CN107079074B

CN107079074B - Imaging device and inspection device

Info

Publication number: CN107079074B
Application number: CN201580053455.2A
Authority: CN
Inventors: 高田仁夫; 黑泽昭夫
Original assignee: Kurashiki Spinning Co Ltd
Current assignee: Kurashiki Spinning Co Ltd
Priority date: 2014-10-03
Filing date: 2015-09-16
Publication date: 2020-04-28
Anticipated expiration: 2035-09-16
Also published as: TWI737582B; WO2016052190A1; TW201618529A; CN107079074A

Abstract

The invention provides an imaging device capable of performing calibration corresponding to a plurality of imaging conditions. The imaging device is provided with an imaging unit for obtaining image data of an object to be imaged; a storage unit that stores a plurality of calibration data for calibrating at least one of the image pickup unit and the image data; and a calibration unit that switches the plurality of calibration data and performs calibration of at least one of the imaging unit and the image data.

Description

Imaging device and inspection device

Technical Field

The present invention relates to an imaging apparatus and an inspection apparatus having a calibration unit, and more particularly, to an imaging apparatus and an inspection apparatus having a shading correction unit.

Background

As an inspection apparatus for inspecting a foreign substance, a flaw, or the like present on a surface of an object to be inspected based on image data obtained by imaging the object to be inspected, there is an inspection apparatus for sequentially switching a plurality of illuminations in synchronization with an imaging timing to perform imaging (for example, see patent document 1).

In recent years, a technique of correcting unevenness in brightness of image data obtained by an imaging apparatus using an imaging device such as a CCD or a CMOS has been discussed. For example, as a technique for correcting sensitivity of an image pickup device, variation in illumination, and brightness unevenness caused by a lens or the like, shading correction is known (for example, see patent document 2). This shading correction is a technique of correcting a variation in sensitivity characteristic of each pixel of the line sensor, and corrects a variation in sensitivity of each pixel by normalizing image data based on white reference data and black reference data. Therefore, in the shading correction, white reference data and black reference data are provided for each of the pixels of the line sensors (R, G, B).

Further, there is a data processing circuit having 3 black point correction circuits for the color line sensors provided for the respective RGB colors (see, for example, patent document 3).

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2012 and 42297;

patent document 2: japanese patent laid-open publication No. 8-307672;

patent document 3: japanese patent laid-open publication No. 2009-94928.

Disclosure of Invention

Problems to be solved by the invention

In the above-described shading correction technique, although correction data for each of the RGB image pickup elements is provided for each of the 3 image pickup elements of RGB, these correction data are correction data under a specific illumination condition and do not include correction data for each of a plurality of illumination conditions.

However, if the lighting conditions during imaging are different, the data for shading correction also changes. Therefore, when imaging is performed by switching a plurality of imaging conditions, such as when imaging is performed by switching a plurality of illuminations, it is difficult to perform accurate shading correction using only the correction data for 1 imaging condition.

The invention aims to provide an imaging device capable of performing calibration corresponding to a plurality of imaging conditions.

Means for solving the problems

An imaging device according to the present invention includes: an image pickup unit that obtains image data of an object to be picked up; a storage unit that stores a plurality of calibration data for calibrating at least one of the imaging unit and the image data; and a calibration unit that performs calibration of at least one of the imaging unit and the image data by switching the plurality of calibration data.

Effects of the invention

According to the imaging apparatus of the present invention, at least one of the imaging unit and the image data can be calibrated by using the calibration data corresponding to the imaging conditions, and therefore, appropriate calibration corresponding to the imaging conditions can be performed.

Drawings

Fig. 1 is a block diagram showing the configuration of an image pickup apparatus according to embodiment 1.

Fig. 2 is a block diagram showing a configuration of an imaging system with illumination including the imaging device of embodiment 2.

Fig. 3 is a schematic diagram illustrating an operation of a shading correction (shading correction) unit of the image pickup apparatus of fig. 2.

Fig. 4 is a graph showing a white reference and a black reference of each pixel constituting the black point correction data, an image signal before correction, and an image signal after correction.

FIG. 5 shows a sequence of switching m_maxA flow chart of an imaging method for obtaining calibrated image data by performing calibration in a conversion (switching) imaging in which imaging is performed by illumination.

Fig. 6 is a block diagram showing the structure of the inspection apparatus according to embodiment 3.

Fig. 7 is a block diagram showing the structure of the inspection apparatus according to embodiment 4.

Fig. 8 is a block diagram showing the structure of the inspection apparatus according to embodiment 5.

Detailed Description

An imaging device according to a first aspect is characterized by comprising: an image pickup unit that obtains image data of an object to be picked up; a storage unit that stores a plurality of calibration data for calibrating at least one of the imaging unit and the image data; and a calibration unit that performs calibration of at least one of the imaging unit and the image data by switching the plurality of calibration data.

In the imaging device according to the second aspect, in the first aspect, the calibration data may be black dot correction data for performing black dot correction on the image data.

In this case, the calibration unit may be a black point correction unit that performs black point correction using the black point correction data.

In an imaging apparatus according to a third aspect, in the first aspect, the calibration data may be calibration data relating to a storage time of an imaging element in the imaging unit.

In this case, the calibration means may be means for adjusting the accumulation time of the image pickup device in the image pickup means using calibration data relating to the accumulation time.

An imaging apparatus according to a fourth aspect may be arranged such that, in the first aspect, the calibration data is calibration data relating to a gain in the imaging means.

In this case, the calibration means may be means for adjusting the gain in the imaging means using calibration data relating to the gain.

An imaging apparatus according to a fifth aspect is the imaging apparatus according to any one of the first to fourth aspects, wherein the calibration data is calibration data for performing calibration in accordance with an illumination condition at the time of imaging.

