JPH04121704A - Projection lens device and projection television device using the same - Google Patents

Abstract

PURPOSE:To realize the lens device which has a wide field angle by putting glass lenses in partial charge of the nearly entire positive refracting power of the whole lens device system and arranging plural plastic aspherical lenses which have positive weak refracting power nearby the optical axis. CONSTITUTION:A 1st group lens 1 and a 2nd group lens 2 which are plastic aspherical lenses are so shaped nearby the optical axis as to have weak positive refracting power and the influence of variation in their refracting power with temperature upon the refracting power of the whole lens system (almost all allotted to glass lenses 3a and 3b) is reduced. The 1st group lens 1 forms a concave lens at its peripheral part and the 2nd group lens 2 forms a convex lens; and the both are made nearly equal in local refracting power to reduce a focus drift corresponding to temperature variation. Thus, a decrease in focus performance with temperature when the diameter of the lens device is made large is canceled.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a projection lens device suitable for use in a projection television device, and particularly to a hybrid type projection lens device in which a glass lens and a plastic lens are mixed. It is something.

[Conventional technology]

In so-called projection television equipment, in which an original image on a cathode ray tube phosphor screen is projected onto a screen using a projection lens device, there has been significant progress in focusing performance in recent years, and demands are placed on the projection lens device, which is a key device. Performance is also improving year by year.

Under these circumstances, projection lens devices are made up of plastic lenses, which have a large degree of freedom in correcting aberrations by easily making the lens surface aspherical, can easily be made into large apertures, and are highly mass-producible. It is becoming mainstream as a lens for Initially, projection lens devices were mainly composed of only plastic lenses, but now the mainstream is hybrid systems that use a combination of glass lenses (spherical lenses) and aspherical plastic lenses.

The reason for this is that if a projection lens device is constructed with only plastic lenses, there will be a point where the refractive index and shape will change due to temperature fluctuations, causing the focal position to change and deteriorating the focusing performance (see below). , this decrease in focus performance is referred to as focus temperature drift)
.

Japanese Patent Laid-Open No. 63-264716 is cited as a document disclosing specific technical means for solving this problem. The conventional technology disclosed herein is a projection lens device with a five-group configuration; ■ Most of the positive refractive power of the entire lens system is borne by the third group lens, and by using this as a glass lens, focusing can be achieved. The temperature drift of is significantly reduced. ■
By using the first group lens as a positive lens and the second group lens as a negative lens, changes in the refractive power of the lens (caused by changes in refractive index) caused by temperature drift are offset.

As described above, the conventional projection lens device described in the above-mentioned document can be said to be an excellent projection lens device in which the temperature drift of the focus is reduced by optimal design of the lens configuration.

[Problem to be Solved by the Invention] In the lens configuration according to the above-mentioned prior art, in order to reduce spherical aberration, astigmatism, and coma that depend on the aperture, the second lens group consisting of a concave lens is replaced with the third lens group. It is placed close to the screen side of the lens. For this reason, the entrance pupil position of the entire lens system moves away from the center of the third group lens and toward the screen, which is the image point, and the conventional projection lens device described above achieves a wide angle of view (reduction in projection distance). If we try to realize this, it becomes extremely difficult to correct distortion and astigmatism.

Furthermore, if an attempt is made to increase the aperture and at the same time obtain a sufficient peripheral illuminance ratio, the outer diameters of the constituent lenses will increase, increasing production costs.

For the reasons described above, it has been extremely difficult to achieve a wide angle of view (short projection distance) using a conventional projection lens device.

Furthermore, the above-mentioned prior art does not disclose any deformation of the lens shape due to expansion and contraction of each lens due to temperature changes that occur even then, and a solution thereof, resulting in a lack of practicality.

Therefore, an object of the present invention is to be able to sufficiently reduce the drift of focus performance due to temperature and humidity, and to have a wide angle of view (
An object of the present invention is to provide a projection lens device that can shorten the projection distance, and furthermore to provide a projection television device using such a projection lens device.

[Means to solve the problem]

In order to achieve the above object, the present invention takes the following measures. In other words, in order to reduce the deterioration of focus performance due to changes in temperature and humidity in the paraxial system, most of the positive refractive power of the entire projection lens system is shared by a glass lens (hereinafter referred to as a glass power lens). . At this time, a concave lens is not placed near the glass power lens, but a plastic aspherical lens having a weak positive refractive power is placed near the optical axis.

Thereby, since the entrance pupil does not move away from the glass power lens toward the screen, a projection lens device with a wide angle of view can be realized.

On the other hand, aberrations that depend on the aperture are corrected by the aspherical shape of the portion away from the optical axis (the peripheral portion of the lens). Next, local changes in the refractive power of the lens surface due to temperature and humidity changes in the aspherical shape of the lens periphery are offset by a combination of a plurality of plastic aspherical lenses.

By the method described above, highly accurate temperature and humidity guarantees of focus performance can be realized.

In addition, in the mounted state, the lens shape is forcibly deformed so that the shape change due to temperature and humidity of the two types of plastic aspheric lenses does not occur freely, or even if it occurs, it is easy to cancel it out. The above object can be achieved by using a structured lens barrel and lens structure.

[Effect]

How the technical means for solving the problems of the present invention works will be explained using FIGS. 3, 4, and 5.

