateral aberration diagram showing coma aberration. In the figure, the center represents the chief ray, the horizontal axis represents the entrance pupil coordinates (maximum ± 20 μm), and the vertical axis represents the lateral aberration value at each entrance pupil coordinate. Lateral aberration represents the aberration of light as a pupil function. Also, (a), (b), (c), and (d) in FIG. 11 are points P1 (center), P2 (maximum image height position on the vertical axis passing through the center), P3 (center), respectively. , The maximum image height on the horizontal axis passing through), and P4 (corner). Specifically, assuming that P1 is 0 mm, the image heights are P2 = 1.44 mm, P3 = 2.4 mm, and P4 = 2.794 mm.

  According to the projection lens 28 configured in this way, each aberration is small as shown in FIGS. 7 to 11 and can be applied to a small projector without any problem.

  Although the projection lens 28 is made entirely of plastic lenses, the minimum number of lenses can be configured. However, as described above, resin lenses such as plastic lenses have a problem that variations in refractive index and Abbe number are small. . Furthermore, few materials have light resistance to blue laser light, and if used, the cost of the lens increases. Therefore, when a projection lens for a small projector is configured with only a plastic lens, it is difficult to realize high resolution, high brightness, and a long focal length. Further, it is necessary to reduce chromatic aberration in order to reduce the aberration at the point of advantage, and it is difficult to obtain a sufficient chromatic aberration if the number of lenses is too small.

  On the other hand, as described above, the first and fourth lenses L1 and L4 on both outer sides are plastic lenses, and the second and third lenses L2 and L3 between them are glass lenses. The point was eliminated, and it was possible to configure with a small number of lenses, ie, four lenses (L1 to L4), which is almost the minimum.

  Further, the second and third lenses L2 and L3 made of glass lenses are configured as compound lenses which are joined in close contact with each other with the same curvature of the lens surfaces (f6) adjacent to each other, and are positively refracted as a whole. It is power. Thereby, the position of the stop STO located between the first lens L1 and the second lens L2 can be brought closer to the second lens L2 made of a glass lens, and the energy density with respect to the first lens L1 made of a plastic lens can be further increased. It can be further reduced.

  Further, a resin lens such as a plastic lens has a problem that there are few variations in the refractive index and the Abbe number, but this is also addressed by the second and third lenses L2 and L3 made of glass lenses. Further, the Abbe number of the second lens L2 closer to the stop STO is made larger than the Abbe number of the third lens L3 farther. Accordingly, in addition to the effect of bringing the position of the stop STO closer to the second lens L2 as described above, chromatic aberration can be suitably reduced by combining different Abbe numbers.

  Further, since the first and fourth lenses L1 and L4 on the outer sides are plastic lenses, the lens shape can be easily changed to a free shape. The projection-side first lens L1 is aspherical to secure a wide field of view, and the opposite outermost fourth lens L4 is also aspherical to ensure telecentric and long back focus. The lenses L1 and L4 can be easily processed. In this way, as described above, it is possible to configure with a small number of lenses, which is the minimum of four lenses (L1 to L4).

  In this way, the lens portion 101 is constituted by the four lenses (L1 to L4). As shown in FIG. 12, a prism portion 102 is provided on the projection side of the lens portion 101 (the projection side of the first lens L1).

  The prism portion 102 is configured by stacking and arranging two prisms 103 and 104 in the direction along the optical axis C of the lens portion. The prisms 103 and 104 may be wedge prisms each having a trapezoidal cross-sectional shape when viewed from a direction orthogonal to the optical axis C (front and back direction in FIG. 12), and the upper and lower bases are opposite to each other. It is arranged to become. The figure shows a case where the notebook computer 2 is placed on a desk and projected, for example. In this case, the projection direction is directed upward so that the lower part of the projection is not blocked by the placement surface. As shown in the figure, the projection direction is changed upward by the prism portion 102.

  In order to make the projection direction upward, the projection-side prism 103 is provided with the lower bottom side facing upward, and the wedge angle (angle between both lens surfaces) θ1 is the first lens L1. Is larger than the wedge angle θ2 of the prism 104 closer to (θ1> θ2).

