U.S. Philips Corporation

Martinus P Bierhoff

Job F Van Mil

Kornelis A Immink

Franciscus A Schoofs

Albert H Slomp

Gerard E Van Rosmalen

Wilhelm J Kleuters

Peter Coops

Joannes H Sieben

Jacobus P Heemskerk

Adrianus Huibert Hoogendijk

Rudy W Pollen

Dirk C Van Eck

Hilde M Overath

Hubertus M Lonij

Karel M De Decker

A laser power supply control circuit may, when the power supply is initially turned on, temporarily permit an excessive supply voltage which may damage the laser. To prevent that, but without restricting the operating range or speed of response of the control circuit, the invention provides a sensing circuit for deriving a sensor signal indicative of a change in the loop gain of the control circuit when it departs from its normal operating mode. The sensor signal is used to prevent the power supply control signal from increasing excessively after a temporary reduction in supply voltage, but permits the control signal to operate substantially immediately when the supply voltage returns to its normal operating range.

Laser power supply circuit as well as option recording and/or reading

Optoelectronic devices in which optoelectronic components comprising a diode laser are fastened on a carrier plate having good heat conduction, and in which the carrier plate is provided with connection conductors for the components which are separated from the carrier plate by an electrically insulating medium, are used inter alia in equipment for optical reading and/or writing of information carriers such as CD (audio) or CDROM. The known device is comparatively expensive, especially because of the necessity of using a special connector when a flexible connection is desired. According to the invention, the electrically insulating medium comprises a strip-shaped flexible foil which carries conductor tracks, extends over and beyond the carrier plate, is fastened on the carrier plate, and has a void above the carrier plate in which the diode laser is present. As a result, the device has a flexible connection possibility without a special connector being necessary, while in addition--as in the known device--a good alignment, listening, and heat removal of the diode laser are possible. The manufacture and modification of the device according to the invention are also simpler and cheaper. Preferably, the device comprises within the void also a photodiode and a monitor diode, while the components are screened by means of a cover which is fastened on the carrier plate and which comprises a window containing one or several optical gratings. Such a so-called LDGU (=Laser Detector Grating Unit) is particularly suitable for use in the equipment mentioned above. The invention also relates to a favourable method of manufacturing such an optoelectronic device.

Optoelectronic device and method of manufacturing same with an

A current amplifier arrangement in which a current-current converter (30) has an input connected to the input (33) of the current amplifier arrangement and a power supply input (34, 35) to which a current source (51-54) is connected a current mirror circuit (31, 32, 42, 44)has an input connected to the output (36-39) current converter and an output (46-49) connected to the output (50) of the current amplifier arrangement. The current converter includes a first output transistor (T1, T3) whose main current path is arranged between the input (33) and the output (37, 39) of the converter and whose base is connected to the power supply input (34, 36), and a diode-connected driver transistor (T2, T4) connected between the base of the first output transistor (T1, T3) and a node (K) which provides a reference potential during operation. The main current path of a second output transistor (T5, T6) is connected to the output of the arrangement and the base of this transistor is connected to said node. The driver transistor conducts as long as a part of the current supplied by the current source flows through the driver transistor and thereby keeps the second output transistor cut off. When the full current from the current source flows through the base of the first output transistor, the second output transistor can be turned on because the driver transistor is then not conductive. Then the second output transistor can also supply current to the output of the amplifier.

Current amplifier arrangement

The invention relates to a semiconductor device comprising a radiation-sensitive element (A . . . D). The radiation-sensitive element includes a transistor (T) having an emitter region (6), a base region (4) and a collector region (2), and further a radiation-sensitive region (7) having a rectifying junction (5). Due to the presence of the transistor (T), such an element (A . . . D) can supply a considerably larger output signal than a photodiode. On the contrary, however, the first-mentioned element (A . . . D) is comparatively slow as compared with a photodiode due to the parasitic capacitance of the rectifying junction (5). The invention obviates this disadvantage in that according to the invention the radiation-sensitive region (7) has at least a first subregion (71) and a second subregion (72) and the transistor (T) is subdivided into two subtransistors (T.sub.1, T.sub.2), whose base regions (4) are separately connected to the subregions (71, 72). The collector regions (2) and the emitter regions (6) of the subtransistors (T.sub.1, T.sub.2) are interconnected.