Figure 3 shows the temperature of the projection lens device invented by Wood,
FIG. 3 is a longitudinal cross-sectional view for explaining means for reducing focus drift due to humidity.

In the figure, l is the first group lens, 2 is the second group lens, and 3 is the second group lens.
is the third group lens (however, the third group lens 3 is a glass lens formed by laminating lenses 3a and 3b), 4 is the fourth group lens, 5 is the fifth group lens, and 6 is the cooling lens. 13 is a screen.

See Figure 3. Among the light rays from the center point A of the cathode ray tube phosphor screen P, the upper limit of the light rays effective for image formation (reaching the screen 13) is RAY 1, and the lower eye ray RAY2. Furthermore, among the light rays from the object point B in the peripheral area of the screen, the upper limit light of the light rays effective for image formation is RAY3', and the lower limit light RAY4.

For convenience of explanation, we will use a projection lens device consisting of 6 lenses, and 3a
, 3b is a hybrid system in which glass lenses are used and the others are plastic lenses.

First, a means for reducing focus drift with respect to the temperature at the center of the screen will be explained. The shapes of the first group lens 1 and the second group lens 2, which are plastic aspheric lenses, near the optical axis are both shaped to have weak positive refractive power. As a result,
The influence of changes in the refractive power of the two lenses due to temperature on the refractive power of the entire projection lens system (mostly shared by the glass lens) can be reduced.

Next, as shown in Figure 4, which is an enlarged view of section A in Figure 3,
The shape of the peripheral part of the lens is a concave lens shape in the first group lens 1 (the local refractive power of the lens is -r).

On the other hand, the second group lens 2 has a convex lens shape (the local refractive power of the lens is 94), and the local refractive powers of both lenses are made almost equal.

That is, ψ,″=, ψ4.

Next, a description will be given of means for reducing focus drift with respect to temperature in the peripheral area of the screen.

Returning to Figure 3, the inside of the image light from off-axis object point B.

As seen in FIG. 5, which is an enlarged view of section A in FIG. 3, the upper limit light RAY3 and the lower limit light RAY4 pass above the optical axis in the first group lens 1, which is a plastic aspherical lens.

The shape of this passage area is a concave lens shape approximately centered at the position through which the principal ray has passed. On the other hand, the shape of the light beam passing region of the second group lens 2 is a weak convex lens shape near the optical axis.

The local refractive power (-ψ,) of the concave lens in the region sandwiched between the chief ray and the upper limit light RAY3 of the first group lens 1 and the local refractive power ψ7 of the second group lens 20 are made approximately equal.

Similarly, the refractive power (-tP6) of the local concave lens in the region sandwiched between the chief ray and the lower limit light RAY4 of the first group lens 1 is approximately equal to the refractive power ψ8 of the local convex lens of the second group lens 2. do.

For convenience of explanation, we have described the meridional plane above, but it goes without saying that the sagittal plane has the same effect.

As described above, in order to reduce focus drift due to temperature changes, it is sufficient to design the local lens shapes of the first group lens 1 and the second group lens 2 so that their refractive powers are approximately equal.

Furthermore, in order to reduce the deterioration in focus performance caused by expansion and contraction of the lens caused by humidity changes, as described above, the refractive power of the local lens shapes of the first lens group 1 and the second lens group 2 should be adjusted. It is best to make them approximately equal so that they cancel each other out. Further, a means for restraining from the radial direction is provided in a portion other than the lens effective diameter of the first group lens 1 or the second group lens 2, or both, so that when the lens expands, it is forcibly deformed. It is even better to increase the canceling effect by strengthening the refractive power of the local lens.

〔Example〕

Examples of the present invention will be described below. Figures 1 and 2
Each of the figures is a sectional view showing a main part of a lens of a projection lens device as an embodiment of the present invention.

In these figures, P is a cathode ray tube phosphor screen, 7 is a cathode ray tube panel, 6 is a coolant, 5 is a fifth group lens, 4 is a fourth group lens, 3 is a third group lens, 2 is a second group lens,
1 is a first group lens.

The first lens group 1 to the fourth lens group 4 are assembled into an inner lens barrel 8, and are positioned and fixed to an outer lens barrel 9 with fixing screws 11. Furthermore, the outer lens barrel 9 is screwed and fixed to the bracket 10 via the demarcation plate 12.

The optical system of this example has a 5.4
The configuration is such that the best performance is obtained when an inch raster is enlarged and projected onto the screen. The magnification for enlarged projection is shown in Table 1 (A), (B) and Table 2 (A
) and (B) respectively, the optical system is 8.4 times larger, and Table 3 (A),
(B) to Table 5 In the optical system constructed from the lens data shown in (A) and (B), respectively, it is 9.3 times larger.

In addition, the angle of view of the lens is shown in Table 1 (AL (B) and Table 2
(AL In the optical system configured with the lens data shown in (B), 72 degrees, Table 3 (A) (B)
In the optical system configured with the lens data shown in Table 5 (A) and (B), it is 78 degrees,
It has a high angle of view, and even a single folding mirror can create a sufficiently compact cent.

The first group lens 1 has an aspherical shape based on the aperture (to eliminate spherical aberration). The second group lens 2 has an aspherical shape to eliminate astigmatism and coma aberration. The third group lens 3 is made of a glass lens and has as large a power as possible in order to reduce focus drift due to temperature changes.

