Image acquisition system and image acquisition method

Abstract

This image acquisition system comprises: a plurality of light sources that emit light radiated onto an object; a light source control unit that switches, among the plurality of light sources, the light source radiating the light onto the object; and a line scan sensor that detects light from the object irradiated with the light, has a pixel unit having a plurality of pixels arranged at least one-dimensionally therein, and can switch a gain value that amplifies signals from the pixels. The line scan sensor switches the gain value synchronously with the switching of the light source.

Description

[Technical Field]

[0001] The present disclosure relates to an image acquisition system and an image acquisition method. [Background technology]

[0002] Devices that use a line sensor to obtain image information (image signals) and capture an image of an object are known (see, for example, Patent Documents 1 and 2). The device described in Patent Document 1 uses a one-dimensional line sensor with CCDs arranged in a row. White light from a halogen lamp light source is irradiated onto a color negative film, and the transmitted light is projected onto the CCD surface. The R, G, and B signal information projected onto the CCD surface is amplified by an amplifier and converted into digital image data by an A / D conversion circuit. In the device described in Patent Document 2, an analog processing unit performs data sampling, offset adjustment, and gain adjustment. The analog signal is then converted into a digital signal by an A / D converter. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-229136 [Patent Document 2] Japanese Patent Application Laid-Open No. 2007-82013 Summary of the Invention [Problem to be solved by the invention]

[0004] Meanwhile, in systems that capture images of transported objects, there is a demand for technology that can capture images efficiently. One possible solution is to alternately turn on reflected and transmitted illumination and synchronize the scanning timing of the line sensor. However, in this case, two images must be captured to capture an image.

[0005] The present disclosure describes an image acquisition system and method that can efficiently acquire images when using multiple light sources. [Means for solving the problem]

[0006] One aspect of the present disclosure is an image acquisition system that acquires an image of an object being transported, comprising: a plurality of light sources that emit light to be irradiated onto the object; a light source control unit that switches between the light sources that irradiate the object with light from among the plurality of light sources; and a line scan sensor that detects light from the object that has been irradiated with light, the line scan sensor having a pixel unit in which a plurality of pixels are arranged at least one-dimensionally and that is capable of switching a gain value that amplifies a signal from each pixel, and the line scan sensor switches the gain value in synchronization with the switching of the light sources.

[0007] In this image acquisition system, the light source controller switches the light source, and the line scan sensor switches the gain value that amplifies the signal from each pixel in synchronization with the light source switching. This configuration adjusts the gain value of the signal from each pixel output in response to different light sources. For example, it is possible to adjust the brightness levels of two types of images. Therefore, images can be acquired efficiently when using multiple light sources.

[0008] The light source control unit may switch between multiple light sources during a predetermined pixel period based on the width of each pixel and the transport speed of the object. In this case, the light source and gain value are switched during the predetermined pixel period, so that the S / N ratio is maintained at a suitable level.

[0009] The multiple light sources may include at least one reflected light source and at least one transmitted light source. In this case, a combination of reflected light and transmitted light can capture a more accurate image. In particular, since the multiple light sources include a transmitted light source, this is advantageous for capturing images of thin objects such as fabrics, paper, boards, and forms.

[0010] Each of the multiple light sources may emit light of a different wavelength. In this case, images corresponding to the spectral reflectance characteristics of the transported object can be efficiently acquired. For example, this is advantageous for capturing images of medicines, food, vegetables, fruits, etc., to determine the freshness, moisture content, constituents, and foreign matter of the object.

[0011] Another aspect of the present disclosure is an image acquisition method for acquiring an image of an object being transported, comprising an illumination step of illuminating the object with light using a plurality of light sources, and a detection step of detecting light from the illuminated object using a line scan sensor, wherein the line scan sensor has a pixel portion in which a plurality of pixels are arranged at least one-dimensionally, and is capable of switching a gain value that amplifies a signal from each pixel, and in the illumination step, a light source that irradiates the object with light is switched from among the plurality of light sources, and in the detection step, the gain value is switched in synchronization with the switching of the light source.

