JP2014010428A - Line illumination apparatus - Google Patents

Abstract

A line illumination device capable of increasing brightness and incident efficiency is provided.
A plurality of sets each including a light emitting diode and a numerical aperture conversion lens are provided. Each numerical aperture conversion lens 12 has a positive refractive power, and is arranged at an interval shorter than the focal length from the light emitting diode 11 so as to reduce the numerical aperture of the light emitted from the light emitting diode 11. Each set of the light emitting diode 11 and the numerical aperture conversion lens 12 is arranged in a straight line, and is provided so that light from each light emitting diode 11 can be emitted in the same direction perpendicular to the arrangement direction. . The cylindrical lens 13 has a positive refractive power only in one direction, and light emitted from each light emitting diode 11 that has passed through each numerical aperture conversion lens 12 is collected in a straight line parallel to the array direction of each set. Arranged to be illuminated.
[Selection] Figure 1

Description

  The present invention relates to a line lighting device.

  A line camera used in a planar defect inspection apparatus, an image reading apparatus, or the like has a higher resolution than a two-dimensional camera, and can obtain a high-resolution two-dimensional image in combination with a system that moves a subject or an imaging system. . Such a line camera is generally equipped with a line illumination device for illuminating a subject during photographing. For example, in the case of a liquid crystal glass defect inspection apparatus, the imaging range of the line camera is a very long and narrow area of about 1 × 300 mm, and therefore the line illumination apparatus only needs to illuminate a range of about 5 × 300 mm.

  In recent years, line cameras have been improved in resolution and reading speed, and a brighter and more efficient line illumination device is required as a corresponding line illumination device. Accordingly, line illuminators using LEDs (light emitting diodes) have been developed as a means to meet such demands.

  As a line illumination device using LEDs, for example, a small LED chip is arranged in a concave reflecting mirror, a bullet-type LED integrally formed with an acrylic mold lens is arranged on a straight line, and this output light is condensed by a cylindrical lens. A light source substrate that is linearly arranged and bonded to a substrate such as a ceramic (such as Patent Document 1) or ceramic, and is molded with a cover glass or hemispherical silicone, and is linearly formed on the light source substrate There exists what collects the output light of arranged LED with a rod lens or a plano-convex cylindrical lens (for example, refer to patent documents 2 or 3).

Except for the bullet-type LED, the emission pattern of the chip LED light has a Lambertian distribution. When the numerical aperture of the optical system in which the LED light is incident is NAin, the efficiency ηin in which the LED light is incident on the optical system is a value obtained by integrating the Lambertian distribution up to an angle with respect to the incident numerical aperture.
ηin = sin ² θ = NAin ²
It becomes. FIG. 7 shows a graph of the luminous intensity and incident efficiency of the LED output light with respect to the angle θ formed by the normal line of the LED and the emitted light. As shown in FIG. 7, when NAin = 1, the incident efficiency is 100%, and the closer to this, the higher the efficiency.

JP 2004-101311 A JP 2009-288206 A JP 2001-215115 A

  In the line illumination device described in Patent Document 1, light emitted from the bullet-type LED in the normal direction in front of the LED chip is directly deflected by the lens and emitted forward, but has a certain angle from the normal direction. The light emitted from the side of the chip and the light emitted from the side surface of the chip are reflected by the lens after being reflected by the reflecting mirror on the side surface of the LED chip, and are then deflected by the lens. There is a problem that it is difficult to increase the brightness and incidence efficiency.

  Further, in the line illumination device using the rod lens described in Patent Document 2, since the numerical aperture of the rod lens is about 0.5, the incident efficiency is about 25% from FIG. there were.

