WO2023277924A1 - Systems, methods, and devices for calibration of color measuring devices - Google Patents
Systems, methods, and devices for calibration of color measuring devices Download PDFInfo
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- WO2023277924A1 WO2023277924A1 PCT/US2021/040299 US2021040299W WO2023277924A1 WO 2023277924 A1 WO2023277924 A1 WO 2023277924A1 US 2021040299 W US2021040299 W US 2021040299W WO 2023277924 A1 WO2023277924 A1 WO 2023277924A1
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- calibration
- photodetector
- measurement
- measuring device
- color measuring
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- 238000000034 method Methods 0.000 title claims abstract description 25
- 238000005259 measurement Methods 0.000 claims abstract description 88
- 230000005855 radiation Effects 0.000 claims description 48
- 230000003287 optical effect Effects 0.000 claims description 22
- 239000000463 material Substances 0.000 claims description 19
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- 239000004983 Polymer Dispersed Liquid Crystal Substances 0.000 claims description 4
- 230000008859 change Effects 0.000 claims description 2
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- 238000010586 diagram Methods 0.000 description 4
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- 238000012986 modification Methods 0.000 description 2
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- 230000002195 synergetic effect Effects 0.000 description 1
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Classifications
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N1/00—Scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission; Details thereof
- H04N1/40—Picture signal circuits
- H04N1/407—Control or modification of tonal gradation or of extreme levels, e.g. background level
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
- G01J3/46—Measurement of colour; Colour measuring devices, e.g. colorimeters
- G01J3/50—Measurement of colour; Colour measuring devices, e.g. colorimeters using electric radiation detectors
- G01J3/501—Colorimeters using spectrally-selective light sources, e.g. LEDs
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
- G01J3/46—Measurement of colour; Colour measuring devices, e.g. colorimeters
- G01J3/52—Measurement of colour; Colour measuring devices, e.g. colorimeters using colour charts
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
- G01J3/46—Measurement of colour; Colour measuring devices, e.g. colorimeters
- G01J3/52—Measurement of colour; Colour measuring devices, e.g. colorimeters using colour charts
- G01J3/524—Calibration of colorimeters
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N1/00—Scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission; Details thereof
- H04N1/46—Colour picture communication systems
- H04N1/56—Processing of colour picture signals
- H04N1/60—Colour correction or control
- H04N1/603—Colour correction or control controlled by characteristics of the picture signal generator or the picture reproducer
- H04N1/6033—Colour correction or control controlled by characteristics of the picture signal generator or the picture reproducer using test pattern analysis
- H04N1/6044—Colour correction or control controlled by characteristics of the picture signal generator or the picture reproducer using test pattern analysis involving a sensor integrated in the machine or otherwise specifically adapted to read the test pattern
Abstract
An example color measuring device calibration system is described comprising a color measuring device and a calibration surface. An example method for calibrating a color measuring device is also described, comprising providing a calibration element controllable to provide a calibration reference state and an optically transparent state, wherein the calibration element is in the field of view of a sensor; controlling, by a controller, the calibration element to provide the calibration reference state, generating, by the sensor, a sensor measurement output when the calibration element is in the reference state, and generating, by the controller, a calibration value based on the sensor measurement output.
Description
SYSTEMS. METHODS. AND DEVICES FOR CALIBRATION OF COLOR
MEASURING DEVICES
BACKGROUND
[001] Some printing devices may comprise a color measuring device. The color measuring devices may be calibrated.
[002] For example, some color measuring devices may be calibrated using a reference tile. The reference tile is placed in front of the color measuring device during a calibration measurement and is removed during color measuring of a target by the color measuring device.
