JPS59201239A - Optical information signal reproducing device - Google Patents

Abstract

PURPOSE:To simplify the constitution of an optical system and reduce the cost by holding the oscillation wavelength of a semiconductor laser constant by a waveform control loop which uses an optical filter having such a transmission characteristic that light varies sharply in transmittivity to the optical wavelength. CONSTITUTION:When the oscillation wavelength of the semiconductor laser 2 is made smaller than a specific value lambda1 owing to, for example, a drop in room temperature, the mode of projection light from a filter PF1 which has transmission characteristics as shown by a curve A is asymmetric about a horizontal axis as shown by a curve 5. A filter PF2, on the other hand, has modulation characteristics as shown by a curve B. Therefore, the synthetic modulation mode of the filters PF1 and PF2 to laser light is asymmetric on a horizontal axis as well. Such a signal is extracted by a filter 14 and detected by a detecting circuit 15 to generate a DC component. The DC component is supplied to a Peltier element 13, which is heated, so that the wavelength of the laser light returns to lambda1. Thus, the oscillation wavelength of the laser is held constant by the simple constitution of the optical system.

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a semi-groove groove used as an optical i' track, which is aligned with the signal side of a recording medium in which an information signal is recorded in two directions. Body laser is +5 3'+'; , +
j,,! ! An optical device that is designed to emit a spot of light with a minute diameter by intersecting it and regenerate the l'7 T'A signal by attaching it to the reflected light from the No. 11 surface. Relating to an information signal reproducing device. (Prior art and problems) Light from a semiconductor laser used as a light source is directed to a signal surface of a recording medium having a signal surface on which information is recorded using a condensing lens. Optical information (-
It is well known that various types of code reproducing devices have been proposed in the past. By the way, in the optical information (Ij ++i generation device) marked il, the light used to read out the information signal from the signal surface of the recording medium forms a spot of light with a minute diameter on the signal surface of the recording medium. The light must be condensed, but since the surface of the recording medium cannot remain perfectly flat during reproduction, it has traditionally been the case that the condenser lens and
]π-cass times to ensure that the distance from the i4 surface is always maintained at a predetermined value! The prefectural light beam/lens is driven and controlled by the A thread so that the spot of light used for reading out the information signal is always formed into a small diameter spora l~ of light. Then, the focus control (′
Various types of ti'ff have been produced for the I and II series, and the applicant's company also uses optical filters, interference filters, etc. in the system. j) M for various types of Fluorukas K Q41
Focus with better performance than the system? li'J O series j
;'4 'f N
Main device (('IJ え J'J':, 4':? 14:!
UQ 57-! G 71464j (see official seal). Now, in the optical information signal reproducing device, -

[These light sources are 7 IL conductor lasers, but in order to keep the output constant even with temperature changes, as in the case of l'U and IJ, I'm sorry for the f14, but the semiconductor laser is ・T: Reno I G 4I
; 4 Te (+S): 12 conversion occurs. pQ's 1 ('Cow equipment is - to cold J3) and Shin]'s J; there are already 1 Shikawa's talent, so civil stirrups. 5::3 as υ! Uses 3 optical (-1 reward number reproducing equipment ``l light source (, 50'' also for the semiconductor laser used)
It is necessary to take into account the change in degree from C to 4t. In order to keep the light output from the semiconductor laser constant even when the temperature changes, the light output from the rear shearing surface of the semiconductor laser is photoelectrically converted and the output is automatically controlled! However, the increase in drive current 1. Compensating the output in this way will cause a rise in the temperature of the semiconductor I-nozer, which will shorten the blue-white period of the semi-groove laser, and in the worst case will destroy the semi-groove laser. The implementation of the control is preferable (J). Also, in a semiconductor laser, the oscillation wavelength changes depending on the change in the L claw, so for example, G a A ],
The change in oscillation wavelength due to temperature change during single-axis mode oscillation of the As laser is 0.2 to 0.3 nm on average per degree change of 1° C. due to mode shift. As mentioned above, if the fluctuation of the oscillation wavelength in a semiconductor laser is 0.2 to 0.3++ m per 1°C, even if the ambient temperature changes by only ±10°C, the fluctuation of the oscillation wavelength will be is 2 to 3 nm, but such a change in the oscillation wavelength is due to the detection operation of the focus error detection system, which includes an interference filter with a relatively narrow operating wavelength range in the optical system. Sometimes things become impossible. Therefore, in an optical information signal reproducing device using a semiconductor laser as a light source, semiconductor 7. It is necessary to create a wavelength control system that can control the oscillation wavelength of the B-11-ray to always be constant, and the applicant company has previously proposed the following.
