JP2014053106A - Illumination device and image inspection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an illumination device capable of reducing illumination unevenness.SOLUTION: An illumination device includes a plurality of reflection type light-emitting diodes aligned in a predetermined direction, and a diffusion filter arranged over the reflection type light-emitting diode other than the reflection type light-emitting diode having the maximum illuminance.

Description

  The present invention relates to an illumination device that illuminates an object, and an image inspection device equipped with the illumination device.

  Conventionally, a lighting device in which a plurality of light emitting elements are arranged is known. As an example, an illuminating device in which the optical axes of a plurality of light emitting diodes are aligned with a slit and light incident from the slit is converted into parallel light through a Fresnel lens can be exemplified. However, this illumination device has a problem that light from a plurality of light emitting diodes is greatly reduced due to diffraction by a slit and diffraction by a Fresnel lens, and is not suitable as an illumination device that irradiates parallel light over a wide range.

  By the way, a technique for irradiating parallel light using a reflective light emitting diode has been studied. Unlike a conventional bullet-type light emitting diode, a reflective light-emitting diode can emit parallel light by itself. Therefore, there is a possibility that parallel light can be irradiated over a wide range by laying reflective light emitting diodes.

  However, when reflection type light emitting diodes are laid, there is a problem in that light is not irradiated from between the light emitting diodes and the light emitting diodes, and since the irradiated light is parallel light, uneven illumination is increased.

  This invention is made | formed in view of said point, and makes it a subject to provide the illuminating device which can reduce illumination nonuniformity.

  The lighting device includes a plurality of reflective light emitting diodes arranged side by side in a predetermined direction, and a diffusion filter installed on each of the reflective light emitting diodes, avoiding a maximum illuminance portion of each of the reflective light emitting diodes. It is a requirement to have.

  According to the disclosed technology, it is possible to provide an illumination device capable of reducing illumination unevenness.

It is a front view which illustrates the illuminating device which concerns on 1st Embodiment. It is a figure which illustrates the block diagram and illumination distribution of the illuminating device which concerns on 1st Embodiment. It is a front view which illustrates the illuminating device which concerns on a comparative example. It is a figure which illustrates the block diagram and illumination distribution of the illuminating device which concerns on a comparative example. It is a front view which illustrates the illuminating device which concerns on 2nd Embodiment. FIG. 6 is a diagram (part 1) illustrating a result of simulating an illuminance distribution of a reflective LED. FIG. 6 is a diagram (part 2) illustrating the result of simulating the illuminance distribution of a reflective LED. It is FIG. (The 1) which illustrates the illuminating device which concerns on 3rd Embodiment. It is FIG. (The 2) which illustrates the illuminating device which concerns on 3rd Embodiment. It is a side view which illustrates the image inspection apparatus which concerns on 4th Embodiment. It is a front view which illustrates the image inspection apparatus which concerns on 4th Embodiment.

  Hereinafter, embodiments for carrying out the invention will be described with reference to the drawings. In the drawings, the same components are denoted by the same reference numerals, and redundant description may be omitted.

<First Embodiment>
FIG. 1 is a front view illustrating a lighting device according to the first embodiment. 2 is a diagram illustrating a configuration diagram and an illumination distribution of the lighting device according to the first embodiment. FIG. 2A is a diagram (bottom surface) viewed from the direction A in FIG. 1, and FIG. The figure (right end surface) seen from B direction of (a), (c) is a figure which illustrates illumination distribution.

  Referring to FIGS. 1 and 2, the illumination device 10 according to the first embodiment includes a contact glass 11, a plurality of reflective light emitting diodes 12 (hereinafter referred to as a reflective LED 12), a diffusion filter 13, and the like. Have A substrate (not shown) is disposed on the lead terminal 12a side of the reflective LED 12, and the lead terminal 12a is inserted into a through hole formed in the substrate (not shown), for example, a land portion around the through hole, solder, or the like. Are electrically and mechanically connected.

  The reflective LEDs 12 are arranged in a row with their upper surfaces (light emitting side surfaces) in close contact with the lower surface of the contact glass 11. In order to reduce illumination unevenness, it is preferable to arrange the reflective LEDs 12 so that they are aligned with no gaps (so that the side surfaces are in contact with each other). However, for the convenience of mounting each reflective LED 12 on a substrate (not shown), a slight gap (about 1 mm or less) may be formed between adjacent reflective LEDs 12.

  Hereinafter, the plurality of arranged reflective LEDs 12 may be collectively referred to as a reflective LED array. In the example of FIG. 1, 16 reflective LEDs 12 are arranged to form one reflective LED array.

  Each reflective LED 12 has a function of irradiating illumination light substantially parallel to each other. The light emitted from each reflective LED 12 is transmitted through the contact glass 11 made of a material transparent to the illumination light of each reflective LED 12 and is, for example, linearly parallel to the object (not shown). Irradiated.

  The diffusion filter 13 is installed on each reflective LED 12 (via the contact glass 11), avoiding the maximum illuminance portion of each reflective LED 12. The maximum illuminance portion of each reflective LED 12 is in the vicinity of the central portion of each reflective LED 12 as shown in FIGS. Therefore, in the example of FIGS. 1 and 2, one diffusion filter 13 is installed between the adjacent reflective LEDs 12 (a boundary portion of the adjacent reflective LEDs 12) and at both ends of the reflective LED array.