In this case, the calibration unit may perform calibration by switching from the plurality of calibration data to calibration data corresponding to the illumination condition at the time of imaging, in accordance with the switching of the illumination condition at the time of imaging.

With the above configuration, calibration using calibration data corresponding to each lighting condition can be performed. Further, by performing calibration inside the imaging device, highly accurate correction processing using a high-gradation image signal can be performed without being affected by lowering of gradation at the time of external output.

An imaging apparatus according to a sixth aspect is the imaging apparatus according to the fifth aspect, wherein the calibration means may switch to calibration data corresponding to the illumination condition at the time of imaging in synchronization with switching of the illumination condition at the time of imaging.

With the above configuration, the calibration data is switched in synchronization with the switching of the lighting conditions, whereby the calibration corresponding to each of the lighting conditions can be sequentially executed.

An imaging apparatus according to a seventh aspect is the imaging apparatus according to the first aspect, wherein the calibration means may switch the calibration data in synchronization with imaging by the imaging means.

An image pickup apparatus according to an eighth aspect is the image pickup apparatus according to the first aspect, wherein the image pickup apparatus further includes an output unit that outputs the image signal of the calibrated image data to the outside while reducing a gray level of the image signal.

An inspection apparatus according to a ninth aspect includes the imaging apparatus according to any one of the first to eighth aspects.

An inspection apparatus according to a tenth aspect is characterized by comprising: an illumination unit capable of illuminating the object to be inspected by switching between a plurality of different illumination conditions; an imaging unit that obtains image data of the object illuminated by the illumination unit; a storage unit that stores a plurality of calibration data for calibrating at least one of the image capturing unit and the image data in correspondence with the plurality of lighting conditions; a calibration unit configured to perform calibration of at least one of the imaging unit and the image data by switching the plurality of calibration data in accordance with switching of illumination conditions during imaging; and an inspection unit that performs inspection of the object to be inspected based on the calibrated image data.

In the inspection apparatus according to an eleventh aspect, in the tenth aspect, the illumination unit may include a plurality of illumination devices that illuminate under different illumination conditions.

In the inspection apparatus according to a twelfth aspect, in the tenth or eleventh aspect, the calibration data may be black dot correction data for performing black dot correction on the image data.

In the inspection apparatus according to a thirteenth aspect, in the tenth or eleventh aspect, the calibration data may be calibration data relating to a storage time of an image pickup device in the image pickup unit.

In the inspection apparatus according to a fourteenth aspect, in the tenth or eleventh aspect, the calibration data may be calibration data relating to a gain in the imaging unit.

In the inspection apparatus according to a fifteenth aspect, in the tenth to fourteenth aspects, the calibration unit may switch to the calibration data corresponding to the illumination condition at the time of imaging in synchronization with switching of the illumination condition at the time of imaging.

In the inspection apparatus according to a sixteenth aspect, in the above-described tenth to fifteenth aspects, the calibration unit may switch the calibration data in synchronization with imaging by the imaging unit.

Hereinafter, an imaging apparatus and an inspection apparatus according to an embodiment of the present invention will be described with reference to the drawings. In the drawings, substantially the same members are denoted by the same reference numerals.

(embodiment mode 1)

< imaging apparatus >

Fig. 1 is a block diagram showing the configuration of an image pickup apparatus 10 according to embodiment 1. The imaging device 10 includes: the image pickup apparatus includes an image pickup unit 1 that obtains image data of an object 5 to be picked up, a storage unit 2 that stores

calibration data

2a, 2b, 2c, 2d for calibrating at least one of the image pickup unit 1 and the image data, and a calibration unit 3 that calibrates at least one of the image pickup unit 1 and the image data using the calibration data. Further, the image processing apparatus may further include an output unit 4 for outputting the image signal of the calibrated image data to the outside.

In this imaging apparatus, since at least one of the imaging unit 1 and the image data can be calibrated by using the calibration data corresponding to the imaging conditions, it is possible to perform appropriate calibration corresponding to the imaging conditions. The imaging device 10 includes: since the memory unit 2 and the calibration unit 3 having the

calibration data

2a, 2b, 2c, and 2d are provided, the calibration can be performed in the state of high-precision image data (high-gradation image signal) in the imaging device 10 without being affected by the low-gradation processing at the time of external output, as compared with the case of performing processing by outputting the data to the outside, and highly-precise calibrated image data can be obtained.

Hereinafter, each component constituting the imaging device 10 will be described.

< imaging means >

The imaging unit 1 may include an imaging device 1a such as a CCD or a CMOS, and an imaging control unit 1b that controls the imaging device 1 a. The imaging unit 1 may be a line sensor or an area sensor. For example, when the object 5 is conveyed, a line sensor may be used to perform scanning at high speed along the conveyance direction. The line sensor may be a single monochrome line sensor (monochrome line sensor).

< storage cell >

The memory unit 2 has a plurality of

calibration data

2a, 2b, 2c, 2 d. The

calibration data

2a, 2b, 2c, 2d are data for calibrating at least one of the imaging unit 1 and the image data. The

calibration data

2a, 2b, 2c, 2d may be black dot correction data, for example. Alternatively, the calibration data may be calibration data for adjusting the brightness of the entire image, for example, calibration data relating to the accumulation time of the imaging element 1a in the imaging unit 1. The calibration data may be calibration data relating to a gain (gain) in the imaging unit 1. In embodiment 2, a case where the calibration data is black dot correction data will be described in detail.