(Configured to automatically control the oscillation wavelength of the semiconductor laser to a constant value) '6 Scientific information (No. 3 reproducing device τ, 4)
-Y4 Showa 57-], 79962 special i:'F j-+
'+ is performing an ode. However, the previously proposed light? F4:i
In the No. 1 playback device, an optical isolator is provided in the optical path of 111 between the signal plane of the recording member, such as the semiconductor laser used as the light source, and the polarizing prism and the 1/47th skin. Since J(twa) is (1"), the value is p; and the balance of F!'!i degree of both the transmitted light and the reflected light of the interference filter is Since the oscillation wavelength is controlled by , it is necessary to arrange and use two light-receiving elements, which also creates a problem that the optical system becomes complicated. (Problem (Means for deciding points)
In the meditative writings that are written (for i7, d11,
The half beam γ body used as a ``b source'' is projected from the 1 noser to the spot of the rental car (-) 6 using a condensing lens, and the light is reflected from the signal surface. (The signal can be regenerated to the bond based on the four-dimensional/TJ
This is a signal reproducing device that uses an IJ knee body laser used as a light source and a light r(i
There is a 41 degree angle between the two optical filters, and the optical filter with the same transmittance (+t) in which the light transmittance gently changes with respect to the change in the wavelength of the light, and the optical filter described above. r-th converting means that receives the transmitted light or reflected light of the filter and converts it into an electrical signal;
'[The wavelength of the emitted light changes at a predetermined period from time to time.' The heating/cooling means of the semiconductor laser and the semiconductor L included in the output signal from the photoelectric conversion means mentioned above are used to convert the semiconductor 1 described above by a signal corresponding to the wavelength variation of the emitted light of the semiconductor laser.
The present invention provides an optical information signal reproducing device in which the laser is heated and cooled and the wavelength of the emitted light from the semiconductor laser can be controlled. (Example) Hereinafter, optical details of the present invention (11.
The specific contents of the reproducing device will be explained in detail in Xcj''1.
There is a block diagram of the big implementation person, and this first
In the figure, 1 is a half-3-wave laser with a driving current of 11
% special ii 4 shift 6 te 1 hara, and this expulsion is in danger) hara 1
From , a direct current of the required magnitude is generated with a frequency f ( io at y!
The big i! When the current is in the state where the 8 is being sounded, the current is half f. X (, 1, supplied to the laser. Semiconductor A ((laser emitted from laser 2)) is made into parallel light by colliter 1 - lens 3 Jt, while So 1 is applied to optical filter I) is incident on Fl.This optical filter P
FI is constructed by coating a polarizing film b directly on the light incident surface side of a quarter-wavelength crystal sheet a, which is made of quartz crystal. An optical property that has sharp transmission characteristics such as a sharp change in transmittance and transmits only a narrow wavelength range of 3'6, for example, a half-value of several nm to several tens of nm. filter, and this optical filter PFI
operates as an optical isolator. The optical filter PFl described above transmits P-polarized light at an incident angle φ1 and reflects S-polarized light that is orthogonal to the P-polarized light. Optical filter]-'Fl's i! 1 U light IE%
P (lid light transmitted through b is ]/4 wavelength 4; y.
After passing A through A,) 1, it becomes 1 light in a circle as shown by arrow A in the figure, and a spot of light with a large diameter is created by the condensing lens 4 on plane A Lj of solid 5. Focus on J. The reflected light reflected from the signal surface of the recorder body 5, indicated by the arrow in the figure, is circularly polarized in the opposite direction to the circularly polarized light indicated by the arrow A described above. passes through a quarter-wave plate a made of a quartz plate of optical filter I) Fl, becomes S-polarized light, is reflected by a polarizing film b, and becomes S-polarized light again. /
4, the light becomes circularly shaped as shown by the arrow C in the figure, and enters the optical filter PF2 at an incident angle φ2. It is assumed that the optical filters PFI and PF2 described above have the same configuration in case i1 of the embodiment shown in the first diagram, but the optical filter PF1 has a Corresponding to the incident angle φl [7, the wavelength of the light showing the maximum transmittance is assumed to be λ1°C, and the optical filter PF2 has the maximum transmittance corresponding to the incident angle φ2 of the incident light with respect to the deviation. The wavelength of the light showing the rate is λ2, 112
The above-mentioned two-dimensional optical filter PFI, PF
The change characteristics of the light transmittance with respect to the change in the wavelength of the second
Song E in the diagram:'? + A 1 It is as shown in B. In Fig. 2, curve A is the change characteristic of the light transmittance as the wavelength of optical filter PFI changes, and curve 29B is the characteristic of change in light transmittance as the wavelength of optical filter PFI changes. The characteristics of changes in light transmittance are illustrated respectively. In Fig. 2, the horizontal axis is the oscillation wavelength of the semiconductor laser 2, and the vertical axis is the light intensity. In the description of the embodiment, two optical filters P'
Although it is assumed that FI and PF2 have the same configuration, the two optical filters PFI and PF2 used are
As for PF2, the relative relationship of the change characteristics of light transmittance with respect to the change of wavelength of each thing is shown in A in Fig. 2.
, 8 curves, at a wavelength of light where one optical filter exhibits maximum light transmittance, the other optical filter exhibits a wavelength between the maximum and minimum light transmittance. Two optical filters PF1. ．． PF2 is sufficient. The circularly polarized light C emitted from the optical filter PFI and incident on the optical filter at an incident angle φ2 is
The light is converted into linearly polarized light by passing through the quarter-wave plate a at 2, and is applied to the light receiving element 7 through the polarizing film of the optical filter PF2. Note that since the linearly polarized light that passes through the optical filter PF2 is S-polarized light, the actual optical filter PF''2 is arranged so that its incident surface is perpendicular to the plane of the paper. Since it is difficult to make such a diagram, the optical filter I"F2 is shown in FIG.
is illustrated as having a layout different from the actual FM arrangement described above. The light receiving element 7 described above is divided into two parts on the optical axis in a direction perpendicular to the incident surface of the optical filter PF2.
