Defective Pixel Detection Device and Defective Pixel Detection Method

Abstract

To provide a defective pixel detection device and a defective pixel detection method that can accurately detect a defective pixel with a relatively simple method.SOLUTION: A defective pixel detection method includes: preparing a first output image of an image forming element obtained by inputting a predetermined first pattern signal to the image forming element, and a second output image of the image forming element obtained by inputting a second pattern signal formed of a pixel reverse pattern of the first pattern signal to the image forming element; and displaying the first output image and second output image on an image display unit, while switching the images at a high speed to the extent that the images cannot be individually recognized.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a defective pixel detection device and a defective pixel detection method for detecting defective pixels of an image forming element.

Background Art

[0002] A digital micromirror device (hereinafter referred to as "DMD") arranges more than two million micromirrors with a side length of a dozen or so μm in an array, and drives an electrode provided below to individually switch the inclination of each micromirror to either an ON state (+ about 12 degrees) or an OFF state (- about 12 degrees), and reflects the light from the internal light source with the micromirrors in the ON state to form a desired output image. Because of its high resolution, it is possible to form a fine pattern.

[0003] Therefore, in recent years, DMD has been widely used as an image forming element. As an example, an exposure apparatus using DMD as an exposure engine has already been put into practical use in the field of photolithography. This type of exposure apparatus can directly expose a circuit pattern such as a semiconductor element, a liquid crystal display panel, or a plasma display panel onto a photoresist without using a photomask, and is therefore called a maskless exposure apparatus. In addition, in the manufacturing process of a photomask, pattern baking is also performed using an exposure apparatus.

[0004] On the other hand, since the micromirrors of DMD are extremely small, there is a risk of malfunction due to electrical or mechanical defects. This malfunction becomes defective pixels in the image forming element, and thus is a problem that cannot be ignored in photolithography that requires high-precision pattern formation in micron units. Therefore, various defective pixel detection methods have been proposed conventionally.

[0005] The defective pixel detection method described in Patent Document 1 inputs a first pattern signal in which ON and OFF are alternately repeated into a DMD, sets each micromirror to an output state in which the ON state and the OFF state are alternately repeated, detects the image output from the DMD with a CCD, and then inputs a second pattern signal in which the pixels of the first pattern are inverted into the DMD, and after detecting the image output from the DMD with the CCD, by blurring the obtained images respectively, when the obtained image contains defective pixels, the area becomes an image that protrudes from a uniform gray background, and defective pixels are detected by this method.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] However, as described above, since the micromirror is extremely small with a side length of a dozen or so μm, the luminance difference in the image between the case where it becomes a defective pixel and the case where it does not is extremely small. Therefore, the phenomenon that defective pixels protrude from a uniform gray background is difficult to obtain, and thus, there is a problem that the defective pixel detection method described in Patent Document 1 cannot accurately detect defective pixels.

[0008] Therefore, in view of such circumstances, an object of the present invention is to provide a defective pixel detection device and a defective pixel detection method capable of accurately detecting defective pixels by a relatively simple method.

Means for Solving the Problems

[0009] The defective pixel detection device according to the present invention is A first output image of the image forming element obtained by inputting a predetermined first pattern signal to the image forming element and imaging the output with an imaging device, and a second output image of the image forming element obtained by inputting a second pattern signal composed of a pixel inversion pattern of the first pattern signal to the image forming element and imaging the output with the imaging device, are stored in a storage unit. An image display unit used for an inspector to visually inspect, which is capable of displaying the first output image and the second output image. In the image display unit, the first output image and the second output image The switching speed is 100 milliseconds or less are provided with a display control unit that switches and displays the images at a high speed such that each image cannot be recognized individually. This is the device.