< calibration Unit >

At least one of the imaging unit 1 and the image data is calibrated by the calibration unit 3 using the calibration data. The calibration unit 3 may be implemented as a physical structure by a circuit, for example. Alternatively, the present invention may be implemented by computer software operating on a computer. The computer may have a function that requires the minimum necessary to be able to execute the above calibration operation among a CPU, a ROM, a RAM, a hard disk, an input/output interface, and the like, which are common components.

Further, when the calibration data is calibration data relating to the accumulation time of the image pickup device in the image pickup unit 1, the calibration unit 3 can obtain image data by changing the accumulation time of the image pickup device in the image pickup unit 1 based on the calibration data and performing exposure and image pickup. In practice, the calibration means 3 reads any of the

calibration data

2a, 2b, 2c, and 2d of the set values relating to the accumulation time from the storage means 2, and sets the value in the imaging means 1, thereby changing the accumulation time of the imaging element 1 a.

When the calibration data is calibration data relating to the gain in the imaging unit 1, the calibration unit 3 changes the gain (analog gain or digital gain) of the imaging unit 1 based on the calibration data, and performs exposure and imaging to obtain image data. In practice, the calibration means 3 reads any of the

calibration data

2a, 2b, 2c, and 2d of the set values relating to the gain from the storage means 2, and sets the value in the imaging means 1, thereby changing the gain.

The calibration unit 3 may switch the calibration data in synchronization with the imaging by the imaging unit 1.

< output Unit >

The image signal of the calibrated image data is output to the outside through the output unit 4.

In the output section 4, the transmission rate may be limited when externally outputting the image signal, and the image signal may be subjected to low gradation processing and externally output the image signal. In this case, the accuracy of the high-accuracy image signal is reduced and the image signal is output.

In the imaging apparatus 10, as described above, the calibration can be performed in the state of high-precision image data (high-gradation image signal) inside the imaging apparatus 10 without being affected by the low-gradation processing at the time of the external output, and highly-precise calibrated image data can be obtained. Although the calibrated image data is subjected to the low gradation processing in the subsequent external output, the influence of the accuracy degradation can be suppressed because the calibrated image data is not affected by the low gradation processing, for example, the significant bit number reduction (calibration) or the like, as compared with the case where the calibration is performed after the low gradation processing.

< buffer memory >

In the imaging apparatus 10, a buffer memory may be provided between the imaging unit 1 and the calibration unit 3. The buffer memory can temporarily hold the image signal from the image pickup unit 1. Thus, even when the timing of imaging and the timing of calibration are not synchronized, the image data before calibration can be held over a predetermined period.

(embodiment mode 2)

< imaging apparatus >

Fig. 2 is a block diagram showing the configuration of an imaging system 30 with illumination including the imaging device 10a of embodiment 2. The imaging device 10a includes: an image pickup unit 11 that obtains image data of an object 5 to be picked up, a storage unit 12 that stores black

dot correction data

12a, 12b, 12c, 12d for performing black dot correction on the image data, and a black dot correction unit 13 that performs black dot correction on the image data using the black

dot correction data

12a, 12b, 12c, 12 d. Further, the image processing apparatus may further include an output unit 14 for outputting the image signal of the corrected image data to the outside.

In the imaging device 10a, since the image data can be corrected for black dots by the black dot correction data corresponding to the illumination condition at the time of imaging, appropriate correction according to the imaging condition can be performed. The imaging device 10a further includes, in its interior: a memory unit 12 having black

dot correction data

12a, 12b, 12c, 12d, and a black dot correction unit 13. Therefore, compared to the case where the image data is output to the outside and processed, the shading correction can be performed in the state of high-precision image data (high-gradation image signal) inside the imaging device without being affected by the low-gradation processing at the time of the external output, and highly-precise corrected image data can be obtained.

Hereinafter, each component constituting the imaging device 10a will be described.

< imaging means >

As the imaging unit 11, substantially the same unit as the imaging unit 1 in embodiment 1 can be used. Therefore, detailed description is omitted.

Note that, although the lens (lens) 15 is shown in fig. 2 as being separated from the imaging unit 11, the lens 15 is shown in a manner separated from the imaging unit 11 for convenience only in order to show an imaging state in which an image is captured from substantially directly above. The lens 15 may be included in the imaging unit 11. In fig. 2, the image pickup apparatus is shown as a whole, but, for example, a head separation type configuration (a configuration in which the image pickup unit 11 and the lens 15 are a head and a processing unit at a subsequent stage is separated from the head as a controller unit) is also possible.

< storage cell >

The memory cell 12 has a plurality of black

dot correction data

12a, 12b, 12c, 12 d. Each of the black

point correction data

12a, 12b, 12c, and 12d is composed of a white reference and a black reference for each pixel of the image pickup element 11a of the image pickup unit 11 for each lighting condition. For example, fig. 4 is a graph showing a white reference W and a black reference B of each pixel constituting the black point correction data. In fig. 4, the horizontal axis represents pixel position and the vertical axis represents luminance.

Further, the first black point correction data 12a, the second black point correction data 12b, the third black point correction data 12c, and the fourth black point correction data 12d correspond to illumination conditions by illumination L1 (18 a), illumination L2 (18 b), illumination L3 (18 c), and illumination L4 (18 d), respectively. The number of illuminations and the number of black point correction data need not necessarily match, and a plurality of black point correction data corresponding to combinations of various illumination conditions may be stored as many as necessary, and appropriate black point correction data may be used in accordance with switching of the illumination conditions.

The white reference W of each pixel constituting the black point correction data can be obtained by imaging using a white calibration plate for each illumination. Alternatively, the white reference W may be obtained by directly irradiating the imaging element 11a of the imaging unit 11 with light from each illumination and imaging the light. The black reference B can be obtained by performing imaging in a state where light is not completely introduced into the imaging element 11a of the imaging unit 11, for example, in a state where the lens 15 is covered with a cover. Alternatively, the black reference B may be obtained by imaging the white reference W using a black calibration plate for each illumination. The black reference B may use common data for all the

illuminations

18a, 18B, 18c, and 18 d.