The fourth group lens 4 has an aspherical shape and its power is made as small as possible in order to eliminate high-order coma aberration. The fifth lens group 5 is a lens for correcting field curvature, and has an aspherical air-side (screen-side) interface in order to correct off-axis sagittal aberration. Further, the cathode ray tube fluorescent screen P1 has a curvature to correct field curvature. In particular, if an aspheric surface is used to correct high-order field curvature, even more excellent correction becomes possible.

-C, the fluorescent screen P1 of the cathode ray tube panel 6 is manufactured by press molding, and no post-processing is performed. Therefore, the manufacturing method itself does not change whether the molded shape is spherical or aspherical.

On the other hand, the lenses of this lens system are designed to minimize the power of plastic lenses, making them thin and
By reducing the difference in wall thickness between the center and periphery, we aim to improve moldability.

In the embodiment of the present invention, as an optical system having the data shown in Table 6, the focal length of the entire projection lens system is shortened to about 80 mm, and chromatic aberration is reduced. Further, as shown in FIG. 1, the third lens group 3 is a bonded lens of two lenses 3a and 3b (in the example, Table 1
(A), corresponding to Table 2 (A) 1 Table 4 (A)). lens 3b
is a concave lens made of a high-dispersion material, and lens 3a is a convex lens made of a low-dispersion material, and by bonding the two together, chromatic aberration is reduced.

Specific lens data that can be taken by the projection lens device according to the present invention described above is shown in Tables 1 to 5, so please refer to them.

Next, how to read this lens data will be explained based on Table 1. Table 1 shows the spherical system (Table 1 (A)) that mainly deals with the lens region near the optical axis and the aspheric system (Table 1 (A)) that deals with the lens area around the optical axis.
The data are shown separately in Table 1 (B). First, the screen has a radius of curvature of ■ (i.e., is a flat surface), the distance on the optical axis from the screen to the surface S1 of the first group lens 1 (interface distance) is 786.09 mm, and the refractive index of the medium (air) between the screen and the surface S1 of the first lens group 1 is 786.09 mm. is shown to be 1.0.

The radius of curvature of the S1 surface of the first lens group 1 is 97.89.
8 mm (the center of curvature is on the phosphor screen side), the distance between lens surfaces S1 and 82 on the optical axis (surface distance) is 8.874 mm, and the refractive index of the medium between them is 1.49334. ing. Similarly, the final result shows that the radius of curvature of the phosphor screen P1 of the cathode ray tube panel 7 is 341.28 mm, the thickness of the cathode ray tube panel 7 on the optical axis is 13.4 mm, and the refractive index is 1.56232.

Next, Table 1(B) shows the surface 51S2 of the first group lens 1, the surface S3 of the second group lens 2. S, and the surface S of the fourth lens group 4
, , S, the 50th lens surface SIG of the fifth group, and the phosphor surface P, the aspherical coefficients are shown.

Here, the aspheric coefficient is a coefficient when the surface shape is expressed by the following equation.

+AE-r'ten AF-rb+AC-rll+AH-r'
.

...... (1) However, as shown in Figures 7 and 8, which are diagrams explaining the definition of the lens shape, Z is defined by taking the optical axis direction as the Z axis and the radial direction of the lens as the r axis. represents the height of the lens surface (a function of r) when

Therefore, if the CC, AE, AF, AC, and AH coefficients are given, the height, or shape, of the lens surface is determined according to the above formula.

Figure 8 is an explanatory diagram of an aspherical surface. By substituting the respective values into the terms of the aspherical surface above, the lens surface of only a spherical system can be changed to SS (
r) A Lens surface shifted by 5° is obtained.

Further, in Table 1(B), the surface S of the fifth group lens 5 has all aspherical coefficients of zero, indicating that it is a spherical surface.

The above is how to read the data shown in Part 1 (A) and (B). Tables 2 to 5 show specific examples of lens data of other examples, and are read in the same way.

Fig. 1 is a side sectional view of the projection lens device corresponding to the lens data in Table 1 (A) and (B), and Fig. 2 is a side sectional view corresponding to the lens data in Table 4 (A) and (B). FIG. 3 is a side sectional view of the projection lens device.

Next, using the projection lens device according to the present invention described above, the MTF (Modulation
FIGS. 9 to 13 show the evaluation results of the focus characteristics by N Transfer Function. The phosphor emission spectrum shown in FIG. 6 was used at this time.

Here, Fig. 9 is a characteristic diagram corresponding to Table 1 (A) and (B), Fig. 10 is a characteristic diagram corresponding to Table 2 (A) and (B), and Fig. 11 is a characteristic diagram corresponding to Table 3 (A). , (B), the 12th
Figures are shown in Tables 4 (A) and (B), and Figure 13 is shown in Table 5 (
A).

(B) is a characteristic diagram corresponding to each.

In addition, 300TV is used as a white and black striped signal on the screen.
This shows what happens when you take a book.

It can be seen that good MTF characteristics are shown from FIG. 9 to FIG. 13. For the examples configured with the lens data shown in Tables 1 to 5, the focal length of the entire lens system is fO
1 1st group lens 1. 2nd group lens 2. Each focal length of the third group lens 3 is fl.

When f2 f3, the relationship shown in Table 6 holds true. That is, 0.14<fo/fl<0.24 0.02<fO/I2<0.25 0.63<fo/f3<0.83. In this embodiment, temperature drift in focus is reduced by sharing most of the positive refractive power of the entire lens system with the third lens group, which is a glass lens.

