JP2011221175A - Imaging optical apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a low-cost imaging optical apparatus that can make a light source arrangement pitch in a light source array equal to an imaging position arrangement pitch on an image surface.SOLUTION: An imaging optical apparatus 1 comprises a first lens array 10 including I-pieces of lenses Ato Aarranged in an array, a second lens array 20 including I-pieces of lenses Bto Barranged in an array, and a light guide array 40 including I-pieces of light guide sections Gto Garranged in an array. An optical axis of the lens Aand an optical axis of the lens Bare aligned with each other. The light guide array 40 is positioned between the first lens array 10 and the second lens array 20. The light guide section Gis provided on the optical axis of the lenses Aand B. The light guide section Ghas a side surface which is parallel to the optical axis and is not perpendicular to an array direction.

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 along a predetermined direction, and (2) an array arranged along a predetermined direction. A second lens array including _I lenses B _{1 to} B _{I and} having the optical axis of each lens B _{i and} the optical axis of the lens A _i coincide with each other; and (3) the first lens array and the second lens. The light guides G _{1 to} G _I are arranged between the arrays and arranged in a predetermined direction. Each light guide G _i is provided on the optical axis of the lenses A _i and B _i. And a light guide section array. Further, the light guide section G _i is a parallel to the optical axis has a side surface not perpendicular to the predetermined direction, characterized in that. 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 a predetermined straight line on the image plane among the light output from the light source is sequentially applied to the lens A _i , the light guide unit G _i, and the lens B _i . Then, an image is formed on the image plane. On the other hand, light in upper one image plane of the light output from the light source can become a crosstalk is reflected by the side surface of the light guide portion G _i, do not reach the predetermined straight line in the plane.

In the optical imaging system of the present invention, organic light guiding portion G _i is may or may not have a side which is perpendicular to the predetermined direction, the side surface is 45 degrees with respect to a predetermined direction which is parallel to the optical axis It may also be surrounded by a side surface that is parallel to the optical axis and that is 45 degrees with respect to a predetermined direction.

In the imaging optical device of the present invention, the I light guides G _{1 to} G _I may be integrated in a partial section in the optical axis direction and separated from each other in the remaining section. The central axis of the light guide G _i may coincide with the optical axes of the lenses A _i and B _i . Further, when the refractive index of the light guide G _i is n and the light guide arrangement pitch in the light guide array is φ, the length of the light guide G _{i in} the optical axis direction is φ / tan {sin ^−1. (1 / n)} may be longer.

  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 figure which shows the locus | trajectory of the light ray in the imaging optical apparatus 1 of this embodiment. Is a diagram illustrating projections of the XZ plane of the light beam reflected by the optical imaging system 1 of the side surface of the light guide portion G _i of the present embodiment. The optical imaging system 1 of the side surface of the light guide portion G _i of the present embodiment is a view as seen in the Z-direction. It is a figure 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 the other 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.

  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. In each figure, an XYZ orthogonal coordinate system is shown for convenience of explanation.

  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 along the Y direction. 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 along the Y direction. 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 along the Y direction. 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.

  Here, 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 Y axis is parallel to the array arrangement direction in each of the first lens array 10, the second lens array 20, and the light source array 30. The Z axis is parallel to the optical axis.

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 imaged at the predetermined positions P _ji and P _j2 passes through the lens A _i and the lens B _i having a common optical axis. The positions P _ji and P _j2 exist on a predetermined straight line parallel to the Y axis.

However, the light that is not imaged in the range MW on the image plane of the first lens array 10 is on a predetermined straight line passing through the positions P _ji and P _j2 on the image plane P of the second lens array 20, and the position P A position other than _ji and P _j2 is reached and crosstalk occurs. 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. _The light passing through _i is selectively passed to form an image on a predetermined straight line on the image plane P, while the light that may pass through the lens A _i1 and the lens B _i2 having different optical axes is selectively selected. Therefore, the crosstalk is suppressed by not forming an image on a predetermined straight line on the image plane P.

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 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 along the Y direction. 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 .

The light guide G _i has side surfaces that are parallel to the Z direction and not perpendicular to the Y direction. Light reaching the lens A _i in such a side surface of the light guide portion G _i, by being reflected at the side surface, without reaching the predetermined straight line in the image plane P, the crosstalk is suppressed.

The light guide portion G _i is suitably not have a side which is perpendicular to the Y direction. Lens light reaching such a side of the light guide portion G _i from A _i is the cross-talk at a predetermined straight line in the image plane P when it is reflected at the side surface, the light guide portion G _i is such a side By not having it, crosstalk is suppressed.

The light guide G _i is preferably parallel to the Z direction and has a side surface that is 45 degrees with respect to the Y direction. Further, the light guide G _i is parallel to the Z direction. It is preferable to be surrounded by a side surface that is 45 degrees with respect to the Y direction.