[0011] Also, a defective pixel detection method according to the present invention prepares a first output image of the image forming element obtained by inputting a predetermined first pattern signal to the image forming element and imaging the output with an imaging device, and a second output image of the image forming element obtained by inputting a second pattern signal composed of a pixel inversion pattern of the first pattern signal to the image forming element and imaging the output with the imaging device. In the image display unit used for an inspector to visually inspect, the first output image and the second output image The switching speed is 100 milliseconds or less are switched and displayed at a high speed such that each image cannot be recognized individually. This is the method.

[0013] According to these inventions, when the output image includes defective pixels, by making it a high-speed switching display image, only the portions of the defective pixels stand out, flicker, shake, or are displayed pulsatingly. Since the display form is significantly different from other regions, it is difficult to overlook. Therefore, the inspector can clearly grasp that the output image includes defective pixels, that is, that there are defective pixels in the image forming element.

[0014] Here, as an aspect of the defective pixel detection device according to the present invention, The first pattern signal is a signal in which ON and OFF are alternately repeated, or a signal in which ON and OFF are repeated in units of a predetermined pixel block. returned The second pattern signal is a signal in which the ON and OFF of the first pattern signal are inverted. The above configuration can be adopted.

[0015] In addition, as another aspect of the defective pixel detection device according to the present invention, The display control unit has a function of enlarging and displaying a partial area of the image displayed on the image display unit, a function of stopping the switching display of the enlarged image and displaying one of the images, and / or a function of slowing down the switching speed of the switching display to an extent that each image can be recognized individually. The above configuration can be adopted.

[0017] In still another aspect of the defective pixel detection device according to the present invention, The image forming element is a digital micromirror device (DMD) that forms an image by reflecting light emitted from a light source. The above configuration can be adopted. Effect of the Invention

[0018] As described above, the defective pixel detection device and defective pixel detection method of the present invention make it possible to accurately detect defective pixels using a relatively simple method of quickly switching between displays of a plurality of images, including the output image of the image forming element to be inspected. [Brief description of the drawings]

[0019]

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DETAILED DESCRIPTION OF THE INVENTION

[0020] Hereinafter, an embodiment of a defective pixel detection device and a defective pixel detection method according to the present invention will be described with reference to the drawings.

[0021] As shown in FIGS. 1 and 2, the defective pixel detection device 1 according to the present embodiment includes an imaging device 10 and a display device 20, and is mainly applied to a digital exposure device 3. Briefly explaining the digital exposure device 3, the digital exposure device 3 includes a light source 30, a DMD 31 that reflects the light irradiated from the light source 30 to form an image, and an xy table 32 on which the image (reflected light) formed by the DMD 31 is projected.

[0022] The imaging device 10 is placed on the xy table 32 and captures the output image output from the DMD 31, and includes a control unit 11 configured with a CPU, an imaging unit 12 composed of, for example, a CCD image sensor, a storage unit 13 that stores various data such as the captured output image and a reference image described later, and an I / F (interface) unit 14 such as a USB.

[0023] The display device 20 is configured using a computer such as a personal computer, and includes a control unit 21 including a display control unit 22, a storage unit 23, I / F units 24 and 25, an image display unit 26 such as a monitor connected via the I / F unit 25, and a PD (pointing device) 27 such as a mouse.

[0024] The imaging device 10 and the display device 20 are separably connected via a cable 15 such as a USB cable connected to the I / F units 14 and 24. However, the imaging device 10 and the display device 20 may be connected by wireless communication such as wireless LAN, Bluetooth (registered trademark), IrDA, Zigbee (registered trademark), or specific low-power radio instead of wired communication, or they may be integrally configured.

[0025] Next, a defective pixel detection method using the defective pixel detection device 1 will be described. First, a first pattern signal is input to the DMD 31 using the interface of the digital image device 3 (step 1). The first pattern signal is a signal in which ON and OFF are alternately repeated in the array direction of the micromirrors 33, as shown in, for example, FIG. 4(a). In the drawings, the micromirror 33a that has transitioned to the ON state by the ON signal is represented in white, and the micromirror 33b that has transitioned to the OFF state by the OFF signal is represented by hatching.

