JP2009222711A - Apparatus and method for inspecting optical transmitter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus and method for inspecting an optical transmitter capable of easily measuring optical characteristics of the optical transmitter regarding a main scanning direction and a sub scanning direction, and capable of shortening an inspection time. <P>SOLUTION: The inspection apparatus for the optical transmitter and the inspection method for the optical transmitter includes a detection step of for radiating light from a light source on the optical transmitter through a measurement pattern 18 having a boundary line 24 between a transparent area 22 and a black area 20 inclined a predetermined angle with respect to a scanning direction A while moving a rod lens array in one direction and detecting information of a quantity of outgoing light from the optical transmitter in regard to an area 32 including a boundary part 24A by an area sensor, a light quantity distribution acquisition step of breaking down the information of light quantity into light quantity components in the main scanning direction in parallel wit the scanning direction A and the sub scanning direction crossing the main scanning direction on the basis of the information of light quantity in regard to the area 32 detected in the detection step and acquiring information of light quantity distribution in regard to these directions, and a calculating step of calculating the optical characteristics of the optical transmitter in regard to the main scanning direction and the sub scanning direction on the basis of the information of light quantity distribution acquired in the light quantity distribution acquisition step. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to an optical transmission body inspection device and an optical transmission body inspection method, and more particularly, to allow inspection light from a light source to enter the optical transmission body while moving the optical transmission body in one direction, and to emit the emitted light. It is related with the inspection apparatus of the optical transmission body which inspects the optical characteristic of an optical transmission body, and the inspection method of an optical transmission body.

  2. Description of the Related Art Conventionally, as an inspection apparatus for inspecting optical characteristics of an optical transmission body, an apparatus that measures an MTF (Modulation Transfer Function) of the optical transmission body is known (Patent Document 1). The inspection apparatus described in Patent Document 1 measures MTF of an optical transmission body by a contrast method. That is, in the inspection apparatus described in Patent Literature 1, inspection light emitted from a light source through a lattice pattern having a specific spatial frequency is irradiated onto a rod lens array that is an optical transmission body, and the rod lens array is aligned in one direction. The light emitted from each rod lens is measured with a line sensor. And MTF is calculated based on the information of the light quantity regarding the moving direction obtained by the line sensor.

Japanese Patent Laid-Open No. 4-128627

In recent years, since an optical transmission body is also used in a field where high resolution is required, it has become necessary to perform MTF measurement of the optical transmission body in more detail than before. Therefore, in recent MTF measurement, the MTF of the rod lens array for high resolution is measured not only in the main scanning direction parallel to the moving direction but also in the sub-scanning direction perpendicular to the main scanning direction. The MTF is also measured for two or more spatial frequencies.
However, in such a case, in the conventional inspection apparatus, it is necessary to calculate the MTF by moving the rod lens array separately in the main scanning direction and the sub-scanning direction. Therefore, there is a problem that the inspection method is complicated and takes an inspection time.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an optical transmission body inspection apparatus that can easily measure the optical characteristics of the optical transmission body with respect to the moving direction of the optical transmission body and the direction orthogonal to the moving direction, and can reduce the inspection time. And providing an inspection method of an optical transmission body.

  In order to achieve the above object, the present invention comprises a light source provided with a measurement pattern, and detection means arranged to face the light source, while moving the optical transmission body in one direction from the light source. An inspection device for an optical transmission body that inspects the optical characteristics of the optical transmission body by causing the inspection light to enter the optical transmission body and detecting the emitted light by a detection means. The measurement pattern includes a light shielding region and a transparent And at least a part of the boundary line between the light shielding area and the transparent area is inclined at a predetermined angle with respect to the moving direction of the optical transmission body, and the detecting means includes an area including at least a part of the inclined boundary line. It has the area sensor which detects the light quantity of an emitted light about, It is characterized by the above-mentioned.

  In the present invention configured as described above, at least a part of the boundary line between the light-shielding region and the transparent region of the measurement pattern is inclined by a predetermined angle with respect to the moving direction, and the emitted light from the optical transmitter is transmitted by the area sensor. Since the detection is performed in the region, the information on the light amount of the emitted light obtained for the region including the boundary line can be decomposed into the moving direction and the direction orthogonal to the moving direction, and information on the light amount in both directions can be obtained. Therefore, optical characteristics in both the moving direction and the direction orthogonal to the moving direction can be obtained in a single inspection process.

