Image reading device

Abstract

To accurately perform temperature correction using a Peltier element in an image reading device.SOLUTION: A spectral characteristic acquisition device 10 as an example of an image reading device comprises: a color information acquisition unit 40 as a spectroscope array that divides light radiated and reflected on an object to be read 90 conveyed relatively in a predetermined direction (Y direction), and receives the rays of reflected light obtained through the division by each of some pixel arrays of a CCD image sensor 44; a temperature sensor 52 that measures a sensor temperature of the CCD image sensor 44; a temperature sensor 53 that measures an environmental temperature of the color information acquisition unit 40; a Peltier element 51 that controls the sensor temperature to be a target temperature; a correction table 61 that holds, according to the environmental temperature, a plurality of color calibration models for performing color calibration of an image read by the color information acquisition unit 40; and a control unit 54 that selects one color calibration model from the plurality of color calibration models 61A-61D on the correction table 61 according to the environmental temperature.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to an image reading device. [Background technology]

[0002] There is a technology for controlling the temperature using a Peltier element to stabilize the temperature and ensure the accuracy of the image sensor.

[0003] Patent Document 1 discloses a method for determining a target temperature for temperature control of a Peltier element and a configuration for correcting read data in order to maintain the temperature of a CCD image sensor and ensure reading accuracy. Summary of the Invention [Problem to be solved by the invention]

[0004] Previous methods using Peltier elements had the problem that changing the target temperature depending on the ambient temperature would result in a deviation from the temperature when adjusted as a color measurement system, resulting in a deterioration in correction accuracy.

[0005] An object of the present invention is to perform temperature correction using a Peltier element with high accuracy. [Means for solving the problem]

[0006] In order to solve the above-described problems, an image reading device according to one aspect of the present invention includes: a light source that irradiates light onto a reading object that is relatively transported in a predetermined direction; a spectrometer array that splits the light reflected from the reading object and receives each of the split reflected light at some pixel rows of an image sensor; a first temperature measurement unit that measures a sensor temperature of the image sensor; a second temperature measurement unit that measures an environmental temperature of the spectrometer array; a Peltier element that controls the sensor temperature to a target temperature; a correction table that holds a plurality of color calibration models for color calibration of an image read by the spectrometer array according to the environmental temperature; and a control unit that selects one color calibration model from the plurality of color calibration models in the correction table according to the environmental temperature.The color calibration model is created based on the temperature characteristics of each pixel of the image sensor. do. [Effects of the Invention]

[0007] Temperature correction using a Peltier element can be performed with high precision. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a perspective view illustrating an example of the configuration of a color measurement device 1 according to an embodiment. [Figure 2] 2 is a cross-sectional view illustrating a color information acquisition unit in FIG. 1; [Figure 3] FIG. 1 is a diagram illustrating a diffraction image in a spectral characteristic acquisition device and light reception by an image sensor. [Figure 4] Hardware configuration diagram of the control system for temperature stabilization control [Figure 5] Functional block diagram of the control system for temperature stabilization control [Figure 6] Hardware configuration diagram of control unit, Peltier control unit, and PC [Figure 7] A diagram showing an example of a sensor temperature estimation method [Figure 8] FIG. 10 shows another example of a sensor temperature estimation method. [Figure 9] Flowchart of sensor temperature stabilization control [Figure 10] A diagram showing an example of the configuration of a color calibration model [Figure 11] A diagram showing an example of setting the target temperature in a color calibration model [Figure 12] A diagram explaining the relationship between sensor temperature stabilization control and the ambient temperature around the sensor. [Figure 13] A diagram explaining sensor temperature stabilization control when the ambient temperature changes significantly. [Figure 14] Flowchart of sensor temperature stabilization control taking ambient temperature fluctuations into account [Figure 15] FIG. 10 is a diagram illustrating another example of sensor temperature stabilization control taking ambient temperature fluctuations into consideration. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments will be described with reference to the accompanying drawings. To facilitate understanding of the description, the same components in the drawings will be denoted by the same reference numerals as much as possible, and duplicated descriptions will be omitted.

[0010] In the following description, the X, Y, and Z directions are perpendicular to one another. The X and Y directions are horizontal directions, and the Z direction is vertical. The X direction is the longitudinal direction of the image sensor 44, and is the arrangement direction of multiple pixels. The Y direction is the longitudinal direction of each pixel of the image sensor 44. For convenience of explanation, the positive z direction may also be referred to as the upper side, and the negative z direction may also be referred to as the lower side.

[0011] Hereinafter, a color measurement device 1 and a spectral characteristic acquisition device 10 will be described as an example of an image reading device according to an embodiment.

[0012] <Basic configuration of colorimeter 1> The basic configurations of a color measurement device 1 and a spectral characteristic acquisition device 10 according to an embodiment will be described with reference to FIGS.

[0013] FIG. 1 is a perspective view illustrating an example of the configuration of a color measuring device 1 according to an embodiment. As shown in Figure 1, the color measurement device 1 has a reading unit 10 that acquires color information (reflection characteristics), a paper transport unit 2, a reading unit transport unit 3, a calibration reference unit 4, and a control system 100 (see Figures 4 and 5).

[0014] The reading unit 10 is composed of a line illumination light source (visible light source / UV light source) 20, a reduction imaging lens 30, and a color information acquisition section 40. In the following description, the reading unit 10 is also referred to as the "spectral characteristic acquisition device 10."

[0015] The paper transport unit 2 transports a reading object 90, such as a color chart to be measured, in a predetermined transport direction (the X direction in the example of FIG. 1). In the example of FIG. 1, the paper transport unit 2 is configured to transport the reading object 90, such as paper, by sandwiching it between two rollers.

[0016] The reading unit transport section 3 transports the reading unit 10 in a predetermined transport direction (Y direction in the example of FIG. 1). The transport direction of the reading unit 10 is, for example, a direction perpendicular to the transport direction of the object to be read 90. In the example of FIG. 1, the reading unit transport section 3 uses a transport stage configured with a ball screw, guides, etc.

[0017] Note that the transport methods of the paper transport section 2 and the reading unit transport section 3 shown in Figure 1 are just examples, and the configuration may differ from that of Figure 1 as long as the configuration allows the paper 90 and the reading unit 10 to be moved in the specified direction.

[0018] The calibration reference portion 4 is placed outside the reading range of the measurement target object 90. In the example of Fig. 1, the calibration reference portion 4 has a white reference plate 4A and a black reference plate 4B, but other references for adjustment of other colors may also be placed.

