WO2022271007A1

WO2022271007A1 - System and method of inspecting translucent object

Info

Publication number: WO2022271007A1
Application number: PCT/MY2022/050053
Authority: WO
Inventors: Syed Muhammad Nazir SYED KHOLED; Muhammad Saiful ZAKARIAH; Muzzammil AMRAN; Cowei OOI; Kong Chin Chee
Original assignee: Tt Vision Technologies Sdn. Bhd.
Priority date: 2021-06-22
Filing date: 2022-06-20
Publication date: 2022-12-29
Also published as: CN117546008A

Abstract

The present invention relates to a system (101) of inspecting translucent object (107), comprising of at least one image capturing device, at least one lens (105); whereby said system (101) further comprises of at least one structured light (113) which is beneficial in inspecting at least one void or bubble inside said translucent object (107) accurately. The present invention also relates to the process of performing said inspection of translucent object (107) using said system (101).

Description

SYSTEM AND METHOD OF INSPECTING TRANSLUCENT OBJECT

1. TECHNICAL FIELD OF THE INVENTION

The present invention relates to a system of inspecting translucent object, comprising of at least one image capturing device, at least one lens; whereby said system further comprises of at least one structured light which is beneficial in inspecting at least one void or bubble inside said translucent object accurately. The present invention also relates to the process of performing said inspection of translucent object using said system.

2. BACKGROUND OF THE INVENTION

Translucent objects are objects made of translucent material, whereby only a portion of light can pass through said material. This is different from transparent objects which allows all light to pass through while opaque objects do not allow light to pass through. One advantage of using translucent material on objects is that when light hits a translucent material such as a stained glass, there is a glowing effect. Therefore, translucent material is most effectively used in products like LEDs, and others.

In the process of manufacturing translucent objects, generally hot liquid resin is transferred to a mold before it gets hardened. During this process, there are chances that bubbles, or voids may appear inside the translucent material, due to some error in the manufacturing process. These bubbles or voids can harm the efficiency of the product. For example, if the translucent object is an LED, then the light emitted by the semiconductor die of the LED will not be homogeneously emitted out to the surrounding. This is because typically, when light rays meet the bubbles or voids, they will be further reflected or absorbed, therefore causing a dark spot emitted from that spot of the LED. In the past, a camera is used to take image of the translucent object, with the assistance of a general lighting system to assist in illuminating the said translucent object. However, by using general lighting system, the defect is not clearly shown in the image captured by the camera. Thus, many steps of image processing need to be performed in order to determine the existence of defect inside the translucent material of said translucent object. Furthermore, it happens more often than not, that false detection of defect, or missing of detection of defect happens due to the inaccuracy of the image taken by the camera.

FIG 1A shows a top view of an example of a translucent object (107), whereby said example is an LED, comprising of translucent material (117) inside a cavity formed by at least one housing (121), said LED further comprises of a semiconductor die (115) inside said translucent material (117). The housing (121) comprises of at least one inner surface, which acts as a side wall (129) in touch with said translucent material (117). As shown in FIG IB which is a cross sectional view of an example of a translucent object (107) of an LED, the semiconductor die (115) is placed on a leadframe (123) and being electrically connected to said leadframe (123) through at least one wire bond (125). FIG 2 further shows a cross sectional view of an example of a translucent object (107) such as an LED, with a defect such as bubble or void. FIG.3 shows an image taken by the image capturing device, using a conventional light source, whereby said light source is a light emitting device such as an LED light which emits beam of light straight to the object without any form of alteration or masking. As can be seen in FIG 3, the defect (127) is not shown clearly amongst the translucent material (117) in the image because the pixels surrounding the defect (127) is having similar intensity value as the pixels of the defect (127), causing more time and image processing is needed to determine the location of the defect (127) in said image.

Hence, it would be advantageous to alleviate the shortcomings by having a system and method of inspecting translucent object, comprising of at least an image capturing device with lens; said system further comprising of at least one light emitting system emitting at least one structured light so that the image capturing device is able to capture high accuracy images in detecting defects inside the translucent material (117) of said translucent object. 3. SUMMARY OF THE INVENTION

Accordingly, it is the primary aim of the present invention to provide a system and method of inspecting translucent object which is able for the image capturing device to obtain at least one image which is having less noise than when using typical lighting, therefore requiring less time and effort to perform image processing. It is yet another objective of the present invention to provide a system and method of inspecting translucent object, which increases the accuracy of defect detection inside the translucent material of the translucent object.

Additional objects of the invention will become apparent with an understanding of the following detailed description of the invention or upon employment of the invention in actual practice.

