JP3889432B2 - Image display device - Google Patents

Description

  The present invention relates to an image display device typified by a CRT (cathode ray tube) display device, and more particularly to an improvement for improving the image quality of a projected image.

  FIG. 25 is a block diagram showing the internal configuration of a conventional image display apparatus as the background of the present invention. This device 150 is configured as a CRT device having a CRT 91. The image signal Pin input from the outside is amplified to the image signal Pc by the amplifier 92 and then input to the cathode electrode (not shown) of the CRT 91. A parallel circuit of a resistance element 93 and a series circuit including a resistance element 95 and a capacitance element 94 is connected to the input of the amplifier 92, and a resistance element 96 is interposed between the input and the output. . In other words, the conventional device 150 includes an active (current feedback) video amplifier circuit.

  A series circuit of an inductor 97 and a resistive element 98 is interposed between the output of the amplifier 92 and the CRT 91. The gain of the amplifier 92 is defined by the resistances of the resistance elements 93, 95, 96, and 98, the capacitance of the capacitance element 94, and the induction (inductance) of the inductor 97. In particular, the capacitive element 94 and the inductor 97 function to compensate for the high frequency component of the gain. That is, the capacitance of the capacitive element 94 and the induction of the inductor 97 define the frequency characteristics of the gain.

  A high voltage generator 99 is further connected to the CRT 91. The high voltage generator 99 supplies the CRT 91 with a high voltage, thereby enabling the electron beam to be emitted inside the CRT 91. Since the conventional apparatus 150 is configured as described above, the image represented by the image signal Pin is displayed on the screen provided on the front surface of the CRT 91.

  Patent Documents 1 to 3 are known as documents relating to the control of the frequency characteristics of the image amplifier.

Japanese Patent Laid-Open No. 50-68221 Japanese Patent Laid-Open No. 2-312465 JP-A-6-189161

  However, in the conventional device 150, the frequency characteristic of the gain of the image signal Pc is fixed, and the frequency characteristic cannot be arbitrarily changed according to the type of the image. In the conventional apparatus 150, a configuration in which the resistance element 95 is replaced with a semi-fixed variable resistance is also known. However, the resistance value of the resistive element 95 cannot be changed by electrical means. Therefore, the frequency characteristic is adjusted to optimize the visibility (visual image quality) of the image according to the type of the image. It was difficult to do.

  Further, there has been no known technique for controlling the frequency characteristics or the like so as to match the type of image only within a specific range on the screen where a specific type of image is displayed. As described above, the conventional image display apparatus has a problem that it is difficult to obtain an optimum image quality according to the image.

  The present invention has been made to solve the above-described problems in the conventional apparatus, and an image display apparatus capable of optimizing the visibility of an image displayed on a screen according to the image is obtained. Objective.

An apparatus according to a first aspect of the present invention is an image display device having a cathode ray tube for projecting an image represented by an image signal, a variable inductor, and a gain having frequency characteristics based on induction of the variable inductor, An amplifying unit for amplifying an image signal and supplying the amplified image signal to the cathode ray tube; a beam current detecting unit for detecting a beam current of the cathode ray tube; and controlling the induction based on the magnitude of the beam current, thereby controlling the frequency. A control unit that controls characteristics, and a transient characteristic detection unit that detects a pulse waveform of the image signal output from the amplification unit. The control unit controls the frequency characteristics, and the transient characteristic detection unit that close to said detected pulse waveform to a target.

  According to a second invention, in the image display device according to the first invention, the amplifying unit further includes an amplifier that amplifies the image signal, and the variable inductor is provided between the amplifier and the cathode ray tube. Is inserted in the path.

  According to a third invention, in the image display device according to the first or second invention, the variable inductor includes a primary coil and a secondary coil that are inductively coupled to each other, and the primary coil is connected to the amplifier. The secondary coil is connected to the control unit, the induction is induction of the primary coil, and the control unit is configured to generate a current in the secondary coil by a current flowing through the primary coil. By controlling the excited current, the induction of the primary coil is controlled.

  An apparatus according to a fourth aspect of the present invention is the image display apparatus according to any one of the first to third aspects, further comprising a resolution detector that detects the resolution of the image signal based on the synchronization signal of the image, The control unit changes the frequency characteristic depending on the resolution of the image signal.

An apparatus according to a fifth aspect is the image display device according to any one of the first to fourth aspects, wherein the control unit displays the image displayed based on the beam current detected by the beam current detection unit. Is a normal display binary image and whether it is a reverse display binary image. For a normal display binary image, the high frequency component of the gain is strengthened. For the reverse display binary image, the frequency characteristic is controlled so as to be weakened.

In the apparatus according to the first aspect of the invention, since the frequency characteristic of the gain of the amplifying unit is controlled based on the beam current through induction of the variable inductor, the frequency characteristic suitable for the image signal can be easily and electrically set. And an image with good visibility can be obtained. In addition, since the frequency characteristics are controlled so that the pulse waveform of the image signal supplied to the cathode ray tube approaches the target, a visually suitable frequency characteristic is automatically applied regardless of the pulse waveform of the input image signal. Can be realized.

  In the device of the second invention, since the variable inductor is inserted in the path between the amplifier and the cathode ray tube, the amplification unit is realized by replacing the inductor of the conventional device with a variable inductor. For this reason, resources such as design data in the conventional apparatus can be used as they are, and costs required for design and manufacture can be reduced.

  In the device of the third invention, the variable inductor includes a primary coil and a secondary coil that are inductively coupled to each other, and the induction of the primary coil is controlled by controlling the current flowing through the secondary coil. Electrical control of the frequency characteristics can be performed particularly easily.

  In the apparatus according to the fourth aspect of the invention, the frequency characteristic is controlled so as to change according to the resolution of the input image signal. Therefore, a visually suitable frequency characteristic is automatically applied to the resolution of the input image signal. Can be realized.

In the apparatus of the fifth invention, when the image projected on the cathode ray tube is a binary image, the frequency characteristic is appropriately changed depending on whether the image is a normal display or a reverse display. Even if it changes, an image with good visibility is automatically realized.

