JPH11231215A - Image forming lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lens system with which a high resolution can be provided while reducing a color aberration without expanding a device by providing the system with one set of lenses mutually bonding a front lens group arranged on the side of reduction and composing the system of plural lenses so as to have positive power. SOLUTION: An image forming lens system 1 is provided with a front lens group 2, a diaphragm 4 and a rear lens group 3. The front lens group 2 is provided with one set of lenses mutually bonded while being arranged on a reduction side B, for example, and has positive power. The diaphragm 4 is arranged so as to be coincident with the synthetic forcal position of the front lens group 2 on the magnification side A. The rear side lens group 3 is arranged on the magnification side A of the diaphragm 4 and composed of plural lens and has negative power. Besides, the front lens group 2 is composed of a first lens 11 arranged on the reduction side B, a second lens 12 arranged on the magnification side A of the first lens 11, a third lens 13 arranged on the expansion side A of the second lens 12, and fourth lens 14 bonded on the surface of the third lens 13 on the magnification side A.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection type projection optical system used in a recording optical device such as a copying machine or a printer using a light source having a plurality of light emitting portions arranged one-dimensionally or two-dimensionally and independently controllable. The present invention relates to an imaging lens system and a recording optical device using the same, and more particularly, to an imaging lens system and a recording optical device capable of obtaining high resolution without reducing chromatic aberration and increasing the size of the device.

[0002]

2. Description of the Related Art Conventional projection type imaging lenses are disclosed in, for example, JP-A-62-52516 and JP-A-3-72-72.
No. 310 is disclosed.

A conventional imaging lens system disclosed in Japanese Patent Application Laid-Open No. 62-52516 is used for micrographics for reducing an engineering drawing to a micro-image size, and is arranged with an interval therebetween. A first lens group consisting of a pair of meniscus lenses, a second lens group consisting of a double lens and a biconvex lens joined together, a plano-convex lens, A third lens group consisting of a double lens joined together, a fourth lens group consisting of a double lens joined together, and an aperture stop arranged between the second lens group and the third lens group. Have been. According to this imaging lens system, it is possible to provide an ultra-wide-angle lens with a small chromatic aberration and a half angle of view of 33 °.

A conventional image forming lens system disclosed in Japanese Patent Application Laid-Open No. 3-72310 is used for an exposure apparatus in manufacturing a printed circuit board, and is constituted by an image-side telecentric lens system. That is, the imaging lens system includes a first lens having a positive power with a convex surface facing the object side, and a first lens disposed on the image side of the first lens and having a positive power with a convex surface facing the object side. A front lens group including a second lens, a third lens disposed on the image side of the second lens, and having a negative power with a concave surface facing the image side; and a front lens group disposed on the image side of the front lens group. A fourth lens having a concave surface facing the negative power, a fifth lens disposed on the image side of the fourth lens and having a positive power having the concave surface facing the image side, and an image of the fifth lens A sixth lens disposed on the image side and having a positive power with the convex surface facing the image side, and a seventh lens disposed on the image side of the sixth lens and having a positive power with the convex surface facing the object side. Matches the front combined focal position of the rear lens group and the rear lens group It is constituted by a diaphragm which is arranged between the sea urchin front lens group and the rear lens group. According to this imaging lens system, by adopting the telecentric system, the dimensional accuracy of the image is increased, the distance between the object and the image is increased as compared with the screen size, and the aperture ratio is increased, so that the resolution can be improved. .

On the other hand, in recording optical devices such as optical printers and digital copiers of the electrophotographic type, improvement in image quality is required in recent years, and higher precision of print images, that is, improvement in resolution is progressing. An example of such a conventional recording optical device is disclosed in, for example, Japanese Patent Application Laid-Open No. 1-152683. This recording optical device is a laser beam scanner using a semiconductor laser array in which semiconductor lasers are arranged one-dimensionally as a light source. Here, since a semiconductor laser array is used as a light source, a sufficient amount of light is obtained, and a light emitting pattern is projected on a recording surface by an optical system, so that a movable portion is not required. In addition, since a semiconductor laser which is monochromatic light is used as a light source, an optical system corresponding to a single wavelength may be used. Therefore, there is an advantage that chromatic aberration correction is not required.

[0006]

However, Japanese Patent Application Laid-Open No. Sho 62-62
According to the conventional imaging lens system disclosed in Japanese Patent No. 52516, although the lens system for micrographics has a sufficient screen size, the magnification on the enlargement side is as large as 10 times or more, and the F-number is also F / 5. There is a problem that the required resolution cannot be obtained because of the large size. Further, since the reduction side is not a telecentric system, the lens system used here cannot be directly applied to a semiconductor laser array in which the principal rays of laser light emitted from each laser element are parallel. .

According to the conventional imaging lens system disclosed in Japanese Patent Application Laid-Open No. 3-72310, a reduction-side telecentric system is provided. It seems to have a relatively bright and high resolution of about 4. However, since the lens system used in this exposure apparatus has a short focal length and a narrow angle of view on the enlargement side, the lens system here is used as it is to satisfy the screen size (120 mm or more) required for the recording optical apparatus. Then, since a huge lens group is required, there is a problem that there is a limit to achieving high resolution without increasing the size of the apparatus.

