Electromagnetic transmitter system

State of the art

The invention relates to an electromagnetic transmitter assembly according to the preamble of claim 1.

It is known, emitting at distance measuring light Diodes (LED) to be used as transmission light source. It should also has already been proposed as a transmitting laser diode light source use in distance measuring devices. Such a laser rangefinder For example, from the published patent DE 43 33 113 A1.

ADVANTAGES OF THE INVENTION

The invention relates to an electromagnetic transmitter assembly with a laser diode as well as driving means for driving the laser diode.

It is proposed that the driving means formed are to operate the laser diode below a current threshold, above which the laser diode in a range induced emission of electromagnetic radiation works, so that the laser diode in the region of spontaneous emission electromagnetic radiation is operable. As a result, dispense with a complicated and expensive control of the laser diode will. At the same time exploits the fact that the laser diode by their special resonator in a LED operating range with spontaneous emission of radiation a numerical aperture and a small exit area of ​​the transmitted beam have the almost the same advantageous low Size as the actual laser operating range. Thereby can be used as a LED, the laser diode, without the adverse properties of an LED as huge Emitting surface of the radiation which a collimating the emission beam difficult, and their adverse inhomogeneous intensity distribution, of a maximum design electrode Center of the exit surface due to have to accept. In addition, a very low-cost laser diode with relatively low quality are used, as their laser operation area is not important. The invention contrast, transmission assembly includes a bundled transmitted beam with a homogeneous intensity distribution. As a result, an inexpensive transmission source to be created. Preferably is the radiation in the visible range, but also, Semiconductor materials, radiation depending on the user to conceivable in the visible or ultraviolet.

Embrace the drive means a first amplifier for driving the laser diode, this can be very simple and in accordance with be carried out inexpensively.

Embrace the drive means a modulation signal source, the modulation signal can be easily in the first amplifier are admixed. Thereby, a modulated transmission beam of the laser diode can be produced. This is advantageous for a Use in distance measuring devices.

Embrace the drive means is a photodiode, this can of receive the laser diode emitted electromagnetic radiation.

Preferably, the photodiode forms a power source for the Laser diode. Depending on the current, the laser diode is driven will.

Preferably, the photodiode of the laser diode forms with a feedback arrangement. An actual signal from the photodiode may be the controlling the first amplifier. The current supplied by the photodiode Output current is small enough, so that always the appropriate Stream is fed to the laser diode to below this the current threshold for laser operation area remains and therefore always works in the LED driving range.

Assigns the feedback arrangement to a low-pass filter, between the photodiode and a first input of the first is connected amplifier, faults can and Noise of the output signal of the photodiode without much effort are eliminated.

The photodiode is connected to an input of a reference amplifier connected, a signal from the current of the photodiode Voltage reference signal of possible recipient and / or Evaluation, as for a run-time measurement of the transmitted beam, be generated.

If a radiation detector assembly is provided which at an object reflected radiation of the laser diode receives, the transmission arrangement can be used in a distance measuring device will.

If the radiation receiver arrangement, a reference signal of Reference amplifier supplied, this may depend on the modulation of the laser diode can be controlled.

Advantageously, finds the transmission arrangement in a handheld power tool Use. In a drill, in particular a hammer, a removal of the transmission arrangement measured to one with a hole to be provided space and thereby determines the current depth of the hole will.

Conveniently, a use of the transmission arrangement in a distance measuring device. It is a cheap way to Distance measurement possible.

It is also favorable to the use of the transmitted light arrangement in a laser pointing device or a light barrier.

drawing

Further advantages arise from the following drawing description. In the drawing, an embodiment of the Invention. The drawing, description and the claims contain numerous features in combination. The skilled artisan will the features individually expediently consider and combine them to form further reasonable combinations. Show it:<dl tsize="6" compact="compact"><dt>Fig. 1</dt><dd>a characteristic of an optical output power a laser diode as a function of the Laser diode electric current supplied,</dd><dt>FIG. 2</dt><dd>a schematic diagram of a transmission arrangement a distance measuring device and</dd><dt>Fig. 3</dt><dd>a schematic diagram of a further Transmitting arrangement.</dd></dl>

Description of Embodiments

Fig. 1 shows a typical characteristic curve of a laser diode, wherein an optical output power P_opt against a in the laser diode injected current I is applied. The characteristic increases linearly with the current I and shows two characteristic ranges A, B with different pitches, different Operating areas characterization. Above a Current threshold I_TH is located in the characteristic range B of the normal Laser operating range of the laser diode, in the production by a population inversion of charge carriers in the semiconductor material the laser diode an induced emission of electromagnetic Radiation takes place and the ordinary operation mode of the laser diode corresponds. The slope of the line for a current I above the current threshold I_TH is a Measure of the quality of the laser diode. Below the current threshold I_TH the characteristic area A, the laser diode behaves contrary as a conventional LED and shows a spontaneous emission of electromagnetic radiation. This LED operating range corresponds to the operating range of the laser diode in the present invention Transmitting arrangement.