<1. Embodiment 1>
First, the image display apparatus according to the first embodiment will be described.

<1-1. Configuration and general operation>
FIG. 1 is a block diagram illustrating a configuration of the image display apparatus according to the first embodiment. The apparatus 101 includes a CRT 1 as an image output unit, and an image represented by an image signal Pin input from the outside is displayed on a screen 10 provided in front of the CRT 1. That is, the device 101 is configured as a CRT device.

  The amplifying unit 2 is connected to the cathode electrode (not shown) of the CRT 1. The image signal Pin as a voltage signal is amplified by the amplification unit 2. The amplified image signal Pc is input as a voltage signal to the cathode electrode (not shown) of the CRT 1. The amplification unit 2 is configured as an active (current feedback) video amplification circuit. That is, the parallel circuit of the resistor element 21 and the series circuit including the resistor element 23 and the capacitor element 22 is connected to the input of the amplifier 20, and the resistor element 24 is interposed between the input and the output. ing.

  A series circuit of the inductor 3 and the output resistance element 11 is interposed between the output of the amplifier 20 and the CRT 1. The gain of the amplifying unit 2 is defined by the resistances of the resistance elements 21, 23, 24, 11, the capacitance of the capacitive element 22, and the induction (inductance) of the inductor 3. In particular, the capacitive element 22 and the inductor 3 function to compensate for the high frequency component of the gain. That is, the capacitance of the capacitive element 22 and the induction of the inductor 3 define the gain frequency characteristics. In particular, the induction of the inductor 3 is variable (that is, the inductor 3 is a variable inductor), so that the frequency characteristics of the gain can be adjusted by the inductor 3.

  The inductor 3 includes a primary coil 31 and a secondary coil 32 that are inductively coupled. The primary coil 31 and the secondary coil 32 are preferably inductively coupled through a magnetic material. The primary coil 31 is inserted between the output of the amplifier 20 and the output resistance element 11, and the secondary coil 32 is connected to the control unit 4. The control unit 4 controls the current I of the secondary coil 32 induced by the current flowing through the primary coil 31, that is, the secondary current of the inductor 3, thereby equivalent induction of the inductor 3 in the amplification unit 2, that is, Control induction of the primary coil 31. Thereby, the frequency characteristic of the gain of the amplifying unit 2 is controlled.

  As the inductor 3, the induction of the primary coil 31 can be widely changed by controlling the secondary current, the parasitic capacitance is low, the high frequency characteristics are excellent, the coupling coefficient is high, and the general-purpose product can be obtained at a low price. It is desirable to use a toroidal type common mode choke.

  The control unit 4 includes a current adjustment unit 41 that is connected to the secondary coil 32 and has a characteristic of limiting the current I, and a drive control unit 40 that drives and controls the current adjustment unit 41. The current limiting characteristic in the current adjustment unit 41 is variable and is changed by the drive control unit 40. That is, in the current adjustment unit 41, two (generally, a plurality of) current paths having different current limiting characteristics are connected in parallel. Each of these current paths forms a separate loop that shares the secondary coil 32.

  By inserting the resistance element 44 in one of the current paths, the current limiting characteristics of those current paths are different from each other. In these current paths, switches 42 and 43 that are opened and closed (on / off) in response to a control signal transmitted by the drive control unit 40 are inserted. For the switches 42 and 43, for example, a switching element such as a transistor or a relay is used. When a transistor is used, selection of an element, setting of a value of a control signal, and the like are performed so that the transistor is saturated in an on state.

  For example, the drive control unit 40 realizes three types of current limiting characteristics by closing (turning on) one of the switches 42 and 43 or opening (turning off) both of them. In the case where transistors or the like are used for the switches 42 and 43, the secondary coil 32, the current adjustment unit 41, For example, one end of the secondary coil 32 is connected to the ground (ground) potential or a constant potential. In the latter case, the power supply 13 is connected as shown in FIG. As a result, the current adjusting unit 41 can be configured with a simple circuit.

  On the other hand, a high voltage generator 12 is further connected to the CRT 1. The high voltage generator 12 enables the emission of an electron beam inside the CRT 1 by supplying a high voltage to the CRT 1. A beam current detector (luminance detector) 5 is further connected to the high voltage generator 12. The beam current detection unit 5 detects the beam current J by being connected to the high voltage generation unit 12. The detection signal of the beam current J is converted into a digital signal by the A / D converter 14 and then transmitted to the drive controller 40.

  The drive control unit 40 can be configured only by hardware not equipped with a program, but preferably a CPU (not shown) that operates based on the program and a memory (not shown) that stores the program. Abbreviated). Thereby, the drive control unit 40 can be configured easily. The drive control unit 40 controls the current adjustment unit 41 based on the electron beam current inside the CRT 1, that is, the beam current J.

  Although not shown, horizontal and vertical synchronization signals are also input from the outside simultaneously with the image signal Pin, and scanning of the electron beam of the CRT 1 is performed in synchronization with these synchronization signals. Thereby, the image represented by the image signal Pin is correctly reproduced on the screen 10.

<1-2. Operation of drive control unit>
2 to 5 are operation explanatory views of the drive control unit 40 when a pulsed image signal Pin representing an image of one pixel is input as an example. Such a pulse-shaped image signal Pin represents, for example, a point or a line (for example, a character) in a binary image. If the frequency characteristics of the amplification unit 2 defined by the inductor 3 are different, the waveform of the image signal Pc input to the CRT 1 is different even if the pulse waveform of the input image signal Pin is the same.

  FIG. 2 shows that a pulse-like image signal Pin representing a black character or the like drawn on a white background (a binary image such as a reverse-displayed character / line diagram) passes through an amplifying unit 2 having different frequency characteristics. The two image signals Pc obtained by the above and the luminance obtained by converting them are illustrated. In the image signal Pc1 obtained under the frequency characteristic that emphasizes the high-frequency component, both rising and falling are steep and the peak is high. Further, vibration (ringing) appears before the return to the steady value.