According to the conventional recording optical apparatus disclosed in Japanese Patent Application Laid-Open No. 1-152683, a sufficient amount of light can be obtained because a semiconductor laser array is used as a light source, but semiconductor lasers are arranged one-dimensionally. Therefore, there is a limit to integration due to thermal interference and fabrication points.Therefore, there is a limit to high density corresponding to high resolution on the image plane, and even if the magnification is reduced, the semiconductor laser Due to the limitation of the size of the array, there is a problem that the screen has a large screen size and high resolution cannot be obtained. Further, even when a monochromatic semiconductor laser is used, there is a problem that a wavelength difference occurs due to a change in environmental temperature or a variation in the same array, and chromatic aberration occurs.

Accordingly, it is an object of the present invention to provide an imaging lens system and a recording optical device which can obtain high resolution without increasing chromatic aberration and without increasing the size of the apparatus.

[0010]

In order to achieve the above object, the present invention provides an imaging lens for enlarging or reducing incident light from a reduction side or an enlargement side to form an image on an imaging surface. A front lens group having a positive power, including a set of lenses cemented to each other, a diaphragm arranged to coincide with the magnification-side combined focal position of the front lens group, and magnification of the diaphragm And a rear lens group having a plurality of lenses and having a negative power. In order to achieve the above object, the present invention has a plurality of laser elements, a semiconductor laser array that emits a plurality of laser beams from the plurality of laser elements based on an image signal, and is arranged on a reduction side or an enlargement side. An imaging lens system for enlarging or reducing the plurality of laser beams from the plurality of laser elements of the semiconductor laser array to form an image on an imaging surface; and A photosensitive member that is exposed on the image forming surface by the plurality of laser beams irradiated through a lens and forms an electrostatic latent image corresponding to the image signal; The lens system includes a set of lenses disposed on the reduction side and joined to each other, and coincides with a front lens group having a positive power and an enlarged-side combined focal position of the front lens group. A diaphragm which is arranged so disposed in the enlarged side of the diaphragm, a plurality of lenses, to provide a recording optical apparatus characterized by comprising a rear lens group having a negative power.

[0011]

FIG. 1 shows an imaging lens system according to a first embodiment of the present invention. In the figure, the right side shows the enlargement side (object) A, and the left side shows the reduction side (image) B (the same applies to other figures). The image forming lens system 1 includes a reduction side B or an enlargement side A (in this embodiment, the reduction side B
And A) a front lens group 2 having a positive power, including a set of lenses arranged on the reduction side B and joined to each other; A stop 4 arranged to coincide with the magnifying side A combined focal position of the front lens group 2 and a rear lens group 3 arranged on the enlargement side A of the stop 4 and including a plurality of lenses and having a negative power. Have. Note that r _i indicates the radius of curvature of the lens, and d _i indicates the distance between adjacent surfaces of each lens and the distance between the lens surface and the diaphragm 4 (the same applies to the following drawings).

The front lens group 2 of the first embodiment is disposed on the reduction side B and has a first lens 11 having a positive power with a convex surface facing the enlargement side A, and an enlargement side A of the first lens 11.
A second lens 12 having a positive power and a convex surface facing the reduction side B, a third lens 13 disposed on the enlargement side A of the second lens 12 and having a convex surface facing the reduction side B, The fourth lens 14 is joined to the surface on the enlargement side A of the lens 13 and has a concave surface facing the enlargement side A.

The rear lens group 3 according to the first embodiment is disposed on the enlargement side A of the diaphragm, and has a negative lens with a concave surface facing the enlargement side A, and a fifth lens 15 having a negative power. A sixth lens 16 disposed on the enlargement side A and having a positive power with the convex surface facing the reduction side B, and an enlargement side A of the sixth lens 16
And a seventh lens 17 having a negative power with the concave surface facing the reduction side B, and an eighth lens 17 having a negative power with the concave surface facing the reduction side B and arranged on the enlargement side A of the seventh lens 17.
A lens 18 and an enlargement side A of the eighth lens 18,
A ninth lens 19 having a positive power with a convex surface directed to the enlargement side A, and a tenth lens 20 having a positive power with a convex surface directed to the enlargement side A and disposed on the enlargement side A of the ninth lens 19.
Consists of

The operation of the imaging lens system 1 having the above configuration will be described.

Since the rear lens group 3 has a negative power as a whole, the angle of view becomes wide on the enlargement side A, and a large screen size can be obtained. On the other hand, the aberration generated thereby also increases. Therefore, by configuring the rear lens group 3 with a plurality of lenses having negative power, it is possible to reduce the aberration generated by dispersing the power. further,
By introducing a lens having a positive power into the rear lens group 3 and optimizing the configuration of the lens having a negative power and the lens having a positive power, the aberration generated by the negative lens is canceled by the positive lens. The aberration of the entire imaging lens system 1 can be suppressed.

When a semiconductor laser array is used as a light source, generally, light emitted from each laser element is parallel to each other, so that the reduction side B must have a telecentric configuration. Therefore, the front lens group 2 provided on the reduction side B includes at least two positive power lenses. When this group is, for example, one, a bright lens that bends a principal ray parallel to the off-axis optical axis of the laser beam emitted from the semiconductor laser array toward the center of the stop and suppresses aberration so as to be telecentric. It is difficult to do.

