KR20210078114A - Apparatus and method for driving a light source - Google Patents

Abstract

The present invention relates to a device and method for controlling the driving of a light source according to a state of a diffuser or when a subject approaches close proximity. The present invention relates to a method for controlling the operation of a light source in a 3D sensing system comprising a light source mounted on a PCB, a diffuser which is fixed by a holder and which diffuses light outputted from the light source positioned therebelow and passes the same therethrough, and a photoreactive element which is mounted on the PCB next to the light source so as to react to the amount of reflected light. The method includes the steps of: comparing a voltage of the photoreactive element, which changes according to the amount of light, with a first reference voltage set to check whether the diffuser is damaged; and selectively controlling, according to a comparison result, the turning off of a driver for driving the light source. Therefore, it is possible to minimize damage by direct irradiation of the light source by controlling the driving of the light source according to the state of the diffuser.

Description

Light source driving control device and method {APPARATUS AND METHOD FOR DRIVING A LIGHT SOURCE}

The present invention relates to a 3D sensing system, and more particularly, to an apparatus and method for controlling driving of a light source according to a state of a diffuser.

As interest in a stereoscopic image service increases, devices for providing a stereoscopic image are being developed and distributed. Among 3D sensing methods for realizing a stereoscopic image, there are a stereoscopic method, a time of flight (TOF) method, a structured light method, and the like.

The basic principle of the stereoscopic method is to separate and input images arranged to be orthogonal to each other in the left and right eyes of a person, and the images input to the left and right eyes are combined in the human brain to generate a stereoscopic image. Stereo-type 3D cameras have problems such as high-precision assembly process and yield reduction due to quality problems caused by assembly errors between the two cameras, which lowers the 3D quality.

Meanwhile, the structured light method acquires depth information of an object by irradiating a laser beam coded with a specific pattern to the object, and calculating the pattern shift amount of the reflected light. This method generally uses a fixed focus lens and a passive coding element. Therefore, there is a disadvantage in that it is not possible to acquire an image while changing the resolution according to various environments.

The time of flight (TOF) method is a method of acquiring depth information of an object by irradiating light directly to a subject and calculating the time of reflected light to be reflected and returned.

Among the above-described 3D sensing methods, the TOF method, which has advantages such as a high frame rate due to a low amount of calculation, a small footprint, a relatively low manufacturing cost, and a characteristic strong against sunlight, is receiving much attention.

The TOF method basically projects light of a specific wavelength to a subject, measures or captures the light of the same wavelength reflected from the subject with a photodiode (D) or a camera, and extracts a depth image.

Since the 3D sensing distance is determined in proportion to optical power in the TOF method, set makers usually try to increase the power of the light source (VCSEL) by increasing the driving current. In general, a 3D sensing system to which the TOF method is applied is provided with a diffuser that changes a point light source to a surface light source.

However, if the diffuser disappears or is damaged as shown in FIG. 1 , the laser light from the light source is directly irradiated to the eyes or skin of the subject, which may cause damage. Therefore, a new method for this is needed.

Republic of Korea Patent Publication No. 10-2017-0130203

Accordingly, the present invention is an invention devised according to the above-mentioned necessity, and the main object of the present invention is to control the driving of a light source in a 3D sensing system that can minimize damage by direct irradiation of the light source by controlling the driving of the light source according to the state of the diffuser. To provide an apparatus and a method therefor.

Furthermore, it is another object of the present invention to provide a light source driving control apparatus and method for a 3D sensing system capable of minimizing damage to a subject that may be caused by light irradiated from a light source when the subject approaches close proximity.

A light source driving control apparatus according to an embodiment of the present invention for achieving the above object is 3D sensing including a light source mounted on a PCB, and a diffuser that is fixed by a holder and diffuses and passes light output from the light source located below. A device applicable to the system, comprising:

a photodiode mounted on a PCB next to the light source to respond to the amount of reflected light;

a voltage generator connected to one side of the photodiode to generate a photodiode detection voltage;

a first comparator for comparing the photodiode detection voltage with a first reference voltage set to check whether the diffuser is damaged;

and a driver control unit that selectively turns off the driver of the light source according to a comparison result of the photodiode detection voltage and the first reference voltage.

