JP2011221132A - Imaging optical device - Google Patents

Abstract

An inexpensive imaging optical device capable of making a light source array pitch in a light source array and an imaging position array pitch in an image plane equal to each other.
An imaging optical apparatus 1 includes a first lens array 10 including _I lenses A _{1 to} A _I arranged in an array and a second lens including _I lenses B _{1 to} B _I arranged in an array. The lens array 20 and a light guide array 40 including _I light guides G _{1 to} G _I arranged in an array are provided. The optical axis of the lens A _{i and} the optical axis of the lens B _i coincide with each other. The light guide array 40 is provided between the first lens array 10 and the second lens array 20. The light guide G _i is provided on the optical axes of the lenses A _i and B _i . A light-shielding part C is provided between two light guide parts adjacent to each other among the _I light guide parts G _{1 to} GI.
[Selection] Figure 2

Description

  The present invention relates to an imaging optical apparatus.

  An imaging optical device including a lens array including a plurality of lenses arranged in an array is used in an image reading device, an LED printer, or the like. For example, in an LED printer, the imaging optical device as described above is used with a light source array including a plurality of LEDs arranged in an array. Each LED included in the light source array selectively emits light according to an electrical signal, and light output from the LED is imaged on a photosensitive drum through a corresponding lens included in the lens array. Generally, two or more LEDs are imaged by one lens.

  Such an imaging optical device may be configured to include a SELFOC lens array (registered trademark). In this case, an erecting equal-magnification imaging optical system can be realized. However, Selfoc lenses are expensive.

  Further, the imaging optical device may be configured to include a first lens array and a second lens array each including a plurality of ordinary lenses arranged in an array. When only one lens array including a plurality of normal lenses arranged in an array is used, a reversed image is obtained. Therefore, the images are reversed by the first lens array and the second lens array, respectively, so that the erecting equal magnification The imaging optical system can be realized. Such an imaging optical device is inexpensive because each of the first lens array and the second lens array can be manufactured by resin molding or the like.

  However, in the imaging optical device configured to include the first lens array and the second lens array, the light output from the light source is imaged through the corresponding lenses included in the first lens array and the second lens array, respectively. In addition to being imaged at a predetermined position on the surface, it reaches another position on the image surface via a lens different from the corresponding lens. That is, the problem of crosstalk occurs.

  The invention disclosed in Patent Document 1 is intended to solve such a problem of crosstalk. The imaging optical device disclosed in Patent Document 1 includes a light shielding plate provided with a minute light-transmitting portion between a first lens array and a second lens array. Light that is to be imaged at a predetermined position on the image plane through the corresponding lens passes through the light transmitting portion of the light shielding plate, but is directed to another position on the image plane through a lens different from the corresponding lens. Is blocked by the light shielding plate, so that crosstalk is suppressed.

JP 2008-278048 A

  However, in the imaging optical device disclosed in Patent Document 1, it is necessary that the translucent portion provided on the light shielding plate has a certain width, and therefore, in the image plane than the light source arrangement pitch in the light source array. The imaging position array pitch increases, and the resolution on the image plane decreases.

  The present invention has been made to solve the above-described problems, and provides an inexpensive imaging optical apparatus capable of making the light source array pitch in the light source array and the imaging position array pitch in the image plane equal to each other. For the purpose.

The imaging optical device of the present invention includes (1) a first lens array including _I lenses A _{1 to} A _I arranged in an array, and (2) I lenses B _{1 to} B _I arranged in an array. A second lens array in which the optical axis of each lens B _{i and} the optical axis of the lens A _i coincide with each other; and (3) an array arrangement provided between the first lens array and the second lens array. been comprises I-number of the light guide portion _G 1 ~G _I, each of the light guide portion _{G i} is the lens _a i, provided on the optical axis of _{B i,} of the I-number of the light guide portion _G 1 ~G _I And a light guide section array in which a light shielding section is provided between two adjacent light guide sections. However, I is an integer greater than or equal to 2, and i is each integer greater than or equal to 1 and less than or equal to I.

