JP2017199998A - Scanner and production method for scanning image - Google Patents

Abstract

A high-quality scan is performed even in a strong external light state.
A determination unit that performs external light measurement for measuring the intensity of external light reaching a sensor in a state where a light source is turned off and determines whether or not the measurement result exceeds a threshold value, and the result of the external light measurement is If the threshold is not exceeded, the latest result in the shading result, which is the result of the shading measurement, is used as the shading result used in the next scan, and the external light measurement result exceeds the threshold. The shading result when the past external light measurement result does not exceed the threshold is used as the shading result to be used in the next scan, and when the scan instruction is received, the external light measurement is performed. And a control unit configured to perform scanning after the shading result used in the next scan is determined.
[Selection] Figure 3

Description

  The present invention relates to a scanner and a scan image production method.

  The scanner illuminates the scan target with a light source, and detects a light from the scan target with a sensor to produce a scan image obtained by reading the scan target. Since variations and temporal changes occur in the characteristics of sensors and light sources, shading measurement is generally performed, and a scanned image is produced based on the measured shading result. When performing shading measurement, if light other than light from the light source, that is, external light is incident on the sensor, the shading result is affected. Therefore, a technique for reducing the influence of external light has been developed. For example, Patent Document 1 discloses a technique for acquiring a white level and a black level while reading a document to the rear end and then the document reaches a paper discharge position.

JP 2013-150175 A

  In the conventional technique, after the original is read to the rear end, the white level and the black level are acquired while the original reaches the paper discharge position. However, even if the original reaches the paper discharge position after the original is read to the rear end, the external light is not necessarily completely eliminated. In particular, when the intensity of outside light is very strong, the white level and black level are affected by outside light, and the white level and black level cannot be measured properly.

  An object of the present invention is to perform high-quality scanning even in a strong external light state.

  The scanner for achieving the above object includes an external light measurement that measures the intensity of external light reaching the sensor with the light source turned off, a determination unit that determines whether the measurement result exceeds a threshold, and an external If the light measurement result does not exceed the threshold value, the latest result in the shading result, which is the result of the shading measurement, is used as the shading result used in the next scan, and the external light measurement result exceeds the threshold value. If the result of the past external light measurement does not exceed the threshold value, the shading result is used as the shading result to be used in the next scan. A control unit that performs scanning after a shading result used in scanning is determined.

  That is, the determination unit determines whether or not the external light intensity is high enough to allow the shading measurement to be properly performed by comparing the external light measurement result with a threshold value. If the external light intensity exceeds the threshold and is excessively strong, the shading result measured in the past and the external light intensity not exceeding the threshold is used. To do. When the intensity of outside light does not exceed the threshold and is in an appropriate range, the latest shading result is used.

  In this configuration, when the intensity of outside light exceeds the threshold value, the past shading result is used, and therefore the shading result does not reflect the intensity of outside light. However, in general, in a scanner, a scan target exists in an optical path that reaches the sensor from the light source in a state where the scan target is being read. Therefore, most of the outside light is shielded by the scan target, and even if the intensity of the outside light is excessive, most of the outside light does not reach the sensor.

  For this reason, when a shading result appropriately measured in the past is used, scanning can be performed more accurately than when a shading result measured under the influence of excessive intensity of external light is used. Therefore, if the intensity of the external light is excessive, scanning using the shading result measured in the past properly will use the shading result measured under the influence of external light. Higher quality scans can be performed than

It is a block diagram of a scanner. It is a figure which shows the structure of the periphery of the conveyance mechanism of a scanner. It is a figure which shows the specific example of a shading measurement. It is a flowchart of a scanning process. It is a flowchart of the scanning process concerning other embodiment.

Here, embodiments of the present invention will be described in the following order.
(1) Scanner configuration:
(1-1) Shading measurement:
(2) Scan processing:
(3) Other embodiments:

(1) Scanner configuration:
FIG. 1 is a block diagram of a scanner 1 according to an embodiment of the present invention. The scanner 1 includes a controller 10, a sensor 20, an illumination unit 30, a transport mechanism 40, an operation unit 50, and a communication unit 60. The controller 10 includes a recording medium (not shown) and a processor that reads and executes a program from the recording medium (may be a dedicated circuit such as an ASIC in which a circuit is configured to execute a specific process).

  The controller 10 controls each unit (the sensor 20, the illumination unit 30, the transport mechanism 40, and the operation unit 50) included in the scanner 1, and produces a scanned image obtained by reading a document that is a scan target. The scanned image may be used in various forms, and may be stored in a recording medium (not shown) included in the scanner 1, may be stored in a portable recording medium, or may be stored in another manner via the communication unit 60. It may be provided to the device. In the present embodiment, the scanned image is output to the computer 70 via the communication unit 60.