Furthermore, the above-described light source driving control device further includes a second comparator for comparing the photodiode detection voltage with a second reference voltage set to check whether or not a subject is in proximity, wherein the driver control unit includes an output of the second comparator. Another feature is to selectively turn off the driver of the light source according to the

A light source driving control device according to another embodiment of the present invention is a device applicable to a 3D sensing system including a light source mounted on a PCB, and a diffuser that diffuses and passes light output from the light source located below the light source fixed by a holder as,

a transparent electrode layer formed on the diffuser and patterned to include a transparent electrode and have a constant resistance value;

a current supply connected to the transparent electrode to apply a bias current;

comparators for comparing the state voltage of the transparent electrode generated according to the application of the bias current with different reference voltages;

It is another feature to include a; a driver control unit that turns off the driver of the light source when the state voltage of the transparent electrode is out of the different reference voltage ranges.

Furthermore, the light source driving control method according to an embodiment of the present invention includes a light source mounted on a PCB, a diffuser that is fixed by a holder and diffuses and passes light output from a light source located below, and is mounted on a PCB next to the light source. As a method feasible in a 3D sensing system comprising a photoreactive element that responds to the amount of reflected light,

comparing the voltage of the photoreactive element, which varies according to the amount of light, with a first reference voltage set to check whether the diffuser is damaged;

and selectively turning off a driver for driving the light source according to the comparison result.

According to the above-described technical problem solving means, the present invention detects the voltage of the photodiode through the photodiode that is mounted on the PCB next to the light source and responds to the amount of reflected light, and sets the detected voltage to check whether or not the subject is close. By comparing the reference voltage with another reference voltage set to check whether the diffuser is damaged, and forcibly turning off the driver of the light source according to the comparison result, damage to the subject due to damage to the diffuser or close proximity to the subject can be minimized. .

1 is a diagram illustrating a broken state of a diffuser in a 3D sensing system.
2 and 3 are cross-sectional views of a light source (VCSEL) package of a light source driving control apparatus according to an embodiment of the present invention.
4 is an exemplary configuration diagram of a light source driving control device according to an embodiment of the present invention.
5 to 7 are waveform exemplary diagrams for explaining the operation of the light source driving control device shown in FIG.
8 is a cross-sectional view of another light source package of the light source driving control device according to the embodiment of the present invention.
FIG. 9 is an exemplary configuration diagram of another light source driving control device related to FIG. 8 .
10 and 11 are waveform examples for explaining the operation of the light source driving control device shown in FIG.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The following detailed description of the present invention refers to the accompanying drawings, which show by way of illustration a specific embodiment in which the present invention may be practiced, in order to clarify the objects, technical solutions and advantages of the present invention. These embodiments are described in sufficient detail to enable those skilled in the art to practice the present invention.

Also throughout this description and claims, the word 'comprise' and variations thereof are not intended to exclude other technical features, additions, components or steps. Other objects, advantages and characteristics of the present invention will appear to a person skilled in the art, in part from this description, and in part from practice of the present invention. The following illustrations and drawings are provided by way of illustration and are not intended to limit the invention. Moreover, the invention encompasses all possible combinations of the embodiments indicated herein. It should be understood that the various embodiments of the present invention are different but need not be mutually exclusive. Accordingly, the detailed description set forth below is not intended to be taken in a limiting sense, and the scope of the invention, if properly described, is limited only by the appended claims, along with all scope equivalents to those claimed. Like reference numerals in the drawings refer to the same or similar functions throughout the various aspects.

Unless otherwise indicated herein or otherwise clearly contradicted by context, items referred to in the singular encompass the plural unless the context requires otherwise. In addition, in describing the present invention, if it is determined that a detailed description of a related known configuration or function may obscure the gist of the present invention, a detailed description thereof will be omitted.

Hereinafter, in order to enable those skilled in the art to easily practice the present invention, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. It is assumed that the following 3D sensing system is a camera device that is used in various fields such as 3D face recognition, automatic driving, virtual/augmented reality, and the like.

2 and 3 illustrate a cross-section of a light source (VCSEL) package of a light source driving control device according to an embodiment of the present invention, and FIG. 4 is a configuration diagram of a light source driving control device according to an embodiment of the present invention will be.

Referring first to FIG. 2 , the 3D sensing system according to an embodiment of the present invention includes a light source 10 mounted on a PCB. The light source 10 may be formed of a laser diode or a vertical-cavity surface-emitting laser (VCSEL). As shown, the light source 10 is fixed by the holder 20 and includes a diffuser 30 that diffuses and passes the light output from the light source 10 located below. In the following, it is shown that a VCSEL is employed as the light source 10 .