[0026] In this state, DMD31 is caused to output, and the image formed by DMD31 is projected onto the xy table 32 of the digital exposure apparatus 3 (step 2). This is imaged by the imaging device 10 placed on the xy table 32 (step 3). Then, the captured output image of DMD31 (first output image, Fig. 5(a)) is stored in the storage unit 13 of the imaging device 10 (step 4).

[0027] Similarly, a second pattern signal is input to DMD31 (step 5). As shown in Fig. 4(b), the second pattern signal is a signal in which the ON and OFF of the first pattern signal are inverted. In this state, DMD31 is caused to output, and the image formed by DMD31 is projected onto the xy table 32 of the digital exposure apparatus 3 (step 6). This is imaged by the imaging device 10 placed on the xy table 32 (step 7). Then, the captured output image of DMD31 (second output image, Fig. 5(b)) is stored in the storage unit 13 of the imaging device 10 (step 8).

[0028] Next, the first output image and the second output image stored in the storage unit 13 are transferred from the imaging device 10 to the display device 20 and stored in the storage unit 23 of the display device 20 (steps 9 and 10). After finishing the preparatory work so far, the inspection work will start from now on. When a high-speed switching display instruction is given to the display device 20 using PD27 (when step 11 is YES), the display control unit 22 performs switching display between the first output image and the second output image on the image display unit 26 (steps 12 and 13). The switching speed of the high-speed switching display is set to 100 milliseconds. That is, the display of the first output image for 100 milliseconds and the display of the second output image for 100 milliseconds are alternately repeated.

[0029] Then, since the first output image and the second output image have an inverted relationship between light (white, digital value 1) and dark (black, digital value 0), when the first output image and the second output image are switched and displayed at high speed, due to the afterimage effect of human vision, as shown in Fig. 6(a), to the inspector, the high-speed switched display image A is visually perceived as an image that is blurred and monochromatized to gray as a whole or an image in a state close to this. Similarly, as shown in Fig. 6(b), the same applies to the enlarged image B. Therefore, when there are no defective pixels in both images, it becomes an image with no particular change.

[0030] However, as shown in Fig. 7(a), when there is a defective pixel 33c in DMD31 that does not transition to either the ON state or the OFF state, its output image becomes an image as shown in Fig. 8(a). Also, as shown in Fig. 7(b), when there is a defective pixel 33d in DMD31 that remains in the OFF state transition, its output image becomes an image as shown in Fig. 8(b). Further, when there is a defective pixel 33e in DMD31 that remains in the ON state transition, its output image becomes an image as shown in Fig. 8(c). In all cases, it becomes an image in which the regularity of white (1) and black (0) of the checker pattern (checkerboard pattern) is partially disrupted.

[0031] In such a case, by performing high-speed switching display (see Figs. 9 and 10), as shown in Fig. 11(a), to the inspector, only the part of the defective pixel appears to float, flicker, sway, or pulsate visually. Therefore, in order to confirm whether it is really a defective pixel, the inspector uses PD27 to instruct an enlarged display of the corresponding location as shown in Fig. 11(b), and also inputs an instruction to stop the switching display of the enlarged image as needed or an instruction to lower the switching speed of the switching display to a level where each image can be recognized individually, and checks for the presence or absence of defective pixels.

[0032] And if there is still a defective pixel, appropriate measures will be taken for the DMD31. Alternatively, if it is not a defective pixel and there is no defective pixel in the DMD31, the DMD31 is considered appropriate and used for the digital exposure device. As shown in Fig. 11(b), the image display unit 26 displays the center coordinates of the enlarged selection area (which can also be the (rectangular) coordinates of the display area) and the magnification ratio with respect to the actual size of the DMD, so that the position information of the defective pixel in the DMD can be obtained.