< Black Point correction Unit >

The black point correction unit 13 performs black point correction on the image data using the black point correction data. The shading correction unit 13 may be realized by a physical structure using a circuit, for example. Alternatively, the present invention may be implemented by computer software operating on a computer. The computer may have a function that requires the minimum necessary to be able to execute the above-described correction operation among a CPU, a ROM, a RAM, a hard disk, an input/output interface, and the like, which are general constituent elements.

Further, when the black point correction unit 13 is configured as a circuit, switching between a plurality of black point correction circuits provided for each lighting condition in synchronization with the lighting of the image pickup and the lighting makes it unnecessary to read out the black

point correction data

12a, 12b, 12c, and 12d from the storage unit 12 every time the lighting is switched, and thus higher-speed correction processing can be performed.

Fig. 3 is a schematic diagram illustrating the operation of the black point correction unit 13 of the imaging apparatus 10a of fig. 2. Fig. 4 is a graph showing an example of: the white reference Wi and the black reference Bi of each pixel i constituting 1 piece of black point correction data are included in all the pixels as an elemental white reference W and black reference B, respectively, the image signal S before correction of each pixel i is included in all the pixels as an elemental image signal S, and the image signal S 'after correction of each pixel i is included in all the pixels as an elemental image signal S'.

The shading correction by the shading correction unit 13 will be described below.

(a) The black point correction unit 13 stores the image signal S and the white reference W and the black reference B constituting the black point correction data corresponding to the illumination condition as the image capturing condition in the line memories 22a, 22B, and 22c, respectively.

(b) Next, the difference (Wi-Bi) between the white reference Wi and the black reference Bi and the difference (Si-Bi) between the image signal Si and the black reference Bi are calculated for each pixel i.

(c) Then, the difference (Si-Bi) between the image signal Si and the black reference Bi is divided by the difference (Si-Bi) between the white reference Wi and the black reference Bi for each pixel i to obtain a normalized value (Si-Bi)/(Wi-Bi).

(d) Multiplying the normalized value by the maximum value 2 of the n-bit image signal SiⁿValue after-1 (Si-Bi)/(Wi-Bi) × (2)ⁿ-1) output as a corrected image signal S' i.

With the above, the shading correction according to the illumination condition can be performed.

< output Unit >

As the output means 14, substantially the same means as the output means 4 in embodiment 1 can be used. Therefore, detailed description is omitted.

< buffer memory >

As the buffer memory, substantially the same memory as that in embodiment 1 can be used. Therefore, detailed description is omitted.

< imaging System with illumination >

The imaging system 30 with illumination includes: the imaging apparatus 10a, the synchronization signal generation unit 16, the illumination control unit 17, and the

illuminations

18a, 18b, 18c, and 18d of embodiment 2. As described in japanese patent laid-open No. 2012 and 42297, the imaging system 30 with illumination can be driven by a so-called conversion imaging method in which imaging is performed while switching the plurality of

illuminations

18a, 18b, 18c, and 18d in synchronization with the imaging timing of the imaging unit 11.

The imaging system 30 with illumination may be driven without synchronizing the imaging timing of the imaging unit 11 with the switching of the plurality of

illuminations

18a, 18b, 18c, and 18d, and the synchronization of the imaging timing and the switching of the illuminations is not essential.

The following describes each component constituting the imaging system 30 with illumination.

< imaging apparatus >

The imaging device 10a can be used as the imaging device 10a, and therefore, the description thereof is omitted.

< illumination >

The imaging system 30 with illumination includes illumination L1 (18 a) which is diffuse reflected light, illumination L2 (18 b), illumination L3 (18 c), and illumination L4 (18 d) which is specular reflected light. Further, the illumination L1 (18 a), the illumination L2 (18B), and the illumination L3 (18 c) emit red light (R), green light (G), and blue light (B) corresponding to R, G, B, respectively, and the illumination L4 (18 d) emits white light.

The number of

illuminations

18a, 18b, 18c, 18d is not limited to 4. For example, the number of illuminations may be 1, 2, 3, or 5 or more. In the above example, the light source is configured by using a combination of 3 diffuse reflection lights and 1 specular reflection light, but the present invention is not limited to this, and for example, the transmitted light may be combined.

< synchronization Signal Generation Unit >

The synchronization signal generation unit 16 sends synchronization signals to the imaging unit 11, the shading correction unit 13, and the illumination control unit 17, and synchronizes the switching of the

illuminations

18a, 18b, 18c, 18d with the timing of imaging. After the end of imaging, the switching to the next illumination is synchronized with the shading correction for the image signal imaged with the first 1 illumination. Therefore, the switching of the

illuminations

18a, 18b, 18c, 18d is synchronized with the reading of the black

spot correction data

12a, 12b, 12c, 12d corresponding to the previous 1 illumination.

The synchronization signal generation unit 16 may be provided in either the imaging device 10a or the illumination control unit 17. Alternatively, they may be provided separately.

< illumination control Unit >

The

lighting

18a, 18b, 18c, 18d is controlled by a lighting control unit 17. The illumination control unit 17 sequentially switches the

illuminations

18a, 18b, 18c, 18d based on the synchronization signal. The control of the illumination in the conversion imaging is not limited to the sequential switching of the plurality of illuminations, and for example, 2 or more illuminations may be combined to perform the illumination at the same time, or 1 illumination may be irradiated a plurality of times while switching the wavelength or the brightness.

