阅读说明：本技术 光照射装置、光学评估装置和物品制造方法
(Light irradiation apparatus, optical evaluation apparatus, and article manufacturing method
) 是由 植村卓典 于 2019-07-03 设计创作，主要内容包括：本公开内容涉及光照射装置、光学评估装置和物品制造方法。一种用于用光照射物体的光照射装置,包括：多个线状遮光器,其以预定的中心至中心间隔布置,并且被配置为至少部分地阻挡光；以及多个线状光照射器,其被布置为与多个遮光器中的一些重叠,以便用光照射物体。多个光照射器被布置为形成不小于多个遮光器的中心至中心间隔的两倍的周期。(The present disclosure relates to a light irradiation apparatus, an optical evaluation apparatus, and an article manufacturing method. A light irradiation device for irradiating an object with light, comprising: a plurality of linear shutters arranged at predetermined center-to-center intervals and configured to at least partially block light; and a plurality of linear light irradiators arranged to overlap some of the plurality of shutters so as to irradiate the object with light. The plurality of light irradiators are arranged to form a period not less than twice a center-to-center spacing of the plurality of shutters.)
1. A light irradiation apparatus for irradiating an object with light, comprising:
a plurality of line-shaped shutters arranged at predetermined center-to-center intervals and configured to at least partially block light; and
a plurality of light irradiators in a line shape arranged to overlap some of the plurality of shutters so as to irradiate the object with light,
wherein the plurality of light irradiators are arranged to form a period of not less than twice a center-to-center spacing of the plurality of shutters.
2. The apparatus of claim 1, wherein the plurality of light illuminators are arranged to form a plurality of periodic elements arranged with the period as a center-to-center spacing, and each of the plurality of periodic elements includes the same number of light illuminators.
3. The apparatus of claim 2, wherein the number is not less than 2, and a center-to-center spacing of light illuminators in each of the plurality of periodic elements is equal to a center-to-center spacing of the plurality of shutters.
4. The apparatus of claim 2, wherein let n be the number, PmIs the center-to-center spacing of the plurality of shutters, and PoIs the period, then
1/4≤(n×Pm)/Po≤3/4。
5. The apparatus of claim 1, wherein a width of each of the plurality of light illuminators is no greater than a width of each of the plurality of shutters.
6. The apparatus according to claim 1, wherein a long side direction of each of the plurality of shutters and a direction in which the plurality of shutters are arranged are perpendicular to each other.
7. The apparatus of claim 1, further comprising a light-transmissive plate member,
wherein the plurality of shutters and the plurality of light irradiators are arranged on a main surface of the plate member.
8. The apparatus of claim 7, wherein the plurality of light illuminators are disposed between the major surface and a shutter of the plurality of shutters that is: the shutters are arranged such that the plurality of light irradiators overlap the shutters.
9. The apparatus of claim 8, further comprising a light source configured to illuminate an end face of the plate member with light.
10. The apparatus of claim 1, wherein a thickness of the plurality of light illuminators is less than a center-to-center spacing of the plurality of shutters.
11. An optical evaluation device, comprising:
the light irradiation device according to claim 1;
an imager configured to image an object irradiated with light by the light irradiation device through an opening between the plurality of shutters;
a driver configured to move the plurality of shutters and the plurality of light irradiators in a direction intersecting a long side direction of each of the plurality of shutters; and
an image processor configured to evaluate the object based on the plurality of images captured by the imager.
12. The apparatus of claim 11, wherein the imager performs imaging in a state where the driver is moving the plurality of shutters and the plurality of light irradiators.
13. The apparatus of claim 12, wherein
The plurality of light irradiators are arranged to form a plurality of periodic elements arranged with the period as a center-to-center interval, and each of the plurality of periodic elements includes the same number of light irradiators, an
Let n be the number, PmIs the center-to-center spacing of the plurality of shutters, and PoIn order to be the period of time,
the distance that the driver moves the plurality of shutters and the plurality of light illuminators during the exposure period of the imager is less than Po-(n×Pm)。
14. A method of manufacturing an article, comprising:
evaluating an article by using the optical evaluation device of claim 11; and
processing corresponding to the evaluation result of the article is performed.
Technical Field
The invention relates to a light irradiation apparatus, an optical evaluation apparatus, and an article manufacturing method.
Background
Japanese patent No. 5994419 describes an inspection apparatus that images an object to be inspected while irradiating the object with light having periodically varying luminance, calculates amplitude values of periodic luminance variations and the like of the obtained image, and detects defects by using the amplitude values and the like. In the inspection apparatus described in japanese patent No. 5994419, an illumination device for illuminating an object to be inspected with light displays stripe pattern light on a display device such as an LCD, and illuminates the object with the stripe pattern light. Alternatively, the illumination apparatus projects stripe-pattern light onto a screen by using a projector, and irradiates an object to be inspected with the stripe-pattern light reflected by the screen.
