JP2015118235A - Zoom lens and image projection device including the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a zoom lens that has a wide angle of view, a high zoom ratio, and little fluctuations in optical performance even when temperature varies, and that easily gives a projected image of high picture qualities..SOLUTION: The following factors are each suitably set in the zoom lens. The factors are: a focal distance fp of an aspherical lens; a focal distance ft of the whole system at a telephoto end; a refractive power φ of all lenses constituting a lens group LB; a change amount dφ of the refractive power per unit temperature change in all lenses constituting the lens group LB; and a change amount of a refractive index dn/dt per unit temperature change of the material of each lens in all lenses constituting the lens group LB.

Description

  The present invention relates to a zoom lens, and is suitable as a projection lens used in an image projection apparatus (projector) that enlarges and projects an image on a screen, for example.

  Conventionally, various image projection apparatuses (projectors) that use an image display element such as a liquid crystal and enlarge and project an image based on the image display element onto a screen surface by a projection optical system have been proposed. There is a demand for a compact zoom lens capable of projecting at various magnifications, projecting on a large screen at a short distance, and having a wide angle of view and high zoom ratio with good portability. Further, since a color splitting optical system or a color synthesizing optical system composed of a prism member, a filter, or the like is disposed between the projection optical system and the image display element, a long back focus is desired.

  In many cases, the ambient temperature of the projector rises due to heat from the light source for illumination. For this reason, the optical performance of the projection optical system used in the projector changes, for example, the focus position, as the temperature rises. For this reason, there is a demand for a small change in optical performance even when the environment changes. As a zoom lens that satisfies these demands, there is known a retrofocus zoom lens in which a lens unit having a negative refractive power is arranged on the most magnification conjugate side and a lens group having a positive refractive power is located on the most reduction conjugate side. (Patent Documents 1 and 2).

  In Patent Document 1, an aspherical lens made of a plastic material is used for the lens group closest to the enlargement conjugate side and the lens group closest to the reduction conjugate side, and the wide angle of view and high zoom are reduced by reducing changes in optical performance (focus position) due to temperature changes. A ratio retrofocus zoom lens is disclosed. Patent Document 2 discloses a retrofocus zoom lens having a wide field angle and high optical performance in which an aspherical lens is a lens having the smallest effective diameter.

  In addition, there is known a projector that reduces fluctuations in optical performance due to temperature changes (Patent Document 3). Patent Document 3 discloses a projector in which various factors such as a linear expansion coefficient, a refractive index of a lens material, and a thermal expansion of a lens barrel are appropriately set to reduce a variation in focus position (focus position) due to a temperature change. Yes.

JP 2011-100081 A JP 2008-83229 A JP 2004-264570 A

  A zoom lens used in a projector is strongly demanded to have a high-quality projected image and a small change in optical performance due to a temperature change. In order to obtain a high-quality projected image, it is effective to use an aspheric lens made of a resin material (plastic material). However, the resin material has a large refractive index change with temperature compared to a general glass material. For this reason, when a lens made of a resin material is used, the optical performance, particularly the focus position fluctuation (temperature focus fluctuation) increases as the temperature changes.

  For this reason, when using an aspherical lens made of a resin material, it is important to configure each lens group so that a change in optical performance accompanying a change in temperature is reduced. For example, it is important for which lens group that constitutes a zoom lens an aspheric lens made of a resin material, and how to reduce the fluctuation of the focus position due to a temperature change. Furthermore, it is important to appropriately set the level of the refractive power (power) of an aspheric lens made of a resin material.

  For example, in Patent Document 1, an aspheric lens made of a resin material is disposed on the most conjugated side. Since this aspherical lens has a weak refractive power (power), there is little change in the focus position due to a temperature change, but aberration correction by the aspherical surface is not always sufficient.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a zoom lens that can easily obtain a high-quality projected image with a wide angle of view, a high zoom, and a small change in optical performance even when there is a temperature change, and an image projection apparatus having the zoom lens.