  In addition, an optical system consisting only of a cylindrical lens having a refractive power only in one direction, such as a rod lens and a plano-convex cylindrical lens described in Patent Documents 2 and 3, has a problem in condensing light as shown below. is there. That is, taking a rod lens as an example, as shown in FIG. 8, the rod lens 52 has a positive refractive power in the Y direction and does not have a refractive power in the X direction. The light is collected on a straight line in the X direction. However, as shown in FIGS. 8 and 9, when comparing the light beam A emitted on the YZ plane with the light beam B emitted on a plane having an angle of 30 degrees with the YZ plane, the light beam B has a light emitting point 51. Since the distance from the lens 52 to the rod lens 52 is longer than that of the light beam A, the curvature of the lens is smaller than that of the light beam A, and the length passing through the lens is longer than the light beam A, the light is condensed before the light beam A. Surface curvature occurs. As described above, when the numerical aperture NA of the light incident on the cylindrical lens is increased, field curvature occurs, and there is a problem in that aberration due to the field curvature increases and illuminance decreases.

  The present invention has been made paying attention to such a problem, and an object of the present invention is to provide a line illumination device capable of increasing brightness and incident efficiency.

  In order to achieve the above object, a line illuminating device according to the present invention has a light emitting diode and a positive refractive power, and has a focal length from the light emitting diode so as to reduce the numerical aperture of light emitted from the light emitting diode. A numerical aperture conversion lens arranged at a short interval and a positive refractive power only in one direction, and arranged so that light emitted from the light emitting diode that has passed through the numerical aperture conversion lens is condensed linearly. And a cylindrical lens.

  In the line illumination device according to the present invention, the numerical aperture conversion lens having a positive refractive power is arranged at an interval shorter than the focal length from the light emitting diode so as to reduce the numerical aperture NA of the light emitted from the light emitting diode. Since the light emitted from the light-emitting diode that has passed through the numerical aperture conversion lens is configured to enter the cylindrical lens, it is possible to suppress the occurrence of field curvature. For this reason, aberration can be reduced and illuminance can be increased. Moreover, the linearity of the light condensed by the cylindrical lens can be improved. The exit numerical aperture of the numerical aperture conversion lens is preferably 0.3 or less so as to keep the curvature of field aberration of the cylindrical lens low.

  The line illuminating device according to the present invention can increase the incident efficiency by setting the incident numerical aperture of the numerical aperture conversion lens to be high. In the line illumination device according to the present invention, if the cylindrical lens can condense light emitted from the light emitting diode that has passed through the numerical aperture conversion lens in a straight line, for example, a rod lens, a plano-convex cylindrical lens, a cylindrical Fresnel lens, etc. Anything can be used.

  The line illumination device according to the present invention includes a plurality of sets of the light emitting diodes and the numerical aperture conversion lens, and each set is linearly arranged, and each light emitting diode is directed in the same direction perpendicular to the arrangement direction. The cylindrical lens is arranged so that the emitted light from each light emitting diode that has passed through each numerical aperture conversion lens is condensed in a straight line parallel to the arrangement direction. It is preferable. In this case, the condensed linear light can be lengthened. Further, the brightness and length of the collected linear light can be adjusted by the number of the light emitting diodes arranged in a straight line and the numerical aperture conversion lens, and the distance between the sets. In addition, it is preferable that the irradiation width of the arrangement direction of one light emitting diode is 2 to 4 times the light emitting diode arrangement interval. This is because if the light emitting diode arrangement interval is narrow, the uniformity of the light in the arrangement direction is reduced, and if the light emitting diode arrangement interval is too long, the irradiation end in the arrangement direction is irradiated outside the irradiation range, resulting in poor efficiency. Because.

  Further, in this case, each set is arranged in a plurality of lines that are parallel to each other, and the cylindrical lens has light emitted from each light emitting diode that has passed through each numerical aperture conversion lens parallel to the arrangement direction. You may arrange | position so that it may concentrate on a linear strip | belt-shaped area | region. In this case, the brightness and width of the straight strip-shaped region to be collected can be adjusted by the number of rows and the spacing between the rows of the combination of the light emitting diode and the numerical aperture conversion lens.

  ADVANTAGE OF THE INVENTION According to this invention, the line illuminating device which can improve brightness and incident efficiency can be provided.

