JP2015014677A - Projection lens and projection display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a projection lens the various aberrations of which is well corrected and which is also compact.SOLUTION: The projection lens comprises a first lens group G1 having negative refractive power and a second lens group G2 having positive refractive power which are arranged in order from an enlarging side, where distance between the first lens group G1 and the second lens group G2 is set to be the largest in the entire system, and the first lens group G1 includes a first lens L11 having negative refractive power and a second lens L12 having negative refractive power arranged in order from the most enlarging side. The projection lens further satisfies conditional expressions (1), (2) as follows; 3.0<f2/f1<50.0...(1), 0.80<D2/D4<7.00...(2), where f1 denotes a focal length of the first lens, f2 denotes a focal length of the second lens L12, D2 denotes a distance between the first lens L11 and the second lens L12, and D4 denotes a distance between the second lens L12 and a lens L13 placed next thereto on the reduction side.

Description

  The present invention relates to a projection display device, and more particularly to a projection display device equipped with a light valve such as a liquid crystal display element.

  The present invention also relates to a projection lens suitably used in the above projection display device.

  In recent years, projection display devices using light valves such as liquid crystal display elements and DMD display elements are becoming widespread. In particular, three light valves are used to correspond to the three primary colors of RGB illumination light, and the light modulated by the individual light valves is combined by a prism or the like, and an image is displayed on a screen via a projection lens. Is widely used in practice.

  In such a projection lens mounted on a projection display device that synthesizes and projects each modulated light from the three light valves by a color synthesis optical system, as described above, a prism that performs color synthesis, etc. Usually, a large back focus is required to arrange the lens and to avoid thermal problems.

  In addition, since the spectral characteristics change depending on the angle of incident light in a color synthesis optical system, this type of projection lens must have a characteristic that the entrance pupil as viewed from the reduction side is located far away, that is, telecentricity. It becomes.

  Also, this type of projection lens requires aberration correction commensurate with the resolution of the light valve. Furthermore, in order to meet the demand for projection from a distance close to a large screen, a wider angle of view is required. On the other hand, there are strong demands for cost reduction of projection lenses.

  Conventionally, those described in Patent Documents 1 to 3 are known as projection lenses capable of satisfying the above requirements to some extent.

JP 2008-309991 A JP 2010-085732 A JP 2011-133656 A

  However, although the projection lens described in Patent Document 1 has a wide field angle of about 110 °, a lens system is large because a mirror for bending an optical path is assumed in the lens. Yes.

  The projection lens described in Patent Document 2 has a wide field angle of about 120 °, but an excessive number of lenses are used for widening the field angle. It has not been able to meet the demand for decline.

  Further, the projection lens described in Patent Document 3 has a wide field angle of about 120 °, but a large curvature of field occurs at the outermost periphery of the lens, and it cannot be denied that aberration correction is insufficient.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a projection lens and a projection display device that can correct various aberrations with a wide angle of view.

The projection lens of the present invention is
In order from the enlargement side, a first lens group having a negative refractive power and a second lens group having a positive refractive power are arranged in order, and the projection lens is substantially formed.
The distance between the first lens group and the second lens group is set to the maximum lens distance in the entire system,
The first lens group includes a first lens having a negative refractive power and a second lens having a negative refractive power, which are arranged in order from the most magnified side,
The first lens group is substantially composed of four or five lenses,
And the following conditional expressions (1) and (2)
3.0 <f2 / f1 <50.0 (1)
0.80 <D2 / D4 <7.00 (2)
F1: Focal length of the first lens f2: Focal length of the second lens D2: Distance between the first lens and the second lens D4: On the reduction side next to the second lens and the second lens It is characterized in that the distance from the arranged lens is satisfied.

  In addition, the above “substantially” and “substantially constituted” means, in addition to the listed components, lenses other than lenses that have substantially no power, lenses such as an aperture, a cover glass, and a filter. It shows that an optical element, a lens flange, a lens barrel, a mechanism portion such as a camera shake correction mechanism, and the like may be included (hereinafter the same).

The projection lens of the present invention having the above configuration has the following conditional expression (1 ′)
4.0 <f2 / f1 <45.0 (1 ′)
It is desirable to satisfy

In that case, the projection lens of the present invention has the following conditional expression (1 ″)
6.0 <f2 / f1 <40.0 (1 ")
It is further desirable to satisfy

Further, the projection lens of the present invention has the following conditional expression (2 ′)
0.90 <D2 / D4 <5.50 (2 ')
It is desirable to satisfy

The projection lens of the present invention has the following conditional expression (3):
110 ° <2ω (3)
However, 2ω: It is desirable to satisfy the entire angle of view on the enlargement side.

The projection lens of the present invention has the following conditional expression (4):
−5.0 <F1 / f <−1.0 (4)
However, f: Focal length of the entire system F1: It is desirable that the focal length of the first lens group is satisfied.

In that case, the projection lens of the present invention has the following conditional expression (4 ′):
−3.5 <F1 / f <−1.4 (4 ′)
It is further desirable to satisfy

Further, the projection lens of the present invention has the following conditional expression (5):
2.5 <F2 / f <10.0 (5)
However, f: Focal length of the entire system F2: It is desirable that the focal length of the second lens group is satisfied.