  The sensor 20 is a line sensor extending in the main scanning direction, and can read a document placed on a document table. The sensor 20 includes a plurality of light receiving elements that output signals corresponding to the intensity of received light, and the light receiving elements are arranged in the main scanning direction to form a line sensor. In the present embodiment, the main scanning direction is a direction perpendicular to the sub-scanning direction in which the document is conveyed.

  The illumination unit 30 includes a light source 30a that irradiates illumination light to a reading region provided in a document transport path. Light reflected by an object (such as an original or a white reference plate) existing in the reading area is received by the sensor 20, and the sensor 20 generates a signal corresponding to the amount of light received by each light receiving element.

  The sensor 20 includes an AFE (analog front end) 20a. The AFE 20a includes a circuit that outputs a signal by applying a gain to a signal output from the light receiving element in accordance with the amount of received light, and a circuit that performs A / D conversion. In this embodiment, the AFE 20a includes a recording medium that records information indicating the gain. In the AFE 20a, the black level of the sensor 20 is set to the minimum output value and the white level is set to the maximum based on the information indicating the gain. Adjust the gain to the output value. Note that an initial value of information indicating a gain determined based on an initial characteristic of the sensor 20 is recorded on the recording medium. The gain adjustment may be performed for each light receiving element included in the sensor 20, may be performed for each chip provided with a plurality of light receiving elements, or may be performed for the entire sensor 20.

  The transport mechanism 40 is a mechanism for transporting a document. The transport mechanism 40 is a mechanism for transporting a document from the outside of the reading region to the reading region, and further transporting the document from the reading region to the outside of the reading region. Scanned images are produced by the reading by 20.

  FIG. 2 is a diagram illustrating a configuration example of the transport mechanism 40. The transport mechanism 40 shown in FIG. 2 includes a cover 41 and a document table 42. The cover 41 and the document table 42 are provided with a pair of transport rollers 41a and 42a, and the document P can be transported in the transport direction by sandwiching the document P between the pair of transport rollers 41a and 42a. Inside the document table 42, a sensor 20 and a light source 30a are arranged. A glass 42 b is disposed on the upper surface of the document table 42, and a white reference plate 41 b is disposed on the lower surface of the cover 41. An area between the glass 42b and the white reference plate 41b is a reading area of the original P.

  The operation unit 50 includes an output unit that provides various information to the user and an input unit that receives an input operation by the user. The controller 10 causes the output unit to display information for performing scanning condition options, a scan instruction, and the like by the function of the control unit 13. The user can input scan condition selection, a scan instruction, and the like based on the output of the output unit.

  The communication unit 60 is a device for communicating with an external device (in this embodiment, an external computer 70), and the controller 10 transmits arbitrary information to the computer 70 and receives various instructions from the computer 70. Etc. can receive. In the present embodiment, when the controller 10 produces a scan image, the scan image is transmitted to the computer 70 via the communication unit 60.

(1-1) Shading measurement:
The AFE 20a of the sensor 20 sets the detection intensity of the sensor 20 when the light source 30a is turned off to the black level, and the detection intensity of the sensor 20 when the light source 30a is turned on (the intensity of light reflected from the white reference plate 41b). Considering the white level, the gain adjustment is performed so that the black level is the minimum output value and the white level is the maximum output value. That is, the black level and the white level correspond to the detectable range of the sensor, and the AFE 20a performs gain adjustment so that the detectable range of the sensor becomes the minimum value to the maximum value of the digital output.

  The black level and white level can vary depending on the characteristics of the sensor 20. For example, the characteristics of the sensor 20 may fluctuate due to noise such as dark current, manufacturing errors for each sensor, changes with time, etc., and the black level and white level may fluctuate in accordance with this fluctuation. Therefore, in the present embodiment, the controller 10 adjusts the gain in a state reflecting such characteristic variation and executes a high-quality scan, so that the black level and the white level are set each time a scan instruction is issued. Perform the shading measurement to be measured.

  However, since the result of the shading measurement is affected by the external light of the scanner 1, if the intensity of the external light is excessive, the quality of the scan is deteriorated if the shading result is used for gain adjustment. Specifically, in the scanner 1 according to the present embodiment, the reading area is sandwiched between the cover 41 and the document table 42, but there is a space for conveying the document P between the cover 41 and the document table 42. The external light E can enter the reading area from the outside.

  In this embodiment, since the shading measurement is performed in a state where the document P does not exist in the reading area, the external light E shown in FIG. 2 excessively enters the reading area, and the external light is detected by the sensor 20. It can happen. On the other hand, when scanning is performed, the document P is in a state indicated by a broken line in FIG. 2 where the document P is sandwiched between the transport rollers 41a and 42a existing in the front and rear in the transport direction. Therefore, even when the external light E is excessively strong, most of the external light is blocked by the document P during scanning, and scanning is performed based on the shading result measured in a state where the external light E is excessively strong. Scan quality is degraded.