The zoom lens according to the present invention includes a first lens group having a negative refractive power on the most conjugate side, a final lens group having a positive refractive power on the most reducing conjugate side, an aperture stop in the optical path, and an adjacent lens for zooming. In zoom lenses where the distance between groups changes,
The first lens group has an aspheric lens made of a plastic material, and is on the reduction conjugate side of the aperture stop in the lens group that moves during zooming.
The lens unit LB closest to the aperture stop moves from the reduction conjugate side to the enlargement conjugate side during zooming from the wide-angle side to the telephoto side,
The focal length of the aspheric lens is fp, the focal length of the entire system at the telephoto end is ft, all the lenses constituting the lens group LB are refracting power, and all the lenses constituting the lens group LB are unit temperature. The change in refractive power per change is dφ, and the change in refractive index per unit temperature change of the material is dn / dt for all lenses constituting the lens group LB.
dφ = dn / dt * φ
When you leave
0.3 <| ft / fp | <0.6
−0.4 <dφ <0
It satisfies the following conditional expression.

  According to the present invention, it is possible to obtain a zoom lens that can easily obtain a high-quality projection image with a wide angle of view, a high zoom, and a small change in optical performance even when there is a temperature change.

(A), (B) Lens cross-sectional views at the wide-angle end and the telephoto end of Embodiment 1 of the present invention (A), (B) Aberration diagrams at the wide-angle end and the telephoto end of Example 1 of the present invention. (A), (B) Lens cross-sectional view at the wide-angle end and the telephoto end of the second embodiment of the present invention (A), (B) Aberration diagrams at the wide-angle end and the telephoto end of Example 2 of the present invention. (A), (B) Lens cross-sectional views at the wide-angle end and the telephoto end of Embodiment 3 of the present invention (A), (B) Aberration diagrams at the wide-angle end and the telephoto end of Example 3 of the present invention. Sectional drawing of the principal part of the image projection apparatus using the zoom lens of this invention

  Examples of the zoom lens according to the present invention will be described below. The zoom lens of the present invention has a first lens group having a negative refractive power on the most conjugate side, a final lens group having a positive refractive power on the most conjugate side, and an aperture stop in the optical path, and adjacent lens groups for zooming. The interval of changes.

  FIGS. 1A and 1B are lens cross-sectional views at the wide-angle end (short focal length end) and the telephoto end (long focal length end) of Embodiment 1 of the zoom lens according to the present invention. 2A and 2B are longitudinal aberration diagrams at the wide-angle end and the telephoto end when the projection distance is 2100 mm in Embodiment 1 of the zoom lens according to the present invention. Here, the projection distance is a distance from the projected image. 3A and 3B are lens cross-sectional views at the wide-angle end and the telephoto end of the second embodiment of the zoom lens according to the present invention. FIGS. 4A and 4B are longitudinal aberration diagrams at the wide-angle end and the telephoto end when the projection distance is 2100 mm in Embodiment 2 of the zoom lens according to the present invention.

  5A and 5B are lens cross-sectional views at the wide-angle end and the telephoto end of Embodiment 3 of the zoom lens according to the present invention. 6A and 6B are longitudinal aberration diagrams at the wide-angle end and the telephoto end when the projection distance is 2100 mm in Embodiment 3 of the zoom lens according to the present invention. FIG. 7 is a schematic view of a main part of an image projection apparatus having a zoom lens according to the present invention.

  The zoom lens of each embodiment is a projection lens (projection optical system) that projects an original image formed by an image display element used in an image projection apparatus (projector). In the lens cross-sectional view, the left is the enlargement conjugate side (screen) (front), and the right is the reduction conjugate side (image display element side) (rear). LA is a zoom lens.

  LF is the front group and LR is the rear group. Bi is the i-th lens group. ST is an aperture stop. IE corresponds to an original image (projected image) of a liquid crystal panel (image display element) or the like. S is the screen surface. GB is an optical block corresponding to a prism for color separation and color synthesis, an optical filter, a face plate (parallel plate glass), a crystal low-pass filter, an infrared cut filter, and the like.