In the case where the wavelength of each laser element in the semiconductor laser array fluctuates or the laser wavelength fluctuates due to environmental or temporal changes, a lens system designed for a single wavelength or a narrow wavelength range has a wavelength. Are different, there is a problem of chromatic aberration that the focal position is greatly shifted for each wavelength. Here, the third lens 13 and the fourth lens 14 use lenses with greatly different dispersions and are joined to each other, whereby it is possible to suppress the focal position shift with respect to the wavelength fluctuation.

According to the first embodiment having the above-described configuration, the rear lens group 3 has a negative power, and therefore has a half-field angle of 10 ° or more on the magnifying side A, which is larger than the lens diameter. Large screen size can be obtained. Therefore, the enlargement magnification is 5-1.
0x, focal length as long as 50mm to 100mm, image height 6
Writing can be performed over 0 mm or more. Further, since the front lens group 2 and the rear lens group 3 are composed of a plurality of lenses having a concave surface facing the stop 4, the F-number is as bright as 3 or less, and high resolution is obtained. In addition, since the front lens group 2 has a positive power, the configuration of a telecentric system becomes easy, and a semiconductor laser array that can obtain high resolution without increasing the size of the apparatus can be used as a light source. In addition, since the number of lenses used can be reduced, the overall length of the lens can be reduced to 50 mm to 150 mm, and the size can be reduced. Further, since the third lens 13 and the fourth lens 14 are bonded to each other, the defocus with respect to the wavelength variation is 0.01 mm / nm or less in the wavelength range of 770 nm to 790 nm which is considered to be the wavelength variation range of the semiconductor laser. Become smaller.

FIG. 2 shows an imaging lens system according to a second embodiment of the present invention. The imaging lens system 1 includes a front lens group 2 and an aperture 4 configured in the same manner as in the first embodiment, and a rear lens group 3 configured differently from the first embodiment. .

The rear lens group 3 is disposed on the enlargement side A of the diaphragm 4 and has a fifth lens 15 having a negative power with its concave surface facing the reduction side B, and is disposed on the enlargement side A of the fifth lens 15. A sixth lens 16 having a positive power with a convex surface facing the enlargement side A, and a seventh lens 1 having a negative power with a concave surface facing the reduction side B disposed on the enlargement side A of the sixth lens 16.
7 and the seventh lens 17 on the enlargement side A,
An eighth lens 18 having a positive power with the convex surface facing the
A ninth lens 19 that is disposed on the enlargement side A of the eighth lens 18 and has a positive power with the convex surface facing the enlargement side A, and a ninth lens 19 that is disposed on the enlargement side A of the ninth lens 19 and has a concave surface facing the reduction side B And a tenth lens 20 having negative power.

FIG. 3 shows an imaging lens system according to a third embodiment of the present invention. The imaging lens system 1 includes a front lens group 2 and an aperture 4 configured in the same manner as in the first embodiment, and a rear lens group 3 configured differently from the first embodiment. .

The rear lens group 3 is disposed on the enlargement side A of the stop 4 and has a fifth lens 15 having a negative power with its concave surface facing the reduction side B, and is disposed on the enlargement side A of the fifth lens 15. A sixth lens 16 having a positive power with a convex surface facing the enlargement side A, and a seventh lens 1 having a negative power with a concave surface facing the reduction side B disposed on the enlargement side A of the sixth lens 16.
7 and a reduction side B arranged on the enlargement side A of the seventh lens 17.
An eighth lens 18 having a negative power with the concave surface facing the
A ninth lens 19 that is disposed on the enlargement side A of the eighth lens 18 and has a positive power with the convex surface facing the enlargement side A, and a ninth lens 19 that is disposed on the enlargement side A of the ninth lens 19 and has a concave surface facing the reduction side B And a tenth lens 20 having negative power.

FIG. 4 shows an imaging lens system according to a fourth embodiment of the present invention. The imaging lens system 1 includes a front lens group 2 and an aperture 4 configured in the same manner as in the first embodiment, and a rear lens group 3 configured differently from the first embodiment. .

The rear lens group 3 is disposed on the enlargement side A of the diaphragm 4 and has a fifth lens 15 having a negative power with its concave surface facing the reduction side B, and is disposed on the enlargement side A of the fifth lens 15. A sixth lens 16 having a positive power with a convex surface facing the enlargement side A, and a seventh lens 1 having a negative power with a concave surface facing the reduction side B disposed on the enlargement side A of the sixth lens 16.
7 and the seventh lens 17 on the enlargement side A,
An eighth lens 18 having a negative power with the concave surface facing the
A ninth lens 19 that is disposed on the enlargement side A of the eighth lens 18 and has a positive power with the convex surface facing the enlargement side A, and a ninth lens 19 that is disposed on the enlargement side A of the ninth lens 19 and has a concave surface facing the reduction side B And a tenth lens 20 having negative power.

FIG. 5 shows an imaging lens system according to a fifth embodiment of the present invention. The imaging lens system 1 includes a stop 4 configured in the same manner as in the first embodiment, and a front lens group 2 and a rear lens group 3 having configurations different from those in the first embodiment. .

The front lens group 2 is disposed on the reduction side B,
A first lens 11 having a positive power having a convex surface directed to the enlargement side A, and a second lens 12 having a positive power having a positive surface having a convex surface directed to the reduction side B disposed on the enlargement side A of the first lens 11.
A third lens 13 disposed on the enlargement side A of the second lens 12 and having a concave surface facing the reduction side B; and a third lens 13 joined to the surface on the enlargement side A of the third lens 13 and having a concave surface facing the enlargement side A. And a fourth lens 14.