FIG. 3 is a diagram showing the locus of light rays in the imaging optical apparatus 1 of the present embodiment. The figure (a) is the figure seen in the X direction, and the figure (b) is the figure seen in the Y direction. In the drawing, the trajectory of light output from the light source S _j among the _J light sources S _{1 to} S _J included in the light source array 30 is indicated by a solid line and a broken line, respectively.

Rays shown by dashed lines, is incident on the incident surface of the light guide portion G _i from the lens A _i, without reaching to the side surface of the light guide portion G _i, emitted from the emission surface of the light guide section G _i to the lens B _i Thus, an image is formed at a desired position P _j on a predetermined straight line (X = 0) on the image plane P. Meanwhile, light rays indicated by the solid line, the lens A _{i + 1} is incident on the incident surface of the light guide portion G _{i + 1} from the, X direction is reflected by the side surface which is parallel to the Z-direction of the light guide G _{i + 1} is not perpendicular to the Y direction The direction is changed, and the light is emitted from the light exit surface of the light guide G _{i + 1} to the lens B _{i + 1} to form an image at a position (X ≠ 0) on the image plane P that is not on a predetermined straight line. The light beam indicated by the solid line is imaged at a position (X ≠ 0) that is not on the predetermined straight line on the image plane P, and thus does not cause crosstalk.

X-axis of the light beam in the light guide portion G _i, Y-axis, and (cosine of the angle between each the beam axis (cos)) direction cosines of the L, M, and N for each Z-axis, of the light guide portion G _i Assuming that the normal vector of the side surface is (l, m, n), the direction cosines of the light beam after being totally reflected by this side surface with respect to the X axis, Y axis, and Z axis are L-2tl and M-2tm, respectively. , N-2tn. Each of L, M, and N is 0 or more and 1 or less. t is represented by the following formula (1).

X-coordinate values of the reflection point of the light beam at the side of the light guide portion G _i, Y coordinate values and Z coordinate values, respectively X _R, Y _R, When Z _R, as shown in FIG. 4, beam after reflection Is projected on the XZ plane by the following linear expression (2), and the angle θ _R with the X axis on the XZ plane is expressed by the following expression (3). Figure 4 is a diagram showing a projection onto the XZ plane side with reflected rays of the imaging optical system 1 of the light guide portion G _i of the present embodiment.

When the side surface of the light guide G _i is parallel to the Z axis, n = 0. In this case, as shown in FIG. 5, if the angle formed between the side surface and the X axis is θ _S , l and m are expressed by the following equation (4). Figure 5 is a diagram of the optical imaging system 1 of the side surface of the light guide portion G _i of the present embodiment as viewed in the Z direction. Using the vector of the side surface of light guide section _{G i} a (l, m, n), (1) is represented by the following formula (5), also the (3) is the following (6) It is expressed by an expression.

On the other hand, the angle of the tangent projection onto the XZ plane in front of the rays of light reflected on the side surface of the light guide portion G _i makes with the Z axis (tan) is L / N. When a ray in the side surface of the light guide portion G _i is not reflected, the light beam, after proceeding in the direction of the left, is refracted by one of the lens included in the rear stage of the second lens array 20, a predetermined in the image plane P It reaches any position on the straight line (X = 0) and crosstalk occurs.

Therefore, the direction of the light beams after being reflected by the side surface of the light guide portion G _i is to the direction of the original ray represented by L / N, is preferably different large as possible. By doing in this way, the light beam after being reflected by the side surface of the light guide G _i reaches a position far from the predetermined straight line (X = 0) on the image plane P, so that crosstalk does not occur. can do. Therefore, the difference between the rays tangent before and after reflection on the side surface of the light guide portion G _i is preferably as large as possible. That is, the absolute value of 2l (lL + mM) / N in the second term on the right side of the above equation (6) is preferably large, and the absolute value of l (lL + mM) is preferably large.

l (lL + mM) is represented by the following formula (7). In order to change the direction of the light beam by reflection on the side surface of the light guide G _i, the side surface must be parallel to the Z direction and not perpendicular to the Y direction, that is, the angle θ _S should not be zero. It is. Further, in order to increase the absolute value of l (lL + mM), considering that the lens has aberration, etc., a light beam having a relatively small L and a large M (that is, a light beam traveling in a direction almost parallel to the YZ plane). It is effective to make the expression (7) larger than Therefore, the inclination each theta _S of the reflective surface of the light guide G _i is preferably 45 degrees.