It is a perspective view which shows the line illuminating device of the 1st Embodiment of this invention. (A) Ray tracing side view of the line illuminating device shown in FIG. 1, (b) Ray tracing side view of a conventional cylindrical lens only illuminating device. (A) Spot diagram of light emitted from one light emitting diode of the line lighting device shown in FIG. 2 (a), (b) From one light emitting diode of the conventional lighting device shown in FIG. 2 (b) It is a spot diagram of the emitted light. 2A is a graph showing the illuminance distribution in the Y direction when the light emitting diodes are arranged infinitely in a straight line in the line illumination device shown in FIG. 2A; FIG. 2B is a conventional illumination device shown in FIG. It is a graph which shows the illuminance distribution of a Y direction when the light emitting diode is arrange | positioned infinitely in linear form. It is a ray tracing side view which shows the line illuminating device of the 2nd Embodiment of this invention. It is a graph which shows the illuminance distribution of the Y direction of the line illuminating device shown in FIG. It is a graph which shows the change of the luminous intensity and incident efficiency of LED output light with respect to the angle which the normal line of LED and LED emitted light make. It is a ray tracing side view which shows the line irradiation apparatus using the conventional rod lens. It is a perspective view explaining the field curvature of the conventional line illuminating device shown in FIG.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1 to 4 show a line illumination device according to a first embodiment of the present invention.
As shown in FIGS. 1 and 2A, the line illumination device 10 includes a plurality of light emitting diodes 11, a plurality of numerical aperture conversion lenses 12, and a cylindrical lens 13.

  Each light emitting diode 11 is arranged in a straight line at a predetermined interval. Each light emitting diode 11 is arranged so as to be able to emit light in the same direction perpendicular to the arrangement direction. The bottom side of the light emitting diode 11 is parallel to the arrangement direction.

  Each numerical aperture conversion lens 12 is arranged corresponding to each light emitting diode 11. Each numerical aperture conversion lens 12 has a positive refractive power, and is disposed so that the surface 12a faces the light emitting diode 11 and the distance from the light emitting diode 11 is shorter than the focal length. Thereby, each numerical aperture conversion lens 12 is configured to reduce the numerical aperture of the light emitted from the light emitting diode 11.

  The cylindrical lens 13 has a positive refractive power only in one direction. The cylindrical lens 13 is disposed on the surface 12b side of each numerical aperture conversion lens 12 so as to sandwich the numerical aperture conversion lens 12 between each light emitting diode 11. The cylindrical lens 13 is disposed so as to be parallel to the arrangement direction of each set of the light emitting diode 11 and the numerical aperture converting lens 12 with its surface 13a facing the numerical aperture converting lens 12. Thereby, the cylindrical lens 13 is configured such that the emitted light from each light emitting diode 11 that has passed through each numerical aperture conversion lens 12 is condensed in a straight line parallel to the arrangement direction.

  In the specific example shown in FIG. 1, each light emitting diode 11 has a dimension L = 1 mm square. Each numerical aperture conversion lens 12 has an incident numerical aperture of 0.7 (incidence efficiency: about 50%), and can convert light from the light emitting diode 11 having an output numerical aperture of 1 into light having a numerical aperture of about 0.2. It has become. The cylindrical lens 13 is disposed at a position where the distance from the emission surface 13b to the irradiation surface 14 is 100 mm. Further, the imaging magnification in the Y direction of the optical system is 5 times.

  Further, the curvature radius r1 (mm) of the surface 12a and the curvature radius r2 (mm) of the surface 12b, the curvature radius r3 (mm) in the Y direction of the surface 13a of the cylindrical lens 13, and the Y of the surface 13b. Radius of curvature r4 (mm), distance d0 (mm) between the light emitting diode 11 and the numerical aperture conversion lens 12 in the optical axis, the center thickness d1 (mm) of the numerical aperture conversion lens 12, and the numerical aperture conversion lens 12 in the optical axis Between the cylindrical lens 13 and the cylindrical lens 13, the center thickness d 3 (mm) of the cylindrical lens 13, the distance d 4 (mm) between the cylindrical lens 13 and the irradiation surface 14 in the optical axis, and the refractive index n 1 of the numerical aperture conversion lens 12. , Refractive index n2 of the cylindrical lens 13, Abbe number ν1 of the numerical aperture conversion lens 12, Abbe number ν2 of the cylindrical lens 13, The conical constant k2 of the surface 12b of the numerical aperture conversion lens 12 and the conical constant k4 of the surface 13b of the cylindrical lens 13 are shown below.