In a conventional inspection apparatus, the measurement pattern is a striped pattern in which light-shielding areas and transparent areas are alternately arranged at a predetermined interval, and the stripes of the measurement pattern, that is, the boundary between the light-shielding areas and the transparent areas The line was arranged so as to be orthogonal to the moving direction. Therefore, in order to measure the optical characteristics in the direction orthogonal to the moving direction, the optical transmission body is rotated by 90 ° with respect to the measurement pattern, and the optical transmission body is moved in the direction orthogonal to the initial moving direction to perform optical measurement. The property had to be measured.
On the other hand, in the present invention, at least part of the boundary line between the light shielding region and the transparent region of the measurement pattern is inclined by a predetermined angle with respect to the moving direction, and the emitted light from the optical transmission body is regiond by the area sensor Therefore, it is possible to obtain information on the amount of light in both directions in the direction of movement and in the direction orthogonal to the direction of movement in a single inspection operation, so there is no need to rotate the optical transmission body by 90 °, There is no need to perform the measurement work of the light emitted from the optical transmission body in both directions orthogonal to each other. Therefore, the optical characteristics of the optical transmission body can be easily measured, and the optical characteristics of the high-resolution optical transmission body can be easily and in a short time.

In the present invention, preferably, the predetermined angle is an acute angle formed by the boundary line and the moving direction, and is 30 to 60 °. More preferably, the predetermined angle is 45 °.
In the present invention configured as described above, the predetermined angle of the boundary line is set to 30 ° to 60 °, and more preferably 45 °, so that the optical characteristics in both the moving direction and the direction orthogonal to the moving direction. It is possible to obtain information on the amount of light that is accurate enough to calculate. Accordingly, the optical characteristics of the optical transmission body can be measured with sufficiently high accuracy in both the moving direction and the direction orthogonal to the moving direction.

  If the angle of the boundary line with respect to the moving direction is smaller than 30 °, it is difficult to obtain accurate information of the emitted light related to the moving direction, and the inspection accuracy of the optical characteristics related to this direction is lowered. Further, if the angle of the boundary line with respect to the moving direction is larger than 60 °, it is difficult to obtain accurate information of the emitted light in the direction orthogonal to the moving direction, and the inspection accuracy of the optical characteristics related to this direction is lowered. Most preferably in this angular range, the angle of the boundary line relative to the moving direction is 45 °. In this case, the information on the amount of emitted light in the moving direction and the direction orthogonal to the moving direction is equivalent. As a result, the optical characteristics in both directions can be measured with the same accuracy. In addition, when the predetermined angle is set to 45 °, it becomes easy to decompose the information on the light amount of the emitted light obtained by the area sensor into information on the light amount in the moving direction and the direction orthogonal to the moving direction.

Further, the measurement pattern has a triangular wave-shaped boundary line along the moving direction in which boundary lines inclined at a predetermined angle in directions opposite to each other in the moving direction are alternately continued.
In the present invention configured as described above, since the measurement pattern has a triangular wave-like boundary line along the movement direction, the measurement pattern has a boundary line between the light shielding region and the transparent region along the movement direction. Appears repeatedly. Therefore, since the information of the emitted light from the optical transmission body can be measured for each boundary line along the moving direction of the optical transmission body, the information of the emitted light at a plurality of locations can be obtained with one jagged boundary line. . Here, the measurement pattern needs to be manufactured with high accuracy in order to obtain highly accurate information on the emitted light. However, in the present invention, the measurement pattern has a triangular wave boundary line. In order to produce a plurality of measurement points, one boundary line having a predetermined number of triangular waves may be produced. Therefore, the measurement pattern can be easily produced, and the measurement pattern can be produced with high accuracy.

  Further, by adjusting the length of one side of the triangular wave, a plurality of boundary lines inclined at a predetermined angle at predetermined intervals along the moving direction can be formed. Therefore, by using this measurement pattern, it is possible to acquire data at a plurality of boundary lines on one screen of the area sensor, and evaluate optical characteristics at a plurality of locations on the screen at once, that is, a plurality of locations of the optical transmission body. Is possible.