  On the other hand, in the image signal Pc2 obtained under the frequency characteristic that weakens the high frequency component, both rising and falling are gentle and the peak is low. In particular, it takes a long time to return to the steady value. The relationship of T1 <T2 is established between the periods T1 and T2 (that is, the pulse time width) from the rising edge to the return to the low normal value of each of the image signals Pc1 and Pc2. The waveform of the image signal Pc is converted into a luminance waveform based on a gamma characteristic (relationship between cathode voltage and luminance) unique to the CRT 1.

  Since the image signal Pc1 has a lower peak than the image signal Pc2, the luminances B1 and B2 of the image signals Pc1 and Pc2 respectively satisfy B1 <B2. However, the luminance difference (B2-B1) does not appear as clearly as the difference between the peaks of the image signals Pc1, Pc2, as can be understood from the gamma characteristic curve of FIG. In other words, in the reverse display, even if the intensity of the high frequency component is different, a noticeable difference does not appear in the luminance.

  FIG. 3 illustrates an image (for example, a character) expressed by the image signals Pc1 and Pc2. In the example of FIG. 3, the represented image is a line segment along the vertical direction V of the screen 10. The scanning line of the electron beam is along the horizontal direction H, and the image in FIG. 3 is displayed on the screen when the pulse-like image signals Pc1 and Pc2 shown in FIG. 10 is projected.

  A relationship of L1 <L2 appears between the widths L1 and L2 of the images represented by the image signals Pc1 and Pc2. This relationship corresponds to the relationship between the periods T1 and T2, and the widths L1 and L2 respectively correspond to the beam diameters under two types of frequency characteristics. Reflecting the relationship between the luminances B1 and B2, the contrast of the black character with respect to the white background is somewhat stronger in the image signal Pc1 than in the image signal Pc2. However, as noted above, the difference is not noticeable visually.

  In FIG. 4, contrary to FIG. 2, a pulse-like image signal Pin representing a white character or the like (normally displayed binary image) drawn in a black background passes through an amplification unit 2 having different frequency characteristics. The two types of image signals Pc3 and Pc4 obtained by doing so and the luminances B3 and B4 obtained by converting them are illustrated. In the image signal Pc3 obtained under the frequency characteristic that emphasizes the high frequency component, both the falling and rising edges are steep and the reverse peak is deep. Further, vibration (ringing) appears before the return to the steady value.

  On the other hand, in the image signal Pc4 obtained under the frequency characteristic that weakens the high frequency component, both the falling and rising are gentle and the reverse peak is shallow. In addition, it takes a long time to return to the steady value. As in the case of the white background, the relationship of T3 <T4 is established between the periods T3 and T4 of the image signals Pc3 and Pc4 from the rise to the return to the low normal value.

  The luminances B3 and B4 of the image signals Pc3 and Pc4 are B4 <B3, contrary to the case of the white background. Moreover, as can be seen from the gamma characteristic curve of FIG. 3, a slight difference in the depth of the reverse peaks of the image signals Pc3 and Pc4 results in a large luminance difference (B3-B4). That is, in the normal display, even if the intensity of the high frequency component is slightly different, a remarkable difference appears in luminance.

  FIG. 5 illustrates an image represented by the image signals Pc3 and Pc4. The image illustrated in FIG. 5 is the same as the image illustrated in FIG. A relationship of L3 <L4 appears between the widths L3 and L4 of the images represented by the image signals Pc3 and Pc4, respectively, as in the case of the white background, reflecting the relationship between the periods T3 and T4. Further, reflecting the relationship between the luminances B3 and B4, the contrast of the white character with respect to the black background is stronger in the image signal Pc4 than in the case of the white background. Moreover, as described above, the difference in contrast appears prominently in vision.

  Regarding the quality of the visual image quality, that is, the visibility of the image, for the following reasons, the frequency characteristic in which the high frequency component is weakened is desirable in the reverse display, and the characteristic that is enhanced in the normal display is desirable. In the case of reverse display, the contrast between the image signals Pc1 and Pc2 is not visually noticeable. In addition, the image signal Pc1 should not emit light because the width L1 is narrow. An electron beam is also irradiated to a non-existing portion, and a portion of a character that should originally be a dark portion becomes visually unclear. On the other hand, in the image signal Pc2, since the width L2 is wide, it is possible to avoid irradiation of an unintentional part with an electron beam, and a character expressed by a dark part becomes visually clear.

  In the reverse display, the image signal Pc2 in which the high-frequency component is weakened also suppresses the generation of moire fringes resulting from the interference between the grill pitch of the aperture grill (not shown) provided in the CRT 1 and the binary image. Is good. On the other hand, in normal display, there is no fear of the occurrence of moire fringes, and the image signal Pc3 is stronger than the image signal Pc4 so that the contrast is conspicuous. Therefore, in normal display, the image signal Pc3 in which the high frequency component is strengthened is desirable in terms of visibility.

  For this reason, when the image is displayed in reverse, the drive control unit 40 weakens the high frequency component of the gain of the amplification unit 2 by turning off both the switches 42 and 43, for example. On the other hand, when the image is a normal display, for example, by turning on the switch 43, the high frequency component of the gain is strengthened.

  Further, when the image is not a binary image but a multi-value image such as a moving image or a photographic image, the drive control unit 40 can turn on the switch 42 and thereby further increase the high-frequency component. . By emphasizing the high frequency component, so-called contour correction is applied to the moving image and the photograph. By contour correction, the contour of a moving image, a photograph, etc. becomes visually clearer. The relationship between high-frequency component enhancement and contour correction will be described in the second embodiment.

  The drive control unit 40 determines the type of image based on the beam current J. For example, if two reference values are set and the average value of the beam current J over a certain period, for example, the average value for one screen is equal to or lower than the low reference value, the image is a normal display binary image. If it is equal to or higher than the high reference value, it is determined that the image is a binary image for reverse display. Further, for example, if the average value is between a low reference value and a high reference value, it is determined as a multi-value image such as a moving image.

  As described above, since the frequency characteristic of the gain is adjusted based on the type of image, the apparatus 101 can display an image with good visibility regardless of the type of image. In addition, since the frequency characteristic is controlled based on the detection signal of the beam current detector 5, an image with good visibility can be automatically obtained even if the type of the image changes.