An optical evaluation apparatus such as the inspection apparatus described in japanese patent No. 5994419 uses an illumination device including a display device such as an LCD or an illumination device including a projector and a screen, and such an illumination device is a non-transmissive device which is opaque to light. Therefore, in order to image a stripe pattern formed on an object to be inspected by using an imaging device, an illumination device must be arranged so as not to block the field of view of the imaging device, which may increase the size of the optical evaluation apparatus. Especially when the inspection target area of the object to be inspected is a curved surface, a large illumination device is required to image the regularly reflected light from the entire inspection target area at once. This may cause a problem that the size of the optical evaluation device is further increased.
Disclosure of Invention
The present invention provides a technique advantageous for reducing the size of an optical evaluation apparatus.
According to a first aspect of the present invention, there is provided a light irradiation device for irradiating an object with light, the light irradiation device comprising: a plurality of linear shutters arranged at predetermined center-to-center intervals and configured to at least partially block light; and a plurality of linear light irradiators arranged to overlap some of the plurality of shutters so as to irradiate the object with light, wherein the plurality of light irradiators are arranged to form a period not less than twice a center-to-center interval of the plurality of shutters.
According to a second aspect of the present invention, there is provided an optical evaluation device comprising: the light irradiation device as defined in the first aspect of the invention; an imager configured to image the object irradiated with the light by the light irradiation device through an opening between the plurality of shutters; a driver configured to move the plurality of shutters and the plurality of light irradiators in a direction intersecting a long side direction of each of the plurality of shutters; and an image processor configured to evaluate the object based on the plurality of images captured by the imager.
According to a third aspect of the present invention, there is provided an article manufacturing method comprising: evaluating the article by using the optical evaluation device as defined in the second aspect of the invention; and executing processing corresponding to the evaluation result of the article.
Further features of the invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
Drawings
Fig. 1A and 1B are diagrams showing the arrangement of a light irradiation device of an embodiment of the present invention;
fig. 2 is a diagram showing the arrangement of an optical evaluation device of an embodiment of the present invention;
fig. 3A to 3D are diagrams for explaining the effect of exposure by the imaging apparatus while scanning the light irradiation device;
FIG. 4 is a flow chart illustrating operation of an optical evaluation device of an embodiment of the present invention; and
FIG. 5 is a graph showing center-to-center spacing P of a plurality of periodic elementsoCenter-to-center spacing P from a plurality of shuttersmRatio (P) ofo/Pm) Graph of the relationship with the non-uniformity of the image intensity.
Detailed Description
The invention will be explained below by means of exemplary embodiments thereof with reference to the drawings.
Fig. 1A and 1B schematically show the arrangement of a light irradiation device 10 of an embodiment of the present invention. The light irradiation device 10 is configured to irradiate the object 11 with light. Fig. 1A is a diagram illustrating the light irradiation device 10 viewed from the object 11 to be irradiated with light by the light irradiation device 10. Fig. 1B is a sectional view or a side view of the light irradiation device 10.
The light irradiation device 10 includes a plurality of shutters 101 and a plurality of light irradiators 102. The plurality of shutters 101 are configured to at least partially block light. In other words, the light transmittance of the plurality of shutters 101 is less than 100%. Preferably, the light transmittance of the plurality of shutters 101 is less than 10%. A plurality of shutters 101 are arranged at predetermined center-to-center intervals P in the X directionmA plurality of linear shutters arranged. The longitudinal direction of each shutter 101 is a direction intersecting the X direction, for example, the Y direction. Note that the Y direction is perpendicular to the X direction. The plurality of light irradiators 102 are a plurality of linear light irradiators arranged to overlap some of the plurality of shutters 101 so as to irradiate the object 11 with light. Width (in X direction) W of each light illuminator 102LIIs equal to or smaller than the width (in the X direction) W of each shutter 101LB。
An opening 107 as a light transmitter that transmits light is formed between adjacent shutters 101 in the plurality of shutters 101. A plurality of openings 107 at center-to-center intervals PmAnd (4) arranging. An imager (described later) may image the object 11 through the plurality of openings 107. The shutters 101 and the openings 107 are alternately arranged.