< conveying Unit >

The conveying unit 19 may be, for example, a unit that conveys the object 5 in one direction. The conveying unit 19 may be, for example, a belt conveyor (belt conveyor).

< imaging method >

FIG. 5 shows a sequence of switching m_maxA flow chart of an imaging method for obtaining calibrated image data by performing calibration in a conversion imaging in which imaging is performed by illumination.

(1) The black point correction data, the accumulation time, and the gain for each illumination are stored in the storage unit in advance (S01). The acquisition of the black point correction data corresponding to each illumination corresponds to the case where the white reference and the black reference are obtained for each illumination as described above. The relationship between the luminance of each illumination, the accumulation time, and the gain is also obtained for the accumulation time and the gain, and calibration data is obtained thereby.

(2) As the initial setting, n =1 and m =1 are set (S02).

(3) The imaging of the n-th line is started (S03).

(4) The accumulation time and gain are set using the mth calibration data (S04). For example, when the illumination is too bright due to specular reflection light or the like, the accumulation time of the image pickup device 11a of the image pickup unit 11 may be reduced or the gain may be reduced, and conversely, when the illumination is too dark due to transmitted light or the like, the accumulation time of the image pickup device 11a may be increased or the gain may be increased.

(5) The mth illumination is turned on (S05).

(6) The image is exposed and captured, and an image signal is obtained (S06).

(7) The mth illumination is extinguished (S07).

(8) The image signal is subjected to shading correction using the mth calibration data (shading correction data) and output (S08).

(9) Judging whether the number m of the illumination is m_max(S09) at m_maxIn the case of (1), the number m of illumination is reset to 1 (S10), and if not, m_maxIn the case of (1), m is added (m = m + 1) (S11), and the process returns to step S04. The resetting of the illumination number m (S10) is not limited to the case of being performed at this stage. For example, the number m of illumination may be reset at the same time when the imaging of the n-th line is started (S03).

(10) After the number m of the illumination is reset to 1, it is determined whether the number n of the line is n_max(S12) at n_maxThe image capturing is ended in the case of (1). Number n of online is not n_maxIn the case of (1), n is increased (n = n + 1) (S13), and the process returns to step S03.

By the above, m is switched in sequence_maxIn the conversion imaging in which imaging is performed by individual illumination, calibration data (black point correction data, accumulation time, gain) corresponding to each illumination condition can be used for imaging units and imagesAt least one of the data is calibrated to obtain calibrated image data.

According to the above-described imaging method, it is possible to simultaneously correct sensitivity unevenness of each pixel of the imaging unit 11 such as a line sensor and illumination unevenness due to a difference in illumination conditions inside the imaging device 10 a.

In the above-described imaging method, the case where the shading correction, the accumulation time, and the gain are all calibrated has been described, but it is not necessary to calibrate all of them. Any one of the shading correction, the accumulation time, and the gain, or a combination thereof may be calibrated.

(embodiment mode 3)

< inspection apparatus >

Fig. 6 is a block diagram showing the structure of the inspection apparatus 40 according to embodiment 3. The inspection device 40 includes: an imaging device 10b, a synchronization signal generation unit 16, an illumination control unit 17,

illuminations

18a, 18b, 18c, 18d as a plurality of illumination devices, and a control device 20. As described in japanese patent laid-open No. 2012-42297, the inspection apparatus 40 can be driven in a so-called transition imaging method in which imaging is performed while switching the illumination conditions by the plurality of

illuminations

18a, 18b, 18c, and 18d in synchronization with the imaging timing of the imaging unit 1 in the imaging apparatus 10b based on the synchronization signal generated by the synchronization signal generation unit 16. The plurality of

illuminations

18a, 18b, 18c, 18d can be controlled by the illumination control unit 17.

The inspection apparatus 40 includes: a storage unit 2 that stores

calibration data

2a, 2b, 2c, 2d corresponding to each illumination condition for calibrating at least one of the imaging unit 1 and the image data, and a calibration unit 3 that calibrates at least one of the imaging unit 1 and the image data using the calibration data. Thus, at least one of the imaging unit 1 and the image data can be calibrated by using the calibration data corresponding to the illumination condition, and therefore, appropriate calibration corresponding to the illumination condition can be performed.

The storage means 2 and the calibration means 3 are configured to be included in the control device 20, but are not limited thereto. For example, as shown in embodiment 2, the imaging device 10b may be configured to include the same. The control device 20 further includes an inspection unit 25 that performs inspection of the object to be inspected based on the calibrated image data.

The inspection device 40 may be driven without synchronizing the imaging timing of the imaging unit 1 in the imaging device 10b with the switching of the illumination conditions by the plurality of

illuminations

18a, 18b, 18c, and 18d, and the synchronization of the imaging timing and the switching of the illumination conditions is not essential.

< imaging apparatus >

The imaging device 10b includes an imaging unit 1 for obtaining image data of the object to be inspected, and may further include an output unit 4 for reducing the gradation of an image signal of the image data and outputting the image signal to the outside.

< imaging means >

The imaging unit 1 may include an imaging device 1a such as a CCD or a CMOS, and an imaging control unit 1b that controls the imaging device 1 a. The imaging unit 1 may be a line sensor or an area sensor. For example, when the test object is conveyed, a line sensor may be used to perform scanning at high speed along the conveying direction. The line sensor may also be a single monochromatic line sensor.

Although the lens 15 is shown as being separated from the image pickup unit 1 in fig. 1, this is merely to show the image pickup state in which an image is picked up from substantially directly above, and the lens 15 is shown as being separated from the image pickup unit 1 for convenience. The lens 15 may be included in the imaging unit 1. In fig. 1, the image pickup apparatus is shown as a whole, but, for example, a head separation type configuration (a configuration in which the image pickup unit 1 and the lens 15 are a head and a processing unit at a subsequent stage is separated from the head as a controller unit) is also possible.