  Furthermore, since the inductor 3 with variable induction is used, it is easy to control the high frequency component of the gain, and electrical control is possible. In particular, since the inductor 3 is inserted in the path between the amplifier 20 and the CRT 1, the amplifying unit 2 is completed by replacing the inductor 97 provided in the conventional device 150 with the inductor 3. That is, resources such as design data in the conventional apparatus 150 can be used as they are, and costs required for design and manufacturing can be reduced.

  In addition, since the inductor 3 includes the primary and secondary coils 31 and 32 that are inductively coupled to each other through mutual inductance, the equivalent induction in the amplification unit 2 can be easily adjusted using the current adjustment unit 41. It is possible. That is, the electrical control of the frequency characteristics can be performed more easily. Further, since the current adjustment unit 41 adjusts the current I stepwise only through the on / off operations of the switches 42 and 43, the design of the current adjustment unit 41 is easy. Further, the control by the drive control unit 40 is simple and easy.

<2. Embodiment 2>
FIG. 6 is a block diagram illustrating a configuration of the image display apparatus according to the second embodiment. This device 102 is different from that of the first embodiment in that the current adjusting unit 41 has a single path of current I, and the current limiting characteristic of the path is continuously variable by a transistor interposed in the path. It is characteristically different from the device 101 (FIG. 1). As shown in FIG. 6, for example, a junction FET 45 is used as the transistor. The FET 45 is preferably a depletion type.

  The source S and drain D of the FET 45 are respectively connected to the two ends of the secondary coil 32. A power source 13 is further connected to the source S, so that the FET 45 can operate as a depletion type. The drive control unit 40 sends out a drive voltage signal as a control signal. The drive voltage signal is input as a gate voltage to the gate G through the resistance element 46 connected to the gate G of the FET 45.

  FIG. 7 is a graph showing the relationship between the gate voltage of the FET 45 and the drain-source resistance. The FET 45 is turned off when a sufficiently large gate voltage is applied in the negative direction, and turned on when a sufficiently large gate voltage is applied in the positive direction. In the non-saturation region, which is an intermediate range between the two, the drain-source resistance decreases as the gate voltage increases in the positive direction. Since the range of the non-saturation region also depends on the characteristics (for example, the number of windings) of the inductor 3, the characteristics of the inductor 3 are appropriately selected so that the FET 45 can operate in the non-saturation region. Further, the range of the control signal is also appropriately set so that the FET 45 always operates in the non-saturation region.

  FIG. 8 is an operation explanatory diagram illustrating the relationship between the control signal, the image signal Pc, and the image displayed on the screen 10. As will be described later in the fifth embodiment, it is possible to simultaneously display images having different frequency characteristics on a single screen 10, but in FIG. 8, they are displayed on the screen 10 at different times. Three types of images are drawn in one screen 10 for convenience.

  The drive control unit 40 determines the type of image based on the magnitude of the beam current J. When the image is a moving image or the like, the drive control unit 40 sets the control signal to be the highest in the positive direction, and when the image is a normal display binary image, the drive control unit 40 sets it to an intermediate height, and the image is displayed in reverse Is set to the lowest (largest in the negative direction). As a result, the equivalent induction of the inductor 3, that is, the induction of the primary coil 31, rises in this order.

  Therefore, the high frequency component of the gain is strongest for a moving image or the like, medium for a normal display binary image, and weakest for a reverse display binary image. The preferable relationship among the three types of images regarding the frequency characteristics is as described in the first embodiment, and the relationship of FIG. 8 matches this preferable relationship. Since a high frequency component is particularly strong in a moving image or the like, an overshoot OS and an undershoot US appear remarkably in the image signal Pc. As a result, contour correction in which the contour of a moving image or the like is enhanced is realized. As a result, the outline of a moving image or the like becomes clear.

  In addition, the frequency characteristic for the normal display binary image located in the middle of the three stages is set to the same level as the frequency characteristic in the conventional device 150, that is, the standard frequency characteristic, for example, in consideration of visibility. For moving images and the like, it is preferable that the high-frequency component is emphasized compared to the standard, and the reverse display binary image is weakened.

  As described above, in the device 102, the frequency characteristic of the gain can be changed variously by controlling the gate voltage of the FET 45 inserted in the single path of the current I. In the above example, the frequency characteristic is changed in three stages. However, the drain-source resistance of the FET 45 can be continuously changed with respect to the gate voltage as shown in FIG. Without changing the configuration of the unit 41, the number of steps of the frequency characteristic can be increased without limitation, and can be changed continuously. That is, it is possible to realize finer frequency characteristic control with a simple configuration.

  FIG. 6 shows an example in which the transistor included in the current adjustment unit 41 is an FET 45. However, another type of transistor may be used, and the same function as a transistor that can operate in a non-saturated state is achieved. It is also possible to replace it with an active element. FIG. 9 is a block diagram showing an example. In this device 103, a bipolar transistor 47 is used instead of the FET 45.

  The emitter and collector of the transistor 47 are respectively connected to the two ends of the secondary coil 32. A wiring for transmitting a ground potential, that is, a ground potential line is further connected to the emitter, so that the transistor 47 can operate. The drive control unit 40 sends out a current signal as a control signal. This current signal is input as a base current to the base through the resistance element 48 connected to the base of the transistor 47.

<Third Embodiment>
FIG. 10 is a block diagram illustrating a configuration of the image display apparatus according to the third embodiment. This device 104 is characteristically different from the device 102 (FIG. 6) of the second embodiment in that the current adjustment unit 41 includes a constant current circuit. A series circuit of an FET 60 and a resistance element 61 is inserted in the path of a single current I provided in the current adjustment unit 41. That is, the drain D of the FET 60 is connected to one end of the secondary coil 32, the source S of the FET 60 is connected to one end of the resistance element 61, and the other end of the resistance element 61 is connected to the other end of the secondary coil 32. Yes. A ground potential line is further connected to the other end of the resistance element 61.