As described above, the center-to-center intervals of the plurality of shutters 101 in the X direction are Pm. This is equivalent to arranging a plurality of shutters 101 to form a period P in the X directionm. The plurality of light irradiators 102 are arranged to form a period P in the X directionoPeriod PoIs the center-to-center spacing P of a plurality of shutters 101mMore than twice as much. The plurality of light irradiators 102 form a plurality of periodic elements 103 arranged to have a period P as a center-to-center intervalo. Each periodic element 103 is formed by the same number of light irradiators 102. When the number of light irradiators 102 forming each periodic element 103 is 2 or more, the center-to-center interval of the light irradiators 102 in each of the plurality of periodic elements 103 is equal to the center-to-center interval P of the plurality of shutters 101m。
Width (in X direction) W of periodic element 103oIs defined as the center-to-center spacing of two openings 107 adjacent to the outer sides of two outermost light irradiators 102 included in the periodic elements 103 (two light irradiators 102 that are most spaced apart from each other in one periodic element 103). Let n be the number of light irradiators 102 forming each periodic element 103, PmIs the center-to-center spacing of the plurality of shutters 101, Wo＝n×PmThis is true.
In the example shown in fig. 1A and 1B, each of the plurality of periodic elements 103 includes two light illuminators 102. Further, in the example shown in fig. 1A and 1B, two shutters 101 are arranged between adjacent periodic elements 103 in the plurality of periodic elements 103. Further, in the example shown in fig. 1A and 1B, the center-to-center spacing or period P of the plurality of periodic elements 103oIs center to center of the plurality of shutters 101Heart interval or period PmAnd the width W of each periodic element 103oIs the center-to-center spacing or period P of the plurality of shutters 101mTwice as much.
The light irradiation device 10 further includes a light transmissive plate member 104, and a plurality of shutters 101 and a plurality of light irradiators 102 may be arranged on the main surface PS of the plate member 104. The plurality of light irradiators 102 may be arranged between the main surface PS and the light chopper 101 of the plurality of light choppers 101 arranged such that the plurality of light irradiators 102 overlap therewith. In the orthographic projection (plan view) of the main surface PS, the light irradiators 102 may be arranged so as not to extend from the shutters 101 which the light irradiators 102 overlap. In other words, the width of each of the plurality of light irradiators 102 may be equal to or less than the width of each of the plurality of shutters 101.
As an example, the plurality of light irradiators 102 may be made of white pigment, and the plurality of shutters 101 may be made of black pigment. The plurality of light irradiators 102 may be formed by applying a white pigment in the form of a line on the plate member 104, and the plurality of shutters 102 may be formed by applying a black pigment in the form of a line. These pigments may be applied by using well known techniques such as screen printing or ink jet printing.
The light irradiation device 10 may be manufactured as follows: a plate member 104 on which a plurality of light irradiators 102 are printed and a substrate on which a plurality of shutters 101 are printed are prepared, and the plate member 104 and the substrate are stacked so that the light irradiators 102 and the shutters 101 overlap each other. The light irradiation device 10 may be manufactured as follows: the light chopper 101 and the light irradiator 102 are printed on another transparent plate member, and the other plate member is arranged on the plate member 104. The light irradiation device 10 may be manufactured as follows: a plurality of light irradiators 102 formed of a transparent organic EL display or the like and a plurality of light shields 101 formed of a metal plate having a plurality of linear openings 107 are stacked.
The plurality of shutters 101 and the plurality of light irradiators 102 may also be formed by a method other than the method using a pigment. For example, the plurality of shutters 101 may be formed of a metal deposited film of aluminum, chromium, or the like. The light irradiator 102 may also be obtained by forming a concave-convex structure or a stain-polished structure on the main surface PS of the plate member 104 by, for example, laser treatment or sand blast treatment.
The light irradiation device 10 may further include a light source 106 for irradiating the end face (side surface) of the plate member 104 with light. In one example, the plate member 104 may be held by the holding frame 105, and the light source 106 may be incorporated into the holding frame 105. The light source 106 may include, for example, a Light Emitting Diode (LED), a Laser Diode (LD), or a halogen lamp. Light emitted from the light source 106 enters the plate member 104 through the end face of the plate member 104, and propagates inside the plate member 104 while being totally reflected. That is, the plate member 104 functions as a light guide plate.
A part of the light propagating inside the plate member 104 is scattered by the plurality of light irradiators 102 formed on the plate member 104. Light scattered in the direction opposite to the object 11 (the positive direction of the Z axis) when viewed from the plate member 104 is blocked by being absorbed or reflected by the shutter 101. This prevents light from irradiating the imager arranged in the opposite direction to the object 11 when viewed from the plate member 104, when viewed from the plate member 104. To accomplish this, the width (in the X direction) W of each light illuminator 102LIPreferably equal to or less than the width (in the X direction) W of each shutter 101LBAnd more preferably less than WLB. The width of each light illuminator may also be 80% (inclusive) to 95% (inclusive) of the width of each light shutter.