In the imaging optical device of the present invention, light to be imaged at a predetermined position on the image plane among the light output from the light source passes through the lens A _i , the light guide G _i, and the lens B _i in order. Imaged on top. On the other hand, of the light output from the light source, light that may cause crosstalk on the image plane is blocked by the light shielding unit.

In the imaging optical device of the present invention, the central axis of the light guide G _i may coincide with the optical axes of the lenses A _i and B _i . The optical imaging system of the present invention, the refractive index of the light guide G _i is n, when a lens arrangement pitch of each of the first lens array and the second lens array and a phi, the optical axis of the light guide G _i May be longer than φ / tan {sin ⁻¹ (1 / n)}. The optical imaging system of the present invention, the shape of the cross section perpendicular to the optical axis of the light guide portion G _i may be rectangular or trapezoidal.

The imaging optical device of the present invention further includes a light source array including _J light sources S _{1 to} S _J arranged in an array, wherein the lens arrangement pitch in each of the first lens array and the second lens array is φ, and the light source array Is provided at a distance L1 longer than twice the focal length f of the lens A _i from the main plane of the first lens array, and the light incident surface of the light guide array is from the main plane of the first lens array. provided at a distance L, when the opening half-width of the light guide section G _i is assumed to be H, may satisfy the following equation (1) relation. However, J is an integer of 2 or more.

  Any one or more of the first lens array, the second lens array, and the light guide section array may be integrally formed. Further, the first lens array, the second lens array, and the light guide section array may be integrally formed.

  In the imaging optical device of the present invention, the light source array pitch in the light source array and the imaging position array pitch in the image plane can be made equal to each other, and can be made inexpensive.

It is a figure which shows the structure of the imaging optical apparatus 2 of a comparative example. It is a figure which shows the structure of the imaging optical apparatus 1 of this embodiment. It is a perspective view which shows the structural example of the light guide part array 40 contained in the imaging optical apparatus 1 of this embodiment. It is a figure which shows an example of the light intensity distribution in the image surface P at the time of using the imaging optical apparatus 1 of this embodiment. It is a figure which shows an example of the light intensity distribution in the image surface P at the time of using the imaging optical apparatus 2 of a comparative example. Is a diagram showing an optical system of the light guide portion of the optical imaging system 1 G _i around the present embodiment. It is a perspective view which shows the other structural example of the light guide part array 40 contained in the imaging optical apparatus 1 of this embodiment. It is a perspective view which shows the specific example of a structure of the imaging optical apparatus 1 of this embodiment.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted. First, the configuration of the imaging optical device of the comparative example will be described, and then the configuration of the imaging optical device of the present embodiment will be described.

  FIG. 1 is a diagram showing a configuration of an imaging optical device 2 of a comparative example. The imaging optical device 2 of this comparative example includes a first lens array 10, a second lens array 20, and a light source array 30. The principal planes of the first lens array 10, the second lens array 20, and the light source array 30 are parallel to each other.

The first lens array 10 includes I aspheric lenses A _{1 to} A _I arranged in an array. The I lenses A _{1 to} A _I have a common size and a common focal length, and are arranged at a constant pitch. The second lens array 20 includes I aspheric lenses B _{1 to} B _I arranged in an array. The I lenses B _{1 to} B _I have a common size and a common focal length, and are arranged at a constant pitch. The optical axis of the lens A _{i and} the optical axis of the lens B _i coincide with each other.

The light source array 30 includes J light sources S _{1 to} S _J arranged in an array. The J light sources S _{1 to} S _J are, for example, LEDs having a common configuration, and are arranged at a constant pitch. In the drawing, the trajectories of the light beams output from the two light sources S _j1 and S _j2 among the _J light sources S _{1 to} S _J included in the light source array 30 are shown. I and J are integers of 2 or more. i is an integer of 1 to I. j1 and j2 are integers of 1 or more and J or less.

