JP2021027340A - Output control device, laser output device, image recording device, output control method, and output control program - Google Patents

Abstract

To enable prevention of variations in output between elements in an output control device having at least one output element.SOLUTION: An output control device 140 has a plurality of laser light emitting elements 41, and a control unit 46 that switches on/off of energization to the laser light emitting elements 41 to control output from the laser light emitting elements 41. When an energization time t0 and an energization stop time toff of a current flowing through the laser light emitting elements 41 are determined according to desired output from the laser light emitting elements 41, the control unit 46 determines an energization time correction value Δt by using a correction function β(toff) individually set to each of the plurality of laser light emitting element 41, and corrects the energization time and the energization stop time based on the energization time correction value Δt.SELECTED DRAWING: Figure 10

Description

The present invention relates to an output control device, a laser output device, an image recording device, an output control method, and an output control program.

Conventionally, a laser device has been developed that can turn on a light emitting element (laser diode, VCSEL, etc.), irradiate the irradiation target with laser light through an optical system, and bring about state changes such as color development, melting, and surface modification by thermal energy. Has been done.

In such a laser device, a switching type current drive is adopted as a method for improving the efficiency of the drive circuit of the light emitting element. In order to drive and control a diode load such as a laser diode, the optical output is usually controlled by current drive.

In order to improve the efficiency of current drive, after chopping the input voltage with a switching element, the current flowing through a smoothing element such as a coil is fed back to be constant, and a pulse that switches the current application direction according to the laser irradiation timing. A current drive control method is already known (see, for example, Patent Document 1).

In this switching method pulse current drive control method, there is a problem that the output variation due to the current ripple is large.

An object of the present invention is to make it possible to suppress variations in output between each element in an output control device having at least one output element.

In order to solve the above-mentioned problems, the output control device according to one aspect of the present invention includes at least one output element and a control unit that controls the output of the output element by switching the energization of the output element on and off. The control unit is individually set for each of the at least one output element when the energization time and energization stop time of the current flowing through the output element are determined according to the desired output of the output element. The energization time correction value is obtained using a correction function, and the energization time and the energization stop time are corrected based on the energization time correction value.

In an output control device having at least one output element, it is possible to suppress variations in output between the elements.

Schematic perspective view of an image recording system as an image recording device according to an embodiment. Schematic perspective view showing the configuration of the recording device according to the embodiment. A block diagram showing a part of an electric circuit of an image recording system according to an embodiment. Block diagram of the recording device of the electric circuit shown in FIG. A block diagram illustrating a driver of the electric circuit shown in FIG. The figure explaining the correction method of the output energy of a laser emitting element by a control unit. The figure explaining the correction method of the output energy of a laser emitting element by a control unit. The figure explaining the correction method of the output energy of a laser emitting element by a control unit. The figure explaining the method of acquiring the correction energy characteristic for each light source The figure explaining the method of acquiring the correction energy characteristic for each light source The figure which shows an example of the characteristic of the correction function when the current value is variable Flowchart of correction function calculation process A flowchart showing the operation of the driver of the electric circuit shown in FIG. Hardware configuration diagram of the control unit

Hereinafter, embodiments will be described with reference to the accompanying drawings. In order to facilitate understanding of the description, the same components are designated by the same reference numerals as much as possible in each drawing, and duplicate description is omitted.

Hereinafter, as an example, a structure having a heat-sensitive recording unit as a recording object, specifically, an image recording device for recording an image in a container for transportation to which a heat-sensitive recording label is attached will be described.

In the present embodiment, "recording" refers to a logo, a product name, a serial number, or the like by irradiating a recording object with light such as a laser to melt, burn, peel, oxidize, scrape, or discolor the surface. It means to print the model number and so on. It can also be expressed as so-called "non-contact marking", "laser marking", "laser printing", or "laser printing".

FIG. 1 is a schematic perspective view of an image recording system 100 as an image recording device according to an embodiment. In the following description, the transport direction of the transport container C will be described as the X-axis direction, the vertical direction will be described as the Z-axis direction, and the direction orthogonal to both the transport direction and the vertical direction will be described as the Y-axis direction. As described in detail below, the image recording system 100 records an image by irradiating a heat-sensitive recording label RL attached to a container C for transportation, which is a recording object, with laser light. As shown in FIG. 3A, the image recording system 100 includes a conveyor device 10, a recording device 14, a system control device 18, a reading device 15, a shielding cover 11, and the like, which are means for transporting recording objects.

The recording device 14 irradiates the thermal recording label RL with a laser beam to record an image as a visible image on a recording object. The recording device 14 is arranged on the −Y side of the conveyor device 10, that is, on the −Y side of the transport path.

The shielding cover 11 shields the laser light emitted from the recording device 14 to reduce the diffusion of the laser light, and the surface thereof is coated with black alumite. An opening 11a for passing laser light is provided in a portion of the shielding cover 11 facing the recording device 14. Further, in the present embodiment, the conveyor device 10 is a roller conveyor, but may be a belt conveyor.

The system control device 18 is connected to a conveyor device 10, a recording device 14, a reading device 15, and the like, and controls the entire image recording system 100. Further, as will be described later, the reading device 15 reads a code image such as a barcode or a QR code (registered trademark) recorded on a recording object. The system control device 18 collates whether or not the image is correctly recorded based on the information read by the reading device 15.