  The arrows indicate the movement direction (movement locus) of the lens group during zooming from the wide-angle end to the telephoto end. The wide-angle end and the telephoto end are zoom positions when the zooming lens units are positioned at both ends of a range in which the zoom lens group can move on the optical axis. In the aberration diagrams, Fno is the F number, and ω is the half angle of view (degrees). In the spherical aberration diagram, the paraxial image surface at the d-line is used as a reference and the wavelength is 550 nm. In the astigmatism diagram, the paraxial image plane at the d-line is used as a reference, the dotted line indicates the meridional image plane, and the solid line indicates the sagittal image plane. The distortion diagram shows the wavelength of 550 nm with reference to the paraxial image plane at the d-line.

  The zoom lens of each embodiment has a front group LF on the enlargement conjugate side and a rear group LR on the reduction conjugate side with the aperture stop ST as a boundary. The front lens group LF sequentially moves from the magnification conjugate side to the reduction conjugate side during the focusing operation, the first lens unit B1 having a negative refractive power, the second lens unit B2 having a positive refractive power, and the third lens unit B3 having a positive refractive power. have.

  In the rear group LR, in order from the magnification conjugate side to the reduction conjugate side, a fourth lens unit B4 having a negative refractive power, a fifth lens unit B5 having a positive refractive power, and a sixth lens unit having a positive refractive power (final lens group). It consists of B6. The first lens unit B1 and the sixth lens unit B6 do not move during zooming. During zooming from the wide-angle end to the telephoto end, the second lens unit B2 to the fifth lens unit B5 move to the magnification conjugate side.

  The first lens group B1 and the sixth lens group B6 are lens groups that do not contribute to zooming, and the second lens group B2 to the fifth lens group B5 are zooming lens groups. The fourth lens unit B4 is a lens unit LB that is closer to the reduction conjugate than the aperture stop ST and is closest to the aperture stop ST among the lens units that move during zooming.

  Each embodiment is a zoom lens used in an image projection apparatus having a light valve (particularly, a three-plate projector equipped with a liquid crystal display element). The zoom lens of each embodiment may be used as an image pickup optical system for an image pickup apparatus using an image pickup element instead of a light valve.

  The zoom lens according to each exemplary embodiment includes six lens groups of negative, positive, positive, negative, positive, and positive refractive powers of the first lens unit B1 to the sixth lens unit B6 in order from the magnification conjugate side to the reduction conjugate side. doing. During zooming, the second lens unit B2 to the fifth lens unit B5 move. An aperture stop ST that moves during zooming is provided between the third lens unit B3 and the fourth lens unit B4.

  In each embodiment, an aspherical lens made of a plastic material having a large refractive power is arranged in the first lens unit B1 on the magnification conjugate side with respect to the aperture stop ST. The lens unit LB closest to the aperture stop ST on the reduction conjugate side with respect to the aperture stop ST is moved from the reduction conjugate side to the enlargement conjugate side during zooming from the wide angle side to the telephoto side. Then, the moving direction of the focus position due to the temperature change of all the lenses constituting the lens unit LB is configured to be opposite to that of the aspherical lens. Thereby, the optical performance is favorably maintained while suppressing a change in the focus position with respect to a temperature change of the entire lens.

  In each embodiment, the first lens unit B1 has an aspheric lens made of a plastic material. Among the lens units that move during zooming, the lens unit LB that is closer to the reduction conjugate side than the aperture stop ST and is closest to the aperture stop SP moves from the reduction conjugate side to the enlargement conjugate side during zooming from the wide-angle side to the telephoto side.

Let fp be the focal length of the aspheric lens. Let ft be the focal length of the entire system at the telephoto end. All lenses constituting the lens group LB have a refractive power of φ, all lenses constituting the lens group LB have a refractive power change per unit temperature change of dφ, and all lenses constituting the lens group LB are made of materials. Let dn / dt be the amount of change in refractive index per unit temperature change. And dφ = dn / dt * φ
When you leave
0.3 <| ft / fp | <0.6 (1)
−0.4 <dφ <0 (2)
The following conditional expression is satisfied. Next, the technical meaning of each conditional expression will be described.