[0019] Referring to FIG. 1, a spectral characteristics acquisition device 10 (reading unit) has a line illumination light source 20 (light source), a reduction imaging lens 30, and a color information acquisition unit 40. FIG. 1 also shows an image-bearing medium 90 such as paper that is the object to be read (hereinafter referred to as object 90). In FIG. 1, the object to be read 90 is being transported in the X-axis direction at a constant speed. The spectral characteristics acquisition device 10 can simultaneously acquire spectral characteristics at multiple positions within a measurement area 90a of the object 90.

[0020] The line illumination light source 20 illuminates a measurement area 90a extending in the transport direction (X-axis direction) of the object 90 from a direction tilted at approximately 45 degrees with respect to the normal direction of the object 90. For example, a white LED (Light Emitting Diode) array having intensity over almost the entire visible light range can be used as the line illumination light source 20. Alternatively, a fluorescent lamp such as a cold cathode fluorescent lamp or a lamp light source can be used as the line illumination light source 20.

[0021] However, it is preferable that the line illumination light source 20 emits light in the wavelength range required for spectroscopy and can uniformly illuminate the entire observation area. A collimating lens may be added to collimate the light emitted from the line illumination light source 20 and irradiate the object 90 (as parallel light).

[0022] The reduction imaging lens 30 is disposed so that its optical axis coincides with the normal direction of the object 90, and has the function of forming an image of the reflected light (light beam) from the object 90 on the incident surface of the color information acquisition unit 40 at a predetermined magnification. Here, by adding an image-side telecentric characteristic to the reduction imaging lens 30, the chief ray of the light beam incident on the image surface becomes approximately parallel to the optical axis. The reduction imaging lens 30 may be composed of multiple lenses. The reduction imaging lens 30 is a representative example of the first imaging means according to the present invention.

[0023] Note that, by adding an image-side telecentric characteristic to the reduction imaging lens 30, the chief ray of the light beam incident on the image plane can be easily made approximately parallel to the optical axis, but it is not necessary to add an image-side telecentric characteristic to the reduction imaging lens 30. In that case, the same effect can be obtained by adjusting the positional relationship between each of the openings 41a, 41b, and 41c (each pinhole) of the pinhole array 41 and each of the lenses 42a, 42b, and 42c of the lens array 42, which will be described later with reference to FIG. 2, in accordance with the inclination of the chief ray at each position on the image plane.

[0024] Specifically, for example, the positions of each lens 42a, 42b, 42c of the lens array 42 are adjusted so that the chief ray of the light beam transmitted through each opening 41a, 41b, 41c (each pinhole) of the pinhole array 41 passes through the center of each corresponding lens 42a, 42b, 42c of the lens array 42.

[0025] The reason why the chief ray at each position on the image plane is made parallel to the optical axis is because the optical axis of each spectroscopic optical system of the downstream color information acquisition unit 40 is configured to be parallel to the optical system of the reduction imaging lens 30. As a result, in each spectroscopic optical system of the color information acquisition unit 40, the light beams emitted from each opening 41a, 41b, 41c of the pinhole array 41 are made to enter the openings of each lens 42a, 42b, 42c of the lens array 42.

[0026] The color information acquisition unit 40 has a function of separating the diffusely reflected light of the light irradiated on the object 90 and acquiring the amount of light in a predetermined wavelength band obtained by the separation. The color information acquisition unit 40 will be described in detail separately.

[0027] 1 is a so-called 45 / 0 optical system in which illumination light emitted from the line illumination light source 20 is incident on the object 90 at an angle of approximately 45 degrees, and the image sensor 44 (see FIG. 2) of the color information acquisition unit 40 receives light that is diffusely reflected in a vertical direction from the object 90. However, the configuration of the optical system is not limited to that illustrated in FIG. 1, and may be, for example, a so-called 0 / 45 optical system in which illumination light emitted from the line illumination light source 20 is incident on the object 90 at a vertical angle, and the image sensor 44 receives light that is diffused in a 45-degree direction from the object 90.

[0028] Next, the configuration of the color information acquisition unit 40 will be described with reference to Fig. 2 and Fig. 3. Fig. 2 is a cross-sectional view illustrating the color information acquisition unit 40 in Fig. 1, showing a portion of a cross section parallel to the XZ plane of the color information acquisition unit 40. Fig. 3 is a diagram illustrating a diffraction image in the spectral characteristic acquisition device 10 and light reception by the image sensor 44.

[0029] 2, color information acquisition unit 40 includes pinhole array 41, lens array 42, diffraction element 43, and image sensor 44. Color information acquisition unit 40 also includes package 45, spacer 46, cover glass 47, and glass substrates 48a, 48b, and 48c.

[0030] The pinhole array 41 has pinholes as openings that pass through light reflected from the object 90. The pinholes are arranged in the Z-axis direction at image plane positions where light incident from the reduction imaging lens 30 forms an image, and are arranged in an array in the X-axis direction at predetermined intervals. Fig. 2 shows an example in which three pinholes 41a, 41b, and 41c are arranged in the X-axis direction.

[0031] The pinhole array 41 is integrally formed on a transparent, flat glass substrate 48a serving as a light-transmitting frame. A thin metal film, such as nickel, is vapor-deposited on the transparent glass substrate, and openings corresponding to the pinholes are provided in an array to form the pinhole array 41. A beam of reflected light from each position in the color information acquisition region 90a of the object 90 is extracted by each pinhole provided in the pinhole array 41.

[0032] The array is not limited to the pinhole array 41, and may be a slit array having rectangular openings or a diagonal slit array in which rectangular slits are inclined with respect to the X-axis direction.

[0033] A transparent, flat glass substrate 48b serving as a light-transmitting frame is bonded to the surface of glass substrate 48a opposite the surface onto which reflected light from object 90 is incident, with the surfaces of the substrate facing each other. Lenses are arranged in an array at predetermined intervals in the X-axis direction on the surface of glass substrate 48b opposite the surface bonded to glass substrate 48a. FIG. 2 shows an example of a lens array 42 in which three lenses 42a, 42b, and 42c are arranged in the X-axis direction. Each of lenses 42a, 42b, and 42c of lens array 42 focuses the light beams that have passed through pinholes 41a, 41b, and 41c of pinhole array 41, forming an image by each lens on image sensor 44.

[0034] The lens array 42 is composed of multiple lenses 42a, 42b, and 42c arranged in a row in the X-axis direction, and each lens 42a, 42b, and 42c of the lens array 42 has the function of converting each diffused light beam that has passed through each opening 41a, 41b, and 41c of the pinhole array 41 into a weakly diffused light beam.