FIG. 2 is a schematic perspective view showing the configuration of the recording device 14 according to the embodiment. In the present embodiment, as the recording device 14, the laser emitting portions of a plurality of optical fibers are set in the main scanning direction (Z-axis direction) orthogonal to the sub-scanning direction (X-axis direction) which is the moving direction of the container C as the recording object. A fiber array recording device that records images using a fiber array arranged in an array is used. The fiber array recording device irradiates a recording object with a laser beam emitted from a laser emitting element via the fiber array, and records an image composed of drawing units. Specifically, the recording device 14 includes a laser array unit 14a, a fiber array unit 14b, and an optical unit 43. The laser array unit 14a is provided corresponding to a plurality of laser light emitting elements 41 (output elements) arranged in an array, a cooling unit 50 for cooling the laser light emitting element 41, and the laser light emitting element 41, and corresponds to the laser. A plurality of drive drivers 45 for driving the light emitting element 41 and a controller 46 for controlling the plurality of drive drivers 45 are provided. The controller 46 is connected to a power supply 48 for supplying electric power to the laser emitting element 41 and an image information output unit 47 such as a personal computer that outputs image information. Hereinafter, the “controller 46” may also be referred to as a “control unit 46”.

The laser emitting element 41 can be appropriately selected depending on the intended purpose, and for example, a semiconductor laser, a solid-state laser, a dye laser, or the like can be used. Among these, the laser emitting element 41 is preferably a semiconductor laser from the viewpoints of wide wavelength selectivity, small size of the apparatus, and low cost.

The wavelength of the laser light emitted by the laser light emitting element 41 is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 700 nm to 2000 nm, more preferably 780 nm to 1600 nm.

In the laser emitting element 41 which is an emitting means, not all of the applied energy is converted into laser light. Normally, in the laser light emitting element 41, energy that is not converted into laser light is converted into heat to generate heat. Therefore, the laser emitting element 41 is cooled by the cooling unit 50 which is a cooling means. Further, in the present embodiment, the recording device 14 can be arranged with the laser emitting elements 41 separated from each other by using the fiber array unit 14b. As a result, the influence of heat from the adjacent laser emitting element 41 can be reduced, and the laser emitting element 41 can be cooled efficiently, so that the temperature rise and variation of the laser emitting element 41 can be avoided. It is possible to reduce the output variation of the laser beam and improve the density unevenness and the white spot.

The output of the laser beam is the average output measured by the power meter. There are two types of laser light output control methods, one is to control the peak power [and] and the other is to control the pulse emission ratio (duty: laser emission time / cycle time).

The cooling unit 50 is a liquid cooling system that circulates a cooling liquid to cool the laser emitting element 41, and has a heat receiving unit 51 in which the cooling liquid receives heat from each laser emitting element 41 and a heat radiating unit that dissipates heat from the coolant. It has 52 and. The heat receiving unit 51 and the heat radiating unit 52 are connected by cooling pipes 53a and 53b. The heat receiving portion 51 is provided with a cooling pipe for flowing the cooling liquid formed of the good thermal conductive member inside the case formed of the good thermal conductive member. The plurality of laser light emitting elements 41 are arranged in an array on the heat receiving unit 51.

The heat radiating unit 52 includes a radiator and a pump for circulating the coolant. The cooling liquid sent out by the pump of the heat radiating unit 52 flows into the heat receiving unit 51 through the cooling pipe 53a. Then, while moving the cooling tube in the heat receiving unit 51, the heat of the laser emitting elements 41 arranged in the heat receiving unit 51 is taken away to cool the laser emitting element 41. The cooling liquid that has taken the heat of the laser light emitting element 41 flowing out from the heat receiving unit 51 and whose temperature has risen moves in the cooling pipe 53b, flows into the radiator of the heat radiating unit 52, and is cooled by the radiator. The coolant cooled by the radiator is pumped again to the heat receiving unit 51.

The fiber array portion 14b includes a plurality of optical fibers 42 provided corresponding to the laser light emitting element 41, and an array head 44 that holds the vicinity of the laser emitting portion of these optical fibers 42 in an array in the vertical direction (Z-axis direction). It has. The laser incident portion of each optical fiber 42 is attached to the laser emitting surface of the corresponding laser emitting element 41.

The image information output unit 47 of a personal computer or the like inputs image data to the controller 46. The controller 46 generates a drive signal for driving each drive driver 45 based on the input image data. The controller 46 transmits the generated drive signal to each drive driver 45. Specifically, the controller 46 includes a clock generator. When the number of clocks oscillated by the clock generator reaches the specified number of clocks, the controller 46 transmits a drive signal for driving each drive driver 45 to each drive driver 45.

Upon receiving the drive signal, each drive driver 45 drives the corresponding laser light emitting element 41. The laser light emitting element 41 irradiates the laser light according to the drive of the drive driver 45. The laser light emitted from the laser emitting element 41 enters the corresponding optical fiber 42 and is emitted from the laser emitting portion of the optical fiber 42. The laser light emitted from the laser emitting portion of the optical fiber 42 passes through the collimating lens 43a and the condensing lens 43b of the optical portion 43, and then irradiates the surface of the heat-sensitive recording label RL of the container C, which is a recording object. An image is recorded on the surface of the thermal recording label RL by being heated by a laser beam irradiating the surface of the thermal recording label RL.