[0012] According to this image acquisition method, the light source is switched in the illumination process. In the detection process, the line scan sensor switches the gain value for amplifying the signal from each pixel in synchronization with the switching of the light source. This configuration adjusts the gain value of the signal from each pixel output in response to different light sources. For example, it is possible to adjust the brightness levels of two types of images. Therefore, images can be acquired efficiently when multiple light sources are used. [Effects of the Invention]

[0013] According to some aspects of the present disclosure, images can be acquired efficiently when multiple light sources are used. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a diagram illustrating a configuration of an image acquisition system according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is a diagram showing the configuration of the line scan sensor in FIG. [Figure 3] FIG. 3 is a diagram showing an example of the configuration of a pixel in FIG. [Figure 4]FIG. 4 is a timing chart illustrating the operation of the pixel of FIG. [Figure 5] FIG. 5 is a timing chart illustrating an example of the operation of switching the gain value in the line scan sensor. [Figure 6] FIG. 6 is a diagram showing the configuration of an image acquisition system according to another embodiment of the present disclosure. [Figure 7] FIG. 7 is a timing chart illustrating an example of the operation of switching the gain value in the line scan sensor. [Figure 8] FIG. 8 shows images obtained in an imaging test of patterned fabric. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the description of the drawings, the same elements are given the same reference numerals, and duplicated description will be omitted.

[0016] First, an image acquisition system 100 according to an embodiment of the present disclosure will be described with reference to FIG. 1. As shown in FIG. 1, the image acquisition system 100 is a system for acquiring an image of an object A being conveyed in a conveyance direction D. The image acquisition system 100 irradiates the object A with light (visible light) from multiple light sources and acquires an image using a line scan sensor 1. The image acquisition system 100 includes a conveyance device 4 that conveys the object A in the conveyance direction D at a predetermined speed, two reflective light sources 2A and one transmitted light source 2B that respectively emit light to be irradiated onto the object A, and the line scan sensor 1 that detects reflected light from the object A irradiated with light from the reflective light source 2A and that detects transmitted light irradiated with light from the transmitted light source 2B.

[0017] The reflected light source 2A, the transmitted light source 2B, and the line scan sensor 1 all extend elongatedly in the width direction (direction perpendicular to the plane of the paper in FIG. 1 ) perpendicular to the conveying direction D. The object A is an object having a predetermined length (width) in the width direction. The object A is not particularly limited, but an object having a flat shape such as a sheet or plate, or an object that easily transmits light, is more suitable. Furthermore, for example, a cloth-like object such as fabric, or a thin object such as paper, a substrate, or a film is advantageous for imaging. For example, the object A is an object having a flat shape such as a sheet or plate. Examples of the object A include cloth or fabric made of woven or knitted fabric. The object A may also be a nonwoven fabric. In the example shown in FIG. 1 , the object A has a length in the width direction and the conveying direction D.

[0018] The conveying device 4 has a conveying section such as a belt conveyor or a roller conveyor, and a driving section such as a motor that drives the conveying section. The conveying device 4 has a predetermined conveying surface and conveying path. The conveying speed v of the conveying device 4 is controlled by the conveying control section 7, which will be described later.

[0019] The reflective light source 2A and the transmitted light source 2B are each, for example, an LED. The type of these light sources is not particularly limited. Any configuration may be adopted as long as multiple light sources are provided and light is emitted from each light source. The light emitted from the light sources is, for example, visible light, infrared light, or ultraviolet light. Furthermore, the reflective light source 2A and the transmitted light source 2B may be, for example, the same light source. The reflective light source 2A and the transmitted light source 2B have, for example, the same output. The reflective light source 2A and the transmitted light source 2B may also have different outputs. A power supply (not shown) is connected to the reflective light source 2A and the transmitted light source 2B.

