JP2002139696A - Illuminator having beam intensity distribution changing optical system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a uniform light intensity distribution in a one-dimensional linear region and high light utilization efficiency, and to avoid entailing significant cost increase for this purpose. SOLUTION: The beam intensity distribution changing optical system G is constituted by an aspheric cylindrical lens L1, arranged on a coherent light source side and an aspheric cylindrical lens L2 existing on its exit side and is arranged with the cylindrical lenses for condensing the rays through this optical system G onto the one-dimensional line. Optical design is made so as to satisfy the relation [X0/R0=Erf(x0/a)/Erf(r0/a)] (where Erf(x/a=(∫exp(-(τ/ a)2)dτ)/(a.√(π))), if Gaussian beam radius of incident parallel beams is defined as 'a', the opening width of the aspheric cylindrical lens L1 as '2.r0', the incident ray height as 'x0', the opening width of the aspheric cylindrical lens L2 as '2.R0' and an exit ray height as 'X0', by which the beam of a one- dimensional top hat shape is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technology for converting a laser beam having a Gaussian distribution into a uniform linear beam shape in an illuminating device having a beam intensity distribution converting optical system.

[0002]

2. Description of the Related Art It is required for various applications to convert irradiation light (laser light or the like) of a Gaussian intensity distribution (light intensity takes a Gaussian distribution) into a uniform beam shape.

FIG. 21 is a graph showing a Gaussian distribution. The upper diagram shows the position coordinate “τ” on the horizontal axis and the intensity “I” on the vertical axis.

That is, when the beam radius is "a",
Gaussian function “exp (− (τ / a) ^Two) "(Function" ex
“p (X)” is an exponential function of the variable X. Min) proportional to
It is represented by a cloth function. In addition, as shown in the lower diagram,
In (τ → x, y), “exp (− (x / a)^Two− (Y
/ A)^Two) = Exp (− (x / a)^Two) .Exp (-(y
/ A)^Two) ".

FIG. 22 is a graph showing a so-called “top hat” or “flat top” distribution having a uniform intensity distribution in a desired region. The position coordinate “τ” is taken, and the vertical axis represents the intensity “I” (one-dimensional top hat shape).

That is, the rectangular area "-.tau..ltoreq..tau..ltoreq..tau.0" in FIG.
Shows a constant strength. In the two dimensions, a rectangular distribution is obtained by rotating a rectangular area around its center line (I axis in the figure) (shown in the lower diagram).

The purpose of converting the Gaussian intensity distribution into the top hat distribution in this way is as follows.

(1) To convert the intensity distribution on the pupil plane to narrow the beam diameter of the spot on the Fourier plane or to improve the imaging characteristics (apodization) (2) Uniform intensity distribution And use this as illumination light.

Note that item (1) is important for application to optical discs and the like (optical pickup devices and the like), and various reports have been made so far, but the results to be seen very little Not raised. The reason is that although there is no effect of narrowing the spot diameter so much, the side band increases, and the off-axis coma aberration causes the loss of tolerance, which is of little practical value.

Regarding (2), uniform illumination is required in an image processing apparatus, an exposure apparatus, and the like.

For example, a liquid crystal display panel or a DMD (Digita
In a projection display using (i.e., Mirror Device) or the like, an illumination optical system using a microlens array or the like is employed to correct the luminance distribution of the lamp. This uses the same principle as a fly-eye lens used in an excimer laser stepper, which spatially splits the incident light beam from the light source and converts the partial light beams of the split details all on the projection surface. The superimposition means that the non-uniformity of each portion is averaged and corrected (the intensity distribution of the illumination light approaches a uniform top hat in a rectangular area).

[0012]

However, there is a problem that the above method cannot be applied as it is to an illumination optical system using a coherent laser beam as a light source. This is because when the spatial coherence of the beam is high, interference fringes are generated when the parts of the beam overlap, and the illumination light is rather non-uniform. Therefore, direct conversion of the beam intensity distribution without using the superposition principle is required.