< output Unit >

The image signal of the image data is output to the outside of the imaging apparatus 10b by the output unit 4.

< control device >

The control device 20 includes a storage unit 2, a calibration unit 3, and an inspection unit 25. Further, a buffer memory may be provided between the imaging unit 1 and the calibration unit 3.

< storage cell >

The storage unit 2 has a plurality of

calibration data

2a, 2b, 2c, 2d corresponding to each lighting condition. The

calibration data

2a, 2b, 2c, 2d may be black dot correction data, for example. Alternatively, the calibration data may be calibration data for adjusting the brightness of the entire image, for example, calibration data relating to the accumulation time of the imaging element 1a in the imaging unit 1. Further, the calibration data may be calibration data relating to a gain in the imaging unit 1. In embodiment 4, a case where the calibration data is black dot correction data will be described in detail.

< calibration Unit >

calibration data

The calibration unit 3 may switch the calibration data in synchronization with the switching of the illumination conditions by the

illuminations

18a, 18b, 18c, and 18d and the imaging by the imaging unit 1.

< inspection means >

The inspection of the object 5 is performed by the inspection unit 25 based on the calibrated image data. For example, the shape, pattern, color, and the like of the object 5 may be inspected for the image data by a pattern matching (pattern matching) method. In addition, various image processing filters may be used to extract defects of the inspection object 5.

Further, by combining a plurality of image data captured under different illumination conditions and performing inspection, it is possible to inspect a defect that cannot be discriminated only by image data obtained under a single illumination condition. For example, a plurality of image data obtained by imaging the test object 5 under illumination of different wavelengths may be represented by different colors, and the image data may be combined to create a color image, and the test of the test object 5 may be performed based on the combined color image.

The image data after calibration is, for example, "image data after calibration" when calibration is performed for image data related to image data, for example, calibration of image data such as shading correction, and means "image data obtained using an image pickup unit after calibration" when calibration is performed for an image pickup unit for accumulation time or gain.

In this case, according to the inspection apparatus 40 of the present invention, since calibration is performed using calibration data corresponding to the illumination condition at the time of imaging, it is possible to easily combine a plurality of image data imaged under different illumination conditions.

< buffer memory >

In the control device 20, a buffer memory may be provided between the imaging unit 1 and the calibration unit 3. The buffer memory can temporarily hold the image signal from the image pickup unit 1. Thus, even when the timing of imaging and the timing of calibration are not synchronized, the image data before calibration can be held over a predetermined period.

< illumination Unit >

The illumination unit can illuminate the inspection object 5 by switching between a plurality of different illumination conditions. The inspection apparatus 40 includes, as an illumination unit: illumination L1 (18 a), illumination L2 (18 b), illumination L3 (18 c) as an illumination device that is diffusely reflected light, and illumination L4 (18 d) as an illumination device that is specularly reflected light. Further, the illumination L1 (18 a), the illumination L2 (18B), and the illumination L3 (18 c) emit red light (R), green light (G), and blue light (B) corresponding to R, G, B, respectively, and the illumination L4 (18 d) emits white light.

The number of illumination units is not limited to 4

illumination units

18a, 18b, 18c, and 18 d. For example, the number of the lighting devices may be 1, 2, 3, or 5 or more. In the above example, the illumination unit is configured by using a combination of 3 diffuse reflection lights and 1 specular reflection light, but the present invention is not limited to this, and for example, a combination of transmitted lights (not shown) may be used. Further, diffuse reflection light having different incident angles may be provided for the same diffuse reflection light. This makes it possible to inspect both a foreign object that is easily visible when the incident angle is shallow and a foreign object that is easily visible when the incident angle is deep.

< synchronization Signal Generation Unit >

The synchronization signal generation unit 16 transmits a synchronization signal to the imaging unit 1, the calibration unit 3, and the illumination control unit 17, and synchronizes the switching of the illumination conditions by the

illuminations

18a, 18b, 18c, and 18d with the timing of imaging. After the end of imaging, the switching to the next illumination condition is synchronized with the calibration of the image signal imaged with the previous 1 illumination condition. Therefore, the switching of the

illuminations

18a, 18b, 18c, 18d is synchronized with the reading of the

calibration data

2a, 2b, 2c, 2d corresponding to the previous 1 illumination condition.

The synchronization signal generation unit 16 may be provided in any of the imaging device 10b, the illumination control unit 17, and the control device 20. Alternatively, they may be provided separately.

< illumination control Unit >

The

lighting

illuminations

18a, 18b, 18c, 18d based on the synchronization signal. The control of the illumination condition in the conversion imaging is not limited to the sequential switching of the plurality of illuminations, and for example, 2 or more illuminations may be combined to perform the illumination at the same time, or 1 illumination may be irradiated a plurality of times while switching the wavelength or the brightness.

The illumination control unit 17 may be provided in either the imaging device 10b or the control device 20. Alternatively, they may be provided separately.

< conveying Unit >

The transport unit 19 may be a unit that transports the test object in one direction, for example. The conveying unit 19 may be a belt conveyor, for example.

In the inspection apparatus 40, the conveyance unit 19 is not necessarily configured. For example, when a line sensor is used as the imaging unit 1, the entire object can be imaged by conveying the object in one direction by the conveying unit 19. On the other hand, when the area sensor is used as the imaging unit 1, the entire object can be directly imaged, and therefore, the conveyance unit 19 is not required.

< imaging method >

At sequential switching m_maxObtaining calibrated image data by performing calibration in conversion imaging in which imaging is performed by illuminationThe imaging method is substantially the same as the flowchart of the imaging method of fig. 5, and therefore, the description thereof is omitted.