  The output of the operational amplifier 62 is connected to the gate G of the FET 60, and the source S of the FET 60 is connected to the inverting input of the operational amplifier 62. That is, a voltage drop generated in the resistance element 61 in proportion to the current I is fed back to the operational amplifier 62. The drive control unit 40 outputs a control signal in the form of a voltage signal, and this control signal is input to the non-inverting input of the operational amplifier 62.

  Therefore, the drain-source resistance of the FET 60 is adjusted by the operational amplifier 62 so that the voltage drop of the resistance element 61 becomes a constant value, in other words, the current I becomes constant. The value of the current I that is constant depends on the control signal. Therefore, the current I can be changed variously and continuously by the control signal.

  For example, even if the characteristics of the FET 60 include non-uniformity, changes with time, changes due to temperature changes, and the like, the current I having a certain magnitude corresponding to the control signal flows through the secondary coil 32. As described above, the device 104 absorbs errors in the characteristics of the elements with a simple configuration, and realizes control of the frequency characteristics with high accuracy.

<4. Embodiment 4>
FIG. 11 is a block diagram illustrating a configuration of the image display apparatus according to the fourth embodiment. This device 105 is characteristically different from the devices 101 to 104 of the first to third embodiments in that a resolution detection unit 70 and a transient characteristic detection unit 71 are provided. In FIG. 11, the current adjustment unit 41 of the device 102 (FIG. 6R> 6) is illustrated as the current adjustment unit 41, but may be replaced with the current adjustment unit 41 of other devices 101, 103, and 104.

  The device 105 is connected to an external device 90 when used. The external device 90 is a personal computer, for example. The external device 90 transmits the image signal Pin and the synchronization signal Sync to the device 105. The image signal Pin includes three types of color components Pin (R), Pin (G), and Pin (B). The synchronization signal Sync includes a horizontal synchronization signal Sync (H) and a vertical synchronization signal Sync (V). Is included.

  The transient characteristic detection unit 71 detects the transient characteristic of the image signal Pc obtained when the image signal Pin passes through the amplification unit 2. The resolution detection unit 70 detects the resolution of the image signal Pin sent from the external device 90 based on the synchronization signal Sync. The drive control unit 40 controls the frequency characteristic of the gain of the amplification unit 2 so as to improve the visibility of the image based on these detection results.

  The synchronization signal Sync is also supplied to a synchronization / deflection circuit (not shown), which is a conventionally known device for scanning an electron beam on the screen 10 of the CRT 1. For this reason, in FIG. 11, the synchronization signal Sync is drawn so as to be branched and transmitted to a path different from the resolution detection unit 70.

  When the image signal is input with a pulse-like waveform representing an image of one pixel and the high-frequency component of the gain of the amplifier 2 is excessively strong, as shown in FIG. Ringing appears. As a result, in the image displayed on the screen 10, image distortion corresponding to ringing appears as shown in FIG. On the contrary, when the high frequency component of the gain of the amplifying unit 2 is excessively weak, as shown in FIG. 14, in the amplified image signal Pc, convergence to a steady value is excessively delayed. As a result, an afterimage appears in the image displayed on the screen 10 as shown in FIG.

  On the other hand, when the frequency characteristic is appropriately set, as shown in FIG. 16, the amplified image signal Pc converges to a steady value at an appropriate speed without ringing. As a result, as shown in FIG. 17, an appropriate image without distortion and afterimage is displayed on the screen 10. The transient characteristic detector 71 detects the pulse waveform of the image signal Pc, that is, the transient characteristic. The transient characteristic is detected by, for example, sampling the image signal Pc at a frequency higher than the clock frequency of the image signal Pin and performing A / D conversion.

  The drive control unit 40 determines how much the transient characteristic is displaced from the target shown in FIG. 16R> 6 based on the digital signal obtained by the transient characteristic detection unit 71, and cancels this displacement. In addition, the frequency characteristic of the gain is corrected through the current adjustment unit 41 and the inductor 3. By repeating this cycle, an appropriate transient characteristic of the target image signal Pc can be obtained regardless of the transient characteristic of the input image signal Pin. FIG. An appropriate image like this is displayed. That is, an appropriate image is displayed without depending on the characteristics of the external device 90 and the characteristics of the wiring connecting the external device 90 and the device 105.

  It is more desirable that the targeted transient characteristic is changed depending on the resolution of the image signal Pin output from the external device 90. The resolution detector 70 is provided for this purpose. The resolution of the image signal Pin is the number of pixels (for example, 1024 pixels × 768 pixels) along the horizontal direction H and the vertical direction V per screen of the image signal Pin. The value is fixed.

  A well-known simple relationship is established between the resolution of the image signal Pin and the cycle of the synchronization signal Sync. The resolution detection unit 70 detects the resolution of the image signal Pin by receiving the synchronization signal Sync and calculating the period thereof. For this purpose, for example, the period of the synchronization signal Sync is converted into the number of clock pulses, and the resolution is calculated through digital signal processing.

  The drive control unit 40 controls the resolution of the image signal Pc, that is, the resolution of the image to be displayed, for example, as shown in the graph of FIG. 18, according to the resolution of the input image signal Pin. The higher the high frequency component of the gain of the amplifying unit 2, the higher the resolution of the image signal Pc. Therefore, the vertical axis in FIG. 18 is equivalent to the strength of the high frequency component of the gain. As shown in FIG. 18, the drive control unit 40 only needs to refer to the horizontal resolution in the resolution of the image signal Pin. Therefore, it is sufficient for the resolution detection unit 70 to detect only the horizontal resolution.

  The device 105 is set so that the highest resolution of the image signal Pin is projected with good reproducibility (straight line C1). On the other hand, if the resolution of the image signal Pin is low, there is no problem in terms of visibility even if the resolution of the projected image is low. For example, the relationship of resolution between the image signals Pin and Pc may be a relationship given by a straight line C2.