  Therefore, in this embodiment, the controller 10 can execute the functions of the determination unit 11, the shading unit 12, and the control unit 13 by a program (not shown) in order to execute a high-quality scan even when the outside light is strong. It is. When the user gives a scan instruction using the operation unit 50, the control unit 13 controls the sensor 20, the illumination unit 30, and the conveyance mechanism 40, while conveying the document P, the document existing in the reading area from the light source 30 a of the illumination unit Is irradiated with light to cause the sensor 20 to perform reading.

  However, in this embodiment, in order to execute a high-quality scan even when the outside light is strong, the control unit 13 causes the outside light measurement to be performed when the scan instruction is received, and is used for the next scan. After the result is determined, the next scan is performed. Specifically, before starting scanning, the control unit 13 instructs the shading unit 12 to perform shading measurement, instructs the determination unit 11 to perform determination, and then causes the shading unit 12 to perform shading. Let the result be determined.

  The shading unit 12 performs shading measurement before determining a shading result to be used in the next scan. In the present embodiment, the shading measurement includes black shading measurement for measuring the black level and white shading measurement for measuring the white level. Specifically, the controller 10 controls the illumination unit 30 to turn off the light source 30a and controls the transport mechanism 40 so that the document P does not exist in the reading area. Then, the controller 10 specifies a signal output from the sensor 20 in a state where the light source 30a is turned off and the document P does not exist in the reading area. The signal is a signal before gain adjustment is performed, and the controller 10 regards the signal as a black level. Furthermore, the controller 10 controls the illumination unit 30 to turn on the light source 30a. Then, the controller 10 specifies a signal output from the sensor 20 in a state where the light source 30a is turned on and the document P does not exist in the reading area. The signal is a signal before gain adjustment is performed, and the controller 10 regards the signal as a white level.

A signal indicating the black level and the white level, that is, the shading result is used for gain adjustment. FIG. 3 shows the black level and white level in the shading measurement performed at different timings (T ₁ , T ₂ , T ₃ , T ₄₁ (or T ₁ , T ₂ , T ₃ , T ₄₂ )) arranged in time series. An example is shown. In FIG. 3, the vertical axis represents the output value of the sensor 20, and here, the output value (or light amount) before gain adjustment is schematically shown. Here, the minimum value of the output value of the sensor 20 is min, and the maximum value is max. In the bar graph shown in FIG. 3, K is added to the portion corresponding to the output value of the black level, and the light quantity resulting from the lighting of the light source is schematically indicated by L. Therefore, for example, at timing T ₁ , the left bar graph schematically shows black shading measurement for measuring the black level, and the right bar graph schematically shows white shading measurement for measuring the white level.

At the timing T ₁ , the black level is B ₁ and is larger than the minimum value min of the output value of the sensor 20. Accordingly, in the gain adjustment, correction is performed so that the black level B ₁ is the minimum value min. At the timing T ₁ , the white level is W ₁ and is smaller than the maximum value max of the output value of the sensor 20. Therefore, in the gain adjustment, correction is performed so that the white level W ₁ is the maximum value max. That is, when the black level B ₁ and the white level W ₁ are obtained as a shading result, the controller 10 records the black level B ₁ and the white level W ₁ on the recording medium of the AFE 20a. As a result, in the AFE20a, it performs gain adjustment for the black level B ₁ the minimum value of the output value of the sensor 20, the maximum value of the output value of the white level W ₁ sensor 20.

When the black level B ₂ and the white level W ₂ are obtained as shading results by the shading measurement at the timing T ₂ , the controller 10 records the black level B ₂ and the white level W ₂ on the recording medium of the AFE 20a. As a result, in the AFE20a, it performs gain adjustment for the black level B ₂ minimum value of the output value of the sensor 20, the maximum value of the output value of the white level W ₂ sensor 20.

At the timing T ₃ , the black level B ₃ is obtained by the black shading measurement, but since the maximum value max of the output value of the sensor 20 is obtained by the white shading measurement (the amount of light is saturated), the controller 10 uses the AFE 20a. the black level B ₃ and white levels max is recorded on the recording medium. As a result, in the AFE20a, the black level B ₃ and the minimum value of the output value of the sensor 20, adjusts the gain so as not to change the white level max.

As shown in the above example, the shading results obtained by the shading measurements performed at different timings may be different. That is, the shading result can change with time reflecting the change in characteristics due to the change of the sensor 20 over time. For example, when comparing the timings T ₁ , T ₂ , and T ₃ arranged in time series, the black level increases with the passage of time. As described above, since the characteristics of the sensor 20 may include a change with time, the latest shading result (scan) is necessary to perform gain adjustment using the shading result with high accuracy and produce a high-quality scan image. It is preferable that a scanned image is produced using a shading result measured at a timing closest to the timing.