The light-receiving element 7 has two light-receiving parts 7a and 7b.
bz＼Generates an electrical output corresponding to the intensity of the incoming light. Two light receiving portions 7a in the light receiving element 7 described above. Each output signal from 7b is applied to an adder 8 and a subtractor 9, and the output signal from the adder 8 is applied to an output terminal 10,
4, which is used to extract the signal component of frequency fo. The signal sent to the Z-tuplet 10 described above is reproduced as an information signal in an information signal demodulation circuit. The output signal of the subtracter 9 is a focus error signal, which is converted into a focus control signal via a characteristic compensation circuit 11 and supplied to the actuator 6. Further, the signal component of the frequency fo extracted by the filter 14 described above is applied to the Peltier element 13 after being detected by the detection circuit 15. The detection circuit 15 described above also includes a compensation filter, an amplifier, and the like. In the first embodiment of the optical information signal reproducing apparatus of the present invention having the above-described configuration, when the signal plane of the recording medium 5 leaves the focal plane of the condenser lens 4, the signal of the recording medium 5 The reflected light from the surface is condensed! Since the light beam transmitted through Nonzu 4 enters the optical filter PF2 as a light beam in a state of divergence, the optical filter P
The transmittance of light on both sides of the optical axis at F2 changes inversely to each other, causing a difference in the output signals from the two light receiving sections 7a and 7b of the light receiving element 7, which causes the optical information signal reproducing device to focus An error detection operation is performed, and the operating principle of such a focus error detection operation is also described in detail in, for example, Japanese Patent Application Laid-Open No. 167146/1983, so please refer to that part. It is good to be treated. In the optical information signal reproducing device shown in FIG. The semiconductor laser 2 is assumed to be in a state of being intensity modulated by fo.
Since the magnitude of its driving current changes with the frequency fo on the time axis, the wavelength of the laser light emitted from it also changes with the frequency fo at time @, m according to the change in the driving current. It has become a hot topic. Therefore, semiconductor laser 2 → collimating lens 3 → optical filter PFI → optical lens 4 → recording medium 5 → condensing lens 4 → optical filter PFI → optical filter r-'F
2 → Photodetector 7 → Adder 8 → Filter 14 → Detector 15 →
The Peltier element 3→semiconductor laser 2 loop constitutes a wavelength control loop for wavelength control. Next, the operation of the wavelength control loop described above will be explained. In the optical information signal reproducing device shown in FIG. 1, the optical filters PFI and PF2 are arranged so that their respective wavelength versus transmittance characteristics are as shown by curves A and B in FIG. Therefore, the optical filter []F1 has maximum transmittance when the semiconductor laser 2 emits laser light of wavelength λ1, and transmits the laser light. By the way, the laser light emitted from the semiconductor laser 2 is
It is modulated by the alternating current component of the frequency fo in the drive current supplied from the drive power source 1 to the semiconductor laser 2, and changes on the time axis as shown by curve (1) in FIG. The light transmitted through the optical filter PFI is modulated at a frequency of 2fo, as shown by curve (2) in FIG. The laser beam emitted from the optical filter PFI is condensed by the condensing lens 4 to create a spot of light with a minute diameter on the signal surface of the recording medium 5, and the light reflected on the signal surface of the recording medium is condensed. The light passes through the optical lens 4 → optical filter PFI and enters the optical filter F2. Since the optical filter PF2 has wavelength versus transmittance characteristics as shown in curve B in Figure 2, it can be assumed that the wavelength of the laser light incident on the optical filter I) F2 is λ1±Δλ. Then, the incident light is subjected to a change i1 as shown in curve ξ1(3) in FIG. 2 by the optical filter PF2. Therefore, half 3! The radiation from the three-body laser 2 is 1,
-The wave of light j is centered at wavelength λ1 and is CΔλt, -j
- When the modulation given to the laser beam by the two optical filters 1) Fl and PF2 is combined, it is the curve (2) in FIG. &u(21:
:, music p+ in l, indicated by U(4) 4 sign and 7 buru. -7, r'i:;Optical filter l'I"] of 2-], 1) The operation of f-"2 is similar to what is called the well-known wobbling or synchronous θ wave. It is something. When the wavelength of the laser light emitted from the semiconductor laser 2 fluctuates up and down by Δλ with the wavelength λ1 as the center as described above, the two optical filters PFI and PF2 described above change the wavelength of the laser light. The overall modulation pattern obtained is vertically symmetrical as shown by curve (4) in FIG.