  Furthermore, it is known that moire fringes are likely to appear on the screen 10 over a certain range due to interference between the resolution of the image signal Pin and the grill pitch of the CRT 1. FIG. 18 illustrates this range as a “moire area”. The position and width of the moire area depend on the height of the resolution indicated by the straight line C1 (the thickness of the electron beam displayed on the screen 10). In order to suppress the appearance of moire fringes, the relationship of resolution between the image signals Pin and Pc may be changed.

  For this purpose, for example, a value slightly higher than the end portion on the high resolution side of the moire area determined by the height of the straight line C1 is set as the reference resolution Rref. If the resolution of the image signal Pin detected by the resolution detection unit 70 is equal to or higher than the reference resolution Rref, the drive control unit 40 determines the resolution of the image signal Pc to a high value so as to match the straight line C1. Conversely, if the resolution of the image signal Pin is lower than the reference resolution Rref, the resolution of the image signal Pc is determined to be a certain height that is lower than the straight line C1 and higher than the straight line C2. The drive control unit 40 sets the target value of the transient characteristic described above so as to realize the frequency characteristic corresponding to each resolution of the determined image signal Pc.

  It is more desirable that the targeted transient characteristic is corrected depending on the type of image (normal display, reverse display, etc.). Therefore, in the apparatus 105, the drive control unit 40 refers to not only the detection results of the transient characteristic detection unit 71 and the resolution detection unit 70 but also the beam current J detected by the beam current detection unit 5. For example, the target may be corrected so as to emphasize the high-frequency component for the binary image of normal display, and may be corrected so as to weaken the high-frequency component for the binary image of reverse display.

  As described above, the apparatus 105 includes the resolution detection unit 70, the transient characteristic detection unit 71, and the beam current detection unit 5, and the drive control unit 40 performs control with reference to the detection signals obtained by these. Do. For this reason, not only the type of image, but also the difference in resolution of the input image signal Pin and the difference in the transient characteristics (pulse waveform) of the input image signal Pin are taken into consideration, so that overall visibility is achieved. It is possible to automatically display the optimized image.

  Note that the image signal Pin input from the external device 90 to the device 105 is not only the RGB color system image signal Pin (R, G, B) but also other color system images such as the YIQ color system. It may be a signal. The transient characteristic detection unit 71 may detect transient characteristics for all three components, or may detect one component as a representative. As the number of components to be detected increases, detection with higher accuracy becomes possible.

  In addition, the device 105 can be modified so that only one of the resolution detection unit 70 and the transient characteristic detection unit 71 is provided. Further, the beam current detection unit 5 and the A / D conversion unit 14 can be removed. In other words, each of the difference in the image type, the difference in the resolution of the input image signal Pin, and the difference in the transient characteristics of the input image signal Pin are individually considered or comprehensively determined by any combination Based on this, it is generally possible to optimize the visibility of the projected image. For example, the drive control unit 40 can also control the frequency characteristics so as to realize the relationship of FIG. 18 based only on the resolution detected by the resolution detection unit 70.

  Further, as shown in FIG. 19, the device 105 can be modified so that the frequency characteristics can be manually changed from the outside. The device 106 includes an operation unit 73, a variable resistance element 74, and an A / D conversion unit 75 instead of the transient characteristic detection unit 71. For example, a positive power supply potential line and a ground potential line are connected to the variable resistance element 74. The operator (operator) can change the voltage drop generated in the variable resistance element 74 by operating the operation unit 73. This voltage drop is converted into a digital signal by the A / D converter 75 and transmitted to the drive controller 40.

  The drive control unit 40 may refer to a signal output from the A / D conversion unit 75 instead of the detection signal from the transient characteristic detection unit 71. As a result, the frequency characteristics set based on the detection signals from the resolution detection unit 70 and the beam current detection unit 5 can be shifted based on the manual operation of the operator. For example, the operator can operate the operation unit 73 so as to obtain an appropriate transient characteristic while viewing an image displayed on the screen 10. In particular, when the current adjustment unit 41 includes the FET 45 that operates in the non-saturation region as in the device 106, the operator can continuously shift the frequency characteristics.

<5. Embodiment 5>
FIG. 20 is a block diagram illustrating a configuration of the image display apparatus according to the fifth embodiment. This device 107 is characterized in that it includes a range specifying unit 8. For example, the drive control unit 40 can control the control exemplified in the first to fourth embodiments, such as control of frequency characteristics based on detection signals from the resolution detection unit 70 and the beam current detection unit 5 and operation of the operation unit 73. This is selectively executed on an image displayed in a specific area (for example, a small screen) in the entire image designated by the designation unit 8. FIG. 20 illustrates a form in which the range specifying unit 8 is added to the device 106 (FIG. 19).

  The range designation unit 8 detects a position signal transmitted from the external device 90 while being superimposed on the image signal Pin or the synchronization signal Sync, and designates a specific range (hereinafter referred to as “control window”) based on the position signal. The position signal is a signal representing the position of the control window. As shown in the operation explanatory diagram of FIG. 21, the position signal Cs corresponding to the control window W set in the entire image that can be displayed on the screen 10 is, for example, in response to the synchronization signal Sync or the image signal Pin. And superimposed on the position corresponding to the end of the control window W.

  Whether the position signal Cs is superimposed on the synchronization signal Sync or the image signal Pin or on both depends on the external device 90. In the form in which the position signal Cs is superimposed on the image signal Pin, for example, when the external device 90 is a personal computer, the position signal Cs is output only by software (program) that outputs the image signal Pin regardless of hardware. There is an advantage that can be generated.

  FIG. 21 shows an example in which the position signal Cs superimposed on the synchronization signal Sync is superimposed on both the horizontal synchronization signal Sync (H) and the vertical synchronization signal Sync (V). ) May be superimposed only on. Further, the position signal Cs to be superimposed on the image signal Pin may be superimposed on all of the three component image signals Pin (R, G, B), or may be superimposed on any one or two components. Good. In general, the more signals that are to be superimposed with the position signal Cs, the more accurate the detection of the position signal Cs.