According to the preferred embodiment of the present invention the following is provided:

A system (101) of inspecting translucent object (107), comprising of: at least one image capturing device (103) with at least one lens (105), facing the direction towards said translucent object (107); characterized in that said system (101) further comprises of at least one light emitting system (111), capable of emitting at least one structured light (113) towards said translucent object (107); said translucent object (107) comprises of translucent material (117) inside at least one cavity formed by at least one housing (121). In another embodiment of the invention there is provided:

A method of inspecting translucent object (701), comprising the steps of:

(i) at least one image capturing device (103), through at least one lens (105), capturing at least one image (801) of at least one translucent object (107), while at least one light emitting system (111) emitting at least one structured light (113) towards the translucent material (117) portion of said translucent object (107); wherein said translucent object (107) comprises of translucent material (117) inside at least one cavity formed by at least one housing;

(h) image processing means performing at least one threshold algorithm on said image (801), to identify defect in said image (801).

4. BRIEF DESCRIPTION OF THE DRAWINGS

Other aspect of the present invention and their advantages will be discerned after studying the Detailed Description in conjunction with the accompanying drawings in which:

FIG. 1A and IB are the top view and cross sectional view of an example of a translucent object. FIG. 2 is a cross sectional view of an example of a translucent object, with a defect.

FIG. 3 is an image taken by the image capturing device, using conventional light source.

FIG. 4 is a cross sectional view of a system of inspecting translucent object, of the present invention, for defects.

FIG. 5 is a cross sectional view of a system of inspecting translucent object, of the present invention, showing the light paths of structured light from light emitting system to translucent object, before being reflected to the image capturing device.

FIG. 6A to FIG. 6H are top views of the examples of the structured light that can be used for the inspection of translucent object.

FIG 7 is a flowchart showing the method of inspecting translucent object, of the present invention.

FIG. 8 shows the flow of images used in the method of inspecting translucent object, of the present invention.

5. DETAILED DESCRIPTION OF THE DRAWINGS

In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be understood by the person having ordinary skill in the art that the invention may be practised without these specific details. In other instances, well known methods, procedures and/ or components have not been described in detail so as not to obscure the invention.

The invention will be more clearly understood from the following description of the embodiments thereof, given by way of example only with reference to the accompanying drawings, which are not drawn to scale.

FIG 4 is cross sectional view of a system (101) of inspecting translucent object (107) of the present invention, in the objective of detecting defects inside the translucent material (117). As shown in FIG 4, the system (101) of inspecting translucent object (107) comprises of at least one image capturing device (103) with at least one lens (105) and at least one light emitting system (111); all used to inspect at least one translucent object

(107).

In certain scenario, the translucent object (107) may be hold into a predetermined location by at least one object holder (not shown) to ensure the relative position between said translucent object (107) and said image capturing device (103) and light emitting system (111) is hold or kept in position as desired. The translucent object (107) may be on a leadframe, a tape and reel pocket, or even with no holder when vision inspection is done on said translucent object (107).

The image capturing device (103) with at least one lens (105) is positioned such that said lens (105) is facing the direction towards said translucent object (107). The light emitting system (111) is positioned such that said light emitting system (111) is capable of emitting at least one structured light (113) towards said translucent object (107). The translucent object (107) which is targeted to be inspected comprises of translucent material (117) inside at least one cavity formed by at least one housing (121). In an example of a translucent object (107) of an LED, as shown in FIG 1 to FIG 3, the translucent object (107) further comprises of at least one semiconductor die (115) encapsulated by said translucent material (117), wherein said semiconductor die (115) is placed on at least one leadframe (123) and electrically connected to said leadframe (123) through at least one wire bond (125). Even though the image capturing device (103) is positioned to face the translucent object (107), it is important to note that the lens (105) of the image capturing device (103) should be facing the translucent material (117) being exposed from the translucent object (107). In other words, the translucent object (107) comprises of surfaces comprising of the housing (121) and surfaces which exposes the translucent material (117). The lens (105) of the image capturing device (103) should be positioned in the direction of the surface which exposes the translucent material (117), so that the image capturing device (103) is able to capture images (801) of the translucent material (117) of the translucent object (107). If the surface of the translucent object (107) exposing the translucent material (117) is substantially flat, it is recommended for the image capturing device (103) to be positioned such that the lens (105) is at a direct angle from the surface of said translucent material (117), in order to capture a clear image of said translucent material (117). Another rule that generally needs to be observed, is that said image capturing device (103) with lens (105) is positioned such that said image capturing device (103) is capable of taking at least one image (801) of said translucent material (117) of said translucent object (107) without being obstructed by said housing (121). This is so that coverage of the image (801) captured by said image capturing device (103) should be to the maximum coverage, if not the whole surface of translucent material (117) being exposed from the translucent object (107). The purpose of having such large coverage is to ensure defects inside said translucent material (117) can be detected no matter the location of the defect inside said translucent material (117). As shown in FIG 4, the light emitting system (111) is positioned such that said light emitting system (111) is capable of emitting at least one structured light (113) towards the translucent material (117) of said translucent object (107). The light emitting system (111) is positioned to be at a predetermined angle (a) away from said image capturing device (103) with reference to said translucent object (107) such that said light emitting system (111) is capable of projecting said structured light (113) to said translucent material (117) of said translucent object (107) without being obstructed by said housing (121).