FIG. 6 is a diagram 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 is an array of _I light guides G _{1 to} G _I each having a rectangular parallelepiped shape. Each of the upper and lower surfaces of the rectangular parallelepiped presented by the light guide G _i is square, the upper surface is a light incident surface from the lens A _i , and the lower surface is a light emission surface to the lens B _i . Four sides of the rectangular parallelepiped exhibited by the light guide portion G _i is 45 degrees to the Y axis which is parallel to the Z axis. It is preferable that a gap is provided between two light guide portions adjacent to each other among the _I light guide portions G _{1 to} G _I , so that crosstalk can be more effectively suppressed.

FIG. 7 is a diagram illustrating another configuration example of the light guide array 40 included in the imaging optical device 1 of the present embodiment. In the light guide array 40 shown in this figure, the I light guides G _{1 to} G _I are integrated in a partial section in the Z direction (section on the first lens array 10 in the previous stage). The remaining section (the section on the second lens array 20 side in the subsequent stage) is separated from each other. The light guide section array 40 having such a configuration can be easily manufactured by molding using two dies in the vertical direction.

FIG. 8 is a diagram showing 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. 9 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.

  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.

The light guide array 40 having the configuration shown in FIG. 7 was used. The I light guide portions G _{1 to} G _I are integrated in a partial section in the Z direction (0.5 mm section on the first lens array 10 side in the front stage), and the remaining section (second stage in the rear stage). In the section of 1.5 mm on the lens array 20 side, they are separated from each other and a gap of 0.01 mm is provided.

_{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. 8 and 9 show light intensity distributions on a predetermined straight line (X = 0) on the image plane P. FIG. Regardless of which of the imaging optical device 1 of the present embodiment and the imaging optical device 2 of the comparative example are used, the images of the light sources S _j1 and S _j2 on the predetermined straight line (X = 0) on the image plane P are used. The interval between the positions P _ji and P _j2 is equal to the interval between the light sources S _j1 and S _j2 and 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. 9, when the imaging optical device 2 of the comparative example is used, the position P _ji , where the light source image should be formed on the predetermined straight line (X = 0) on the image plane P. There is also a light peak at a position 4.5 mm away from P _j2 , which is crosstalk. On the other hand, as shown in FIG. 8, when the imaging optical device 1 of the present embodiment is used, the peak of light that causes crosstalk as in the comparative example is a predetermined straight line (X = 0) Not recognized above.

Incidentally, the refractive index of the light guide G _i is n, the light guide unit arrangement pitch of the light guide unit array 40 When phi, and the light that is incident from the air layer into the light guide portion G _i after passing through the lens A _i The maximum value θ of the angle formed by the optical axis is θ = sin ⁻¹ (1 / n) from Snell's law. To enable the effect of total reflection at 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.

  Further, a slit is disposed in front of the image plane P, and light passing through the slit opening is imaged on a predetermined straight line (X = 0) on the image plane P, while being reflected by the side surface of the light guide portion Gi. The light may be blocked. The width of the slit opening in the X direction is, for example, 0.1 mm.

  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. not provided with a so comprises a light guiding portion array 40 the reflecting surface of the predetermined direction in each of the light guide portion G _i includes an array arranged I-number of the light guide portion G ₁ ~G _I is provided, the lens a 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, selectively advancing direction by the reflecting surface of the optical light guide portion G _i that might be crosstalk Can be changed.

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 (7)

A first lens array including _I lenses A _{1 to} A _I arranged in an array along a predetermined direction;
A second lens array including _I lenses B _{1 to} B _I arranged in an array along the predetermined direction, 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 arranged between the first lens array and the second lens array and arranged in the predetermined direction, and each light guide G _i is a lens. A light guide array provided on the optical axes of A _i and B _i ;
The light guide G _i has a side surface that is parallel to the optical axis and not perpendicular to the predetermined direction.
An imaging optical device (where I is an integer greater than or equal to 2, i is an integer greater than or equal to 1 and less than or equal to I). Light guide section G _i is, no is perpendicular side in the predetermined direction, that optical imaging system of claim 1, wherein the. Light guide section G _i has a side surface which is 45 degrees with respect to the predetermined direction which is parallel to the optical axis, optical imaging system according to claim 1, characterized in that. Light guide section G _i is optical imaging system of claim 1, wherein a parallel to the optical axis is surrounded by the side surface is 45 degrees with respect to the predetermined direction, characterized in that. The imaging optics according to claim 1, wherein the _I light guide parts G _{1 to} G _I are integrated in a partial section in the optical axis direction and separated from each other in the remaining section. apparatus. 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 . The refractive index of the light guide G _i is n, the when and the light guide portion arrangement pitch phi of the light guide unit array, the length of the optical axis of the light guide G _i is φ / tan {sin ^-1 ( The imaging optical device according to claim 1, wherein the imaging optical device is longer than 1 / n)}.

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