  If the absolute value of the focal length of the aspheric lens increases beyond the lower limit value of the conditional expression (1) (the absolute value of the negative refractive power decreases), aberration correction by the aspheric surface becomes insufficient. Further, if the absolute value of the focal length of the aspheric lens becomes smaller than the upper limit value (when the absolute value of the negative refractive power becomes larger), aberration correction by the aspheric surface becomes excessive, which is not good.

  In each embodiment, by using an aspheric lens satisfying conditional expression (1), good optical performance is obtained over the entire zoom range. Since the material of the aspherical lens is made of resin, the change in refractive power (power) due to temperature change is large, and the variation in optical performance is large. Accordingly, among the lens groups that move during zooming, the lens configuration of the lens group LB that is closer to the reduction conjugate side than the aperture stop SP and is closest to the aperture stop SP is appropriately set to reduce fluctuations in optical performance due to temperature changes. Yes. For example, fluctuations in focus position due to temperature changes are reduced.

  Specifically, the amount of change in the refractive index of the material per unit temperature rise is dn / dt, and the lens power is φ. At this time, the amount of change dφ of the lens power per unit temperature rise can be expressed as follows.

dφ = dn / dt * φ
The refractive power of the aspheric lens in each embodiment is negative. The aspheric lens is made of a resin material, and the refractive index variation dn / dt of the resin material is dn / dt <0
It is. Therefore, the amount of change dφ in the power of the aspheric lens is
0 <dφ
It becomes.

  On the other hand, the lenses constituting the lens unit LB closest to the aperture stop ST on the reduction conjugate side from the aperture stop SP satisfy the conditional expression (2). As a result, changes in the focus position of the entire system due to temperature changes are kept small.

  Conditional expression (2) means that the configuration is such that the focus correction direction due to the temperature change of all the lenses constituting the lens unit LB is opposite to that of the aspherical lens. Conditional expression (2) is for effectively correcting a focus change due to a temperature change generated in the aspherical lens. By satisfying conditional expression (2), the change of the focus position with respect to the temperature change of the entire zoom lens is suppressed to be small.

  If the upper limit value or lower limit value of conditional expression (2) is exceeded, it will be difficult to effectively correct the change in focus position due to the temperature change. More preferably, the numerical ranges of conditional expressions (1) and (2) are set as follows.

0.3 <| ft / fp | <0.5 (1a)
−0.3 <dφ <0 (2a)
Further, since the focus sensitivity of the change in the focus position with respect to the temperature change is greater at the telephoto end than at the wide-angle end, the change in the focus position with respect to the temperature change at the telephoto end is large.

  Usually, the change in the focus position with respect to the temperature change is proportional to the power change amount dφ and the height of the on-axis marginal ray from the optical axis.

  In the present invention, the lens unit LB is moved from the reduction conjugate side to the enlargement conjugate side during zooming from the wide-angle side to the telephoto side. As a result, the height h of the on-axis marginal ray from the optical axis at the telephoto end is higher than that at the wide-angle end, so that the telephoto end has the effect of correcting the focus change due to the temperature change. By adopting this configuration, the change in the focus position with respect to the temperature change of the entire zoom lens is kept small even in the entire zoom range.

  In each embodiment, it is more preferable to satisfy one or more of the following conditional expressions. The lens unit LB has at least one positive lens, and the refractive index and Abbe number of the positive lens material are nd and νd, respectively. Let fw be the focal length of the entire system at the wide-angle end. The distance at the wide-angle end from the aperture stop ST to the lens surface on the reduction conjugate side of the lens unit LB is L4w, and the total lens length is L.

  Here, the total lens length L is a value obtained by adding back focus in terms of air to the distance from the first lens surface to the final lens surface. The back focus is a distance in terms of air from the final lens surface to the image plane. At this time, one or more of the following conditional expressions should be satisfied.

50 <νp <100 (3)
1.40 <np <1.75 (4)
ft / fw <2.5 (5)
0.10 <L4w / L <0.35 (6)

  Satisfying the conditional expressions (3) and (4) means using a material having a high refractive index while the power variation dφ is dφ <0. Thereby, the power of at least one positive lens included in the lens unit LB can be set large, and various aberrations can be effectively corrected. Furthermore, since the expansion coefficient with respect to the temperature change of the material of the positive lens is relatively small, it becomes easy to process into a cemented lens or the like. Further, it becomes easy to construct the positive lens with a normal low dispersion / low refractive index material (abnormal dispersion material), and the selectivity of the material is improved.

