JPH0445270Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a device for driving a pulsed laser element to emit light, and particularly relates to a pulsed laser element driving device in a system having a plurality of pulsed laser elements. .

(Prior Art) As a system that uses laser light as a measurement medium, for example, there is a system in which a plurality of laser diodes are provided and the laser diodes are sequentially driven to emit laser light in a scanning manner.

A laser diode driver for such a system is conventionally configured as shown in FIG.

That is, in the conventional laser diode driving device, switching means for driving light emission, such as transistors Q ₂₁ to Q _2o , are connected in series to each of a plurality of laser diodes D ₁ to D _o , and the laser diode D ₁ to D o is connected in series. ~D _o and transistor
Capacitors C ₁ to _{C o} for storing luminous energy are connected in parallel to each of the series circuits with Q ₂₁ to Q _2o , and the laser diode D ₁
~D _o , transistor Q ₂₁ ~Q _2o and capacitor C ₁
~ Constant current circuit for each of the circuits due to C _o
A ₁ to A _o are provided, and further transistors Q ₂₁ to _{Q 2o}
Gates G ₁ to _{G o} for inputting light emission drive command signals to the control terminals (bases) of the circuits are provided for each of the above circuits, and one input terminal of the gates G ₁ to _{G o} is all dual-type. The input terminals are connected to the trigger signal terminal T, and the other input terminals are individually connected to the light emitting element designation terminals S ₁ to _{S o} .

All of the capacitors C ₁ to _{C o} are normally charged through a path of "power supply terminal V - constant current circuit A ₁ - _{A o} - capacitor C ₁ - _{C o} - ground". Further, the transistors Q ₂₁ -Q _2o are always off, so the laser diodes D ₁ -D _o do not emit light.

When driving a laser diode, for example _D1 , to emit light, a trigger signal is input to the terminal T after inverting the level of the terminal _S1 corresponding to the laser diode _D1 to a high level. As a result, the moment the trigger signal is input, the gate G ₁ opens and the transistor Q ₂₁ turns on, completing the closed loop of "capacitor C ₁ - transistor Q ₂₁ - laser diode D ₁ - capacitor C ₁ ". A discharge current flows through, and laser diode _D1 emits light.

When driving a laser diode in pulses (pulsed laser system), the duty ratio (ratio of light emission time to light emission cycle) is usually 0.1%.
It is driven by a large current of several tens of amperes and obtains a light emitting output of several watts. As described above, the charging and discharging action of a capacitor is used as a means to flow a large current in an extremely short period of time.

(Problem to be solved by the invention) According to the above conventional technology, the transistor Q ₂₁ ~
Since a current of several tens of amperes flows through Q _2o , the transistors Q ₂₁ to _{Q 2o} must be used for high power. Using a large number of such transistors increases the size and cost of the device.

Also, keep capacitors C ₁ to _{C o} charged at all times,
At the time of discharge, it is necessary to discharge only the capacitor specified by the terminals S ₁ to _{S o} regardless of other capacitors, so constant current circuits A ₁ to A _o are required for each of the capacitors C ₁ to C _o , This also causes an increase in the size and cost of the device.

The present invention is proposed to solve the above-mentioned conventional problems.

(Means for Solving the Problems) In order to solve the above problems, the present invention provides a plurality of series circuits of pulse laser elements and capacitors in parallel, and provides a charging control circuit for each of the charging paths of the capacitors. In addition, a light emission control switch means for discharging the charge in the capacitor to drive the pulse laser element to emit light is provided in common for the series circuit group of the pulse laser element and the capacitor. This is what I did.

(Configuration of Example) The configuration of an embodiment of the present invention is shown in FIG.

As shown in FIG. 1, pulsed laser elements, such as laser diodes D ₁ to _{D o} , are connected in series with capacitors C ₁ to _{C o} for storing emitted energy, respectively, and these series circuits are connected in parallel. Laser diodes D ₁ to D _o are commonly connected to this series circuit group and in parallel with the series circuit group.
A switch means for controlling the light emission of the capacitors C 1 to C o, for example, a transistor Q ₂ is provided, and a switch means for controlling the charge of the capacitors C ₁ to C _o , for example, a transistor Q ₁₁ is provided.
~Q _1o is provided in series with each of the capacitors C ₁ -C _o and in parallel with each of the laser diodes D ₁ -D _o .

In the device of this embodiment, the constant current circuit A may be provided in common to all the laser diodes D1 _{to D0} by controlling the charging of _the capacitors _C1 to C0 individually by the transistors _Q11 to _Q10 .

Furthermore, compared to the conventional example, transistors Q ₁₁ to _{Q 1o} for charge control are required, but the transistors Q ₁₁ to _{Q 1o} may be small ones for low power use.
The only large transistor for high power use is transistor _Q2 for light emission control.

(Operation of the embodiment) FIG. 2 is a time chart explaining the operation of the embodiment. Furthermore, Figure 2 shows the laser diode.
The operation is shown in which D ₁ to D _o are sequentially driven to emit light and this is cyclically repeated.