BRIEF DESCRIPTION
[003] Some non-limiting examples of the present disclosure will be described in the following with reference to the appended drawings, in which:
[004] Figures 1 A and 1 B are schematic diagrams illustrating examples of a color measuring device according to examples;
[005] Figures 2A and 2B show schematic diagrams of an electrical circuit comprising a calibration surface as disclosed herein;
[006] Figure 3 shows a calibration surface according to examples;
[007] Figure 4 shows a printing device comprising a color measuring device according to examples;
[008] Figure 5 is a flowchart illustrating examples of a method for calibration of a color measuring device in accordance with examples disclosed herein;
[009] Figure 6 is a flowchart illustrating examples of a method for calibrating a color measuring device in accordance with examples disclosed herein;
[0010] Figure 7 is a schematic depiction of a controller including a processor and a non-transitory machine-readable storage medium according to an example; and
[0011] Figure 8 is a block diagram of the instructions to control a color measuring device and a calibration surface for a calibration measurement and/or a color measurement.
DETAILED DESCRIPTION
[0012] The present disclosure presents examples of devices, systems, and methods for calibrating a color measuring device. The present disclosure also presents examples of devices, systems, and methods for measuring color of a printed image with a color measuring device calibrated according to the examples disclosed herein.
[0013] In some printing processes, it may be desired to increase color uniformity of images printed by a printing device. In some printing processes, it may be desired to increase uniformity across multiple printing devices. Printing device settings may be monitored and adjusted to increase color uniformity.
[0014] In order to increase the color uniformity of printed images output by a printing device or by multiple printing devices, a color measuring device may be used. The color measuring device may measure color in a printed image or in a sample of printed images (which may comprise, for example, an ordinary printing output of the printing device or a color test patch/chart). A controlling device or an operator may adjust a printer setting based on the color measurement results accordingly. Adjusting the printing device settings in this manner may increase uniformity of the printing output.
[0015] The color measuring device may be calibrated to adjust its color measurement output based on the present conditions (such as ambient lighting or electrical noise).
[0016] In examples, a system for calibrating a color measuring device is provided. The system for calibrating the color measuring device comprises a color measuring device and a calibration surface. The color measuring device comprises a radiation source and a sensor. The calibration surface is to change between a calibration reference state and an optically transparent state. The system also comprises a controller to control the calibration surface to be in a calibration reference state for a calibration measurement, and to control the radiation source and the sensor to generate a calibration value, and to control the calibration surface to be in an optically transparent state for color measurement (for example, color measurement of a printed image).
[0017] FIG. 1A shows a schematic top view of a system for calibrating a color measuring device according to an example. The system comprises a color measuring device 10 and a calibration surface 100. The color measuring device 10 comprises a sensor 102. In examples, the sensor 102 may comprise a photodetector or a photosensor. For example, the sensor 102 may comprise a CMOS light sensor. In examples, the sensor 102 may comprise a matrix of CMOS light sensors. In examples, the sensor 102 may comprise a photodiode or a photodiode matrix. The color measuring device 10 also comprises a radiation source 104a,b. In the example, the radiation source comprises two radiations sources 104a,b. In examples, the radiation source 104a,b may comprise a light source. The radiation source 104a,b may comprise, for example, a light-emitting diode(s) (LED light source). The radiation source 104a,b may, for example, comprise a white LED which may irradiate the calibration surface with a light beam from 3 RGB diodes (i.e., light in the 474 THz, 535 THz, 638 THz frequency range). In examples, the intensity of the radiation (set by the controller or at the light source) may, for example, range between 1 to 5 W (the intensity of the irradiation measured at the calibration
surface may differ from the intensity provided at the light source). The calibration surface 100 is in the field of view F of the sensor 102.
