JP2012242637A - Image display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive and light-weight image display device by resinifying a lens which transmits light with low light density energy, in an optical system used in the image display device.SOLUTION: A projection optical part 8 guides light that is output from light emission means to the outside through a plurality of lens groups. Among a plurality of lenses that forms the lens groups in the projection optical part 8, lenses (L10, L13) at positions where irradiation light has low light power per unit area are resinified.

Description

  The present invention relates to an image display device including a light source device using a semiconductor laser or a light emitting diode (LED) as a light source.

  In recent years, a technique using a semiconductor laser or a light emitting diode as a light source of an image display device has attracted attention. In particular, semiconductor lasers have better color reproducibility, can be turned on instantaneously, have a longer life, and have higher efficiency and lower 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 performed and being easy to miniaturize (see, for example, Patent Document 1).

  Such an image display device projects and displays a required image on an external screen, and includes a three-color light source for color display and an optical system that guides the light output to the screen. This optical system is generally composed of a collimator lens, a field lens, a dichroic mirror, a projection lens, and the like.

JP 2007-316393 A

  The lens of the optical system used in the image display device is made of glass. Therefore, since these lenses are made of glass, there is a problem that the weight of the optical system is increased and the weight of the image display device itself is also increased. Furthermore, glass lenses are expensive and expensive to process. Therefore, the lens of the optical system is changed from glass to resin to reduce the cost, and the optical system and further the image display device are reduced in cost and weight. However, when these lenses are made of a resin, there is a problem that photodegradation of the resin (especially, degradation of the resin by light having a short wavelength such as blue) is accelerated, and the characteristics of the lens of the optical system cannot be maintained. Furthermore, recent image display devices are becoming smaller and higher in brightness (temperature increases as the brightness of the light source increases), so the temperature inside the device is increased and the temperature inside the device increases, resulting in light degradation of the resin. There is also the problem of being promoted.

  The present invention has been devised in order to solve such problems of the prior art, and the main purpose of the present invention is to control the light density energy of light passing through an optical system used in an image display device. An object of the present invention is to provide an image display device in which a low lens is resinized.

In order to solve the above problems, an image display device according to the present invention includes a blue light source that emits blue light, a green light source that emits green light, a red light source that emits red light, and each color output from each color light source. An optical system composed of a plurality of lens groups for guiding and projecting light to the outside, and among the lenses belonging to the plurality of lens groups, the light power per unit area of the blue light passing through the lens is 180 mW / mm ² While the following lenses were resinized, lenses other than the resinized lenses among the lenses belonging to the lens group were made of glass.

  According to the present invention, the lens material cost is maintained while maintaining the lens characteristics of the optical system by making the lens having a low optical power density of the light passing through the lens of the optical system used in the image display device made of resin. The reduction can reduce the cost of the lens, making it easier to mold the lens and reducing the number of manufacturing steps. Further, since the lens aspherical surface can be easily formed and the number of lens components can be reduced, the cost of the lens can be reduced, and the cost of the image display device can be reduced.

  Furthermore, the weight of the lens can be reduced by making the lens into a resin or reducing the number of lens components, and the weight of the image display device can be reduced and the weight can be reduced.

Schematic configuration diagram of an image display device in the present invention The figure which shows the transmittance | permeability after 1000-hour irradiation with respect to the light emission wavelength in this invention The figure which shows the transmittance | permeability after 1000 hours irradiation with respect to the optical power density in this invention The figure which shows the resin blue-light tolerance in this invention Schematic configuration diagram of a lens group of an image display device in the present invention Schematic configuration diagram of a lens group in the projection optical unit of the image display device in the present invention

According to the first aspect of the present invention, a blue light source that emits blue light, a green light source that emits green light, a red light source that emits red light, and each color light output from each color light source is guided to the outside and projected. An optical system composed of a plurality of lens groups, and among the lenses belonging to the plurality of lens groups, a lens whose optical power per unit area of blue light passing through the lenses is 180 mW / mm ² or less is made into a resin An image display device characterized in that a lens other than a resin-made lens among the lenses belonging to the lens group is made of glass, the light passing through the lens of the optical system used in the image display device By making the lens with low optical power density made of resin, the lens cost can be reduced by reducing the lens material cost while maintaining the lens characteristics of the optical system. Possible to reduce the man-hours. Further, since the lens aspherical surface can be easily formed and the number of lens components can be reduced, the cost of the lens can be reduced, and the cost of the image display device can be reduced.