Next, the shape of the lens surface will be explained. 1st group lens 1
screen side lens surface S1, second group side lens surface SZ,
The following can be said about the aspherical shapes of the first group side lens surface ss of the second group lens 2 and the third group side lens surface S4 of the second group lens 2. This will be explained below using FIG.

As already mentioned, FIG. 8 is an explanatory diagram showing the shape of an aspherical lens. The height of the lens surface when the optical axis direction is taken as the Z axis and taken in the radial direction of the lens is the spherical system, that is, Rn
33(r) + CC, AE, AF, AC
, AH is substituted into the above equation (1) as A. , then by substituting the clap radius for r, the above A3(
r+ and S. .

As shown in Table 8, the ratio of -0.08<As/Ss<0.05 holds true, and similarly, the second group side lens surface S of the first group lens 1
2, the following relationship holds true: 0.20<As/ss<0.52.

On the first group side lens surface S3 of the second group lens 2, as shown in Table 9, the relationship 1,26<As/Ss<0.06 holds true. Similarly, on the third group side lens surface S4 of the second group lens 2, 0.07 < As / S s
The relationship < 1.16 holds true.

The surface spacing between the first group lens 1 and the second group lens 2 is 12
3, the ratio of I23 and the focal length fO of the entire projection lens system is 0, 15< (I23/f
O) The relationship of <0.25 holds true. In order to maintain the force performance and secure the peripheral illumination ratio, it is necessary to satisfy 0.15<(I23/fo). On the other hand, as this ratio increases, the amount of light in the middle area of the screen decreases, so preferably (I23/fo) <0.25.

Also, the plane distance between the first group lens 1 and the second group lens 2 is 1.
23 and the surface spacing 145 between the second group lens 2 and the third group lens 3, as shown in Table 7, 23.0<(1
23/I45) <40.0 holds true.

In order to suppress the sag amount of the first group side lens surface S of the second group lens 2 and ensure the edge thickness of the lens, it is desirable that (123/I45) < 40. .

It is necessary to do so.

On the other hand, if the brightness at the center of the screen is ensured and the above value is reduced, it is necessary to increase the effective diameter of the second group lens 2. For this reason, it is preferable to set 23,0 < (123/I45).

Next, regarding the shape of the phosphor screen, as shown in Tables 1 to 5, it is aspherical, and the center of curvature is on the screen side, and the radius of curvature increases from the center to the periphery. It is the shape.

The projection lens device according to the present invention has a projection distance of 787.6 mm for 45-inch projection and 790.0 mm for 50-inch projection, which is sufficiently short and requires only one folding mirror, so that the set can be made more compact. .

The characteristics of the projection lens device according to the embodiment of the present invention have been described above based on the lens data constituting the projection lens device. Next, the effects of this embodiment will be specifically described.

FIGS. 14 and 15 show a projection lens device (Table 1 (A)) as an embodiment of the present invention shown in FIG. 1.

First group lens 1 in (Lens data listed in (B))
alone, second group lens 2 alone, first group lens 1 and second group lens 2 simultaneously expanded by 0.1% and 0.1%
It is a characteristic diagram showing changes in MTF characteristics of 300 TV lines when the lens shape is changed by shrinking.

In both figures, the average meridional and sagittal MTFs are calculated and plotted at each image height. Condition 1 in both figures indicates the case where only the first group lens 1 is used alone, and Condition 2 indicates the case where only the second group lens 2 is used alone. Furthermore, condition 3 indicates a case where the first group lens 1 and the second group lens 2 are simultaneously expanded or contracted.

From both figures, it can be seen that in this example, the deterioration in focus performance caused by changes in the lens surface shape caused by expansion or contraction is offset by changes in the shapes of the first group lens 1 and the second group lens 2. .

Next, FIGS. 16 and 17 are characteristic diagrams showing changes in the MTF characteristics of 300TV with respect to changes in the refractive index of the lens caused by temperature changes in the same example as the above-mentioned example. In the figure, the average meridional and sagittal MTFs are calculated and plotted at each image height.

FIG. 16 is a characteristic diagram when the lens temperature is 40°C. Further, FIG. 17 is a characteristic diagram for a case where the lens temperature is 65°C.

Condition 1 in both figures indicates the case where only the first group lens 1 is used alone, and Condition 2 indicates the case where only the second group lens 2 is used alone. Furthermore, condition 3 shows a case where the refractive indexes of the first group lens I and the second group lens 2 are changed at the same time.

In both figures, the deterioration in focus performance is greatest under condition 2, that is, when the refractive index of only the second group lens 2 is changed independently. In addition, in the same way as the focus reduction due to expansion and contraction of the lens described above, in the case of condition 3, that is, when the refractive index changes of the first group lens 1 and the second group lens 2 occur simultaneously, the focus performance may be reduced. It turns out that they cancel each other out.

As described above, in the projection lens device of this embodiment, the deterioration of focus performance due to temperature and humidity can be offset by the lens surface shapes of at least two plastic aspherical lenses in the constituent lenses.

Next, in a projection lens device, a concrete method for restraining a plastic lens and forcibly deforming the lens shape due to changes in temperature and humidity is shown in FIGS. 18 and 19.
This will be explained using figures.