[0018] The calibration surface 100 may be controllable between two different states, which may be referred to as optical states. In a first state, shown in Figure 1a, the calibration surface 100 is in an optically transparent state. In this state, the material properties of the calibration surface 100 are such that radiation (for example, light) is substantially fully transmitted through the calibration surface 100. Thus, the calibration surface 100, in such state, becomes optically transparent and allows transmission of incident radiation. Radiation that reaches or contacts the calibration surface 100 may be transmitted through the calibration surface 100. In a second state, shown in Figure 1b, the calibration surface 100 is in a calibration reference state. In the calibration reference state the material properties of the calibration surface 100 are such that radiation that reaches the calibration surface 100 is reflected and/or scattered. The reflection and/or scattering of the radiation by the calibration surface 100 renders the calibration surface 100 opaque (this opacity is illustrated in FIG. 1 B with dots in the calibration surface 100). In the calibration reference state, the calibration surface 100 may exhibit a substantially white color. The opacity or white color of the calibration surface in the calibration reference state renders it suitable for obtaining values for calibration parameters used in determining a dynamic range of the color measuring device. For example, the calibration parameters may comprise a white reference level and a dark reference level to determine the dynamic range of the color measuring device. The obtained dynamic range may reflect the minimum and maximum color measurement values that may be obtained with the color measuring device in the conditions (for example, lighting and electrical noise) present during the calibration (which conditions may be present in a subsequent color measurement). A controller 110 may control the calibration surface to provide the calibration reference state. The controller may control the radiation source 104a,b and the sensor 102 to obtain a measurement of the white reference level by controlling the radiation source 104a,b to irradiate the calibration surface 100, and generate a sensor measurement by sensor 102 accordingly. The
controller may control the radiation source 104a,b and the sensor 102 to obtain a measurement of the dark reference level by controlling the radiation source 104a,b to not irradiate the calibration surface (e.g., turning it off) and generate a measurement by the sensor 102 accordingly. The measured white and dark reference levels may be used to determine the dynamic range of the color measuring device. When a calibration measurement is not being performed, the calibration surface may be controlled to be in the optically transparent state. To obtain the optically transparent state the controller may, for example, apply no voltage to the calibration surface (such that it is OFF), or may apply a voltage that is less than the minimum threshold voltage necessary to obtain the optically transparent state. With the calibration surface in the optically transparent state, the color measuring device may carry out its color measuring function of a target T. While two optical states are described, the calibration surface may be controlled to render further states (for example, with varying degrees of optical transparency or opacity) depending of the magnitude of the voltage applied across the calibration surface.
[0019] A target T is shown in FIGS. A,B to illustrate the relative position of a surface to be measured by the color measuring device 10 (such a surface may comprise, for example, a printed image). As shown in the top view, the target T is on the opposite side of the calibration surface 100 with respect to the color measuring device 10. The target T may comprise, for example, a printed image. The calibration surface 100 is connected to a controller 110. In order to carry out a color measurement by the color measuring device 10, the controller 110 may control the calibration surface 100 to provide the optically transparent state by applying a voltage across the calibration surface 100. In that manner, radiation emitted by the radiation source 104a,b is transmitted through the calibration surface 100 and it may reach the target T (and be reflected by the target T) such that the sensor 102 may make a color measurement.
[0020] In examples, the calibration surface 100 may be provided integrally with the color measuring device. In examples, the calibration surface 100 may be provided as a lid or cover of a color measuring device. In examples, the
calibration surface 100 may be provided as a lid or cover of a spectrophotometer.
[0021] FIG. 2A shows a cross-section view of the calibration surface 100 in a calibration reference state (for example, opaque). In examples, the calibration surface 100 comprises an electrochromic material 101 provided between first and second transparent plates 115a,b. The plates 115a,b may comprise, for example, a plastic sheet or a glass pane. In examples, the calibration surface comprises a material with voltage-dependent light transmittance. The calibration surface comprises material whose particles physically align in response to an applied voltage such that light may be transmitted through the material, and whose particles may not align when no voltage is provided across the calibration surface (or for example, when the voltage V is not equal to nor greater than the minimum voltage required the particles to align). In that case, as shown in the example of FIG. 2A, the particles may not align and light or radiation is reflected or scattered, as indicated by the arrows.
[0022] The calibration surface 100 may be connected to the controller 110 such that a voltage may be provided across the calibration surface 100 by the controller 110. The connection may comprise, for example, a first electrical terminal 116a and second electrical terminal 116b for electrical connection to the controller 110. The first and second electrical terminals 116a,b may comprise, for example, a conductive material such as a conductive film or a conductive paint. The conductive material may comprise, for example, indium tin oxide material (ITO), which is optically transparent. As schematically depicted in FIG. 2B, the particles align when a voltage V is applied across the calibration surface 100, thereby allowing light to be transmitted through the calibration surface as indicated by the arrow.