After switching m in turn_maxIn the conversion imaging in which imaging is performed by illumination, at least one of the imaging unit and the image data can be calibrated by using calibration data (black point correction data, accumulation time, gain) corresponding to each illumination condition, and calibrated image data can be obtained.

According to the above imaging method, it is possible to simultaneously correct the sensitivity unevenness of each pixel of the imaging unit 1 such as a line sensor and the illumination unevenness due to the difference in illumination conditions.

(embodiment mode 4)

Fig. 7 is a block diagram showing the structure of an inspection apparatus 40a according to embodiment 4. This inspection apparatus 40a differs from the inspection apparatus 40 according to embodiment 3 in that the storage means 2 and the calibration means 3 are provided not in the control device 20 but in the imaging device 10 c. Specifically, the imaging device 10c includes: a storage unit 2 that stores

calibration data

2a, 2b, 2c, 2d corresponding to each illumination condition for calibrating at least one of the image pickup unit 1 and the image data, and a calibration unit 3 that calibrates at least one of the image pickup unit 1 and the image data using the calibration data.

In this manner, the imaging device 10c includes: since the storage means 2 and the calibration means 3 have the

calibration data

2a, 2b, 2c, and 2d corresponding to each illumination condition, the calibration can be performed in the state of high-precision image data (high-gradation image signal) inside the imaging device 10c without being affected by the low-gradation processing at the time of external output, as compared with the case of performing processing by outputting to the outside, and highly-precise calibrated image data can be obtained.

In the subsequent external output, the calibrated image data is subjected to the low gradation processing, but compared with the case where the calibration is performed after the low gradation processing, the influence of the low gradation processing, for example, a large reduction in the number of bits, is not received, and therefore the influence of the accuracy reduction can be suppressed.

(embodiment 5)

< inspection apparatus >

Fig. 8 is a block diagram showing the structure of an inspection apparatus 40b according to embodiment 5. This inspection apparatus 40b differs from the inspection apparatus 40a of embodiment 4 in the following points: the imaging device 10d constituting the inspection device 40b includes: a storage unit 12 that stores black

point correction data

12a, 12b, 12c, 12d, 12e for performing black point correction on the image data, and a black point correction unit 13 that performs black point correction on the image data using the black

point correction data

12a, 12b, 12c, 12d, 12 e. Further, the illumination differs in that illumination L5 (18 e) that is transmitted light is also provided. The other structures are substantially the same as those of the inspection apparatus according to embodiment 4.

In the inspection device 40b, since the image data can be corrected for black dots by the black dot correction data corresponding to the illumination condition at the time of image capturing, appropriate correction according to the illumination condition can be performed. The imaging device 10d constituting the inspection device 40b includes, in its interior: a memory unit 12 having black

dot correction data

12a, 12b, 12c, 12d, 12e, and a black dot correction unit 13. Therefore, compared to the case where the image data is output to the outside and processed, the shading correction can be performed in the state of high-precision image data (high-gradation image signal) inside the imaging device 10d without being affected by the low-gradation processing at the time of the external output, and highly-precise corrected image data can be obtained.

Hereinafter, each component constituting the inspection apparatus 40b will be described.

< imaging apparatus >

The components of the imaging device 10d constituting the inspection device 40b will be described.

< imaging means >

As the imaging unit 11, substantially the same units as the imaging unit 1 in

embodiments

3 and 4 can be used. Therefore, detailed description is omitted.

< storage cell >

The memory cell 12 has a plurality of black

dot correction data

12a, 12b, 12c, 12d, 12 e. Each of the black

point correction data

12a, 12b, 12c, 12d, and 12e is composed of a white reference and a black reference for each pixel of the image pickup element 11a of the image pickup unit 11 for each lighting condition. For example, fig. 4 is a graph showing a white reference W and a black reference B of each pixel constituting the black point correction data. In fig. 4, the horizontal axis represents pixel position and the vertical axis represents luminance.

The first black point correction data 12a, the second black point correction data 12b, the third black point correction data 12c, the fourth black point correction data 12d, and the fifth black point correction data 12e correspond to illumination conditions by illumination L1 (18 a), illumination L2 (18 b), illumination L3 (18 c), illumination L4 (18 d), and illumination L5 (18 e), respectively. The number of illuminations and the number of black point correction data need not necessarily match, and a plurality of black point correction data corresponding to combinations of various illumination conditions may be stored as many as necessary and appropriate black point correction data may be used in accordance with switching of the illumination conditions.

illuminations

18a, 18B, 18c, 18d, and 18 e.

< Black Point correction Unit >

The black dot correction unit 13 corresponds to the calibration unit 3 in

embodiments

3 and 4. The shading correction unit 13 performs shading correction on the image data using the shading correction data. The shading correction unit 13 may be realized by a physical structure using a circuit, for example. Alternatively, the present invention may be implemented by computer software operating on a computer. The computer may have a function that requires the minimum necessary to be able to execute the above-described correction operation among a CPU, a ROM, a RAM, a hard disk, an input/output interface, and the like, which are general constituent elements.

point correction data

12a, 12b, 12c, 12d, and 12e from the storage unit 12 every time the lighting is switched, and thus higher-speed correction processing can be performed.

A schematic diagram illustrating the operation of the shading correction unit 13 of the imaging device 10d constituting the inspection device 40b of fig. 8 is the same as that of fig. 3. Note that a graph showing the white reference and the black reference of each pixel constituting the black point correction data in the inspection device 40b, the image signal before correction, and the image signal after correction is the same as that in fig. 4. Therefore, the description of the shading correction by the shading correction unit 13 is also the same as that described above, and therefore, the description thereof is omitted.