When a galvano mirror is used as a recording device to deflect a laser and record an image on a recording object, images such as characters are irradiated with laser light as if they were drawn with a single stroke by rotating the galvano mirror. And record. Therefore, when recording a certain amount of information on a recording object, there is a problem that the recording cannot be made in time unless the transportation of the recording object is stopped. On the other hand, by using a laser array in which a plurality of laser emitting elements 41 are arranged in an array like the recording device 14 of the present embodiment, the recording object can be controlled by ON / OFF control of the laser emitting elements 41 corresponding to each pixel. Images can be recorded on the laser. As a result, even if the amount of information is large, the image can be recorded on the recording object without stopping the transportation of the container C. Therefore, according to the recording device 14 of the present embodiment, even when a large amount of information is recorded on the recording object, the image can be recorded without reducing the productivity.

FIG. 3 is a block diagram showing a part of an electric circuit in the image recording system 100 according to the embodiment. In the figure, the system control device 18 includes a CPU, RAM, ROM, non-volatile memory, etc. (not shown), and controls the drive of various devices in the image recording system 100 and performs various arithmetic processes. It is a thing. A conveyor device 10, a recording device 14, a reading device 15, an operation panel 181 and an image information output unit 47 are connected to the system control device 18.

The operation panel 181 is provided with a touch panel display and various keys, and displays an image on a display and receives various information input by a key operation of an operator.

As shown in FIG. 3, the system control device 18 functions as an image recording means by operating the CPU according to a program stored in a ROM or the like. The system control device 18 that functions as an image recording means controls the recording device 14 and irradiates a recording object that moves relative to the recording device 14 in a direction different from a predetermined direction to record the recording target. An object is heated to form image dots and an image is recorded.

Next, an example of the operation of the image recording system 100 will be described with reference to FIG. First, the container C in which the luggage is housed is placed on the conveyor device 10 by the operator. The operator places the container C on the conveyor device 10 so that the side surface of the main body of the container C to which the thermal recording label RL is affixed is located on the −Y side, that is, the side surface faces the recording device 14. To do.

When the operator operates the operation panel 181 to start the system control device 18, the transfer start signal is transmitted from the operation panel 181 to the system control device 18. Upon receiving the transfer start signal, the system control device 18 starts driving the conveyor device 10. Then, the container C placed on the conveyor device 10 is conveyed toward the recording device 14 by the conveyor device 10. As an example of the transport speed of the container C, it is 2 m / sec.

A sensor for detecting the container C transported on the conveyor device 10 is arranged on the upstream side of the recording device 14 in the transport direction of the container C. When this sensor detects the container C, a detection signal is transmitted from the sensor to the system control device 18. The system control device 18 has a timer. The system control device 18 starts time measurement using a timer at the timing when the detection signal from the sensor is received. Then, the system control device 18 grasps the timing at which the container C reaches the recording device 14 based on the elapsed time from the reception timing of the detection signal.

When the elapsed time from the reception timing of the detection signal becomes T1 and the container C reaches the recording device 14, the system control device 18 displays an image on the heat-sensitive recording label RL affixed to the container C passing through the recording device 14. A recording start signal is output to the recording device 14 in order to record.

The recording device 14 that has received the recording start signal emits a laser beam of a predetermined power toward the heat-sensitive recording label RL of the container C that moves relative to the recording device 14 based on the image information received from the image information output unit 47. Irradiate. As a result, the image is recorded on the thermal recording label RL in a non-contact manner.

The image recorded on the heat-sensitive recording label RL (image information transmitted from the image information output unit 47) includes, for example, a character image such as the contents of the package contained in the container C, information on the transportation destination, and the container. It is a code image such as a bar code or a two-dimensional code in which information such as the contents of luggage stored in C and information on a transportation destination is coded.

The container C in which an image is recorded in the process of passing through the recording device 14 passes through the reading device 15. At this time, the reading device 15 reads a code image such as a barcode or a two-dimensional code recorded on the thermal recording label RL, and acquires information such as the contents of the package contained in the container C and the transportation destination information. To do. The system control device 18 collates the information acquired from the code image with the image information transmitted from the image information output unit 47, and checks whether or not the image is correctly recorded. When the image is correctly recorded, the system control device 18 sends the container C to the next step (for example, a transportation preparation step) by the conveyor device 10.

On the other hand, when the image is not correctly recorded, the system control device 18 temporarily stops the conveyor device 10 and displays on the operation panel 181 that the image is not correctly recorded. Further, the system control device 18 may transport the container C to a specified transport destination when the image is not correctly recorded.

FIG. 4 is a block diagram relating to the recording device 14 of the electric circuit shown in FIG. An I / F unit 180 is provided between the system control device 18 and the control unit 46.

The image information output unit 47 transmits information on the light energy required to output a desired dot density to the system control device 18. The system control device 18 transmits control signals such as timing, pulse width, and peak power as information on necessary light energy to the control unit 46 via the I / F unit 180, and a status signal via the I / F unit 180. Is received from the control unit 46.

In principle, the driver 45 of the recording device 14 may be a high-efficiency switching system, a low-efficiency linear system, or the like, but the driver system is not particularly limited as long as it can output a pulse in the present embodiment.

FIG. 5 is a block diagram illustrating the driver 45 of the electric circuit shown in FIG.

The driver 45 includes a current drive circuit 480, and the control signal 450 is sent from the control unit 46 to supply the output current 480S to the drive target connected to the output unit 454.

Although the laser emitting element 41 is connected to the output unit 454, an LED may be connected as another form.