[0020] The two reflective light sources 2A are disposed, for example, above the object A (conveying path). For example, one reflective light source 2A and the other reflective light source 2A are disposed on both sides of the line scan sensor 1 in the conveying direction D and are installed at an angle facing each other. The one reflective light source 2A and the other reflective light source 2A are disposed so as to irradiate light from the front side of the object A to an area (an area extending in the width direction) where the optical axis of the line scan sensor 1 intersects with the conveying path. One transmitted light source 2B is disposed, for example, below the object A (conveying path). The transmitted light source 2B is directed, for example, vertically upward. The transmitted light source 2B is disposed so as to emit light from the back side of the object A to an area where the optical axis of the line scan sensor 1 intersects with the conveying path. In this way, the reflective light source 2A is disposed on the same side as the line scan sensor 1 with respect to the conveying path, and the transmitted light source 2B is disposed on the opposite side of the line scan sensor 1 with respect to the conveying path.

[0021] The control unit 5 is a computer having, for example, a processor such as a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), an input / output interface, etc. The control unit 5 has a light source control unit 6, a transport control unit 7, and a camera control unit 8. The light source control unit 6 is connected to the reflective light source 2A and the transmitted light source 2B and controls the on / off (on and off) of each of the reflective light source 2A and the transmitted light source 2B. The light source control unit 6 switches between the reflective light source 2A and the transmitted light source 2B, which light source irradiates the object A. The transport control unit 7 is connected to the drive unit of the transport device 4 and controls the operation of the transport device 4, including the transport speed. The camera control unit 8 is connected to the line scan sensor 1 and controls various operations, described below, such as switching the gain value of the line scan sensor 1. Specifically, the camera control unit 8 controls the sensor control unit 30 of the line scan sensor 1.

[0022] The control of each of the above-mentioned parts by the control unit 5 is set so that the operations of each part to be controlled, i.e., the reflective light source 2A and the transmitted light source 2B, the conveying device 4, and the line scan sensor 1, coincide with predetermined timing (described in detail below).

[0023] Next, the line scan sensor 1 of this embodiment will be described with reference to Fig. 2 and Fig. 3. As shown in Fig. 2, the line scan sensor 1 has a plurality of pixels 101 to 10 N The line scan sensor 1 has a pixel section 3 in which a plurality of pixels are arranged in a line direction (corresponding to the width direction of the conveying device 4). The line scan sensor 1 is a linear image sensor. The pixel section of the line scan sensor 1 may have a configuration in which a plurality of pixels are arranged at least one-dimensionally, and may include pixels arranged in one row or multiple rows.

[0024] The line scan sensor 1 includes N pixels 101 to 10 N The line scan sensor 1 is controlled by the camera control unit 8 and the sensor control unit 30 to read out the image from each pixel 10. n Voltage values ​​corresponding to the amount of light incident on the photodiodes included in the pixels 101 to 100 are sequentially output from the readout circuit 20 to the video line 40. Here, N is an integer of 2 or more, and n is an integer of 1 or more and N or less. N Each pixel 10 has a common configuration and is arranged one-dimensionally at a constant pitch. n includes a photodiode and outputs a voltage value according to the amount of light incident on the photodiode.

[0025] The read circuit 20 includes N hold circuits 211 to 21 N , N switches 221 to 22 N and N switches 231 to 23 N Each hold circuit 21 n Switch 22 n via Pixel 10 n and the switch 22 n Just before pixel 10 changes from an ON state to an OFF state, nEach hold circuit 21 holds the voltage value output from n Switch 23 n is connected to the video line 40 via the switch 23 n is in the ON state, the voltage value it holds is output to the video line 40.

[0026] Switches 221-22 N are controlled by a control signal given from the sensor control unit 30, and are switched on / off at the same timing. N are controlled by a control signal given from the sensor control unit 30, and are sequentially turned on for a certain period of time. N and switches 231 to 23 N In addition to controlling the on / off of each pixel, pixels 101 to 10 N It also controls the operation of each.