In that case, the projection lens of the present invention has the following conditional expression (5 ′):
4.0 <F2 / f <8.0 (5 ′)
It is further desirable to satisfy

The projection lens of the present invention has the following conditional expression (6):
3.0 <Bf / f (6)
Where f: focal length of the entire system Bf: back focus of the entire system (air equivalent length)
It is desirable to satisfy

  Further, in the projection lens of the present invention, the first lens group in order from the magnifying side is a first lens having negative refracting power, a second lens having negative refracting power, and a meniscus lens having a convex surface facing the magnifying side. A third lens having a negative refractive power, a fourth lens having a positive refractive power, and a fifth lens having a negative refractive power are arranged and substantially configured, and It is desirable that five lenses are joined to form a lens portion having negative refractive power as a whole. In that case, it is desirable that the third lens and the lens unit having a negative refractive power are configured to be focused by moving in the optical axis direction independently of each other.

  Alternatively, in the projection lens of the present invention, the first lens group in order from the magnification side is a first lens having a negative refractive power, a second lens having a negative refractive power, and a meniscus lens having a convex surface facing the magnification side. In this case, a third lens having a negative refractive power and a fourth lens having a negative refractive power may be arranged and substantially constituted. In that case, it is desirable that the third lens and the fourth lens are configured to be focused by moving in the optical axis direction independently of each other.

  On the other hand, a projection display device of the present invention includes a light source, a light valve, an illumination optical system that guides a light beam from the light source to the light valve, and the projection lens according to the present invention described above. It has a configuration in which it is modulated and projected onto a screen by a projection lens.

  The projection lens according to the present invention is configured to satisfy the conditional expressions (1) and (2) described above, so that it is possible to satisfactorily correct field curvature and distortion that are likely to occur in a wide-angle lens. In addition, miniaturization can be achieved. The reason will be described below.

  Conditional expression (1) defines the ratio of the focal length of the second lens to the focal length of the first lens of the first lens group. When this ratio is equal to or greater than the upper limit of conditional expression (1), The power of the first lens with respect to the lens becomes too strong, or the power of the second lens with respect to the first lens becomes too weak, making it difficult to correct curvature of field and distortion. ), The power of the first lens, which is the most magnified lens, becomes too weak. Therefore, it is inevitable to increase the lens diameter in order to obtain a predetermined angle of view, resulting in high costs. In addition to being connected, it leads to an increase in the total number of lenses due to insufficient aberration correction by the first lens and the second lens.

  Conditional expression (2) defines the ratio between the distance between the first lens and the second lens and the distance between the second lens and the next lens, and when this ratio is equal to or greater than the upper limit of conditional expression (2). This leads to an increase in the size of the entire lens system. On the other hand, when the ratio is less than or equal to the lower limit value of conditional expression (2), a large field curvature occurs at the outermost periphery of the lens.

  On the other hand, as long as the power balance and the positional relationship between the first lens and the second lens are appropriately maintained so as to satisfy the conditional expressions (1) and (2), the above-described problems are not caused. Further, it is possible to satisfactorily correct the field curvature and distortion that are likely to occur in a wide-angle lens, and to reduce the lens size.

  Further, since the projection display device of the present invention is applied with the projection lens according to the present invention as described above, various aberrations are favorably corrected while realizing a wide angle of view and miniaturization. High-quality images can be projected.

Sectional drawing which shows the lens structure of the projection lens which concerns on Example 1 of this invention. Sectional drawing which shows the lens structure of the projection lens which concerns on Example 2 of this invention. Sectional drawing which shows the lens structure of the projection lens which concerns on Example 3 of this invention. Sectional drawing which shows the lens structure of the projection lens which concerns on Example 4 of this invention. Each aberration diagram of the projection lens according to Example 1 of the present invention Each aberration diagram of the projection lens according to Example 2 of the present invention Each aberration diagram of the projection lens according to Example 3 of the present invention Each aberration diagram of the projection lens according to Example 4 of the present invention 1 is a schematic configuration diagram of a projection display device according to an embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. 1 to 4 are cross-sectional views showing examples of the configuration of a projection lens according to an embodiment of the present invention. The configuration examples shown in FIGS. 1 to 4 correspond to the projection lenses of Examples 1 to 4, which will be described later. These projection lenses project image information displayed at the reduction-side conjugate position to the enlargement-side conjugate position. A schematic configuration of a projection display device according to an embodiment of the present invention using such a projection lens is shown in FIG. 9, which will be described later.

  First, a projection lens according to an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a cross-sectional view showing a lens configuration of a projection lens according to Example 1 of the present invention. This figure shows the lens arrangement when the projection distance, that is, the distance between the most magnified lens surface and the magnification conjugate position is 122.717. Here, the projection distance is shown as a value when the focal length of the entire system is 1.00, and setting the projection distance to 122.717 naturally means focusing at that distance. (The same applies hereinafter). Hereinafter, an embodiment of the present invention will be described using the configuration example shown in FIG. 1 as a representative example.

  The projection lens of this embodiment can be mounted on a projection display device used for school education, corporate training, presentation, etc. as an example. For example, image information displayed on a light valve is projected onto a screen. It can be used as a projection lens. In FIG. 1, assuming that the left side of the drawing is an enlargement side and the right side is a reduction side and is mounted on a projection display device, the image display surface 1 of the light valve and the one end surface 2 a are in close contact with the image display surface 1. The glass block 2 (including the filter portion) and the virtual diaphragm 3 arranged so as to be displayed are displayed together.

  In the projection display device, a light beam provided with image information on the image display surface 1 is incident on the projection lens via the glass block 2, and the enlargement side conjugate position in the left direction of the paper surface by the projection lens. And is enlarged and projected on a screen (not shown).