Structured light (113) can be made to emit from said light emitting system (111), by having a light emitting device to emit light through at least one light masking device such as a masking plate or projection pattern plate, whereby the light passing through said light filtering system will be in a predetermined shape and size. The said masking plate can be a glass with lithography to allow light to only pass through a portion of the plate where no lithography is done, whereby said portion can be of a certain pattern as shown in FIG 6A to FIG 6H. The structured light (113) can even be emitted by the light source itself. It is important to note that any mechanism of light emitting is possible, as long as light of a particular pattern or structure is hitting said translucent material (117) of said translucent object (107). FIG 6A to FIG 6H show all the possible shapes and sizes of structured lights that may be emitted from said light emitting system (111).

Generally, the size of the structured light (113) being projected to the translucent material (117) of the translucent object (107) is such that said size is able to cover as much of the surface of said translucent material (117) which exposes the translucent material (117). In an example of a case of the translucent object (107) being an LED, as shown in

FIG 1, the translucent material (117) being exposed is in the shape of a circle. Therefore, the best shape of structured light (113) to be used is to project a circle structured light (113) whereby the diameter of the circle is as near as possible to the diameter of the circle of the exposed translucent material (117). By having this shape and size of structured light (113), said structured light (113) will also be as far as possible from the semiconductor die (115), for the example of the translucent object (107) being an LED. The structured light (113) needs to be as far as possible from the semiconductor die (115), so as to avoid having light being directly hitting said semiconductor die (115) and causing direct light reflection. This is because when light shines on a shiny or reflective surface such as a semiconductor die (115), more light will be reflected, therefore causing over expose or excessive noise to the image (801) taken by the image capturing device. In contrast, light shown on the leadframe or translucent material is diffused and does not cause over-expose or excessive noise to the image (801) taken by the image capturing device. Therefore, the structured light (113) projected on said translucent object (107) has a perimeter less than and as close as possible to the perimeter of the surface of said translucent object (107) facing said light emitting system (111).

However, is it important to note that the shape of the structured light (113) being projected to the surface of the exposed translucent material (117) not necessarily be the same shape as the shape of the exposed translucent material (117). For example, of the translucent object (107) being an LED, even though the exposed surface of translucent material (117) is circle, the projected structured light (113) can be of the shape of a square, rectangular, pentagon or any other possible shapes, as long as the size of the projected structured light (113) should be smaller but as close as possible to the size of the exposed translucent material (117) of the translucent object (107).

The structured light (113) emitted from said light emitting system (111) preferably should have a light bandwidth of from Ultraviolet (UV) up to near Infra-Red (IR). In furtherance to this, any light bandwidth can be used by said light emitting system (111), as long as said light can be picked up by said image capturing device (103).

As shown in FIG 5, when the structured light (113) being emitted from the light emitting system (111) is projected towards the exposed translucent material (117) of the translucent object (107), the light path will pass through the surface of the translucent material (117), will travel through the translucent material (117), and will be reflected when said light reaches an opaque material such as leadframe (123) inside translucent object (107) such as an LED. The light path will be reflected or scattered to multiple directions, which will further be reflected upon reaching another opaque surface such as the side wall (129) of the housing (121), which can act as a reflector due to the opaque characteristic. Eventually, the light will be reflected to the lens (105) of the image capturing device (103).