FIG. 18 is a perspective view showing an example of such restraint means. In the figure, 14 is a ring, 15 is a plastic lens, and 19 is an edge portion.

In FIG. 18, a ring 14 made of a material more rigid than plastic is attached to the edge part 19 (the flat outer edge part supported by the lens barrel) of the plastic lens 15 other than the effective diameter.
Insert. Alternatively, the ring 14 may be insert molded. At this time, if the relationship between the outer diameter of the plastic lens 15 in a dry state and the inner diameter L° of the ring 14 is L''<(1,001×L), a practical restraining force can be obtained and the desired deformation can be achieved. amount can be achieved.

When the above-described restraining means was applied to the first group lens 1 and the second group lens 2 of the embodiment shown in FIG. 1, the first group lens 1 was moved toward the screen side due to expansion due to moisture absorption.
It was confirmed that the second group lens 2 was deformed toward the cathode ray tube, and the local lens effects described above were strengthened to the same extent.

In this embodiment, the screen-side lens surface shape of the first group lens 1 is convex toward the screen at the center and becomes concave toward the periphery, and the shape of the second group lens 2 is weak at the center. We have described the combination of two plastic aspherical lenses in the case of positive refractive power and a shape where the positive refractive power is stronger at the periphery, but even if the shapes of the lenses are different or the direction of deformation is opposite, However, the same effect may be obtained by using similar restraint means.

Moreover, FIG. 19 is a perspective view showing another example of the restraint means.

In the figure, 16 is a lens barrel, and 17 is a ring.

In FIG. 19, a part is shown as a broken surface to make the structure easier to understand. That is, the plastic lens 1 of the lens barrel 16
A ring 17 made of a material having higher rigidity than plastic is fitted and fixed in the part that receives the edge part 19 of the ring 5. Alternatively, a similar lens barrel may be obtained by insert molding the ring 17.

At this time, the relationship between the outer diameter of the plastic lens 15 in a dry state and the inner diameter L1 of the ring 17 is L'<(1,001×
L), a practical restraining force can be obtained and a desired amount of deformation can be achieved.

On the other hand, depending on the shape of the plastic lens, it may be possible to obtain a better offsetting effect by allowing the plastic lens to expand without restraint, rather than forcibly deforming it when it expands due to the restraints described above. . below,
Specific means for making it unrestricted will be explained using FIG. 20 and FIG. 21.

FIG. 20 is a perspective view showing an example of means by which the plastic lens itself becomes unrestricted when the lens expands.

In the figure, 1st is an elastic body, and 20 is a notch.

In FIG. 20, an edge portion 19 is provided at a portion other than the effective diameter of the plastic lens 15, and a portion thereof is cut out to provide a notch portion 20 for fixing the elastic body 18. The elastic body 18 is stuffed into this notch 20 and fixed. Alternatively, a similar lens may be obtained by insert molding the elastic body 18.

With the configuration described above, the plastic lens 15
Even if the plastic lens 15 expands, the elastic body 18 only deforms, and the plastic lens 15 is not restrained by the lens barrel 16. At this time, the relationship between the outer diameter of the plastic lens 15 in a dry state and the distance (R'/2) from the outermost part of the elastic body 18 in the radial direction to the center of the lens is expressed as R'> (1,001×L) By doing so, the desired effect can be obtained. In this embodiment, there are three notches, but the same effect can be obtained even if there are more than three notches.

The second group lens 2 of the embodiment shown in FIG.
In this case, the local lens effect could be most effectively offset when the first group lens 1 was provided with the above-mentioned restraining means.

As described above, it goes without saying that it is effective to use both a constrained plastic lens and an unconstrained plastic lens in the same projection lens device, as described above.

FIG. 21 is a perspective view showing another example of means for forming an invalid bundle. In the figure, 21 is a fixing hole.

In FIG. 21, a part is shown as a broken surface so that the structure can be easily understood. Three or more fixing holes 21 are provided in a portion of the lens barrel 16 that receives the plastic lens 15 from the radial direction, and the elastic body 18 is pushed into the fixing holes 21 and fixed. The elastic body 18 is provided with a bend, so that once it is inserted once, it cannot be removed. Further, when the elastic body 18 is attached to a lens barrel, a portion thereof protrudes from the inner wall surface of the lens barrel, and the tip of this protruding portion allows the plastic lens 1
5 is supported and fixed.

With the configuration described above, even if the plastic lens 15 expands, the elastic body 18 only deforms, and the plastic lens 15 is not restrained by the lens barrel 16. At this time, when the diameter of the inscribed circle connecting the outer diameter of the plastic lens 15 in a dry state and the apex of the protrusion of the elastic body 18 protruding from the lens barrel 16 is D> (1,001 xL), the desired effect can be obtained.

In this embodiment, an elastic body fixing hole 21 is provided in the lens barrel 16.
are provided at three locations, and the plastic lens 15 is held and fixed by elastic bodies from three directions, but the same effect can be obtained from three or more directions.

Table 1 (A) Table 1 (B) Table 2 (A) Table 2 (B) Table 3 (A) Table 3 (B) Table 4 (A) Table 4 (B) Table 5 (A) Table 5 (B) Table rl: Focal length of the 1st group lens f3: Focal length of the 3rd group lens [5: Focal length of the 5th group lens r2: Focal length of the 2nd group lens f4F Focal length of the 4th group lens Table ■23: Surface distance I45 between first group lens 1 and second group lens 2: Surface distance table between second group lens 2 and third group lens 3 [Effects of the Invention] According to the present invention, projection Due to the shape of at least two plastic aspherical lenses in the projection lens device, even if the projection lens device has a large aperture, it is possible to offset the decrease in focus performance due to temperature and humidity.