The following method can be considered.

(A) Method using beam profile conversion using an aspherical lens (b) Method using a diffractive optical element

First, as for (a), two aspherical lenses are combined to spread the light beam at the center of the Gaussian beam having a high light density and to narrow the light beam at the peripheral portion (foot portion) having a low light density. The use of an optical system is based on the viewpoint that a beam profile can be made uniform. By changing the local emission magnification in the vicinity of each light beam, the power flow of the light is made uniform. It is an idea.

However, this method still has problems such as complicated design and difficulty in complicated aspherical surface processing, and has not been widely used at present.
Further, in research in this field, illumination in a two-dimensional area is a main concern, and there has not been enough studies on making illumination light uniform on a one-dimensional line.

The above method (b) is a method of realizing such a complicated optical element as a diffractive element by paying attention to the recent progress of the diffractive optical element. Considering the problem of interference with scattered light, diffraction efficiency, etc., it does not always provide a practical solution in all cases.

By the way, a display using an active driving grating by a micromachine technology has been developed and attracted attention (a diffraction grating element called a grating light valve element is used, and this is hereinafter referred to as a "GLV element"). Compared to conventional spatial modulators, it has features such as being able to display a seamless (seamless) clear and bright image, being able to be created at low cost, and being capable of high-speed operation (for example, US Pat. No. 5,311,360, May 10, 1994, "Method and Apparatus fo
r Modulating a Light Beam ", Stanford.) For the lighting required for a one-dimensional GLV element, see
There is a demand for how to make the light uniform in the line area and to increase the light use efficiency, and there is a background that effective lighting means for that purpose is being sought.

An object of the present invention is to provide an illumination optical system capable of obtaining a uniform intensity distribution and a high light use efficiency in a one-dimensional line area, and to prevent a remarkable increase in cost for the purpose. I do.

[0020]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention has the following arrangement.

A beam intensity distribution conversion optical system including a first aspherical cylindrical lens disposed on the side of the coherent light source and a second aspherical cylindrical lens located on the exit side thereof;

A cylindrical lens for condensing a light beam having passed through the beam intensity distribution conversion optical system onto a one-dimensional line;

The radius of the Gaussian beam of the incident parallel beam is "a", the opening width of the first aspherical cylindrical lens is "2.r0", the height of the incident light beam is "x0", and the opening of the second aspherical cylindrical lens is Assuming that the width is “2 · R0” and the height of the emitted light beam is “X0”, the following relational expression is satisfied for almost all incident light beams in the beam intensity distribution conversion optical system.

"X0 / R0 = Erf (x0 / a) /
Erf (r0 / a)] where Erf (x) is an error function, and “Erf (x / a)
a) = (∫exp (− (τ / a) ² ) dτ) / (a · √)
(Π)) ”. The integration area is “−x ≦ τ ≦ x”.

Therefore, according to the present invention, a Gaussian is obtained by combining a pair of two aspherical cylindrical lenses and a cylindrical lens on the exit side thereof and performing optical design based on the above relational expression. It is possible to obtain an illumination area having a uniform intensity on a one-dimensional line by using the light of the distribution, and it can be realized with a simple configuration.

[0026]

1 to 4 are diagrams used for explaining the principle according to the present invention.

The beam intensity distribution conversion optical system according to the present invention has a configuration in which two aspherical cylindrical lenses are combined. This means that even if a rotationally symmetric spherical or aspherical surface is used for the lens surface, in consideration of rotational symmetry around the optical axis, it is necessary to pay the price of blocking some of the beam and losing the amount of light. This is because it is not possible to uniformly illuminate a one-dimensional linear illumination area. That is, in order to make uniform one-dimensional linear illumination without loss of light quantity, it is essential to use a cylindrical lens or the like as a rotationally asymmetric optical element.