In order to check whether the diffuser 30 is damaged, the light source driving control device according to an embodiment of the present invention is mounted on a PCB next to the light source 10 and responds to the amount of light reflected from the diffuser 30 (PD). , 40).

)과 검출 전압의 평균치를 얻기 위한 LPF(50)로 구성할 수 있다.Furthermore, as shown in FIG. 4 , the light source driving control apparatus according to the embodiment of the present invention includes a voltage generator connected to one side of the PD 40 to generate a photodiode detection voltage VPD. The voltage generator is a resistor (

) and the LPF 50 for obtaining the average value of the detected voltage.

In addition, the light source driving control apparatus according to the embodiment of the present invention includes a first comparator 60 for comparing the averaged photodiode detection voltage LPF Out with a first reference voltage PD_DET_VTL set to check whether the diffuser is damaged. ,

The driver control unit 80 that selectively turns off the driver of the light source 10 according to the comparison result of the averaged photodiode detection voltage LPF Out and the first reference voltage PD_DET_VTL, which may be implemented in logic includes

Furthermore, as shown in FIG. 3 , in order to check whether an object is in proximity, the light source driving control apparatus according to an embodiment of the present invention uses the averaged photodiode detection voltage LPF Out to the second set to check whether the object is in proximity. A second comparator 70 for comparing with the reference voltage PD_DET_VTH may be further included. In this case, the driver control unit 80 outputs a signal for selectively turning off the driver of the light source according to the output OPD_ERR of the second comparator 70. The first comparator 60 and the first comparator 60 The two comparators 70 may be provided with any one or all of them as needed.

For reference, each of the reference voltages compared in the comparators 60 and 70 may change a voltage level through a resistor. In the enable generator (Enable Gen, 100) not described in FIG. 4, the driver control unit 80 periodically compares the photodiode detection voltage and the first reference voltage PD_DET_VTL or/and the second reference voltage PD_DET_VTH. A state monitoring signal (EN_PROTECT) for monitoring is generated and transmitted to the driver control unit 80 . As shown in FIG. 5 , the enable generator 100 is activated after a predetermined time delay (time until the photodiode detection voltage is stabilized) from the generation of the low voltage differential signal LVDS used in the 3D sensing system. Generates a monitoring signal. Such a state monitoring signal may be defined as a signal for activating the driver control unit 80 . In this case, without the enable generator 100 , the driver control unit 80 is activated according to the enable signal applied from the upper processor to include the photodiode detection voltage and the first reference voltage PD_DET_VTL or/and the second reference voltage PD_DET_VTH. It may be possible to control the driver of the light source by periodically monitoring the comparison result with the .

Hereinafter, the operation of the light source driving control device including the above-described configuration will be described in detail with reference to FIGS. 5 to 7 . FIGS. 5 to 7 are waveform examples for explaining the operation of the light source driving control device shown in FIG. 4 . are shown respectively.

First, the SPI/I2C command signal shown in FIGS. 5 to 7 is a pulse for setting the reference voltage in the register when the 3D sensing system is powered on, and the EN signal is a signal for activating the entire driver of the 3D sensing system, LVDS indicates a low voltage differential signal, and PD LPF Out Voltage indicates an output voltage of the LPF 50 which is a component of the voltage generator, that is, an averaged photodiode detection voltage.

If the diffuser 30 is not damaged or the subject is not close to the set position, the averaged photodiode detection voltage (PD LPF Out Voltage) in the section in which the state monitoring signal EN_PROTECT is activated is as shown in FIG. Similarly, a level higher than the first reference voltage PD_DET_VTL set to check whether the diffuser 30 is damaged or not and a level lower than the second reference voltage PD_DET_VTH set to check whether a subject is close to each other will be maintained.

However, as shown in FIG. 3 , when the subject comes closer than the set position, a greater amount of light is reflected by the subject, and the detection voltage of the photodiode 40 that reacts in proportion to the amount of light increases. As described above, when the photodiode detection voltage (PD LPF Out Voltage) is greater than or equal to the second reference voltage (PD_DET_VTH) set to check whether or not the object is close as shown in FIG. 6 due to the proximity of the subject, the driver control unit 80 controls the light source By forcibly turning off the driver of (EN_DRIVER), it prevents damage or damage to the subject in advance due to proximity to the subject.