The rear lens group 3 is disposed on the enlargement side A of the diaphragm 4 and has a fifth lens 15 having a negative power with its concave surface facing the reduction side B, and is disposed on the enlargement side A of the fifth lens 15. A sixth lens 16 having a positive power with a convex surface facing the enlargement side A, and a seventh lens 1 having a negative power with a concave surface facing the reduction side B disposed on the enlargement side A of the sixth lens 16.
7 and a reduction side B arranged on the enlargement side A of the seventh lens 17.
An eighth lens 18 having a negative power with the concave surface facing the
A ninth lens 19 that is disposed on the enlargement side A of the eighth lens 18 and has a positive power with the convex surface facing the enlargement side A, and a ninth lens 19 that is disposed on the enlargement side A of the ninth lens 19 and has a concave surface facing the reduction side B And a tenth lens 20 having negative power.

FIG. 6 shows a recording optical device according to an embodiment of the present invention. The recording optical device 100 includes a semiconductor laser array 101 in which n × m laser elements are arranged in an array, and a laser beam from each laser element can be emitted in parallel and independently at the same time. After converging a plurality of laser beams emitted in parallel from the element to the combined focal position 6a, the photosensitive drum 102 is enlarged at a predetermined angle of view and rotated by a driving device (not shown).
The imaging lens system 1 having the above-described configuration for forming an image thereon, an image memory 103 storing an image signal, reading an image signal from the image memory 103, processing the image signal, and inputting a recording signal according to a recording pattern. A laser processing circuit 104 for inputting a recording signal from the signal processing circuit 104 to drive the semiconductor laser array 101, and outputting a control signal to the laser driving circuit 105 to output the laser driving circuit 105 Control circuit 1 for controlling driving by
06. The recording optical device 100
Although not shown, an image forming means such as a charger, a developing device, and a transfer device is provided around the photoreceptor drum 102, and a paper feed unit for supplying recording paper to the transfer device is provided at a stage preceding the transfer device. A fixing unit that fixes the toner image transferred to the recording paper, a paper discharge unit that discharges the recording paper to which the toner image has been fixed, and the like are provided downstream of the transfer device.

According to the recording optical device 100 having the above configuration,
Even if there is a change in the wavelength of the laser beam due to a change in the environmental temperature, or a change in the wavelength
It is possible to suppress the defocus to be sufficiently small with respect to the depth of focus so that the image quality does not deteriorate. Also, the imaging lens system 1
Is 5 to 10 on the enlarged side A where the photosensitive drum 102 is located.
Since the magnification is twice as large, the size of the light source can be reduced. Further, since the imaging lens system 1 has an F number smaller than 3 and is bright, the spot diameter of the laser beam formed on the photosensitive drum 102 can be reduced, and a high-resolution image can be formed. The imaging lens system 1 has a focal length of 50 to 100 mm and a wide angle of view of a half angle of view of 10 ° or more.
Total length up to 500mm or less, and 60mm
Since the above image height is obtained, the size of the apparatus can be reduced. Further, since the imaging lens system 1 is configured such that the reduction side B is a telecentric system, the semiconductor laser array 101 in which the main beam of the laser beam is parallel to the optical axis can be used on the reduction side B, so that high resolution is achieved. Is obtained.

[0030]

EXAMPLES Example 1 Table 1 shows lens data of the imaging lens system of Example 1 corresponding to the first embodiment shown in FIG.

[Table 1]

In Table 1, ri indicates the radius of curvature of the lens, and di indicates the distance between adjacent surfaces of each lens and the distance between the lens surface and the stop. Also, nj is d
In the refractive index of each lens in the line, νj indicates a dispersion value. The effective focal length f, magnification M, image height IMH, object-side numerical aperture NA, object-image distance TT, and total lens length OAL of the imaging lens system having the lens data are set as follows. f = 59.9798 mm, M = 6, IMH = 60 mm,
NA = 0.169 TT = 446.2155 mm, OAL = 100 mm

FIGS. 7 (a), 7 (b) and 7 (c) and FIGS.
(b) and (c) show the spherical aberration, astigmatism, distortion, and image height of the imaging lens system configured as described above.
The lateral aberrations of 40 mm and 0 mm are shown, respectively. Each of the figures is for 780 nm, which is the wavelength of the semiconductor laser used as the light source on the reduction side B. FIG.
8 and FIG. 8, S represents a sagittal image plane, and T represents a tangential image plane. In the present embodiment, the cemented surface of the third lens 13 and the fourth lens 14 has a convex surface on the reduction side B, and two convex lenses (19, 20) are on the enlargement side A of the eighth lens 18 serving as a diffusion lens. Has been arranged. In the embodiments described later, the same reference numerals as those described above are used, and description thereof will be omitted.

<Example 2> Table 2 shows lens data of the imaging lens system of Example 2 corresponding to the second embodiment shown in FIG.