In FIG. 5, in order to perform pulse modulation at high speed, a light emission control unit 455 (switch unit) that controls light emission / non-light emission of the laser light emitting element 41 is output by switching the current path flowing through the laser light emitting element 41 as a light emitting element. It is connected to the unit 454 in parallel. The light emission control unit 455 is composed of a switching element such as a MOSFET.

The current modulation speed of the drive current by the light emission control unit 455 is high because it depends on the switch time of the switching element of the light emission control unit 455 (several tens of ns in the case of MOSFET).

The current drive circuit 480 has a function of monitoring the current flowing through the light emission control unit 455 and the drive target connected to the output unit 454, and can also send the feedback signal 460 to the control unit 46.

The control unit 46 sends a PWM control signal 455S as a switching signal (light emission information) for turning on / off the light emission control unit 455 to the light emission control unit 455. When the pulse frequency is 40 kHz (1 cycle = 25 us) and the recording device 14 has 256 gradations, one pixel corresponds to a pulse width of about 0.1 us (≈100 ns). If a pulse with a duty of 50% (128 gradations) is output, the pulse width will be about 12.8 us.

The control unit 46 has a correction information database 470 in which correction information (correction function β described later) corresponding to the modulation characteristics of the plurality of laser light emitting elements 41 is stored. The correction information database 470 is created and held in advance by the control unit 46 based on the input / output information acquired from the laser light emitting element 41 before using the output device.

In the present embodiment, by sending a PWM control signal 455S in consideration of the correction information database 470 to each light emission control unit 455 that controls a plurality of laser light emitting elements 41, a main scan orthogonal to the moving direction of the recording object is performed. It suppresses the energy variation of the pulse generated in the direction (arrangement direction of the laser emitting element).

The driver 45 and the control unit 46 described above constitute an output control device 140 that controls an output current 480S, which is a current supplied to the output unit 454. Further, the laser output device is configured by connecting the laser light emitting element 41 to the output control device 140.

As described above, particularly in the present embodiment, the control unit 46 individually corrects the PWM control signals to each of the plurality of laser light emitting elements 41 according to the characteristics of each element, whereby the plurality of laser light emitting elements 41 It is configured so that the output can be made uniform. This correction process will be described below.

6A, 6B, and 6C are diagrams for explaining a method of correcting the output energy of the laser emitting element 41 by the control unit 46.

FIG. 6A shows an example 500 of the waveform of the current flowing through the light emitting element 41, and FIG. 6B shows the waveform 510 of the output power of the light emitting element 41 based on the current waveform 500. In the power waveform 510, the target output is shown by a dotted line, and the actual output is shown by a solid line. FIG. 6A shows a current waveform 520 in which the energization stop time is relatively long with respect to the current waveform 500, and FIG. 6D shows a waveform 530 of the output power of the light emitting element 41 based on the current waveform 520. In (b) and (d), the target output is shown by a dotted line, and the actual output is shown by a solid line.

When the PWM control signal 455S is sent to the light emission control unit 455 of FIG. 5, the temporal change of the current 41S flowing through the light emitting element 41 becomes like the current waveform 500 of FIG. 6A (a) and is formed. Between the pulse waveforms having a time width of t0, an energization stop time t1 in which no current flows occurs.

At this time, the temporal change of the optical power output from the light emitting element 41 is ideally close to a rectangle as shown in the output waveform 510, as shown in FIG. 6A (b). Let one output energy of this output waveform 510 be E1.

Here, considering the case where the energization time remains t0 and the energization stop time is t2 longer than t1, the current waveform 520 is as shown in FIG. 6A (c) (t1 <t2). ).

At this time, as shown in FIG. 6A (d), the temporal change of the output power of the light emitting element 41 may have a blunt rise as shown in the output waveform 530, and the output energy may be E2 smaller than E1.

This is a phenomenon particularly observed in laser light emitting elements of several watts to several tens of watts class. In many cases, the optical system of such a laser emitting element is adjusted on the premise of emitting light under CW (continuous wave) conditions, so that the radiation pattern and the temperature of the optical system when PWM is performed change with time. It is considered that the longer the energization stop time, the easier the coupling efficiency decreases.

FIG. 6B (e) shows the characteristic 540 of the optical system temperature and the energization stop time toff, and (f) shows the characteristic 550 of the coupling efficiency estimated from the characteristic 540 and the energization stop time toff. Further, (g) of FIG. 6B shows the characteristic 560 of the output energy estimated from the characteristic 550 and the energization stop time, and (h) shows the characteristic 570 of the correction energy estimated from the characteristic 560 and the energization stop time. Is shown. In FIGS. 6B (e) to 6B, the energization stop times t1 and t2 shown in FIG. 6A are shown (t1 <t2), respectively.

If the energization stop time is lengthened while the energization time is t0 using this light source, one pulse waveform having the energization time t0 is affected by the coupling efficiency characteristics as shown in the graph 550 shown in FIG. 6B (f). The per-output energy is considered to decrease monotonically as shown in the graph 560 shown in FIG. 6B (g) (t1 <t2, E2 <E1). That is, even if the energization time is the same, this light source has a characteristic that the energy per output waveform actually output changes depending on the energization stop time, which makes control difficult.