  FIG. 22 is a block diagram showing an internal configuration of the range specifying unit 8. The position signal Cs superimposed on the image signal Pin is extracted by the position signal extraction unit 81, and the position signal Cs superimposed on the synchronization signal Sync is extracted by the position signal extraction unit 84. When the position signal Cs is superimposed on the image signal Pin, in order to facilitate the extraction of the superimposed position signal Cs, the image signal Pin is preferably deleted in a portion where the position signal Cs exists, or It ’s weakened. As a result, an image corresponding to the position signal Cs is displayed on the screen 10 at the end portion along the horizontal direction H of the control window W as shown in FIG. As a result, the position of the control window W in the entire image can be easily visually confirmed.

  Returning to FIG. 22, the position signal Cs extracted by the position signal extraction unit 81 is sent to the range determination unit 82. The range determination unit 82 determines the position of the control window W in the entire image by determining the position of the position signal Cs in the image signal Pin. As a result, a signal designating the position of the control window W is sent from the range determination unit 82 to the drive control unit 40.

  Similarly, the position signal Cs extracted by the position signal extraction unit 84 is sent to the range determination unit 85. The range determination unit 85 determines the position of the control window W in the entire image by determining the position of the position signal Cs in the synchronization signal Sync. As a result, a signal designating the position of the control window W is sent from the range determination unit 85 to the drive control unit 40.

  As described above, since the range specifying unit 8 includes two position signal processing systems corresponding to both the synchronization signal Sync and the image signal Pin, the position signal Cs is superimposed on either the synchronization signal Sync or the image signal Pin. Appropriate processing can be performed for the external device 90 that performs the processing or for the external device 90 that overlaps both. The drive control unit 40 selectively performs the various controls described in the first to fourth embodiments on the control window W specified by the signal transmitted from one or both of the range determination units 82 and 85. Execute. If there is no need to support a wide range of external devices 90, the range specifying unit 8 does not need to include two processing systems, and may include only one system corresponding to a specific external device 90.

  Returning to FIG. 21, the position signal Cs can have various patterns, as exemplified by the position signal Cs superimposed on the image signal Pin. Not only represents the position of the control window W by the position of the position signal Cs in the image signal Pin or the synchronization signal Sync but also represents the type of image quality to be controlled in the control window W by having a pattern. Is possible. The controlled image quality may include not only image quality that can be adjusted by frequency characteristics such as the presence / absence of contour correction but also image quality that cannot be adjusted only by frequency characteristics, such as image brightness and contrast.

  The pattern illustrated in FIG. 21 is a pulse train having various pulse numbers, pulse intervals, and pulse widths, and corresponds to a barcode expressed by the pulse train. The pattern of the position signal Cs is not limited to the example of FIG. The pattern of the position signal Cs superimposed on the image signal Pin can be arbitrarily set within a range that can be distinguished from the image signal Pin.

  As shown in FIG. 22, the range specifying unit 8 further includes image quality control decoding units 83 and 86. These image quality control decoding units 83 and 86 decode the pattern of the position signal Cs extracted by the position signal extraction units 81 and 84, respectively, and determine the type of image quality to be controlled. The image quality control decoding units 83 and 86 further send a signal designating the type of image quality to be controlled to the drive control unit 40. The drive control unit 40 controls the control window W with respect to the type of image quality specified by the signal transmitted from one or both of the image quality control decoding units 83 and 86.

  For example, contour correction is applied to the control window W or the brightness of the image is changed. The drive control unit 40 not only controls the frequency characteristic through the current adjustment unit 41 but also controls the preamplifier 25 which is a device part for adjusting the brightness and contrast of the image displayed on the screen 10. Is sent out. As a result, control as represented by the position signal Cs is performed even for image quality of a type that cannot be controlled through frequency characteristics, such as brightness and contrast.

  In FIG. 8 referred to in the second embodiment, three types of images are drawn side by side in the screen 10 for convenience. However, if the device 107 of the fifth embodiment is used, as shown in FIG. 8, it is possible to project three types of images, each having an appropriate frequency characteristic, arranged side by side in the same entire image. It becomes.

  As described above, in the apparatus 107, image quality control is selectively performed on the control window W in the entire image based on the designation of the external apparatus 90. Further, not only the range of the control window W in the entire image but also the type of image quality to be controlled can be designated by the external device 90. As a result, image quality control for enhancing visibility can be flexibly performed on various types of images to be projected.

<6. Embodiment 6>
FIG. 23 is a block diagram illustrating a configuration of the image display apparatus according to the sixth embodiment. The device 108 is characterized in that the position of the control window W can be designated by the operation of the operator. That is, the device 108 includes an operation unit 76, a variable resistance element 77, an A / D conversion unit 78, and a position signal generation unit 79 so that the position signal Cs can be generated based on the operation of the operator. . For example, a positive power supply potential line and a ground potential line are connected to the variable resistance element 77.

  The operator can change the voltage drop generated in the variable resistance element 77 by operating the operation unit 76. This voltage drop is converted into a digital signal by the A / D converter 78 and transmitted to the position signal generator 79. The position signal generation unit 79 generates a position signal Cs that represents the position of the control window W designated by the operation unit 76 based on the digital signal output from the A / D conversion unit 78. At this time, the position signal generator 79 outputs the position signal Cs at a timing corresponding to the position of the control window W by referring to the synchronization signal Sync sent from the external device 90.

  The signal mixing unit 87 superimposes the position signal Cs output from the position signal generation unit 79 on the image signal Pin transmitted from the external device 90. The position signal Cs is superimposed on a part corresponding to the position of the control window W in the image signal Pin. The range specifying unit 8 extracts the position signal Cs from the signal output from the signal mixing unit 87, determines the position of the control window W represented by the position signal Cs, and sets the control window W to the drive control unit 40. To specify. The range designation unit 8 only needs to include the position signal extraction unit 81 and the range determination unit 82 in the range designation unit 8 (FIG. 22) of the device 107.

  Since the position signal Cs is input to the amplifying unit 2 together with the image signal Pin, as shown in FIG. 24, the position signal Cs is displayed on the screen 10 at the ends of the control window W, for example, the upper left corner and the lower right corner. Appears. The operator can recognize the control window W by viewing the position signal Cs. Therefore, the operator can move the control window W to a desired position in the entire image by operating the operation unit 76 while viewing the position signal Cs. As described above, in the apparatus 108, the position of the control window W with respect to the entire image can be arbitrarily designated by the operator's manual operation.

