Laser angular speed detector employing non-optical output

A semiconductor ring laser apparatus is provided which comprises a semiconductor laser element having electrical terminals and optical terminals. An electrical power supply means is coupled to the electrical terminals for applying a voltage thereto and optical means are optically coupled to the optical terminals of the semiconductor laser element. The optical means form resonant ring optical paths in clockwise and counterclockwise directions for the light which is emitted by the semiconductor. Detector means are provided which are coupled to said electrical terminals for detecting voltage variations thereon caused by the rotation of the apparatus.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a semiconductor ring laser apparatus used for 
detecting an angular speed. 
2. Description of the Prior Art 
There has been hitherto known a helium neon ring laser apparatus such as 
shown in FIG. 1. In this Figure, a helium neon medium tube 1 is made of 
quartz or the like, and this medium tube 1 is provided with mirrors 2a, 
2b, a beam splitter 3, a prism 4 and electrodes 6,6 connected to a driving 
electric source 5. An optical detector 8 having an output terminal 7 faces 
the prism 4. 
This apparatus is brought into a ring laser oscillation condition by a 
ring-formed optical path 9 formed in the helium neon medium tube 1 and 
used as a ring resonator. A beam in a clockwise direction travels from the 
mirror 2a towards the beam splitter 3 to penetrate the beam splitter 3 and 
is then reflected by the prism 4 and travels again towards the beam 
splitter 3, and is reflected again before that position to reach the 
optical detector 8, while a beam in a counterclockwise direction travels 
towards the beam splitter 3 to penetrate the beam splitter 3 and the prism 
4 and reaches the optical detector 8. 
If now a certain angular speed is applied to the apparatus, there is a 
difference in frequency between the clockwise beam and the 
counterclockwise beam, and the difference is outputted from the output 
terminal 7 of the optical detector 8 as a beat signal of a change in 
optical output and thereby the angular speed can be detected. 
There has also been proposed such a semiconductor ring laser apparatus as 
shown in FIG. 2. Referring to this Figure, a semiconductor laser element 
10 is connected to a semiconductor laser element driving electric source 
12 through a variable resistance 11 for electric current adjustment. A 
lens 13 is provided, and the other elements correspond to those in FIG. 1 
and are denoted by identical members. 
This apparatus is also operated in almost the same manner as the apparatus 
in FIG. 1. Namely, when the apparatus is applied with an angular speed, a 
difference in frequency between the clockwise and counterclockwise beam is 
provided from the output terminal 7 of the optical detector 8 as beat 
signal of a change in optical output. Either of the angular speed 
detecting ring laser apparatuses shown in FIGS. 1 and 2 is of the type 
that the clockwise and counterclockwise beams are added together by the 
optical detector 8 by means of the optical system comprising the beam 
splitter 3 and the prism 4, and the difference in frequency between the 
two beams is provided from the optical detector 8 as a beat signal of a 
change in optical output. Thus, either apparatus of this type requires the 
optical detector 8, the optical system such as the beam splitter 3, the 
prism 4 and other elements and requires space for these components. 
Consequently, the same has the disadvantage that it is high in cost and 
large in size and weight, and should avoid vibration and change in 
temperature because the optical system requires an accurate adjustment. 
SUMMARY OF THE INVENTION 
It is the primary object of the present invention to provide semiconductor 
ring laser apparatus which is small in size and weight and relatively low 
in cost. 
It is another object of the present invention to provide a semiconductor 
ring laser apparatus which is relatively insensitive to vibrations and 
changes in temperature. 
The present invention is directed to a semiconductor laser element which is 
used as a laser element in a ring laser apparatus. The semiconductor laser 
element is connected to a driving electric source, and it is arranged so 
that when the apparatus is rotated at a certain angular speed, a beat 
signal of the difference in frequency between a clockwise beam and a 
counterclockwise beam is detected as a change in terminal voltage of the 
semiconductor laser element.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The phenomenon of the present invention will be illustrated with regards to 
an experimental apparatus shown in FIG. 3. An output beam from a 
semiconductor laser element 10 is focused on a mirror 2 through a lens 13, 
and a reflection beam thereof is blocked and passed repeatedly by rotation 
of a chopper 16. The reflection beam is thus caused to feed back and not 
to feed back repeatedly to the semiconductor laser element 10. In this 
apparatus, when the reflection beam is fed back thereto, the semiconductor 
laser element 10 is caused to have a self-coupling effect by the feedback 
beam. Consequently, its optical output, which is detected by the optical 
detector 8, is increased as compared with the occasion where the element 
10 receives no feedback beam. At the same time, the terminal voltage of 
the semiconductor laser element 10 connected to the driving electric 
source 12 is changed in accordance with the increase and decrease of the 
optical output. 