  However, if the intensity of the external light is excessive, it is more likely that a higher quality scan can be performed by using the past shading results where the external light intensity was not excessive, rather than the latest shading results. . Specifically, when the intensity of external light is excessive, the amount of external light that reaches the sensor 20 during shading measurement and the external light that reaches the sensor 20 while being blocked by the original P during scanning. Since the amount of light is significantly different, a scanned image cannot be produced with high quality using the latest shading results.

In FIG. 3, an example in which the shading measurement is performed at a timing later than timing T ₃ , when the intensity of external light is not excessive (timing T ₄₁ ) and the intensity of external light is excessive. The case (timing T ₄₂ ) is shown. In each example, a bar graph of the amount of light at the stage where the shading measurement is performed is shown on the left side, and then the bar graph in a state where the document P is conveyed to the reading area (external light is blocked by the document P). Is shown on the right side. As will be described later, since the time for accumulating light in the sensor 20 differs between the shading measurement and the scan, the bar graph shown in FIG. 3 schematically shows the amount of light per unit time.

At timing T ₄₁ , even if black light shading measurement is performed with external light reaching the sensor 20 during black shading measurement and the light source 30 a is turned off, the bar graph (G ₁ ) on the left side shows. As described above, the black level B ₄₁ is obtained in a state where the amount of external light Lo is added. In the white shading measurement, since the light amount is saturated, the maximum value max of the output value of the sensor 20 is obtained. When the original P is conveyed to the reading area in the situation where the external light of the light amount Lo reaches the sensor 20 in this way, the amount of external light reaching the sensor 20 by being blocked by the original P is reduced. At a timing T ₄₁ in FIG. 3, the right side of the bar (G _2), amount of external light reaching the sensor 20 is reduced, indicating that a quantity of light L _1.

The timing T ₄₁ is an example when the amount of external light Lo reaching the sensor 20 is not excessive. That is, at the timing T ₄₁ , the black level B ₄₁ is obtained by the shading measurement, but the black level B ₄₁ is not _{significantly} different from the black level B ₄₁₁ when the original P is shielded from light. In this case, it is possible to scan without shading results in the timing T ₄₁ to lower the quality of the excessive scan image be used in the next scan.

On the other hand, at the timing T _42, the external light excessive amount Lo ₂ when the black shading measured as shown in the left bar graph (G ₁₎ has reached the sensor 20, the black shading measurement is made excessively large black level B ₄₂ is obtained in a state where a light amount Lo ₂ is plus. In the white shading measurement, since the light amount is saturated, the maximum value max of the output value of the sensor 20 is obtained. Thus, when the original P is conveyed to the reading area in a situation where the external light of the light quantity Lo reaches the sensor 20, it is shielded by the original P, and the light quantity L ₂ is applied to the sensor 20 as shown in the right bar graph (G ₂ ). Outside light reaches. Therefore, the black level in a state where such light shielding is performed becomes the black level B ₄₂₂ .

Thus, at the timing T ₄₂ , the difference between the black level B ₄₂ measured by the black shading measurement and the black level B ₄₂₂ in the state where the light is shielded is extremely large. In this case, if the shading result (black level B ₄₂ ) at the timing T ₄₂ is used in the next scan, the quality of the scanned image is excessively degraded.

  Therefore, in this embodiment, the controller 10 determines whether or not the intensity of external light is excessive by the function of the determination unit 11. In other words, the determination unit 11 causes the controller 10 to perform a function of performing external light measurement for measuring the intensity of external light reaching the sensor 20 with the light source turned off, and determining whether the measurement result exceeds the threshold value. . In the present embodiment, the result of black shading measurement is used as the result of external light measurement. Therefore, in the present embodiment, the controller 10 considers that the measurement result of the external light measurement is acquired by acquiring the result of the black shading measurement from the result of the shading measurement by the shading unit 12 by the function of the determination unit 11. . According to this configuration, external light measurement and black shading measurement can be performed simultaneously.

  Then, the controller 10 determines whether or not the result of the external light measurement exceeds the threshold value by comparing the result of the black shading measurement and the threshold value by the function of the determination unit 11. Here, the threshold value can be determined whether or not the scan image has an inappropriate result when the intensity of the external light is excessive and the scan image is produced based on the shading result obtained in the external light state. Is set as follows. In the present embodiment, the shading measurement is performed while changing the intensity of the external light, and the threshold of the external light is specified such that the quality of the scanned image reflecting the shading result is outside the allowable range. Is determined in advance. In the present embodiment, a threshold value is defined in advance so as to be compared with the black level. In FIG. 3, an example of the threshold value is indicated as Th.