< output Unit >

As the output means 14, substantially the same means as the output means 4 in

embodiments

3 and 4 can be used. Therefore, detailed description is omitted.

< buffer memory >

As the buffer memory, substantially the same memory as that in embodiment 3 can be used. Therefore, detailed description is omitted.

< illumination >

In the inspection apparatus 40b, illumination L5 (18 e) for transmitted light is also provided. By using the illumination L5 (18 e) that is transmitted light, for example, an effect of easily detecting foreign matter on a transparent object to be inspected can be obtained.

< synchronization Signal Generation Unit >

As the synchronization signal generation unit 16, substantially the same units as the synchronization signal generation unit 16 in

embodiments

3 and 4 can be used. Therefore, detailed description is omitted.

< illumination control Unit >

As the lighting control unit 17, substantially the same unit as the lighting control unit 17 in

embodiments

3 and 4 can be used. Therefore, detailed description is omitted.

< conveying Unit >

As the conveying unit 19, substantially the same units as the conveying unit 19 in

embodiments

3 and 4 can be used. Therefore, detailed description is omitted.

In the present disclosure, any of the above-described various embodiments may be appropriately combined to provide the effects of the respective embodiments.

Industrial applicability

According to the imaging apparatus and the inspection apparatus of the present invention, at least one of the imaging unit and the image data can be calibrated by using the calibration data corresponding to the imaging condition (for example, the illumination condition), and therefore, an appropriate calibration corresponding to the imaging condition (the illumination condition) can be performed.

Description of reference numerals

1. 11 image pickup unit

1a, 11a imaging element

1b, 11b image pickup control unit

2. 12 memory cell

2a first calibration data

2b second calibration data

2c third calibration data

2d fourth calibration data

3 calibration unit

4. 14 output unit

5 object to be imaged and inspected object

10. 10a, 10b, 10c, 10d imaging device

12a first shading correction data

12b second Black Point correction data

12c third Black Point correction data

12d fourth Black Point correction data

13 black dot correction unit

15 lens

16 synchronous signal generating unit

17 Lighting control Unit

18a, 18b, 18c, 18d illumination

19 transport unit

20. 20a, 20b control device

22a, 22b, 22c line memories

25 inspection unit

30 camera system with illumination

40. 40a, 40b inspect the device.

Claims

1. An imaging device, comprising, in an interior of the imaging device:

an imaging unit that obtains image data of an object to be imaged illuminated by an illumination unit that can switch between a plurality of different illumination conditions to illuminate the object to be imaged;

a storage unit having a plurality of calibration data for calibrating the image data in advance in correspondence with the plurality of illumination conditions;

a calibration unit configured to perform calibration of the image data by switching the plurality of calibration data in accordance with switching of illumination conditions during imaging; and

an output unit for outputting the image signal of the calibrated image data to the outside of the imaging device with reduced accuracy by reducing the transmission rate of the image signal in response to the external output,

the calibration means performs calibration in a state in which the image data is not affected by the low gradation processing performed by the output means.

2. The image pickup apparatus according to claim 1,

the calibration data is black dot correction data for performing black dot correction on the image data,

the calibration unit is a black dot correction unit that performs black dot correction using the black dot correction data.

3. The image pickup apparatus according to claim 1,

the calibration data is calibration data relating to accumulation time of an image pickup element in the image pickup unit,

the calibration means adjusts the accumulation time of the image pickup device in the image pickup means using calibration data relating to the accumulation time.

4. The image pickup apparatus according to claim 1,

the calibration data is calibration data relating to gain in the camera unit,

the calibration means adjusts the gain in the imaging means using calibration data relating to the gain.

5. The image pickup apparatus according to any one of claims 1 to 4,

the calibration data is calibration data for performing calibration in accordance with an illumination condition at the time of imaging,

the calibration unit performs calibration by switching from the plurality of calibration data to calibration data corresponding to the illumination condition at the time of imaging, in accordance with the switching of the illumination condition at the time of imaging.

6. The imaging apparatus according to claim 5, wherein the calibration means switches to calibration data corresponding to the illumination condition at the time of imaging in synchronization with switching of the illumination condition at the time of imaging.

7. The image pickup apparatus according to claim 1, wherein the calibration unit switches the calibration data in synchronization with image pickup in the image pickup unit.

8. An inspection apparatus comprising the imaging apparatus according to any one of claims 1 to 4.

9. An inspection apparatus, comprising:

an illumination unit capable of illuminating the object to be inspected by switching between a plurality of different illumination conditions;

an imaging unit that obtains image data of the object illuminated by the illumination unit;

a storage unit that stores a plurality of calibration data for calibrating at least one of the image capturing unit and the image data in correspondence with the plurality of lighting conditions;

a calibration unit configured to perform calibration of at least one of the imaging unit and the image data by switching the plurality of calibration data in accordance with switching of illumination conditions during imaging; and

and an inspection unit configured to perform defect inspection of the inspection object by combining the plurality of calibrated image data.

10. The inspection apparatus according to claim 9, wherein the illumination unit includes a plurality of illumination devices that illuminate under different illumination conditions.

11. The inspection apparatus according to claim 9 or 10,

12. The inspection apparatus according to claim 9 or 10,

13. The inspection apparatus according to claim 9 or 10,

the calibration data is calibration data relating to gain in the camera unit,

14. The inspection apparatus according to claim 9 or 10, wherein the calibration unit switches to calibration data corresponding to the illumination condition at the time of imaging in synchronization with switching of the illumination condition at the time of imaging.

15. The inspection apparatus according to claim 9 or 10, wherein the calibration unit switches the calibration data in synchronization with imaging in the imaging unit.