Even when the signal shown by curve (4) in the figure is extracted by the filter 14 and detected by the detection circuit 15, no DC component is generated, and the Peltier element 13 is supplied with operating power. Never. The extremely small Peltier element 13 with an output of about 1 watt is
It is bonded to the semiconductor laser 2, and when operating power is supplied to it, the entire case of the semiconductor laser 2 is cooled or heated. The state in which no power is applied is when the semiconductor laser 2 oscillates a laser beam with a wavelength λ1 of maximum transmittance in the optical filter Pi"1 with f, L <. Then, the oscillation wavelength of the semiconductor laser 2 is If, for some reason, the wavelength λ1 deviates from the wavelength λ1 described above, the wavelength control loop described above performs a wavelength control operation such that the oscillation fatigue length of the semiconductor laser 2 is automatically returned to the wavelength λl, and the wavelength control loop of the semiconductor laser 2 For example, if the oscillation wavelength of the semiconductor laser 2 becomes shorter than λ1 due to low room temperature, the optical filter 1)
The f5j production point of the laser beam incident on Fl is the song &amp;
? In order to move from the top point to the left-hand slope of the wavelength vs. transmittance characteristic curve of the optical filter I, denoted by tA), in this state the optical filter I)F
The mode of encroachment of the laser light emitted from L is shown by a vertically asymmetrical waveform as shown by curve (5) in FIG. On the other hand, since the modulation characteristics of the optical filter PF2 do not change even with the change in the wavelength of the laser beam, the optical filter I·F 1 is suitable for the laser beam. &? of overall modulation of PF2? tη is the first; (5) and curve (3), but since it is vertically asymmetrical to curve (5) and curve (p), such a signal is filtered by γ ,)■
4, and when it is detected by the detection circuit 15, a DC component is generated. By supplying the above-mentioned DC component to the Peltier element 13 as its operating power, the Peltier element 13
is heated, the oscillation wavelength of the semiconductor laser 2 is lengthened, and the wavelength of the laser light is returned to λ1. Contrary to the above case, if the oscillation wavelength of the semiconductor laser 2 becomes longer than λ due to a rise in room temperature, for example, the operating point of the laser light incident on the optical filter PFI will be the curve shown in Figure @2. Optical filter PF shown in A
In order to move from the top point in the wavelength versus transmission characteristic curve A of I to the right slope, the optical filter P
The bad modulation ladder of the laser light emitted from F1 is shown by a vertically asymmetrical waveform, as in the case described above. On the other hand, since the modulation characteristics of the optical filter PF'2 do not change even with the change in the wavelength of the laser beam described above, the optical filter P Fl in the laser beam. The overall modulation mode of PF2 is also vertically asymmetrical, as in the case described above, and this effect is reflected in the filter 14.
When it is detected by the detection circuit 15, a DC component is generated. Then, by connecting the above-mentioned direct current to the Peltier element 1:'I as a force for each operation, and using it as a forceps, the Veltier face plate 13 has a cooling force of 11 tons. So, half-drinking (1
:1 no 4! 12'5;: ! ! ! The wavelength power is reduced and one skin length of the laser beam is returned to λ1. In this way, in the optical fiber re-equipped skin of the present invention, the light transmittance for the wavelength of 6 is reduced to 1 momme, so that only light of a narrow range of wavelengths is transmitted. The wavelength control operation performed by the above-mentioned wavelength control TLL loop, which is designed to make it possible to skillfully utilize the characteristics of optical filters that control the transmission characteristics of semiconductor lasers. Therefore, the oscillation wavelength of 2 can always be maintained at the predetermined wavelength λ1. Figure 3 shows the relationship between the wavelength control gain and the focus control gain, as well as the frequency qf of the exchange meeting of the drive itJ signal containing the information signal.
This is a diagram illustrating the 1!1 staff such as o, etc., and this third
In the figure, the 0 position on the horizontal axis is the position of the fundamental frequency of rotation of the recording body. In FIG. 3, the wavelength control gain is shown to be set lower than the focus control gain by a difference of 3 days or more, but this is because the semiconductor laser 2
The period of the disturbance that disturbs the oscillation wavelength of is quite long, and 21
This is because the time constant determined by the output of the Peltier element 13 is also sufficiently large due to the thermal capacity of the case of the J-body laser 2 and the like. In addition, the frequency [o] of the exchange of the drive current sent from the drive power supply 1 to the semiconductor laser 2 is determined by the frequency range of the focus control gain-circular transfer characteristic and the frequency range of the information signal as shown in the third figure. By setting it so that it is placed between the focus control system signal and the information signal, the influence of both the focus control system signal and the information signal on the modulation operation due to the above-mentioned drive current exchange is minimized. Contrary to the above, it is also possible to prevent the effects of the afiltration exchange meeting from affecting the focus control system signals and information signals. In the optical information signal reproducing device shown in Fig. 1, the conditions under which the automatic control system for the oscillation wavelength of the semiconductor laser can start operation are as shown in Fig. 2, which shows the wavelength versus transmittance characteristics of the optical filters PF1 and PF2. This is when the wavelength of the laser light emitted from the semiconductor laser exists in the range of the slope of the track 1%B in the overlapping portion of the tracks mA and B shown in . FIG. 4 is a diagram showing another embodiment of the optical information signal reproducing apparatus of the present invention, and the optical information signal reproducing apparatus shown in FIG. The information signal reproducing device includes a recording signal source 16 and a changeover switch 17.