  As a result, as shown in FIG. 12, the light beam from the point Pc that coincides with the optical axis C of the optical modulator 25 travels on the optical axis C in the lens portion 101 as shown by the alternate long and short dash line in FIG. Although it is directed slightly downward at 104, the direction is changed upward by the prism 103, and light emitted from the projection lens 28 is emitted at an upward angle with respect to the optical axis C and is projected onto the screen S. The same applies to a light beam from the upper point of the optical modulator 25 (corresponding to P2 in FIG. 6) Pu (two-dot chain line in the drawing) and a light beam from the middle point Pd of the lower edge (solid line in the drawing). is there. As shown in the figure, the three lenses L2 to L4 pass through the focal point (near the stop STO), reach the prism portion 102 via the first lens L1, and are directed upward with respect to the optical axis C by the prism portion 102. It is emitted at an angle.

  Further, as described above, chromatic aberration can be suppressed by superimposing the two prisms 103 and 104 alternately. With reference to FIG. 13, description will be given of how to suppress chromatic aberration by the prisms 103 and 104 in the present embodiment. 13 representatively shows a red light beam Lr of red laser light (640 nm) and a blue light beam Lb of blue laser light (445 nm) emitted from an arbitrary point (Pd in FIG. 12) of the light modulator 25, and the red light beam Lr. Is indicated by a broken line, and the blue light ray Lb is indicated by a solid line. In addition, it has shown with the schematic diagram and emphasizes the change of the inclination of a light ray, etc. greatly.

  Using each of the lenses L1 to L4 having the above-described configuration, each color laser beam Lr, Lb passes through the prism portion 102 and the lens portion 101 to one point on the optical modulator 25 with respect to an arbitrary point on the screen S. The prisms 103 and 104 can be obtained so as to collect light. As shown in FIG. 13, when the points at which the red ray Lr and the blue ray Lb from one point on the screen S reach the projection 103 (screen S side) surface 103a of the prism 103 are Pa and Pb, respectively, the prism 103 Then, the red light ray Lr is refracted so as to reach the point Pc of the mating surface 103b (104a) between the prisms 103 and 104, and the blue light ray Lb is larger than the red light ray Lr so as to reach the point Pd on the surface 103b (104a). Refract.

  In the prism 104, the red light ray Lr is refracted from the point Pc so as to reach the point Pe on the surface 104b of the prism 104 on the light modulator 25 side, and the blue light ray Lb is reached from the point Pd to the point Pf on the surface 104b. Refract. On this surface 104b, the red light beam Lr and the blue light beam Lb are reversed up and down in the figure, but the blue light beam Lb is largely refracted on the surface 104b, so that the red light beam Lr and the blue light beam reach the light modulator 25. Lb can coincide with one point. Note that the green light beam is located between the red light beam Lr and the blue light beam Lb, and the illustration thereof is omitted.

  By designing the shape of each prism 103 and 104 and the distance to the light modulator 25 and the screen S so that each color light beam is refracted by the prisms 103 and 104 as described above, any one point of the light modulator 25 is designed. Can be focused on a point on the screen S. The design of each prism 103, 104 can be realized by optimizing the dispersion value or refractive index of the glass or resin material forming each prism. Then, by superimposing the two prisms 103 and 104 so that the thicknesses increase or decrease in opposite directions, chromatic aberration generated in one prism can be corrected by the other prism. As a result, the projection direction by the prism portion 101 can be changed and chromatic aberration can be suppressed, and a clear image Im can be projected onto the screen S without any problem.

  In addition, such a configuration of the projection lens 28 can provide the image display device 1 that projects in a direction inclined upward from the side surface of the notebook computer 2 without providing a structure such as a hinge mechanism or a shift mechanism. The thickness of the optical engine unit 13 can be 6.9 mm or less so that it can be accommodated in the casing of the notebook computer 2. The drive bay of the notebook personal computer 2 is generally 9.5 mm in height, and in order to fit in the drive bay with the height of 9.5 mm, the thickness of the optical system should be 6.9 mm or less. Can respond. By using aspherical lenses for the first and fourth lenses L1 and L4 made of plastic lenses as described above, the number of sheets can be reduced and the length in the optical axis direction can be shortened. Even when the size is 22 inches, it is possible to cope with it sufficiently, and it is possible to suppress an increase in length in the optical axis direction by a simple structure in which the two prisms 103 and 104 are overlapped. In addition, the total optical length, which is the distance from the first conjugate point side (projection side) surface of the first lens L1 to the light modulator 25, can also be made 40 mm or less, and can be accommodated in the casing of the notebook computer 2. It will not cause any trouble.

  The lens components of the first and fourth lenses L1 and L4 made of a resin material may be made of a cycloolefin polymer or a cycloolefin copolymer. Thereby, the light resistance (especially light resistance of blue laser light) of the lens components of the first and fourth lenses L1 and L4 made of plastic lenses can be further enhanced.