In order to prevent this, the energy per output waveform for a certain energization time may be corrected so as to be constant regardless of the energization stop time. For example, if it is known that the coupling efficiency of a certain light source has the characteristics shown in Graph 550 shown in FIG. 6B (f), the corrected energy characteristics for the energization stop time (graph shown in FIG. 6B (h)) are compensated for. 570) can be set. In the graph 570 shown in FIG. 6B (h), it is shown that ΔE1 is added when the energization stop time is toff = t1 and ΔE2 is added when toff = t2 (t1 <t2, ΔE1 <ΔE2).

An example of applying this correction method to the current waveform 500 is the current waveform 501 shown in FIG. 6C (i). Assuming that the voltage between the terminals of the light emitting element 41 is constant and V1, the added current pulse width can be calculated by the following equation (1).
Δt1 = ΔE1 / (I1 × V1) ・ ・ ・ (1)

As a result, as shown in FIG. 6C (j), in the output waveform 511, the output energy of one pulse waveform becomes E1 + ΔE1.

Similarly, when the correction means is applied to the current waveform 520, the current waveform 521 shown in FIG. 6C (k) is obtained. Assuming that the voltage between the terminals of the light emitting element 41 is a constant value V1, the current pulse width to be added can be calculated by the following equation (2).
Δt2 = ΔE2 / (I1 × V1) ・ ・ ・ (2)

As a result, in the output waveform 531 as shown in FIG. 6C (l), the output energy of one pulse waveform becomes E2 + ΔE2.

If the corrected energy characteristics (graph 570 in FIG. 6B (h)) are based on the coupling efficiency characteristics of the light source, the energies per output waveform of the output waveforms 511 and 513 are equal, and E1 + ΔE1 = E2 + ΔE2.

In the current waveforms 500, 520, 501, and 521, the current value was set to a constant I1, but even when this is an arbitrary function I (t), the voltage between the terminals of the light emitting element 41 is set to a constant value V1 and the pulse width. Assuming that the correction start time is t0, Δt1 satisfying the following equation (3) may be obtained. The same applies to ΔE2.

The means up to this point are performed for one light source, but since it is used as a fiber array in an actual device, there are a plurality of light sources. When PWM is performed with these light sources, the optical system temperature (graph 540 in FIG. 6B (e)) and the coupling efficiency characteristic (graph 550 in FIG. 6B (f)) with respect to the energization stop time do not always match. It is likely to vary depending on the light source.

When an image is recorded using such a fiber array, even if a current waveform having the same pulse width is input to each light source, the energy of each output waveform varies, so that the image becomes uneven.

Therefore, when a laser emitting element is used, the corrected energy characteristic (FIG. 6B) based on the optical system temperature (graph 540 in FIG. 6B (e)) and the coupling efficiency characteristic (graph 550 in FIG. 6B (f)) for each light source. Graph 570) of (h) is required. Hereinafter, this characteristic acquisition method will be described with reference to FIGS. 7A and 7B.

7A and 7B are diagrams for explaining a method of acquiring the correction energy characteristic 570 for each light source.

It is difficult and time-consuming to directly acquire the optical system temperature (graph 540 in FIG. 6B (e)) and the coupling efficiency characteristic (graph 550 in FIG. 6B (f)) of the plurality of light sources of the laser emitting element, so it is easy. A method of obtaining the corrected energy characteristic (graph 570 of FIG. 6B (h)) will be described.

Waveforms 600, 620, 640, 660, and 680 shown in FIGS. 7A (a), (c), (e), (g), and (i) are current waveforms passed through a certain light emitting element 41, and all of them are current waveforms. The energization and stop are repeated, and the energization stop time is t0, but the energization stop time is different from toff = t1 to t5 (t1 <t2 <t3 <t4 <t5).

At this time, the temporal changes in the optical power output from the light emitting element 41 are the output waveforms 610, 630, and 650 shown in FIGS. 7A (b), (d), (f), (h), and (j), respectively. , 670, 690.

FIG. 7B (k) shows the characteristic 700 between the output energy based on the five types of input / output of FIG. 7A and the energization stop time tof. As shown in FIGS. 7A to 7A, as the energization stop time becomes longer, the rising edge of the output waveform becomes dull and the peak decreases. Therefore, as shown in Graph 700, the energy per output waveform is energized. It decreases as the downtime increases. E1 to E5 in FIG. 7B (k) correspond to the output energies of toff = t1 to t5 (E1 <E2 <E3 <E4 <E5).

In order to reduce the variation of these energies, the correction energy may be added to E1 to E5 to make the output energy uniform. FIG. 7B (l) shows the characteristic 710 between the correction energy and the energization stop time toff based on the graph 700. The characteristic 710 shows the correction energies ΔE1 to ΔE5 corresponding to E1 to E5.

By adding the correction energy to the output energy, E1 + ΔE1 = E2 + ΔE2 = E3 + ΔE3 = E4 + ΔE4 = E5 + ΔE5 = Ec. Since the value of Ec can be set arbitrarily, the intercept of the characteristic of the graph 710 does not have to be 0.

Here, as an example, t0 = 12.5us, t1 = 50us, t2 = 37.5us, t3 = 25us, t4 = 12.5us, t5 = 6.25us, the current I = 10A flowing through the light emitting element 41, and the output voltage V. Consider the case where = 4V and power-optical conversion efficiency η = 50%.