[0027] FIG. 3 shows each pixel 10 n 1 is a diagram illustrating a first configuration example of each pixel 10. n The circuit includes a photodiode 50, a MOS transistor 51, a MOS transistor 52, and a source follower amplifier 60. The source follower amplifier 60 includes a MOS transistor 61, an operation control switch 62, and a current source 63.

[0028] The photodiode 50 generates charges in response to incident light. The anode of the photodiode 50 is connected to a second reference potential input terminal to which a second reference potential (e.g., ground potential) is input. The gate of the MOS transistor 61 is connected to the cathode of the photodiode 50 via the MOS transistor 51, and is also connected to a first reference potential input terminal to which a first reference potential (e.g., power supply potential) is input via the MOS transistor 52. The drain of the MOS transistor 61 is connected to the first reference potential input terminal.

[0029] The operation control switch 62 is provided between the source of the MOS transistor 61 and a connection node 64. The operation control switch 62 can be configured by a MOS transistor. The current source 63 is provided between the connection node 64 and a second reference potential input terminal. The current source 63 can be configured to include a MOS transistor, or may be configured by a resistor.

[0030] The on / off of each of the MOS transistors 51 and 52 is controlled by a control signal provided by the sensor control unit 30. When the MOS transistor 52 is in the on state, the gate potential of the MOS transistor 61 is initialized. When the MOS transistors 51 and 52 are in the on state, the charge accumulation in the junction capacitance of the photodiode 50 is initialized. When the MOS transistor 51 is in the on state and the MOS transistor 52 is in the off state, the gate potential of the MOS transistor 61 corresponds to the amount of light incident on the photodiode 50.

[0031] The on / off of the operation control switch 62 is also controlled by a control signal provided by the sensor control unit 30. While the operation control switch 62 is in the on state, a current flows from the first reference potential input terminal to the second reference potential input terminal via the MOS transistor 61, the operation control switch 62, and the current source 63, and a voltage value according to the gate potential of the MOS transistor 61 is output from the connection node 64. Meanwhile, while the operation control switch 62 is in the off state, no current flows through the source follower amplifier 60, and the source follower amplifier 60 is in a power-down state.

[0032] Each pixel 10 n The device further includes a capacitive element 70 and a charge amplifier 80. The charge amplifier 80 includes an amplifier 81, a capacitive section 82, and a reset switch 83.

[0033] The amplifier 81 has an inverting input terminal, a non-inverting input terminal, and an output terminal. A fixed bias potential is input to the non-inverting input terminal of the amplifier 81. The inverting input terminal of the amplifier 81 is connected to the connection node 64 of the source follower amplifier 60 via the capacitive element 70.

[0034] The capacitance unit 82 is provided between the inverting input terminal and the output terminal of the amplifier 81. The capacitance unit 82 accumulates a charge of an amount corresponding to the voltage value output from the source follower amplifier 60. The capacitance value of the capacitance unit 82 may be fixed, but is preferably variable. The capacitance unit 82 is configured to include a capacitance element 84, a capacitance element 85, and a switch 86, thereby making the capacitance value variable. The capacitance element 85 and the switch 86 are connected in series, and these are provided in parallel with the capacitance element 84. The capacitance value of the capacitance unit 82 varies depending on whether the switch 86 is on or off, and the gain (gain value) of the charge amplifier 80 varies. The on / off state of the switch 86 is controlled by a control signal provided by the sensor control unit 30.

[0035] The reset switch 83 is provided in parallel with the capacitance unit 82 between the inverting input terminal and output terminal of the amplifier 81. When the reset switch 83 is in the on state, the charge stored in the capacitance unit 82 is reset. When the reset switch 83 is in the off state, a voltage value according to the amount of charge stored in the capacitance unit 82 and the capacitance value of the capacitance unit 82 is output from the output terminal of the amplifier 81. The on / off of the reset switch 83 is controlled by a control signal provided by the sensor control unit 30.