<7. Modification>
(1) In the above embodiment, an example in which the image signal Pc amplified by the amplifying unit 2 is input to the cathode of the CRT 1, that is, an example in which the CRT 1 is a cathode voltage control type has been described. The CRT 1 may be a grid voltage control type.

  (2) In the above embodiment, the inductor 3 is inserted in the path between the output of the amplifier 20 and the CRT 1, but in the amplifier 2, other inductors that affect the frequency characteristics of the gain are provided. It may be provided at the site. However, in the form inserted in the path between the output of the amplifier 20 and the CRT 1, the advantages as described in the first embodiment can be obtained.

  (3) Instead of the inductor 3 having a plurality of coils coupled by mutual inductance, it has a single coil, for example, the position of the magnetic core and the size of the gap of the core can be adjusted electrically. A simple inductor may be used. However, the inductor 3 provides the advantages described in the first embodiment.

  (4) In the device 106 of FIG. 19, none of the resolution detection unit 70, the transient characteristic detection unit 71, and the beam current detection unit 5 is provided. Instead, the operation unit 73, the variable resistance element 74, and A It is possible to change to the simplest configuration so that the / D converter 75 is provided. At this time, the control of the frequency characteristic is performed only manually. When the operator manually operates while viewing the screen 10, it is possible to realize an optimum frequency characteristic for the projected image. However, in the embodiment provided with the resolution detection unit 70, the transient characteristic detection unit 71, the beam current detection unit 5, and the like, the advantages described in the fourth embodiment can be obtained.

1 is a block diagram of an apparatus according to Embodiment 1. FIG. FIG. 3 is an operation explanatory diagram of the apparatus according to the first embodiment. FIG. 3 is an operation explanatory diagram of the apparatus according to the first embodiment. FIG. 3 is an operation explanatory diagram of the apparatus according to the first embodiment. FIG. 3 is an operation explanatory diagram of the apparatus according to the first embodiment. FIG. 6 is a block diagram of an apparatus according to a second embodiment. 6 is a graph showing the characteristics of the FET of the second embodiment. FIG. 10 is an operation explanatory diagram of the apparatus according to the second embodiment. FIG. 10 is a block diagram of another example of the apparatus according to the second embodiment. FIG. 10 is a block diagram of an apparatus according to a third embodiment. FIG. 10 is a block diagram of an apparatus according to a fourth embodiment. FIG. 10 is an operation explanatory diagram of the apparatus according to the fourth embodiment. FIG. 10 is an operation explanatory diagram of the apparatus according to the fourth embodiment. FIG. 10 is an operation explanatory diagram of the apparatus according to the fourth embodiment. FIG. 10 is an operation explanatory diagram of the apparatus according to the fourth embodiment. FIG. 10 is an operation explanatory diagram of the apparatus according to the fourth embodiment. FIG. 10 is an operation explanatory diagram of the apparatus according to the fourth embodiment. FIG. 10 is an operation explanatory diagram of the apparatus according to the fourth embodiment. FIG. 10 is a block diagram of another example of the apparatus according to the fourth embodiment. FIG. 10 is a block diagram of an apparatus according to a fifth embodiment. FIG. 10 is an operation explanatory diagram of the apparatus according to the fifth embodiment. FIG. 10 is a block diagram of a range specifying unit according to the fifth embodiment. FIG. 10 is a block diagram of an apparatus according to a sixth embodiment. FIG. 20 is an operation explanatory diagram of the apparatus according to the sixth embodiment. It is a block diagram of the conventional apparatus.

Explanation of symbols

1 CRT (image output unit), 2 amplifying unit, 3 inductor, 4 control unit, 5 beam current detecting unit (luminance detecting unit), 8 range specifying unit, 10 screen, 20 amplifier, 31 primary coil, 32 secondary coil, 40 drive control unit, 41 current adjustment unit, 70 resolution detection unit, 71 transient characteristic detection unit, 73 operation unit, 81,84 position signal extraction unit, 82,85 range determination unit, 83,86 image quality control decoding unit, 90 external Device, I current, J beam current, Pin, Pin (R, G, B), Pc Image signal, Sync, Sync (H, V) Sync signal.

Claims (5)

A cathode ray tube for displaying an image represented by the image signal;
An amplifying unit having a variable inductor and amplifying the image signal and supplying the image signal to the cathode ray tube with a gain having a frequency characteristic based on induction of the variable inductor;
A beam current detector for detecting a beam current of the cathode ray tube;
A control unit for controlling the frequency characteristics by controlling the induction based on the magnitude of the beam current;
A transient characteristic detection unit for detecting a pulse waveform of the image signal output from the amplification unit ,
Wherein the control unit controls the frequency characteristic, an image display device that closer to the pulse waveform detected by said transient characteristic detector target. The image display device according to claim 1,
The amplifying unit further includes an amplifier that amplifies the image signal,
An image display device in which the variable inductor is interposed in a path between the amplifier and the cathode ray tube. The image display device according to claim 1 or 2,
The variable inductor includes a primary coil and a secondary coil inductively coupled to each other;
The primary coil is connected to the amplifier;
The secondary coil is connected to the control unit;
The induction is induction of the primary coil;
The said control part is an image display apparatus which controls the induction | guidance | derivation of the said primary coil by controlling the electric current excited by the electric current which flows into the said primary coil in the said secondary coil. The image display device according to any one of claims 1 to 3,
A resolution detector for detecting the resolution of the image signal based on the synchronization signal of the image;
The control unit is an image display device that changes the frequency characteristic depending on a resolution of the image signal. The image display device according to any one of claims 1 to 4,
The control unit is based on the beam current detected by the beam current detection unit, whether or not the image to be projected is a normal display binary image, and a reverse display binary image. whether, determines, with respect to the normal display of the binary image, intensified high frequency components of the gain, for the reverse display of the binary image, so weakened, an image that controls the frequency characteristic Display device.

Images