In FIG. 1, "L1" is a first lens,
“L2” indicates the second lens, and these are arranged along the z-axis (optical axis). In this example, the power of the first lens L1 is negative and the power of the second lens L2 is positive in the upper diagram (yz diagram).
The three-dimensional orthogonal coordinate system includes a z-axis and an x-axis and a y-axis set in a plane orthogonal to the z-axis. For example, each axis is defined by an axis extending along a direction as illustrated. Is defined.

When these lenses are paired to form a beam intensity distribution conversion optical system G, position coordinates x, y
Is the two variables, the distribution function of the incident light (to the optical system) is “σ (x, y)”, and the distribution function of the outgoing light is “Σ (x, y)”.
y) ", the relationship shown in the following equation is established with the light amount loss set to zero.

I _total = ∫∫σ (x, y) dxdy = ∫∫Σ (x, y) dxdy− (1) Here, the aperture (aperture) of the first lens L1 is “2x0 × 2y0”. And the aperture (opening) of the second lens L2 is a rectangular shape of “2X0 × 2Y0”. The double integral shown in the first expression on the right side of the above expression, “∫∫σ (x,
y) dxdy ”, the integration area is defined as“ −x0 ≦ x ≦ x
0 ”,“ −y0 ≦ y ≦ y0 ”, and 2
Regarding the multiple integration, "∫∫Σ (x, y) dxdy", the integration areas are "-X0≤x≤X0" and "-Y0≤y≤Y0".

When the intensity distribution of light incident from the coherent light source on this optical system is a Gaussian distribution, the Gaussian beam radius of the incident parallel beam (light intensity is 1 / (e ² of the maximum intensity at the center) (E) indicates the base of the natural logarithm.) When “a” is used,
The result calculated for the first expression on the right side of the expression (1) is as follows.

I_total = (∫exp (-x^Two/ A^Two) Dx) · (∫exp (-y^Two/ A ^Two ) Dy) = π · a^Two-Erf (x0 / a) -Erf (y0 / a)-(2) where the function "Erf (x)" shown in the above equation is an error function (A
Or Err (x / a) = (∫
exp (−τ^Two/ A^Two) Dτ) / (a · √ (π)) ”
Thus, the integration area is “−x ≦ τ ≦ x”.

With respect to the intensity distribution when such a two-dimensional Gaussian distribution beam is condensed on a one-dimensional figure, if the influence of diffraction is neglected, the light amount is simply obtained as one-dimensional integration. Well, it becomes like the following formula.

I_1D(X0) = ∫exp (-((x0)^Two
+ Y^Two) / A^Two) Dy In addition, "1D" means one dimension, and the integral area of the variable y is
"-√ (r^Two− (X0) ^Two) ≦ y ≦ √ (r^Two− (X0)^Two) "
And "(x0)^Two+ (Y0)^Two= R^Two".

FIG. 2 shows an example of numerical calculation, in which the horizontal axis represents position coordinates "x0" (the domain is normalized and shown in the range of "-1≤x≤1"), and the vertical axis represents the values. The light intensity is shown as a relative value (a constant level of the top hat is "1").

The distribution indicated by the rectangle N indicates the target top hat, and as can be seen from the comparison with the graph line g, the intensity is too high in the central region and insufficient in the peripheral region. . In the actual distribution, the influence of diffraction must be further considered, so that the light converging width is narrower at the center, and the difference in the intensity distribution between the central region and the peripheral region is further increased.

As described above, a Gaussian distribution type incident beam is simply obtained by using an aspherical cylindrical lens.
It can be seen that the intensity distribution when condensed on a line is not uniform if the light is converted into dimensional output light.

Then, under the condition that there is no vignetting and the effect of diffraction is neglected, in order to convert the beam shape of the Gaussian distribution into the distribution shape of the top hat,
Each of the first and second lenses constitutes a beam intensity distribution conversion optical system as an aspherical cylindrical lens, and a cylindrical lens or lens for condensing a light beam passing through the beam intensity distribution conversion optical system on a one-dimensional line. A group (not shown) is arranged.