[0035] The term "weakly diffused light beam" refers to a diffused light beam that is closer to a parallel light beam than the incident diffused light beam. In other words, the diffused light beam is less diffused than the incident diffused light beam, i.e., is weaker.

[0036] The lenses 42a, 42b, and 42c that make up the lens array 42 are arranged at positions corresponding to the openings 41a, 41b, and 41c that make up the pinhole array 41, and each lens 42a, 42b, and 42c has a diameter that allows all of the light that has passed through the openings 41a, 41b, and 41c to enter. However, the planar shape of each lens 42a, 42b, and 42c does not have to be circular.

[0037] In this embodiment, the pinhole array 41 and the lens array 42 are arranged via glass substrates 48a and 48b, but this is not limiting. The thicknesses of the glass substrates 48a and 48b are determined so that the optical path length between the pinhole array 41 and the lens array 42 is shorter than the object-side focal length of each of the lenses 42a, 42b, and 42c of the lens array 42. In addition, in the lens array 42, it is preferable to shield the portions other than the openings of each of the lenses 42a, 42b, and 42c from light in order to eliminate stray light.

[0038] A transparent, flat glass substrate 48c serving as a light-transmitting frame is provided so as to face the lens array 42 in the Z-axis direction. The glass substrates 48b and 48c are bonded together via a spacer 46.

[0039] The spacer 46 is a component for providing a predetermined gap, i.e., space, between the glass substrate 48b and the glass substrate 48c, and is, for example, a component having a predetermined through-hole formed in the planar portion of a metal plate. On the surface of the spacer 46 facing the lens array 42, the portions of the spacer 46 that do not correspond to the through-holes contact and bond with the portions of the glass substrate 48b that do not have lenses. On the surface of the spacer 46 facing the diffraction element 43, the portions of the spacer 46 that do not correspond to the through-holes contact and bond with any portion of the glass substrate 48c. This provides a predetermined gap, i.e., space, between the glass substrate 48b and the glass substrate 48c. The through-holes may be small enough to accommodate each lens of the lens array 42, or large enough to accommodate multiple lenses.

[0040] A diffraction element 43 is provided on the surface of the glass substrate 48c facing the lens array 42, i.e., the surface onto which reflected light from the object 90 is incident. The diffraction element 43 has sawtooth patterns formed at predetermined intervals on the glass substrate 48c, and functions as a diffraction grating that diffracts and separates the incident light. The light beams that pass through the lenses 42a, 42b, and 42c of the lens array 42 are each separated by the diffraction element 43. Diffraction images corresponding to the respective light beams are formed on the image sensor 44.

[0041] It is preferable to use a blazed diffraction grating, which has improved diffraction efficiency for first-order diffracted light, as the diffraction element 43. By using a blazed diffraction grating as the diffraction element 43, it is possible to increase the diffraction efficiency of only the first-order diffracted light, thereby improving the light utilization efficiency of the optical system. This makes it possible to acquire a signal of sufficient quality in a short time, thereby shortening the time required to acquire spectral characteristics.

[0042] The image sensor 44 is a line sensor in which a plurality of pixels, each having a light-receiving area with its longitudinal direction in the Y-axis direction, are arranged in the X-axis direction. The image sensor 44 receives each diffraction image formed by the lens array 42 and the diffraction element 43 with a plurality of light-receiving elements at different positions, thereby acquiring the amount of incident light in a predetermined wavelength band. The image sensor 44 may be, for example, a MOS (Metal Oxide Semiconductor Device), a CMOS (Complementary Metal Oxide Semiconductor Device), or a CCD (Charge Coupled Device).

[0043] The diffraction axis of the diffraction element 43 is tilted at an angle α with respect to the X-axis direction. As shown in FIG. 3, a diffraction image tilted at an angle α with respect to the X-axis direction is incident on the image sensor 44. In FIG. 3, three diffraction patterns consisting of a zeroth-order diffraction image A, a +first-order diffraction image B, and a +second-order diffraction image C are shown lined up in the X-axis direction. Of the diffraction patterns, the image sensor 44 is positioned so that the first-order diffraction image B is received. In FIG. 3, the three first-order diffraction images generated by the three lens arrays are received by pixel regions 44a, 44b, and 44c of the image sensor 44 and converted into electrical signals. The electrical signals are output as color information data acquired by the color information acquisition unit 40.

[0044] In this way, the spectral characteristic acquisition device 10 eliminates crosstalk in the diffraction images, and makes it possible to obtain the spectral characteristics of the object 90 from the +1st-order diffraction image B. In the following description, the +1st-order diffraction image B may be simply referred to as the diffraction image.

[0045] 2, the image sensor 44 is fixed inside a package 45, and the opening of the package 45 is closed with a transparent cover glass 47 serving as a light-transmitting frame. The cover glass 47 is bonded to the surface of the glass substrate 48c on the side where the diffraction element 43 is not formed.

[0046] One pinhole (one of pinholes 41a, 41b, and 41c) in pinhole array 41, one corresponding lens (one of lenses 42a, 42b, and 42c) in lens array 42, part of diffraction element 43, i.e., the light beam transmitting portion of the lens, and a part of the pixel row (one of pixel areas 44a, 44b, and 44c) of image sensor 44 optically function as one spectroscope. Therefore, the part having the function of one spectroscope will be referred to as a spectroscopic sensor hereinafter.

[0047] 2 and 3 illustrate only three spectroscopic sensors, but the present invention is not limited to this and may include a configuration having multiple spectroscopic sensors. For example, if the image sensor 44 has 1,024 pixels and the number of pixels in the aforementioned partial pixel row is 10, 102 spectroscopic sensors can be configured. In other words, the color information acquisition unit 40 shown in FIGS. 1 to 3 can also be expressed as a "spectroscope array" having multiple spectroscopic sensors. The "spectroscope array" can also be defined as a device that splits light reflected from the object 90 and receives each of the split reflected light beams at a partial pixel row of the image sensor 44.

[0048] In the optical system for spectroscopy that constitutes the color information acquisition unit 40, the accuracy of acquiring the spectral characteristics is significantly affected by a relative positional shift between the diffraction image formed by the pinhole array 41, lens array 42, and diffraction element 43 and the image sensor 44. In this embodiment, to suppress this positional shift, the pinhole array 41, lens array 42, diffraction element 43, and image sensor 44 are stacked in the optical axis direction of the reduction imaging lens 30, bonded, and integrated.