The object 11 is irradiated with light that is scattered by the plurality of light irradiators 102 and output from the plate member 104 toward the object 11. Accordingly, a light intensity distribution or image corresponding to the arrangement of the plurality of light irradiators 102 is formed on the surface of the object 11.
When the light irradiator 102 is formed of a pigment, the thickness of the light irradiator 102 may be several micrometers or more in order to irradiate the object 11 with sufficiently strong light. On the other hand, if the thickness of the light irradiator 102 is too large, the position of the shutter 101 overlapping with the light irradiator 102 becomes distant from the plate member 104. This excessively increases the difference between the height of the shutter 101 disposed on the light irradiator 102 and the height (distance from the main surface PS) of the shutter 101 disposed on a portion where the light irradiator 102 is not formed. At this pointIn this case, the widths of the plurality of shutters 101 viewed from the imager become uneven. Accordingly, the thickness of the plurality of light irradiators 102 is preferably less than the center-to-center spacing P of the plurality of shutters 101m。
Fig. 2 shows the arrangement of an optical evaluation device 1 of an embodiment of the present invention. The optical evaluation apparatus 1 includes a light irradiation device 10 as a constituent member (light irradiation apparatus), and optically evaluates an object 11. The object 11 has, for example, a glossy surface. The object 11 may be, for example, a metal member or a resin member having a polished surface. Various defects such as scratches, color loss, and dents may exist at or near the surface of the object 11.
The optical evaluation apparatus 1 can detect a defect on the surface of the object 11 by obtaining an image of a region to be inspected of the object 11 and evaluating a processed image obtained by processing the image. Further, the optical evaluation device 1 may classify the object 11 as, for example, a non-defective product or a defective product based on the defect detection result. Although not shown, the optical evaluation apparatus 1 may include a conveying device (not shown) for conveying the object 11 to a predetermined position (for example, a conveyor, a robot, a slider, or a manual stage).
The optical evaluation device 1 may include: a light irradiation device 10 for illuminating the object 11 by irradiating the object 11 with light; and an imager (camera) 12 for imaging the object 11 via the light irradiation device 10. The imager 12 images the object 11 through a plurality of openings 107 between the plurality of shutters 101. The imager 12 may include: an image sensor (area sensor) in which a plurality of pixels are two-dimensionally arranged, such as a CCD image sensor or a CMOS image sensor; and an optical system that forms an image of the object 11 on an imaging plane of the image sensor. By not using a line sensor but using an area sensor, a wide range of the object 11 can be quickly evaluated.
The optical evaluation device 1 comprises a drive 13. The driver 13 moves the light irradiation device 10 (the plurality of shutters 101 and the plurality of light irradiators 102) in a direction (generally, X direction) intersecting the longitudinal direction (Y direction) of each of the plurality of shutters 101. In this example shown in fig. 2, the driver 13 moves the entire light irradiation device 10. However, when the plurality of shutters 101 and the plurality of light irradiators 102 are formed on the movable member, the driver 13 may also move only the movable member.
The optical evaluation device 1 may further comprise a controller 14. The controller 14 may be a PLD (programmable logic device) such as an FPGA (field programmable gate array), an ASIC (application-specific integrated circuit), a general-purpose or special-purpose computer with a program installed, or a combination of all or part thereof. The controller 14 causes, for example, the light irradiation device 10, the imager 12, and the driver 13 to operate in synchronization with each other. For example, the controller 14 controls the driver 13 so that the light irradiation device 10 moves at a predetermined speed while sending a trigger signal to the imager 12 at predetermined time intervals, thereby causing the imager 12 to capture N images (N ≧ 3). However, the configuration is not limited thereto. For example, it is also possible to move the light irradiation device 10 by manually operating the driver 13 and cause the imager 12 to perform imaging by a manual trigger.
The optical evaluation device 1 may further comprise an image processor 15 and a display 16. Image processor 15 evaluates object 11 based on a plurality (N) of images captured by imager 12. The image processor 15 and the controller 14 may also be integrated. The image processor 15 may be, for example, a general-purpose or special-purpose computer with a program installed therein. The image captured by the imager 12 may be transmitted to the image processor 15 through a transmission path such as a cable or a communication path (not shown).