Furthermore, there are other effects: (1) There is no concave lens placed on the screen side of the lens with positive refractive power in the entire projection lens system, making it possible to correct distortion and astigmatism even when the angle of view is widened. It can achieve both high focus and wide angle of view.

(2) As mentioned above, since the concave lens is not arranged,
Light rays from the periphery of the screen do not diverge. Therefore, the height of the light beam can be reduced. For this reason, a good peripheral light amount ratio can be achieved.

In addition, in order to reduce the deterioration of focus performance due to temperature and humidity changes, means for restraining the movement of the lens from the radial direction is provided in a portion other than the effective diameter (edge portion) of the plastic aspherical lens, so as to prevent deterioration in focus performance due to temperature and humidity changes. The local shape of the lens is forcibly deformed by the expansion caused by the lens, and the above-mentioned canceling effect can be further enhanced.

Furthermore, depending on the shape of the lens, a holding means that does not have a binding force may be required, and the above-mentioned holding can be realized by the plastic lens and lens barrel of the present invention.

[Brief explanation of the drawing]

1 and 2 are cross-sectional views showing a projection lens device as an embodiment of the present invention, and FIGS. 3 to 5 are lenses for explaining the operating principle of the projection lens device according to the present invention. A schematic diagram, FIG. 6 is an emission spectrum characteristic diagram of a clamping light body, FIGS. 7 and 8 are explanatory diagrams used to explain the definition of lens shape, and FIGS. 9 to 13 are examples of the present invention, respectively. MTF characteristic diagram of the projection lens device shown as 14th
15 is a characteristic diagram showing MTF characteristics with respect to changes in lens shape of a projection lens device as an embodiment of the present invention, and FIGS. 16 and 17 are characteristic diagrams of a projection lens as an embodiment of the present invention. A characteristic diagram showing MTF characteristics with respect to changes in the refractive index of the lens caused by changes in the temperature of the device; FIGS. 18 and 19 are perspective views showing an example of lens restraint means, respectively;
Figure 20. FIG. 21 is a perspective view showing an example of lens non-constraint means. Explanation of symbols 1... 1st group lens, 2... 2nd group lens, 3...
・3rd group lens, 4... 4th group lens, 5... 5th group lens
Group lens, Pl... fluorescent screen, 6... coolant, 7...
・Cathode ray tube panel, 8...Inner tube, 9...Outer tube, 10...Bracket, 11...Fixing screw, 12.
... Fixed plate, 13... Screen, 14... Ring, 15... Plastic lens, 16... Lens barrel, 1
7...Ring, 18...Elastic body, 19...Lens edge portion, 20...Edge notch portion Representative Patent Attorney Akio Namiki No. 6-7 Fig. Z (Optical axis) Fig. 8 Z (optical axis) Fig. 9 ItlO Fig. Relative angle of view Fig. 11 Fig. 12 Fig. 13 Comparative penalty σ angle of view 14 ■ Relative seed crystal Fig. 16 Chopsticks 17 Fig. Saimeju・1i! 〉High School Figure 18 Figure 19 Figure 20 Figure 21 Procedural Amendment Statement October 23, 1990

Claims (1)