[0023] FIG. 3 shows another view of a calibration surface 100 according to examples. The calibration surface may comprise substantially any shape and/or dimension if a calibration surface area is provided in the field of view of the sensor of the color measuring device that is suitable for making a calibration measurement. In examples, the calibration surface may be a planar surface. In
examples, the calibration surface may be a non-planar surface (for example, an undulating surface).
[0024] As shown in FIG. 3, the calibration surface may comprise a height (h), a width (w), and depth (d). The calibration surface may be provided in any suitable dimensions. In examples, the height (h) of the calibration surface 100 may be in the range of 25 to 30 mm. In examples, the width (w) of the calibration surface 100 may be in the range of 25 to 30 mm. In examples, the depth (d) of the calibration surface 100 may be in the range of 1 to 5 mm. The controller 110 may apply a voltage equal to or exceeding a minimum threshold to the calibration surface 100 such that an optically transparent state may be attained by the calibration surface 100. The minimum magnitude of the voltage V to be applied to the calibration surface to attain an optically transparent state may depend on the dimensions of the calibration surface 100 and/or the amount of electrochromic material or particles present in the calibration surface 100. For example, a larger calibration surface may require a greater voltage to attain optical transparency than a smaller calibration surface. For example, a calibration surface comprising a greater amount of electrochromic material may require a greater voltage to attain optical transparency than a calibration surface comprising less electrochromic material. A voltage of any suitable magnitude to attain optical transparency may be applied. In examples, the voltage (V) applied may be in the range of 1V to 300V. The voltage V may be applied across the calibration surface, between a first electrical terminal and a second electrical terminal connected to the calibration surface, such that it generates an electrical field affecting the calibration surface 100. The voltage V may be applied across the calibration surface, between a first electrical terminal and a second electrical terminal connected to the calibration surface, such that it generates an electrical field affecting an electrochromic material of the calibration surface 100. The electrochromic material may comprise, for example, polymer-dispersed liquid crystals (PDLC). In examples, the electrochromic material may comprise an Organic Light-Emitting Diode (OLED) display.
[0025] In examples, the voltage (V) applied to the electrochromic material to attain optical transparency may be provided as an alternating current (AC) waveform of any suitable frequency. In examples, the applied AC voltage may have a frequency (f) of 60 Hz. In examples, the applied AC voltage may have a frequency (f) of 1kHz. In examples, the voltage may be provided as a DC (direct current) waveform, having any suitable magnitude and direction.
[0026] In examples, a printing device is provided, the printing device comprising a spectrophotometer for color measurement of a printed image output by the printing device; a spectrophotometer calibration element controllable to switch between a first optical state and a second optical state; and a controller to control the calibration element to switch to the first optical state for a calibration measurement, and to control the calibration element to switch to the second optical state for color measurement.
[0027] FIG. 4 schematically shows a printing device 400 according to examples. The printing device 400 comprises a color measuring device 402 and a calibration surface 404. The color measuring device 402 may comprise, for example, a spectrophotometer. The calibration surface 404 is in the field of view F of the spectrophotometer (or color measuring device) 402. The calibration surface 404 may comprise an electrochromic material (that is, a material whose light transmittance depends on the voltage applied to the material). The calibration surface 404 may be (permanently) fixed or attached to the printing device 400, or may be removably attached to the printing device 400. As the calibration surface 404 may be controllable to switch between two optical states, a first optical state suitable for calibration of the color measuring device, and a second optical state suitable for color measurement of a printed image output by the printing device, it is not necessary to remove the calibration surface 404 after a calibration measurement and prior to a color measurement by the color measuring device 402. The calibration surface 404 may be controlled to be in an optically transparent state (a color measuring mode) in which the spectrophotometer may perform a color measuring function of a target T (for example, a printed image) on the other side of the calibration surface 404. In
examples, the spectrophotometer and calibration surface may be provided on a carriage 406 of a printing device, as shown in FIG. 4. Thus, the spectrophotometer and calibration surface may be displaced along the carriage 406 and may be displaced to obtain a color measurement from a position in the carriage 406. The printing device may comprise printheads 408 and an encoder 410. The encoder 410 may, for example, sense or measure a displacement or a position of the carriage 406 which input may be used as input for operation of the carriage motor. The encoder 410 input may also be used to determine or estimate a position of the color measuring device 402 along the carriage axis. In examples, a color measuring device (or spectrophotometer) is not provided on a carriage of a printing device, and the color measuring device is instead provided on another component of the printing device.