[Table 2]

The effective focal length f, magnification M, image height IMH, and object side numerical aperture N of the imaging lens system having the above lens data.
A, the object-image distance TT, and the total lens length OAL are set as follows. f = 60.0003 mm, M = 6, IMH = 60 mm,
NA = 0.169 TT = 451.347 mm, OAL = 100 mm

9 (a), 9 (b), 9 (c) and 10 (a),
(b) and (c) show the spherical aberration, astigmatism, distortion, and image height of the imaging lens system configured as described above.
The lateral aberrations of 40 mm and 0 mm are shown, respectively. In this embodiment, the cemented surface of the third lens 13 and the fourth lens 14 has a concave surface on the reduction side B, and the seventh lens 1 serving as a diffusion lens
Between the seventh lens and the tenth lens 20, two convex lenses (18, 1
9) is arranged.

<Example 3> Table 3 shows lens data of the imaging lens system of Example 3 corresponding to the third embodiment shown in FIG.

[Table 3]

Effective focal length f, magnification M, image height IMH, object side numerical aperture N of the imaging lens system having the above lens data
A, the object-image distance TT, and the total lens length OAL are set as follows. f = 59.997 mm, M = 6, IMH = 60 mm, N
A = 0.169 TT = 455.9419 mm, OAL = 100 mm

FIGS. 11 (a), (b) and (c) and FIG. 12 (a)
, (B) and (c) show the spherical aberration, astigmatism, distortion, and image height of the imaging lens system configured as described above.
The lateral aberrations of m, 40 mm, and 0 mm are shown, respectively. In the present embodiment, the cemented surface of the third lens 13 and the fourth lens 14 has a concave surface on the reduction side B, and one convex lens (1) is located between the eighth lens 18 and the tenth lens 20 which are diffusion lenses.
9) is arranged.

Example 4 Table 4 shows lens data of the imaging lens system of Example 4 corresponding to the fourth embodiment shown in FIG.

[Table 4]

Effective focal length f, magnification M, image height IMH, object side numerical aperture N of the imaging lens system having the above lens data
A, the object-image distance TT, and the total lens length OAL are set as follows. f = 59.99999 mm, M = 6, IMH = 60 mm,
NA = 0.169 TT = 457.7729 mm, OAL = 100 mm

FIGS. 13 (a), (b) and (c) and FIG. 14 (a)
, (B) and (c) show the spherical aberration, astigmatism, distortion, and image height of the imaging lens system configured as described above.
The lateral aberrations of m, 40 mm, and 0 mm are shown, respectively. In the present embodiment, the cemented surface of the third lens 13 and the fourth lens 14 has a concave surface on the reduction side B, and one convex lens (1) is located between the seventh lens 17 and the tenth lens 20 which are diffusion lenses.
9) and one concave lens (18).

Example 5 Table 5 shows lens data of the imaging lens system of Example 5 corresponding to the fifth embodiment shown in FIG.

[Table 5]

The effective focal length f, magnification M, image height IMH, and object side numerical aperture N of the imaging lens system having the above lens data.
A, the object-image distance TT, and the total lens length OAL are set as follows. f = 59.9884 mm, M = 6, IMH = 60 mm,
NA = 0.169 TT = 431.9372 mm, OAL = 100 mm

FIGS. 15 (a), (b) and (c) and FIG. 16 (a)
, (B) and (c) show the spherical aberration, astigmatism, distortion, and image height of the imaging lens system configured as described above.
The lateral aberrations of m, 40 mm, and 0 mm are shown, respectively. In the present embodiment, the cemented surface of the third lens 13 and the fourth lens 14 has a convex surface on the reduction side B, and one convex lens (1) is located between the eighth lens 18 and the tenth lens 20 which are diffusion lenses.
9) is arranged, and the distortion is reduced to 0.1% or less.

Example 6 Table 6 shows lens data of the imaging lens system of Example 6 corresponding to the first embodiment shown in FIG.

[Table 6]

Effective focal length f, magnification M, image height IMH, object side numerical aperture N of the imaging lens system having the above lens data
A, the object-image distance TT, and the total lens length OAL are set as follows. f = 59.975 mm, M = 6, IMH = 60 mm,
NA = 0.169 TT = 455.8984 mm, OAL = 100 mm

FIGS. 18 (a), (b), (c) and FIG. 19 (a)
, (B) and (c) show the spherical aberration, astigmatism, distortion, and image height of the imaging lens system configured as described above.
The lateral aberrations of m, 40 mm, and 0 mm are shown, respectively. In the present embodiment, the cemented surface of the third lens 13 and the fourth lens 14 has a convex surface on the reduction side B, and two convex lenses (19, 20) are on the enlargement side A of the seventh lens 17 serving as a diffusion lens. Has been arranged.

<Embodiment 7> FIG. 20 shows an imaging lens system of Embodiment 7 corresponding to the third embodiment shown in FIG.
Table 7 shows lens data of the imaging lens system of Example 7.

[Table 7]

Effective focal length f, magnification M, image height IMH, object side numerical aperture N of the imaging lens system having the above lens data
A, the object-image distance TT, and the total lens length OAL are set as follows. f = 59.9868 mm, M = 6, IMH = 60 mm,
NA = 0.169 TT = 444.4361 mm, OAL = 100 mm

FIGS. 21 (a), (b) and (c) and FIG. 22 (a)
, (B) and (c) show the spherical aberration, astigmatism, distortion, and image height of the imaging lens system configured as described above.
The lateral aberrations of m, 40 mm, and 0 mm are shown, respectively. In the present embodiment, the cemented surface of the third lens 13 and the fourth lens 14 has a concave surface on the reduction side B, and one convex lens (1) is located between the eighth lens 18 and the tenth lens 20 which are diffusion lenses.
9) is arranged, and the distortion is reduced to 0.1% or less.