18, a comparator 19, and an alternating current signal generator 20, the optical information signal enables a good focus pull-in operation and also enables an information signal recording operation. This is a reproducing device (optical information signal recording and reproducing device), and the optical information signal reproducing device shown in FIG. In a state in which the movable contact V of the switch 18 is switched to the fixed contact Ca side, the configuration is the same as that of the optical information signal reproducing device shown in FIG. It is possible to perform a reproducing operation similar to that of the optical information signal reproducing apparatus shown in FIG. When the optical information reproducing device No. 44 shown in FIG. In addition, the movable contact V of the changeover switch 17 is switched to the fixed contact r side, and the recording signal to be transferred from the recording signal source 16 to the recording medium 5 and the frequency f for changing the wavelength of the laser beam are transmitted from the recording signal source 16 to the recording medium 5.
The signal superimposed with the alternating current signal of o is given to the semiconductor laser 2 as a drive signal, but before a recording operation is performed in the optical information signal reproducing device, the changeover switch 18 is The movable contact V and the fixed contact c
b side, and supplying the AC signal generated by the AC signal generator 20 to the Beltier FI3 13 via the fixed contact cb and the movable contact V of the changeover switch 18,
By heating and cooling the semiconductor laser 2 at the cycle of the alternating current signal described above, the wavelength of the laser light emitted from the semiconductor laser 2 is set to 1. The above-mentioned wavelength is oscillated by the cycle of the above-mentioned alternating current signal within a frequency range that includes a predetermined wavelength λl showing the maximum transmittance in the optical filter PFI provided in the wavelength control loop. To quickly bring a control loop into a state where it can perform control operations. The AC 4n generator 2o described above is, for example, a triangular wave or a stop! (waves, or other suitable waveform alternating current (uG) is generated, and it is supplied to the semiconductor laser 2 by directing it to the irradiated wave. The movable contact V of the switch 18 is switched to the fixed contact cba, and the alternating current signal generated by the alternating current signal generator 2o is passed through the fixed contact cb and the movable contact V of the switching switch 18. Semiconductor laser 2
is heated and cooled by the AC signal loop 1 described above, so that the wavelength of the laser light emitted from the semiconductor laser 2 becomes
When the frequency range including the predetermined wavelength λ1 is fluctuated by the cycle of the AC signal described above, the wavelength of the laser light emitted from the semiconductor laser becomes the predetermined wavelength λ1.
However, when the wavelength of the laser light emitted from the semiconductor laser matches the predetermined wavelength λ1, the laser light emitted from the semiconductor laser passes through the optical filter PFI. The signal surface of the recording medium 5 is irradiated, and the resulting reflected light from the signal surface of the recording medium 5 is transmitted to the condensing lens 4 and the optical filter PF1.
．． ．． Since the light is supplied to the light receiving element 7 via the PF2 etc., a large output is cursed to the output side of the adder 8, and the resulting output of the comparator 19 causes the movable contact V of the changeover switch 18 to become a fixed contact. By being switched to the C'a side, the wavelength control loop described above can perform the wavelength control operation as explained with reference to FIG. When an information signal is recorded on the recording medium 5 by irradiating a laser beam, the semiconductor laser 2 uses a high-output laser beam, compared to the case where the information signal is read by irradiating the recording medium 5 with a laser beam. Therefore, the semiconductor laser 2 of the optical information signal reproducing device during the recording operation generates more heat than the semiconductor laser 2 of the optical information signal reproducing device during the reproducing operation. I'm in love with you. Therefore, when the optical information signal reproducing device is in an overhang state to perform a recording operation, it is preferable that the semiconductor laser 2 is cooled by the Peltier element 13. Also,
The platform where the optical information signal reproducing device is changed from the regeneration operation mode to the recording operation mode receives an AC signal from the AC signal generator 20 described above, which is used to enter the wavelength control operation prior to the recording operation. The fluctuation of the laser oscillation wavelength due to the cooling period can be made to start from a cooling period, or by applying a DC bias voltage to an AC signal, a signal whose cooling period is longer than that of a Peltier signal can be used. It may also be done to provide the element 13 with the same voltage. FIG. 5 shows a method for detecting the convergence state of the condenser lens that is different from the method for detecting the convergence state of the condenser lens used in the optical information signal reproducing apparatus of the present invention described with reference to FIGS. 1 and 4. 5 is a block diagram showing an optical information signal reproducing apparatus according to another embodiment of the present invention, in which a cylindrical lens 21 is used to detect floor light by an astigmatism method. The convergence state of the lens is detected. Now, in the optical information signal reproduction Hm shown in FIG. If a filter 22 that can extract 2fO is connected, a signal with a frequency component of 2fO is extracted from the filter 22. The frequency component of 2fo described above is the laser light emitted from the semiconductor laser 2 by the driving current of the frequency Qfo supplied from the F5 dynamic power source 1 to the semiconductor laser 2, as already described with respect to the embodiment shown in the first figure. As a result, the intensity of the light emitted from the optical filter PF4 fluctuates at the frequency 2fo, as shown by curve (2) in FIG. 2, due to the fluctuation of the wavelength. In the optical information signal reproducing apparatus shown in FIG.