  Conditional expression (5) defines the range of zoom magnification (zoom ratio). The sensitivity of movement (fluctuation) of the focus position with respect to temperature changes increases from the wide-angle end to the telephoto end. As the zoom ratio increases, the movement of the focus position due to temperature changes increases. If the zoom ratio increases beyond the upper limit value of conditional expression (5), the variation of the focus position with respect to the temperature change caused by zooming increases, which is not good.

  Conditional expression (6) defines the distance of the lens unit LB from the aperture stop ST. If the lens group LB is not positioned within a predetermined distance from the aperture stop ST to the reduction conjugate side by deviating from the conditional expression (6), the lens group LB effectively changes the focus position by the aspherical lens due to the temperature change. It becomes difficult to correct. More preferably, the numerical ranges of conditional expressions (3) to (6) are set as follows.

60 <νp <85 (3a)
1.45 <np <1.75 (4a)
1.5 <ft / fw <2.0 (5a)
0.15 <L4w / L <0.30 (6a)

  In each embodiment, in order from the magnification conjugate side to the reduction conjugate side, the first lens unit B1 is a meniscus negative lens having a convex surface on the object side, a meniscus negative lens having a convex surface on the object side, a biconcave negative lens, and a biconvex lens. It consists of a positive lens with a shape. The second lens unit B2 is composed of a positive lens having a convex surface facing the object side. The third lens unit B3 is composed of a positive lens having a convex surface facing the object side.

  The fourth lens unit B4 includes, in order from the magnification conjugate side to the reduction conjugate side, a cemented lens in which a biconcave negative lens and a biconvex positive lens are cemented, a magnification negative lens having a concave conjugate side, and a biconvex positive It consists of a lens. The fifth lens unit B5 includes a cemented lens in which a biconcave negative lens and a biconvex positive lens are cemented. The sixth lens unit B6 is composed of a positive lens having a convex surface facing the magnification conjugate side. By configuring the lens configuration of each lens group as described above, there is obtained a zoom lens in which various aberrations during zooming are small and good optical performance can be obtained over the entire zoom range.

  The image projection apparatus in FIG. 7 will be described. In FIG. 7, reference numeral 41 denotes a light source. Reference numeral 42 denotes an illumination optical system that realizes illumination with less unevenness on the image display element and has a function of aligning the polarization direction of emitted light to an arbitrary direction of P-polarized light or S-polarized light. A color separation optical system 43 separates light from the illumination optical system 42 into an arbitrary color corresponding to the image display element.

  Reference numerals 47, 48, and 49 denote image display elements made of reflective liquid crystal that modulates incident polarized light according to an electric signal. Reference numerals 44 and 45 denote polarization beam splitters that transmit or reflect light according to modulation by the image display elements 47, 48, and 49. A color combining optical system 46 combines the light from the image display elements 47, 48, and 49 into one. Reference numeral 50 denotes a projection optical system that projects light synthesized by the color synthesis optical system 46 onto a projection object such as a screen 51. The zoom lens of the present invention is used for the projection optical system 50. Thereby, changes in various aberrations during zooming are corrected favorably, and an image projection apparatus having good optical performance over the entire screen is obtained.

  As mentioned above, although preferable embodiment of this invention was described, this invention is not limited to these embodiment, A various deformation | transformation and change are possible within the range of the summary.

  Next, numerical examples of the zoom lens of each embodiment will be shown. Surface numbers in the lens configuration of Numerical Example 1 (Table A) are numbers assigned to the respective lens surfaces in order from the magnification conjugate side to the reduction conjugate side. r represents the radius of curvature of each lens surface, and d represents the distance (physical distance) on the optical axis between the lens surface i and the lens surface (i + 1).