[0036] FIG. 4 shows each pixel 10 n 1 is a timing chart illustrating the operation of the pixel 10. The operation control switch 62 is switched on / off at regular intervals. While the operation control switch 62 is in the on state, a voltage value according to the gate potential of the MOS transistor 61 is applied to the pixel 10. n is output from switch 22 n Just before pixel 10 changes from an ON state to an OFF state, n The voltage value output from the hold circuit 21 n During the period when the operation control switch 62 is in the OFF state, the N switches 231 to 23 N are sequentially turned on for a certain period of time, and N hold circuits 211 to 21 NThe voltage values ​​held by the voltage detector 41 are sequentially output to the video line 40.

[0037] While the operation control switch 62 is in the ON state, a current flows through the source follower amplifier 60, whereas while the operation control switch 62 is in the OFF state, no current flows through the source follower amplifier 60. The length of the period during which the operation control switch 62 is in the ON state can be, for example, approximately 15% of the ON / OFF switching cycle. The line scan sensor 1 of this embodiment can turn the operation control switch 62 off when not in use, thereby reducing power consumption. When the operation control switch 62 switches from the OFF state to the ON state, the source follower amplifier 60 can be quickly restarted. Therefore, when the source follower amplifier 60 is not in use, the operation control switch 62 can be turned off to power down the source follower amplifier 60.

[0038] Furthermore, by providing the charge amplifier 80, the line scan sensor 1 resets the charge stored in the capacitance section 82 while the operation control switch 62 is in the off state. Also, while the reset switch 83 is in the on state, the switch 86 is switched on / off, changing the capacitance value of the capacitance section 82. That is, the line scan sensor 1 resets the charge stored in each pixel 10. n While the operation control switch 62 is in the OFF state, the reset switch 83 and the switch 86 in the charge amplifier 80 are switched ON / OFF.

[0039] Next, with reference to Fig. 5, a description will be given of the relationship between the timing of switching the reflective light source 2A and the transmitted light source 2B in the image acquisition system 100 and the timing of switching the gain value in the line scan sensor 1. Fig. 5 is a timing chart illustrating an example of the operation of switching the gain value in the line scan sensor.

[0040] As shown in FIG. 5, in the line scan sensor 1, gain switching is possible when the reset switch 83 is in the on state. During this period in which gain switching is possible, the gain value is changed to the required value. The required gain value is, for example, a value that corresponds to the spectral reflectance characteristics of the object being transported. Setting the gain value to an appropriate value improves, for example, the S / N ratio, making it easier to determine whether there is a foreign object or the like in the image.

[0041] 5, pixel-corresponding periods T1 and T2 are also shown. Each pixel-corresponding period T1 or T2 is one pixel period, and each pixel 10 n The predetermined pixel period is determined based on the pixel width of each pixel 10 in the conveying direction D and the conveying speed of the conveying device 4. For example, the predetermined pixel period is determined based on the pixel width of each pixel 10 in the conveying direction D. n It is an integer multiple of the time obtained by dividing the pixel width of each pixel by the transport speed of the object S. In other words, n The longer (more) the pixel width of each pixel 10, the longer the predetermined pixel period. n When the pixel width becomes shorter (less), the predetermined pixel period becomes shorter. Also, when the transport speed becomes faster, the predetermined pixel period becomes shorter. Also, when the transport speed becomes slower, the predetermined pixel period becomes longer. This one pixel period includes the longest possible exposure time (the irradiation time by the reflective light source 2A or the transmitted light source 2B).