An imaging period (exposure period) in which the imager 12 performs imaging is set within a moving period in which the driver 13 moves the light irradiation device 10. In other words, the imager 12 performs imaging in a state where the driver 13 moves the light irradiation device 10. The exposure period is a period in which charges generated by photoelectric conversion by the imager 12 are accumulated, that is, a charge accumulation period. Such an operation is advantageous in reducing the period P having a larger period than the plurality of periodic elements 103 in the frequency component formed by the plurality of shutters 101 and the plurality of periodic elements 103oShort periodic frequency components (higher order frequency components). The reason will be explained below with reference to fig. 3A to 3D.
FIG. 3A shows a view from the imager 12 in a state where the light irradiation device 10 is stationaryThe observed transmittance distribution of the plurality of shutters 101. The abscissa represents an X coordinate, and the ordinate represents the transmittance (equivalent to the light amount (time-integrated value of luminance) during the exposure period of the imager 12). The transmittance distribution has a rectangular waveform because the plurality of line-shaped light shields 101 are spaced at a center-to-center interval (period) PmAnd (4) arranging.
FIG. 3B shows the imager 12 at PmThe transmittance distribution (solid line) of the plurality of shutters 101 observed by the imager 12 at the time of continuing exposure while scanning the light irradiation device 10. The abscissa represents an X coordinate, and the ordinate represents the transmittance (equivalent to the light amount (time-integrated value of luminance) during the exposure period of the imager 12). For comparison, fig. 3B shows the transmittance distribution of fig. 3A with a dotted line. Due to the presence of PmThe exposure of the imager 12 is continued while the light irradiation device 10 is scanned, and therefore the transmittance distribution of the plurality of shutters 101 observed by the imager 12 is smooth, thereby forming a trapezoidal distribution having almost uniform transmittance on the upper side.
Fig. 3C shows the luminance distribution of the plurality of light irradiators 102 observed by the imager 12 in a state where the light irradiation device 10 is stationary. The abscissa represents an X coordinate, and the ordinate represents luminance (equivalent to the light amount (time-integrated value of luminance) during the exposure period of the imager 12). The luminance distribution has a rectangular waveform having irregular intervals because the plurality of linear light irradiators 102 are arranged to form the period Po。
FIG. 3D shows the imager 12 at PmThe luminance distribution (solid line) of the plurality of light irradiators 102 observed by the imager 12 at the time of continuing exposure while scanning the light irradiation device 10. The abscissa represents an X coordinate, and the ordinate represents luminance (equivalent to the light amount (time-integrated value of luminance) during the exposure period of the imager 12). For comparison, fig. 3D shows the transmittance distribution of fig. 3C with a dotted line. Since the imager 12 is at PmThe imaging continues while the light irradiation device 10 is scanned, and therefore the brightness distribution of the plurality of light irradiators 102 observed by the imager 12 is also smooth. However, the luminance distribution is not a single trapezoid but has a trapezoidal waveform because of the plurality of light irradiators 102 (a plurality of periodic elements)103) Period P of formationoGreater than the interval P of the plurality of shutters 101m(in this example, PoIs PmFour times greater).
As described above, when the imager 12 performs imaging while the light irradiation device 10 is stationary, the transmittance distribution of the plurality of shutters 101 and the luminance distribution of the plurality of light irradiators 102 (the plurality of periodic elements 103) (both of which are observed through the imager 12) include the period PmThe frequency component of (a). On the other hand, when the imager 12 performs imaging while the light irradiation device 10 is scanned, the period P may be reducedmI.e., higher order frequency components. By thus reducing the high-order frequency components, the uniformity of luminance (pixel value) in a processed image (explained later) can be improved.
FIGS. 3A-3D show the imager 12 at PmThe transmittance distribution of the plurality of shutters 101 and the luminance distribution of the plurality of light irradiators 102 observed through the imager 12 while continuing exposure while scanning the light irradiation device 10. However, this is merely an example, and it is not necessary to make the moving amount of the light irradiation device 10 during the imaging period (exposure period) of the imager 12 equal to Pm. The amount of movement of the light irradiation device 10 during the imaging period (exposure period) is desirably smaller than the center-to-center intervals P of the plurality of periodic elements 103oAnd width WoDifference P betweeno-Wo(i.e., P)o-(n×Pm)). This is because if the amount of movement of the light irradiation device 10 during the imaging period is larger than Po-WoThen, a high-contrast image (waveform) cannot be obtained in the luminance distribution of the plurality of light irradiators 102 (the plurality of periodic elements 103).
In order to further reduce the higher-order frequency components, it is advantageous that the imager 12 has a function (overlapping function) capable of performing imaging (exposure) and image transmission in parallel. The imager 12 having the overlapping function can perform imaging even during the time required for transferring the image, and thus a higher smoothing effect can be obtained.