A signal that turns on the transistors Q _{11 -Q 1o} for a set period of time is sequentially applied to the terminals S 1 -S _o , and a signal that turns on the transistor Q ₂ for a very short period of time is applied to the terminal T as a signal to the terminals S ₁ -S _o . It is applied each time the application of . The signals applied to the terminals S ₁ to S _o correspond to the laser diodes D ₁ to D _o , respectively, and are signals for specifying the laser diode to be driven to emit light (light emitting element specification signal). The applied signal is a signal (trigger signal) for driving the laser diode specified by the applied signal to the terminals S ₁ to _{S o} to emit light.

When a light emitting element designation signal is applied to terminal _S1 , transistor _Q11 is turned on, and the following path is established: "Power supply terminal V - Constant current circuit A - Capacitor _C1
- Transistor Q ₁₁ - Ground'' capacitor C ₁ is charged and luminous energy is accumulated.

Next, when the application of the light emitting element designation signal to the terminal S ₁ is stopped and the trigger signal is applied to the terminal T, the transistor Q ₁₁ is turned off, the transistor Q ₂ is turned on, and a closed loop is established through the following path _. A transistor _Q2 - laser diode _D1 - capacitor _C1 is formed, and the capacitor _C1 is momentarily discharged, and the luminescent energy stored in the capacitor _C1 flows into the closed loop as a luminescent current, and the laser diode _D1 Drives the light emission.

Since the direction in which the discharge current from the capacitor C ₁ flows is opposite to the polarity of the other laser diodes D ₂ to D _o , the discharge current flows only to the laser diode D ₁ corresponding to the terminal S ₁ and the above It does not flow to other laser diodes D ₂ ~ _{D o} . Furthermore, the end of the light emitting element designation signal applied to the terminal _S1 and the start of the trigger signal applied to the terminal T do not necessarily have to coincide; for example, the end of the light emitting element designation signal is later than the start of the trigger signal. You can. In this case, there is a period when transistor Q ₁₁ and transistor Q ₂ are on at the same time,
Since the polarity of the transistor _Q11 is opposite to the direction of the discharge current of the capacitor _C1 , the discharge current does not flow through the transistor _Q11 .
Note that the relationship between the end of the light emitting element designation signal and the end of the trigger signal must be such that the former always comes before the latter.

Next, when a light emitting element designation signal is applied to terminal _S2 ,
When the capacitor C ₂ is charged and luminous energy is accumulated in the same manner as above, and a trigger signal is applied to the terminal T, the discharge current from the capacitor C ₂ flows through the laser diode D ₂ in the same manner as above. Laser diode _D2 is driven to emit light.

Thereafter, a light emitting element designation signal is sequentially applied to the terminals S ₃ -S _o , and a trigger signal is applied to the terminal T each time, so that the laser diodes D ₃ -D _o are sequentially driven to emit light. By repeating this operation cyclically, laser light can be emitted in a scanning manner within a set angle range, for example.

In the above operation, the duration of the light emitting element designation signal is set to a time sufficient to complete charging of the capacitors C ₁ to C _o , and the duration of the trigger signal is set to a time sufficient to complete the charging of the capacitors C ₁ to _{C o} . It is set as above. The emission time of laser diodes D ₁ ~ _{D o} is
Since it is determined by the time constant of each closed discharge loop, the duration of the trigger signal does not require a precise value.

In addition, in the above operation, a large current (discharge current) instantly flows through the transistor Q ₂ , so a _large power transistor is required _.
Since only a small current (charging current) flows through the battery, a low-power one is sufficient.

(Effects of the invention) As explained above, the present invention charges the capacitors corresponding to the laser diodes to be driven to emit light individually at the time when they should be driven to emit light, and controls the light emission by means of a switch common to all laser diodes. Therefore, only one large switch is required for light emission control, and the power supply circuit (constant current circuit) can be provided in common for all laser diodes, so multiple This invention greatly contributes to the miniaturization and cost reduction of systems using pulsed laser elements, and has an extremely large effect.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of an embodiment of the present invention, FIG. 2 is a time chart showing the operation of the embodiment, and FIG. 3 is a circuit diagram of a conventional example. Main symbols: D ₁ - D _o ... Pulse laser element (laser diode), C ₁ - C _o ... Capacitor,
Q ₁₁ to _{Q 1o} ...Switch means (transistor) for capacitor charging control, Q ₂ ...Switch means (transistor) for light emission control.

Claims (1)

[Scope of utility model registration request] In an apparatus for driving a plurality of pulsed laser elements to emit light using a discharge current of a capacitor, a capacitor is provided in series with each of the pulsed laser elements, and a capacitor charge control switch is provided in each individual portion of a charging path of the capacitor. means and
A pulse laser element driving device comprising a light emission control switch means provided in a common part of the discharge path of the capacitor via the pulse laser element.