In the event that there is a defect inside the translucent material (117) such as a bubble / void, the light path will also be reflected when reaching the bubble / void. The light path being reflected to the image capturing device (103) when the translucent material (117) does not have bubble or void (127), is different from the light path being reflected back when the translucent material (117) does have bubble or void (127). Hence, the image (801) being captured by the image capturing device (103) would indicate existence of defect such as bubble / void (127). As shown in FIG 7, it shows a flowchart of the method (701) of inspecting translucent object (107), of the present invention, comprising the following steps. In step (i), at least one image capturing device (103), through at least one lens (105), captures at least one image (801) of at least one translucent object (107), while at least one light emitting system (111) emits at least one structured light (113) towards the translucent material (117) portion of said translucent object (107). The translucent object (107) comprises of translucent material (117) inside at least one cavity formed by at least one housing (121). In an example of the translucent object (107) being an LED, said translucent object (107) further comprises of at least one semiconductor die (115) encapsulated by said translucent material (117), wherein said semiconductor die (115) is placed on at least one leadframe (123) and electrically connected to said lead frame (123) through at least one wire bond (125). The defect inside said translucent material (117) is void, bubble or any other possible defects in a translucent object (107).

The structured light (113) projected on said translucent object (107) has size less than and as close as possible to the size of the surface of said translucent object (107) facing said light emitting system (111). In step (ii), the image processing means performing at least one threshold algorithm on said image (801), to identify defect in said image (801). Any suitable threshold algorithm such as Global Threshold can be used, as long as suitable to identify defect in said image (801).

Said step (ii) of the said method (701) of inspecting translucent object (107) may comprise of sub-steps in several possible flow. In the first possible flow, the threshold algorithm comprises of the following sub-steps. In the first flow's first sub-step, the user defines at least one first region (803) inside said image (801), wherein said first region (803) includes the area covering the translucent material (117), and said first region (803) includes an area wherein at least one defect (127) may exist inside said translucent material (117). In the first flow's second sub-step, the user sets a first threshold intensity value to be used on said first region (803), whereby at least one pixel in said first region (803) which has higher intensity value (807) than said second threshold intensity value is plotted by at least one processing means and implicated as defect (127) in said translucent material (117). In the second possible flow, the threshold algorithm comprises of the following sub-steps. In the second flow's first sub-step, user defines at least one second region (809) smaller than the area covered by pixels of the structured light and said second region (809) includes an area wherein at least one defect (127) may exist inside said second region (809), thereby reducing the search region. In the second flow's second sub-step, the user sets a second threshold intensity value to be used on said second region (809), whereby at least one pixel in said second region (809) which has higher intensity value (807) than said second threshold intensity value is plotted by at least one processing means and implicated as defect (127) in said translucent material (117).

In the third possible flow, the threshold algorithm comprises of the following sub- steps. In the third flow's first sub-step, the user defines at least one first region (803) inside said image (801), wherein said first region (803) includes the area covering the translucent material (117) and said first region (803) includes an area wherein at least one defect (127) may exist inside said translucent material (117). In the third flow's second sub-step, the user sets a first threshold intensity value to be used on said first region (803), whereby at least one pixel in said first region (803) is classified as either below (805) or above (807) said threshold intensity value, to filter out surround noise. In the third flow's third sub- step, the user defines at least one second region (809) inside said first region (803), wherein said second region (809) is smaller than the area covered by pixels of the structured light and said second region (809) includes an area wherein at least one defect (127) may exist inside said second region (809), thereby reducing the search region. In the third flow's fourth sub-step, the user sets a second threshold intensity value to be used on said second region (809), whereby at least one pixel in said second region (809) which has higher intensity value (807) than said second threshold intensity value is plotted by at least one processing means and implicated as defect (127) in said translucent material

(117). When determining the first region (803) and/ or second region (809), said region is chosen by the user based on the experience of the user or based on past data on the probability of position of said defect (127). As an option, the user is able to define at least one suitable minimum size of pixel areas of higher intensity value (807) than said second threshold intensity value which is defined as the defect (127). This option is useful for the user to eliminate smaller defects (127) which in certain cases will not affect the functionality of the translucent object (107) and should not be detected while performing the method of inspection translucent object (107).

FIG 8 shows the sample of images (801) after going through the steps in the method of inspecting translucent object (107) of the present invention. In using as example, the first threshold intensity value should be around 100-150 intensity value while the second threshold value should be around 200-255 intensity value. It is important to note that all suitable first threshold intensity value and second threshold intensity value can be used as well.

While the present invention has been shown and described herein in what are considered to be the preferred embodiments thereof, illustrating the results and advantages over the prior art obtained through the present invention, the invention is not limited to those specific embodiments. Thus, the forms of the invention shown and described herein are to be taken as illustrative only and other embodiments may be selected without departing from the scope of the present invention, as set forth in the claims appended hereto.

Claims

WHAT IS CLAIMED IS:

1. A system (101) of inspecting translucent object (107), comprising of: at least one image capturing device (103) with at least one lens (105), facing the direction towards said translucent object (107); characterized in that said system (101) further comprises of at least one light emitting system (111), capable of emitting at least one structured light (113) towards said translucent object (107); said translucent object (107) comprises of translucent material (117) inside at least one cavity formed by at least one housing (121).