  In order to achieve the above object, the method for inspecting an optical transmission body of the present invention is configured to move light from a light source while moving the optical transmission body in one direction. An area sensor is used to illuminate the optical transmission body through a measurement pattern having a light shielding area and a transparent area inclined at a predetermined angle, and to output information on the amount of light emitted from the optical transmission body for an area including at least part of the boundary line. Based on the detection process to detect and the light quantity information on the area detected in the detection process, the light quantity information is decomposed into a light quantity component in the main scanning direction parallel to the moving direction and in the sub scanning direction orthogonal to the main scanning direction. The light in the main scanning direction and the sub-scanning direction is obtained based on the information on the light amount distribution obtained in the light quantity distribution obtaining step and the information on the light quantity distribution obtained in the light quantity distribution obtaining step. A calculation step of calculating the optical properties of Okukarada, with a, is characterized in that.

  In the present invention configured as described above, in the detection step, information on the amount of light emitted from the optical transmission body is detected in the region by the area sensor, so information on the amount of light is obtained only in one direction by the conventional line sensor. On the other hand, in the present invention, it is possible to obtain light quantity information in two dimensions. Therefore, by obtaining information on the two-dimensional light quantity for at least a part of the boundary line inclined by a predetermined angle with respect to the moving direction, the information on the two-dimensional light quantity is obtained in the main scanning direction and in the light quantity distribution obtaining step. It can be decomposed into information in the sub-scanning direction. Accordingly, since the optical characteristics of the optical transmission body in the main scanning direction and the sub-scanning direction can be obtained in a single inspection process, the optical characteristics can be easily inspected. In addition, since the optical characteristics of the optical transmission body in the main scanning direction and the sub-scanning direction can be inspected in a single inspection process, inspection can be performed even in the inspection of high-resolution optical transmission bodies that require inspection in both directions. It can be done in a short time.

In the present invention, preferably, the calculation step includes a Fourier transform step of obtaining optical characteristics of the optical transmission body related to the spatial frequency by performing Fourier transform on the light amount distribution information obtained in the light amount distribution acquisition step.
In the present invention configured as described above, since the calculation step includes a Fourier transform step, it is possible to obtain the optical characteristics of the optical transmission body related to the spatial frequency in the main scanning direction and the sub-scanning direction.

In the conventional inspection method, in order to obtain the optical characteristics of the optical transmission body for a predetermined spatial frequency, it is necessary to use a measurement pattern in which boundary lines are formed at intervals corresponding to the spatial frequency.
For this reason, in order to obtain optical characteristics for a plurality of spatial frequencies, a plurality of measurement patterns for each spatial frequency were prepared, and the inspection work was performed for each measurement pattern. Therefore, the inspection work was very complicated. .

  On the other hand, in the present invention, the optical characteristics of the optical transmission body related to the spatial frequency can be obtained by performing Fourier transform on the information of the light intensity distribution obtained in the light intensity distribution obtaining step, so that it corresponds to each spatial frequency. There is no need to perform the inspection work a plurality of times using the measured pattern. As described above, in the present invention, by performing the Fourier transform process, it is possible to obtain the optical characteristics of the optical transmission body for an arbitrary spatial frequency in a single inspection process. Can be done.

It is the schematic of the inspection apparatus of the optical transmission body by one Embodiment of this invention. It is a whole perspective view which shows the optical transmission body test | inspected with the inspection apparatus of the optical transmission body by one Embodiment of this invention. It is a figure which shows the pattern for a measurement of the inspection apparatus of the optical transmission body by one Embodiment of this invention. It is a figure which shows the light quantity distribution of the emitted light of the optical transmission body obtained by the inspection apparatus of the optical transmission body by one Embodiment of this invention. It is a figure which shows MTF with respect to the measurement position of the optical transmission body in the predetermined | prescribed spatial frequency obtained by the inspection apparatus of the optical transmission body by one Embodiment of this invention. It is a figure which shows MTF with respect to the spatial frequency in the predetermined measurement position of the optical transmission body obtained by the inspection apparatus of the optical transmission body by one Embodiment of this invention. It is a figure which shows the modification of the pattern for a measurement of the inspection apparatus of the optical transmission body of this invention. It is a figure which shows the inspection apparatus modification of the optical transmission body of this invention. It is a figure which shows another modification of the pattern for a measurement of the inspection apparatus of the optical transmission body of this invention. It is the schematic which shows the whole structure of the test | inspection apparatus by the Example of this invention. It is the schematic of the optical system part of the test | inspection apparatus by the Example of this invention. It is a figure which shows the result of the Example of this invention. It is a figure which shows the result of the Example of this invention. It is a figure which shows the result of the Example of this invention. It is a figure which shows the result of the Example of this invention. It is a figure which shows the result of the comparative example of this invention. It is a figure which shows the result of the comparative example of this invention. It is a figure which shows the result of the comparative example of this invention. It is a figure which shows the result of the comparative example of this invention.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a schematic view showing an entire optical transmission body inspection apparatus 1 according to an embodiment of the present invention.
As shown in FIG. 1, an optical transmission body inspection device 1 includes a light source 2, a detection unit 4 that is disposed to face the light source 2, detects the amount of inspection light from the light source 2, and the light source 2 and detection unit. 4 is provided with a transfer means 6 for transferring an optical transmission body, which is an object to be inspected, disposed along the scanning direction A, which is a moving direction.