[Claims] 1. A projection lens device including at least two plastic lenses for enlarging and projecting an original image projected on a display screen onto the screen, wherein one of the two plastic lenses is , consists of a lens (1) whose center is convex toward the screen and becomes concave toward the periphery;
The lens (2) has a shape in which the center part has a weak positive refractive power toward the screen side, and the positive refractive power becomes stronger as it goes toward the periphery compared to the central part. A projection device characterized in that a lens has a concave shape at its periphery and a shape having positive refractive power at the periphery of the other lens cancels out fluctuations in lens power caused by changes in the surrounding environment. lens device. 2. The projection lens device according to claim 1, wherein the one lens is located closer to the screen than the other lens. 3. In the projection lens device according to claim 1, the other lens (2) has a shape in which the center portion thereof has a weak positive refractive power toward the screen side, and the positive refractive power increases toward the peripheral portion. The lens has a shape where its refractive power is stronger than that at the center, and the lens surface on the screen side (S3)
A projection lens device characterized in that the lens satisfies the following relationship: |Rs|>|Rb|, where the radius of curvature of the display screen side lens surface (S4) is Rb. 4. In the projection lens device according to claim 1 or 2, the one lens (1) is made of plastic having a shape that is convex at the center toward the screen and becomes concave toward the periphery. A projection lens device characterized in that it is a lens and is a lens located closest to a screen among the lenses constituting the lens device. 5. In the projection lens device according to claim 3, one lens group (3a,
3b) is arranged on the display screen side of the other lens (2). 6. In a projection lens device for enlarging and projecting the original image projected on the display screen onto the screen, from the screen side to the display screen side, the center part has a convex shape toward the screen side and goes to the peripheral part. First group lens (1) including a plastic lens having a concave surface according to
The plastic lens has a shape in which the center part has a weak positive refractive power toward the screen side, and the positive refractive power becomes stronger toward the periphery compared to the central part. a second group lens (2), a third group lens (3a, 3b) including lenses that share most of the positive refractive power of the entire system of the lens device consisting of a plurality of lens groups, and a relatively weak refractive power. Fourth group lens (4) including a lens with
and a fifth group lens (5) including a negative lens having a concave surface on the screen side. 7. The projection lens device according to claim 6, wherein the projection lens device satisfies the following relationship. 0.14<f0/f1<0.24 0.02<f0/f2<0.25 0.63<f0/f3<0.83 However, f0: The value of the entire lens system including the phosphor screen which is the display screen. Focal length f1: Focal length of the first group lens f2: Focal length of the second group lens f3: Focal length of the third group lens 8. In the projection lens device according to claim 7, the first group lens, the 2nd group lens, 4th group lens, and 5th group lens
A projection lens device characterized in that either one of the group lenses is an aspherical surface. 9. The projection lens device according to claim 7 or 8, wherein a plastic lens (1
), when the aspherical amount of the screen-side lens surface is As/Ss (where As is the aspherical sag amount and Ss is the spherical sag amount), -0.1<
A projection lens device characterized in that the following relationship holds true: (As/Ss). 10. The projection lens device according to claim 7 or 8, wherein a plastic lens (
When the aspherical amount of the display screen side lens surface in 1) is As/Ss (where As is the aspherical sag amount and Ss is the spherical sag amount), -1.3<
A projection lens device characterized in that the following relationship holds true: (As/Ss). 11. The projection lens device according to claim 7 or 8, wherein the plastic lens (
When the aspherical amount of the screen-side lens surface in 2) is As/Ss (where As is the aspherical sag amount and Ss is the spherical sag amount), -1.3
A projection lens device characterized in that the following relationship holds true: <(As/Ss). 12. The projection lens device according to claim 7 or 8, wherein the plastic lens (
When the aspherical amount of the display screen side lens surface in 2) is As/Ss (where As is the aspherical sag amount and Ss is the spherical sag amount), -0.15
A projection lens device characterized in that the following relationship holds true: <(As/Ss). 13. In the projection lens device according to claim 7, the distance between the first group lens (1) and the second group lens (2) is I23, and the entire surface including the fluorescent screen which is the display screen is A projection lens device characterized in that, when the focal length of the lens system is f0, the following relationship holds true: 0.15<(I23/f0). 14. The projection lens device according to claim 7 or 8, wherein the surface distance between the first group lens (1) and the second group lens (2) is I23, and the second group lens (2) and the third group lens (3a, 3b) is I45, and the ratio (I23/I45) of the two holds true as follows: 20<(I23/I45) lens device. 15. In the projection lens device according to claim 6, 7 or 8, the fifth group lens (5) includes a negative lens having a concave surface on the screen side and a display screen having a convex surface on the opposite side from the screen. A projection lens device comprising: a fluorescent screen glass (7); 16. The projection lens device according to claim 15,
A projection lens device characterized in that the shape of the fluorescent screen glass (7) constituting the fifth group lens has a center of curvature on the screen side, and a radius of curvature is larger in the peripheral part than in the central part. 17. A projection lens device for enlarging and projecting the original image projected on the display screen onto the screen, in which the center part is convex toward the screen side and the peripheral part is convex from the screen side to the display screen side. The first group lens (1) includes a plastic lens with a surface that becomes concave toward the center, and the center part has a weak positive refractive power toward the screen, and the positive refractive power increases toward the periphery. The second lens group includes a plastic lens having a surface whose refractive power is stronger than that of the central part (
2), a third group lens (3a, 3b) including lenses that share most of the positive refractive power of the entire system consisting of a plurality of group lenses constituting the lens device, and a third group lens (3a, 3b) that has a relatively weak refractive power. A projection lens device comprising: a fourth group lens (4) including a lens with a concave surface; and a fifth group lens (5) including a negative lens having a concave surface on the screen side and a cathode ray tube phosphor screen constituting the display screen. A projection television device characterized by using. 18. The projection television apparatus according to claim 17, wherein the cathode ray tube phosphor screen is formed of a glass surface having a convex shape on the side opposite to the screen. 19. The projection television device according to claim 18, wherein the shape of the cathode ray tube fluorescent screen glass has a center of curvature on the screen side, and a radius of curvature is larger in the peripheral part than in the central part. television equipment. 