  In FIG. 1, only the image display surface 1 of one light valve is shown. However, in the projection display device, the light beam from the light source is separated into three primary color lights by a color separation optical system. For example, there are three light valves that can display a full-color image (see FIG. 9). In that case, the three primary color lights can be synthesized by arranging color synthesizing means such as a cross dichroic prism at the position of the glass block 2.

  The projection lens according to the present embodiment is substantially configured by sequentially arranging a first lens group G1 having a negative refractive power and a second lens group G2 having a positive refractive power in order from the magnification side. . In the example shown in FIG. 1, the first lens group G1 includes five lenses of a first lens L11, a second lens L12, a third lens L13, a fourth lens L14, and a fifth lens L15 in order from the substantially enlarged side. It is arranged. The fourth lens L14 and the fifth lens L15 are cemented with each other to form a lens unit having negative refractive power.

  On the other hand, in the second lens group G2, the first lens L21, the second lens L22, the third lens L23, the fourth lens L24, the fifth lens L25, the sixth lens L26, the seventh lens L27, In addition, eight lenses of the eighth lens L28 are arranged. The second lens L22 and the third lens L23 are cemented with each other, and the sixth lens L26 and the seventh lens L27 are also cemented with each other.

  In the first lens group G1, the first lens L11 is an aspherical lens having negative refractive power, in which the magnification-side and reduction-side lens surfaces are aspherical and the concave surface is directed to the magnification side in the paraxial region, The second lens L12 is an aspherical lens having negative refractive power in which the lens surfaces on the magnifying side and the reducing side are each aspherical and the convex surface is directed to the magnifying side in the paraxial region, and the third lens L13 is the magnifying side. A meniscus lens having a negative refractive power with a convex surface facing the lens, the fourth lens L14 is a biconvex lens, and the fifth lens L15 is a biconcave lens.

  On the other hand, in the second lens group G2, the first lens L21 is a biconvex lens, the second lens L22 is a biconcave lens, the third lens L23 is a meniscus lens having positive refractive power, the fourth lens L24 is a biconvex lens, and a fifth lens L25. Is an aspherical lens in which the lens surfaces on the enlargement side and the reduction side are each aspherical, with the concave surface facing the enlargement side in the paraxial region, the sixth lens L26 is a biconcave lens, the seventh lens L27 is a biconvex lens, The eight lens L28 is a biconvex lens.

  However, the number and types of lenses constituting each lens group of the projection lens of the present invention are not limited to the example of FIG. 1 described above.

  In the projection lens of the present embodiment, the first lens group G1 is substantially composed of five lenses L11 to L15 as described above. The first lens L11 arranged on the most enlargement side in the first lens group G1 and the second lens L12 arranged next on the reduction side both have negative refractive power. .

  In the projection lens of this embodiment, the distance between the first lens group G1 and the second lens group G2, that is, the fifth lens L15 of the first lens group G1 and the first lens L21 of the second lens group G2. The interval (air interval) is set to the maximum lens interval in the entire system, as will be described in detail later.

  In the projection lens of the present embodiment, as described above, the first lens group G1 includes, in order from the magnification side, the aspherical first lens L11 having negative refractive power and the second aspherical lens having negative refractive power. A lens L12, a meniscus lens having a convex surface on the enlargement side and having a negative refractive power, and a lens portion having a negative refractive power (consisting of a fourth lens L14 and a fifth lens L15 joined to each other). ) Is arranged and substantially configured, the following effects are obtained.

  That is, the arrangement of the two aspheric lenses L11 and L12 on the most enlarged side is advantageous for widening the angle and realizing a small F number. In addition, the third lens L13, which is a meniscus lens having a negative refractive power disposed next to the reduction side, can bend the light beam to suppress the occurrence of coma and field curvature, and then the reduction side. The chromatic aberration of magnification can be corrected by the lens unit having negative refractive power arranged in the lens. Since the lens unit having negative refractive power is configured by joining the fourth lens L14 having positive refractive power and the fifth lens L15 having negative refractive power, further correction of lateral chromatic aberration is achieved. It will be advantageous.

  The above describes the effect of the configuration of the first lens group G1 of the present embodiment in accordance with Example 1, but in Examples 2 to 4 described later, instead of the lens unit having the negative refractive power, Since the fourth lens L14 having negative refracting power is provided, the same effects as described above can be obtained in the second to fourth embodiments. However, in Examples 2-4, the effect by having used the said lens part as the cemented lens is not acquired.

  In the projection lens of the present embodiment, focusing is performed by moving a part of the lenses of the first lens group G1 along the optical axis Z. More specifically, the first lens L11 and the second lens L12 of the first lens group G1 are fixed, and the third lens L13 is moved along the optical axis Z so that the distance between them is changed. Independent of the third lens L13, a lens unit having negative refractive power disposed on the reduction side (consisting of a fourth lens L14 and a fifth lens L15 joined together) is moved along the optical axis Z. By doing so, focusing is performed. The change in the surface interval due to the movement of the lenses L13 to L15 will be described in detail later with reference to Table 2.

  The projection lens of the present embodiment has the following effects due to the above-described configuration for focusing. That is, it is generally difficult to maintain optical performance when focusing on a wide-angle lens, but the third lens L13 and the lens unit move independently from each other as in the present embodiment. If a so-called floating structure is applied, it is possible to satisfactorily correct aberration fluctuations (particularly field curvature) associated with focusing. In addition, since the first lens L11 and the second lens L12, which are large-diameter lenses, are not included in the focusing lens group, the focusing mechanism can be simplified, thereby reducing the cost. Can be achieved.