  When the controller 10 specifies the shading result to be used in the next scan by the function of the shading unit 12, the controller 10 determines different shading results depending on whether the external light measurement result exceeds the threshold value or not. The controller 10 is caused to function so as to obtain a shading result used in scanning. That is, the controller 10 compares the result of external light measurement with the threshold value by the determination unit 11 to determine whether or not the influence of the external light is large enough to exceed the advantage that the characteristic variation due to the temporal change of the sensor 20 is eliminated. Identify.

Specifically, in the example shown in FIG. 3, when scanning is performed at timing T ₄₂ , the black level becomes B ₄₂₂ as a result of being shielded from light by the original P. When the black level B ₄₂ measured by the black shading measurement at the timing T ₄₂ is compared with the black level B ₃ measured by the black shading measurement at the timing T ₃ , the difference between the black level B ₄₂ and the black level B ₄₂₂ is ΔB ₄ , and the difference between the black level B ₃ and the black level B ₄₂₂ is ΔB ₃ . Therefore, the black level B ₃ measured by the black shading measurement at the timing T ₃ is the black level B ₄₂₂ at the time of the actual scanning, rather than the black level B ₄₂ measured by the black shading measurement at the timing T ₄₂ . close.

Therefore, when the external light is strong as indicated by the timing _T42, it can be said that the influence of the external light is large enough to exceed the advantage of eliminating the characteristic variation due to the change of the sensor 20 with time. Therefore, in such a case, the controller 10 uses the function of the shading unit 12 to determine the past shading obtained in a state where the external light measurement result did not exceed the threshold value, not the latest shading result (black level B ₄₂₂ ). Let the shading result be the shading result used in the next scan.

  When the external light measurement result exceeds the threshold, the controller 10 uses the function of the shading unit 12 to display the latest result among the shading results when the past external light measurement result does not exceed the threshold. The shading result used in the next scan is used. That is, since the shading result reflects the fluctuation of the characteristics due to the change of the sensor 20 with time, the latest shading result may most accurately indicate the change of the sensor 20 with time among the past shading results. high.

For example, in the example illustrated in FIG. 3, it is assumed that shading measurement is performed in the order of timings T ₁ , T ₂ , T ₃ in the past, and the latest shading measurement is performed at timing T ₄₂ . In this example, since the result of the external light measurement does not exceed the threshold value at the timings T ₁ , T ₂ , and T ₃ , the controller 10 uses the function of the shading unit 12 to cause the shading result at the latest timing T ₃ among them. Is the shading result used in the next scan.

That is, in the step of timing T _42, information indicating the shading results in the latest timing T ₃ in which the result of outside light measurement does not exceed the threshold value is recorded in a recording medium AFE20a. Therefore, the controller 10 does not update the recording medium AFE20a shading result at the timing T _42. As a result, the AFE 20a performs gain adjustment based on the information recorded on the recording medium. That is, in the AFE20a, the black level B ₃ and the minimum value of the output value of the sensor 20, adjusts the gain so as not to change the white level max. According to this configuration, it is possible to use a shading result that is most likely to show the change with time of the sensor 20 most accurately among past shading results, and to perform high-quality scanning.

On the other hand, when the result of the external light measurement does not exceed the threshold value, the controller 10 uses the function of the shading unit 12 to set the latest shading result as a shading result used in the next scan. For example, in the example shown in FIG. 3, when the shading measurement at the timing T ₄₁ is performed, the controller 10 records the shading results obtained at the timing T ₄₁ to a recording medium AFE20a. That is, the black level B ₄₁ and the white level max obtained at the timing T ₄₁ are recorded on the recording medium of the AFE 20 a. As a result, in the AFE 20a, the black level B ₄₁ is set to the minimum value of the output value of the sensor 20, and gain adjustment is performed so as not to change the white level max.

  In the present embodiment, the controller 10 performs external light measurement (shading measurement) by accumulating light longer than the accumulation time of light when the document P is scanned by the sensor 20. That is, since the scan period when the original P is scanned is generally a very short period, the intensity of the external light is measured at the same time as the sensor 20 accumulates light during the scan. Often difficult. Therefore, in the present embodiment, when the controller 10 performs external light measurement (shading measurement), the time during which the sensor 20 accumulates light is longer than the time during which the sensor 20 accumulates light during scanning of the document P. . According to this configuration, external light measurement can be performed more reliably.

  Upon receiving the scan instruction, the control unit 13 controls the sensor 20, the illuminating unit 30, and the transport mechanism 40 to perform scanning after the shading result used in the next scan is determined as described above. To produce. When the scan image is produced, the controller 10 outputs the scan image to the computer 70 via the communication unit 60. As a result, the computer 70 can use the scanned image. In the present embodiment as described above, even if the intensity of the external light exceeds the threshold value, scanning is performed using a shading result appropriately measured in the past, so the influence of external light is reduced. Higher quality scanning can be performed than when scanning is performed using the shading result measured in the received state.