Radiation-sensitive semiconductor device having a transistor

A focus control system for optical record carrier scanning apparatus includes a mechanical actuator (13) for moving the focus of the scanning beam relative to a recording layer of the record carrier, a focus-error detection circuit (15, 16, 17) for generating a focus-error signal (FE), and a control circuit (26) for generating a first control signal (AS') for the actuator (13) which is proportional to the focus-error signal (FE). In order to ensure that the actuator is within its generating range when it locks-in to the focus-error signal, the system also includes a lock-in circuit (20) having a signal generator (21) and an integrator (23) for generating an additional control signal (AS') for the actuator (13) prior to lock-in. A lock-in detection circuit (25) generates a lock-in signal (IN FOCUS) when the focus error is in the operation range, which causes a switch (22) to change-over the input to integrator (23) to the focus-error signal (FE) and also enables the control circuit (26) to provide the first control signal (AS'). Thus, after lock-in the integrator (23) and the control circuit (26) constitute a controller for controlling actuator (13) in accordance with both the focus-error signal and the integral thereof. This compensates for low-frequency disturbances and renders the control system more immune to variations in the parameters affecting correct beam focus position.

Beam focus control system for optical record carrier scanning apparatus

A radiation-sensitive semiconductor device, more particularly but not exclusively a photo detection arrangement for determining the postion of a luminous spot, including a semiconductor body having at least two radiation-sensitive diodes and amplifying circuitry for the photocurrent generated by the luminous spot. The amplifying circuitry includes transistors arranged outside the area of the semiconductor body occupied by the radiation-sensitive diodes. Each transistor is assigned to and connected to a radiation-sensitive diode, while at least the active parts of the transistors are arranged more closely to each other in the semiconductor body than the diodes to which they are assigned. A focusing arrangement may advantageously incorporate such as semiconductor photodetector.

Photosensitive semiconductor device having radiation sensitive diodes

A radiation-sensitive semiconductor device comprises a semiconductor body having a first semiconductor region of a first conductivity type, which adjoins with one side a surface of the semiconductor body and adjoins within it at a certain distance from and substantially parallel to the surface a second semiconductor region of a second conductivity type opposite to the first type and forms with it a first pn junction. Such semiconductor devices are used in a reading or writing unit for a system for optical recording, such as CD, LV, DOR and CDV. In one embodiment having a semiconductor region at least two further regions are present, which are located at the surface and each form with the first semiconductor region a further pn junction substantially parallel to the surface and at a smaller distance therefrom than the first pn junction. Moreover, the further regions, like the first semiconductor region, are coupled to reading members, by means of which a current can be measured. As a result, the further semiconductor regions can be thin and can therefore be arranged close to each other so that a focus error signal without a dip is obtained via the reading members coupled to these regions. Since the further regions result in diodes having an inverse polarity, class B amplifiers based on npn transistors may now be integrated in with the semiconductor device so that a separation circuit requiring comparatively large capacitances is no longer necessary.

Radiation sensitive semiconductor device for optical reading or writing

Apparatus for scanning a record carrier having substantially parallel recording tracks, which apparatus includes a position control system with position and velocity feedback for controlling the scanning point toward the center of a track being scanned. Such position control system produces a velocity signal (RS) indicative of the velocity of the scanning point and an error signal (RE) which, within a limited first range to either side of the track center, is proportional to the deviation from the track center. The position control system has a feedback loop which includes a control circuit for controlling the positioning of the scanning point in accordance with the error signal (RE) and the velocity signal (RS), such control circuit generating at least one substitute error signal (PE', UC') when the scanning point deviation is in a second range beyond the aforesaid first range, the substitute error signal having a sign indicative of the direction of such deviation. The control circuit provides the velocity signal (RS) and a position control signal in the feedback loop in response to either the error signal (RE) or the substitute error signal (UC', PE'), depending on whether the deviation is within the first range or the second range. The velocity control signal (RS) is independent of the magnitude of the scanning point deviation.

Record carrier scanning apparatus with feedback control system for

In a multi-track record carrier the data is stored in words which comprise an increased number of smybols as a result of added redundancy. In order to neutralize so-called burst errors, the symbols of a word are stored in a distributed manner, for example by interleaving. In the case of loss of track, a regrouped word may then actually consist of parts of two or more different words (i.e. words situated on several tracks). Decoding of such a word is prevented in practice in that a series of symbols are invalidated in the case of loss of track, for example by inversion or by means of an invalidity flag.