<Eighth Embodiment> FIG. 23 shows an imaging lens system of an eighth embodiment corresponding to the second embodiment shown in FIG.
Table 8 shows lens data of the imaging lens system of Example 8.

[Table 8]

Effective focal length f, magnification M, image height IMH, object side numerical aperture N of the imaging lens system having the above lens data
A, the object-image distance TT, and the total lens length OAL are set as follows. f = 59.9847 mm, M = 6, IMH = 60 mm,
NA = 0.169 TT = 447.2252 mm, OAL = 100 mm

FIGS. 24 (a), (b) and (c) and FIG. 25 (a)
, (B) and (c) show the spherical aberration, astigmatism, distortion, and image height of the imaging lens system configured as described above.
The lateral aberrations of m, 40 mm, and 0 mm are shown, respectively. In the present embodiment, the cemented surface of the third lens 13 and the fourth lens 14 has a concave surface on the reduction side B, and two convex lenses (1) are located between the seventh lens 17 and the tenth lens 20 which are diffusion lenses.
8, 19) to reduce distortion to 0.1% or less.

<Embodiment 9> FIG. 26 shows an imaging lens system of Embodiment 9 corresponding to the third embodiment shown in FIG.
Table 9 shows lens data of the imaging lens system of Example 9.

[Table 9]

Effective focal length f, magnification M, image height IMH, object side numerical aperture N of the imaging lens system having the above lens data
A, the object-image distance TT, and the total lens length OAL are set as follows. f = 59.9863 mm, M = 6, IMH = 60 mm,
NA = 0.169 TT = 449.892 mm, OAL = 100 mm

FIGS. 27 (a), (b) and (c) and FIG. 28 (a)
, (B) and (c) show the spherical aberration, astigmatism, distortion, and image height of the imaging lens system configured as described above.
The lateral aberrations of m, 40 mm, and 0 mm are shown, respectively. In the present embodiment, the cemented surface of the third lens 13 and the fourth lens 14 has a concave surface on the reduction side B, and one convex lens (1) is located between the eighth lens 18 and the tenth lens 20 which are diffusion lenses.
9) is arranged, and the distortion is reduced to 0.1% or less.

In the present embodiment, the semiconductor laser array has a flat plate shape, and each laser element emits a principal ray of laser light parallel to each other in a direction perpendicular to the surface.
Since the size of the semiconductor laser array is not negligible with respect to the diameter of the lens system, the reduction side B is a telecentric system, but when the semiconductor laser array is arranged on a spherical surface or a curved surface, Even if the semiconductor laser array is flat, if the principal ray of the laser beam of each laser beam is directed to the aperture of the lens, the design is easier than that of the telecentric system. It can be used after correction.

[0058]

As described above, according to the present invention,
Since the front lens group disposed on the reduction side includes a pair of lenses joined to each other, chromatic aberration can be reduced. In addition, since the front lens group arranged on the reduction side is composed of a plurality of lenses so as to have a positive power, the configuration of the telecentric system becomes easy, and high resolution can be achieved without increasing the size of the apparatus. The obtained semiconductor laser array can be used as a light source. Further, the rear lens group arranged on the magnifying side is composed of a plurality of lenses so as to have a negative power, so that a wide angle can be achieved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a configuration of an imaging lens system according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view illustrating a configuration of an imaging lens system according to a second embodiment of the present invention.

FIG. 3 is a sectional view showing a configuration of an imaging lens system according to a third embodiment of the present invention.

FIG. 4 is a sectional view showing a configuration of an imaging lens system according to a fourth embodiment of the present invention.

FIG. 5 is a sectional view showing a configuration of an imaging lens system according to a fifth embodiment of the present invention.

FIG. 6 is a perspective view illustrating a schematic configuration of a recording optical device according to an embodiment of the present invention.

FIG. 7 is a diagram illustrating various aberrations in the first embodiment of the present invention.
(a) is a spherical aberration diagram, (b) is an astigmatism diagram, and (c) is a distortion diagram.

FIG. 8 is a lateral aberration diagram according to the first embodiment of the present invention;
(a) is a lateral aberration diagram at an image height of 60 mm, (b) is a lateral aberration diagram at an image height of 40 mm, and (c) is a lateral aberration diagram at an image height of 0 mm.

FIG. 9 is a diagram illustrating various aberrations in the second embodiment of the present invention.
(a) is a spherical aberration diagram, (b) is an astigmatism diagram, and (c) is a distortion diagram.

FIG. 10 is a lateral aberration diagram according to the second embodiment of the present invention.
(a) is a lateral aberration diagram at an image height of 60 mm, (b) is a lateral aberration diagram at an image height of 40 mm, and (c) is a lateral aberration diagram at an image height of 0 mm.

FIG. 11 is a diagram illustrating various aberrations in the third embodiment of the present invention.
(a) is a spherical aberration diagram, (b) is an astigmatism diagram, and (c) is a distortion diagram.

FIG. 12 is a lateral aberration diagram in the third embodiment of the present invention.
(a) is a lateral aberration diagram at an image height of 60 mm, (b) is a lateral aberration diagram at an image height of 40 mm, and (c) is a lateral aberration diagram at an image height of 0 mm.