When the number of the light irradiators 102 forming each of the plurality of periodic elements 103 is 2 or more, the light forming each periodic element 103 is irradiatedThe device 102 is expected to have a period PmAnd (4) arranging. That is, each periodic element 103 is desirably formed with a period PmN light irradiators 102 arranged in series. This is to avoid generation of undesired frequency components (except for the period P) in the luminance distribution of the light irradiator 102 when the imager 12 continues exposure while scanning the light irradiation device 10oFrequency components other than those). The undesired frequency components may adversely affect the processed image as will be explained below.
Further, the width Wo(i.e., n × P)m) Period P of a plurality of periodic elements 103oRatio (W) ofo/Po) The (duty cycle) is preferably from 1/4 (inclusive) to 3/4 (inclusive). That is, it is preferable that 1/4 ≦ (n × P) is satisfiedm)/PoThe condition is less than or equal to 3/4. This is because undesirable frequency components (other than the period P) observed by the imager 12 that are generated in the luminance distribution of the plurality of light illuminators 102 if this condition is satisfiedoFrequency components other than these) are sufficiently small. From the same viewpoint, the duty ratio (W) of the plurality of shutters 101LB/Pm) And the duty cycle (W) of the plurality of light illuminators 102LI/Pm) Preferably 40% or less or 60% or more. Note that if the duty cycle is increased, the resolution may be reduced because the shutter 101 blocks a portion of the pupil of the optical system of the imager 12. When this is taken into consideration, the duty ratios (W) of the plurality of shutters 101LB/Pm) And the duty cycle (W) of the plurality of light illuminators 102LI/Pm) Preferably 40% or less.
Fig. 4 shows a procedure of the inspection method performed by the optical evaluation apparatus 1. The controller 14 controls the inspection method. An example of inspecting defects on the surface of the object 11 will be explained with reference to fig. 4. First, in step S11, the controller 14 causes the driver 13 to start scanning (moving) the light irradiation device 10. In step S12, the controller 14 causes the light irradiation device 10 to emit light (to irradiate the object 11 with light) while the driver 13 scans the light irradiation device 10, and causes the imager 12 to perform imaging. Thus, the imager 12 captures the ith image Ii(x, y). This operation is repeated until i becomes 1 to N, resulting in capturing a total of N (N ≧ 3) images. (x)And y) indicates the position (coordinate value) of a pixel in an image.
In step S14, the controller 14 causes the driver 13 to stop scanning the light irradiation device 10. In step S15, the controller 14 causes the image processor 15 to process the N images obtained by repeating step S12 and generate processed images for detecting defects. In step S16, the controller 14 detects a defect on the surface of the object 11 based on the processed image obtained in step S15.
An example of processing an image is with a shift of 2 π △ Xi/PoAmplitude image of frequency component of phase of radian △ Xi( i 1, 2.., N) is the position of the light irradiation device 10 with respect to the reference position when the i-th image is captured when the position of the light irradiation device 10 is △ XiThe phase of the plurality of periodic elements 103 is set to 2 π △ Xi/PoRadian indicates when the light irradiation device 10 emits light at a predetermined light amount while scanning and the imager 12 performs imaging (exposure), △ XiIs the average position of the light illuminating device 10 during the exposure period △ XiHowever, since the phases that differ from each other by an integer multiple of 2 π have the same value, they may be at △ Xn≠△Xm+nPoIs imaged in the position of the light irradiation device 10.
When having P at the position of the light irradiation device 10oWhen N images are captured at intervals of/N, △ XiRepresented by equation (1) (where the position at which the first image is captured is the reference position):
ΔXi＝(Po/N)×(i-1) ...(1)
in this case, the amplitude image a (x, y) can be calculated from equation (2):
when the light irradiation device 10 is moved, the images of the plurality of light irradiators 102 reflected on the surface of the glossy object 11 are moved, and thus the luminance of incident light is changed in each pixel of the imager 12. In a portion having normal gloss on the surface of the object 11, the luminance greatly changes when the light irradiation device 10 moves, and thus the amplitude value of the luminance increases. On the other hand, a portion having scattering defects such as scratches and surface roughness generates scattered light in addition to specular reflected light. When light is scattered on the surface of the object 11, the images of the plurality of light irradiators 102 reflected on the surface are blurred, and thus the contrast difference in intensity is reduced, and the amplitude value is also reduced. For example, on a perfectly diffuse surface, the angular distribution of scattering of light is no longer dependent on the angle of the incident light. Therefore, even when a plurality of light irradiators 102 project a trapezoidal waveform pattern onto the object 11, the luminance is always constant regardless of the position of the light irradiation device 10, and thus the amplitude becomes zero. Therefore, in the amplitude image, the normal portion is visualized as bright, and the defective portion is visualized as dark. This makes it possible to evaluate the degree of scattering as a surface characteristic in the amplitude image and obtain information on scattering defects such as scratches and surface roughness.