Fig. 2 shows a schematic diagram of a preferred electromagnetic transmission arrangement, as described for example in can be used a rangefinder. to drive the laser diode 10, a first amplifier 12 is provided. This controls the laser diode 10 preferably always below a current threshold I_TH at which, when exceeded the laser diode 10 induced in a range of emission electromagnetic radiation is working, so that the laser diode 10 spontaneous in the field emission of electromagnetic Radiation, preferably visible light, operable is.

Further, for driving the laser diode 10, a modulation signal source 14 is provided. This initiates modulation signal via a line 42 to the first amplifier 12, in which the modulation signal into a drive signal of the laser diode 10 is fed, which is indicated by a mixer icon is.

A photodiode 16 is disposed adjacent to the laser diode 10 and receives direct or indirect electromagnetic Radiation which is emitted from the laser diode 10th The Photodiode 16 is thereby turned on and is an electric Stream from which a line 40 partially over a conventional Low-pass filter 18, a capacitor 34 and a Resistor 36 comprises, to a first input 30 of the first Amplifier 12 is passed and partly to a second Amplifier 20 with a first resistor 28. The second input 32 of the first amplifier 12 is grounded.

The photodiode 16 forms with the laser diode 10 is a feedback or regulating arrangement for regulating the flow of Laser diode 10. The stronger the laser diode 10 emits, the more stronger the influence of the photodiode 16 input signal at the first input 30, which with a suitable choice of the resistors 36, 38 and the potential level on the resistor 38 the current of the laser diode 10 attenuates. Together with the third Resistor 38, connected to the second resistor 36 a voltage divider forms, an operating point of the first amplifier 12 pre-set and by the feedback arrangement be managed.

The second amplifier 20, with its first input 22 the Photodiode 16 is connected, forms a reference amplifier, at its output 26 a reference signal U_ref be removed can. The reference signal U_ref corresponds to that of the Laser diode 10 emitted light signal.

The second input 24 is connected to ground. In the embodiment, represents the second amplifier 20 is a current-voltage converter demonstrate how it used with typically a photodiode 16 becomes. The output voltage is dependent on the first resistor 28, the first between the inverting input 22 and the output is 26. The reference signal U_ref can for driving a radiation detector assembly, not shown, be used which is reflected on an object electromagnetic radiation of the laser diode 10 receives and For example, at run time measurement in a distance measuring device is used.

A dimensioning of the electrical components, such as resistors 28, 36, 38, capacitors 34, voltage dividers, amplifier 12, 20 and the like, the skilled artisan will accordingly make the desired properties useful.

By design sends the laser diode 10 a collimated Beam of electromagnetic radiation, for example, as ranging signal for a distance measuring device or be used for a drill or a hammer drill can, to view or set a depth. alternative the beam without distance measuring function in a Laser pointing device or can be used in a light barrier.

Another schematic representation of a with respect to FIG. 2 simplified circuit shown in FIG. 3. The low pass filter 18 of FIG. 2 is suitable by any those skilled in the appearing low-pass filter 44 is replaced and the second input 32 of the first amplifier 12 is connected to a reference voltage source 46, the suitable to a potential can be adjusted. The mixer of the first amplifier 12 is omitted, wherein the signal from the modulation signal source 14 simply added to the signal of the first amplifier becomes. The principle corresponds to the simplified circuit the operating principle of the circuit of FIG. 2.

The laser diode 10 operates in the LED operating very stable and is easy to operate. Therefore, in a further in the figures not shown, the simplification on the feedback or Control arrangement for controlling the current of the laser diode 10 omitted. Then, the low pass filter 18, 44 and the feedback to the first amplifier 12 are eliminated. When operating without a distance measurement can also photodiode 16, the arrangement to the second amplifier 20, the Generating the reference signal and the modulation signal source 14 omitted. The laser diode 10 can then be operated so, that they in the LED driving portion constant a transmission beam sends. The laser diode 10 is controlled by a current source supplied and driven by the first amplifier 12th

numeral

<dl tsize="2" compact="compact"><dt>10</dt><dd>laser diode</dd><dt>12</dt><dd>first amplifier</dd><dt>14</dt><dd>Modulation signal source</dd><dt>16</dt><dd>photodiode</dd><dt>18</dt><dd>Low Pass Filter</dd><dt>20</dt><dd>reference amplifier</dd><dt>22</dt><dd>first input reference amplifier</dd><dt>24</dt><dd>second input reference amplifier</dd><dt>26</dt><dd>Output reference amplifier</dd><dt>28</dt><dd>first resistance</dd><dt>30</dt><dd>first input</dd><dt>32</dt><dd>second input</dd><dt>34</dt><dd>capacitor</dd><dt>36</dt><dd>second resistor</dd><dt>38</dt><dd>third resistor</dd><dt>40</dt><dd>management</dd><dt>42</dt><dd>management</dd><dt>44</dt><dd>Low Pass Filter</dd><dt>46</dt><dd>Reference voltage source</dd></dl>