JPWO2015132908A1 - Display control device - Google Patents

Abstract

Provided is a display control device capable of detecting a screen abnormality even during a display operation. In the case of the screen (21) in which images are intermittently projected and the light (difference) between the common electrode (26) and the selection electrode (27) can be switched between the transmission state and the scattering state with respect to the light, the drive control signal The common electrode (26) and the drive control signal generation unit (311) are generated by the drive signal for generating a potential difference between the generation unit (311) and the common electrode (26) that is generated and applied to the selection electrode (27). If the potential difference generated at both ends of the detection resistor (Rcom) connected to the differential resistor (313a) is detected by the differential amplifier (313a) and the potential difference detected by the differential amplifier (313a) by the comparator (313b) is equal to or higher than the threshold value, High Output level.

Description

  The present invention relates to a display control device that controls display of a screen or the like that displays an image.

  For example, Patent Document 1 discloses a display device that displays an image projected from a projector or the like using a transparent body such as glass as a screen.

  In this type of screen, for example, when an abnormality such as a short circuit of the liquid crystal cell occurs, there is a possibility that an image (projected light) projected from a projector or the like may penetrate. When such a situation occurs, there is a possibility that the observer looks directly at the projection light.

  As for abnormality detection of the liquid crystal panel, for example, methods described in Patent Documents 2 and 3 can be cited. Patent Document 2 discloses whether the current output or voltage output when the cell capacitor of the TFT-LCD is charged or not is integrated over time, and whether or not the difference between charging and non-charging is greater than a reference value. It has been proposed to determine whether it is normal or not by determining

  Patent Document 3 proposes inspecting the presence or absence of a pixel defect based on a difference in charging time or discharging time caused by a difference between a capacity of a normal pixel portion and a capacity of an abnormal pixel portion of liquid crystal.

JP 2004-184979 A JP-A-7-333278 JP-A-10-293149

  The methods described in Patent Documents 2 and 3 relate to panel inspection at the time of production, and a waveform dedicated to inspection is applied. Therefore, it is impossible to detect an abnormality that has occurred when an image is actually projected and displayed from a projector or the like (during a display operation).

  In addition, a failure during display of a liquid crystal panel that is not an image projected from the outside, which is the subject of Patent Documents 2 and 3, can be easily recognized by the user from an abnormal display state without inspection. Since only light such as light is observed, there are few problems due to the failure itself. However, the display device described in Patent Document 1 has a risk due to penetration of the projection light.

  Such a problem is not limited to a screen on which an image is projected by a projector or the like. For example, a dimming screen used for a blindfold in which the transmittance is changed so that it cannot be seen from the opposite side of the screen is also affected. To do. In this case, there arises a problem that what is originally desired to be hidden is visible due to an abnormality of the screen.

  Therefore, in view of the above-described problems, an object of the present invention is to provide a display control device that can detect an abnormality of a screen even during operations such as display and blindfolding.

  In order to solve the above-mentioned problem, an invention according to claim 1 includes an optical layer sandwiched between a first electrode and a second electrode, and a potential difference between the first electrode and the second electrode. A screen display control apparatus capable of changing a transmittance with respect to light, the drive signal generating unit being connected to the first electrode and generating a drive signal for generating the potential difference, the first electrode, A resistor connected in series with the drive signal generation unit or in series with the second electrode, a detection unit for detecting a potential difference generated at both ends of the resistor by the drive signal, and the potential difference detected by the detection unit And an abnormality signal output unit that outputs a signal relating to the abnormality of the screen based on the above.

  According to a second aspect of the present invention, an image is intermittently projected, and has an optical layer sandwiched between the first electrode and the second electrode, and between the first electrode and the second electrode. A screen display control apparatus capable of switching between a transmission state and a scattering state with respect to light according to a potential difference, and a drive signal generation unit that is connected to the first electrode and generates a drive signal for generating the potential difference; A resistor connected in series with the first electrode and the drive signal generation unit or in series with the second electrode, a detection unit for detecting a potential difference generated at both ends of the resistor by the drive signal, and the detection And an abnormality signal output unit that outputs a signal relating to the abnormality of the screen based on the potential difference detected by the unit.