  The above describes the effect of the configuration for focusing of the present embodiment in accordance with Example 1, but in Examples 2 to 4 described later, instead of the lens unit having the negative refractive power, a negative value is used. Since the fourth lens L14 having the refractive power is arranged, the same effects as described above can be obtained in the second to fourth embodiments.

In the projection lens of this embodiment, the conditional expressions (1) and (2) described above are used.
3.0 <f2 / f1 <50.0 (1)
0.80 <D2 / D4 <7.00 (2)
F1: Focal length of the first lens group first lens L11 f2: Focal length of the first lens group second lens L12 D2: Distance between the first lens L11 and second lens L12 D4: Second lens L12 and third lens The distance from the lens L13 is satisfied.

  It should be noted that these conditional expressions (1) and (2) and the other conditional expressions (3) to (6) described above define the conditions (that is, the character expressions) values for Examples 1 to 4. These are collectively shown in Table 17.

  When the conditional expressions (1) and (2) are satisfied, the projection lens of this embodiment can satisfactorily correct the field curvature and distortion that are likely to occur with a wide-angle lens as described above. In addition, there is an effect that downsizing can be realized. The detailed reason is as described above.

As shown in Table 17, specifically, in Example 1, the value of f2 / f1 is 7.93. Therefore, in the first embodiment, the following conditional expression (1 ′) is further expressed by conditional expression (1 ″)
4.0 <f2 / f1 <45.0 (1 ′)
6.0 <f2 / f1 <40.0 (1 ")
Is also satisfied. Further, as shown in Table 17, specifically, in Example 1, the value of D2 / D4 is 1.15. Therefore, in Example 1, the following conditional expression (2 ′)
0.90 <D2 / D4 <5.50 (2 ')
Is also satisfied. Therefore, in the projection lens of Example 1, the above effect becomes more remarkable.

  From Table 17, the conditional expression (1) and further conditional expressions (1 ′) and (1 ″) described above are satisfied, and that conditional expression (2) and further conditional expression (2 ′) are satisfied. Obviously, Examples 2 to 4 to be described later are the same, and therefore, the effects as described above can be obtained also in Examples 2 to 4.

In the projection lens of this embodiment, the conditional expression (3) described above is used.
110 ° <2ω (3)
However, 2ω: All angles of view on the enlargement side are also satisfied. As a result, the projection lens of the present embodiment can meet the demand for a wide angle of view.

  The condition (3) described above is satisfied as is clear from Table 17 in the second to fourth embodiments described later. Therefore, in the second to fourth embodiments, as described above. The effect is obtained.

In the projection lens of the present embodiment, the conditional expression (4) described above is used.
−5.0 <F1 / f <−1.0 (4)
However, f: Focal length of the entire system F1: The focal length of the first lens group G1 is also satisfied. Thereby, the projection lens of the present embodiment can satisfactorily correct various aberrations such as lateral chromatic aberration, spherical aberration, and coma. The reason will be described below.

  Conditional expression (4) defines the ratio of the focal length F1 of the first lens group G1 to the focal length f of the entire system. When this ratio is larger than the upper limit value of the conditional expression (4), The power of the first lens group G1 becomes too large, and it becomes difficult to correct various aberrations such as spherical aberration and coma. On the other hand, when the ratio is small enough to be equal to or lower than the lower limit value of the conditional expression (4), the power of the first lens group G1 becomes too small, and it becomes difficult to correct lateral chromatic aberration. On the other hand, if the ratio exceeds the lower limit value of conditional expression (4) and is lower than the upper limit value, various aberrations such as lateral chromatic aberration, spherical aberration, and coma aberration can be achieved without causing the above-described problems. It can be corrected satisfactorily.

In the present embodiment, the following conditional expression (4 ′)
−3.5 <F1 / f <−1.4 (4 ′)
Therefore, the above effect becomes more remarkable.

  Conditional expression (4) and further conditional expression (4 ′) described above are satisfied in the same way in Examples 2 to 4 described later, as is apparent from Table 17, and accordingly, in Example 2 The effects as described above can be obtained also in .about.4.

In the projection lens of this embodiment, the conditional expression (5) described above is used.
2.5 <F2 / f <10.0 (5)
However, f: Focal length of the entire system F2: The focal length of the second lens group G2 is also satisfied. As a result, the projection lens of the present embodiment can ensure a sufficient back focus, and can satisfactorily correct various aberrations such as spherical aberration and coma. The reason will be described below.

  Conditional expression (5) defines the ratio of the focal length F2 of the second lens group G2 to the focal length f of the entire system. When this ratio is larger than the upper limit value of the conditional expression (5), Since the power of the second lens group G2 becomes too small, it is difficult to satisfactorily correct various aberrations such as spherical aberration and coma. On the contrary, when the ratio is small enough to be equal to or lower than the lower limit value of the conditional expression (5), the power of the second lens group G2 becomes too large, and the back focus cannot be sufficiently secured. If the ratio is above the lower limit value of conditional expression (5) and below the upper limit value, sufficient back focus can be secured without incurring the above problems, and spherical aberration, coma aberration, etc. Various aberrations can be corrected satisfactorily.

In the present embodiment, the following conditional expression (5 ′)
4.0 <F2 / f <8.0 (5 ′)
Therefore, the above effect becomes more remarkable.

  Conditional expression (5) and further conditional expression (5 ′) described above are satisfied in the same way in Examples 2 to 4 described later, as is clear from Table 17. The effects as described above can be obtained also in .about.4.