FIG. 3 schematically shows a configuration example in which the first lens L1 (first aspherical cylindrical lens) is a plano-concave lens and the second lens L2 (second aspherical cylindrical lens) is a plano-convex lens. The meaning of each symbol is as shown below.

"2.r0" = aperture width of the first lens "x0" = incident ray height of the first lens "(r, z)" = position coordinates on the exit surface of the first lens "n1" = Refractive index of the first lens • “t” = thickness at the center of the first lens • “n0” = refractive index between lenses (1 in air) • “2 · R0” = opening width of the second lens • “X0” = Height of the outgoing light ray of the second lens-"(R, Z)" = position coordinates on the incident surface of the second lens-"(0, Z0)" = vertex position coordinates of the second lens-"n2" = second lens "T" = thickness of the center of the second lens In the three-dimensional orthogonal coordinate system, the Z (or z) axis is set as the optical axis, and the X (or x) axis orthogonal to this is set. An axis orthogonal to both axes and extending perpendicular to the plane of the drawing is defined as a Y (or y) axis (not shown). Have the same cross-sectional shape along the direction of the axis.). When it is necessary to distinguish the coordinates of the first lens and the second lens, small letters x, y, and z are used for the first lens L1, and capital letters X, Y, and Z are used for the second lens L2. I will.

In such an optical system, the amount of light transmitted through an area (see the hatched portion in the figure) indicated by the range of “0 ≦ x ≦ x0” on the concave surface (second surface) of the first lens is calculated. Then, it becomes as follows.

I (x 0) = ∫∫exp (− (x ² + y ² ) / a ² ) dxdy = ((π · a ² ) / 2) · Erf (x 0 / a) · Erf (y 0 / a) − (3a) Expression In the above expression, the integral range of the variable x is “0 ≦ x ≦ x0”.
And the integral range of the variable y is “−y0 ≦ y ≦ y0” (that is, the width in the y-axis direction is “2 · y0”).

All the light amounts represented by the equation (3a) are incident on the second lens L2 without loss, and "0≤X≤X0"
And the distribution function of the second lens is represented by “Σ (X, Y)”.
Then, the following equation is obtained.

I (x 0) = ∫ ｛∫Σ (X, Y) dY｝ dX− (3b) In the above equation, the integral range of the variable X is “0 ≦ X ≦ X 0”
And the integral range of the variable Y is “−Y0 ≦ Y ≦ Y0” (that is, the width in the Y-axis direction is “2 · Y0”).

In order to obtain the distribution of the top hat when the emitted light passing through the second lens L2 is subsequently converged on a line, the integral within ｛｝ in the above equation (3b) (integration with respect to the variable Y) Must be a constant (referred to as “Σc”). That is, it is necessary to impose the following condition.

∫Σ (X, Y) dY = Σc (constant) − (4) Note that the integral range of the variable Y is “−Y0 ≦ Y ≦ Y0”.

The aperture on the incident side of the first lens is “−r0 ≦ x ≦ r0”, “−r0 ≦ y ≦ r0”,
When the aperture on the emission side of the second lens is “−R0 ≦
If X ≦ R0 ”and“ −R0 ≦ Y ≦ R0 ”, assuming that there is no light amount loss, the total light amount of the lens system“ I _total ”
The following expression holds for.

I _total = 2 · I (r0) = 2 · R0 · Σc− (5) From this, “Σc” can be obtained, and is as follows.

Σc = ((π · a ² ) / (2 · R 0)) · Erf (r 0 / a) · Erf (y 0 / a) − (6) Accordingly, the half value “R 0” of the aperture of the second lens is obtained. The following result is obtained when the ratio of the height of the emitted light beam “X0” to the ratio is obtained.

X0 / R0 = Erf (x0 / a) / Erf (r0 / a) −Equation (7) This equation is obtained by substituting equation (4) into equation (3b) and integrating “X0 · Σc”. Can be easily confirmed from equation (6) that equation (3a) is equal to equation (3a) with some equation modifications.