The power per unit time output from the light emitting element 41 is 10A x 4V x 50% = 20W, and the energizing time is t0 = 12.5us, so the target energy of the output waveform per unit is 20W x 12.5us = 250uJ. It becomes. The energy per actual output waveform differs depending on the energization stop time. For example, when E1 = 235uJ, E2 = 217.5uJ, E3 = 207.5uJ, E4 = 202.5uJ, E5 = 200uJ, (1) in FIG. 7B. The graph 720 shown in m) is shown. By approximating (t1, E1) to (t5, E5) on the graph 720 with a polynomial, a fluctuation function α (toff) with the energization stop time toff as a variable can be obtained.

The variable function α (toff) is a polynomial such as a linear function, a quadratic function, or a cubic function. When the graph 720 of FIG. 7B (m) is approximated by a cubic equation, the following equation (4) is used. Can be represented (unit is uJ).
α (toff) = a × toff ³ + b × toff ² + c × toff +250 ・ ・ ・ (4)

Since the target energy is 250uJ, the intercept is set to 250uJ, but the section is not limited to this.

If the fluctuation function α (toff) is obtained, the correction function β (toff) for setting the correction energy for suppressing the energy variation can also be calculated. The correction function β (toff) can be derived from the following equation (5) by subtracting the fluctuation function α (toff) from the target energy Ec, for example.
β (toff) = Ec-α (toff) ・ ・ ・ (5)

The correction function β can also be derived by other methods. A easily conceivable method is to move the fluctuation function α (toff) symmetrically with respect to the horizontal axis (energization stop time axis) and set the intercept to 0. That is, when the fluctuation function is the equation (4), the correction function is the following equation (6).
β (toff) =-(a × toff ³ + b × toff ² + c × toff) ・ ・ ・ (6)

Correction energy for waveforms 600, 620, 640, 660, 680 shown in FIGS. 7A (a), (c), (e), (g), and (i) using the equation (5) or (6), respectively. ΔE1 to ΔE5 can be obtained. At this time, the intercept does not necessarily have to be 0. At this time, the correction function β (toff) is as shown in the graph 730 shown in FIG. 7B (n).

In order to obtain the correction function β (toff), energy per output waveform for a plurality of energization stop times is required for a certain energization time t0, but the maximum value of the energization stop time for acquiring the function is actually. It is preferable that the pixel period used in the above device is exceeded because the accuracy is high. For example, if the light source is driven at a pixel frequency of 40 kHz, the period of one pixel is 25 us, so the correction function β (toff) approximated in the range of the energization stop time t1 = 50 us as shown in Graph 730 can be sufficiently used.

In addition, the number of energization stop times for acquiring the correction function was set to 5 in the examples of FIGS. 7A and 7B, but if accuracy is important, it may be larger, and the correction function acquisition can be completed in a short time. If you want, you can use less.

The energy of the output waveform per unit is a photo diode (light output from the light emitting element 41 is made parallel by a collimating lens, dimmed by an ND filter, or condensed by a condensing lens. It is possible to obtain it from the optical waveform after incident and voltage conversion to the light detection unit of PD), but in the case of multiple light sources such as a fiber array, it takes cost and time to adjust the optical system of the multiple light sources.

Therefore, if an optical power meter or a thermal sensor having a large area of the photodetector is used, the light energy output from a plurality of light sources can be obtained without precise adjustment of the optical system. It is desirable to have a system in which light from all the light sources used can be input to the photodetector without adjusting the optical axis. However, since the optical power meter and the thermal sensor detect the time average (power) of the incident light energy, in order to measure the energy of the output waveform per one, the detected power may be divided by the duty ratio. In this way, the energy per unit time of each output waveform can be obtained, and the comparison as shown in Graph 720 becomes possible depending on the energization stop time.

Up to this point, the method of correcting the energy variation of the output waveform per light source due to the energization stop time has been described for a certain light source, but in a light emitting element having multiple light sources such as a fiber array, when PWM is performed. Since the characteristics of the optical system temperature (graph 540) and the coupling efficiency (graph 550) differ depending on the light source, there is an optimum fluctuation function α (toff) and correction function β (toff) for each light source. Therefore, if there are N light sources, the correction functions β1 (toff) to βN (toff) may be obtained by the methods described so far.

As a result, the energy variation of the pulse generated in the main scanning direction (arrangement direction of the laser emitting element) orthogonal to the moving direction of the recording object can be suppressed, so that the density variation and density unevenness of the image, the accuracy deterioration of the three-dimensional object, and the processing defect can be suppressed. Is improved.

However, it is not always necessary to acquire the correction function β (toff) for all the light sources, and the number may be less than the number of light sources.

Although the current value flowing through the light emitting element 41 is set to 10A this time as an example, the correction function β (toff) may change depending on this set value. FIG. 8 is a diagram showing an example of the characteristics of the correction function when the current value is variable. The vertical axis and the horizontal axis of FIG. 8 are the same as those of FIG. 7B (n).

The apparatus used in this embodiment is basically assumed to perform pulse width modulation with a fixed current value. If the current value is also modulated, it is necessary to acquire a plurality of correction functions β (toff) corresponding to each current value as shown in the graph 740 shown in FIG.