In the projection lens of this embodiment, the conditional expression (6) described above is used.
3.0 <Bf / f (6)
Where f: focal length of the entire system Bf: back focus of the entire system (air equivalent length)
Is also satisfied. As a result, the projection lens of this embodiment can secure a sufficient back focus and can easily arrange a color synthesis prism or the like. The reason will be described below.

  Conditional expression (6) defines the ratio of the back focus Bf to the focal length f of the entire projection lens system. If this ratio is small enough to be less than or equal to the lower limit value of the conditional expression (6), the back focus Bf. Becomes shorter, and it becomes difficult to dispose a color synthesis prism or the like. If the above ratio exceeds the lower limit value of conditional expression (6), it is necessary and sufficient to secure a space for arranging a color composition prism or the like on the reduction side of the projection lens without incurring the above-mentioned problems. A correct back focus Bf is set.

  The condition (6) described above is satisfied, as is clear from Table 17, the same applies to Examples 2 to 4 described later. Therefore, also in Examples 2 to 4 as described above, The effect is obtained.

  In the projection lens of the present invention, as in the example shown in FIG. 1, an aspherical lens can be applied to some lenses, and in that case, aberration correction can be performed better. Of course, the present invention is not limited to this, and the projection lens of the present invention can be configured by using only a lens having a spherical lens surface. In such a case, it is advantageous in reducing the cost.

  Next, an embodiment of the projection display device of the present invention will be described with reference to FIG. FIG. 9 schematically shows a configuration of a projection display apparatus according to an embodiment of the present invention. The projection display apparatus 100 includes a projection lens 10 according to an embodiment of the present invention, a light source 20, transmissive display elements 11 a to 11 c as light valves corresponding to each color light, and light beams from the light source 20. And an illumination optical system 30 leading to the bulb. The illumination optical system 30 includes dichroic mirrors 12 and 13 for color separation, a cross dichroic prism 14 for color synthesis, condenser lenses 16a to 16c, and mirrors 18a to 18c. In FIG. 9, the projection lens 10 is schematically shown. Further, an integrator such as a fly eye is disposed between the light source 20 and the dichroic mirror 12, but the illustration thereof is omitted in FIG.

  White light from the light source 20 is separated into three colored light beams (G light, B light, R light) by the dichroic mirrors 12 and 13 in the illumination optical system 30, and then the optical path is deflected by the mirrors 18a to 18c, respectively. Then, the light passes through the condenser lenses 16a to 16c and is incident on the transmissive display elements 11a to 11c corresponding to the light beams of the respective colors to be light-modulated. After color synthesis by the cross dichroic prism 14, the light enters the projection lens 10. The projection lens 10 projects an optical image by light modulated by the transmissive display elements 11a to 11c on a screen (not shown).

  As the transmissive display elements 11a to 11c, for example, transmissive liquid crystal display elements can be used. Although FIG. 9 shows an example in which a transmissive display element is used as the light valve, the light valve provided in the projection display device of the present invention is not limited to this, and a reflective liquid crystal display element, DMD, or the like. Other light modulation means may be used.

  Since the projection display device 100 of the present embodiment is applied to the projection display device 100 of the present embodiment, a high image quality in which various aberrations are well corrected while realizing a wide angle of view and miniaturization. The image can be projected.

  Next, specific examples of the projection lens of the present invention will be described.

<Example 1>
FIG. 1 shows the lens configuration of the projection lens of Example 1. The way of displaying the lens configuration and the like in FIG. 1 is as described above, and this is the same in FIGS. In addition, since the arrangement of the lens groups and the configuration of each lens group in the projection lens of Example 1 are also as described above, redundant description is omitted here.

  Table 1 shows basic lens data of the projection lens of Example 1. In Table 1, in the column of Si, the surface on the enlargement side of the component on the most enlargement side is the first, and the component number is assigned to the i-th (i = 1, 2, 3, ...). The Ri column indicates the radius of curvature of the i-th surface, and the Di column indicates the surface spacing on the optical axis Z between the i-th surface and the i + 1-th surface. Further, in the column of Ndj, the d-line (wavelength 587.6 nm) of the j-th (j = 1, 2, 3,. The νdj column indicates the Abbe number of the j-th component with respect to the d-line. In Table 1, the surfaces of the virtual diaphragm 3 and the glass block 2 shown in FIG. 1 are also shown. The surface with surface number 10 is the surface of the virtual diaphragm 3, and the surfaces with surface numbers 25 and 26 are the surface on the enlargement side and the surface on the reduction side of the glass block 2, respectively.

  In Table 1, the sign of the radius of curvature is positive when the surface shape is convex on the enlargement side and negative when the surface shape is convex on the reduction side. In Table 1, the surface number of an aspherical surface is indicated by an asterisk (*), and the paraxial radius of curvature is described in the column of the radius of curvature of the aspherical surface.

  In the projection lens of Example 1, as described above, the third lens L13 of the first lens group G1 is moved along the optical axis Z and is joined to each other independently. Focusing is performed by moving the fourth lens L14 and the fifth lens L15 along the optical axis Z. Therefore, the surface interval (surface interval between the second lens L12 and the third lens L13) related to the surface number 4 shown in Table 1, the surface interval related to the surface number 6 (interval between the third lens L13 and the fourth lens L14), and the surface The surface interval for No. 9 (the interval between the fifth lens L15 and the virtual diaphragm 3) changes with the focusing operation. In Table 1, the values for the three surface intervals are shown when the projection distance is 122.717.

  Table 2 shows projections of the surface numbers 4, 6 and 9 whose surface intervals change as the third lens L13, the fourth lens L14, and the fifth lens L15 of the first lens group G1 move as described above. The distance between the surfaces when the distance is 122.717, 92.038, and 178.86 are collectively shown.