[0042] The light source control unit 6 switches between the reflective light source 2A and the transmissive light source 2B during each of the pixel corresponding periods T1 and T2 (illumination step). When the line scan sensor 1 detects reflected light or transmitted light, the camera control unit 8 controls the sensor control unit 30 to switch the gain value in synchronization with the switching of the light source (detection step). The "gain switching" shown in FIG. 5 is performed by the camera control unit 8 for each pixel 10. nThis means changing the capacitance value of the capacitance section 82 in one pixel period. When the light source is switched during one pixel period, the spatial resolution on the object A decreases, but the exposure time for each irradiation does not change, so a decrease in the signal can be prevented. Furthermore, the S / N ratio is maintained by switching the gain value in synchronization with the switching of the light source. In this way, during one pixel period, the gain value is switched a number of times according to the type of light source (two types in this embodiment). For example, if there are n types of light source, the gain value may be switched n times in synchronization with the switching of the light source.

[0043] According to the image acquisition system 100 and the image acquisition method, the light source is switched by the light source control unit 6, and in synchronization with the switching of the light source, the line scan sensor 1 n This allows each pixel 10 to output signals according to different light sources (reflective light source 2A or transmitted light source 2B). n The gain value of the signal from the line scan sensor 1 is adjusted. For example, the brightness levels of two types of images can be adjusted. Therefore, when using multiple light sources, images can be acquired efficiently. There is no need to capture images twice, and an image can be acquired with a single capture. By using the line scan sensor 1 of this embodiment, gain can be switched quickly, and no afterimage remains. In other words, there is no effect of the output on the readout of the next line. Therefore, it is possible to acquire images with higher accuracy.

[0044] The light source control unit 6 controls each pixel 10 n The multiple light sources are switched during a predetermined pixel period based on the width of the object A and the transport speed of the object A. Therefore, the light sources are switched during the predetermined pixel period, and the gain value is also switched, so that the S / N ratio is maintained at an optimum level.

[0045] Next, another embodiment of the present disclosure will be described with reference to Figures 6 and 7. As shown in Figure 6, an image acquisition system 200 differs from the previously described image acquisition system 100 in that an RGB light source 2C that emits light of different wavelengths is provided instead of the reflective light source 2A and the transmissive light source 2B. In the image acquisition system 200, a light source control unit 6 controls the RGB light source 2C to switch between the B light source, the R light source, and the G light source.

[0046] In the image acquisition system 200, as shown in FIG. 7, the light source control unit 6 switches between the RGB light sources 2C during each of the pixel corresponding periods T1 and T2. The camera control unit 8 controls the sensor control unit 30 to switch the gain value in synchronization with the switching of the light source. When the light source is switched during one pixel period, the spatial resolution does not decrease, but the exposure time for each irradiation is shortened, resulting in a decrease in signal. However, by switching the gain value in synchronization with the switching of the light source, the S / N ratio is maintained. In this way, the gain value is switched a number of times during one pixel period according to the type of light source (three types in this embodiment).

[0047] The image acquisition system 200 also achieves the same effects and advantages as the image acquisition system 100. Furthermore, by using multiple light sources that emit light of different wavelengths, it is possible to efficiently acquire images that correspond to the spectral reflectance characteristics of the object being transported. For example, this is advantageous for capturing images of the freshness and moisture content of medicines, food, vegetables, fruits, and the like, as well as the components that make up the object and foreign matter. The RGB light source 2C may be combined with the reflective light source 2A and / or the transmitted light source 2B of the previous embodiment.

[0048] Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments. For example, light sources other than the reflective light source 2A, the transmissive light source 2B, or the RGB light source 2C may be used. The line scan sensor 1 is not limited to the configurations shown in Figures 2 and 3 as long as it is configured to switch gain values ​​in synchronization with switching of the light source. Other known configurations that enable high-speed switching of gain values ​​may also be employed.

[0049] The timing of switching the gain value may be synchronized with the timing of switching the light source, and the gain value may be switched once or multiple times during the exposure time of the same light source.