The imaging magnification of each lens A _i of the first lens array 10 provided at the front stage is M, and the imaging magnification of each lens B _i of the second lens array 20 provided at the rear stage is 1 / M. To do. M is a positive number less than 1. It is assumed that the distance between the light source S _j1 and the light source S _j2 is W. At this time, if there are light sources _{S j1} and the light source _{S j2} is within the range of the same width as the array pitch of the lens _{A i,} each source _{S j1} and the light source _{S j2} distance MW in the image plane of the first lens array 10 An image is formed at a distant position, and the image is formed again at positions P _ji and P _j2 separated by a distance W on the image plane P of the second lens array 20. Thus, the light focused on the predetermined positions P _ji and P _j2 passes through the lens A _i and the lens B _i having a common optical axis.

However, the light that has not been imaged in the range MW on the image plane of the first lens array 10 reaches a position other than the positions P _ji and P _j2 on the image plane P of the second lens array 20, Cross talk. The light to be crosstalk as, instead of passing through the lens A _i and a lens B _i having a common optical axis, passes through the lens A _i1 and lens B _i2 having different optical axis from each other. Here, i1 and i2 are different numbers.

Therefore, the imaging optical device 1 according to the present embodiment uses the light guide array 40 provided between the first lens array 10 and the second lens array 20 to cause the lens A _i and the lens B having a common optical axis. _While selectively passing light passing through _i , crosstalk is suppressed by selectively blocking light that may pass through the lens A _i1 and the lens B _i2 having different optical axes. .

  FIG. 2 is a diagram illustrating a configuration of the imaging optical device 1 of the present embodiment. The imaging optical device 1 of this embodiment further includes a light guide array 40 in addition to the configuration of the imaging optical device 2 of the comparative example. The main planes of the first lens array 10, the second lens array 20, the light source array 30, and the light guide section array 40 are parallel to each other.

The light guide array 40 is provided between the first lens array 10 and the second lens array 20 and includes _I light guides G _{1 to} G _I arranged in an array. The I light guides G _{1 to} G _I have a common configuration and are arranged at a constant pitch. The light guide portion G _i is the lens A _i, is provided on the optical axis of the B _i, selectively passes the light toward the lens A _i to the lens B _i. It is preferable that the central axis of the light guide G _i coincides with the optical axes of the lenses A _i and B _i . A light-shielding part C is provided between two light guide parts adjacent to each other among the _I light guide parts G _{1 to} GI. The light shielding part C selectively blocks light by absorbing, refracting, or scattering light from the lens A _i1 to the lens B _i2 .

FIG. 3 is a perspective view illustrating a configuration example of the light guide unit array 40 included in the imaging optical device 1 of the present embodiment. The light guide array 40 shown in this figure has a rectangular parallelepiped shape as a whole, a plurality of grooves parallel to each other are formed on one surface, and a rectangular cross-section portion between two adjacent grooves There is a light guide portion G _i, the light-shielding portion C is inserted into each of the plurality of grooves. The light shielding part C may be a black paint, for example. The light guide array 40 can be manufactured by immersing the rectangular parallelepiped member in a black paint in a state where the light incident / exit surface of the transparent rectangular parallelepiped member formed with a plurality of grooves is masked. Such a configuration of the light guide portion array 40, the light guide portion G _i are readily produced by a molding, also, the light shielding portion C may also be readily produced.

FIG. 4 is a diagram illustrating an example of the light intensity distribution on the image plane P when the imaging optical device 1 of the present embodiment is used. FIG. 5 is a diagram showing an example of the light intensity distribution on the image plane P when the comparative imaging optical device 2 is used. Here, a specific configuration example of the imaging optical devices 1 and 2 is as follows. Lens _{A i} of the first lens array 10, lens _{B i} and the light guide portion _{G i} respective refractive index of the light guide array 40 of the second lens array 20 is 1.5. The focal length of the lens A _i of the first lens array 10 at the front stage is 2 mm, and the imaging magnification of the lens A _i is ¼. Focal length of the lens _{B i} of the subsequent second lens array 20 is 1.5 mm, the imaging magnification of the lens _{B i} is 4. The arrangement pitch of the I-number of the lens _A 1 to A pitch of the _I, I-number of lens _B 1 .about.B _I arrangement pitch and I-number of the light guide portion _G 1 ~G _I are both 1 mm. The thickness of the light-shielding part C provided between two light guide parts adjacent to each other among the _I light guide parts G _{1 to} GI is 0.1 mm.