Another example of processing an image is a phase image. The phase image θ (x, y) can be calculated by equation (3):
in the formula (3), the phase is calculated as a value from-pi to pi. Therefore, if the phase change is larger than this, discontinuous phase jumps occur in the phase image. If this is the case, phase connection (phase unwrapping) is required.
In the phase image, the surface inclination of the object 11 can be evaluated as a surface characteristic. Therefore, in the phase image, information of defects caused by gentle shape changes such as dents, surface tangle errors, and surface depressions in the phase image can be obtained.
Various algorithms for phase connection (phase unwrapping) have been proposed, but if the image is noisy, thenAs a method of avoiding phase connection, a phase difference (corresponding to a differential of a phase) may be calculated instead of the phase difference △ θx(x, y) and △ θy(x, y) can be calculated from equation (4):
yet another example of processing an image is averaging the image. Average image Iave(x, y) can be calculated from equation (5):
in the average image, the reflectance distribution can be evaluated as a surface characteristic. Therefore, in the average image, information of defects having a reflectance different from that of a normal portion, such as color loss, stains, and absorption of foreign substances, can be obtained.
As described above, the optically evaluable surface characteristics vary depending on the processed image. Therefore, since the defect to be visualized also changes between the processed images, various defects can be visualized in the processed images by combining the processed images.
Fig. 3B and 3D depict transmittance distributions of the plurality of shutters 101 and luminance distributions of the plurality of light irradiators 102 observed by the imager 12 when the imager 12 continues imaging while scanning the light irradiation device 10. However, the positions of the plurality of shutters 101 and the plurality of light irradiators 102 are not independent of each other. Therefore, strictly speaking, an image obtained by performing exposure while scanning the light irradiation device 10 is not a product of the transmittance distribution of the plurality of light irradiators 102 shown in fig. 3B and the luminance distribution of the plurality of light irradiators 102 shown in fig. 3D. As a result, the image contains higher order frequency components. Therefore, even in a normal region of the object 11, periodic intensity unevenness occurs in the average image, the amplitude image, and the phase image. If the intensities (pixel values) of these images have unevenness, the detection accuracy of the defect on the surface of the object 11 may be lowered.
FIG. 5 shows the center-to-center spacing P relative to a plurality of periodic elements 103oCenter-to-center spacing P from a plurality of shutters 101mRatio (P) ofo/Pm) The calculation result of the nonuniformity of intensity (pixel value) generated on the image. When P is in the two-logarithmic grapho/PmAs it increases, the intensity non-uniformity decreases linearly. Therefore, when the light irradiator 102 (P) is formed in all the shutters 101o＝Pm) When the intensity of the light beam is changed, a large intensity unevenness appears on the image. In addition, in order to improve image uniformity, it is preferable to increase P as much as possibleo/Pm. Thus, the center-to-center spacing P of the plurality of periodic elements 103oPreferably the center-to-center spacing P of the plurality of shutters 101mMore preferably 8 times or more.
On the other hand, if the center-to-center spacing P of the plurality of shutters 101mExcessively decreased, the diffraction of light blurs the image and the resolution is decreased. Let λ be the wavelength of light to be emitted by the light irradiation device 10, the angle θ of the first-order diffracted light obtained by the shutter 101 is represented by equation (6):
let D be the distance between the surface on which the plurality of shutters 101 are arranged and the surface of the object 11, the first-order diffracted light produces a blur of 2Dtan θ on the surface of the object 11. Let B be an allowable blur amount, the center-to-center intervals P of the plurality of shutters 101mMust be greater than (2D lambda/B).
On the other hand, if Po/PmLarge and PmIs also large, the center-to-center spacing P of the plurality of periodic elements 103oThe value of (c) also increases. In this case, the distance that the driver 13 moves the light irradiation device 10 increases, which may increase the size of the optical evaluation device 1. In addition, if the center-to-center spacing P of the plurality of periodic elements 103oLarge, scattering defects with a low degree of scattering (high directionality) in the amplitude image become difficult to detect in the phase image. Even when P iso/PmWhen the increase is excessive, the intensity unevenness of the image is also hidden in noise or the like and is not improved. Thus, the center-to-center spacing P of the plurality of periodic elements 103oPreferably the center-to-center spacing P of the plurality of shutters 101mLess than 256 times.