[0033] As described above, according to the defective pixel detection device and the defective pixel detection method according to the present embodiment, when the output image contains a defective pixel, by using a high-speed switching display image, only the part of the defective pixel appears, flickers, shakes, or is displayed pulsatingly. Since the display form is significantly different from other areas, it is difficult to overlook. Therefore, the inspector can clearly grasp that the output image contains a defective pixel, that is, there is a defective pixel in the DMD31. Thereby, defective pixels can be accurately detected by a relatively simple method of high-speed switching display of a plurality of images including the output image of the DMD31 to be inspected.

[0034] Moreover, according to the defective pixel detection device and the defective pixel detection method according to the present embodiment, by looking at the overall image of the high-speed switching display image, or by dividing the overall image into several parts at a magnification that is not too large and looking at them, if there is a suspicious area, the range is narrowed down for detailed confirmation. Therefore, compared with the method of checking each pixel one by one, defective pixels can be detected quickly and efficiently. Thereby, a highly accurate inspection can be performed without spending time.

[0035] Note that the first pattern signal and the second pattern signal are not limited to the signals in which ON and OFF are alternately repeated as described above, and various patterns having an inversion relationship with each other can be selected. As an example, the pattern signal shown in FIG. 12 is a signal in which ON and OFF are alternately repeated for every 2×2 = 4 pixel blocks. As a result, as shown in FIG. 13, an output image in which white (1) and black (0) are repeated in units of 2×2 = 4 pixel blocks is obtained. Further, as another example, the pattern signal shown in FIG. 14 is a signal in which ON and OFF are alternately repeated for every 3×3 = 9 pixel blocks. As a result, as shown in FIG. 15, an output image in which white (1) and black (0) are repeated in units of 3×3 = 9 pixel blocks is obtained. Thus, by changing the number of unit pixels of the pattern, defective pixels of various sizes can be detected.

[0036] Also, the switching display is not limited to switching between two images, i.e., the first output image and the second output image. For example, a dummy image with all white (1), a dummy image with all black (0), or a dummy image with all gray can be sandwiched between the first output image and the second output image, and three or more images, including these dummy images, can be switched and displayed.

[0037] <Another Defective Pixel Detection Method> The defective pixel detection method according to the above embodiment is to rapidly switch and display the first output image and the second output image based on the first pattern signal and the second pattern signal having an inversion relationship with each other. Here, instead of rapidly switching and displaying the first output image and the second output image, the first output image and the first reference image corresponding to the first pattern signal are rapidly switched and displayed, and the second output image and the second reference image corresponding to the second pattern signal are rapidly switched and displayed.

[0038] As shown in FIG. 16, first, a first pattern signal is input to the DMD 31 using the interface of the digital image device 3 (step 1). The first pattern signal is a signal in which ON and OFF are alternately repeated in the array direction of the micromirrors 33, for example, as shown in FIG. 4(a). In this state, the DMD 31 is caused to output, and the image formed by the DMD 31 is projected onto the xy table 32 of the digital exposure device 3 (step 2). This is imaged by the imaging device 10 placed on the xy table 32 (step 3). Then, the captured output image (first output image, FIG. 5(a)) of the DMD 31 is stored in the storage unit 13 of the imaging device 10 (step 4).

[0039] Similarly, a second pattern signal is input to the DMD 31 (step 5). The second pattern signal is a signal in which the ON and OFF of the first pattern signal are inverted, as shown in FIG. 4(b). In this state, the DMD 31 is caused to output, and the image formed by the DMD 31 is projected onto the xy table 32 of the digital exposure device 3 (step 6). This is imaged by the imaging device 10 placed on the xy table 32 (step 7). Then, the captured output image (second output image, FIG. 5(b)) of the DMD 31 is stored in the storage unit 13 of the imaging device 10 (step 8).