  Furthermore, the weight of the lens can be reduced by making the lens into a resin or reducing the number of lens components, and the weight of the image display device can be reduced and the weight can be reduced.

  According to the second aspect of the present invention, the resinized lens is one of a plurality of lens groups and is located at the most downstream side of the optical path and is the most upstream in the light irradiation direction among the lenses of the projection optical unit that emits light to the outside. 2. The image display device according to claim 1, wherein the lens has a low optical power density of light passing through a lens of a projection optical unit used in the image display device. By making the resin, it is possible to reduce the cost of the lens by reducing the lens material cost while maintaining the lens characteristics of the optical part, and it becomes easy to mold the lens and reduce the number of manufacturing steps. Further, since the lens aspherical surface can be easily formed and the number of lens components can be reduced, the cost of the lens can be reduced, and the cost of the image display device can be reduced.

  Furthermore, it is possible to reduce the weight of the lens by reducing the weight of the image display device by reducing the weight of the lens by making the lens of the large and heavy projection optical unit out of the entire optical system or by reducing the number of lens components. Can greatly contribute.

According to a third aspect of the present invention, the resinized lens is one of a plurality of lens groups and is located in the uppermost stream of the optical path, and the lens is a collimator lens that converts light output from each color light source into parallel light. ^2. The image display device according to claim 1, wherein the blue light passing through the lens has a light power per unit area of 0 mW / mm ² , wherein the blue light does not pass through the red and green lights. By making the collimator lens lens that passes only through the resin, the lens cost can be reduced by reducing the lens material cost while maintaining the lens characteristics of the optical part, and the lens molding becomes easy and the number of manufacturing steps can be reduced. Further, since the lens aspherical surface can be easily formed and the number of lens components can be reduced, the cost of the lens can be reduced, and the cost of the image display device can be reduced.

  Furthermore, it is possible to reduce the weight of the lens by reducing the weight of the image display device by making the large and heavy collimator lens out of the entire optical system resin, or by reducing the number of lens components. can do.

  The invention according to claim 4 is the image display device according to any one of claims 1 to 3, wherein the material of the resinized lens is a polymer olefin resin or an acrylic resin. By using polymer olefin resin or acrylic resin for the resin of the lens with low optical power density of the light passing through the lens of the optical system used in the display device, the adverse effect of light on the resin can be reduced. , It is possible to prevent the deterioration of the optical characteristics.

  The image display device of the present invention will be described below with reference to the drawings. The first embodiment described below is a preferred specific example of the present invention, and the limitation of technically favorable conditions is described. However, the scope of the present invention is particularly limited to the present description in the following description. As long as there is no description which limits invention, it is not restricted to these conditions.

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic configuration diagram of an image display device 1 according to the present invention. This image display device 1 projects and displays a required image on a screen, and outputs a green laser light source device 2 that outputs green laser light (for example, emission wavelength 532 nm) and a red laser beam (for example, emission wavelength 655 nm). A red laser light source device 3 that emits light, a blue laser light source device 4 that outputs blue laser light (e.g., emission wavelength 445 nm), and a liquid crystal reflective type that modulates laser light from each of the laser light source devices 2 to 4 in accordance with a video signal. The spatial light modulator 5 and a polarization beam splitter that reflects the laser light from each of the laser light source devices 2 to 4 and irradiates the spatial light modulator 5 and transmits the modulated laser light emitted from the spatial light modulator 5. 6, the relay optical system 7 that guides the laser light emitted from each of the laser light source devices 2 to 4 to the polarization beam splitter 6, and the polarization beam splitter 6. And an optical system comprising a plurality of lens groups for irradiating the outside of the image display device 1 with the laser light output from each of the laser light source devices 2 to 4. 60 is formed.