  The invention according to claim 9 has an optical layer sandwiched between the first electrode and the second electrode, and transmits light with respect to light by a potential difference between the first electrode and the second electrode. A display control method for a screen that can be changed, and a drive signal generation step of generating a drive signal for generating the potential difference by applying to the first electrode, and the first electrode and the drive by the drive signal A detection step for detecting a potential difference generated at both ends of a resistor connected in series with the signal generation unit or in series with the second electrode, and a signal regarding abnormality of the screen based on the potential difference detected in the detection step. And an abnormal signal output step for outputting.

  The invention described in claim 10 is characterized in that the display control device control method described in claim 9 is executed by a computer.

  The invention described in claim 11 is characterized in that the control program for the display control device described in claim 10 is stored.

  According to a twelfth aspect of the present invention, an image is intermittently projected, and has an optical layer sandwiched between the first electrode and the second electrode, and between the first electrode and the second electrode. A screen display control method capable of switching between a transmission state and a scattering state with respect to light according to a potential difference, and a driving signal generation step of generating a driving signal for generating the potential difference by applying the first electrode. Detecting a potential difference generated at both ends of a resistor connected in series with the first electrode and the drive signal generation unit or in series with the second electrode according to the drive signal, and detecting in the detection step And an abnormal signal output step of outputting a signal relating to an abnormality of the screen based on the potential difference.

  A thirteenth aspect of the invention is characterized in that the display control device control method according to the twelfth aspect is executed by a computer.

  The invention described in claim 14 is characterized in that the control program for the display control device described in claim 13 is stored.

It is a schematic block diagram of the display apparatus provided with the display control apparatus concerning 1st Example of this invention. It is typical sectional drawing of the screen shown by FIG. It is explanatory drawing of the projector which projects in synchronization with the optical characteristic of the screen shown by FIG. It is explanatory drawing of the display state with which the image | video by the image light and the background of a screen overlap in the display apparatus shown by FIG. It is a functional block diagram of the synchronous control part shown by FIG. FIG. 6 is a circuit diagram of the differential amplifier shown in FIG. 5. FIG. 6 is a circuit diagram illustrating an equivalent circuit of a part of the synchronization control unit illustrated in FIG. 5 and a screen. FIG. 8 is a timing chart showing drive waveforms during normal operation of the circuit shown in FIG. 7. FIG. 8 is a timing chart showing drive waveforms when the screen of the circuit shown in FIG. 7 is short-circuited. FIG. 8 is a timing chart showing drive waveforms when a detection resistor of the circuit shown in FIG. 7 is in an open state. It is the flowchart which showed the operation | movement of the synchronous control part shown in FIG. It is a circuit diagram showing other circuit composition. It is a circuit diagram showing other circuit composition. It is a circuit diagram showing other circuit composition. It is a timing chart which showed the drive waveform of the screen in which the display control apparatus concerning the 2nd example of the present invention operates normally. It is the timing chart which showed the drive waveform when a screen short-circuits. It is a timing chart which showed the drive waveform in case a detection resistance is an open state. It is the graph which showed the relationship between the value of the electrostatic capacity of a screen, and the time change of the output voltage of a differential amplifier. It is typical sectional drawing of the screen which the synchronous control part concerning the 3rd Example of this invention controls. FIG. 20 is a schematic front view of a screen showing an arrangement of a plurality of selection electrodes shown in FIG. 19. It is explanatory drawing of the synchronous control of the scanning of a screen shown by FIG. 19, and a drive. It is explanatory drawing of the projector which scans the screen shown by FIG. FIG. 20 is a schematic timing chart of scanning and driving of the screen shown in FIG. 19. FIG. It is the circuit diagram which showed a part of synchronous control part and the equivalent circuit of a screen. 6 is a timing chart showing drive waveforms of a screen that is operating normally. 6 is a timing chart showing drive waveforms of a screen that is operating normally. It is a timing chart showing the drive waveform of the abnormally operating screen. It is a timing chart in case selection end and selection end overlap. It is a timing chart at the time of shifting selection start and selection end. It is a schematic block diagram of the light control screen provided with the display control apparatus concerning the 4th Example of this invention.

  Hereinafter, a display device according to an embodiment of the present invention will be described. A display control device according to an embodiment of the present invention includes a first signal and a driving signal generated by a driving signal that is generated by a driving signal generation unit and applied to the first electrode to generate a potential difference with the second electrode. A potential difference generated at both ends of a resistor connected in series with the generation unit or in series with the second electrode is detected by the detection unit, and a signal relating to an abnormality of the screen is generated based on the potential difference detected by the detection unit at the abnormal signal output unit. Output. By doing so, the abnormality can be detected by detecting the potential difference of the resistance connected to the first electrode or the second electrode, so that the abnormality of the screen can be detected without inputting an inspection signal or the like. it can.