  However, one elongated diffusion filter 13 formed with a plurality of openings exposing the maximum illuminance portion (near the center) of each reflective LED 12 is covered from one end to the other end of the reflective LED array. You may install as follows.

  As the diffusion filter 13, for example, on the surface of a resin substrate or the like formed of a material transparent to the illumination light of each reflective LED 12, random minute irregularities or line irregularities or the like having a use wavelength or less are formed. Can be used. For example, polished glass or the like may be used as the diffusion filter 13.

  FIG. 3 is a front view illustrating a lighting device according to a comparative example. 4 is a diagram illustrating a configuration diagram and an illumination distribution of a lighting device according to a comparative example, in which (a) is a diagram (bottom surface) viewed from the direction A in FIG. 3, and (b) is from a direction B in FIG. A view (right end face) and (c) are diagrams illustrating the illumination distribution.

  3 and 4, the illumination device 100 according to the comparative example is different from the illumination device 10 (see FIGS. 1 and 2) only in that the diffusion filter 13 is not provided. In the illuminating device 100, light is not irradiated between the adjacent reflective LEDs 12, and therefore, the illumination distribution is large between the vicinity of the center of each reflective LED 12 and between the adjacent reflective LEDs 12, as shown in the illumination distribution shown in FIG. Lighting unevenness will occur.

  On the other hand, in the illumination device 10, unlike the bright device 100, since the diffusion filters 13 are installed between the adjacent reflective LEDs 12 and at both ends of the reflective LED array, a part of the light emitted from the reflective LEDs 12. Enters the diffusion filter 13 and is diffused by the diffusion filter 13.

  Therefore, as in the solid line portion of the illumination distribution shown in FIG. 2C, compared to the illumination distribution shown in FIG. 4C, the light amount between the adjacent reflective LEDs 12 and the light amounts at both ends of the reflective LED array are reduced. Can be increased. The broken line portion of the illumination distribution shown in FIG. 2 (c) shows the illumination distribution shown in FIG. 4 (c) for comparison. That is, in FIG. 2C, in the region where the solid line portion is larger than the broken line portion, the amount of light is increased due to the effect of installing the diffusion filter 13.

  In addition, even if one elongated diffusion filter having no opening is disposed in the entire reflective LED array, the amount of light between the adjacent reflective LEDs 12 and the amount of light at both ends of the reflective LED array can be increased. However, this method is not preferable because the amount of light near the center of the reflective LED 12 is reduced.

  Like the illuminating device 10, it is preferable to arrange | position the diffusion filter 13 between the adjacent reflective LED12 and the both ends of a reflective LED row | line | column so that the center part vicinity (maximum illumination intensity part) of reflective LED12 may be exposed. Thereby, the light quantity between adjacent reflective LED12 and the light quantity of the both ends of a reflective LED row | line | column can be increased, without reducing the light quantity of the center part vicinity (maximum illumination intensity part) of reflective LED12.

  The range in which the diffusing filter 13 is inserted and the standard of the diffusivity are, for example, a work (low glossy material: for example, a standard reflecting plate having a diffusive reflectance of 99%) and a specular reflectance that are commercially available with diffused line illumination. Take a picture of a high workpiece (high glossy object; for example, a mirror with a specular reflectance of 97% or more). “Evaluation value = average of high glossy object / average of low glossy object” and “flatness = 1 / standard deviation of measured values of high glossy material ”can be used.

  Next, the range in which the diffusion filter 13 is inserted and the diffusivity are varied to measure the above two evaluation values, and the range and diffusivity that are better than the reference value are obtained. In particular, since the evaluation value is a measure of the amount of parallel light, it is preferable to select the range in which the diffusion filter 13 is inserted and the degree of diffusion so that this value is more than double the reference value.

  For example, when the values are as shown in Table 1, it is preferable that the range of the diffusion filter 13 is 5 mm and the diffusivity is 5 ° from the evaluation value and the flatness. It should be noted that illumination unevenness that cannot be reduced at this time can also be reduced by software processing, and therefore it is not preferable to insert a diffusion filter 13 whose evaluation value is greatly reduced. Table 1 shows the relationship between the range of the diffusion filter 13 and the diffusion degree, the evaluation value, and the flatness, and the evaluation value = 4 and the flatness = 0.033 are the reference values.

ソフト処理による照明ムラの軽減方法としては、一例として、リファレンスを撮影して、撮影した画像から補正値を計算し、照明ムラを軽減する方法を挙げることができる。処理方法としては、例えば、白色度の高いワークと照明がない場合の画像を撮影し、白色度の高いワークの撮影画像から照明ムラの補正値を、照明がない場合の画像からオフセット値を決定し、下記の式（１）で補正を行うことができる。

As an example of a method for reducing illumination unevenness by software processing, a method of taking a reference, calculating a correction value from the captured image, and reducing illumination unevenness can be given. As a processing method, for example, a high whiteness workpiece and an image when there is no illumination are photographed, a correction value for uneven illumination is determined from the photographed image of the workpiece with high whiteness, and an offset value is determined from the image when there is no illumination. Then, the correction can be performed by the following equation (1).