  In Table 1 and Tables 5, 9 and 13, which will be described later, the surface numbers are determined on the assumption that the virtual diaphragm 3 (see FIG. 1) is located on the enlargement side with respect to the second lens group G2. However, in Example 1, the actual virtual diaphragm 3 is positioned on the reduction side with respect to the enlargement side lens surface of the first lens L21 of the second lens group G2, so in Table 1 from the virtual diaphragm 3 to the first lens L21. , That is, the surface interval of the surface number 10 is indicated with a symbol “−” (the same applies to Tables 5 and 9). Therefore, the distance between the first lens group G1 and the second lens group G2, that is, the distance (air distance) between the fifth lens L15 of the first lens group G1 and the first lens L21 is 5.5816-0.1649. = 5.4167, which is the maximum lens interval in the entire system. This is the same when the projection distance is set to a value other than 122.717, as is apparent from Tables 1 and 2.

  Next, Table 3 shows specifications for the d-line of the projection lens of Example 1, specifically, focal length f, back focus Bf, F number Fno. , The value of the total angle of view 2ω (unit is degree).

  In Tables 1 to 3, the value related to the length is a value normalized with the focal length of the entire system as 1.00. In Tables 1 to 3, numerical values rounded by predetermined digits as appropriate are described.

Table 4 shows the surface number and aspheric coefficient of each aspheric surface in Example 1. The aspheric coefficient shown here is a value of each coefficient K (eccentricity) and Ai in the aspheric expression represented by the following (Equation 1). Here, i is an integer of 3 or more, and in Example 1, all aspherical surfaces have values up to 16. However, the value i takes is not limited to this, and varies depending on each aspheric surface. Further, the numerical value “E−n” (n: integer) of the aspheric coefficient means “× 10 ⁻ⁿ ”.

  On the other hand, FIGS. 5A to 5D show aberration diagrams of the spherical aberration, astigmatism, distortion (distortion aberration), and lateral chromatic aberration (chromatic aberration of magnification) of the projection lens of Example 1, respectively. . The aberrations shown here are for the case where the projection distance is 122.717 described above.

  The aberration diagrams in FIGS. 5A to 5D are based on the d-line, but in the spherical aberration diagram, the F-line (wavelength wavelength 486.1 nm) and the C-line (wavelength 656.3 nm). ) Also shows aberrations, and the lateral chromatic aberration diagram shows aberrations related to the F-line and C-line. Further, in the astigmatism diagram, aberrations in the sagittal direction and the tangential direction are indicated by a solid line labeled (S) and a broken line labeled (T), respectively. Fno. Described above the vertical axis of the spherical aberration diagram. Is the F number, and ω described above the vertical axis of the other aberration diagrams is the half angle of view.

  The symbols, meanings, and description methods of the lens configuration diagram, table, and aberration diagram of Example 1 described above are basically the same as those of Examples 2 to 4 below unless otherwise specified. Further, the values related to the length of the lens data are standardized with the focal length of the entire system as 1.00, which is the same in the description of Examples 2 to 4 below.

<Example 2>
FIG. 2 shows the lens configuration of the projection lens of Example 2. The lens arrangement shown here is that when the projection distance is set to 122.977. Regarding the second embodiment and the third and fourth embodiments to be described later, the description of the configuration common to the first embodiment is omitted unless particularly necessary.

  The projection lens of Example 2 shown in FIG. 2 is substantially configured by arranging a first lens group G1 having a negative refractive power and a second lens group G2 having a positive refractive power in order from the magnification side. Has been. The first lens group G1 includes four lenses, that is, a first lens L11, a second lens L12, a third lens L13, and a fourth lens L14, which are arranged in order from the magnification side. The second lens group G2 includes a first lens L21, a second lens L22, a third lens L23, a fourth lens L24, a fifth lens L25, a sixth lens L26, a seventh lens L27, Eight lenses of the eighth lens L28 are arranged. The second lens L22 and the third lens L23 are cemented with each other, and the sixth lens L26 and the seventh lens L27 are also cemented with each other.

  As described above, the projection lens of Example 2 is basically different from the projection lens of Example 1 in that the number of lenses in the first lens group G1 is four. In the projection lens of Example 2, focusing is performed by moving the third lens L13 and the fourth lens L14 of the first lens group G1 along the optical axis Z independently of each other. The above points are the same in the third and fourth embodiments described later.

  In the first lens group G1, the first lens L11 is an aspherical lens having negative refractive power, in which the magnification-side and reduction-side lens surfaces are aspherical and the concave surface is directed to the magnification side in the paraxial region, The second lens L12 is an aspherical lens having negative refractive power in which the magnification-side and reduction-side lens surfaces are each aspherical and the convex surface is directed to the magnification side in the paraxial region, and the third lens L13 is negative. The meniscus lens having a refractive power and the fourth lens L14 are biconcave lenses.

  On the other hand, in the second lens group G2, the first lens L21 is a biconvex lens, the second lens L22 is a biconcave lens, the third lens L23 is a meniscus lens having positive refractive power, the fourth lens L24 is a biconvex lens, and a fifth lens L25. Is an aspherical lens in which the lens surfaces on the enlargement side and the reduction side are each aspherical, with the concave surface facing the enlargement side in the paraxial region, the sixth lens L26 is a biconcave lens, the seventh lens L27 is a biconvex lens, The eight lens L28 is a biconvex lens.