[0049] <Temperature stabilization control of image sensors> Temperature stabilization control of the image sensor according to this embodiment will be described with reference to Figures 4 to 15. In the following description, a CCD image sensor will be used as an example of the image sensor 44 of the spectral characteristic acquisition device 10 described with reference to Figures 1 to 3. The CCD image sensor 44 is an example of the image sensor 44, and is an example of the image sensor according to this embodiment.

[0050] The detection accuracy of the CCD image sensor 44 is significantly affected by the temperature around the sensor. In this embodiment, to stabilize the temperature and ensure the accuracy of the CCD image sensor 44, a Peltier element 51 is used to control the temperature, and the reading results are corrected using a correction table 61 (see FIG. 4) for the targeted temperature. This embodiment also targets an image reading device configured as a spectrometer array having multiple spectroscopic sensors, such as the color information acquisition unit 40 described with reference to FIGS. 1 to 3. In this configuration, a temperature correction table based on the main scanning distribution of the CCD image sensor 44 according to temperature is provided, thereby suppressing the effect of temperature characteristics on the main scanning readout value.

[0051] Fig. 4 is a hardware configuration diagram of a control system 100 related to temperature stabilization control. As shown in Fig. 4, the control system 100 includes a control device 50 and a PC 60. The control device 50 is communicably connected to the PC 60. For example, the control device 50 is installed inside the spectral characteristic acquisition device 10, and the PC 60 is installed outside the spectral characteristic acquisition device 10.

[0052] The control device 50 includes a CCD image sensor 44, a Peltier element 51, a temperature sensor 52 (first temperature measurement unit), a temperature sensor 53 (second temperature measurement unit), a control unit 54, a Peltier control unit 55, an ADC (Analog-to-digital converter) 56, and a communication unit 57.

[0053] The Peltier element 51 switches between heat generation and heat absorption depending on the direction of the current flow. The greater the input power, the greater the effect. In this embodiment, the heat generation or heat absorption action of the Peltier element 51 controls the temperature of the CCD image sensor 44 to a desired temperature.

[0054] The temperature sensor 52 is installed around the CCD image sensor 44 and measures the temperature of the CCD image sensor 44 (sensor temperature).

[0055] The temperature sensor 53 does not directly measure the temperature of the CCD image sensor 44, but rather measures the temperature inside the spectroscopic characteristic acquisition device 10 (ambient temperature). The temperature inside the device measured by the temperature sensor 53 is used to determine the target temperature for temperature stabilization control. Because the temperature of the CCD image sensor 44 is controlled by the Peltier element 51, the temperature measured by the temperature sensor 52 installed near the CCD image sensor 44 is maintained near the target temperature, and any changes in the inside temperature cannot be detected by the temperature sensor 52. The temperature sensor 53 is installed, for example, inside the housing of the spectroscopic characteristic acquisition device 10 or at any position on the outer surface of the housing so that it can detect fluctuations in the inside temperature and the outside air temperature.

[0056] The control unit 54 acquires temperature information from the temperature sensors 52 and 53. The control unit 54 controls the operations of the CCD image sensor 44, the Peltier control unit 55, and the ADC 56 based on this acquired information.

[0057] The control unit 54 transmits a target temperature instruction value of the Peltier element 51 that controls the temperature of the CCD image sensor 44 to the Peltier control unit 55 .

[0058] The Peltier control unit 55 monitors information from a temperature sensor 52 installed near the CCD image sensor 44 based on the target temperature instruction value received from the control unit 54, and controls the Peltier element 51 so that the temperature of the CCD image sensor 44 becomes the target temperature. For example, the Peltier control unit 55 supplies the Peltier element 51 with power appropriate for achieving the target temperature.

[0059] Furthermore, Peltier control unit 55 can also provide control unit 54 with information on the amount of control (voltage, current value, etc.) for Peltier element 51. In this case, control unit 54 changes the target temperature value to an optimal temperature when the power supply to Peltier element 51 is large.

[0060] The control unit 54 also controls signals for reading the CCD image sensor 44. The sensor output output from the CCD image sensor 44 in response to a command from the control unit 54 is input to the ADC 56. The ADC 56 converts the sensor output into digital image data in a format that can be transmitted to the PC 60 in response to a command from the control unit 54. The image data converted by the ADC 56 is transmitted to the PC 60 via a communication unit 57 such as an interface (I / F).

[0061] Based on the environmental temperature information acquired from the temperature sensor 53, the control unit 54 selects one color calibration model suitable for the current environmental temperature, and sets a target temperature for the image sensor 44 based on the selected color calibration model. As will be described later, a plurality of color calibration models are prepared in a correction table 61 of the PC 60. The control unit 54 also transmits information about the selected color calibration model to the PC 60.

[0062] The PC 60 corrects the received image data according to the temperature.

[0063] The control device 50 also includes a motor for transporting the object 90 to be read, an optical sensor for use in transport control, a drive circuit for the line illumination light source 20, and the like.

[0064] 5 is a functional block diagram of the control system 100 related to the temperature stabilization control. As functions related to the temperature stabilization control, the control unit 54 has a temperature control unit 541 and a color calibration model determination unit 542, the Peltier control unit 55 has a temperature estimator 551 and a control amount determiner 552, and the PC 60 has a correction table 61 and a correction unit 62.

[0065] The temperature control unit 541 changes the target temperature of the CCD image sensor 44 based on the environmental temperature measured by the temperature sensor 53 or based on the controlled amount of at least one of the voltage and current used by the Peltier element 51 .

[0066] Based on the environmental temperature measured by the temperature sensor 53, the color calibration model determination unit 542 determines one color calibration model that is suitable for the current environmental temperature from among a plurality of color calibration models prepared in advance.

[0067] The temperature estimation unit 551 calculates the temperature distribution of the CCD image sensor 44 based on information about the sensor temperature measured by the temperature sensor 52 .

[0068] The control amount determination unit 552 controls the operation of the Peltier element 51 so that the temperature of each part of the CCD image sensor 44 becomes a target temperature.

[0069] The correction table 61 holds a plurality of color calibration models 61A to 61D (see FIG. 10) for performing color calibration of an image read by the spectrometer array (color information acquisition unit 40). The plurality of color calibration models 61A to 61D are each created according to an environmental temperature, as will be described later.

[0070] The correction unit 62 corrects the image data of the CCD image sensor 44. The correction unit 62 performs color calibration of the image using one color calibration model selected by the color calibration model determination unit 542 of the control unit 54 according to the environmental temperature.