ここで、画素の座標を横：ｗ，高さ：ｈ、観測された信号値をＸ（ｗ，ｈ）、補正後の信号値をＹ（ｗ，ｈ）、期待される上限値をＥ（例えば、０〜２５５の値）、オフセット値をＯ（ｗ）、補正値をＲ（ｗ）としている。オフセット値Ｏ（ｗ）は、例えば、全ての反射型ＬＥＤ１２を消灯した状態（遮光した状態）における受光素子（図示せず）の画像データ（黒一色の画像データ）により得られる。又、補正値Ｒ（ｗ）は、例えば、全ての反射型ＬＥＤ１２を点灯して白色基準板を照射し、その反射光を受光素子（図示せず）で読み取った画像データにより得られる。

Here, the coordinates of the pixel are horizontal: w, height: h, the observed signal value is X (w, h), the corrected signal value is Y (w, h), and the expected upper limit value is E ( For example, the value is 0 to 255), the offset value is O (w), and the correction value is R (w). The offset value O (w) is obtained, for example, from image data (black color image data) of a light receiving element (not shown) in a state where all the reflective LEDs 12 are turned off (light-shielded state). The correction value R (w) is obtained from, for example, image data obtained by lighting all the reflective LEDs 12 and irradiating the white reference plate and reading the reflected light with a light receiving element (not shown).

  If a plurality of diffused filters 13 separated in advance are installed only between the adjacent reflective LEDs 12 and at both ends of the reflective LED array, there may be a problem in installation accuracy and installation method. Therefore, when actually manufacturing the lighting device 10, it is possible to provide a diffusion filter that covers the entire reflective LED array, and then remove only the diffusion filter near the center of each reflective LED 12 (maximum illuminance portion), This is preferable in that the arrangement work can be reduced.

  In this way, a plurality of reflective LEDs 12 are densely arranged in one row, and diffusion filters 13 are installed between adjacent reflective LEDs 12 and at both ends of the reflective LED rows, avoiding the maximum illuminance portion of each reflective LED 12. To do. Thereby, the light quantity between adjacent reflective LED12 and the light quantity of the both ends of a reflective LED row | line | column can be increased, without reducing the light quantity of the center part vicinity (maximum illumination intensity part) of reflective LED12. That is, the illumination unevenness can be reduced by diffusing the light with the diffusion filter 13.

  Even when the diffusion filter 13 is installed between the adjacent reflective LEDs 12 and the diffusion filter 13 is not installed at both ends of the reflective LED array, a certain effect (an effect of reducing illumination unevenness) is achieved.

<Second Embodiment>
In 2nd Embodiment, the example of the method of reducing the illumination intensity nonuniformity of an illuminating device is shown, without using a diffusion filter. In the second embodiment, description of the same components as those of the already described embodiments may be omitted.

  FIG. 5 is a front view illustrating a lighting device according to the second embodiment. Referring to FIG. 5, in the illumination device 10 </ b> A according to the second embodiment, a plurality of reflective LEDs 12 are densely arranged in one row in the C direction (hereinafter, referred to as an arrangement direction C) on the contact glass 11. Has been.

  However, in the illumination device 10 (see FIGS. 1 and 2), the side surfaces of the reflective LEDs 12 are arranged so as to be perpendicular to the arrangement direction of the reflective LEDs 12 when viewed from the front. On the other hand, in the illuminating device 10 </ b> A, the side surfaces of the respective reflective LEDs 12 are arranged so as to be inclined with respect to the arrangement direction C of the reflective LEDs 12 in a front view (disposed to be inclined).

  Although the inclination angle θ with respect to the direction perpendicular to the arrangement direction C of the side surfaces of each reflective LED 12 can be determined as appropriate, it can be, for example, about 15 degrees. The front view refers to viewing the illumination device 10 </ b> A or the like from a direction perpendicular to the light emitting side surface of the reflective LED 12.

  Thus, by arranging each reflective LED 12 so that the side surface of each reflective LED 12 is inclined with respect to the arrangement direction C in a front view, there is a portion where the amount of illumination light between the adjacent reflective LEDs 12 is small. Distributed in the horizontal direction. Therefore, it is possible to reduce illuminance unevenness of the lighting device 10A.

  The value of the inclination angle θ can be determined from information such as the illuminance distribution of the reflective LED 12 and the length L of the overlapping portion of the adjacent reflective LED 12. For example, when the reflective LEDs 12 having a planar shape of 11 mm × 7 mm are arranged at intervals of 0.3 mm and the inclination angle θ is 15 degrees, the length L is about 2 mm.

  Here, the illuminance distribution in the arrangement direction C of the reflective LEDs 12 is measured, and the illuminance distribution when there is an overlap of 2 mm is simulated using the measured illuminance distribution. FIG. 6 is a diagram illustrating the result of simulating the illuminance distribution when there is an overlap of 2 mm between adjacent reflective LEDs 12 (when L = 2 mm). As shown in FIG. 6, the illuminance of each reflective LED 12 gradually decreases from the central peak (maximum illuminance) to the periphery, and the end portion becomes dark.

  However, since there is an overlap of 2 mm, the illuminance at the end portion (between adjacent reflective LEDs 12) can actually be increased as shown by the solid line in FIG. The appropriate value of the inclination angle θ is an angle at which the illuminance between adjacent reflective LEDs 12 is raised to the same extent as the maximum illuminance of each reflective LED 12.