As described above, in order to obtain a top hat when a two-dimensional Gaussian distribution beam is condensed on a one-dimensional line, in the beam intensity distribution conversion optical system, equation (7) is used. Must be satisfied for almost all incident rays.

In an actual image forming optical system, a so-called cosine (4th power) law must be considered for the brightness of an off-axis image. Here, a laser beam having a strong directivity is mainly used as a light source. Note that we assume this. Also,
Since the surface of the projection plane is not a Lambertian plane (perfectly diffusing surface) but a mirror surface, the cosine fourth law cannot be applied in this case. Therefore, it is not necessary to include the cosine fourth law in the design in consideration of these circumstances, but when the influence of vignetting of the projection lens is significant, the correction conditions for these conditions are discussed above. What is necessary is just to do the design which included.

In the above example, the configuration in which the beam diameter of the laser beam is expanded (expansion system) has been described. However, the present invention is not limited to this, and the present invention may be applied to an equal magnification system or a reduction system. Even in this case, if the relationship of equation (7) is satisfied,
It is possible to obtain uniform illumination light in a one-dimensional line area by the cylindrical lens.

In order to cope with time-dependent changes in the beam diameter of the laser beam and individual differences in the laser light emitting element, etc., if necessary, an optical component for correction should be provided on the entrance side of the beam intensity distribution conversion optical system. Is also effective.

For example, in the example shown in FIG. 4, the beam diameter adjusting means is constituted by using an optical system in which an anamorphic prism P and a parallel flat plate H (for beam height correction) are combined. Regarding the two optical components P and H, the posture of each component is freely controlled in a plane including the optical axis (a plane including the paper surface) by a rotating mechanism (not shown) as shown by arrows A and B in FIG. (The tilt angle with respect to the optical axis can be arbitrarily set by changing the respective postures.)

The illumination device according to the present invention can be widely used for optical devices for various uses including a display device such as a laser display. For example, in a laser display using the above-described GLV element, the brightness of an image can be made uniform by controlling the diffraction efficiency of each pixel in the device by using a voltage. The light above is thrown away. Therefore, if the intensity of the illumination light is not uniform, light use efficiency is sacrificed. That is, when the light use efficiency is low, it is necessary to increase the output of the laser to achieve the target brightness, and thus problems such as a burden on the laser, an increase in cost and power consumption occur. Therefore, it is preferable that the illumination light is as uniform as possible, and in that sense, the application of the present invention is suitable.

[0057]

5 to 12 are views for explaining a first embodiment according to the present invention.

FIGS. 5 to 7 show optical path diagrams. FIG. 5 shows the overall arrangement of the optical system and optical paths (ray tracing results), and FIG. 6 is a plan view seen from the x- and X-axis directions. 7 shows a side view (showing the arrangement on the XZ plane) as viewed from the y- and Y-axis directions. Note that, similarly to FIG. 3, regarding the setting of the three-dimensional orthogonal coordinate system, the Z axis (z axis) is defined as the optical axis, and two axes orthogonal to this are defined as the X axis (x axis) and Y (y axis), respectively. In this case, the first lens and the second lens are distinguished by using lowercase letters and uppercase letters.

In these figures, the first lens L1 is a plano-concave lens, and the second lens L2 is a plano-convex lens. These form a pair and constitute a beam intensity distribution conversion optical system. It is an aspheric cylindrical lens (shapes along the x and X axis directions have the same cross-sectional shape).

The third lens L3 is a plano-convex lens, and is a cylindrical cylindrical lens having the same cross-sectional shape along the y- and Y-axis directions.

In FIG. 5, the three-dimensional shape is represented as a wire frame by connecting the contours of the lenses to the edges.

This optical system (line generator) is Rh
It is designed to satisfy the relationship of the above equation (7) based on a design method by Odes and the like, and the specifications of the first lens and the second lens are shown as follows in a table format.

[0063]

[Table 1]

The materials for the refractive indices n1 and n2 are shown in parentheses. The thickness T value of the second lens L2 is not particularly limited (∵it is not refracted at the exit surface of the second lens because it is perpendicularly incident).
mm.