  In the present embodiment, the rod lens array 8 is employed as the optical transmission body. FIG. 2 is a perspective view showing the entire rod lens array 8. The rod lens array 8 includes a large number of cylindrical rod lenses 12 which are formed into a rod shape by cutting an optical fiber having a refractive index distribution in a radial direction between two substrates 10 into a specific length. It is an integrated structure. Such a rod lens array 8 is used as an optical component for an image sensor used in a copying machine, a facsimile, a scanner, a hand scanner, or the like, or an LED printer or a liquid crystal element using an LED (light emitting diode) as a light source. It is used as a writing device in apparatuses such as liquid crystal printers and EL printers using EL elements. In the Honten-tei, the test rod lens array may be in a single row or in a plurality of rows.

  Returning to FIG. 1, the light source 2 includes an LED light source 14, a diffusion plate 16 disposed in front of the white LED light source 14, and a measurement pattern 18 disposed in front of the diffusion plate 16. In FIG. 1, the white LED light source 14, the diffuser plate 16, and the measurement pattern 18 are arranged with a space therebetween for the sake of explanation. It is arranged to be close. The light source 2 may be a white light source, but in order to obtain measurement data with monochromatic light, a combination of a white light source including a white LED and a color filter as the light source 2, or a monochromatic LED light source or other monochromatic light A means for obtaining light may be employed. Alternatively, a white light source may be used as the light source 2 and a color filter may be provided on the detection means 4 side to obtain measurement data with monochromatic light.

  FIG. 3 shows a measurement pattern 18 of the inspection apparatus 1 according to an embodiment of the present invention. In the measurement pattern 18, a light-shielding black region 20 and a transparent region 22 are formed by evaporating a light-shielding substance on a glass plate. The boundary line 24 between the black area 20 and the transparent area 22 is a constant “triangular wave” boundary line extending in the scanning direction A. That is, the boundary portion 24A, which is one hypotenuse composing each triangular peak of the “triangular wave”, is arranged at a predetermined angle α with respect to the scanning direction A, and the other hypotenuse side boundary portion 24A The continuous boundary portion 24B is arranged in the other direction with respect to the scanning direction A so as to form a predetermined angle β. In the present embodiment, the predetermined angle α and the predetermined angle β are set equal. In the present embodiment, the boundary line 24 represents the inclination of the boundary line 24 with respect to the moving direction A using an acute angle formed with respect to the moving direction A. Hereinafter, unless otherwise specified, the slope is expressed in the same manner as this.

  Here, the predetermined angles α and β detect the light amount distribution along the predetermined direction at the boundary line 24 sufficiently accurately in both the main scanning direction parallel to the scanning direction A and the sub-scanning direction orthogonal to the main scanning direction. Any angle can be used, and any angle can be adopted, but an angle of 30 ° or more and 60 ° or less is preferable. In the present embodiment, the predetermined angles α and β are set to 45 °.

  In addition, the length of the hypotenuse of the boundary portions 24A and 24B and the length of the base of each triangular wave 26 can be arbitrarily set. In this embodiment, the rod lens array 8 that is an object to be inspected is configured. One or more slopes of the triangular wave 26 with respect to the end surfaces (incident surfaces) of the two rod lenses 12 are set, and preferably, the dimensions are set such that a plurality of triangular waves 26 are arranged.

  Returning to FIG. 1, the detection unit 4 includes an area sensor 28 using a CCD camera, a CMOS camera, or the like, and an arithmetic processing unit 30 for processing the light quantity information obtained by the area sensor 28. The area sensor 28 is provided with a position adjustment mechanism (not shown) for adjusting the position with respect to the light source 2, that is, the height, the inclination, the distance from the light source 2, and the like.