[0040] Next, the first output image and the second output image stored in the storage unit 13 are transferred from the imaging device 10 to the display device 20 and stored in the storage unit 23 of the display device 20 (steps 9 and 10). After finishing the preparation work so far, the inspection work will start from now on. When a high-speed switching display instruction is given to the display device 20 using the PD 27 (when step 11 is YES), the display control unit 22 performs switching display between the first output image and the first reference image in the image display unit 26 (steps 12 and 13). The first reference image and the second reference image described later are images created by image processing or output images of the same type of DMD that have been confirmed to be normal, and these are stored in advance in the storage unit 23 of the display device 20.

[0041] Then, since the bright (white, digital value 1) and dark (black, digital value 0) of the first output image and the first reference image are in the same phase relationship, when the first output image does not contain defective pixels, the high-speed switching display image remains a checkerboard pattern (checkerboard pattern) and does not change. However, when there are defective pixels in DMD31 that do not transition to either the ON state or the OFF state of the micromirror (see Fig. 7(a)), or when there are defective pixels in DMD31 that remain in the OFF state transition (see Fig. 7(b)), the output image thereof becomes an image in which the regularity of white (1) and black (0) of the checkerboard pattern (checkerboard pattern) is partially disrupted, as shown in Figs. 8(a) and 8(b).

[0042] In such a case, by performing high-speed switching display (see Fig. 17), to the inspector, only the part of the defective pixel appears to float, flicker, shake, or pulsate visually. Therefore, in order to confirm whether it is really a defective pixel, the inspector uses PD27 to instruct the enlarged display of the corresponding location, and also inputs an instruction to stop the switching display of the enlarged image as needed or an instruction to lower the switching speed of the switching display to such an extent that each image can be recognized individually, and checks the presence or absence of defective pixels.

[0043] However, when it is a defective pixel that remains in the ON state transition of the micromirror (see Fig. 7(c)), it does not appear as a defect in the first output image. Therefore, when the confirmation operation of the first output image is completed (step 14 is YES), next, the display control unit 22 performs switching display of the second output image and the second reference image on the image display unit 26 (steps 15, 16).

[0044] Then, when the second output image does not contain defective pixels, the high-speed switching display image remains a checkered pattern (checkerboard pattern) and does not change. However, when defective pixels that remain in the ON state of the micromirror exist in DMD31 (see Fig. 7(c)), the output image becomes an image in which the regularity of white (1) and black (0) in the checkered pattern (checkerboard pattern) is partially disrupted as shown in Fig. 8(c). In such a case, by performing high-speed switching display (see Fig. 18), only the portion of the defective pixel appears to float, flicker, sway, or pulsate visually to the inspector. Therefore, in order to confirm whether it is truly a defective pixel, the inspector uses PD27 to instruct an enlarged display of the corresponding location, and also inputs an instruction to stop the switching display of the enlarged image if necessary, or an instruction to lower the switching speed of the switching display to such an extent that each image can be recognized individually, and checks for the presence or absence of defective pixels.

[0045] And if there are still defective pixels, appropriate measures will be taken for that DMD31. Or, if it is not a defective pixel and there are no defective pixels in that DMD31, then that DMD31 is considered proper and is used for the digital exposure device.

[0046] Also, by such a defective pixel detection method, when the output image contains defective pixels, by making it a high-speed switching display image, only the portion of the defective pixel appears to float, flicker, sway, or pulsate. Since its display form is significantly different from other areas, it is less likely to be overlooked. Therefore, the inspector can clearly grasp that the output image contains defective pixels, that is, that there are defective pixels in DMD31. As a result, defective pixels can be accurately detected with a relatively simple method of high-speed switching display of a plurality of images including the output image of DMD31 to be inspected.

[0047] Note that the defective pixel detection device and the defective pixel detection method according to the present invention are not limited to the above-described embodiment, and various modifications are possible without departing from the gist of the present invention.