(2) Scan processing:
Next, the procedure of the scanning process will be described along the flowchart shown in FIG. When the user gives a scan instruction using the operation unit 50, the controller 10 receives the scan instruction by the function of the control unit 13, and starts the scan process shown in FIG. When the scanning process is started, the controller 10 performs shading measurement by the function of the shading unit 12 (step S100). That is, when the document P exists in the reading area, the controller 10 instructs the transport mechanism 40 to discharge the document P.

  In addition, the controller 10 instructs the sensor 20 to perform scanning at a cycle longer than that of the original P. Further, the controller 10 instructs the illumination unit 30 to turn off the light source 30a, acquires the detection intensity of the sensor 20 in a state where the light source 30a is turned off, and measures the black level. Further, the controller 10 instructs the illumination unit 30 to turn on the light source 30a, acquires the detection intensity of the sensor 20 in a state where the light source 30a is turned on, and measures the white level. When the black level and the white level are measured, the control unit 13 temporarily records the measurement result in a memory (not shown).

  Next, the controller 10 determines whether or not the intensity of external light is larger than the threshold value by the function of the determination unit 11 (step S105). That is, the controller 10 obtains a black level temporarily recorded in a memory (not shown) in step S100 by the function of the determination unit 11, and the intensity of external light is larger than the threshold when the black level is larger than the threshold. Is determined.

  When it is determined in step S105 that the intensity of external light is greater than the threshold, the controller 10 uses the shading result recorded on the recording medium of the AFE 20a for the next scan by the function of the shading unit 12 (step S110). ). That is, the controller 10 does not update the information indicating the gain (information indicating the black level and the white level) recorded on the recording medium of the AFE 20a, and sets the controller 10 to be used in the next scan.

  On the other hand, if it is not determined in step S105 that the intensity of outside light is greater than the threshold, the controller 10 uses the shading result measured in step S100 for the next scan by the function of the shading unit 12 (step S115). ). That is, the controller 10 updates the information indicating the gain recorded on the recording medium of the AFE 20a with the shading result measured in step S100. As a result, in the AFE 20a, the shading result measured in step S100 is used in the next scan.

  Next, the controller 10 performs a scan by the function of the control unit 13 (step S120). That is, the controller 10 instructs the transport mechanism 40 to transport the document P to the reading area. Further, the controller 10 instructs the illumination unit 30 to turn on the light source 30a, obtains the output of the sensor 20 in synchronization with a predetermined period as the scanning period of the document P, and the document P by the transport mechanism 40. Repeat transportation. When information about a predetermined area of the document P is output from the sensor 20, the controller 10 records the output information in the memory as scan image information. As a result, a scanned image can be produced without degrading the quality even when the intensity of external light is excessively strong.

(3) Other embodiments:
The above embodiment is an example for carrying out the present invention, and various other embodiments can be adopted. For example, various adjustments other than gain adjustment may be employed for output adjustment in the AFE 20a, and γ correction or the like may be performed. The above-described scanner 1 includes the transport mechanism 40, but may of course be a flatbed scanner in which the sensor 20, the illumination unit 30, and the like move. Furthermore, the scanner may be an apparatus integrated with another apparatus, for example, a printer. Furthermore, in the above-described example, the change over time in the shading result is focused on the change over time in the characteristics of the sensor 20, but, of course, the shading result reflecting the change over time in the characteristics of the light source 30a (such as a decrease in the amount of light). The present invention may be applied to the resulting configuration.

  The determination unit only needs to be able to determine whether or not the measurement result exceeds the threshold by performing external light measurement that measures the intensity of external light reaching the sensor with the light source turned off. That is, the determination unit can control the light source that emits light to the scan target when scanning the scan target, and can turn off the light source. In addition, the external light measurement only needs to be able to measure the intensity of external light reaching the sensor with the light source turned off, and the measurement may be performed by a sensor for performing scanning, or other detection means, For example, it may be executed by an optical sensor different from the sensor for performing scanning, and various configurations can be adopted.

  The threshold to be compared with the measurement result of the external light measurement is that the intensity of the external light is excessive, and if the scan image is produced based on the shading result obtained in the external light state, the scan image is inappropriate It may be set so that it can be determined whether or not. Therefore, for example, the shading measurement is performed while changing the intensity of the external light, and the threshold value is determined by specifying in advance the intensity of the external light such that the quality of the scanned image reflecting the shading result is outside the allowable range. You just have to. Note that when measuring external light, the scan target may or may not exist at the reading position, but the scan target exists at the reading position in order to accurately determine the influence of external light. It is preferable that no scanning target exists on the optical path from the light source to the sensor.