[0071] Note that the control device 50 may be provided with functions similar to the correction table 61 and the correction unit 62, and the sensor correction according to the temperature may be performed in-house. In this case, the control system 100 related to the temperature stabilization control may not include the PC 60, and may be configured to include only the control device 50.

[0072] 6 is a hardware configuration diagram of the control unit 54, the Peltier control unit 55, and the PC 60. As shown in FIG. 6, the control unit 54, the Peltier control unit 55, and the PC 60 can be physically configured as a computer system including a CPU (Central Processing Unit) 101, a RAM (Random Access Memory) 102 and a ROM (Read Only Memory) 103 as main storage devices, an input device 104 such as a keyboard and a mouse as input devices, an output device 105 such as a display, a communication module 106 as a data transmission / reception device such as a network card, an auxiliary storage device 107, etc. The functions of the control unit 54, the Peltier control unit 55, and the PC 60 described with reference to FIG. 5 are realized by loading predetermined computer software (image processing programs) onto hardware such as the CPU 101 and the RAM 102, thereby operating the communication module 106, the input device 104, and the output device 105 under the control of the CPU 101, and reading and writing data from and to the RAM 102 and the auxiliary storage device 107.

[0073] FIG. 7 is a diagram illustrating an example of a sensor temperature estimation method.

[0074] 7(A) illustrates a configuration having three spectroscopic sensors as an example of a spectrometer array, and illustrates pixel areas 44a, 44b, and 44c corresponding to the spectroscopic sensors of a CCD image sensor 44. The left-right direction in the figure is illustrated as the pixel arrangement direction (X direction).

[0075] Figure 7(B) shows an example of the temperature distribution of the sensor temperature along the pixel direction corresponding to the configuration of (A). The horizontal axis of Figure 7(B) indicates the pixel direction, and each position corresponds to the position of each pixel in Figure 7(A). The vertical axis of Figure 7(B) indicates the sensor temperature at each pixel position. Also in Figure 7(B), the measurement points of the sensor temperature by temperature sensor 52 are shown by solid circle A.

[0076] The spectrometer array (CCD image sensor 44) has a length in the pixel direction (X direction), that is, it is formed so that the pixel direction is the longitudinal direction, so the temperature is not necessarily uniform along the pixel direction. Also, a temperature sensor 52 is used to know the control target of a Peltier element 51 for controlling the temperature of the CCD image sensor 44, but the position where the temperature sensor 52 is installed may not coincide with the temperature distribution of the CCD image sensor 44.

[0077] For this reason, the relationship between the temperature distribution of the temperature sensor 52 and the spectrometer array is acquired and understood in advance, and the temperature effect is corrected after the distribution is understood using the temperature sensor 52. One example of the temperature effect to be taken into account is the dark current, which is the current when there is no optical input. If the temperature rises by 5 to 7°C, the dark current may double, and this has an effect on the readout value of the CCD image sensor 44.

[0078] Furthermore, when the temperature rises, the physical expansion of the CCD image sensor 44, the metal plate on which the sensor is attached, the spectroscopic element, etc. may change the relationship between the dispersed light and the pixels of the CCD image sensor 44. If this relationship changes, the amount of light for each wavelength will differ, and the color detection accuracy will decrease.

[0079] Therefore, by understanding the temperature at the reading location and adjusting the reading method, such errors can be canceled out. In other words, as shown in Fig. 7(B), multiple temperature distribution estimation lines (three levels: high, medium, and low in the example of Fig. 7) are set according to the information on the sensor temperature measured by the temperature sensor 52.

[0080] For example, as shown by circle A in Fig. 7(B), the Peltier control unit 55 acquires information about the sensor temperature measured by the temperature sensor 52. Then, as shown in Fig. 7(B), one of the multiple temperature distribution patterns is selected to estimate the temperature distribution in the pixel direction of the CCD image sensor 44, and the temperature of the Peltier element 51 can be controlled based on the estimated temperature distribution.

[0081] 8A and 8B are diagrams showing another example of a sensor temperature estimation method, and the outlines of (A) and (B) of FIG. 8 are similar to those of (A) and (B) of FIG. 7, respectively.

[0082] The example in Figure 8 shows a case where two temperature sensors 52 are used to estimate the temperature of the CCD image sensor 44. When one temperature sensor 52 is used as in Figure 7, only the temperature at that point can be measured, as shown by circle A in Figure 7(B), making it difficult to grasp the overall trend.

[0083] On the other hand, to obtain a more accurate understanding of the temperature distribution, the sensor temperature can be measured at two points as shown by circles B and C in Figure 8(B) and interpolated to obtain a highly accurate temperature distribution of the sensor temperature along the pixel direction. As shown in Figure 8(B), one example of estimating the temperature distribution is to connect the two points with a straight line, but other interpolation methods such as connecting with a curved line may also be used.

[0084] 8 is associated with the block diagram of Fig. 4, it is provided with a plurality of temperature sensors 52 that measure the temperature of the CCD image sensor 44. The plurality of temperature sensors 52 are installed at appropriate intervals along the arrangement direction (X direction) of the plurality of pixels of the CCD image sensor 44.

[0085] In this configuration, the temperature estimation unit 551 of the Peltier control unit 55 calculates the temperature distribution of the CCD image sensor 44 based on information about the sensor temperatures measured by the multiple temperature sensors 52. Then, the control amount determination unit 552 can control the operation of the Peltier elements 51 individually for each region in the X direction of the CCD image sensor 44, in accordance with the temperature distribution calculated by the temperature estimation unit 551, so that the temperature of each part of the CCD image sensor 44 becomes the target temperature.

[0086] FIG. 9 is a flowchart of the sensor temperature stabilization control.

[0087] To ensure the color measurement accuracy of the image sensor 44, such as a CCD or CMOS, a reference image is read to create a correction table 61 (color calibration model). However, if the temperature of the image sensor 44 when the color calibration model is created differs from the temperature during actual use (the target control temperature by the Peltier element 51), the accuracy of the color calibration may deteriorate. For this reason, in this embodiment, multiple color calibration models 61A to 61D (see FIG. 10) are created in advance for each sensor temperature and are applied in the flow of FIG. 9.

[0088] In step S11, first, the temperature sensor 53 measures the environmental temperature in order to determine the target temperature for the Peltier element 51. The temperature control unit 541 of the control unit 54 acquires information on the environmental temperature from the temperature sensor 53.