[0048] For example, in the above embodiment, the first output image and the second output image were obtained by directly imaging the output of the exposure engine of the digital exposure device 3 with the imaging device 10. However, the first output image and the second output image are not limited thereto, and based on the first pattern signal and the second pattern signal respectively by the digital exposure device 3, a photoresist may be exposed and developed, and the developed one may be imaged by the imaging device 10 and used as the first output image and the second output image.

[0049] Also, in the above embodiment, the switching speed of the switching display was set to 100 milliseconds. However, the faster the switching speed, the higher the degree of monochromatization of the high-speed switching display image. Therefore, for example, 50 milliseconds or less is preferable, and more preferably, 20 milliseconds or less.

[0050] Also, in a state where at least the functions, characteristics, and effects of the detection device according to the present invention are maintained, a downsized and / or unitized device configuration is incorporated into a device having a DMD as an exposure engine, such as a maskless exposure device or a direct drawing device, so that it can be utilized as a self-diagnosis function when initializing the optical system of the device, and it can also be expected to be utilized for regular maintenance of a device having a DMD as an exposure engine. In that case, the exposure optical system and the inspection optical system may be independent or used in combination. The storage unit can be either independent or combined.

[0051] Also, in the above embodiment, the DMD was used as the image forming element to be inspected. However, in the present invention, the image forming element is not limited to the DMD, and for example, a liquid crystal element or the like may be used.

Explanation of Reference Numerals

[0052] 1…Defective pixel detection device, 10…Imaging device, 11…Control unit, 12…Imaging unit, 13…Memory unit, 14… I / F unit, 15…Cable, 20…Display device, 21…Control unit, 22…Display control unit, 23…Memory unit, 24, 25… I / F unit, 26…Image display unit, 27…PD, 3…Digital exposure device, 30…Light source, 31…DMD, 32…XY table, 33…Micro mirror, 33a…Micro mirror that has transitioned to the ON state, 33b…Micro mirror that has transitioned to the OFF state, 33c~33e…Defective pixels, A…High-speed switching display image, B…Enlarged image of the high-speed switching display image

Claims

1. A storage unit that stores a first output image of the image forming element obtained by inputting a predetermined first pattern signal to the image forming element and imaging the output with an imaging device, and a second output image of the image forming element obtained by inputting a second pattern signal composed of a pixel inversion pattern of the first pattern signal to the image forming element and imaging the output with the imaging device; An image display unit used for an inspector to perform visual inspection, the image display unit being capable of displaying the first output image and the second output image; A display control unit that, in the image display unit, switches and displays the first output image and the second output image at a high speed such that each image cannot be individually recognized at a switching speed of 100 milliseconds or less. A defective pixel detection device.

2. The first pattern signal is a signal in which ON and OFF are alternately repeated, or a signal in which ON and OFF are repeated in units of predetermined pixel blocks, and the second pattern signal is a signal in which ON and OFF of the first pattern signal are inverted. The defective pixel detection device according to Claim 1.

3. The display control unit has a function of enlarging and displaying a partial area of the image displayed on the image display unit, a function of stopping the switching display of the enlarged image and displaying either one of the images, and / or a function of reducing the switching speed of the switching display to a degree where each image can be individually recognized. The defective pixel detection device according to Claim 1 or Claim 2.

4. The image forming element is a digital micromirror device (DMD) that forms an image by reflecting light irradiated from a light source. The defective pixel detection device according to any one of Claims 1 to 3.

5. Prepare a first output image of the image forming element obtained by inputting a predetermined first pattern signal to the image forming element and imaging the output with an imaging device, and a second output image of the image forming element obtained by inputting a second pattern signal composed of a pixel inversion pattern of the first pattern signal to the image forming element and imaging the output with the imaging device. In an image display unit used for an inspector to perform visual inspection, switch and display the first output image and the second output image at a high speed such that each image cannot be individually recognized at a switching speed of 100 milliseconds or less. A defective pixel detection method.

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