3 as one of its input signals, and
As the other input to the multiplier 23 described above, a signal component of the frequency fO is applied from the drive source 1. The signal of the frequency fo given to the multiplier 23 from the driving source 1 is a signal having the same frequency and the same phase as the signal shown in curve (3) in FIG. Therefore, the signal obtained as the output of the multiplier 23 is the second
A signal that is the product of the signal shown in curve i (2) in the figure and the signal shown in curve (3) in FIG. 2, that is, curve (4) in FIG. The signals (synchronously detected signals) shown in (5) are obtained. Therefore, in the optical information signal reproducing device shown in FIG.
The optical information signal reproducing apparatus shown in FIGS. 1 and 4 performs a synchronous detection operation using the wavelength versus transmittance characteristics of the optical filters PFI and PF2 as described above. 2. Instead of creating a signal that is the product of the signal shown by curve (2) and the signal shown by curve (3) in Fig. 2, the multiplier 23 performs a synchronous detection operation, 2 The signal shown by curve (2) in Figure 2 and the signal shown by curve (2)
This creates a cross-over of the product with the signal shown in 3). Therefore, if the output signal from the multiplier 23 is detected by the detector 15 and applied to the Peltier element 13, in the optical information signal reproducing apparatus shown in FIG. PFI → condenser lens 4 → recording medium 5 → condenser lens 4 → optical filter PFI → cylindrical lens 21 → light receiving element 7 → adder 8 → filter 22 → multiplier 23 → detector 15 → Peltier element 13
→The loop of the semiconductor laser 2 constitutes a one-cycle wavelength control loop for wavelength control. Therefore, the laser light emitted from the semiconductor laser 2 always has a wavelength that is the maximum transmittance of the optical filter PFI. automatically controlled to match the wavelength that indicates the rate. FIG. 6 is a block diagram showing another embodiment of the optical information signal reproducing device of the present invention. In the optical information signal reproducing device shown in FIG. When the light enters the optical filter PF1, the reflected light generated on the incident surface of the optical filter PFI is converted into a C electric signal by the light receiving element 24, and the polarity of the output signal of the light receiving element 24 is inverted by the inverter 25. Then, the AC signal component of the frequency fO is applied from the drive power source 1 to the multiplier 23, and the multiplier 23
synchronous detection is performed. In other words, among the laser light incident on the optical filter PFI, the light reflected on the incident surface of the optical filter PFI is complementary to the light transmitted through the optical filter PFI, but 6. As in the illustrated device, the reflected light on the incident surface of the optical filter PFI is converted into an electrical signal by the light receiving element 24, the polarity of the output signal of the light receiving element 24 is inverted by the inverter 25, and then applied to the multiplier 23, Furthermore, if the driving power supply 1 supplies an AC signal component of frequency fO to the multiplier 23, the multiplier 23 can transmit the signal to the multiplier 23 in the optical information signal reproducing apparatus shown in FIG. The output is similar to that of . Moreover, in the optical information signal reproducing device shown in FIG.
Semiconductor laser 2 → collimating lens 3 → optical filter PFl → light receiver 24 → inverter 25 → rice 1h unit 23
→Detector I5→Bertier element': f13→Semiconductor laser 2
The loop for wavelength control is one round of wavelength control loop hair (
As a result, the oscillation wavelength of the laser beam emitted from the half-light laser 2 is automatically controlled to match the wavelength λ1 showing the maximum transmittance in the optical filter PFl. In Part 7, we will discuss curve C showing the relationship between the intensity of the laser light emitted from the semiconductor laser 2 and the drive current supplied to the semiconductor laser 2, and the optical curve C to which the laser light emitted from the semiconductor laser 2 is applied. ) and the wavelength versus transmittance characteristic A of Ilter PFI are shown superimposed. After the thickness of the drive current exceeds the threshold value, the intensity of the laser beam output from the half-body laser 2 increases in proportion to the drive current value, as shown by curve C in FIG. To increase. When the magnitude of the drive current applied to the semiconductor laser 2 changes with the frequency fO, the laser light emitted from the semiconductor laser 2 has both an intensity and a wavelength equal to that of the drive current. Therefore, if the semiconductor laser 2 having the drive current vs. output characteristic as shown in curve C in FIG. 7 is driven with a drive current whose magnitude varies at frequency fO, then Semiconductor laser 2
When the L nozzle light emitted from the curve A in FIG. , C
As is clear from the curfew, the laser light that has passed through the optical filter PFI is in a synchronously detected state. The output signal from 22 and the 6th
Light receiving element 24 according to the illustrated optical information signal reproducing device
Both the output signals from the two are signals that have been synchronously detected once. Therefore, the output signal from the filter 22 in the optical information signal reproducing apparatus shown in FIG. 5 and the output signal from the light receiving element 24 in the optical information signal reproducing apparatus shown in FIG.