Record carrier decoder for multi-track data patterns including error

An apparatus is described for reading an optically readable record carrier, in which apparatus various control signals are derived from signals obtained by sampling the signals supplied by two optical-detector halves with the bit frequency both during the intermediate areas and the pits, the samples taken during the pits being processed separately from the samples taken during the intermediate areas. Preferably, only one sample is taken for each pit and each intermediate area, namely only if the pit or intermediate area is longer than a specific number of clock periods.

Apparatus for reproducing information from an optically readable record

An apparatus for reproducing information in the form of one or more information blocks in the track of a record carrier, for example a compact-disc digital audio player, is equipped with a memory having n storage locations for storing in each of these storage locations one sequence number corresponding to an information block (if present) whose beginning is situated in a portion of the record carrier corresponding to each storage location, where n&lt;99, and first means for the storage of or containing data relating to the size and the location of the portions on the record carrier, or for the storage of or containing data from which the size and the location of the portions on the record carrier can be derived. Suitably, n is not greater than 10. By means of such an apparatus searching for a following track number that has been selected can be effected more rapidly.

Apparatus for rapid reproduction of information from a record carrier

A D/A converter providing a binary weighted series of currents (I.sub.3, I.sub.4, I.sub.5) via first current-source transistors (T.sub.3, T.sub.4, T.sub.5) each in a given ratio to a reference current (I.sub.1) in a reference transistor (T.sub.1). The weighted currents are switched to analog output (15) or to positive supply terminal (20) via first switching devices (3.1, 3.2, 3.3). A control device includes a second current-source transistor (T.sub.8) connected to a reference-current source or to the positive supply terminal via a second switching device (4). The current (I.sub.8) in the transistor T.sub.8 has a given ratio to the reference current (I.sub.1). By connecting the second current-source transistor to the positive supply terminal or to the reference current source, the reference transistor carries the full reference current (I.sub.ref) from the reference current source or only a fraction of the full reference current, respectively. As the weighted currents are in a given ratio to the current (I.sub.1) in the reference transistor, these currents are a similar fraction smaller in the first case than in the second case. By increasing the reference transistor current (I.sub.1) stepwise from a fraction to the full reference current over the range of the digital input code, the converter output current range will also vary stepwise.

Digital/analog converter having a switchable reference current

Apparatus for reading a disc-shaped record carrier with a light beam. A radial positioning apparatus controls the radial position of the light beam spot on the information track of a record carrier. A lock-in system is provided for switching the radial positioning apparatus into a tracking mode when the light spot is positioned to coincide with the information track. The direction of relative radial movement between the light spot and the information track is detected and a first control signal is supplied to initiate radial tracking of the information track when the relative radial movement between the reading beam and the information track changes from an outward movement of the light spot over the track to an inward movement of the light spot over the track. At the instant the transition occurs, the radial positioning apparatus is enabled to permit the read spot to follow the information track.

Apparatus for enabling an autotrack circuit of an optical disc reading

For detecting whether an input signal is above or below a reference level in such a way that brief signal interruptions and negative spurious pulses are not interpreted as decreases below the reference level, the detector includes an input comparator, a first delay circuit, a second delay circuit and an output circuit. The first delay circuit comprises a first integrator comprising a first transistor and a first capacitor, a first current source and a second comparator. The second delay circuit comprises a second integrator with a second transistor and a second capacitor, a second current source and a third comparator. The first delay circuit and the second delay circuit have equal delay times. In order to ensure that during detection of a decrease below the reference level a positive spurious pulse is not interpreted as an increase above the reference level a third Transistor connects a third current source in parallel with the first current source of the first delay circuit when the input signal lies below the reference level, so that the delay time of the first delay circuit becomes smaller than that of the second delay circuit.

Signal level detector for compact disc player

An apparatus for playing optical discs is described, in which for a smoother locking-in of the focus servo control the focussing error signal is initially derived from the amplitude of the h.f. signal, followed by a gradual change-over to a difference signal derived by means of subdetectors. In this way the focus control point with the servo loop closed is shifted towards the desired in-focus point.

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Eindhoven, Netherlands

Martinus P Bierhoff