The interval described as variable in the table changes with zooming. Further, nd and νd indicate the refractive index and the Abbe number for the d-line of the material constituting each lens, respectively. Table 1 shows the focal length, the aperture ratio (F number), the half angle of view, the total lens length, the air equivalent back focus (BF), the zoom ratio, and the distance between the lens groups during zooming. (Table B) shows aspheric coefficients A to G for indicating the aspheric shape. y represents the coordinate in the radial direction of the lens surface, and x represents the coordinate in the optical axis direction. Furthermore, E-X indicates a ^{10 -X.}

At this time, the aspherical shape is as follows.
x = (y ² / R) / [1+ {1− (1 + K) (y ² / R ² )} ^1/2 ] + Ay ⁴ + By ⁶ + Cy ⁸ + Dy ¹⁰ + Ey ¹² + Fy ¹⁴ + Gy ¹⁶
Table 1 shows the relationship between the above-described embodiments and numerical values.

Numerical example 1

(A) Lens configuration

Wide angle telephoto
f (focal length) 21.78 39.20
F (aperture ratio) 2.8 2.8
Half angle of view (degrees) 31.0 18.5
Total lens length 167.9
BF 58.2
Zoom ratio 1.80

r1 = 56.19 d1 = 4.00 n1 = 1.805 ν1 = 25.4
r2 = 25.59 d2 = 8.20
r3 = 80.00 d3 = 3.03 n2 = 1.531 ν2 = 55.9
r4 = 32.22 d4 = 12.23
r5 = -31.78 d5 = 3.00 n3 = 1.487 ν3 = 70.2
r6 = 180.84 d6 = 5.01
r7 = 226.61 d7 = 6.91 n4 = 1.806 ν4 = 33.3
r8 = -50.67 d8 = variable
r9 = 59.63 d9 = 3.46 n5 = 1.487 ν5 = 70.2
r10 = 185.24 d10 = variable
r11 = 52.61 d11 = 4.08 n6 = 1.834 ν6 = 37.2
r12 = 326.80 d12 = variable
r13 = ∞ d13 = variable
r14 = -266.18 d14 = 1.30 n7 = 1.751 ν7 = 31.7
r15 = 18.63 d15 = 8.76 n8 = 1.487 ν8 = 70.4
r16 = -28.72 d16 = 1.33
r17 = -19.55 d17 = 1.30 n9 = 1.805 ν9 = 25.4
r18 = -573.79 d18 = 0.50
r19 = 130.84 d19 = 8.59 n10 = 1.497 ν10 = 81.5
r20 = -23.31 d20 = variable
r21 = -63.20 d21 = 1.85 n11 = 1.686 ν11 = 32.0
r22 = 76.16 d22 = 7.67 n12 = 1.755 ν12 = 27.6
r23 = -53.54 d23 = variable
r24 = 75.14 d24 = 4.45 n13 = 1.805 ν13 = 25.4
r25 = -488.19 d25 = 2.3
r26 = ∞ d26 = 30.0 n14 = 1.516 ν14 = 64.1
r27 = ∞ d27 = 1.9
r28 = ∞ d28 = 17.7 n15 = 1.805 ν15 = 25.4
r29 = ∞ d29 = 5.0
r30 = ∞ d30 = 2.3 n16 = 1.516 ν16 = 64.1
r31 = ∞

When zoomed (2100mm)
Group spacing Wide angle Telephoto
d8 40.48 8.92
d10 15.57 4.13
d12 6.28 32.38
d13 19.39 1.50
d20 1.57 7.51
d23 1.00 29.85

(B) Aspheric coefficient

r3 K = 0 A = 1.73E-05 B = -3.17E-08 C = 2.98E-11 D = 1.09E-13
E = -1.13E-16 F = -3.59E-19 G = 6.86E-22
r4 K = 0 A = 1.22E-05 B = -3.39E-08 C = -1.53E-11 D = 1.03E-13
E = 1.31E-15 F = -5.79E-18 G = 7.26E-21