  Further, the distance between the light emitting surface of the light source array 30 and the light incident surface of the first lens array 10 is 8.2 mm. The distance between the light incident surface and the light exit surface of the first lens array 10 is 1 mm. The distance between the light emitting surface of the first lens array 10 and the light incident surface of the light guide unit array 40 is 1.5 mm. The distance between the light incident surface and the light emitting surface of the light guide array 40 is 2 mm. The distance between the light emitting surface of the light guide array 40 and the light incident surface of the second lens array 20 is 1 mm. The distance between the light incident surface and the light exit surface of the second lens array 20 is 1 mm. The distance between the light exit surface of the second lens array 20 and the image plane P is 6.2 mm.

_{Assume that} each of the two light sources S _j1 and S _j2 outputs light. The light emission area of each of the light sources S _j1 and S _j2 is 10 μm square. The light source S _j1 is located at the center of the light source array 30, and the light source S _j2 is located at a distance of 0.5 mm from the center. Regardless of which one of the imaging optical device 1 of this embodiment and the imaging optical device 2 of the comparative example is used, the distance between the image positions P _ji and P _j2 of the light sources S _j1 and S _{j2 on} the image plane P is The distance between the light sources S _j1 and S _j2 is 0.5 mm. Further, an erecting equal-magnification imaging optical system is realized, and a light source image having the same arrangement pitch as the arrangement pitch of the light sources is obtained.

However, as shown in FIG. 5, when the imaging optical device 2 of the comparative example is used, a position 4.5 mm away from the positions P _ji and P _j2 where the light source image is to be formed on the image plane P. There is also a light peak, which is crosstalk. On the other hand, as shown in FIG. 4, when the imaging optical device 1 of this embodiment is used, the peak of light that causes crosstalk as in the comparative example is not recognized on the image plane P. .

Figure 6 is a diagram showing an optical system of the light guide portion G _i around the optical imaging system 1 of the present embodiment. Opening half-width H of the light guide G _i is preferably larger than the position h of the light beam to reach through the outermost light incident surface of the light guide portion G _i of the lens A _i. The distance from the main plane P ₁₀ of the first lens array 10 and the light incident surface of the light guide portion array 40 and L. Let the focal length of the lens A _{i be} f. Further, the arrangement pitch of each of the _I lenses A _{1 to} A _I , the I lenses B _{1 to} B _I, and the I light guide portions G _{1 to} G _I is φ.

Assume a light source having a light emitting position in the main distance from the plane _{P 10 (1 + 1 / M} ) distance from the optical axis of an f lens A _i (φ / 2) apart at the first lens array 10. If the light guide portion G _i is assumed not to exist, the position Q _i in which the light output from the light source is condensed by lens A _i is the distance from the main plane P ₁₀ of the first lens array 10 (1 + M) f And at a distance (Mφ / 2) from the optical axis of the lens A _i .

From the similarity of two triangles indicated by hatching in the figure, the position h of the light ray that reaches the light incident surface of the light guide part G _i through the outermost part of the lens A _i is expressed by the equation (2). . Here, if the distance between the main plane P ₁₀ and the light emitting surface of the light source of the first lens array 10 and L1 ((3) below), (2) is converted to (4) below.

In order to arrange the position of the image by the first lens array near the optical axis, M needs to be smaller than 1. Therefore, the distance L1 between the main plane P ₁₀ and the light emitting surface of the light source of the first lens array 10 is equal to or greater than 2 times the focal length f of the lens A _i.

Incidentally, when the cross-sectional shape of the light guide portion G _i of the light guide portion array 40 as shown in FIG. 7 is a trapezoid, an opening half-width H of the light guide G _i, an array on the optical axis of the lens A _i It is defined by the direction width. In the figure, the illustration of the light shielding portion is omitted.

When the refractive index of the light guide G _i is n, the maximum value θ of the angle formed by the light beam that has passed through the lens A _i and then enters the light guide G _i from the air layer and the optical axis is Snell's law Therefore, θ = sin ⁻¹ (1 / n). To enable the effect of the light shielding portion C of the light guide portion G _i side preferably has a length in the optical axis direction of the light guide G _i is greater than phi / tan .theta.