[0089] In step S12, a color calibration model that is closest to the current ambient temperature is selected and applied. Details of the color calibration model are shown in FIG. 10. For example, the color calibration model determination unit 542 of the control unit 54 selects one color calibration model from the correction table 61 that corresponds to the ambient temperature. The color calibration model determination unit 542 of the control unit 54 then transmits information about the selected color calibration model to the correction unit 62 of the PC 60 via the communication unit 57 or the like.

[0090] In step S13, the temperature control unit 541 of the control unit 54 sets a target temperature of the Peltier element 51 that matches the color calibration model selected in step S12. For example, the central temperature of the color calibration model to be applied at that time is set as the target temperature. Because the CCD image sensor 44 has less dark noise at lower temperatures, the lower end of the temperature range of the color calibration model may be set as the eye temperature. The temperature control unit 541 of the control unit 54 transmits information about the set target temperature to the Peltier control unit 55, and the control amount determination unit 552 of the Peltier control unit 55 controls the temperature of the Peltier element 51 based on the target temperature information received from the control unit 54.

[0091] That is, the temperature control section 541 of the control section 54 functions to change the target temperature of the image sensor 44 based on the ambient temperature measured by the temperature sensor 53. The control amount determination section 552 of the Peltier control section 55 can adjust the control amount of the Peltier element 51 to control the operation of the Peltier element 51 so that the sensor temperature of the CCD image sensor 44 becomes the target temperature changed by the temperature control section 541 of the control section 54. This makes it possible to achieve color detection accuracy while performing appropriate temperature control in response to changes in ambient temperature.

[0092] Fig. 10 is a diagram showing an example of the configuration of color calibration models 61A to 61D. As shown in Fig. 10, a plurality of color calibration models 61A to 61D are created in advance according to the environmental temperature. Fig. 10 shows an example in which the temperature range of the environmental temperature is divided into four parts, and four color calibration models 61A, 61B, 61C, and 61D are created.

[0093] 9, for example, color calibration model determination unit 542 of control unit 54 selects one color calibration model based on which of color calibration models 61A, 61B, 61C, or 61D the current ambient temperature falls within, and temperature control unit 541 determines the target temperature based on the selected color calibration model. After determining the target temperature, control variable determination unit 552 of Peltier control unit 55 controls the temperature using Peltier element 51 to maintain a constant temperature of CCD image sensor 44.

[0094] The number of divisions for color calibration models 61A, 61B, 61C, and 61D is determined based on the width of the temperature range supported by the device, the width of the temperature rise range of the CCD image sensor 44, the target accuracy, and the time allowable for creating the color calibration model. For example, the number of divisions should be increased when the temperature range supported is wide or the temperature fluctuations of the CCD image sensor 44 are large. The number of divisions should also be increased when the target accuracy is high. Conversely, when the temperature effect is relatively minor, the number of divisions should be reduced, taking into account the effort required to create the model.

[0095] Each of the color calibration models 61A, 61B, 61C, and 61D is preferably created based on the temperature characteristics of each pixel of the CCD image sensor 44, as described with reference to Figures 7(B) and 8(B), for example. This makes it possible to perform correction in accordance with the temperature characteristics of each pixel of the CCD image sensor 44, and image data can be obtained with high accuracy.

[0096] Fig. 11 is a diagram showing an example of setting the target temperature in a color calibration model. With reference to Fig. 11, a method for determining the color calibration model and the target temperature (target temperature) of the Peltier element 51 is shown. For simplicity of explanation, Fig. 11 shows only two color calibration models 61A and 61B.

[0097] As shown in FIG. 11, the target temperature can be set by, for example, two methods.

[0098] As a first example, for color calibration model 61A, the center temperature of the temperature range of color calibration model 61A is set as the target temperature. If there is a large temperature change due to changes in the environmental temperature, it is better to set the target temperature at the center of the temperature range and take into account variations above and below the environmental temperature.

[0099] As a second example, for color calibration model 61B, the target temperature is set to the lower end of the temperature range of color calibration model 61B. A lower sensor temperature is desirable because higher temperatures increase dark current. Therefore, when temperature change is small, the lower end of the temperature range of color calibration model 61B is set as the target temperature.

[0100] For example, in step S13 of FIG. 9, the control unit 54 can set the target temperature of the Peltier element 51 using one of the two methods illustrated in FIG.

[0101] As described above, the spectral characteristic acquisition device 10 as an example of an image reading device according to this embodiment includes: a line illumination light source 20 that irradiates light onto a reading object 90 that is being relatively transported in a predetermined direction (Y direction); a color information acquisition unit 40 as a spectrometer array that disperses light reflected from the reading object 90 and receives each of the dispersed reflected light beams at some pixel rows of a CCD image sensor 44; a temperature sensor 52 that measures the sensor temperature of the CCD image sensor 44; a temperature sensor 53 that measures the ambient temperature of the color information acquisition unit 40; a Peltier element 51 that controls the sensor temperature to a target temperature; a correction table 61 that holds multiple color calibration models for color calibration of an image read by the color information acquisition unit 40 in accordance with the ambient temperature; and a color calibration model determination unit 542 in a control unit 54 that selects one color calibration model from the multiple color calibration models 61A to 61D in the correction table 61 in accordance with the ambient temperature.

[0102] With this configuration, multiple patterns of color calibration models 61A-61D in the main scanning direction of the CCD image sensor 44 are generated in advance according to the ambient temperature, and the color calibration model determination unit 542 selects an appropriate color calibration model based on the correction temperature (i.e., ambient temperature) of the Peltier element 51. The correction unit 62 of the PC 60 can then correct the read image using the selected color calibration model. This prevents a situation in which, when the target temperature for temperature control of the CCD image sensor 44 by the Peltier element 51 is changed depending on the ambient temperature, a discrepancy occurs between the sensor temperature of the CCD image sensor 44 when the image to be corrected was acquired and the assumed temperature of the color calibration model used for correction, resulting in a deterioration in image correction accuracy. Therefore, a read result that is appropriately corrected in response to changes in ambient temperature can be obtained. Furthermore, the above configuration also enables appropriate temperature correction and correction of read values ​​to be performed for an image reading device that uses a spectrometer array in which multiple spectroscopic sensors are arranged, such as the spectral characteristics acquisition device 10 of this embodiment. As a result, in this embodiment, temperature correction using the Peltier element 51 can be performed accurately in the image reading device.

[0103] Fig. 12 is a diagram illustrating the relationship between the sensor temperature stabilization control and the ambient temperature around the sensor. The horizontal axis of Fig. 12 represents time (seconds), and the vertical axis represents ambient temperature (°C), showing the transition of the ambient temperature over time at the start of the spectroscopic characteristic acquisition device 10.