  Next, a second embodiment will be described with reference to FIG. FIG. 15 is a diagram corresponding to FIG. 12 described above, and the same portions as those described above are denoted by the same reference numerals and detailed description thereof is omitted.

  In the second embodiment, the lens barrel 105 that holds the lenses L1 to L4 of the lens portion 102 and the holder 106 that holds the prisms 103 and 104 of the prism portion 103 are separated from each other so that they can be coaxially contacted and separated. Is formed. The separation surface of the lens barrel 105 and the holder 106 has an annular end surface shape that surrounds the first lens L1 and faces in the direction of the optical axis C, and the separation surface on the lens barrel 105 side is a circle coaxial with the optical axis C. An annular groove 107 is provided, and an annular convex portion 108 that is coaxial with the optical axis C and is inserted into the groove 107 is provided on the separation surface on the holder 106 side. The annular convex portion 108 in the illustrated example is formed of a cylindrical member different from the holder 106 and has a shape that is partially embedded in the holder 106 in the axial direction, but is integrated with the holder 106. For example, it may be formed by molding or shaving.

  The lens barrel 105 and the holder 106 formed separately as described above are assembled by fitting the annular convex portion 108 into the annular groove 107. In addition, the annular convex portion 108 and the annular groove 107 are formed in an uneven sectional shape that can slide relative to each other around the axis, and a retaining mechanism (not shown) is provided between the lens barrel 105 and the holder 106. Thus, the lens barrel 105 and the holder 106 are provided coaxially and rotatably. The lens barrel 105 is fixed to the housing of the projection lens 28.

  Thereby, the image projected at a predetermined angle with respect to the optical axis C by rotating the holder 106 can be projected at an arbitrary position as indicated by Im1 to Im4 in FIG. In the figure, four positions (Im1 to Im4) are shown, but the projection can be performed in an arbitrary direction of 360 degrees around the optical axis C.

  In each of the above embodiments, the movable body 12 of the image display device 1 has been described as being projected from the notebook computer 2, but it is not always necessary to pull out from the notebook computer, and the exit window 74 is fixed to the side surface of the notebook computer 2. It may be. In that case, when the prism portion 101 is made rotatable as in the second embodiment, a part of the outer peripheral portion of the holder 106 is made to face the part of the case of the notebook computer 2, What is necessary is just to enable it to rotate the holder 106 with a fingertip.

  Further, a hinge mechanism may be provided between the optical engine unit 13 and the control unit 14 of the movable body 12. Thereby, the optical engine unit 13 can be tilted with respect to the control unit 14 in the pulled-out state, and the upward projection angle can be further increased.

  Although the present invention has been described above with reference to preferred embodiments, the present invention is not limited to such embodiments so that those skilled in the art can easily understand, and departs from the spirit of the present invention. It is possible to change appropriately within the range not to be. In addition, all the components shown in the above embodiment are not necessarily essential, and can be appropriately selected without departing from the gist of the present invention.

  The image display device according to the present invention can project in a direction having an angle with respect to the optical axis with a simple configuration, and the image display device can be made compact, and is useful as a small projector or the like.

DESCRIPTION OF SYMBOLS 1 Image display apparatus 22 Green laser light source apparatus 23 Red laser light source apparatus 24 Blue laser light source apparatus 28 Projection lens 101 Lens part 102 Prism part 103,104 Prism 105 Lens barrel 106 Holder L1-L4 First lens-Fourth lens

Claims (3)

An image display device comprising a projection lens for projecting laser light emitted from a light source toward a screen means,
The projection lens includes a lens portion that is a combination of a concave lens and a convex lens for enlarging the image of the laser light, and a prism for tilting the projection direction of the laser light emitted from the lens portion with respect to the optical axis of the lens portion. And having a part
2. The image display device according to claim 1, wherein the prism portion includes two prisms in which trapezoidal cross sections viewed from a direction orthogonal to the optical axis are combined in directions opposite to each other. The lens portion includes at least three or more lens components so as to be object-side telecentric, and each outer lens component disposed on both outer sides facing the conjugate point of the lens portion is a plastic lens,
The aperture position of the lens portion is between each outer lens component,
The image display device according to claim 1, wherein at least a lens component other than the outer lens component of the lens portion that is closest to the aperture position is a glass lens.   The image display device according to claim 1, wherein the prism portion is provided so as to be rotatable around an optical axis of the lens portion.

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