  The transfer means 6 includes a stage 7 on which the rod lens array 8 is placed, and a position adjustment mechanism (not shown) for adjusting the height, inclination, distance from the light source 2 and the like of the stage 7 with respect to the light source 2. . The transfer means 6 includes a drive mechanism (not shown) that moves the stage 7 on which the rod lens array 8 is placed along the scanning direction A.

Next, a method for measuring MTF as an optical characteristic of the rod lens array 8 using the inspection apparatus 1 having such a configuration will be described.
The rod lens array 8 is placed on the stage 7 of the transfer means 6, and the rod lens array 8 is placed between the light source 2 and the detection means 4 so that both end faces of the rod lens 12 face the light source 2 and the detection means 4, respectively. Place. Light from the LED light source 14 is diffused by the diffusion plate 16 and irradiated to the rod lens array 8 through the measurement pattern 18. Here, the inspection light from the light source 2 becomes a pattern having a triangular wave-like boundary line corresponding to the measurement pattern 18 in which the black regions 20 and the transparent regions 22 are alternately arranged along the scanning direction A.

  Next, the area sensor 28 sequentially detects the light emitted from the light source 2 through each rod lens 12 while moving the stage 7 on which the rod lens array 8 is mounted along the scanning direction A by the driving mechanism. Then, a detection step for obtaining light quantity information is performed. As shown in FIG. 3, the area sensor 28 detects light quantity information for one or a plurality of regions 32 including one or both of the two boundary portions 24A and 24B inclined with respect to the scanning direction A. To do.

FIG. 4 shows a region 32 of the boundary line 24 of the measurement pattern 18 according to one embodiment of the invention.
Based on the light quantity information for the plurality of areas 32 obtained by the area sensor 28, the arithmetic processing unit 30 converts the light quantity information for the plurality of areas 32 into the main direction parallel to the scanning direction A as shown in FIG. A light quantity distribution acquisition step is performed in which the information on the scanning direction and the information on the sub-scanning direction orthogonal to the main scanning direction are decomposed to obtain the light quantity distribution in each direction. In this step, light quantity distribution data obtained by scanning at a plurality of locations on each slope is averaged to obtain a light quantity distribution. This is to eliminate the edge detection error of the slope due to the pixel pitch of the CCD camera or CMOS camera which is the light detection means 4. By averaging the information on the amount of light obtained in this way, it is possible to eliminate noise and the like generated during the inspection.

The arithmetic processing unit 30 performs a calculation step of calculating the MTF for each direction from the respective light quantity distributions obtained for the main scanning direction and the sub-scanning direction. The calculation step includes a Fourier transform step of Fourier transforming the light quantity distributions in the main scanning direction and the sub-scanning direction obtained for the region 32 including the boundary portion 24A.
FIG. 5 is a diagram showing the MTF with respect to the measurement position of the rod lens array 8 at a predetermined spatial frequency. FIG. 6 is a diagram showing the MTF with respect to the spatial frequency of the rod lens array 8 at a predetermined measurement position. By performing Fourier transform on each light quantity distribution in the calculation process by the arithmetic processing unit 30, MTFs in the main scanning direction and the sub-scanning direction are obtained for each measurement position and each spatial frequency as shown in these figures. .

According to the present embodiment configured as described above, the following excellent effects can be obtained.
Since the inspection apparatus 1 includes the measurement pattern 18 having the boundary portion 24A inclined by the predetermined angle α with respect to the scanning direction A, and the area sensor 28 obtains the light amount information about the region 32, the light amount information is subjected to the main scanning. By decomposing in the direction and the sub-scanning direction, it is possible to obtain light quantity information in both the main scanning direction and the sub-scanning direction. Therefore, it is possible to calculate MTFs for a plurality of spatial frequencies in both the main scanning direction and the sub-scanning direction in a single inspection process in which the emitted light is detected while moving the rod lens array 8 in the scanning direction A. This can simplify the inspection process even when measuring a high-resolution rod lens array 8 that requires inspection in both the main scanning direction and the sub-scanning direction with respect to a plurality of spatial frequencies. The inspection time can be shortened.