d0 = 3
r1 = −16 d1 = 8 n1 = 1.492 ν1 = 57.44
r2 = −6.3 d2 = 22.3 k2 = −0.19
r3 = 77.1 d3 = 10 n2 = 1.492 ν2 = 57.44
r4 = -20.1 d4 = 100 k4 = -1.26

  For comparison, FIG. 2B shows an illuminating device 60 that is designed only with a conventional cylindrical lens 63 that does not have the numerical aperture conversion lens 12. The conventional illumination device 60 shown in FIG. 2B has the same conditions as in FIG. 1, that is, the dimension L of each light emitting diode 61 is 1 mm square, the incident numerical aperture is 0.7, the imaging magnification is 5 times in the Y direction, and the surface 63b The distance from the irradiation surface 64 to the irradiation surface 64 is 100 mm.

  Each constant of the optical system of the conventional illumination device 60, that is, the curvature radius r1 (mm) in the Y direction of the surface 63a of the cylindrical lens 63 and the curvature radius r2 (mm) in the Y direction of the surface 63b, and the light emitting diode 61 on the optical axis. Between the cylindrical lens 63, the center thickness d 1 (mm) of the cylindrical lens 63, the distance d 2 (mm) between the cylindrical lens 63 and the irradiation surface 64 on the optical axis, the refractive index n 1 of the cylindrical lens 63, and the cylindrical The Abbe number ν1 of the lens 63 and the conic constant k2 of the surface 63b of the cylindrical lens 63 are shown below.

d0 = 13.9
r1 = −125 d1 = 10 n1 = 1.883 ν1 = 40.77
r2 = −13.1 d2 = 100 k2 = −0.69

  In the line illuminating device 10 shown in FIG. 2A and the illuminating device 60 shown in FIG. 2B, the spot diagrams of the light emitted from one light emitting diode 11, 61 are respectively shown in FIGS. ). As shown in FIG. 3, the line illuminating device 10 has almost no aberration over the entire region and is distributed on a straight line having a width of 5 mm, but the conventional illuminating device 60 has no aberration near the optical axis, but the periphery thereof. Then, it can be confirmed that the spot is widened due to the aberration caused by the curvature of field.

  Moreover, in the line illuminating device 10 shown in FIG. 2A and the illuminating device 60 shown in FIG. 2B, when the light emitting diodes 11 and 61 having a total luminous flux of 100 lumens (lm) are arranged infinitely at intervals of 10 mm, The illuminance distribution in the Y direction is shown in FIGS. 4 (a) and 4 (b), respectively. As shown in FIG. 4, the line illumination device 10 efficiently irradiates only the 5 mm width, and it can be confirmed that the illuminance of the irradiation unit with the 5 mm width is about twice that of the conventional illumination device 60.

  As described above, the line illumination device 10 is configured such that the numerical aperture conversion lens 12 having a positive refractive power is disposed at a distance shorter than the focal length from the light emitting diode 11 so as to reduce the numerical aperture of the light emitted from the light emitting diode 11. In addition, since the light emitted from the light emitting diode 11 that has passed through the numerical aperture conversion lens 12 is configured to enter the cylindrical lens 13, the occurrence of field curvature can be suppressed. For this reason, aberration can be reduced and illuminance can be increased. In addition, the linearity of the light collected by the cylindrical lens 13 can be improved.

  Moreover, the line illuminating device 10 can raise incident efficiency by setting the incident numerical aperture of the numerical aperture conversion lens 12 high. The line illumination device 10 adjusts the brightness and length of the linear light to be collected according to the number of pairs of light emitting diodes 11 and numerical aperture conversion lenses 12 arranged in a straight line and the interval between the pairs. be able to. In the line illumination device 10, it is preferable that the distance between each set of the light emitting diode 11 and the numerical aperture conversion lens 12 is adjusted so that the collected light is not interrupted and continues linearly.