  A part of the lens group of the optical system 60 and a part of the constituent lenses of the projection optical unit 8 are composed of lenses made of resin (details will be described later). In addition, a lens that is not resinated in a part of the lens group of the optical system 60 and a part of the constituent lenses of the projection optical unit 8 is made of glass.

  The image display device 1 displays a color image by a so-called field sequential method. Laser beams of each color are sequentially output from the laser light source devices 2 to 4 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 7 includes collimator lenses 11 to 13 that convert the laser beams of the respective colors output from the laser light source devices 2 to 4 into parallel beams, and the laser beams of the respective colors that have passed through the collimator lenses 11 to 13 in a predetermined direction. First and second dichroic mirrors 14 and 15, a lenticular lens 16 that diffuses the laser light guided by the dichroic mirrors 14 and 15, and a field lens that converts the laser light that has passed through the lenticular lens 16 into a convergent laser. 17.

  Assuming that the side from which the laser light is emitted from the projection optical unit 8 toward the screen S is the front side, the blue laser light is emitted backward from the blue laser light source device 4, and is green with respect to the optical axis of the blue laser light. The green laser beam and the red laser beam are emitted from the green laser light source device 2 and the red laser light source device 3 so that the optical axis of the laser beam and the optical axis of the red laser beam are orthogonal to each other. , And green laser light are guided to the same optical path by the two dichroic mirrors 14 and 15. That is, the blue laser light and the green laser light are guided to the same optical path by the first dichroic mirror 14, 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 15.

  The first and second dichroic mirrors 14 and 15 are formed with a film for transmitting and reflecting laser light having a predetermined wavelength on the surface, and the first dichroic mirror 14 transmits blue laser light. And reflects the green laser light. The second dichroic mirror 15 transmits red laser light and reflects blue laser light and green laser light.

  Each of these optical members is supported by the casing 21. The housing 21 functions as a radiator that dissipates heat generated by the laser light source devices 2 to 4 and is formed of a material having high thermal conductivity such as aluminum or copper.

  The green laser light source device 2 is attached to an attachment portion 22 formed in the housing 21 in a state of protruding toward the side. The mounting portion 22 is provided in a state of projecting in a direction perpendicular to the side wall portion 24 from a corner portion where the front wall portion 23 and the side wall portion 24 located respectively in front and side of the accommodation space of the relay optical system 7 intersect. ing. The red laser light source device 3 is attached to the outer surface side of the side wall portion 24 while being held by the holder 25. The blue laser light source device 4 is attached to the outer surface side of the front wall portion 23 while being held by the holder 26.

  The red laser light source device 3 and the blue laser light source device 4 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 3 and the blue laser light source device 4 are fixed to the holders 25 and 26 by, for example, press-fitting into mounting holes 27 and 28 provided in the holders 25 and 26. The heat generated by the laser chips of the blue laser light source device 4 and the red laser light source device 3 is transmitted to the housing 21 through the holders 25 and 26 to be dissipated, and each of the holders 25 and 26 has a thermal conductivity such as aluminum or copper. It is made of a high material.

  The green laser light source device 2 includes a semiconductor laser 31 that outputs excitation laser light, and a condensing lens that condenses the excitation laser light output from the semiconductor laser 31, a FAC (Fast-Axis Collimator) lens 32 and a rod lens 33. A solid-state laser element 34 that is excited by the excitation laser beam and outputs a basic laser beam (infrared laser beam), and a wavelength that converts the wavelength of the basic laser beam and outputs a half-wavelength laser beam (green laser beam) A conversion element 35, a concave mirror 36 that forms a resonator together with the solid-state laser element 34, a glass cover 37 that prevents leakage of excitation laser light and fundamental wavelength laser light, a base 38 that supports each part, and each part A cover body 39 is provided.

  The green laser light source device 2 is fixed by attaching a base 38 to the mounting portion 22 of the housing 21, and a required width (for example, 0.5 mm) between the green laser light source device 2 and the side wall portion 24 of the housing 21. The following gaps are formed. This makes it difficult for the heat of the green laser light source device 2 to be transmitted to the red laser light source device 3, suppresses the temperature rise of the red laser light source device 3, and allows the red laser light source device 3 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 3, a required width (for example, 0.3 mm or more) is provided between the green laser light source device 2 and the red laser light source device 3. ) Is provided.