On the other hand, if the diffuser 30 is damaged as shown in FIG. 1, the amount of light reflected therefrom is reduced, so that the detection voltage (PD LPF Out Voltage) of the photodiode 40 is lowered as shown in FIG. 7, and the photodiode (40) When the detection voltage (PD LPF Out Voltage) is below the first reference voltage (PD_DET_VTL) set to check whether the diffuser is damaged, the driver control unit 80 forcibly turns off the driver of the light source, thereby damaging the diffuser 30 This prevents the subject from being damaged or damaged in advance.

Therefore, the present invention is an invention that can minimize damage to the subject that may be caused by the light irradiated from the light source when the subject approaches or/or the diffuser 30 is damaged.

Hereinafter, the mechanical and circuit features of the light source driving control device according to another embodiment of the present invention will be described in detail.

8 is a cross-sectional view of another light source package of the light source driving control device according to an embodiment of the present invention, FIG. 9 is a block diagram of another light source driving control device related to FIG. 8, and FIGS. 10 and 11 are Each of the waveform diagrams for explaining the operation of the light source driving control device shown in FIG. 9 is exemplified.

As shown in FIG. 8 , the light source driving control device according to another embodiment of the present invention is fixed by a light source 10 mounted on a PCB and a holder 20, and outputted from the light source 10 positioned below. As a part of a 3D sensing system including a diffuser 30 that diffuses and passes light, a transparent electrode layer 65 formed on the diffuser 30 and containing a transparent electrode (ITO) and patterned to have a constant resistance value. include more

In addition to the above-described transparent electrode layer 65, the light source driving control device according to another embodiment of the present invention is a circuit feature element, as shown in FIG. 9 ,

)과,A current source for applying a bias current connected to the transparent electrode (ITO) (

)and,

)을 서로 다른 기준전압(RDET_VTL, RDET_VTH)과 각각 비교하는 비교기들(75,85)과,The transparent electrode state voltage (

) with different reference voltages RDET_VTL and RDET_VTH, respectively, with comparators 75 and 85, and

)이 상기 서로 다른 기준전압이 형성하는 범위를 벗어나면 광원의 드라이버를 오프시키는 드라이버 제어부(80)를 포함한다.The transparent electrode state voltage (

) out of the range formed by the different reference voltages, includes a driver control unit 80 that turns off the driver of the light source.

에 다양한 전압레벨을 생성할 수 있도록 바이어스 전류값을 레지스터에서 선택(레지스터 세팅)할 수 있도록 할 수도 있다.Corresponding to the resistance of the transparent electrode (ITO) in the above configuration

It is also possible to select the bias current value in the resistor (register setting) so that various voltage levels can be generated.

EN_RDET, which is not described in FIG. 9 , is a signal applied from the upper processor and may be defined as a transparent electrode state check signal for checking the state of the transparent electrode. The transparent electrode state check signal EN_RDET is activated at the end of the register setting period (SPI/I2C Command) as shown in FIG. 10 .

Hereinafter, the operation of the light source driving control device shown in FIG. 9 will be described in detail with reference to FIGS. 10 and 11 ,

)에 의해 인가되는 바이어스 전류(

)에 의해 투명전극 상태전압(

)은 도 10에 도시한 바와 같이 사전 설정된 두 기준전압(RDET_VTL, RDET_VTH) 사이에서 일정한 전압 레벨을 유지한다.First, if there is no damage to the diffuser 30 as shown in FIG. 1, the current source (

) applied by the bias current (

) by the transparent electrode state voltage (

) maintains a constant voltage level between two preset reference voltages RDET_VTL and RDET_VTH as shown in FIG. 10 .

) 값도 변하게 된다. 투명전극의 저항(

)값이 증가 혹은 감소하게 되면 그에 따라 투명전극 상태전압(

) 역시 변하게 되어 도 11에 도시한 바와 같이 미리 설정된 두 개의 기준전압(RDET_VTL, RDET_VTH) 범위를 상방 혹은 하방으로 벗어나게 된다. 이러한 경우 드라이버 제어부(80)는 광원의 드라이버를 강제적으로 오프시킴으로써, 디퓨저(30) 손상으로 인해 피사체가 손상되거나 피해를 입는 것을 사전에 예방한다.However, if the diffuser 30 is damaged, the resistance (

) will change as well. resistance of transparent electrode (

) increases or decreases, the transparent electrode state voltage (

) is also changed, and as shown in FIG. 11, the two preset reference voltages RDET_VTL and RDET_VTH are out of range upward or downward. In this case, the driver control unit 80 forcibly turns off the driver of the light source to prevent damage to or damage to the subject due to damage to the diffuser 30 in advance.