  Table 5 shows basic lens data of the projection lens of Example 2, Table 6 shows the distance between the variable surfaces of the lens moving with the focusing operation, Table 7 shows the specifications for the d-line, and the aspheric coefficient. Is shown in Table 8. The surface intervals shown in Table 6 are those when the projection distances are set to 122.977, 92.233, and 183.363. In addition, the surface distance of the basic lens data shown in Table 5 is for the case where the projection distance is 122.977.

From the data shown in Table 5, the interval (air interval) between the first lens group G1 and the second lens group G2 is 5.2237−0.1548 = 5.0689, which is the largest in the entire system. It is the lens interval. As is clear from Tables 5 and 6, this point is the same when the projection distance is set to a value other than 122.977.

  6A to 6D show aberration diagrams of the projection lens of Example 2. FIG. Each aberration shown here is for a projection distance of 122.977.

<Example 3>
FIG. 3 shows the lens configuration of the projection lens of Example 3. The lens arrangement shown here is for a projection distance of 122.803.

  The projection lens of Example 3 shown in FIG. 3 includes a first lens group G1 having a negative refracting power and a second lens group G2 having a positive refracting power arranged in order from the magnification side. Has been. The first lens group G1 includes four lenses, that is, a first lens L11, a second lens L12, a third lens L13, and a fourth lens L14, which are arranged in order from the magnification side. The second lens group G2 includes a first lens L21, a second lens L22, a third lens L23, a fourth lens L24, a fifth lens L25, a sixth lens L26, a seventh lens L27, Eight lenses of the eighth lens L28 are arranged. The second lens L22 and the third lens L23 are cemented with each other, and the sixth lens L26 and the seventh lens L27 are also cemented with each other.

  In the first lens group G1, the first lens L11 is an aspherical lens having negative refractive power, in which the magnification-side and reduction-side lens surfaces are aspherical and the concave surface is directed to the magnification side in the paraxial region, The second lens L12 is an aspherical lens having negative refractive power in which the magnification-side and reduction-side lens surfaces are each aspherical and the convex surface is directed to the magnification side in the paraxial region, and the third lens L13 is negative. The meniscus lens having refractive power and the fourth lens L14 are meniscus lenses having negative refractive power.

  On the other hand, in the second lens group G2, the first lens L21 is a biconvex lens, the second lens L22 is a biconcave lens, the third lens L23 is a meniscus lens having positive refractive power, the fourth lens L24 is a biconvex lens, and a fifth lens L25. Is an aspherical lens in which the lens surfaces on the enlargement side and the reduction side are each aspherical, with the concave surface facing the enlargement side in the paraxial region, the sixth lens L26 is a biconcave lens, the seventh lens L27 is a biconvex lens, The eight lens L28 is a biconvex lens.

  The basic lens data of the projection lens of Example 3 is shown in Table 9, the variable surface interval of the lens that moves with the focusing operation is shown in Table 10, the specifications for the d-line are shown in Table 11, and the aspheric coefficient Is shown in Table 12. The surface intervals shown in Table 10 are those when the projection distance is 122.803, 92.102, 183.103. Further, the surface interval of the basic lens data shown in Table 9 is for the case where the projection distance is 122.803.

From the data shown in Table 9, the distance (air distance) between the first lens group G1 and the second lens group G2 is 5.2465−0.0428 = 5.2037, which is the largest in the entire system. It is the lens interval. This is the same when the projection distance is set to a value other than 122.803, as is apparent from Tables 9 and 10.

  FIGS. 7A to 6D show aberration diagrams of the projection lens of Example 3. FIG. Each aberration shown here is for a projection distance of 122.803.

<Example 4>
FIG. 4 shows the lens configuration of the projection lens of Example 4. The lens arrangement shown here is for a projection distance of 121.895.

  The projection lens of Example 4 shown in FIG. 4 is substantially composed of a first lens group G1 having a negative refractive power and a second lens group G2 having a positive refractive power arranged in order from the magnification side. Has been. The first lens group G1 includes four lenses, that is, a first lens L11, a second lens L12, a third lens L13, and a fourth lens L14, which are arranged in order from the magnification side. The second lens group G2 includes a first lens L21, a second lens L22, a third lens L23, a fourth lens L24, a fifth lens L25, a sixth lens L26, and a seventh lens L27 in order from the substantially enlarged side. Seven lenses are arranged. The second lens L21 and the third lens L22 are cemented with each other, and the fifth lens L25 and the sixth lens L26 are also cemented with each other.

  As described above, the projection lens of Example 4 is compared with the projection lens of Example 1 in addition to the fact that the number of lenses in the first lens group G1 is four as described above, and in addition, the second lens group G2. This is basically different in that the number of lenses is seven.

  In the first lens group G1, the first lens L11 is an aspherical lens having negative refractive power, in which the magnification-side and reduction-side lens surfaces are aspherical and the concave surface is directed to the magnification side in the paraxial region, The second lens L12 is an aspherical lens having negative refractive power in which the magnification-side and reduction-side lens surfaces are each aspherical and the convex surface is directed to the magnification side in the paraxial region, and the third lens L13 is negative. The meniscus lens having refractive power and the fourth lens L14 are meniscus lenses having negative refractive power.

  On the other hand, in the second lens group G2, the first lens L21 is a biconvex lens, the second lens L22 is a biconcave lens, and the third lens L23 has an aspherical surface on the enlargement side and a reduction side. The aspherical lens with the concave surface facing the enlargement side, the fourth lens L24 is a biconvex lens, the fifth lens L25 is a biconcave lens, the sixth lens L26 is a biconvex lens, and the seventh lens L27 is a biconvex lens.