  When the shading unit specifies a shading result to be used in the next scan, a different shading result is used as a shading result in the next scan depending on whether the external light measurement result exceeds the threshold value or not. I can do it. The shading measurement is a measurement for measuring at least the black level and white level of the sensor. That is, when the light detection intensity is the lowest among the sensor outputs, the detection intensity is regarded as the black level. When the light detection intensity is the maximum among the sensor outputs, the detection intensity is the white level. (Even if each color component is expressed as a white level).

  The black level and the white level correspond to the detectable range of the sensor, but the black level and the white level may vary depending on the characteristics of the sensor, the light source, and the like. For example, the characteristics of the sensor may fluctuate due to noise such as dark current, manufacturing errors for each sensor, changes with time, etc., and the black level and the white level may fluctuate according to this fluctuation. Therefore, in order to perform a high-quality scan, it is preferable that shading measurement is performed before the scan is performed, and the black level and the white level are specified.

  The shading measurement may be a measurement for specifying at least the black level and the white level. As a measurement of the black level, for example, a configuration in which the level output by the sensor is regarded as the black level in a state where the light source is turned off, or in addition to the state, there is no scanning target in the optical path from the light source to the sensor. Can be adopted. As the measurement of the white level, for example, a configuration in which the level output by the sensor is regarded as the white level in a state where the light source is turned on and the white reference plate is disposed in the optical path from the light source to the sensor can be adopted.

  Note that the object of shading measurement may be the entire sensor, an individual sensor, or both. That is, shading measurement may be performed to eliminate fluctuations in the characteristics of the entire sensor (also referred to as calibration), or shading measurement may be performed to eliminate differences in sensor characteristics in the line direction in the line sensor. Also good. The characteristics of the sensor in the line direction may be measured for each chip on which the sensor is mounted, or may be measured for each pixel.

  Since the shading result reflects the change in characteristics due to changes with time of the sensor or the like, a scan image is produced using the latest shading result (for example, the shading result measured at the timing closest to the scan timing). It is preferable. On the other hand, if the intensity of external light is excessive, the amount of external light that reaches the sensor during shading measurement and the amount of external light that reaches the sensor while being blocked by the scan target during scanning Since the latest shading results are used, it is not possible to produce a scanned image with high quality.

  Therefore, the shading unit determines whether or not the influence of external light is so large that it exceeds the advantage of eliminating fluctuations in characteristics due to changes over time of the sensor based on the result of comparison of the external light measurement result and the threshold value by the determination unit. Is identified. And if the influence of external light is so great that the fluctuation of characteristics due to changes over time of the sensor exceeds the advantage of eliminating, the shading unit is not the latest shading result, the external light measurement result has not exceeded the threshold value The obtained past shading result is used as a shading result used in the next scan. According to this configuration, a scan image is produced with a shading result reflecting the past sensor characteristics instead of the latest sensor characteristics. Accordingly, even when the intensity of external light is excessively strong, scanning can be performed without excessively degrading the quality.

  In order to use the past shading result, information indicating at least one of the past shading results is held in the recording medium, and can be used as a shading result used in the next scan. When the external light measurement result exceeds the threshold, the past shading result used in the next scan may be various shading results including the initial value of the shading result used first.

  As a configuration example using the past shading result, for example, when the external light measurement result exceeds the threshold value, the shading unit is included in the shading result when the past external light measurement result does not exceed the threshold value. It is possible to adopt a configuration in which the latest result is used as a shading result used in the next scan. In other words, since the shading result reflects a change in characteristics due to the change with time of the sensor, it is highly likely that the latest shading result most accurately indicates the change with time of the sensor among the past shading results.

  Therefore, if the latest shading result is selected from the shading results obtained when the external light measurement result does not exceed the threshold value and used as the shading result used in the next scan, the sensor time-lapse among the past shading results. Shading results that are most likely to show the change most accurately can be used, and high quality scans can be performed.

  The control unit only needs to be able to perform external light measurement upon receiving a scan instruction and perform scanning after the shading result used in the next scan is determined. In other words, when receiving a scanning instruction from the user, the control unit controls the scanner and produces a scanned image using a shading result used in the next scanning.

  The reflection of the shading result is based on the shading result (measured black level and white level) that the scan image is generated so that the sensor's detectable range is substantially from the black level to the white level. It is realized with. Such reflection of the shading result may be performed by various methods. For example, it may be configured to output a signal in a range from a black level to a white level by gain adjustment with respect to the output signal of the sensor, or when generating digital image data based on the output signal of the sensor, The image data may be generated so that the black level is the minimum value of the gradation value and the white level is the maximum value of the gradation value, and various configurations can be employed.