  In FIG. 7, the illuminance between adjacent reflective LEDs 12 is raised to the same level as the maximum illuminance of each reflective LED 12, and therefore, with the reflective LED 12 used for the simulation, the inclination angle θ = 15 degrees is approximately appropriate. It is an angle. However, since the appropriate inclination angle θ varies depending on the illuminance distribution and arrangement of the reflective LED 12, when the illuminance distribution and arrangement conditions of the reflective LED 12 change, such a simulation is used to make an inclination angle each time. The optimum value of θ will be determined.

  As in the first embodiment, illumination unevenness that cannot be reduced at this point can be reduced by software processing.

<Third Embodiment>
In the third embodiment, an example in which reflective LEDs are arranged in a plurality of rows is shown. In the third embodiment, the description of the same components as those of the already described embodiments may be omitted.

  FIGS. 8A and 8B are diagrams illustrating a lighting device according to the third embodiment, in which FIG. 8A is a front view and FIG. 8B is a view (left end surface) viewed from the D direction of FIG. Referring to FIG. 8, the illumination device 10 </ b> B according to the third embodiment includes a dichroic mirror 15, a plurality of reflective LEDs 12, and a plurality of reflective LEDs 22.

  The reflective LED 22 has a lead terminal 22a. A board (not shown) different from the board for fixing the reflective LED 12 is disposed on the lead terminal 22a side of the reflective LED 22, and the lead terminal 22a is inserted into a through hole formed in the board, for example, It is electrically and mechanically connected to the land portion by solder or the like.

  Each reflective LED 12 is arranged in a row with its upper surface (light emitting side surface) in close contact with the lower surface of the dichroic mirror 15, and each reflective LED 22 has its upper surface (light emitting side surface) arranged on the dichroic mirror 15. Are arranged in a row in close contact with one side surface. Note that the rows of the reflective LEDs 12 and the rows of the reflective LEDs 22 are substantially parallel.

  However, the positions of the reflective LED 12 and the reflective LED 22 in the arrangement direction are shifted. That is, each reflective LED 12 and each reflective LED 22 are arranged such that the peak (maximum illuminance) of each reflective LED 12 and the peak (maximum illuminance) of each reflective LED 22 are at different positions in the arrangement direction. ing.

  In order to reduce illumination unevenness, it is preferable that the reflective LEDs 12 and 22 be arranged in a line without gaps (so that the side surfaces are in contact with each other). However, for the convenience of mounting each of the reflective LEDs 12 and 22 on a substrate (not shown), some gaps may be formed between the adjacent reflective LEDs 12 and between the adjacent reflective LEDs 22.

  Each of the reflective LEDs 12 and 22 has a function of irradiating illumination light substantially parallel to each other. However, the reflective LED 22 has a function of irradiating illumination light having a wavelength different from that of the reflective LED 12. For example, the reflective LED 12 can be a red LED and the reflective LED 22 can be a green LED. The external shape of the reflective LED 22 may be the same as the external shape of the reflective LED 12.

  The light irradiated from each reflective LED 12 enters the dichroic mirror 15, exits from the dichroic mirror 15 that transmits the wavelength of the illumination light of each reflective LED 12, and is irradiated onto an object (not shown). The light emitted from each reflective LED 22 enters the dichroic mirror 15, and is emitted after the optical path is converted by the dichroic mirror 15 that reflects the wavelength of the illumination light of each reflective LED 22, and then the object (not shown). )).

  In FIG. 8B, for convenience of explanation, the illumination light (solid arrow) of each reflective LED 12 and the illumination light (broken arrow) of each reflective LED 22 are shown shifted, but these are dichroic mirrors. 15 is synthesized on the same optical axis and irradiated to an object (not shown).

  In this way, a plurality of reflective LEDs 12 and 22 having different wavelengths are arranged in a predetermined direction, and each illumination light from the reflective LEDs 12 and 22 is reflected and transmitted by the dichroic mirror 15 on the same optical axis. Overlapping. Further, the positions in the arrangement direction of the 12 peaks (maximum illuminance) of the reflective LED and the peak (maximum illuminance) of the reflective LED 22 are shifted. Thereby, the shortage of light quantity can be compensated. That is, the portion where the light amount between the adjacent reflective LEDs 12 decreases can be supplemented with the light amount of the reflective LED 22, and the portion where the light amount between the adjacent reflective LEDs 22 decreases can be supplemented with the light amount of the reflective LED 12. Thereby, uneven illumination can be reduced.

  A plurality of reflective LEDs 32 may be further added as in the illumination device 10C shown in FIG. The reflective LED 32 has a lead terminal 32a. On the lead terminal 32a side of the reflective LED 32, a substrate (not shown) different from the substrate on which the reflective LEDs 12 and 22 are fixed is disposed. The lead terminal 32a is inserted into a through hole formed in the substrate, for example, and is electrically and mechanically connected to a land portion around the through hole by solder or the like.

  The reflective LEDs 32 are arranged in a line with their upper surfaces (light emitting side surfaces) in close contact with the other side surface of the dichroic mirror 15. Note that the row of the reflective LEDs 12, the row of the reflective LEDs 22 and the row of the reflective LEDs 32 are substantially parallel.