  First, the conditions under which the lens used in the optical system 60 of the image display device 1 can be made into a resin will be described.

  The resinization of the lens used in the optical system 60 of the image display device 1 will be described with reference to FIGS. FIG. 2 is a diagram showing the transmittance after 1000 hours irradiation with respect to the emission wavelength in the present invention, FIG. 3 is a diagram showing the transmittance after 1000 hours irradiation with respect to the optical power density in the present invention, and FIG. 4 is in the present invention. It is a figure which shows resin blue-light tolerance.

  FIG. 2 shows the results of examination of the transmittance of the resin after irradiating the resin used for the lens with light of various wavelengths for 1000 hours. As shown in FIG. 2, the blue light (with a wavelength of 500 nm or less) has a large decrease in the transmittance of the resin compared to green light and red light. In other words, it is necessary to consider the influence of blue light when making a lens resin. On the other hand, it has been found that a lens through which only green light or red light passes may be made into a resin.

Next, the result of studying the optical power of blue light which has a great influence on the above-described lens resinization will be described. FIG. 3 shows the result of examining the transmittance of the resin after 1000 hours of irradiation to the resin used for the lens by changing the light power density (light power per unit area) of the blue light. As shown in FIG. 3, it was found that when the optical power density is higher than 180 mW / mm ² , the resin transmittance decreases greatly. Therefore, it was found that if the light power density of blue light is 180 mW / mm ² or less, the lens used in the optical system 60 of the image display apparatus 1 can be made resin.

  In addition, the type of resin used to make the lens resin was also examined. FIG. 4 shows the results of examining the blue light resistance of a resin material used when manufacturing a lens. As described above, the problem when the lens is made of resin is deterioration of the resin due to short wavelength light such as blue light.

  The materials examined and evaluated in the first embodiment are four types of polycarbonate resin, polystyrene resin, polymer olefin resin, and acrylic resin in consideration of the molding process and material strength.

The horizontal axis in FIG. 4 is the time when the above-mentioned four types of resin are irradiated with laser light having an optical power density of 30 mW / mm ^{2 with} an emission wavelength of 445 nm at an ambient temperature of 60 ° C., and the vertical axis in FIG. It is the transmittance | permeability of four types of resin.

  As shown in FIG. 4, when the lens material is made of polystyrene resin, the transmittance decreases as soon as the blue laser light is irradiated. Not suitable as. In addition, when the lens material is polycarbonate resin, the transmittance decreases when the irradiation time is about 400 hours when blue laser light is irradiated. Not suitable as material.

  On the other hand, when the lens material is a polymer olefin resin or an acrylic resin, the transmittance does not decrease even when the blue laser beam is irradiated for 1000 hours. Suitable as material. For example, the polymer olefin resin includes a cycloolefin polymer, and the acrylic resin includes a polymethyl methacrylate resin.

  Here, the reason for setting the blue laser light irradiation time to 1000 hours as the material determination of the resin lens is that the image display device 1 is used for business purposes, and has a device life of 5 years and a use day of 5 weeks per week. This is because the irradiation time of the blue laser light is about 1040 hours, assuming that the lighting duty of each color laser light is 20% because the time is 2 hours each in the morning and afternoon and the field sequential system. This condition is a rather severe evaluation time condition.

  (Table 1) is a table showing the optical power density of each lens in the optical system of the image display device 1 according to the first embodiment.

（表１）が示す通りに、青色光の光パワー密度が１８０ｍＷ／ｍｍ²以下であるレンズ群は投射光学部８、レンチキュラレンズ１６そしてフィールドレンズ１７である（（表１）で一点鎖線内に示される部分）。したがって、前述した検討結果によりこれらのレンズ群のレンズが樹脂化できる。

As shown in (Table 1), the lens group in which the optical power density of blue light is 180 mW / mm ² or less is the projection optical unit 8, the lenticular lens 16, and the field lens 17 ((Table 1) within the one-dot chain line). Part shown). Therefore, the lenses of these lens groups can be made resin based on the above-described examination results.