2. The system (101) of inspecting translucent object (107) as claimed in Claim 1, wherein said system further comprises of at least one object holder, capable of holding said translucent object (107) to be inspected.

3. The system (101) of inspecting translucent object (107) as claimed in Claim 1, wherein the structured light (113) projected on said translucent object

(107) has size less than and as close as possible to the size of the surface of said translucent material (117) facing said light emitting system (111).

4. The system (101) of inspecting translucent object (107) as claimed in Claim 1, wherein said image capturing device (103) with lens (105) is positioned such that said image capturing device (103) is capable of taking at least one image (801) of said translucent material (117) of said translucent object (107) without being obstructed by said housing.

5. The system (101) of inspecting translucent object (107) as claimed in Claim 1 or 3, wherein said light emitting system (111) is positioned to be at a predetermined angle (a) away from said image capturing device (103) with reference to said translucent object (107) such that said light emitting system (111) is capable of projecting said structured light (113) to the translucent material (117) of said translucent object (107) without being obstructed by said housing (121).

6. The system (101) of inspecting translucent object (107) as claimed in Claim 1, wherein said structured light (113) has light bandwidth of from Ultraviolet (UV) up to near Infra-Red (IR).

7. The system (101) of inspecting translucent object (107) as claimed in Claim 1, wherein said translucent object (107) further comprises of at least one semiconductor die (115) encapsulated by said translucent material (117), wherein said semiconductor die (115) is placed on at least one leadframe (123) and electrically connected to said leadframe (123) through at least one wire bond (125).

8. A method of inspecting translucent object (701), comprising the steps of:

(ii) image processing means performing at least one threshold algorithm on said image (801), to identify defect in said image (801).

9. The method of inspecting translucent object (701) as claimed in Claim 8, wherein said threshold algorithm comprises of the following sub-steps: (a) user defining at least one first region (803) inside said image (801), wherein said first region (803) includes the area covering the translucent material, and said first region (803) includes an area wherein at least one defect may exist inside said translucent material (117); (b) user setting a first threshold intensity value to be used on said first region (803), whereby at least one pixel in said first region (803) which has higher intensity value (807) than said second threshold intensity value is plotted by at least one processing means and implicated as defect (127) in said translucent material (117).

10. The method of inspecting translucent object (701) as claimed in Claim 8, wherein said threshold algorithm comprises of the following sub-steps:

(a) user defining at least one second region (809) smaller than the area covered by pixels of the structured light, and said second region (809) includes an area wherein at least one defect (127) may exist inside said second region (809);

(b) user setting a second threshold intensity value to be used on said second region (809), whereby at least one pixel in said second region (809) which has higher intensity value (807) than said second threshold intensity value is plotted by at least one processing means and implicated as defect (127) in said translucent material (117).

11. The method of inspecting translucent object (701) as claimed in Claim 8, wherein said threshold algorithm comprises of the following sub-steps: (a) user defining at least one first region (803) inside said image (801), wherein said first region (803) includes the area covering the translucent material (117), and said first region (803) includes an area wherein at least one defect (127) may exist inside said translucent material (117); (b) user setting a first threshold intensity value to be used on said first region (803), whereby at least one pixel in said first region (803) is classified as either below (805) or above (807) said threshold intensity value, to filter out surround noise;

(c) user defining at least one second region (809) inside said first region (803), wherein said second region (809) is smaller than the area covered by pixels of the structured light, and said second region (809) includes an area wherein at least one defect (127) may exist inside said second region (809);

(d) user setting a second threshold intensity value to be used on said second region (809), whereby at least one pixel in said second region (809) which has higher intensity value (807) than said second threshold intensity value is plotted by at least one processing means and implicated as defect (127) in said translucent material (117). 12. The method of inspecting translucent object (701) as claimed in Claim 9, 10 or 11, wherein user has the capability of defining at least one suitable minimum size of defect.

13. The method of inspecting translucent object (701) as claimed in Claim 8, wherein the structured light (113) projected on said translucent object (107) has size less than and as close as possible to the size of the surface of said translucent object (107) facing said light emitting system (111).

14. The method of inspecting translucent object (701) as claimed in Claim 8, therein said translucent object further comprises of at least one semiconductor die (115) encapsulated by said translucent material (117), wherein said semiconductor die (115) is placed on at least one leadframe (123) and electrically connected to said leadframe (123) through at least one wire bond (125).

15. The method of inspecting translucent object (701) as claimed in Claim 8, wherein said defect is void, bubble or any other possible defects in a translucent object (107).