  However, the positions of the reflective LED 12, the reflective LED 22, and the reflective LED 32 in the arrangement direction are shifted. That is, each reflection type LED 12, each reflection type LED 22, and each reflection type LED 32 are the peak (maximum illuminance) of each reflection type LED 12, the peak (maximum illuminance) of each reflection type LED 22, and the peak (maximum illuminance) of each reflection type LED 32. Are arranged at positions different from each other in the arrangement direction.

  In order to reduce illumination unevenness, it is preferable to arrange the reflective LEDs 12, 22, and 32 so that they are aligned with no gaps (so that the side surfaces are in contact with each other). However, for the convenience of mounting each of the reflective LEDs 12, 22, and 32 on a substrate (not shown), there is a slight gap between the adjacent reflective LEDs 12, between the adjacent reflective LEDs 22, and between the adjacent reflective LEDs 32. It may be possible.

  Each reflective LED 12, 22, and 32 has a function of irradiating illumination light substantially parallel to each other. However, the reflective LEDs 12, 22, and 32 each have a function of irradiating illumination light having different wavelengths. For example, the reflective LED 12 can be a red LED, the reflective LED 22 can be a green LED, and the reflective LED 32 can be a blue LED. The external shape of the reflective LED 32 may be the same as the external shape of the reflective LEDs 12 and 22.

  The light irradiated from each reflective LED 12 enters the dichroic mirror 15, exits from the dichroic mirror 15 that transmits the wavelength of the illumination light of each reflective LED 12, and is irradiated onto an object (not shown). The light emitted from each reflective LED 22 enters the dichroic mirror 15, and is emitted after the optical path is converted by the dichroic mirror 15 that reflects the wavelength of the illumination light of each reflective LED 22, and then the object (not shown). )). The light emitted from each reflective LED 32 is incident on the dichroic mirror 15, and is emitted after the optical path is converted by the dichroic mirror 15 that reflects the wavelength of the illumination light of each reflective LED 32. )).

  In FIG. 9B, for convenience of explanation, the illumination light of each reflective LED 12 (solid line arrow), the illumination light of each reflective LED 22 (broken line arrow), and the illumination light of each reflective LED 32 (dotted line arrow) The figure is shifted. However, in practice, these are synthesized on the same optical axis by the dichroic mirror 15 and irradiated onto an object (not shown). The illumination device 10 </ b> C shown in FIG. 9 can compensate for the shortage of the light amount, similarly to the illumination device 10 </ b> B shown in FIG. 8.

  When using the illumination devices 10B and 10C, it is necessary to correct by adding an offset value for each wavelength to the signal value of the photographed image using a monochrome camera when photographing regularly reflected light. The correction value can be obtained by using a high gloss mirror or the like as a work (object) and photographing the reflected light.

  Further, by changing the color of the reflective LED to be lit according to the color of the work to be photographed, it is possible to photograph an image of only regular reflection light. For example, when photographing a red workpiece, a blue or green (or blue and green) reflective LED is turned on so that diffuse reflection light from the workpiece is minimized. Note that, after being converted into a monochrome image, illumination unevenness that cannot be reduced at this point can be reduced by software processing as in the first embodiment.

<Fourth embodiment>
In 4th Embodiment, the example of the image inspection apparatus carrying the illuminating device 10 which concerns on 1st Embodiment is shown. Note that in the fourth embodiment, the description of the same component as the already described embodiment may be omitted.

  FIG. 10 is a side view illustrating an image inspection apparatus according to the fourth embodiment. FIG. 11 is a front view illustrating an image inspection apparatus according to the fourth embodiment. For convenience of explanation, some components of FIG. 10 are omitted in FIG.

  Referring to FIGS. 10 and 11, the image inspection apparatus 40 includes an illumination apparatus 10, a curved mirror 41, a concentration illumination apparatus 42, an imaging lens 43, an image sensor 44, and a transport unit 45. . Reference numeral 90 denotes an image bearing medium such as paper (hereinafter referred to as an image bearing medium 90) as a measurement object, and 90a denotes one line on the image bearing medium 90 from which the gloss distribution and density distribution are read by the image inspection apparatus 40. , 90b indicates the transport direction of the image bearing medium 90 (hereinafter referred to as the transport direction 90b).

  Note that the specularly reflected light refers to reflected light that is reflected at the same angle as the incident angle of the illuminating light applied to the image bearing medium 90 from the illuminating device 10 and is reflected to the opposite side of the incident direction. Refers to reflected light other than specularly reflected light.

  Each reflective LED 12 of the illumination device 10 has a function of irradiating illumination light 12x incident on the curved mirror 41 and substantially parallel to each other. That is, the illumination device 10 is a linear parallel light source that generates linear substantially parallel light. In the illuminating device 10, since substantially parallel light is generated on the entire surface of the light emitting portion of each reflective LED 12, there is an effect that the illumination light is not interrupted throughout the reading region 90a.

  In FIG. 1, the number of the reflective LEDs 12 included in the illumination device 10 is 16. However, the number of the reflective LEDs 12 included in the illumination device 10 may be arbitrarily set. Unless the reflective LEDs 12 are densely arranged in the direction of the reading area 90a (the Y direction in FIGS. 10 and 11), it is impossible to generate illumination light that generates specularly reflected light in all areas of the reading area 90a. Therefore, it is preferable that the number of the reflective LEDs 12 is large.