Even if it is immediately applied to the detection circuit 15, the required wavelength control signal can be obtained from the detection circuit 15. Note that, as in the optical information signal reproducing apparatus shown in FIGS. 5 and 6, if the signal that has been synchronously detected is sent to the multiplier 23 and synchronously detected again. , the advantage is that the gain of the wavelength control loop is increased. Also in the optical information signal reproducing apparatus shown in FIGS. 1 and 4 described above, double synchronous detection is performed in the wavelength control loop, and the gain of the wavelength control loop is increased. I'm so talented. (Effects) As is clear from the above detailed explanation, the present invention provides light from a semiconductor laser used as a light source to a signal surface of a recording medium having a signal surface on which an information signal is recorded. An optical information signal reproducing device that is capable of reproducing information No. 4rA based on reflected light from a signal surface by projecting it as a spot of light with a minute diameter using a condensing lens, and used as a light source. It is installed in the optical path between the semiconductor laser to be used and the seven-sided surface of the recording medium. Jfl filter 4. The transmittance of light changes sharply as the wavelength of light changes, allowing only light in a narrow wavelength range to pass through.
An optical filter having Y property and transmitted light of the optical filter described above. Or (photoelectric conversion L) means for receiving reflected light and converting it into an electrical signal, and the wavelength of the semiconductor laser emission A1 is predetermined. 1) 111 means for driving a semiconductor laser to drive the '1'-conductor laser so that it changes at time +t* at 1 and at J2; the heating and cooling means for the semiconductor laser described above; Based on the signal corresponding to the wavelength variation of the emitted light of the semiconductor laser included in the output signal from the photoelectric conversion means, the above-mentioned heating cylinder of the semiconductor laser is performed (1) to change the wavelength of the emitted light of the semiconductor laser. Since this method completely eliminates the means for controlling the
Similar to the optical information signal reproducing device of No. 9962, the oscillation wavelength of the semiconductor laser is automatically controlled so that the semiconductor laser can always oscillate a laser beam of a constant wavelength, and it also Optical information signal reproduction 2
Problems with direct lighting, i.e. ≧ used as a light source
An optical isolator provided in the optical path between the 1' conductor and the signal surface of the recording medium is connected to the side optical prism and 1'.
The oscillation wavelength was controlled by the balance between the intensity of the transmitted light and the reflected light of the Chisa filter. In order to achieve this, it is necessary to arrange and use two sets of light-receiving elements, and the optical system becomes complicated. By controlling the semiconductor laser at a constant temperature at all times, the oscillation wavelength of the laser light emitted from the semiconductor laser can be kept constant, and a long-life, highly reliable optical information signal reproducing device can be easily provided. It is possible. In addition, in the optical information signal reproducing device of the present invention, the optical filter has a transmission characteristic in which the light transmittance sharply changes in response to a change in the wavelength of the light, and only light in a narrow wavelength range is transmitted. For example, by using an optical filter with sharp transmission characteristics, such as a half-maximum distance of several nm - several + 1 m, a wavelength control loop is created so that the semiconductor laser oscillates at a wavelength that exhibits its maximum transmission convexity. Since the optical information signal reproducing apparatus is formed into a groove, the optical information signal reproducing apparatus can be easily made smaller and lighter, and the cost of the optical information signal reproducing apparatus can also be easily reduced. Furthermore, in the optical information signal reproducing device of the present invention, since the oscillation wavelength of the semiconductor laser is held constant, mode popping noise does not occur, and compared to the case where wavelength control is not performed, the oscillation wavelength of the semiconductor laser is kept constant, and the noise An improvement in S/N can be achieved, and therefore, the present invention can easily provide an optical information signal reproducing apparatus suitable for recording and reproducing video signals that require a high S/N. In addition, in the optical (1°1 information and reward generation device) of the present invention, an interference filter is arranged in the optical path of the reflected light from the signal surface of the recording medium, and one of the transmitted light and the reflected light of the interference filter is disposed. (The present invention may be implemented by constructing a device that can perform wavelength control operation using a wavelength control device.

[Brief explanation of drawings]

Figures 1, 4 and 5] Figures 6 and 3 respectively show block diagrams of embodiments of the optical information signal reproducing device of the present invention. The figure and FIG. 7 are waveform openings for explanation.

Claims (1)

[Claims] 1. Light from a semiconductor laser used as a light source is focused on a signal surface of a recording medium having a signal surface on which an information signal is recorded, using a condensing lens to convert the light into a small diameter light beam. An optical information signal reproducing device that projects a spot and reproduces an information signal based on reflected light from a signal plane. An optical device that is installed in the optical path between the signal plane of the a photoelectric conversion means that receives the transmitted light or reflected light of the optical filter and converts it into an electrical signal, and the wavelength of the emitted light of the semiconductor laser changes on the time axis at a predetermined period of 9. a semiconductor laser driving means for driving the semiconductor laser such that the semiconductor laser is heated and cooled;
The semiconductor laser is heated and cooled by a signal corresponding to the wavelength variation of the emitted light of the semiconductor laser, which is included in the output signal from the photoelectric conversion means, and the wavelength of the emitted light of the semiconductor laser is controlled. an optical information signal reproducing device 2, comprising a polarizing film having a characteristic capable of transmitting only one plane-polarized light and reflecting plane-polarized light orthogonal to the plane-polarized light; The optical information signal main device 3 according to claim 1, which uses an optical filter configured by attaching a 174-wavelength plate to a recording medium having a signal surface on which an information signal is recorded. Light from a semiconductor laser used as a light source is projected onto the signal surface as a tiny spot of light using a condensing lens, and an information signal can be reproduced based on the light reflected from the signal surface. This optical information signal reproducing device is installed in the optical path between a semiconductor laser used as a light source and a signal surface of a recording medium. An optical filter that has a transmission characteristic in which the light transmittance sharply changes in response to a change in the wavelength of light and only transmits light in a narrow wavelength range, and the transmitted light or reflection of the above-mentioned optical filter. A photoelectric conversion means that receives light and converts it into an electrical signal, and a semiconductor laser that drives the semiconductor laser so that the wavelength of the emitted light from the semiconductor laser changes at a predetermined period on the time axis. a driving means;
The semiconductor laser is heated and cooled by the heating and cooling means for the semiconductor laser and a signal corresponding to the wavelength variation of the emitted light of the semiconductor laser, which is included in the output signal from the photoelectric conversion means. means for rubbing so that the spread of laser radiation is controlled (:!