  In particular, in this embodiment, since the predetermined angle α is set to 45 °, the angle of the boundary portion with respect to the main scanning direction A and the sub-scanning direction B becomes equal. Therefore, when the information on the amount of emitted light is decomposed in the main scanning direction and the sub-scanning direction, the arithmetic processing unit 30 does not need to perform arithmetic processing in consideration of the difference in angle, so that the arithmetic processing is performed easily. Can do.

  Since the measurement pattern 18 includes the triangular wave-like boundary line 24 having the boundary portions 24A and 24B, a plurality of boundary portions 24A are formed in the scanning direction. The amount of light information can be detected.

  Since the arithmetic processing unit 30 performs Fourier transform on the obtained light quantity distribution information, the MTF for each spatial frequency can be calculated by a single inspection operation. In the conventional inspection apparatus, in order to inspect an optical transmission body having a desired resolution range, it is necessary to prepare a measurement pattern having a predetermined spatial frequency corresponding to the resolution range. Therefore, conventionally, when optical characteristics are inspected for a plurality of spatial frequencies, it is necessary to repeat the inspection process using the measurement patterns for each spatial frequency. In contrast, in the present embodiment, MTFs for a plurality of spatial frequencies can be obtained at a time by performing Fourier transform on the information on the light amount distribution, so that the inspection work can be greatly simplified, and the inspection time can be greatly reduced. Can be shortened.

The present invention is not limited to the above embodiment, and for example, a plurality of rod lens arrays may be inspected simultaneously. In this case, the rod lens arrays are arranged to overlap in the width direction, and as shown in FIG. 7, a measurement pattern 40 having a plurality of (two in FIG. 7) boundary lines 42 and 44 may be used. . At this time, the interval between the boundary lines 42 and 44 is set corresponding to the width direction dimension of the rod lens array.
In the above-described embodiment, the light amount information detection mainly for the region including the boundary portion 24A has been described. In the case of detection, if the predetermined angle α of the boundary portion 24A and the predetermined angle β of the boundary portion 24B are equal, the calculation process is facilitated when the light amount distribution information is decomposed in the main scanning direction and the sub-scanning direction.

  When the inspection apparatus inspects the optical characteristics of the light transmission body with respect to a specific color, a film of a specific color, for example, a red color, is interposed between the white LED light source 14 and the diffusion plate 16 as shown in FIG. 52 and a green film 54 may be provided. The detection means 56 may be provided with a drive mechanism (not shown) that moves the area sensor 28 along the scanning direction A. According to the inspection apparatus 50 having such a structure, it is possible to obtain the optical characteristics of the light transmission body related to red and the optical characteristics of the light transmission body related to green in one inspection operation.

  The measurement pattern is not limited to one having a triangular wave-like boundary line that is alternately inclined in the opposite direction with respect to the scanning direction. What is necessary is just to incline with a predetermined angle. Therefore, for example, as shown in FIG. 9, the measurement pattern 60 may have a straight boundary line 62 inclined at a predetermined angle with respect to the scanning direction A.

  Further, the measurement pattern may have a plurality of triangular wave-like boundary lines arranged in a direction orthogonal to the moving direction. According to this configuration, since the measurement pattern has a plurality of triangular wave boundaries in the direction orthogonal to the moving direction, a plurality of optical transmission bodies are arranged in the direction orthogonal to the moving direction, If the optical transmission bodies are moved together in the moving direction, the optical characteristics of a plurality of optical transmission bodies can be measured simultaneously. Therefore, since the optical characteristics of a plurality of optical transmission bodies can be inspected with a single inspection operation, the inspection efficiency can be improved.

  In the calculation step, the light quantity distribution information need not be Fourier transformed. In this case, as in the prior art, a measurement pattern in which boundary lines are formed at intervals corresponding to a desired spatial frequency may be prepared, and the MTF for this spatial frequency may be measured. Even in this case, the measurement pattern may be a pattern in which boundary lines inclined at a predetermined angle with respect to the scanning direction are arranged in a triangular wave shape at a predetermined interval as in the above-described embodiment. Alternatively, a straight boundary line inclined at a predetermined angle with respect to the angle may be arranged at a predetermined interval.

  The optical transmission body is not limited to the rod lens array, and may be any other lens such as a plate lens. Further, the optical transmission body is not limited to one in which a plurality of lenses are arranged to form an array, and may be a single lens.

[Example]
Next, in order to confirm the effect of the present invention, the following experiment was conducted.