[0028] In examples, a method for calibrating a color measuring device is provided, the method comprising providing a calibration element controllable to provide a calibration reference state and an optically transparent state, wherein the calibration element is in the field of view of the photodetector, controlling, by a controller, the calibration element to provide the calibration reference state, generating, by the photodetector, a photodetector measurement output when the calibration element is in the reference state, and generating, by the controller, a calibration value based on the photodetector measurement output.
[0029] FIG. 5 shows a flowchart of a method 500 according to examples. In block 501 the here we can put the table with the states
[0030] The method 500 for calibrating a color measuring device comprising a radiation source and a photodetector, the method comprising.
[0031] In block 502 a calibration element controllable to provide a calibration reference state and an optically transparent state is provided, wherein the calibration element is in the field of view of a photodetector (i.e., the calibration surface is visible to the photodetector, at a distance from the photodetector such that the photodetector may make a photodetection measurement of the calibration surface).
[0032] In block 504, the controller may control the calibration element to provide a calibration reference state. Such controlling may comprise, for example, reducing the voltage applied to the calibration surface to a voltage below the minimum required for optical transparency (for example, 0V). In the case that the calibration surface is already subject to a voltage below the minimum voltage for optical transparency, controlling may comprise merely allowing the calibration surface to remain in that state.
[0033] In block 506 the photodetector may generate a photodetector measurement output when the calibration element is in calibration reference state. Thus, the photodetector may detect radiation reflected by the calibration element when the calibration element is in the calibration reference state and may generate a measurement output accordingly. In block 508 the controller may generate a calibration value based on the photodetector measurement output.
[0034] The calibration value generated at block 508 may be used to calibrate the color measuring device. The calibration value may be used to offset a measurement error or deviation of the color measuring device. In examples, the calibration value may be used to adjust electrical parameters such an amplifier gain, or a current level provided to the light source(s) (such as an LED light source). In examples, the calibration value may be used in the interpolation of measurement values during color measurement of a target. Alternatively or additionally, the calibration value may be stored in a memory/storage means of the controller for subsequent calibration of the color measuring device (or in a memory/storage means accessible by the controller).
[0035] After a calibration measurement is complete the calibration surface may be controlled to be in an optically transparent state for color measuring of a printed image. Such controlling may comprise, applying to the calibration surface, by the controller, a voltage equal to or greater than the minimum voltage necessary for the calibration surface to attain an optically transparent state.
[0036] In examples, a method for calibrating a color measuring device is provided, the method comprising providing a calibration element controllable to provide a calibration reference state and an optically transparent state, wherein the calibration element is in the field of view of the photodetector, irradiating, by the radiation source, the calibration element in the calibration reference state during a first time period, and not irradiating, by the radiation source, the calibration element in the calibration reference state during a second time period; generating, by the photodetector, a first photodetector measurement output in the first time period, and generating, by the photodetector, a second photodetector measurement output in the second time period; and generating, by the controller, a first calibration value based on the first photodetector measurement, and generating, by the controller, a second calibration value based on the second photodetector measurement.
[0037] FIG. 6 shows a flowchart of a method 600 according to examples.
[0038] In block 602, a calibration element controllable to provide a calibration reference state and an optically transparent state is provided in the field of view of a photodetector (i.e., the calibration element is visible to the photodetector, at a distance from the photodetector such that the photodetector may make a photodetection measurement of the calibration element).
[0039] In block 604, the controller controls the calibration element to be in a calibration reference state.
[0040] In block 606, the controller controls a radiation source to irradiate the calibration element during a first time period.