  Therefore, a configuration in which a part of the lens group of the optical system 60 and a part of the constituent lenses of the projection optical unit 8 are made of resin will be described in detail.

  The optical path of the laser beam passing through the lens group of the optical system 60 of the image display apparatus 1 will be described with reference to FIG. FIG. 5 is a schematic configuration diagram of a lens group in the optical system 60 of the image display apparatus 1 according to the present invention.

  As shown in FIG. 5, the laser light output from the blue laser light source device 4 passes through the collimator lens 13 and is input to the lenticular lens 16. At this time, the laser light is converted into parallel light.

  That is, the laser light output from the blue laser light source device 4 travels along the optical path represented by the thick solid line, solid line, and dotted line in FIG. When the laser light reaches and passes through the collimator lens 13, the laser light travels through the collimator lens 13 with a high light power density shown in (Table 1).

  Then, the optical power of the laser light is attenuated by traveling through the collimator lens 13, and the attenuated laser light is input to the lenticular lens 16. When the laser light reaches and passes through the lenticular lens 16, the laser light travels through the lenticular lens 16 at a low light power density shown in (Table 1).

Therefore, the collimator lens 13 through which the blue laser light travels with a high optical power density cannot be made into a resin as described above. On the other hand, the lenticular lens 16 in which the blue laser light travels at a reduced light power density can be resinized if the light power density value for resinization is satisfied (the light power density of blue light is 180 mW / mm ² or less). .

  Next, the blue laser light output from the lenticular lens 16 is diffused and input to the field lens 17. When the light reaches the field lens 17 and passes through, the light power density of the blue laser light becomes considerably low as shown in Table 1 because the light beam is diffused. Therefore, the field lens 17 can be made of resin as described above.

  The laser beam described above is described for blue light, but as described above for green light and red light, lenses that pass only green light and red light (that is, collimator lenses 11 and 12) are made of resin. it can.

  Next, the optical path of the laser beam passing through the constituent lenses in the projection optical unit 8 of the image display device 1 will be described with reference to FIG. FIG. 6 is a schematic configuration diagram of a lens group in the projection optical unit 8 of the image display apparatus 1 according to the present invention. FIG. 6A is a schematic configuration diagram when a lens group used for the projection optical unit 8 is made of glass, and FIG. 6B is a diagram illustrating a part of the lens group used for the projection optical unit 8 made of resin. It is a schematic block diagram in a case.

  As shown in FIG. 6A, the blue laser light output from the spatial light modulator 5 passes through the polarization beam splitter 6 and is input to the projection optical unit 8. At this time, the laser beam becomes a luminous flux having a spread.

  That is, the blue laser light output from the spatial light modulator 5 travels along an optical path represented by a solid line, a dotted line, and an alternate long and short dash line in FIG. When the laser light reaches the lens L 9 of the projection optical unit 8, the light beam of the laser light becomes almost maximum spread, and then converges toward the aperture stop 50. Thereafter, the light beam of the laser light that has passed through the aperture stop 50 is gradually expanded and emitted to the projection side.

  Therefore, the optical power density is small in a lens (for example, a lens surrounded by a square frame such as L1 and L9 in FIG. 6A) at a position away from the aperture stop 50 of the projection optical unit 8.

  On the other hand, in a lens close to the aperture stop 50 of the projection optical unit 8 (for example, a lens L4 or L5 in FIG. 6A), the laser beam converges and the optical power density increases.

  In particular, a laser beam having a short wavelength such as a blue emission wavelength has a larger optical energy than that of green or red even at the same optical power density, so that it is used for the optical system of the image display apparatus 1. The effect on the resin-made members (such as a decrease in transmittance) is increased.

  In the first embodiment, the lenses L1, L2, L3, L6, L7, L8, and L9 at the position where the optical power density of the blue laser light is small in FIG. 6A are changed from glass to resin. . That is, the lenses L1, L2 and L3 are provided with the function of resin, and the resin aspherical lens L10 is replaced in FIG. 6B.