Using the apparatus having the configuration of the present invention, the optical characteristics of the rod lens array as an optical transmission body were inspected. The overall configuration of the optical transmission body inspection apparatus used in this example will be described with reference to FIGS.
FIG. 10 is a schematic view showing an inspection apparatus 70 used in this embodiment, and FIG. 11 is a schematic view of an optical system portion of the inspection apparatus 70 shown in FIG. As shown in FIG. 10, the light source unit 72 of the inspection apparatus 70 includes light sources 74R, 74G, and 74B having wavelengths of R, G, and B, and a diffusion plate for diffusing light from the light sources 74R, 74G, and 74B. 76R, 76G, and 76B, and measurement patterns 78R, 78G, and 78B that receive the light from the diffusion plates 76R, 76G, and 76B.
The light detection unit 80 arranged to face the light source unit 72 is provided for each of the light sources 74R, 74G, and 74B (light detection units 80R, 80G, and 80B). The light detection unit 80 is connected to a personal computer 82, and the personal computer 82 processes information detected by the light detection unit 80.

  As shown in FIG. 11, the light source unit 72 and the light detection unit 80 are fixed to 6-axis stages 84 and 86, respectively, so that precise optical axis alignment is possible. The rod lens array 100 is fixed to the linear guide 88 by the vacuum suction unit 90, and the servo motor 92 (FIG. 10) is used to set the optical system of the rod lens lens 100 so that the middle between the light source unit 72 and the light detection unit 80 is located. While being moved in the vertical direction, the image detected by the light detector 80 through the measurement patterns 78R, 78G, 78B and the rod lens array 100 is taken into the personal computer 82 via the image board 94 (FIG. 10). The image captured by the personal computer 82 is an edge image including the boundary between the black region and the transparent region of the measurement patterns 78R, 78G, and 78B. These edge images are subjected to arithmetic processing such as Fourier transformation in the vertical direction (main scanning direction) and the horizontal direction (sub-scanning direction), and the MTF for each spatial frequency in each of the main scanning direction and the sub-scanning direction. Calculated. Such a method for evaluating the image quality of a lens from an edge image is a method generally called an “edge function method”.

  Using the inspection apparatus 70 as described above, the optical characteristics of the rod lens array 100 were inspected. The rod lens array 100 used in this example has a lens having a diameter of 0.343 mm sandwiched between substrates and is parallel to the width of 228 mm at a constant interval (the distance between the centers of adjacent rod lenses is 0.36 mm). They were arranged in a row and fixed with an adhesive, and the lens length was 4.4 mm and the lens conjugate length was 10 mm. Further, as the light detection unit 80, a 1/3 inch PS-CCD camera was used.

As the measurement patterns 78R, 78G, and 78B, the pattern shown in FIG. 3 in the above-described embodiment is used, where the angles α and β are both 45 °. The length of the bottom side of the triangular wave 26 is 0.6 mm.
Using the inspection device 70, RGB images are captured at a pitch of 0.3 mm in the width direction of the rod lens array 100, and calculation processing by the personal computer 82 results in 1 [Lp / mm] to 100 [Lp] for each image. MTF in the main scanning direction and sub-scanning direction at a spatial frequency up to / mm] was calculated at a time.

[Comparative example]
The same optical characteristics of the rod lens array 100 as in the example were measured by a conventional contrast method. As an inspection apparatus, a black and white line pattern having a boundary line in a direction orthogonal to the scanning direction and alternately having a light shielding area and a transparent area, instead of the measurement patterns 78R, 78G, and 78B of the optical system shown in FIG. It was used. Further, a line sensor is used as the light detection unit 80 instead of the CCD camera. As the line pattern, 4 [Lp / mm], 6 [Lp / mm], and 12 [Lp / mm] were prepared, and the line pattern was arranged so that the boundary line was orthogonal to the scanning direction.

Using such an apparatus, the sub-scanning direction of 4 [Lp / mm], the main scanning direction of 6 [Lp / mm], the main scanning direction of 12 [Lp / mm], and the sub-scanning direction of 12 [Lp / mm] Measurements were made in the scanning direction. In the measurement in the main scanning direction or the sub-scanning direction of 12 [Lp / mm], the line pattern was rearranged so that the boundary line of the line pattern was orthogonal to the scanning direction.
Other conditions are the same as in the example.