  FIG. 8 is a perspective view showing a specific example of the configuration of the imaging optical device 1 of the present embodiment. In the imaging optical device 1 shown in this figure, the first lens array 10, the second lens array 20, and the light guide section array 40 are integrally formed. Any two of the first lens array 10, the second lens array 20, and the light guide section array 40 may be integrally formed. In these cases, it is not necessary to adjust the optical axis during assembly.

  The imaging optical device 1 of the present embodiment can not only make the light source array pitch in the light source array and the image formation position array pitch in the image plane equal to each other, but can also suppress crosstalk. Further, since each of the first lens array 10, the second lens array 20, and the light guide section array 40 can be manufactured by resin molding or the like, the imaging optical device 1 of the present embodiment can be manufactured at low cost.

The imaging optical device 1 according to the present embodiment includes a light shielding plate provided with a small light-transmitting portion that is inserted between the first lens array and the second lens array in the imaging optical device disclosed in Patent Document 1. In addition, the lens A includes the light guide part array 40 including the _I light guide parts G _{1 to} G _I arranged in an array and including a light shielding part between two adjacent light guide parts. The openings of _i and B _i can be enlarged.

Therefore, the imaging optical device 1 of the present embodiment can form a light source image on the image plane P with the same resolution as the arrangement pitch of the _J light sources S _{1 to} S _J arranged in the light source array 30. while for selectively passing the light to be imaged in a predetermined position by the guide portion G _i, can block light that may be crosstalk selectively by the light shielding unit.

Further, the optical imaging system 1 of the present embodiment, the arrangement pitch of the array arranged light guide portion G _i in the light guide portion array 40, a lens A _i which are arrayed in the lens array 10, _20, the B _i Since the pitch can be the same as the arrangement pitch, the light guide array 40 can also be manufactured at a low cost.

  In addition, the imaging optical device 1 according to the present embodiment makes the first lens array 10 and the second lens array 20 inexpensive by increasing the distance between the first lens array 10 and the second lens array 20. In addition, the degree of freedom in design is high.

DESCRIPTION OF SYMBOLS 1 ... Imaging optical apparatus, 10 ... 1st lens array, 20 ... 2nd lens array, 30 ... Light source array, 40 ... Light guide part array

Claims (6)

A first lens array including _I lenses A _{1 to} A _I arranged in an array;
A second lens array including _I lenses B _{1 to} B _I arranged in an array, wherein the optical axis of each lens B _{i and} the optical axis of the lens A _i coincide with each other;
The light guides G _{1 to} G _I are provided between the first lens array and the second lens array and arranged in an array, and each of the light guides G _{i corresponds} to the lenses A _i and B _i . A light guide section array provided on the optical axis and having a light shielding section between two adjacent light guide sections among the _I light guide sections G _{1 to} G _I ;
(Where I is an integer of 2 or more and i is an integer of 1 or more and I or less). 2. The imaging optical device according to claim 1, wherein the central axis of the light guide part G _i coincides with the optical axes of the lenses A _i and B _i . When the refractive index of the light guide G _i is n and the lens arrangement pitch in each of the first lens array and the second lens array is φ, the length of the light guide G _{i in} the optical axis direction is φ / tan The imaging optical apparatus according to claim 1, wherein the imaging optical apparatus is longer than {sin ⁻¹ (1 / n)}. Optical imaging system of claim 1, the shape of the cross section perpendicular to the optical axis of the light guide portion G _i is characterized by a rectangular or trapezoidal. A light source array including _J light sources S _{1 to} S _J arranged in an array;
The lens arrangement pitch in each of the first lens array and the second lens array is φ, and the light exit surface of the light source array is a distance longer than twice the focal length f of the lens A _i from the main plane of the first lens array. provided at a position of L1, the light incident surface of the light guide portion arrays are arranged at a distance L from the main plane of the first lens array, when the opening half-width of the light guide section G _i is assumed to be H,

Satisfy the relationship
The imaging optical device according to claim 1, wherein J is an integer of 2 or more. The imaging optical device according to claim 1, wherein any two or more of the first lens array, the second lens array, and the light guide section array are integrally formed.

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