FIG. 13 is a diagram illustrating various aberrations in the fourth embodiment of the present invention.
(a) is a spherical aberration diagram, (b) is an astigmatism diagram, and (c) is a distortion diagram.

FIG. 14 is a lateral aberration diagram in Example 4 of the present invention.
(a) is a lateral aberration diagram at an image height of 60 mm, (b) is a lateral aberration diagram at an image height of 40 mm, and (c) is a lateral aberration diagram at an image height of 0 mm.

FIG. 15 is a diagram illustrating various aberrations in the fifth embodiment of the present invention.
(a) is a spherical aberration diagram, (b) is an astigmatism diagram, and (c) is a distortion diagram.

FIG. 16 is a lateral aberration diagram in the fifth embodiment of the present invention.
(a) is a lateral aberration diagram at an image height of 60 mm, (b) is a lateral aberration diagram at an image height of 40 mm, and (c) is a lateral aberration diagram at an image height of 0 mm.

FIG. 17 is a sectional view illustrating a configuration of an imaging lens system according to Example 6 of the invention.

FIG. 18 is a diagram illustrating various aberrations in the sixth embodiment of the present invention.
(a) is a spherical aberration diagram, (b) is an astigmatism diagram, and (c) is a distortion diagram.

FIG. 19 is a lateral aberration diagram in the sixth embodiment of the present invention.
(a) is a lateral aberration diagram at an image height of 60 mm, (b) is a lateral aberration diagram at an image height of 40 mm, and (c) is a lateral aberration diagram at an image height of 0 mm.

FIG. 20 is a sectional view illustrating a configuration of an imaging lens system according to Example 7 of the invention.

FIG. 21 is a diagram illustrating various aberrations in the seventh embodiment of the present invention.
(a) is a spherical aberration diagram, (b) is an astigmatism diagram, and (c) is a distortion diagram.

FIG. 22 is a lateral aberration diagram in the seventh embodiment of the present invention.
(a) is a lateral aberration diagram at an image height of 60 mm, (b) is a lateral aberration diagram at an image height of 40 mm, and (c) is a lateral aberration diagram at an image height of 0 mm.

FIG. 23 is a sectional view showing a configuration of an imaging lens system according to Example 8 of the present invention.

FIG. 24 is a diagram illustrating various aberrations in the eighth embodiment of the present invention.
(a) is a spherical aberration diagram, (b) is an astigmatism diagram, and (c) is a distortion diagram.

FIG. 25 is a lateral aberration diagram in Example 8 of the present invention.
(a) is a lateral aberration diagram at an image height of 60 mm, (b) is a lateral aberration diagram at an image height of 40 mm, and (c) is a lateral aberration diagram at an image height of 0 mm.

FIG. 26 is a cross-sectional view illustrating a configuration of an imaging lens system according to Example 9 of the invention.

FIG. 27 is a diagram illustrating various aberrations in the ninth embodiment of the present invention.
(a) is a spherical aberration diagram, (b) is an astigmatism diagram, and (c) is a distortion diagram.

FIG. 28 is a lateral aberration diagram in the ninth embodiment of the present invention.
(a) is a lateral aberration diagram at an image height of 60 mm, (b) is a lateral aberration diagram at an image height of 40 mm, and (c) is a lateral aberration diagram at an image height of 0 mm.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Imaging lens system 2 Front lens group 3 Rear lens group 4 Aperture 4a Synthetic focal position 11 First lens 12 Second lens 13 Third lens 14 Fourth lens 15 Fifth lens 16 Sixth lens 17 Seventh lens 18th 8 lens 19 ninth lens 20 10th lens 100 recording optical device 101 semiconductor laser array 102 photosensitive drum 103 image memory 104 signal processing circuit 105 laser drive circuit 106 control circuit A enlargement side B reduction side

Claims (7)