  The curved mirror 41 has a concave curved surface with a predetermined curvature in the linear direction (longitudinal direction) of the lighting device 10. The curved mirror 41 reflects (optical path change) the substantially parallel illumination light 12x from the illumination device 10, and the illumination light is incident on the pupil of the imaging lens 43 when the specular reflection light is irradiated onto the measurement object. 12y is generated. The concave curved surface of the curved mirror 41 has a curvature at which the regular reflection light 12z corresponding to the illumination light 12y is incident on the pupil of the imaging lens 43.

That is, the substantially parallel illumination light 12x emitted from each reflective LED 12 of the illumination device 10 enters the curved mirror 41 having a concave curved surface with a predetermined curvature, is reflected by the curved mirror 41, and travels in different directions. Illuminating light 12y is generated. Illumination light 12y reflected by the curved mirror 41 is incident at an incident angle theta ₁ to the entire scan area 90a of the image-carrying medium 90. Then, the illumination light 12y is specularly reflected throughout the reading region 90a to become specularly reflected light 12z (here, the incident angle θ ₁ = the reflection angle θ ₂ ). The specularly reflected light 12z is directed to enter the pupil of the imaging lens 43, respectively. The illumination device 10 and the curved mirror 41 are typical examples of the light illumination means according to the present invention.

The density illumination device 42 has a function of irradiating illumination light 42x incident on the reading region 90a of the image bearing medium 90 at a predetermined angle. The predetermined angle may be any angle as long as it is different from the incident angle θ ₁ , but can be set to 90 deg, for example. As the concentration illumination device 42, for example, a diffuse illumination device such as a xenon lamp or an LED array can be used. Note that the illumination device 10 and the concentration illumination device 42 which are glossy illumination devices do not emit light at the same time, and emit light alternately in accordance with the drive of the image sensor 44, or either one emits light at any time. It is comprised so that it may radiate | emit.

  The imaging lens 43 and the image sensor 44 are arranged at a position where the regular reflection light 12z can be received. In addition, the imaging lens 43 and the image pickup device 44 can receive the diffuse reflected light 42y that is a part of the diffuse reflected light of the illumination light 42x emitted from the density illumination device 42 to the reading region 90a of the image bearing medium 90. Placed in position. The imaging lens 43 is composed of, for example, a plurality of lenses, and has a function of imaging the regular reflection light 12z of the illumination light 12y irradiated on the image bearing medium 90 or the diffuse reflection light 42y of the illumination light 42x on the image sensor 44. Have.

  The imaging element 44 is composed of a plurality of pixels, and has a function of acquiring the amount of regular reflection light 12z or diffuse reflection light 42y incident through the imaging lens 43. As the image sensor 44, for example, a metal oxide semiconductor device (MOS), a complementary metal oxide semiconductor device (CMOS), a charge coupled device (CCD), a contact image sensor (CIS), or the like can be used. In the present embodiment, a one-dimensional reading type image sensor is used as the image sensor 44. When a color image is targeted, an image sensor such as a 3-line type having sensitivity to each color of RGB may be used. The imaging element 44 is a typical example of the imaging means according to the present invention.

  The transport unit 45 has a function of transporting the image bearing medium 90 in, for example, the transport direction 90b (X direction in FIG. 10). Note that the arrangement direction of the reflective LEDs 12 of the illumination device 10 can be, for example, a direction perpendicular to the transport direction 90 b of the transport unit 45.

  The inspection of the gloss distribution and the density distribution in the image inspection apparatus 40 is performed as follows. That is, the image inspection device 40 first turns on the illumination device 10 (the concentration illumination device 42 is turned off) and irradiates the illumination light 12y to the one-line reading region 90a. Then, the light amount of the regular reflection light 12z from the reading region 90a is acquired by the image sensor 44. Then, the gloss distribution of the reading region 90a is inspected based on the acquired amount of the regular reflection light 12z.

  Next, the image inspection apparatus 40 turns on the density illumination device 42 (the illumination device 10 is turned off) and irradiates the illumination light 42x to the one-line reading region 90a. Then, the amount of diffuse reflected light 42y from the reading area 90a is acquired by the image sensor 44. Then, the density distribution of the reading region 90a is inspected based on the acquired amount of diffuse reflected light 42y. This completes the inspection of the gloss distribution and density distribution of one line (one dimension).

  When the inspection of the gloss distribution and density distribution of one line (one-dimensional) is completed, the transport unit 45 transports the image bearing medium 90 by a predetermined distance in the transport direction 90b. Then, the same inspection as described above is performed for the next one line (one dimension). By repeating this operation, two-dimensional gloss distribution and density distribution can be inspected.

  Note that, as described below, the inspection of the gloss distribution and the density distribution for each line (one dimension) may not be performed, and only the inspection of the two-dimensional gloss distribution and the density distribution may be performed. That is, the image inspection device 40 first turns on the illumination device 10 (the concentration illumination device 42 is turned off) and irradiates the illumination light 12y to the one-line reading region 90a. Then, the image sensor 44 acquires and stores the amount of the regular reflection light 12z from the reading area 90a.