The table below summarizes the design data.

[0066]

[Table 2]

The surface numbers are sequentially numbered from 1 to 6 from the object side to the image side.
The curvature of the (convex surface of the third lens) is defined in a plane orthogonal to the respective curvatures of the first lens and the second lens.

The concave surface of the first lens (the second surface, which is described as "S2") and the convex surface of the second lens (the third surface, which is described as "S3"), are aspherical toroidal. "C = k = 0" in the aspherical expression shown below.
(“C” is the curvature, “1 + k” is the cone coefficient.) (In the following equation, x, y, z coordinates and X, Y, Z
The coordinates are expressed collectively without being distinguished by the lens. ).

Z = (c · y ² ) / (1 + √ (1- (1+
^{k) · c 2 · y 2} )) + α1 · y 2 + α2 · y 4 + α3 · y 6 +
^{α4 · y 8 + α5 · y} 10 + α6 · y 12 Note that "αi" (i = 1 to 6) are aspherical coefficients of even order, "2 · i" indicates the order.

An example of the design data is shown in the table below.

[0071]

[Table 3]

In this case, “e” in the above table is not the base of the natural logarithm, but “eX = 10 ＾ X” (“X” is an exponent,
“＾” indicates a power. ) Is a real exponential notation.

As described above, regarding the first and second lenses,
One surface shape is defined as a flat surface (zero curvature), and the other surface shape is defined by a polynomial of a predetermined order in which the curvature is zero in the aspherical expression.

FIGS. 8 to 12 show the characteristics and the like of the optical system.

FIG. 8 shows the sag of the surfaces S2 and S3, in which the abscissa represents the z coordinate and the ordinate represents the aforementioned "r" (the position on the surface, that is, the distance from the origin). .

FIG. 9 shows the results of ray tracing.
The horizontal axis represents the z coordinate, and the vertical axis represents “r”.

FIG. 10 shows the profile of the incident beam. The horizontal axis represents "y", and the vertical axis represents the relative value of the light intensity "I" (the peak value at the center of the incident beam is "1"). Is taken.

The graph curve "IB" in the figure shows the intensity distribution (Gaussian distribution) of the incident beam, and the graph curve "IB"
"T" indicates an integrated value along the x and X axes.

FIG. 11 shows a profile of the intensity distribution of light condensed on a one-dimensional straight line, in which “Y” is plotted on the horizontal axis and the relative value of light intensity “I” is plotted on the vertical axis. It is a thing.

A rectangle "DT" shown by a broken line in the drawing indicates a distribution that is a target value (ideal value) of the top hat, and a graph curve "GE" indicates an actual distribution. The area indicated by the solid-line rectangle "CL" located within the graph curve "GE" is, for example, a completely uniform area which is taken out after being calibrated for application to a laser display device or the like using a GLV element. It shows a strong intensity distribution.

In this figure, the geometrical optical beam expansion rate in the vicinity of the sampled light ray is obtained for the area within the rectangle "DT", and the beam profile is calculated based on this. Then, for this beam profile, the slice level of the calibration that maximizes the light use efficiency is indicated by a rectangle “CL”. In this design, the calibration slice level is 92.7%, and the light use efficiency after calibration is 8%.
2.3%. In practice, you can expect a few percent margin for calibration,
For example, if the slice level is about 96%, 90%
The above light utilization efficiency can be achieved. However, since the amount of light is reduced in the peripheral area, it is preferable to design the target with a range slightly wider than the actual illumination area.

FIG. 12 shows the integrated energy “EE (“ Encircled Energy ”)” (relative value) obtained on the y-axis at the light-converging surface by the optical system including the first to third lenses. The horizontal axis represents the distance from the origin (center of the lens) (the distance from the optical axis), and the vertical axis represents y = y0 from the origin.
The relative value of the amount of light contained in the region up to is taken ("1" at y = y0).