[0050] In the image acquisition system 100, the number of reflected light sources 2A and / or transmitted light sources 2B may be changed as appropriate. In the image acquisition system 100, the multiple light sources may include one or three or more reflected light sources 2A. The multiple light sources may include two or more transmitted light sources 2B. One or more reflected light sources and one or more transmitted light sources may be combined as appropriate in a single image acquisition system. In the image acquisition system 200, multiple RGB light sources 2C may be provided. Furthermore, in the image acquisition system 100 or the image acquisition system 200, the line scan sensor 1 may detect, as light from the object A, for example, fluorescence or scattered light in addition to reflected light or transmitted light.

[0051] As long as the line scan sensor 1 has a configuration that can switch the gain value in synchronization with switching of the light source, the configuration is not limited to that shown in Figures 2 and 3. Other known configurations that enable high-speed switching of the gain value may also be employed.

[0052] A predetermined pixel period is set for each pixel 10 in the transport direction D. n The gain value may be multiple times (two or three times or more) the time (quotient value) obtained by dividing the pixel width by the transport speed of the object S. Even in this case, multiple light sources are switched during a predetermined pixel period, and the gain value is switched in synchronization with the switching of the light sources. Note that the light source may be switched regardless of the pixel period (regardless of the above-mentioned quotient value). Even in this case, by switching the gain value at least in synchronization with the switching of the light source, an image can be acquired efficiently.

[0053] In an image acquisition system having multiple light sources that emit light of different wavelengths (such as the image acquisition system 200 described above as an example), a configuration may be adopted in which the light source that emits light of one wavelength is a reflective light source, and the light source that emits light of another wavelength is a transmissive light source.

[0054] An imaging test of patterned fabric was conducted using the image acquisition system 100 having the configuration shown in Figures 1 to 3. As shown in Figure 8, an image acquired using a combination of reflected light and transmitted light was able to detect abnormalities such as holes or scratches (see the circles and triangles in the figure). In contrast, an imaging test conducted using only reflected light confirmed scratches but not holes. Furthermore, an imaging test conducted using only transmitted light confirmed scratches and holes, but because the fabric has numerous thin areas, these thin areas appear to be the same as holes and scratches. [Explanation of symbols]

[0055] 1... line scan sensor, 2A... reflected light source, 2B... transmitted light source, 2C... RGB light source, 3... pixel unit, 4... conveyance device, 5... control unit, 6... light source control unit, 7... conveyance control unit, 8... camera control unit, 101 to 10 N ...pixel, 20...readout circuit, 40...video line, 50...photodiode, 60...source follower amplifier, 80...charge amplifier, 81...amplifier, 82...capacitor section, 100, 200...image acquisition system, A...object.

Claims

1. 1. An image acquisition system for acquiring images of a conveyed object, a plurality of light sources that emit light to be irradiated onto the object; a light source control unit that switches the light source that irradiates the object with the light from among the plurality of light sources; a line scan sensor that detects light from the object illuminated with the light, the line scan sensor having a pixel section in which a plurality of pixels are arranged at least one-dimensionally and capable of switching a gain value that amplifies a signal from each pixel; An image acquisition system in which the line scan sensor switches the gain value in synchronization with switching of the light source.

2. The image acquisition system of claim 1 , wherein the light source control unit switches between the plurality of light sources during a predetermined pixel period based on the width of each pixel and a transport speed of the object.

3. The image acquisition system of claim 1 or 2, wherein the plurality of light sources includes at least one reflected light source and at least one transmitted light source.

4. The image acquisition system according to any one of claims 1 to 3, wherein each of the plurality of light sources emits light of a different wavelength.

5. 1. An image acquisition method for acquiring an image of a transported object, comprising: an irradiation step of irradiating the object with light using a plurality of light sources; a detection step of detecting light from the object illuminated with the light by a line scan sensor, the line scan sensor has a pixel section in which a plurality of pixels are arranged at least one-dimensionally, and is capable of switching a gain value for amplifying a signal from each pixel; In the irradiating step, a light source that irradiates the object with the light is switched among the plurality of light sources; In the detection step, the gain value is switched in synchronization with switching of the light source.

Images