  Next, the image inspection apparatus 40 turns on the density illumination device 42 (the illumination device 10 is turned off) and irradiates the illumination light 42x to the one-line reading region 90a. Then, the image sensor 44 acquires and stores the amount of diffuse reflected light 42y from the reading region 90a.

  Next, the transport unit 45 transports the image bearing medium 90 by a predetermined distance in the transport direction 90b. Then, for the next one line (one dimension), the light amount of the regular reflection light 12z and the light amount of the diffuse reflection light 42y are acquired and stored in the same manner as described above. By repeating this operation, the light quantity of the regular reflection light 12z and the light quantity of the diffuse reflection light 42y can be acquired in two dimensions. Thereafter, the two-dimensional gloss distribution and density distribution are inspected based on the light amount of the regular reflection light 12z and the light amount of the diffuse reflection light 42y acquired and stored in two dimensions.

  In the image inspection apparatus 40, the illuminating device 10 is substantially parallel light, and it is better that the principal ray has directivity in the pupil direction, and it is better that there is less light in other directions. Therefore, a configuration without diffuse reflected light is desirable. In addition, if the light amount between the adjacent reflective LEDs 12 in the illumination device 10 is small, illumination unevenness (hereinafter, the illumination uneven portion may be referred to as a gap) occurs, and the inspection accuracy extremely decreases in the gap portion. For this reason, it is necessary to exclude from the two-dimensional gloss distribution a portion photographed in the gap portion at the time of inspection.

  However, as shown in the first embodiment, in the illumination device 10, a plurality of reflective LEDs 12 are densely arranged in one row, and one diffusion filter 13 is arranged between adjacent reflective LEDs 12. . And thereby, the light quantity between adjacent reflective LED12 is made to increase, without reducing the light quantity of the center part vicinity of reflective LED12. Therefore, in the image inspection apparatus 40, it is not necessary to exclude a portion photographed with light between the adjacent reflective LEDs 12 from the two-dimensional gloss distribution.

  However, the accuracy of the portion where the diffusion filter 13 is inserted is lower than the portion where the diffusion filter 13 is not inserted. If the influence of diffused light is large, the ratio of diffusely reflected light is obtained from a two-dimensional gloss distribution obtained by photographing an object having a high diffuse reflectance and a low regular reflectance. Then, the influence of diffused light can be reduced by subtracting the estimated density distribution obtained from the ratio and the two-dimensional density distribution from the two-dimensional gloss distribution.

  As described above, by mounting the illumination device 10 according to the first embodiment on the image inspection device 40, it is possible to photograph a two-dimensional gloss distribution with little illumination unevenness, and inspect the captured two-dimensional gloss distribution. Can be used. As a result, a more accurate inspection can be performed.

<Variation 1 of the fourth embodiment>
In the first modification of the fourth embodiment, an example of an image inspection apparatus equipped with the illumination device 10A according to the second embodiment is shown. In the first modification of the fourth embodiment, the description of the same components as those of the already described embodiment may be omitted.

  10 and 11, the lighting device 10 </ b> A according to the second embodiment may be mounted instead of the lighting device 10. When the illumination device 10A is mounted, it is possible to photograph a two-dimensional gloss distribution with little illumination unevenness as in the case of the illumination device 10, and the captured two-dimensional gloss distribution can be used for inspection. As a result, a more accurate inspection can be performed.

  Unlike the illumination device 10, the illumination device 10 </ b> A is irradiated with the same parallel light as that of a normal reflective LED because the diffusion filter 13 is not inserted. Therefore, it is preferable in that it is not necessary to perform the subtraction of the diffused light described in the fourth embodiment.

  However, in the illuminating device 10 </ b> A, the side surfaces of the respective reflective LEDs 12 are disposed to be inclined (disposed obliquely) with respect to the arrangement direction C of the reflective LEDs 12, so that the intensity of parallel light is generated. Therefore, it is preferable to correct the intensity of parallel light. The correction of the intensity of parallel light is performed by, for example, illuminating from a two-dimensional gloss distribution obtained by photographing paper before printing (the same or same whiteness and regular reflectance as the printed matter to be measured). This can be done by calculating the unevenness. If the inspection object is not glossy, it is not necessary to correct the intensity of parallel light.

<Modification 2 of the fourth embodiment>
In the second modification of the fourth embodiment, an example of an image inspection apparatus equipped with the illumination device 10B according to the third embodiment is shown. In the second modification of the fourth embodiment, the description of the same components as those of the already described embodiment may be omitted.

  10 and 11, instead of the illumination device 10, an illumination device 10B according to the third embodiment may be mounted. When the illumination device 10B is mounted, similarly to the case where the illumination device 10 is mounted, it is possible to photograph a two-dimensional gloss distribution with little illumination unevenness, and the captured two-dimensional gloss distribution can be used for inspection. As a result, a more accurate inspection can be performed.

  In addition, unlike the illuminating device 10, the illuminating device 10B is irradiated with the same parallel light as a normal reflection type LED because the diffusion filter 13 is not inserted. Therefore, it is preferable in that it is not necessary to perform the subtraction of the diffused light described in the fourth embodiment.