  Similarly, the lenses L6, L7, L8, and L9 are provided with the functions of resin, and the resin aspherical lens L13 is used in FIG. 6B.

  At this time, it is apparent as shown in FIG. 6B that the replaced lenses L10 and L13 are also in a position where the optical power density of the laser light is small.

  Thus, the lens material having the low optical power density of the blue light passing through the lens used in the image display device 1 is made of a resin aspherical lens, so that the lens material is maintained while maintaining the lens characteristics of the optical system. The cost reduction can reduce the cost of the lens, making the lens molding easier and reducing the number of manufacturing steps. In addition, since the lens can be made aspherical by making the lens resin, the number of lenses can be reduced, so that the cost of the lens can be reduced and the cost of the image display device 1 can be reduced.

  Furthermore, the weight of the lens can be reduced by converting the lens into a resin or reducing the number of lens components, and the weight of the image display device 1 can be reduced.

  In addition, although the lens of the projection optical part 8 which is large and heavy among the lens groups of all the optical systems has been described, the lenses of other lens groups can be resinized similarly.

Further, the lens of the optical system 60 of the image display device 1 having a light power density of blue light higher than 180 mW / mm ² cannot satisfy the light resistance if it is made of resin. In order to maintain the quality, it is made of conventional glass.

  As described above, a lens having a low optical power density of light passing through the lens of the optical system used in the image display device 1 is a resin-made aspheric lens, while maintaining the lens characteristics of the optical system. The cost of the lens can be reduced by reducing the lens material cost, the lens can be easily molded, and the number of manufacturing steps can be reduced. Further, since the lens can be made aspherical by making the lens resin, the number of lenses can be reduced, so that the cost of the lens can be reduced and the cost of the image display device 1 can be reduced.

  Furthermore, the weight of the lens can be reduced by converting the lens into a resin or reducing the number of lens components, and the weight of the image display device 1 can be reduced.

  Further, since the resin of the resin lens is made of polymer olefin resin or acrylic resin, it is possible to prevent the light deterioration of the resin lens from being promoted even when the image display device 1 is downsized and the internal temperature of the device is likely to rise.

  In the first embodiment, the light source of the image display device 1 is described as a laser, but the light source may be a light emitting diode (LED). However, since lasers have the same phase of light, chromatic aberration is unlikely to occur in the lens, and there is an advantage that the design of the optical system becomes easy.

  The image display device according to the present invention has the effect of reducing the lens cost by reducing the cost of the lens by resinating the lens of the optical system, and reducing the weight of the lens by reducing the number of lens components. Useful for cost reduction and weight reduction.

DESCRIPTION OF SYMBOLS 1 Image display apparatus 2 Green laser light source apparatus 3 Red laser light source apparatus 4 Blue laser light source apparatus 5 Spatial light modulator 6 Polarizing beam splitter 8 Projection optical part 11, 12, 13 Collimator lens 14, 15 Dichroic mirror 16 Lenticular lens 17 Field lens 50 Aperture stop 60 Optical system

Claims (4)

A blue light source that emits blue light;
A green light source that emits green light;
A red light source that emits red light;
An optical system composed of a plurality of lens groups for guiding and projecting each color light output from each color light source to the outside, and
Among each lens belonging to the plurality of lens groups, a lens having a light power per unit area of the blue light passing through the lens of 180 mW / mm ² or less is resinized, and among the lenses belonging to the lens group An image display device, wherein a lens other than a resinized lens is made of glass. The resinized lens is one of the plurality of lens groups and is the most upstream lens and the most downstream lens in the light irradiation direction among the lenses of the projection optical unit that is located on the most downstream side of the optical path and irradiates light to the outside. The image display apparatus according to claim 1, wherein the image display apparatus is provided. The resinized lens is one of the plurality of lens groups and is located in the uppermost stream of the optical path, and is a collimator lens that converts the light output from each color light source into parallel light. The image display device according to claim 1, wherein the image display device is a lens having an optical power per unit area of 0 mW / mm ² . 4. The image display device according to claim 1, wherein the resinized lens is made of a polymer olefin resin or an acrylic resin.

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