20. In a projection lens device for enlarging and projecting an original image projected on the screen of an image display device onto the screen, at least two of the plurality of lenses constituting the projection lens device are plastic lenses; The first plastic lens among the two plastic lenses consists of a lens (1) having a convex shape at the center and a concave shape toward the periphery, and the second plastic lens among the two plastic lenses The lens has a shape in which the center has a weak positive refractive power, and as it goes to the periphery, the positive refractive power becomes stronger than that in the center, and in the direction of transmission of light rays. By combining the locally convex or concave lens shapes of the first and second plastic lenses, changes in refractive index caused by changes in ambient temperature and humidity, and changes in refractive power caused by changes in lens shape. A projection lens device characterized by canceling out. 21. In a projection lens device for enlarging and projecting the original image projected on the screen of an image display device onto the screen, at least two of the plurality of lenses constituting the projection lens device are plastic lenses; The first plastic lens among the two plastic lenses is an aspherical lens that has a convex shape at the center and becomes concave toward the periphery, and the second plastic lens among the two plastic lenses , an aspherical lens having a shape in which the center part has a weak positive refractive power and the positive refractive power becomes stronger toward the periphery compared to the central part, and the first and second plastic A restraining means for restraining one or both of the aspherical lenses in the radial direction at a portion other than the effective diameter of the lens (
14, 17). 22. A projection lens device for enlarging and projecting the original image projected on the display screen onto the screen, in which the center part is convex toward the screen side and the peripheral part is convex from the screen side to the display screen side. The first group lens includes an aspherical plastic lens with a surface that becomes concave toward the center, and the center has a weak positive refractive power toward the screen, and the positive refractive power increases toward the periphery. The entire system of the projection lens device is composed of a second group lens including an aspherical plastic lens having a surface whose refractive power is stronger than that of the central portion, and a plurality of lens groups constituting the lens device. A third group lens includes a lens that shares most of the refractive power, a fourth group lens includes a lens with relatively weak refractive power, and a fifth group lens includes a negative lens having a concave surface on the screen side. The projection lens device is characterized by comprising a restraining means for restraining one or both of the two aspherical plastic lenses in the radial direction at a portion other than the effective diameter of the lens. Projection lens device. 23. The projection lens device according to claim 22,
The aspherical plastic lens constituting the first group lens has a surface that is convex at the center toward the screen and becomes concave toward the periphery. A projection lens device comprising a restraint means for restraining in a direction. 24. The projection lens device according to claim 22,
The second group lens has a shape in which the center part has a weak positive refractive power toward the screen side, and the surface has a shape in which the positive refractive power becomes stronger toward the periphery compared to the central part. A projection lens device comprising a restraining means for restraining a constituting aspherical plastic lens in a radial direction at a portion other than the effective diameter of the lens. 25. The projection lens device according to claim 22,
The aspherical plastic lens constituting the first group lens has a surface whose center part is convex toward the screen and becomes concave toward the periphery; Both of the aspherical plastic lenses constituting the second lens group have surfaces shaped to have a weak positive refractive power, and the positive refractive power becomes stronger toward the periphery than in the center. A projection lens device comprising a restraining means for restraining a lens in a radial direction at a portion other than the effective diameter of the lens. 26. The projection lens device according to claim 21,
The restraining means has an inner diameter L' having the following relationship with respect to the outer diameter of the aspherical plastic lens in a dry state as L, and is made of a material having higher rigidity than plastic, A projection lens device comprising a ring fitted into the outer shape of the aspherical plastic lens at a portion other than the lens effective diameter. L′<(1.001×L) 27. In the projection lens device according to claim 21,
The restraining means has an inner diameter L' having the following relationship with respect to the outer diameter of the aspherical plastic lens in a dry state as L, and is made of a material having higher rigidity than plastic, A projection lens device comprising a ring that is screwed, fitted, or insert-molded in advance into a portion of a lens barrel that holds and fixes the aspherical plastic lens. L′<(1.001×L) 28. In the projection lens device according to claim 21,
The restraining means has an inner diameter L' having the following relationship with respect to the outer diameter of the aspherical plastic lens in a dry state, and is formed of a material having higher rigidity than plastic. A projection lens device comprising the lens barrel in which a ring is screwed, fitted, or insert-molded in advance into a portion of the lens barrel that holds and fixes the aspherical plastic lens. L'<(1.001×L) 29. In a projection lens device for enlarging and projecting an original image projected on the screen of an image display device onto the screen, a plurality of lenses constituting the projection lens device At least two of the plastic lenses are made of plastic lenses, and the first plastic lens of the two plastic lenses is an aspherical lens that has a convex shape at the center and becomes concave toward the periphery; The second lens in the plastic lens is an aspherical lens in which the center part has a weak positive refractive power, and the positive refractive power becomes stronger toward the periphery compared to the central part. In one or both of the first and second plastic aspherical lenses, a flat outer edge portion supported by the lens barrel is formed as an edge portion (19) on the outside of the lens effective surface; A notch (20) is provided in the edge portion, the notch is filled with an elastic body that absorbs the expansion of the lens through elastic deformation, or insert molding is performed, and the diameter of the lens in a dry state is L, and the When the distance in the radial direction from the center of the lens to the outermost part of the packed or insert-molded elastic body is R', the relationship is 2R'>(1.001×L). A projection lens device characterized by: 30. In a projection lens device for enlarging and projecting an original image projected on the screen of an image display device onto the screen, at least two of the plurality of lenses constituting the projection lens device are plastic lenses; The first plastic lens among the two plastic lenses is an aspherical lens that has a convex shape at the center and becomes concave toward the periphery, and the second plastic lens among the two plastic lenses , an aspherical lens having a shape in which the center part has a weak positive refractive power and the positive refractive power becomes stronger toward the periphery compared to the central part, and the first and second plastic As a lens barrel for one or both of the aspherical lenses, at least three fixing holes are bored in the outer wall surface of the lens barrel for holding and fixing the plastic aspherical lens, and elastic holes are formed from the outside of the holes inward. The plastic aspherical lens is supported and fixed from the radial direction by protruding the body, and the diameter of the inscribed circle connecting the vertices of the protrusion of the elastic body is D, and the diameter of the plastic aspherical lens in a dry state is A projection lens device characterized in that it uses a lens barrel having the relationship D>(1.001×L), where L is D>(1.001×L).