Accordingly, the light source driving control device shown in FIG. 9 also provides an effect of minimizing damage to a subject that may be caused by the light irradiated from the light source when the diffuser 30 is damaged.

The above has been described with reference to the embodiments shown in the drawings, which are merely exemplary, and those skilled in the art will understand that various modifications and equivalent other embodiments are possible therefrom. Accordingly, the true technical protection scope of the present invention should be defined only by the appended claims.

Claims (10)

A 3D sensing system comprising: a light source mounted on a PCB; and a diffuser that diffuses and passes light output from the light source positioned below the light source fixed by a holder,
a photodiode mounted on a PCB next to the light source to respond to the amount of reflected light;
a voltage generator connected to one side of the photodiode to generate a photodiode detection voltage;
a first comparator for comparing the photodiode detection voltage with a first reference voltage set to check whether the diffuser is damaged;
and a driver control unit for selectively turning off a driver of the light source according to a comparison result of the photodiode detection voltage and the first reference voltage. The method according to claim 1, further comprising a second comparator for comparing the detection voltage of the photodiode with a second reference voltage set to check whether a subject is close, wherein the driver control unit is the light source according to the output of the second comparator Light source driving control device, characterized in that the driver is turned off selectively. The method according to claim 1 or 2, wherein the voltage generator,
A resistor connected between the photodiode and the ground to detect the photodiode voltage (

)and;
the resistance (

) connected to one side of the LPF to obtain an average value of the photodiode voltage; The enable generator of claim 1 or 2, wherein the driver control unit generates a state monitoring signal (EN_PROTECT) for periodically monitoring a comparison result between the photodiode detection voltage and the first reference voltage or the second reference voltage. ; Light source driving control device, characterized in that it further comprises. The method according to claim 4, The enable generator,
and generating a state monitoring signal that is activated with a delay of a predetermined time from a point in time when the low voltage differential signal used in the 3D sensing system is generated. A 3D sensing system comprising: a light source mounted on a PCB; and a diffuser that diffuses and passes light output from the light source positioned below the light source fixed by a holder,
a photodiode mounted on a PCB next to the light source to respond to the amount of reflected light;
a voltage generator connected to one side of the photodiode to generate a photodiode detection voltage;
a second comparator for comparing the photodiode detection voltage with a second reference voltage set to check whether a subject is in proximity;
and a driver control unit for selectively turning off the driver of the light source according to a comparison result of the photodiode detection voltage and the second reference voltage. A 3D sensing system comprising: a light source mounted on a PCB; and a diffuser that diffuses and passes light output from the light source positioned below the light source fixed by a holder,
a transparent electrode layer formed on the diffuser and patterned to include a transparent electrode and have a constant resistance value;
a current supply connected to the transparent electrode to apply a bias current;
comparators for comparing the state voltage of the transparent electrode generated according to the application of the bias current with different reference voltages;
and a driver control unit that turns off the driver of the light source when the state voltage of the transparent electrode is out of the different reference voltage ranges. 3D comprising: a light source mounted on a PCB; a diffuser that diffuses and passes light output from the light source fixed by a holder but located below; and a photoreactive element mounted on the PCB next to the light source and reacting to the reflected light In the method for controlling the driving of a light source of a sensing system,
comparing the voltage of the photoreactive element, which varies according to the amount of light, with a first reference voltage set to check whether the diffuser is damaged;
and selectively turning off a driver for driving the light source according to the comparison result. The light source driving method according to claim 8, further comprising: comparing the voltage of the photoresponding element with a second reference voltage set to check whether or not a subject is in proximity before the step of selectively turning off the driver. control method. A light source mounted on the PCB, a diffuser that is fixed by a holder and diffuses light output from the light source located below, and a transparent electrode layer formed on the diffuser and patterned to contain a transparent electrode and have a constant resistance value; In the light source driving control method of the 3D sensing system comprising a current source for applying a bias current connected to the transparent electrode,
comparing the state voltages of the transparent electrodes generated according to the application of the bias current with different reference voltages;
and selectively turning off a driver for driving the light source when the state voltage of the transparent electrode is out of the different reference voltage ranges.

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