[0041] In block 608, a first photodetector measurement output is generated of the calibration element in the calibration reference state during the first time period (that is, when it is being irradiated by the radiation source). The first photodetector measurement occurs within the first time period but does not necessarily occur during the entire first time period. The first time period may range, for example, between 500 ms and 5000 ms. A photodetector measurement in the first time period, may be executed, for example, in 100 ms.
The first photodetector measurement is received by the controller and may be stored in a memory/storage means of the controller (or in a memory/storage means accessible by the controller).
[0042] In block 610, the controller controls the radiation source to not irradiate the calibration element in the calibration reference state during a second time period. For example, the controller may deactivate or turn off the radiation source or may merely allow the radiation source to remain in an OFF state if it is already inactive.
[0043] In block 612, the photodetector generates a second photodetector measurement output in the second time period. Thus, the second photodetector measurement output is generated when the calibration element is in a calibration reference state and the radiation source is not irradiating the calibration element). The second photodetector measurement occurs within the second time period but does not necessarily occur during the entire first time period. The second time period may range, for example, between 500 ms and 5000 ms. A photodetector measurement in the second time period, may be executed, for example, in 100 ms. The second photodetector measurement is received by the controller and may be stored in a memory of the controller (or in a memory accessible by the controller).
[0044] In block 614, the controller generates a first calibration value based on the first photodetector measurement output and generates a second calibration value based on the second photodetector measurement.
[0045] The sequence order of blocks 612 and 614 may be interchangeable.
[0046] The first calibration value may comprise or be used by the controller as a first or white reference calibration parameter value. The second calibration value may be used by the controller as a second or dark reference calibration parameter value.
[0047] The calibration values generated at block 612 may be used to calibrate the color measuring device. The calibration values may be used to
define a dynamic range of the color measuring device in the lighting conditions in which the first and second photodetector measurements were generated. The calibration values may be used to offset a measurement error or deviation of the color measuring device (for example, of the photodetector). In examples, the calibration values may be used to adjust electrical parameters such an amplifier gain, or a current level provided to the light source(s) (such as an LED light source). In examples, the calibration value may be used in the interpolation of photodetector measurement values during color measurement of a target. Alternatively or additionally, the calibration value may be stored in a memory of the controller for subsequent calibration of the color measuring device.
[0048] In examples, the color measuring device and calibration element may be provided in an enclosed housing or encapsulation such that external lighting is reduced. In this manner, a more controlled measurement that is more isolated from external factors may be obtained.
[0049] In examples, calibration of the color measuring device comprises obtaining a first calibration parameter value and a second calibration parameter value.
[0050] In examples, a dynamic range determination for calibration of the color measuring device comprises generating a first calibration parameter value and a second calibration parameter value, wherein the first calibration parameter value defines a white reference measurement (measured while the calibration element being irradiated by the radiation source) and the second calibration parameter input defines a dark reference measurement (measured while the calibration element is not being irradiated by the radiation source). The first and second calibration values described above may thus be used as the first and second calibration parameter values for determining a dynamic range of the color measuring device.
[0051] The first and second calibration parameter values represent the minimum and maximum measurement values that may be generated by the photodetector of the color measuring device. The calibration values may be
affected by the lighting conditions in which the color measuring device is being calibrated (which also includes any radiation/lighting originating from sources other than the radiation source of the color measuring device). In examples, the calibration values may be compared to a reference photodetector measurement threshold to detect a lighting leakage. The calibration values may also be affected by electrical noise.
[0052] In block 612, calibrating the color measuring device based on the first and second calibration values. In this manner, subsequent color measurements by the color measuring device may be adjusted, thereby reducing an associated measurement errors or deviations. Alternatively or additionally, the calibration values may be stored in a memory of the controller for use in a subsequent calibration or color measurement.
[0053] Table 1 below shows four different status combinations of various elements and the corresponding photodetector view.
[0054] Table 1
[0055] FIG. 7 is a schematic depiction of the controller 110 including a processor 111 and a non-transitory machine-readable storage medium 112 coupled to the processor. The processor 111 performs operations on data, for example, operations for calibrating the color measuring device 10 or spectrophotometer 402. The processor may also be a central processing unit for controlling the operation of a system, e.g. of a printing system.