When, in FIG. 3, there is a multi-mode oscillation by the self-coupling 
effect caused by the feedback beam, there often appears on the optical 
output of the semiconductor laser element oscillations of a higher 
frequency (inductive oscillation) and, also in this case, there appears on 
the terminal voltage of the semiconductor laser element an oscillation of 
the frequency which is equal to that of the optical output oscillation. 
An output terminal 15 provides a change in terminal voltage of the 
semiconductor laser element 10 which can be electrically detected. 
Thus, in a semiconductor laser element, if the optical output is changed 
for a certain reason, the terminal voltage thereof is also changed in 
accordance with the change thereof. Accordingly, if this phenomenon is 
utilized, the optical beat signal in the semiconductor laser apparatus can 
be detected as a change in terminal voltage of the semiconductor laser 
element itself, instead of the conventional detecting as a change in 
optical output of an optical detector. 
FIG. 4 shows one embodiment of the present invention. A semiconductor laser 
element 10 is connected at its electrodes 10a, 10b to a driving electric 
source 12 through a resistance 11. Forward and rearward output beams 
thereof are formed into a ring-formed optical path by means of lenses 13 
and mirrors 2. This apparatus is brought into a ring laser oscillation 
condition by the ring-formed optical path 9 used as a ring-formed 
resonator. As a certain angular speed is applied to this apparatus, there 
is caused a difference in frequency between the clockwise beam and the 
counterclockwise beam as mentioned before. This difference appears as a 
heat signal on the optical output of the semiconductor laser element 10, 
and also appears as a beat signal of the same frequency on the terminal 
voltage of the semiconductor laser element 10. 
Accordingly, this beat signal at terminal 15 can be detected through a 
direct current blocking capacitor 14. 
FIGS. 5 and 6 show further embodiments of this invention. Each of these is 
a semiconductor ring laser apparatus having an optical fiber member 17 in 
the ring-formed optical path formed outside the semiconductor laser 
element 10. In FIG. 5, lenses 13,13 are interposed between the 
semiconductor laser element 10 and the optical fiber member 17 while, in 
FIG. 6, the lenses 13,13 are omitted and the semiconductor laser element 
10 and the ring-formed optical fiber member 17 are directly connected. 
FIG. 7A shows an embodiment of a semiconductor laser element of this 
invention, and FIGS. 7B shows a partial sectional perspective view of the 
semiconductor laser element shown in FIG. 7A. 
Referring to these Figures, the semiconductor laser element 18 has upper 
and lower electrodes 19a, 19b and there are interposed between these 
electrodes 19a,19b an insulation layer 20, a P-type Ga As layer 21, a 
P-type Al.sub.X Ga;hd 1-XAs layer 22, an n-type Al.sub.X Ga.sub.1-X As 
layer (waveguide) 23, an n-type Al.sub.X Ga.sub.1-X As layer 24 and an 
n-type Ga As layer 25 (here X is different in each layer). 
The semiconductor laser element 18 is connected at two electrodes 19a, 19b 
to a driving electric source 12 through a resistance 11 so that a charged 
electric current may flow from the electrode 19a thereinto in the form of 
a ring so as to constitute a ring-formed waveguide 23, and thereby ring 
laser oscillation is effected. 
Also in this embodiment, by applying a certain angular speed to the 
semiconductor ring laser apparatus, there is produced a beat signal of a 
frequency difference between clockwise and counterclockwise beams which 
can be detected from the output terminal 15 through the direct current 
blocking capacitor 14 as a change in terminal voltage of the semiconductor 
laser element 18. 
Thus, according to this invention, when a certain angular speed is applied 
to the semiconductor ring laser apparatus, a beat signal of a frequency 
difference between clockwise and counterclockwise beams is detected as a 
change in terminal voltage of a semiconductor laser element connected to a 
driving electric source. Thus, the need for an optical detector is 
eliminated and an optical system comprising a beam splitter, a lens and 
other members for putting the beams together and an optical path and a 
space for various parts of the optical system can be abolished. Thus, 
there can be obtained practical and extremely excellent semiconductor ring 
laser apparatus which is small in size and weight, low in cost and small 
in number of parts. 
The present invention may be embodied in other specific forms without 
departing from the spirit or essential characteristics thereof. The 
presently disclosed embodiments are, therefore, to be considered in all 
respects as illustrative and not restrictive, the scope of the invention 
being indicated by the appended claims rather than the foregoing 
description, and all changes which come within the meaning and range of 
equivalency of the claims are, therefore, to be embraced therein.