[Contrast of results of Example and Comparative Example]
12 to 15 show the relationship of the MTF with respect to the distance from the reference position in the embodiment. Here, FIG. 12 shows the sub-scanning direction of 4 [Lp / mm], FIG. 13 shows the main scanning direction of 6 [Lp / mm], and FIG. 14 shows the main scanning direction of 12 [Lp / mm]. FIG. 15 shows data in the sub-scanning direction of 12 [Lp / mm], both of which are for green (G) having a measurement wavelength of 521.5 mm.

  As shown in FIGS. 12 to 15, defects were observed at a distance of 140 mm from the reference position. The measurement for each spatial frequency and the measurement for the main scanning direction and the sub-scanning direction were obtained by one scan for one spatial frequency.

  On the other hand, FIGS. 16 to 19 show the relationship of the MTF to the distance from the reference position in the comparative example. 16 shows the sub-scanning direction of 4 [Lp / mm], FIG. 17 shows the main scanning direction of 6 [Lp / mm], and FIG. 18 shows the main scanning direction of 12 [Lp / mm]. FIG. 19 shows data taken in the sub-scanning direction of 12 [Lp / mm], both of which are for green (G) with a measurement wavelength of 521.5 mm.

  As shown in FIGS. 16 to 19, in the sub-scan of 4 [Lp / mm], a defect was observed at a distance of 140 mm from the reference position, but this defect was not observed in other data. The reason is that the contrast method does not observe a defect whose period exactly overlaps with the interval between the black and white line patterns. Further, in order to take these four data, it is necessary to measure by rotating the direction of the monochrome line pattern in the respective main scanning and sub-scanning directions or by exchanging the line pattern for each spatial frequency. It took many times longer than the example.

  As described above, according to the present invention, it was confirmed that the optical characteristics of the optical transmission body in the main scanning direction and the sub-scanning direction can be easily measured, and the inspection time can be shortened.

DESCRIPTION OF SYMBOLS 1 Inspection apparatus 2 Light source 4 Detection means 8 Rod lens array 12 Rod lens 18 Measurement pattern 20 Black area 22 Transparent area 24 Boundary line 28 Area sensor 32 Area

Claims (6)

A light source provided with a measurement pattern; and a detecting means arranged to face the light source, and injecting inspection light from the light source into the optical transmission body while moving the optical transmission body in one direction. An inspection device for an optical transmission body that inspects optical characteristics of the optical transmission body by detecting emitted light with the detection means,
The measurement pattern includes a light shielding region and a transparent region, and at least a part of a boundary line between the light shielding region and the transparent region is inclined at a predetermined angle with respect to a moving direction of the optical transmission body, and the detection The means includes an area sensor that detects a light amount of the emitted light for a region including at least a part of the inclined boundary line.
An inspection device for an optical transmission body characterized by the above.   The optical transmission body inspection apparatus according to claim 1, wherein the predetermined angle is an acute angle formed by the boundary line and the moving direction, and is 30 to 60 °.   The optical transmission body inspection apparatus according to claim 2, wherein the predetermined angle is 45 °.   The measurement pattern has a triangular wave-shaped boundary line along the moving direction, in which the boundary lines inclined by the predetermined angle in opposite directions to the moving direction are alternately continued. 4. The optical transmission body inspection apparatus according to any one of 3 above. While moving the light transmission body in one direction, the light transmission body is irradiated with light from the light source through a measurement pattern having a light shielding area and a transparent area where at least a part of the boundary line is inclined at a predetermined angle with respect to the movement direction. And a detection step of detecting, by an area sensor, information on the amount of light emitted from the optical transmission body for a region including at least a part of the boundary line inclined,
Light quantity distribution acquisition that obtains light quantity distribution information in the main scanning direction and the sub-scanning direction by decomposing light quantity information into light quantity components in the main scanning direction parallel to the moving direction and the sub-scanning direction orthogonal to the main scanning direction Process,
A calculation step of calculating optical characteristics of the optical transmission body in the main scanning direction and the sub-scanning direction based on the information of the light amount distribution obtained in the light amount distribution acquisition step,
An inspection method for an optical transmission body characterized by the above. The calculation step includes a Fourier transform step of obtaining optical characteristics of the optical transmission body related to a spatial frequency by performing Fourier transform on the information of the light amount distribution obtained in the light amount distribution acquisition step.
The optical transmission body inspection method according to claim 5.

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