[0056] The non-transitory machine-readable storage medium 112 is encoded with instructions 113 which, when executed by the processor 111, cause the processor 111 to adjust a calibration parameter of the color measuring device (for example, adjusting a calibration parameter using the calibration value(s) obtained via the systems, methods, or devices disclosed herein).
[0057] The non-transitory machine-readable storage medium 112 may include any electronic, magnetic, optical, or other physical storage device that stores executable instructions. The non-transitory machine-readable storage medium may be, for example, Random Access Memory (RAM), an Electrically- Erasable Programmable Read-Only Memory (EEPROM), a storage drive, an optical disk, and the like.
[0058] FIG. 8 is a block diagram of the instructions included in the non- transitory machine-readable storage medium of FIG. 7.
[0059] The non-transitory machine-readable storage medium 112 is encoded with instructions 113 which, when executed by the processor 111, cause the processor 111 to operate the controller to control a calibration surface to be in a calibration reference state at block 810; instruct a color measuring device to generate a sensor measurement output when the calibration element is in calibration reference state as represented at block 820; and generate a calibration value based on the sensor measurement output as represented at block 830. Alternatively or additionally, the instructions may comprise instructions to control a radiation source to irradiate the calibration element during a first time period at block 822; generate a first photodetector measurement output of the calibration element in the calibration reference state during the first time period at block 824; control the radiation source to not irradiate the calibration element in the calibration reference state during a second time period at block 826; generate a second photodetector measurement output in the second time period at block 828; and control the calibration surface to be in an optically transparent state for color measurement as represented at block 832.
[0060] The instructions encoded in the non-transitory machine-readable storage medium represented at blocks 810, 820, 822, 824, 826, 828, 830, and 832 may be executed in calibrating the color measuring device and/or in color measurement of a printed image according to any of the examples herein.
[0061] The processor 111 may control the calibration settings of the color measuring device.
[0062] In examples, the processor 111 may receive calibration settings to operate the color measuring device. In examples, calibration settings may be received from a user interface device or from a storage medium, e.g. from a look-up-table.
[0063] In addition, the processor 111 may control the operation of a carriage of a printing system, wherein a color measuring device is provided on the carriage. The operation of the carriage may be controlled (or displacement of the color measuring device along the carriage) may be controlled to position the color measuring device in a target position for calibration measurement or for color measurement.
[0064] The preceding description has been presented to illustrate and describe certain examples. Different sets of examples have been described; these may be applied individually or in combination, sometimes with a synergetic effect. This description is not intended to be exhaustive or to limit these principles to any precise form disclosed. Many modifications and variations are possible in light of the above teaching. It is to be understood that any feature described in relation to any one example may be used alone, or in combination with other features described, and may also be used in combination with any features of any other of the examples, or any combination of any other of the examples.
[0065] Although a number of particular implementations and examples have been disclosed herein, further variants and modifications of the disclosed devices and methods are possible. For example, not all the features disclosed
herein are included in all the implementations, and implementations comprising other combinations of the features described are also possible.
Claims
1. A system for calibrating a color measuring device, comprising: a color measuring device comprising a radiation source and a sensor; a calibration surface to change between a calibration reference state and an optically transparent state; and a controller to: control the calibration surface to be in a calibration reference state for a calibration measurement, control the radiation source and the sensor to generate a calibration value, and to control the calibration surface to be in an optically transparent state for color measurement of a printed image.
2. The system of claim 1 , wherein controlling the radiation source and sensor to generate a calibration value comprises: generating a first calibration value by controlling the radiation source to irradiate the calibration surface in the calibration reference state and sensing radiation by the sensor, and generating a second calibration value by controlling the radiation source to not irradiate the calibration surface in the calibration reference state and sensing radiation by the sensor.
3. The system of claim 1 or claim 2, wherein controlling the calibration surface to be in an optically transparent state for color measurement of a printed image comprises applying a voltage to the calibration surface above a minimum voltage threshold, and wherein controlling the calibration surface to be in a calibration reference state for calibration measurement comprises not applying a voltage across the calibration surface above a minimum voltage threshold.