[0104] Fig. 12 shows a case where the target temperature of the Peltier element 51 is determined taking into consideration the ambient temperature near the CCD image sensor 44. The temperature shown in Fig. 12 is the ambient temperature near the CCD image sensor 44. In Fig. 12, temperature control (sensor temperature stabilization control in Fig. 9) is not initially performed before time t1. This is because when temperature control is started, the sensor temperature will become different from the ambient temperature.

[0105] Immediately after the power is turned on, the ambient temperature rises due to machine operation and power consumption, and stabilizes after a certain time has passed (after time t1 in FIG. 12). If the temperature at which the ambient temperature has stabilized is set as the target temperature to be controlled by Peltier element 51, the difference between the target temperature and the ambient temperature becomes smaller, and less power is input to Peltier element 51, resulting in energy savings. Furthermore, reducing the difference between the ambient temperature and the target temperature makes temperature control easier.

[0106] Therefore, it is preferable to monitor the ambient temperature and determine and control the target temperature of the Peltier element 51 after a certain time has passed or when the temperature fluctuation has settled within a certain range, such as after time t1 in FIG.

[0107] For example, when performing the sensor temperature stabilization control of FIG. 9, the temperature control unit 541 of the control unit 54 or the control amount determination unit 552 of the Peltier control unit 55 may be configured to monitor the sensor temperature using the temperature sensor 52, and start temperature control of the Peltier element 51 through the sensor temperature stabilization control after time t1 when the sensor temperature falls within the steady temperature range as shown in FIG. 12.

[0108] Alternatively, a configuration may be adopted in which a temperature measured by a temperature sensor other than the temperature sensor 52 near the Peltier element 51 (for example, the environmental temperature measured by the temperature sensor 53) is used to determine whether or not to start the sensor temperature stabilization control shown in FIG. 12.

[0109] 13 is a diagram illustrating sensor temperature stabilization control when the ambient temperature changes significantly. The horizontal axis of FIG. 13 represents time (seconds), and the vertical axis represents ambient temperature (°C), showing the transition of ambient temperature over time at the start of the spectroscopic characteristic acquisition device 10.

[0110] In the case of Fig. 13, a sensor (temperature sensor 53 shown in Fig. 4) for measuring the ambient temperature (environmental temperature) inside the device is provided in addition to the temperature control sensor (temperature sensor 52 shown in Fig. 4) for Peltier element 51. This is because the temperature sensor 52 for controlling the Peltier element controls the temperature using Peltier element 51, and therefore the temperature is kept constant, making it impossible to determine the environmental temperature.

[0111] Immediately after the power is turned on at time t2 in Figure 13, the temperature rises due to the operation inside the device, and after time t3, the temperature stabilizes and becomes constant to a certain extent. However, as seen from time t4 onwards, the temperature may change from the initial temperature, for example, due to the ambient temperature rising due to the operation of the indoor air conditioner.

[0112] If an attempt is made to maintain the ambient temperature before the temperature rise despite the ambient temperature having risen, it is necessary to continue to lower the sensor temperature using the Peltier element 51. This has the disadvantages of increasing power consumption and possibly exceeding the control range of the Peltier element 51 if the temperature change is large.

[0113] Therefore, if the ambient temperature deviates significantly from the initial temperature, the temperature control section 541 of the control section 54 changes the target value of the Peltier element 51 to a value that matches that temperature. This makes it possible to easily change the power for temperature control and to control the temperature by minimizing the difference between the ambient temperature and the target temperature.

[0114] The example in Figure 13 describes the case where the temperature rises from the initial state and stabilizes, but if the temperature drops, control is performed based on the dropped temperature.

[0115] FIG. 14 is a flowchart of the sensor temperature stabilization control taking into consideration the ambient temperature fluctuation shown in FIG.

[0116] In step S21, the sensor temperature stabilization control shown in Fig. 4 is started. At this point, the target temperature of the Peltier element is not changed to match the ambient temperature.

[0117] In step S22, the temperature control unit 541 of the control unit 54 or the control amount determination unit 552 of the Peltier control unit 55 waits for the temperature to stabilize until the ambient temperature (sensor temperature or environmental temperature) stabilizes to a certain extent after the power of the spectroscopic characteristic acquisition device 10 is turned on (for example, until it falls within a predetermined steady temperature range as shown in FIG. 12).

[0118] In step S23, as long as the ambient temperature is within a certain temperature range (Yes in S23), the control amount determination unit 552 of the Peltier control unit 55 continues to maintain the sensor temperature based on the target temperature set in the sensor temperature stabilization control in step S21.

[0119] Note that the flow in Figure 14 focuses on temperature control, but if the user issues a command to start reading before the temperature has stabilized, the system will wait for the temperature to stabilize before starting scanning, as in steps S22 to S23, and will only start scanning once the temperature has stabilized.

[0120] On the other hand, if the ambient temperature is outside the constant temperature range (No in S23), the process proceeds to step S24 to change the target temperature and color calibration model in the sensor temperature stabilization control by the temperature control unit of control unit 54 and the color calibration model determination unit 542.

[0121] In step S24, since it is not desirable to change the color calibration model during scanning, the process waits until the scanning is completed (No in S24). This is because changing the color calibration model during one scan may result in a change in characteristics within that scan. If scanning is not in progress or if the ongoing scan has completed (Yes in S24), the process proceeds to step S25.

[0122] In step S25, the temperature control unit 541 of the control unit 54 changes the target temperature of the Peltier element 51. Furthermore, the color calibration model determination unit 542 of the control unit 54 changes the color calibration model to match the changed target temperature.

[0123] In step S26, since the target temperature is not reached immediately after the target temperature is switched, the temperature control unit 541 of the control unit 54 or the control amount determination unit 552 of the Peltier control unit 55 waits for the temperature to stabilize. Once the temperature has stabilized, the process returns to step S23, and as long as the temperature is within a certain range, the control amount determination unit 552 of the Peltier control unit 55 continues to maintain the sensor temperature based on the target temperature changed in step S25 in step S23, as in the case described above.

[0124] 15A and 15B are diagrams illustrating another example of sensor temperature stabilization control that takes ambient temperature fluctuations into consideration. Fig. 15A shows the time progression of the target temperature, and Fig. 15B shows the time progression of the value of the current supplied to Peltier element 51.

[0125] The example of FIG. 15 shows a case where the target temperature is changed by the current of the Peltier element 51, rather than by the ambient temperature sensor (temperature sensor 52 or temperature sensor 53).