Numerical example 2

(A) Lens configuration

Wide angle telephoto
f (focal length) 21.74 39.15
F (aperture ratio) 2.8 2.8
Half angle of view (degrees) 31.0 18.5
Total lens length 167.0
BF 58.2
Zoom ratio 1.80

r1 = 39.55 d1 = 2.30 n1 = 1.805 ν1 = 25.4
r2 = 25.13 d2 = 8.31
r3 = 56.20 d3 = 3.50 n2 = 1.531 ν2 = 55.9
r4 = 23.99 d4 = 12.12
r5 = -33.58 d5 = 3.48 n3 = 1.487 ν3 = 70.2
r6 = 71.34 d6 = 1.31
r7 = 113.53 d7 = 5.87 n4 = 1.806 ν4 = 33.3
r8 = -56.79 d8 = variable
r9 = 40.90 d9 = 2.35 n5 = 1.487 ν5 = 70.2
r10 = 46.16 d10 = variable
r11 = 50.23 d11 = 4.20 n6 = 1.834 ν6 = 37.2
r12 = -1346.65 d12 = variable
r13 = 1E + 18 d13 = variable
r14 = -114.53 d14 = 1.30 n7 = 1.751 ν7 = 31.7
r15 = 19.47 d15 = 8.40 n8 = 1.487 ν8 = 70.4
r16 = -29.86 d16 = 1.21
r17 = -20.34 d17 = 1.30 n9 = 1.805 ν9 = 25.4
r18 = -714.24 d18 = 0.52
r19 = 126.09 d19 = 7.60 n10 = 1.497 ν10 = 81.5
r20 = -24.32 d20 = variable
r21 = -99.97 d21 = 1.85 n11 = 1.686 ν11 = 32.0


r22 = 37.87 d22 = 9.25 n12 = 1.755 ν12 = 27.6
r23 = -64.70 d23 = variable
r24 = 55.37 d24 = 3.70 n13 = 1.805 ν13 = 25.4
r25 = 169.88 d25 = 2.3
r26 = ∞ d26 = 30.0 n14 = 1.516 ν14 = 64.1
r27 = ∞ d27 = 1.9
r28 = ∞ d28 = 17.7 n15 = 1.805 ν15 = 25.4
r29 = ∞ d29 = 5.0
r30 = ∞ d30 = 2.3 n16 = 1.516 ν16 = 64.1
r31 = ∞

When zoomed (2100mm)
Group spacing Wide angle Telephoto
d8 48.23 13.23
d10 12.82 4.82
d12 4.98 29.95
d13 19.91 3.58
d20 1.50 11.18
d23 1.00 25.68

(B) Aspheric coefficient


r3 K = 0 A = 8.26E-06 B = -9.80E-09 C = 3.73E-11 D = -3.35E-13 E = 8.06E-16
F = 1.28E-18 G = -4.06E-21
r4 K = 0 A = -1.35E-07 B = -2.91E-08 C = 1.77E-10 D = -1.52E-12 E = 2.17E-15
F = 1.58E-17 G = -4.07E-20

Numerical Example 3

(A) Lens configuration

Wide angle telephoto
f (focal length) 21.78 39.20
F (aperture ratio) 2.8 2.8
Half angle of view (degrees) 31.0 18.5
Total lens length 164.2
BF 58.2
Zoom ratio 1.80