  In the embodiment shown in FIG. 1 and FIG. 2A, the incident NA of the numerical aperture conversion lens 12 is calculated as 0.7 for comparison with the prior art. The above numerical aperture conversion lens 12 can be designed. Considering conditions such as interference with the imaging system, the output NA of the cylindrical lens 13 is preferably about 0.2. Therefore, the imaging magnification in the Y direction is about 5 times. If the irradiation width is 5 mm, the size of the chip LED is 1 mm. Considering the range of these conditions, the chip size of the light emitting diode 11 is desirably 0.5 to 2 mm.

5 and 6 show a line illumination device according to a second embodiment of the present invention.
As shown in FIG. 5, the line illumination device 20 includes a plurality of light emitting diodes 11, a plurality of numerical aperture conversion lenses 12, and a cylindrical lens 13. In the following description, the same reference numerals are given to the same components as those of the line illumination device 10 according to the first embodiment of the present invention, and redundant descriptions are omitted.

  As shown in FIG. 5, in the line illumination device 20, each set of the light emitting diode 11 and the numerical aperture conversion lens 12 is arranged in two rows of straight lines that are parallel to each other. The cylindrical lens 13 is a linear strip in which the emitted light from each light emitting diode 11 that has passed through each numerical aperture conversion lens 12 is parallel to the arrangement direction of each row of the set including the light emitting diode 11 and the numerical aperture conversion lens 12. It arrange | positions so that it may concentrate on an area | region.

  In a specific example shown in FIG. 5, the line lighting device 20 uses the same light emitting diodes 11, numerical aperture conversion lenses 12, and cylindrical lenses 13 as the line lighting device 10 shown in FIG. 11 and the numerical aperture conversion lens 12 are arranged in two lines in a straight line. The interval between each row is 5 mm. The illuminance distribution in the Y direction at this time is shown in FIG. As shown in FIG. 6, it can be confirmed that the line illuminating device 20 efficiently irradiates a linear strip region having a width twice as large as that in FIG.

  As described above, the line illumination device 20 can adjust the brightness and width of the condensed linear belt-shaped region by the interval between the rows of the set including the light emitting diode 11 and the numerical aperture conversion lens 12. Further, by increasing the number of columns, it is possible to adjust the brightness and width of the condensed straight belt-like region. Moreover, the depth of the irradiation surface 14 can be increased by changing the arrangement in the Z direction.

DESCRIPTION OF SYMBOLS 10, 20 Line illumination apparatus 11 Light emitting diode 12 Numerical aperture conversion lens 12a (incident) surface 12b (emitted) surface 13 Cylindrical lens 13a (incident) surface 13b (emitted) surface 14 Irradiated surface

Claims (3)

A light emitting diode;
A numerical aperture conversion lens that has a positive refractive power and is arranged at an interval shorter than the focal length from the light emitting diode so as to reduce the numerical aperture of the light emitted from the light emitting diode;
A cylindrical lens that has a positive refractive power only in one direction and is arranged so that light emitted from the light emitting diode that has passed through the numerical aperture conversion lens is linearly collected;
A line lighting device comprising: There are a plurality of sets of the light emitting diodes and the numerical aperture conversion lenses, and each set is arranged in a straight line so that light from each light emitting diode can be emitted in the same direction perpendicular to the arrangement direction. ,
The cylindrical lens is arranged so that light emitted from each light-emitting diode that has passed through each numerical aperture conversion lens is condensed in a straight line parallel to the arrangement direction. The line lighting device described. Each set is arranged in a straight line of multiple rows parallel to each other,
The cylindrical lens is arranged so that light emitted from each light emitting diode that has passed through each numerical aperture conversion lens is condensed in a linear strip region parallel to the arrangement direction. 2. The line illumination device according to 2.