[0126] Because the temperature is controlled by the Peltier element 51, the temperature of the CCD image sensor 44 appears to be constant, but if the ambient temperature changes from the initial state, the power required to maintain that temperature may increase. For example, if the initial ambient temperature was 30°C and the target was 32°C, then the temperature may be maintained at 32°C even if the ambient temperature drops to 28°C.

[0127] In such cases, the change cannot be detected by looking at the temperature sensor alone, so the amount of current (when maintaining voltage and controlling input power with current) or power (when controlling with both voltage and current) of the Peltier control unit 55 attempting to maintain that temperature is looked at, and the target temperature of the Peltier element 51 is changed so that the amount of input power is reduced. At the same time, the color calibration model is changed to match that temperature. Note that a control method that maintains current and controls input power with voltage may also be used. The voltage and current may be looked at by looking at the control target values ​​of the voltage and current of the Peltier control unit 55, or by actually measuring the voltage and current.

[0128] For example, in the example of Fig. 15, when the ambient temperature drops at time t5, if the target temperature remains constant as shown in Fig. 15(A), the current value of Peltier element 51 begins to increase as shown in Fig. 15(B) in order to maintain the sensor temperature at the target temperature. Even in this case, by focusing on the fluctuations in the current value and power value supplied from Peltier control unit 55 to Peltier element 51, control unit 54 can perform control to lower the target temperature so as to suppress the increase in the current value and power value of Peltier element 51.

[0129] 15, the temperature control unit 541 of the control unit 54 functions to change the target temperature based on the control amount of at least one of the voltage and current used by the Peltier element 51. The control amount determination unit 552 of the Peltier control unit 55 can control the Peltier element 51 so that the sensor temperature of the CCD image sensor 44 becomes the target temperature changed by the temperature control unit 541 of the control unit 54. This makes it possible to achieve color detection accuracy while performing appropriate temperature control in response to changes in the ambient temperature.

[0130] The present embodiment has been described above with reference to specific examples. However, the present disclosure is not limited to these specific examples. Design modifications to these specific examples made by a person skilled in the art as appropriate are also included within the scope of the present disclosure as long as they comprise the features of the present disclosure. The elements of the above-described specific examples, as well as their arrangement, conditions, shape, etc., are not limited to those exemplified and can be modified as appropriate. The elements of the above-described specific examples can be combined in various ways as appropriate, as long as no technical contradictions arise.

[0131] For example, aspects of the present invention are as follows. <1> a light source that irradiates light onto a reading object that is relatively transported in a predetermined direction; a spectrometer array that splits the light reflected from the object to be read and receives each of the split reflected light beams at a pixel row of an image sensor; a first temperature measurement unit that measures a sensor temperature of the image sensor; a second temperature measurement unit that measures an environmental temperature of the spectrometer array; a Peltier element that controls the sensor temperature to a target temperature; a correction table that stores a plurality of color calibration models for performing color calibration of the image read by the spectrometer array according to the environmental temperature; a control unit that selects one color calibration model from the plurality of color calibration models in the correction table in accordance with the environmental temperature; An image reading device comprising: <2> The Peltier element controls the sensor temperature to the target temperature by generating or absorbing heat. The aforementioned <1> 2. The image reading apparatus according to claim 1 . <3> the color calibration model is created based on the temperature characteristics of each pixel of the image sensor; The aforementioned <1> or <2> 2. The image reading apparatus according to claim 1 . <4> a temperature estimation unit that has a plurality of the first temperature measurement units and calculates the temperature distribution of the image sensor; The aforementioned <1> ~ <3> 10. The image reading device according to claim 9, <5> a temperature control unit that changes the target temperature based on the environmental temperature measured by the second temperature measurement unit; a Peltier control unit that controls the Peltier element so that the sensor temperature becomes the target temperature changed by the temperature control unit; Equipped with The aforementioned <1> ~ <4> 10. The image reading device according to claim 9, <6> a temperature control unit that changes the target temperature based on a control amount of at least one of a voltage and a current used by the Peltier element; a Peltier control unit that controls the Peltier element so that the sensor temperature becomes the target temperature changed by the temperature control unit; Equipped with The aforementioned <1> ~ <5> 10. The image reading device according to claim 9, [Explanation of symbols]

[0132] 1. Color measurement device (image reading device) 10 Spectral characteristics acquisition device (reading unit) 20 Line lighting light source (light source) 40 Color information acquisition unit (spectroscope array) 44 Image sensor, CCD image sensor (image sensor) 51 Peltier element 52 Temperature sensor (first temperature measurement unit) 53 Temperature sensor (second temperature measurement unit) 54 Control Unit 541 Temperature control unit 542 Color calibration model determination unit 55 Peltier control unit 551 Temperature estimation section 552 Control amount determination unit 60 PC 61 Correction Table 61A~61D Color Calibration Model 62 Correction unit 90 Reading Object [Prior art documents] [Patent documents]

[0133] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-145224

Claims

1. a light source that irradiates light onto a reading object that is relatively transported in a predetermined direction; a spectrometer array that splits the light reflected from the object to be read and receives each of the split reflected light beams at a pixel row of an image sensor; a first temperature measurement unit that measures a sensor temperature of the image sensor; a second temperature measurement unit that measures an environmental temperature of the spectrometer array; a Peltier element that controls the sensor temperature to a target temperature; a correction table that stores a plurality of color calibration models for performing color calibration of the image read by the spectrometer array according to the environmental temperature; a control unit that selects one color calibration model from the plurality of color calibration models in the correction table in accordance with the environmental temperature; Equipped with the color calibration model is created based on the temperature characteristics of each pixel of the image sensor; Image reading device.

2. The Peltier element controls the sensor temperature to the target temperature by generating or absorbing heat.

2. The image reading device according to claim 1.

3. a temperature estimation unit that has a plurality of the first temperature measurement units and calculates a temperature distribution of the image sensor; 3. The image reading device according to claim 1 or 2.

4. a temperature control unit that changes the target temperature based on the environmental temperature measured by the second temperature measurement unit; a Peltier control unit that controls the Peltier element so that the sensor temperature becomes the target temperature changed by the temperature control unit; Equipped with 2. The image reading device according to claim 1.

5. a temperature control unit that changes the target temperature based on a control amount of at least one of a voltage and a current used by the Peltier element; a Peltier control unit that controls the Peltier element so that the sensor temperature becomes the target temperature changed by the temperature control unit; Equipped with 2. The image reading device according to claim 1.

Images