In the case of perfect uniform light, the intensity is constant in the range of y = 0 to y0. Therefore, the integral value is expected to have a relationship proportional to the y-axis coordinate value. An almost proportional linear relationship is observed.

FIGS. 13 to 20 are views for explaining the second embodiment according to the present invention.

FIGS. 13 to 15 show optical path diagrams. FIG. 13 shows the overall arrangement of the optical system and the optical path (ray tracing result), and FIG. 14 is a plan view viewed from the x- and X-axis directions. Y
-Shows the arrangement on the Z plane. ) And FIG. 15 show side views (showing the arrangement on the XZ plane) as viewed from the y and Y axis directions, respectively. The setting of the three-dimensional orthogonal coordinate system is the same as that of the first embodiment.

The optical system according to this embodiment has five lenses L
The first lens L1 is a plano-concave lens, the second lens L2 is a plano-convex lens, and these form a pair to constitute a beam intensity distribution conversion optical system. Both lenses are aspherical cylindrical lenses (shapes along the x-axis and the X-axis have the same cross-sectional shape).

The third lens L3 is a plano-concave lens, and is a cylindrical lens having the same cross-sectional shape along the x and X axis directions and having a cylindrical surface with a constant curvature.

The fourth lens L4 is a plano-convex lens.
This is a cylindrical lens having a cylindrical surface having a constant curvature and having the same cross-sectional shape along the X-axis direction.

The fifth lens L5 is a plano-convex lens.
This is a cylindrical lens having a cylindrical surface having a constant curvature and having the same cross-sectional shape along the Y-axis direction.

In FIG. 13, in addition to the three-dimensional representation of the outline of each lens as a wire frame by connecting the edges, a supplementary line such as a center line is added. It is put as.

In this embodiment, the beam intensity distribution is converted by two aspherical cylindrical lenses, and then the beam is expanded by a beam expander with three spherical (more precisely, cylindrical) cylindrical lenses. .

Tables 4 and 5 show examples of the design data.

[0093]

[Table 4]

The numbers in parentheses for the materials of each lens indicate the respective refractive indexes, and the refractive index of air is "1" in other gaps. The surface numbers are sequentially numbered from 1 to 10 from the object side to the image side, and the curvature of the surface number 9 (the convex surface of the fifth lens) is the concave or convex surface of the first to fourth lenses. Are defined in planes orthogonal to each other.

The curvature of the second surface and the third surface is set to zero in the above-mentioned aspherical surface equation, and the respective aspherical surface coefficients are as shown in the following table.

[0096]

[Table 5]

Note that notational notes regarding "e" in the above table are as described in Table 3. The first to fourth surfaces were designed as rectangular openings of 12 × 12 (mm).

FIGS. 16 to 19 correspond to FIGS. 8 to 11 according to the first embodiment, respectively. FIG. 16 shows the sag of the second surface S2 and the third surface S3, and FIG. Shows tracking results. FIG. 18 shows the profile of the incident beam, and FIG. 19 shows the profile of the light intensity distribution on a one-dimensional straight line (the vicinity of the boundary is enlarged and shown in a large circle). Are as described above.

FIG. 20 shows the integrated value (light amount) of the light intensity distribution on the light condensing surface as a relative value (the total amount is “1”). In the left figure, the horizontal axis shows the coordinates in the tangential direction, and the light quantity integrated along the axis is shown on the vertical axis. In the figure on the right, the coordinates in the sagittal direction are taken, and the light quantity integrated along the axis is shown on the vertical axis.

As can be seen from the right figure, the graph line shows a substantially linear relationship, and therefore, the intensity distribution is uniform (the gradient of the graph line is almost constant, and the intensity distribution, which is a derivative thereof, is It is almost constant.)

According to each of the above-described embodiments, the light intensity distribution can be made uniform when the light is focused on the one-dimensional linear illumination area after the profile conversion is performed on the Gaussian distribution type incident beam. In addition, the light use efficiency can be improved. Therefore, the output of the laser required to obtain a desired light amount can be reduced, which is effective for power saving and cost reduction of the entire system.