Here, the polynomial γ (I) with the current value as a variable may be multiplied by Eq. (6) to obtain the correction function in Eq. (7) below.
β (toff) =-(a × toff ³ + b × toff ² + c × toff) × γ (I)
... (7)

Further, the polynomial A (t0) with the energization time t0 as a variable may be multiplied by the equation (7) to obtain the correction function in the following equation (8).
β (toff) =-(a × toff ³ + b × toff ² + c × toff) × γ (I) × A (t0)
... (8)

Next, the output control method according to the present embodiment will be described with reference to FIGS. 9 and 10. FIG. 9 is a flowchart of the calculation process of the correction function β (toff). Each process of the flowchart of FIG. 9 is performed in advance, for example, every predetermined number of operations before the laser output operation is performed by the control unit 46.

This flowchart is executed before the image recording device of FIG. 1 records an image on the recording object, and a system for receiving the laser beam emitted from the light emitting element 41 of FIG. 4 is provided, and FIG. It is premised that the correction function β (toff) is calculated as the correction information database 470 stored in the control unit 46 of the above. The control unit 46 selects an arbitrary light source from the light emitting element 41 (step S1), sets the current value I (step S2) to be passed through the light source, the energization time t0 (step S3), and the energization stop time toff (step S4). It is set and light is output from the light emitting element 41 (step S5).

The light detection method differs depending on whether the actual light waveform is output or the average power is detected (step S6).

In the method of outputting the actual optical waveform, that is, when it is incident on the photodetector of the photodiode (PD) (step S7), the current flowing through the PD is voltage-converted (step S8), and the time of the output waveform of an oscilloscope or the like is obtained. The energy of one output waveform is calculated by displaying the change in the object (step S9).

In the method of detecting the average power, that is, when the light is incident on the photodetector of an optical power meter or a thermal sensor (step S10), the detected power is divided by the duty ratio to calculate the energy of one output waveform per unit time. (Step S11).

From the results so far, the energy of one output waveform for one energization stop time toff can be obtained, but if the required number of data points is not available (NO in step S12), the process returns to step S4 and the energy acquisition is repeated.

On the other hand, when a sufficient number of data points are obtained (YES in step S12), the target energy Ec per output waveform is calculated (step S13)), and the energy fluctuation function α (toff) is calculated by polynomial approximation (YES in step S12). Step S14).

The energy correction function β (toff) is calculated based on the energy fluctuation function α (toff) (step S15). For example, the energy correction function β (toff) can be calculated by subtracting the energy fluctuation function α (toff) from the target energy Ec using the equation (5).

If the number of the calculated correction functions β (toff) is not sufficient (NO in step S16), the process returns to step S1, and another light source is selected from the light emitting element 41 to proceed with the process. On the other hand, when the calculated number of correction functions β (toff) is sufficiently complete (YES in step S16), it means that the correction function β to be stored in the correction information database 470 of the control unit 46 has been obtained. finish.

FIG. 10 is a flowchart showing the operation of the driver 45 of the electric circuit shown in FIG. Each process of the flowchart of FIG. 10 is performed by the control unit 46.

This flowchart is executed on the premise that the necessary correction function β (toff) is obtained from the flowchart of FIG. 9 at the stage of recording an image on the recording object by the image recording apparatus of FIG.

At the time of current drive, the control unit 46 sends the PWM control signal 455S as a switching signal (light emission information) for turning on / off the light emission control unit 455 to the light emission control unit 455, but according to the flowchart of FIG. 10, a correction function is performed before transmission. The control signal is corrected by β.

First, the PWM control signal 455S is set. The PWM control signal 455S includes information on the pixel frequency (pixel period T), the energization time t0 = p, and the energization stop time toff = q (step S101). At this time, T = p + q.

Next, the correction energy ΔE is calculated using the correction function β (toff) (step S102). For example, the control unit 46 inputs the energization stop time toff = q into the equation (5) or (6), and calculates the correction energy ΔE as the output value of the correction function β.

Next, the additional energization time Δt is obtained from the calculated correction energy ΔE, the voltage V across the output unit 454, and the current value I (step S103). For example, the control unit can calculate the additional energization time Δt by dividing the correction energy ΔE by the power VI of the output unit (Δt = ΔE / VI).

Then, the energization time and the energization stop time are corrected using the calculated additional energization time Δt (step S104). Specifically, assuming that the pixel period T does not change, the corrected energization time is t0 = p + Δt, and the energization stop time is toff = q−Δt. The control unit 46 transmits the corrected PWM control signal 455S based on the corrected energization time and energization stop time to the light emission control unit 455. When the process of step S104 is completed, this control flow ends.

FIG. 11 is a hardware configuration diagram of the control unit 46. As shown in FIG. 11, the control unit 46 is physically a CPU (Central Processing Unit) 101, a RAM (Random Access Memory) 102 and a ROM (Read Only Memory) 103 as main storage devices, and an input device. It can be configured as a computer system including an input device 104 such as a keyboard and a mouse, an output device 105 such as a display and a touch panel, a communication module 106 which is a data transmission / reception device such as a network card, and an auxiliary storage device 107 such as a hard disk. ..

Each function of the control unit 46 described above loads the communication module 106, the input device 104, and the output under the control of the CPU 101 by loading predetermined computer software (output control program) on the hardware such as the CPU 101 and the RAM 102. This is achieved by operating the device 105 and reading and writing data in the RAM 102 and the auxiliary storage device 107.

The output control program of this embodiment is stored in, for example, a storage device included in a computer. A part or all of the output control program may be transmitted via a transmission medium such as a communication line, and may be received and recorded (including installation) by a communication module or the like provided in the computer. Further, the manufacturing execution program has a configuration in which a part or all of the manufacturing execution program is recorded (including installation) in the computer from a state of being stored in a portable storage medium such as a CD-ROM, a DVD-ROM, or a flash memory. May be.