4. The system of any of the preceding claims, wherein the calibration
surface comprises an electrochromic material.
5. The system of any of the preceding claims, wherein the calibration surface comprises polymer-dispersed liquid crystals.
6. The system of any of the preceding claims, wherein the sensor is a photosensor.
7. The system of any of the preceding claims, wherein the radiation source comprises a light source.
8. The system of claim 78, wherein the light source comprises a light emitting diode.
9. A printing device, comprising: a spectrophotometer for color measurement of a printed image output by the printing device; a spectrophotometer calibration element controllable to switch between a first optical state and a second optical state; and a controller to control the calibration element to switch to the first optical state for a calibration measurement, and to control the calibration element to switch to the second optical state for color measurement.
10. The printing device of claim 9, wherein the color measuring device and the calibration surface are on a carriage of the printing device.
11. A method for calibrating a color measuring device comprising a radiation source and a photodetector, the method comprising: providing a calibration element controllable to provide a calibration reference state and an optically transparent state, wherein the calibration element is in the field of view of the photodetector; controlling, by a controller, the calibration element to provide the
calibration reference state; generating, by the photodetector, a photodetector measurement output when the calibration element is in the reference state, and generating, by the controller, a calibration value based on the photodetector measurement output.
12. The method of claim 11, comprising irradiating, by the radiation source, the calibration element in the calibration reference state during a first time period, and not irradiating, by the radiation source, the calibration element in the calibration reference state during a second time period; and wherein generating a photodetector measurement output when the calibration element is in the calibration reference state comprises generating, by the photodetector, a first photodetector measurement output in the first time period, and generating, by the photodetector, a second photodetector measurement output in the second time period; and wherein generating, by the controller, a calibration value based on the photodetector measurement output comprises generating, by the controller, a first calibration value based on the first photodetector measurement, and generating, by the controller, a second calibration value based on the second photodetector measurement.
13. The method of claim 11 or claim 12, wherein the calibration element comprises an electrochromic material.
14. The method of any of claims 11 to 13, wherein the calibration element comprises polymer-dispersed liquid crystals.
15. The method of any of claims 11 to 14, wherein controlling the calibration element to provide an optically transparent state comprises
applying a voltage above a minimum voltage threshold across the calibration element.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| PCT/US2021/040299 WO2023277924A1 (en) | 2021-07-02 | 2021-07-02 | Systems, methods, and devices for calibration of color measuring devices |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| PCT/US2021/040299 WO2023277924A1 (en) | 2021-07-02 | 2021-07-02 | Systems, methods, and devices for calibration of color measuring devices |
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| Publication Number | Publication Date |
|---|---|
| WO2023277924A1 true WO2023277924A1 (en) | 2023-01-05 |
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| PCT/US2021/040299 WO2023277924A1 (en) | 2021-07-02 | 2021-07-02 | Systems, methods, and devices for calibration of color measuring devices |
Country Status (1)
| Country | Link |
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| WO (1) | WO2023277924A1 (en) |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5508826A (en) * | 1993-04-27 | 1996-04-16 | Lloyd; William J. | Method and apparatus for calibrated digital printing using a four by four transformation matrix |
| US20150009500A1 (en) * | 2013-07-08 | 2015-01-08 | Mattel, Inc. | Colorimeter calibration system and methods |
| WO2019172919A1 (en) * | 2018-03-08 | 2019-09-12 | Hewlett-Packard Development Company, L.P. | Printer calibration |
-
2021
- 2021-07-02 WO PCT/US2021/040299 patent/WO2023277924A1/en unknown
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5508826A (en) * | 1993-04-27 | 1996-04-16 | Lloyd; William J. | Method and apparatus for calibrated digital printing using a four by four transformation matrix |
| US20150009500A1 (en) * | 2013-07-08 | 2015-01-08 | Mattel, Inc. | Colorimeter calibration system and methods |
| WO2019172919A1 (en) * | 2018-03-08 | 2019-09-12 | Hewlett-Packard Development Company, L.P. | Printer calibration |
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