In the above optical information signal reproducing device, a change in the wavelength of the light occurs during the optical transmission to the photoelectric transformer (means) for receiving the transmitted light of the optical filter and converting it into an electric eraser. The above-mentioned optical filter has transmission characteristics such that the light transmittance changes Q sharply and only transmits light in a narrow wavelength range. The optical information signal reproducing device 4 is provided with an interference filter whose transmittance is set to have an intermediate value between the maximum value and the minimum value (ri), and is capable of transmitting one plane polarized light. A special claim using an optical filter constructed by covering 1/4 of the 1/4 fr]it light with characteristics that can reflect plane polarized light perpendicular to the plane polarized light that is perpendicular to the plane polarized light that is Range of the optical information signal Isuruga 5 described in item 3, the signal surface of the recording medium that is f′j from the signal surface on which the information signal is recorded, as a light source. From J) L is emitted as a spot of light with a microscopic diameter on the focal light l nons, and information is reproduced based on the anti-11 light from the l+ + (J) plane 7p and others. The optical information signal reproduction system that is designed as The transmittance of light changes sharply as the light wave J changes, resulting in a narrow wavelength J・1−1c
``11 logical filter, which has transmission characteristics that allow it to pass through the optical filter, and the optical filter '12 jL+
−°L, or receive reflected light and convert it into an electrical signal fρ
The photoelectric conversion r3 means and the semiconductor laser h! 1) The light emitted from the laser beam changes at a predetermined period on the time axis, and 2) the tracer is driven in a single core, the semiconductor laser driving means, and the heating and cooling of the semiconductor laser described above. means for multiplying the output signal from the photoelectric conversion means by the signal given to the semiconductor laser from the semiconductor laser driving means; and heating the semiconductor laser using the output signal of the multiplication means. An optical information signal reproducing device 6 comprising means for cooling and controlling the wavelength of the light emitted from the semiconductor laser 6, capable of transmitting only one plane polarized light, and capable of transmitting only one plane polarized light; The optical information signal according to claim 5 of the scope of claim 51, which uses an optical filter configured by attaching a polarizing film having a characteristic such that it can reflect plane polarized light orthogonal to the 1/7I wavelength plate. Reproducing device 7, the signal surface number on which the information signal is recorded (light, relative to the signal surface on the B medium) Projected as a spot,
An optical information signal reproducing device capable of reproducing an information signal based on reflected light from a signal surface, the optical information signal reproducing device having a t ``': The beam is 4c, and in line with the change in the wavelength of light, the light family 30 changes slowly and transmits light of q + wavelength j +, '2 light 4J) 111 times. The optical filter having the characteristics of the above-mentioned optical filter;
−'; Photoelectric conversion y that reduces light reception and converts it into an electrical signal ′, ′, %
'1, E13 i (3, Laser emission j'4.
Since the J light wave J-t is defined as p, I-1, i p, 1
3, so that C changes on time 4111.
Le half H''N body 1/ -Sa (J) l<Nail Hand Q To, :M', iJF, I/ ;5. ;1-7
jjjj 14. □□ Laser addition: 1; "ζ cooling 4:)) means," as described above.16 (7,',)b control'1 Output from the means (J?-W) i Cooling is performed by the addition of the above-mentioned half) by the signal created by the wavelength change 1ll) of the conductor 1-' and 17'/j'+, ir, +; The optical 4.i(2(411 In the code reproducing device, the C, IH!:・",!; During the optical path to the r means, the wavelength of the light is changed to 3.+ and Q, so that the 3.-'2 of the light changes rapidly so that only the light in the desired wavelength range is transmitted. The optical filter described above, which has a transmission characteristic of ¥1, is set at the wavelength of light that exhibits maximum transmittance, and the transmittance is set to a value between 11 and the minimum value. An interference filter is provided, and the transmission y that occurs in the regions on both sides of the optical axis and the plane of incidence is divided according to the expansion 11 of the light incident on the interference filter and the pickup of the vehicle.・Using the signal ♀1[ based on the changes in
Pentological '+;;<'U<, -! The number reproducing device 8 is capable of transmitting only one plane polarized light. The optical information signal described in item 7 of 41 (41) of the optical information signal ( 1st grade equipment