  Table 13 shows basic lens data of the projection lens of Example 4, Table 14 shows variable surface distances relating to the lens that moves with the focusing operation, Table 15 shows specifications for the d-line, and aspheric coefficient Is shown in Table 16. The surface intervals shown in Table 14 are those when the projection distance is set to 121.895, 91.421, and 181.749. Further, the surface intervals of the basic lens data shown in Table 13 are those when the projection distance is 121.895.

From the data shown in Table 13, the distance (air distance) between the first lens group G1 and the second lens group G2 is 5.5477 + 0.3070 = 5.8547, which is the maximum lens distance in the entire system. It has become. This is the same when the projection distance is set to a value other than 121.895, as is apparent from Tables 13 and 14.

  FIGS. 8A to 8D show aberration diagrams of the projection lens of Example 4. FIGS. Each aberration shown here is for a projection distance of 121.895.

Table 17 below summarizes the conditions defined by the conditional expressions (1) to (6) described above (that is, the character expression part) and the values of the conditions related thereto for Examples 1 to 4, respectively. Show.

  As can be seen from the above data, the projection lenses of Examples 1 to 4 have a wide full angle of view of 119.8 ° to 123.2 °, a small F-number of 1.80, and various aberrations. It is well corrected and has high optical performance.

  The present invention has been described with reference to the embodiments and examples. However, the projection lens of the present invention is not limited to the above examples, and various modifications can be made. For example, the curvature of each lens can be changed. The radius, surface spacing, refractive index, and Abbe number can be changed as appropriate.

  Further, the projection display apparatus of the present invention is not limited to the one having the above configuration, and various modifications can be made.

DESCRIPTION OF SYMBOLS 1 Image display surface 2 Glass block 3 Virtual aperture 10 Projection zoom lens 11a-11c Transmission type display element 12, 13 Dichroic mirror 14 Cross dichroic prism 16a-16c Condenser lens 18a-18c Mirror 20 Light source 30 Illumination optical system 100 Projection display Devices L11 to L15, L21 to L28 Lens G1 First lens group G2 Second lens group Z Optical axis

Claims (15)

In order from the enlargement side, a first lens group having a negative refractive power and a second lens group having a positive refractive power are arranged in order, and the projection lens is substantially formed.
The interval between the first lens group and the second lens group is set to the maximum lens interval in the entire system,
The first lens group includes a first lens having a negative refractive power and a second lens having a negative refractive power, arranged in order from the most magnified side,
The first lens group is substantially composed of four or five lenses,
A projection lens satisfying the following conditional expressions (1) and (2):
3.0 <f2 / f1 <50.0 (1)
0.80 <D2 / D4 <7.00 (2)
Where f1: focal length of the first lens f2: focal length of the second lens D2: distance between the first lens and the second lens D4: reduction side next to the second lens and the second lens Distance to the lens placed in The projection lens according to claim 1, wherein the following conditional expression (1 ′) is satisfied.
4.0 <f2 / f1 <45.0 (1 ′) The projection lens according to claim 1, wherein the following conditional expression (1 ″) is satisfied.
6.0 <f2 / f1 <40.0 (1 ") The projection lens according to claim 1, wherein the following conditional expression (2 ′) is satisfied.
0.90 <D2 / D4 <5.50 (2 ') The projection lens according to claim 1, wherein the following conditional expression (3) is satisfied.
110 ° <2ω (3)
2ω: Full angle of view on the enlarged side The projection lens according to claim 1, wherein the following conditional expression (4) is satisfied.
−5.0 <F1 / f <−1.0 (4)
Where f: focal length of the entire system F1: focal length of the first lens group The projection lens according to claim 6, wherein the following conditional expression (4 ′) is satisfied.
−3.5 <F1 / f <−1.4 (4 ′) The projection lens according to claim 1, wherein the following conditional expression (5) is satisfied.
2.5 <F2 / f <10.0 (5)
Where f: focal length of the entire system F2: focal length of the second lens group The projection lens according to claim 8, wherein the following conditional expression (5 ′) is satisfied.
4.0 <F2 / f <8.0 (5 ′) The projection lens according to claim 1, wherein the following conditional expression (6) is satisfied.
3.0 <Bf / f (6)
Where f: focal length of the entire system Bf: back focus of the entire system (air equivalent length)   The first lens group is a first lens having a negative refractive power, a second lens having a negative refractive power, and a meniscus lens having a convex surface facing the magnification side in order from the magnification side. 3 lenses, a fourth lens having a positive refractive power, and a fifth lens having a negative refractive power are arranged and substantially constituted, and the fourth lens and the fifth lens are joined to form a negative as a whole. The projection lens according to claim 1, wherein the projection lens has a refractive power.   The projection lens according to claim 11, wherein the third lens and the lens unit having a negative refractive power are brought into focus by moving in the optical axis direction independently of each other.   The first lens group is a first lens having a negative refractive power, a second lens having a negative refractive power, and a meniscus lens having a convex surface facing the magnification side in order from the magnification side. 11. The projection lens according to claim 1, wherein three lenses and a fourth lens having a negative refractive power are arranged substantially. 11.   The projection lens according to claim 13, wherein the third lens and the fourth lens are focused by moving in the optical axis direction independently of each other.   A projection lens according to claim 1, comprising: a light source; a light valve; an illumination optical system that guides a light beam from the light source to the light valve; and the projection lens that modulates the light beam by the light valve. Projecting type display apparatus characterized by projecting on a screen.