[0102]

As is apparent from the above description, according to the first aspect of the present invention, a pair of two aspherical cylindrical lenses and a cylindrical lens on the exit side thereof are combined, and By performing an optical design based on a relational expression for obtaining a one-dimensional top hat distribution, a uniform illumination area can be obtained on a one-dimensional line using a Gaussian distribution light beam, and the light use efficiency can be improved. Can be enhanced. In addition, the configuration of the optical system is not significantly complicated.

According to the second aspect of the present invention, a beam expanding system can be configured with a relatively simple configuration without using a complicated diffractive optical element or the like.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining the principle of the present invention.

FIG. 2 is a graph showing a one-dimensional projection intensity distribution of a two-dimensional Gaussian distribution.

FIG. 3 is an explanatory diagram of an arrangement of a first lens and a second lens.

FIG. 4 is a diagram illustrating an example of an optical system for beam correction.

FIG. 5 is a diagram for explaining the first embodiment according to the present invention, together with FIGS. 6 to 12, and is a perspective view showing a spatial arrangement of an optical system.

FIG. 6 is a diagram of the optical system viewed from a direction (x, X-axis direction) orthogonal to the optical axis.

FIG. 7 is a diagram of the optical system viewed from a direction (y, Y-axis direction) orthogonal to the optical axis.

FIG. 8 is a diagram showing a surface shape.

FIG. 9 is a diagram showing a ray tracing result.

FIG. 10 shows a profile of an incident beam.

FIG. 11 shows a profile of a light intensity distribution.

FIG. 12 shows an integrated energy amount (light amount) obtained on the y-axis at the light-collecting surface.

FIG. 13 is a diagram for explaining the second embodiment according to the present invention, together with FIGS. 14 to 20, which is a perspective view showing a spatial arrangement of an optical system.

FIG. 14 shows an optical system in a direction (x, X,
FIG.

FIG. 15 shows an optical system in a direction (y, Y) orthogonal to its optical axis.
FIG.

FIG. 16 is a diagram showing a surface shape.

FIG. 17 is a diagram showing a ray tracing result.

FIG. 18 shows a profile of an incident beam.

FIG. 19 shows a profile of a light intensity distribution.

FIG. 20 shows an integrated value (light amount) of a light intensity distribution along a predetermined axis direction on a light-collecting surface.

FIG. 21 is an explanatory diagram schematically showing a Gaussian distribution.

FIG. 22 is an explanatory diagram schematically showing a uniform intensity distribution.

[Explanation of symbols]

G: beam intensity distribution conversion optical system, L1: first aspheric cylindrical lens, L2: second aspheric cylindrical lens, L3: third cylindrical lens

Claims (2)

[Claims] 1. A beam intensity distribution converting optical system including a first aspherical cylindrical lens disposed on the side of a coherent light source and a second aspherical cylindrical lens positioned on an exit side thereof, and the beam intensity distribution converting optical system includes: An illumination device having a beam intensity distribution conversion optical system having a third cylindrical lens or lens group for condensing the transmitted light rays on a one-dimensional line, wherein a Gaussian beam radius of an incident parallel beam is “a”. ,
The aperture width of the first aspherical cylindrical lens is “2 · r0”, the incident light height is “x0”, and the aperture width of the second aspherical cylindrical lens is “2 · R”.
"0" and the height of the emitted light is "X0", the following relational expression:
a) "(where Erf (x) is an error function, ie, Er
f (x / a) = (∫exp (− (τ / a) ² ) dτ) /
(A · √ (π)), and the integral range of the variable τ is “−x ≦ τ
≦ x ”. ) Wherein the beam intensity distribution conversion optical system is satisfied with almost all incident light beams. 2. An illumination device comprising the beam intensity distribution conversion optical system according to claim 1, wherein the first aspherical cylindrical lens is a plano-concave lens,
An illumination device provided with a beam intensity distribution conversion optical system, wherein the second aspheric cylindrical lens is a plano-convex lens.