As described above, in the output control device 140 according to the present embodiment, the control unit 46 has an energization time t0 and an energization stop time toff of the current flowing through the laser light emitting element 41 according to the desired output of the laser light emitting element 41. Once determined, the energization time correction value Δt is obtained using the correction function β (toff) individually set for each laser light emitting element 41, and the energization time and the energization stop time are corrected based on the energization time correction value Δt.

With this configuration, when light is emitted from a plurality of laser emitting elements 41 arranged in an array to record an image, even if there are individual differences in modulation characteristics depending on the laser emitting elements 41, the laser emitting element 41 can be supplied. By correcting the length of the energization time t0 based on the length of the energization stop time toff, it is possible to suppress the variation in the output between the laser emitting elements 41. As a result, it is possible to suppress energy variation of pulses generated in the main scanning direction (arrangement direction of the laser emitting element 41) orthogonal to the moving direction of the recording object (for example, the heat-sensitive recording label RL in FIG. 1), and as a result, the recorded image. Density variation and density unevenness, deterioration of accuracy of three-dimensional objects and processing defects are improved.

Further, in the present embodiment, the correction function β (toff) can be formulated as, for example, the above equations (5) to (8), but the point is that it is a function of the energization stop time toff in each of the plurality of laser light emitting elements 41. is there. More specifically, the correction function β (toff) can also be expressed as a function set to compensate for the energy output from the laser emitting element 41 fluctuating due to the energization stop time toff at an arbitrary energization time t0. More specifically, the correction function β (toff) can also be expressed as including a polynomial function or an exponential function of the energization stop time toff in each of the plurality of laser light emitting elements 41. Further, the correction function β (toff) can be expressed as a monotonically increasing function in which the energization stop time toff is a variable. It can also be expressed that the correction function β (toff) is a function set to compensate for the change in the optical system temperature or the change in the coupling efficiency of the light source with respect to the energization stop time toff.

By using such a correction function β (toff), it is possible to express a highly accurate function according to the individual modulation characteristics of the plurality of laser light emitting elements 41, and sufficiently cover the difference in the modulation characteristics between the elements. Therefore, the output of each element can be made more uniform.

The present embodiment has been described above with reference to specific examples. However, the present disclosure is not limited to these specific examples. Those skilled in the art with appropriate design changes to these specific examples are also included in the scope of the present disclosure as long as they have the features of the present disclosure. Each element included in each of the above-mentioned specific examples, its arrangement, conditions, shape, etc. is not limited to the illustrated one, and can be appropriately changed. The combinations of the elements included in each of the above-mentioned specific examples can be appropriately changed as long as there is no technical contradiction.

100 Image recording system (image recording device)
140 Output control device (laser output device)
41 Laser light emitting element (output element)
454 Output unit 455 Light emission control unit (switch unit)
455S PWM control signal (switching signal)
46 Control unit β (toff) correction function t0 Energization time toff Energization stop time Δt Energization time correction value

Patent No. 6077263

Claims (11)

With at least one output element
A control unit that controls the output of the output element by switching the energization of the output element on and off.
Have,
When the energization time and the energization stop time of the current flowing through the output element are determined according to the desired output of the output element, the control unit uses a correction function individually set for each of the at least one output element. The energization time correction value is obtained, and the energization time and the energization stop time are corrected based on the energization time correction value.
Output control device. The output section connected to the output side of the current drive circuit and
It has a switch unit connected to the output unit and
The at least one output element is connected to the output unit and is connected to the output unit.
The control unit outputs a switching signal for switching on / off of the switch unit to the switch unit to control energization of the output element.
The switching signal is generated based on the corrected energization time and energization stop time.
The output control device according to claim 1. The correction function is a function of the energization stop time in each of the at least one output element.
The output control device according to claim 1 or 2. The correction function is a function set to compensate for the fluctuation of the energy output from the output element depending on the energization stop time at an arbitrary energization time.
The output control device according to claim 3. The correction function includes a polynomial function or an exponential function of the energization stop time in each of the at least one output element.
The output control device according to claim 4. The correction function is a monotonically increasing function with the energization stop time as a variable.
The output control device according to claim 5. The output control device according to any one of claims 1 to 6 is provided.
The output element is a laser emitting element.
Laser output device. The correction function is a function set to compensate for a change in the optical system temperature of the light source or a change in the coupling efficiency with respect to the energization stop time.
The laser output device according to claim 7. The laser output device according to claim 7 or 8 is provided.
An image recording device that records an image by giving energy to the recording object by irradiating the recording object with laser light emitted from the laser light emitting element. It is an output control method of an output control device having at least one output element and controlling the output of the output element by switching on / off of energization of the output element.
A step of determining the energization time and energization stop time of the current flowing through the output element according to the desired output of the output element, and
A step of obtaining an energization time correction value using a correction function individually set for at least one output element, and
An output control method including a step of correcting the energization time and the energization stop time based on the energization time correction value. An output control program of an output control device having at least one output element and controlling the output of the output element by switching on / off of energization of the output element.
A function of determining the energization time and energization stop time of the current flowing through the output element according to the desired output of the output element, and
A function of obtaining an energization time correction value using a correction function individually set for at least one output element, and
A function for correcting the energization time and the energization stop time based on the energization time correction value, and
An output control program for realizing a computer.

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