r1 = 35.62 d1 = 2.50 n1 = 1.805 ν1 = 25.4
r2 = 25.53 d2 = 7.59
r3 = 79.08 d3 = 3.00 n2 = 1.531 ν2 = 55.9
r4 = 32.11 d4 = 16.30
r5 = -30.46 d5 = 2.00 n3 = 1.487 ν3 = 70.2
r6 = 67.66 d6 = 4.98
r7 = 264.92 d7 = 4.55 n4 = 1.806 ν4 = 33.3
r8 = -56.77 d8 = variable
r9 = 47.30 d9 = 2.35 n5 = 1.487 ν5 = 70.2
r10 = 55.12 d10 = variable
r11 = 50.39 d11 = 4.20 n6 = 1.834 ν6 = 37.2
r12 = -5389.26 d12 = variable
r13 = 1E + 18 d13 = variable
r14 = -302.07 d14 = 1.30 n7 = 1.751 ν7 = 31.7
r15 = 17.15 d15 = 8.75 n8 = 1.487 ν8 = 70.4
r16 = -29.14 d16 = 1.28
r17 = -19.44 d17 = 1.30 n9 = 1.805 ν9 = 25.4
r18 = 503.38 d18 = 0.50
r19 = 96.84 d19 = 8.16 n10 = 1.497 ν10 = 81.5
r20 = -22.71 d20 = variable
r21 = -95.95 d21 = 1.85 n11 = 1.686 ν11 = 32.0
r22 = 30.03 d22 = 9.25 n12 = 1.755 ν12 = 27.6
r23 = -67.24 d23 = variable
r24 = 62.41 d24 = 3.70 n13 = 1.805 ν13 = 25.4
r25 = 281.63 d25 = 2.3
r26 = ∞ d26 = 30.0 n14 = 1.516 ν14 = 64.1
r27 = ∞ d27 = 1.9
r28 = ∞ d28 = 17.7 n15 = 1.805 ν15 = 25.4
r29 = ∞ d29 = 5.0
r30 = ∞ d30 = 2.3 n16 = 1.516 ν16 = 64.1
r31 = ∞

When zoomed (2100mm)
Group spacing Wide angle Telephoto
d8 37.70 7.61
d10 17.12 4.21
d12 6.40 32.65
d13 18.47 0.66
d20 0.50 6.08
d23 0.50 29.47

(B) Aspheric coefficient

r3 K = 0 A = 1.90E-05 B = -4.62E-08 C = 1.08E-10 D = -5.51E-14
E = -2.15E-16 F = 6.97E-19 G = -6.25E-22
r4 K = 0 A = 1.44E-05 B = -5.39E-08 C = 1.01E-10 D = 4.20E-14
E = -7.87E-16 F = 3.12E-18 G = -4.30E-21

B1 1st lens group B2 2nd lens group B3 3rd lens group B4 4th lens group B5 5th lens group B6 6th lens group

Claims (6)

A zoom lens that has a first lens unit having a negative refractive power on the most conjugated side, a final lens unit having a positive refracting power on the most conjugated side, and an aperture stop in the optical path. In the lens,
The first lens group has an aspheric lens made of a plastic material, and is on the reduction conjugate side of the aperture stop in the lens group that moves during zooming.
The lens unit LB closest to the aperture stop moves from the reduction conjugate side to the enlargement conjugate side during zooming from the wide-angle side to the telephoto side,
The focal length of the aspheric lens is fp, the focal length of the entire system at the telephoto end is ft, all the lenses constituting the lens group LB are refracting power, and all the lenses constituting the lens group LB are unit temperature. The change in refractive power per change is dφ, and the change in refractive index per unit temperature change of the material is dn / dt for all lenses constituting the lens group LB.
dφ = dn / dt * φ
When you leave
0.3 <| ft / fp | <0.6
−0.4 <dφ <0
A zoom lens satisfying the following conditional expression: The lens group LB has at least one positive lens, and when the refractive index and Abbe number of the material of the positive lens are nd and νd, respectively,
50 <νp <100
1.40 <np <1.75
The zoom lens according to claim 1, wherein the following conditional expression is satisfied. The zoom lens, in order from the magnification conjugate side to the reduction conjugate side,
A first lens group having a negative refractive power, a second lens group having a positive refractive power, a third lens group having a positive refractive power, a fourth lens group having a negative refractive power, a fifth lens group having a positive refractive power, 2. The sixth lens group having a positive refractive power, wherein the second lens group, the third lens group, the fourth lens group, and the fifth lens group move during zooming. 2 zoom lens. When the focal length of the entire system at the wide angle end is fw
ft / fw <2.5
The zoom lens according to claim 1, wherein the following conditional expression is satisfied. When the distance at the wide-angle end from the aperture stop to the lens surface on the reduction conjugate side of the lens unit LB is L4w, and the total lens length is L,
0.10 <L4w / L <0.35
The zoom lens according to claim 1, wherein the following conditional expression is satisfied.   6. An image projection comprising: the zoom lens according to claim 1; and an image display element that forms an original image, and the original image formed by the image display element is projected by the zoom lens. apparatus.