[ example 1]
In the optical evaluation device 1 of example 1, the center-to-center intervals P of the plurality of shutters 101mIs 0.5mm, and the center-to-center spacing P of the plurality of periodic elements 103oIs 8mm, and the width W of each periodic element 103oIs 4 mm. Thus, Pm/WoIs 16, and the duty cycle (W) of the periodic element 103o/Po) Is 50%. Further, the width W of the shutter 101LBIs 0.2mm (duty cycle (W)LB/Pm) 40%) and the width W of the light illuminator 102LIIs 0.1mm (duty cycle (W)LI/Pm) 20%) of the total weight.
The optical evaluation apparatus 1 captures 16 images in positions where the plurality of periodic elements 103 have different phases. The driver 13 scans the light irradiation device 10 at a speed of 10 mm/sec, and the imager 12 performs imaging at an imaging interval of 50ms within an exposure period of 50 ms. Under these conditions, the amount of movement of the light irradiation device 10 during the exposure period of each image is 0.5 mm. In addition, when the time required for the driver 13 to accelerate and decelerate the light irradiation device 10 is excluded, the operation for capturing 16 images is completed within 0.8 second.
[ example 2]
In the optical evaluation device 1 of example 2, the center-to-center intervals P of the plurality of shutters 101mIs 1mm, and the center-to-center spacing P of the plurality of periodic elements 103oIs 12mm and each periodic element 103 has a width WoIs 6 mm. Thus, Pm/WoIs 12, and the duty cycle (W) of the periodic element 103o/Po) Is 50%. In addition, a shutterWidth W of 101LBIs 0.3mm (duty cycle (W)LB/Pm) 30%) and the width W of the light illuminator 102LIIs 0.2mm (duty cycle (W)LI/Pm) 20%) of the total weight.
The optical evaluation apparatus 1 captures 9 images in positions where the plurality of periodic elements 103 have different phases. The driver 13 scans the light irradiation device 10 at a speed of 22.2 mm/sec, and the imager 12 performs imaging at an imaging interval of 50ms within an exposure period of 60 ms. Under these conditions, the amount of movement of the light irradiation device 10 during the exposure period of each image was 1.33 mm. In addition, when the time required for the driver 13 to accelerate and decelerate the light irradiation device 10 is excluded, the operation for capturing 9 images is completed within 0.54 second.
According to the light irradiation device 10 of the present embodiment, the imager 12 can image the object 11 via the plurality of openings 107 of the light irradiation device 10. Therefore, the light irradiation device 10 and the imager 12 may be coaxially arranged, in other words, the light irradiation device 10 may be arranged between the object 11 and the imager 12. Therefore, the light irradiation device 10 may be arranged near the object 11. Therefore, even when the light irradiation device 10 of a small size is used, regular reflected light to the imager 12 can be obtained from a wide range of the surface of the object 11. Therefore, the optical evaluation apparatus 1 using the light irradiation apparatus 10 of the present embodiment can optically evaluate a wide range of the surface of the object 11 at once. Particularly when the surface of the object is a curved surface and the non-transmissive light irradiation device is disposed away from the object, a huge light irradiation device is required to obtain regular reflected light to the imager from a wide range of the object. Therefore, the light irradiation device 10 according to the present embodiment is particularly effective when the surface of the object is a curved surface. Further, the light irradiation device 10 of the present embodiment may be configured by making the center-to-center intervals P of the plurality of periodic elements 103oIs the center-to-center spacing P of the shutter 101mMore than twice to reduce intensity non-uniformities on the image that adversely affect the evaluation of the surface of the object 11.
In addition, the optical evaluation apparatus 1 using the light irradiation apparatus 10 of the present embodiment can be used for optical evaluation (optical inspection) performed as one step of an article manufacturing method (processing method). For example, the surface of a workpiece to be processed (an object to be processed) is optically evaluated by using the optical evaluation apparatus 1 of the present embodiment. If the evaluation result is better than the threshold value, the workpiece is transferred to a subsequent step (means for performing the subsequent step). If the result is worse than the threshold, the job is transferred to a reprocessing step (means for performing the reprocessing step). That is, the optical evaluation apparatus 1 of the present embodiment can be applied to an article manufacturing method that performs different processes (transfer to a subsequent step apparatus and transfer to a reprocessing apparatus) according to the optical evaluation result. In addition, when the optical evaluation apparatus 1 of the present embodiment is used, the optical evaluation step (optical evaluation apparatus) can be incorporated without requiring any large space inside the manufacturing apparatus (processing apparatus).
While the present invention has been described with respect to the exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