[Claims] An imaging lens for enlarging or reducing incident light from a reduction side or an enlargement side to form an image on an imaging surface, comprising: a set of lenses arranged on the reduction side and joined to each other; A front lens group having a positive power, a diaphragm arranged to coincide with the magnifying side combined focal position of the front lens group, and a plurality of lenses arranged on the magnifying side of the diaphragm,
An imaging lens system comprising: a rear lens group having negative power. 2. The first lens group, wherein the first lens group is disposed on the reduction side and has a positive power with a convex surface facing the enlargement side.
A lens, a second lens disposed on the enlargement side of the first lens and having a positive power with a convex surface facing the reduction side, and a second lens disposed on the enlargement side of the second lens and having a convex surface on the reduction side. And a fourth lens joined to the surface on the enlargement side of the third lens and having a concave surface facing the enlargement side. The rear lens group is disposed on the enlargement side of the diaphragm. A fifth power source having a negative power with a concave surface facing the magnifying side;
A lens, a sixth lens disposed on the enlarged side of the fifth lens and having a positive power with a convex surface facing the reduced side, and a sixth lens disposed on the enlarged side of the sixth lens and concave on the reduced side A seventh lens having a negative power and a negative lens disposed on the enlargement side of the seventh lens and having a concave surface facing the reduction side;
A ninth lens disposed on the enlargement side of the lens and having a positive power with the convex surface facing the enlargement side; and a positive power disposed on the enlargement side of the ninth lens with the convex surface facing the enlargement side. And a tenth lens having:
An imaging lens system as described. 3. The first lens group, wherein the front lens group is disposed on the reduction side and has a positive power with a convex surface facing the enlargement side.
A lens, a second lens disposed on the enlargement side of the first lens and having a positive power with the convex surface facing the reduction side, and a lens disposed on the enlargement side of the second lens and convex on the reduction side And a fourth lens joined to the surface on the enlargement side of the third lens and having a concave surface facing the enlargement side.
A fifth lens group having a negative power, the rear lens group being disposed on the enlargement side of the diaphragm and having a concave surface facing the reduction side.
A lens, a sixth lens disposed on the enlarged side of the fifth lens and having a positive power with a convex surface facing the enlarged side, and a sixth lens disposed on the enlarged side of the sixth lens and concave on the reduced side A seventh lens having a negative power directed toward the zoom lens, an eighth lens disposed on the magnifying side of the seventh lens and having a positive power with a convex surface facing the magnifying side,
A ninth lens disposed on the enlargement side of the lens and having a positive power with the convex surface facing the enlargement side; and a negative power disposed on the enlargement side of the ninth lens with a concave surface facing the reduction side. And a tenth lens having:
An imaging lens system as described. 4. The first lens group, wherein the front lens group is disposed on the reduction side and has a positive power with a convex surface facing the enlargement side.
A lens, a second lens disposed on the enlargement side of the first lens and having a positive power with the convex surface facing the reduction side, and a lens disposed on the enlargement side of the second lens and convex on the reduction side And a fourth lens joined to the surface on the enlargement side of the third lens and having a concave surface facing the enlargement side.
A fifth lens group having a negative power, the rear lens group being disposed on the enlargement side of the diaphragm and having a concave surface facing the reduction side.
A lens, a sixth lens disposed on the enlarged side of the fifth lens and having a positive power with a convex surface facing the enlarged side, and a sixth lens disposed on the enlarged side of the sixth lens and concave on the reduced side A seventh lens having a negative power and a negative lens disposed on the enlargement side of the seventh lens and having a concave surface facing the reduction side;
A ninth lens disposed on the enlargement side of the lens and having a positive power with the convex surface facing the enlargement side; and a negative power disposed on the enlargement side of the ninth lens with a concave surface facing the reduction side. And a tenth lens having:
An imaging lens system as described. 5. The first lens group, wherein the front lens group is disposed on the reduction side and has a positive power with a convex surface facing the enlargement side.
A lens, a second lens disposed on the enlargement side of the first lens and having a positive power with the convex surface facing the reduction side, and a lens disposed on the enlargement side of the second lens and convex on the reduction side And a fourth lens joined to the surface on the enlargement side of the third lens and having a concave surface facing the enlargement side.
A fifth lens group having a negative power, the rear lens group being disposed on the enlargement side of the diaphragm and having a concave surface facing the reduction side.
A lens, a sixth lens disposed on the enlarged side of the fifth lens and having a positive power with a convex surface facing the enlarged side, and a sixth lens disposed on the enlarged side of the sixth lens and concave on the reduced side A seventh lens having a negative power, the eighth lens being disposed on the enlarged side of the seventh lens, and having a negative power with a concave surface facing the enlarged side;
A ninth lens disposed on the enlargement side of the lens and having a positive power with the convex surface facing the enlargement side; and a negative power disposed on the enlargement side of the ninth lens with a concave surface facing the reduction side. And a tenth lens having:
An imaging lens system as described. 6. The first lens group, which is disposed on the reduction side and has a positive power with a convex surface facing the enlargement side.
A lens, a second lens disposed on the enlargement side of the first lens and having a positive power with a convex surface facing the reduction side, and a lens disposed on the enlargement side of the second lens and concave on the reduction side And a fourth lens joined to the surface on the enlargement side of the third lens and having a concave surface facing the enlargement side.
A fifth lens group having a negative power, the rear lens group being disposed on the enlargement side of the diaphragm and having a concave surface facing the reduction side.
A lens, a sixth lens disposed on the enlarged side of the fifth lens and having a positive power with a convex surface facing the enlarged side, and a sixth lens disposed on the enlarged side of the sixth lens and concave on the reduced side A seventh lens having a negative power and a negative lens disposed on the enlargement side of the seventh lens and having a concave surface facing the reduction side;
A ninth lens disposed on the enlargement side of the lens and having a positive power with the convex surface facing the enlargement side; and a negative power disposed on the enlargement side of the ninth lens with a concave surface facing the reduction side. And a tenth lens having:
An imaging lens system as described. 7. A semiconductor laser array having a plurality of laser elements and emitting a plurality of laser beams from the plurality of laser elements based on image signals, and a semiconductor laser array arranged on a reduction side or an enlargement side. An imaging lens system for enlarging or reducing the plurality of laser beams from the plurality of laser elements to form an image on an imaging surface; emitted from the plurality of laser elements and irradiated through the imaging lens A photosensitive member that is exposed on the image forming surface by the plurality of laser beams to form an electrostatic latent image corresponding to the image signal. A front lens group having a positive power and including a set of lenses cemented to each other, and a diaphragm arranged to coincide with an enlarged-side combined focal position of the front lens group. When disposed in the enlarged side of the diaphragm, a plurality of lenses, recording optical apparatus characterized by comprising a rear lens group having a negative power.