  When the illumination device 10B is mounted, if the illuminance of each reflective LED gradually falls from the peak as shown in FIG. 6, the peak portion is adopted as it is when the images in the respective wavelength bands are superimposed. It is preferable to calculate a weighted value for the gently falling portion. Alternatively, it is possible to increase the inspection accuracy by referring to the two-dimensional concentration distribution and adopting data in a wavelength band having the least influence.

  It should be noted that the same effect can be obtained even if the illumination device 10C is mounted instead of the illumination device 10B.

  The preferred embodiment and its modification have been described in detail above, but the present invention is not limited to the above-described embodiment and its modification, and the above-described implementation is performed without departing from the scope described in the claims. Various modifications and substitutions can be added to the embodiment and its modifications.

  For example, in the third embodiment, the reflective LED is disposed such that the upper surface of the reflective LED is in contact with a predetermined surface of the dichroic mirror. However, as in the first embodiment, the reflective LED may be arranged such that the upper surface of the reflective LED is in contact with the lower surface of the contact glass, and the light emitted from the reflective LED may enter the dichroic mirror through the contact glass. .

  In FIG. 9 of the third embodiment, only the reflective LEDs 22 and 32 may be used, and the reflective LED 12 may be omitted. That is, the reflective LEDs having different wavelengths may be arranged to face each other via the dichroic mirror, and the illumination light from each reflective LED may be reflected by the dichroic mirror and synthesized.

  Moreover, in each embodiment, when the illumination light from each reflection type LED is irradiated linearly to a target object, the arrangement of each reflection type LED does not need to be linear. For example, the reflective LEDs may be arranged in a curved shape (arch), and the illumination light from each reflective LED may be linear after being reflected by a curved mirror.

10, 10A, 10B, 10C Illumination device 11 Contact glass 12, 22, 32 Reflection type light emitting diode (reflection type LED)
12a, 22a, 32a Lead terminals 12x, 12y, 42x Illumination light 12z Regular reflection light 13 Diffusion filter 15 Dichroic mirror 40 Image inspection device 41 Curved surface mirror 42 Concentration illumination device 42y Diffuse reflection light 43 Imaging lens 44 Imaging element 45 Conveying means 90 Image bearing medium 90a Reading area 90b Transport direction θ ₁ Incident angle θ ₂ Reflection angle

JP 2005-147817 A

Claims (10)

A plurality of reflective light emitting diodes arranged side by side in a predetermined direction;
A diffusing filter installed on each of the reflection type light emitting diodes, avoiding the maximum illuminance portion of each of the reflection type light emitting diodes.   The illuminating device according to claim 1, wherein the diffusion filter is installed so as to cover at least a boundary portion between the adjacent reflective light emitting diodes.   2. The diffusion filter is installed so as to cover the plurality of reflection type light emitting diodes, and the diffusion filter is formed with a plurality of openings for exposing the maximum illuminance portions of the reflection type light emitting diodes. Or the illuminating device of 2. Having a plurality of reflective light emitting diodes arranged side by side in a predetermined direction;
Each of the reflection type light emitting diodes is disposed such that a side surface of each of the reflection type light emitting diodes is inclined with respect to the predetermined direction in a front view. A plurality of first reflective light emitting diodes arranged side by side in a predetermined direction and emitting light including a first wavelength;
A plurality of second reflective light emitting diodes that emit light including a second wavelength arranged side by side in a direction parallel to the predetermined direction;
A dichroic mirror that enters the light including the first wavelength and the light including the second wavelength and emits the light superimposed on the same optical axis;
Each of the first reflective light emitting diodes and each of the second reflective light emitting diodes includes a maximum illuminance portion of each of the first reflective light emitting diodes and each of the second reflective light emitting diodes. A lighting device arranged such that a maximum illuminance portion is located at a different position in the predetermined direction. Each of the first reflective light emitting diodes is arranged side by side on the first surface of the dichroic mirror such that the light emitting side surface is in contact with the first surface of the dichroic mirror,
6. The illumination according to claim 5, wherein each of the second reflective light emitting diodes is arranged side by side on the second surface of the dichroic mirror such that the light emitting side surface is in contact with the second surface of the dichroic mirror. apparatus. A plurality of third reflective light emitting diodes that emit light including a third wavelength arranged side by side in a direction parallel to the predetermined direction;
Each of the first reflective light-emitting diodes, each of the second reflective light-emitting diodes, and each of the third reflective light-emitting diodes is a maximum illuminance of each of the first reflective light-emitting diodes. The portion, the maximum illuminance portion of each of the second reflective light emitting diodes, and the maximum illuminance portion of each of the third reflective light emitting diodes are arranged so as to be at different positions in the predetermined direction. Or the illuminating device of 6. Light illuminating means including the illuminating device according to any one of claims 1 to 7, and irradiating illumination light from an oblique direction to an object on which an image is formed;
And imaging means for receiving specularly reflected light of the illumination light irradiated on the object,
An image inspection apparatus that inspects the image based on a light amount of the regular reflection light received by the imaging unit.   The image inspection apparatus according to claim 8, wherein the gloss distribution of the object is inspected based on a light amount of the regular reflection light received by the imaging unit. Having a conveying means for conveying the object;
The image inspection apparatus according to claim 8, wherein the predetermined direction is a direction perpendicular to a transport direction of the transport unit.

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