  As described above, external light measurement can also be performed by a sensor for performing scanning. In this case, a configuration may be employed in which external light measurement is performed by accumulating light in the sensor for a longer time than scanning. That is, since the scan cycle (cycle in which lighting and non-lighting of the light source for reading one pixel is set to one cycle) is generally a very short cycle, the time during which the sensor accumulates light during the scan It is often difficult to measure the intensity of external light that is equivalent. Therefore, if the time for which the sensor accumulates light in the external light measurement is longer than the time for which the sensor accumulates light in the scan to be scanned, the external light measurement can be performed more reliably.

  When external light measurement is performed using a sensor for scanning, the external light measurement may be black shading measurement. That is, when black shading measurement for measuring the black level is performed in a state where the light source is turned off, the measurement result can be regarded as an external light measurement result. In this case, the determination unit determines whether or not the result of the black shading measurement exceeds the threshold value. According to this configuration, external light measurement and black shading measurement can be performed simultaneously.

  When external light measurement is performed using an optical sensor different from the sensor for performing scanning, the scanning process may be different from the process illustrated in FIG. 4 described above. FIG. 5 is a flowchart illustrating an example of scan processing when external light measurement is performed using an optical sensor different from the sensor for performing scanning. In FIG. 5, the same processes as those in FIG. 4 are denoted by the same reference numerals. That is, in the process shown in FIG. 5, the external light measurement in step S90 and the shading measurement in step S112 are different from the process shown in FIG.

  Further, this processing is realized by providing a sensor for measuring external light separately from the sensor 20 in the scanner 1 shown in FIG. The sensor for measuring the external light only needs to be able to evaluate the external light reaching the sensor 20 and may be provided on the outer surface of the scanner 1 or may be provided near the reading region or the sensor 20. Good.

  In this configuration, in step S90, the controller 10 uses the function of the determination unit 11 to turn off the light source 30a and acquire the output of a sensor for measuring external light in a state where the document P does not exist in the reading area. Measure ambient light. In step S105, the intensity of external light is evaluated based on a preset threshold value for evaluating the intensity of external light based on the output of the sensor. Then, when the intensity of the external light does not exceed the threshold value, the controller 10 performs the shading measurement in step S112 by the function of the shading unit 12. The shading measurement is the same processing as step S100 shown in FIG. Steps S110, S115, and S120 are the same as the processing shown in FIG. According to this configuration, the shading measurement can be omitted when the shading measurement is not significant.

  Furthermore, as described above, the method of changing the shading result used in the next scan based on the intensity of external light can also be realized as a method. Furthermore, each unit included in the scanner may be realized by hardware resources, hardware resources whose functions are specified by a program, or a combination thereof, and various modes can be adopted. Furthermore, the function of each unit is not limited to that realized by hardware resources that are physically independent of each other. Furthermore, the function of each unit can be realized as a program or a recording medium for the program. Of course, the recording medium may be a magnetic recording medium, a magneto-optical recording medium, or any recording medium developed in the future.

DESCRIPTION OF SYMBOLS 1 ... Scanner, 10 ... Controller, 11 ... Judgment part, 12 ... Shading part, 13 ... Control part, 20 ... Sensor, 30 ... Illumination part, 30a ... Light source, 40 ... Conveyance mechanism, 41 ... Cover, 41a ... Conveyance roller, 41b ... white reference plate, 42 ... original table, 42a ... conveying roller, 42b ... glass

Claims (5)

A scanner,
A determination unit that performs external light measurement to measure the intensity of external light reaching the sensor with the light source turned off, and determines whether the measurement result exceeds a threshold;
When the external light measurement result does not exceed the threshold, the latest result in the shading result that is the result of the shading measurement is used as the shading result used in the next scan,
When the external light measurement result exceeds the threshold, the shading unit uses the shading result when the previous external light measurement result does not exceed the threshold as the shading result used in the next scan. When,
When receiving a scan instruction, the controller that performs the external light measurement and performs a scan after the shading result used in the next scan is determined;
With a scanner. The external light measurement is
By accumulating light in the sensor for a longer time than scanning,
The scanner according to claim 1. The shading part is
When the result of the external light measurement exceeds the threshold, the shading that uses the latest result among the shading results when the result of the external light measurement in the past does not exceed the threshold is used in the next scan. As a result,
The scanner according to claim 1 or 2. The external light measurement is black shading measurement, and the determination unit determines whether the result of the black shading measurement exceeds the threshold value.
The scanner according to claim 1. A method of producing a scanned image by a scanner,
When a scan instruction is received,
Perform external light measurement to measure the intensity of external light reaching the sensor with the light source turned off, determine whether the measurement result exceeds the threshold,
When the external light measurement result does not exceed the threshold, the latest result in the shading result that is the result of the shading measurement is used as the shading result used in the next scan,
When the external light measurement result exceeds the threshold, the shading result when the external light measurement result in the past does not exceed the threshold is used as the shading result used in the next scan,
After the shading result used in the next scan is determined, the scan is performed to generate a scan image.
Scanned image production method.

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