  In addition, the display control apparatus according to another embodiment of the present invention can intermittently project an image and switch between a transmission state and a scattering state with respect to light by a potential difference between the first electrode and the second electrode. In the case of a simple screen, the drive signal generator generates and applies to the first electrode to generate a potential difference between the second electrode and the first electrode and the drive signal generator in series, or A potential difference generated between both ends of the resistor connected in series with the second electrode is detected by the detection unit, and a signal relating to the abnormality of the screen is output based on the potential difference detected by the detection unit by the abnormality signal output unit. In this way, in the screen in which an image is intermittently projected and the light can be switched between a transmission state and a scattering state with respect to light by a potential difference between the first electrode and the second electrode, Since the abnormality can be detected by detecting the potential difference between the resistors connected to the two electrodes, it is possible to detect the abnormality of the screen without inputting an inspection signal or the like.

  The detection by the detection unit may be performed during a period in which an image is projected on the screen. In this way, it is possible to detect screen abnormalities that occur during the display operation.

  Moreover, when the signal regarding abnormality is output, you may have a projection control part which controls so that the projection of an image may not reach a screen. By doing so, the projection light can be stopped or blocked when an abnormality is detected. Therefore, the viewer can use the screen safely without directly viewing the light from the projector or the like.

  Further, the abnormality signal output unit may output a signal relating to an abnormality of the screen when the potential difference is equal to or larger than a predetermined threshold value. By doing so, it is possible to easily determine whether or not there is an abnormality based on the potential difference generated between both ends of the resistor by setting the threshold value.

  In addition, the abnormal signal output unit outputs a signal relating to an abnormality of the screen when the number of pulse signals indicating that the potential difference is greater than or less than a predetermined threshold value within a predetermined period is different from a predetermined number of times. It may be output. By doing so, the drive waveform is a rectangular wave, and the waveform output by the detection unit is output as a detection signal corresponding to the transient response due to the relationship of the CR circuit composed of the screen capacitance and the surrounding impedance. Even if it becomes, it can be determined whether it is abnormal.

  Further, the abnormal signal output unit may output a signal relating to an abnormality of the screen based on the width of the pulse signal. By doing so, the width of the pulse signal changes due to the change in the capacitance of the screen, so that an abnormality of the screen can be detected. In particular, it is possible to capture signs of abnormality due to changes over time.

  Further, the second electrode may be divided into a plurality, and a resistor may be connected between the first electrode and the drive signal generation unit. By doing in this way, even when the second electrode is divided and individually driven, an abnormality in each divided region can be detected with one resistor on the first electrode side.

  The display control method according to an embodiment of the present invention includes the first electrode and the second electrode generated by the drive signal generation step and applied to the first electrode to generate a potential difference between the first electrode and the second electrode. A potential difference generated at both ends of a resistor connected in series with the drive signal generation unit or in series with the second electrode is detected in the detection process, and the screen abnormality is detected based on the potential difference detected in the detection process in the abnormal signal output process. Output a signal. By doing so, the abnormality can be detected by detecting the potential difference of the resistance connected to the first electrode or the second electrode, so that the abnormality of the screen can be detected without inputting an inspection signal or the like. it can.

  In addition, in the display control method according to another embodiment of the present invention, an image is intermittently projected, and a transmission state and a scattering state can be switched with respect to light by a potential difference between the first electrode and the second electrode. In the case of a simple screen, the drive signal is generated in the drive signal generation step and applied to the first electrode to generate a potential difference between the second electrode and the first electrode and the drive signal generation unit in series, or A potential difference generated between both ends of the resistor connected in series with the second electrode is detected in the detection step, and a signal relating to an abnormality of the screen is output based on the potential difference detected in the detection step in the abnormal signal output step. In this way, in the screen in which an image is intermittently projected and the light can be switched between a transmission state and a scattering state with respect to light by a potential difference between the first electrode and the second electrode, Since the abnormality can be detected by detecting the potential difference between the resistors connected to the two electrodes, it is possible to detect the abnormality of the screen without inputting an inspection signal or the like.

  Moreover, it is good also as a display control program which performs the display control method mentioned above by computer. By doing so, it is possible to detect abnormality of the screen using the computer even during the display operation.

  Further, the display control program described above may be stored in a computer-readable recording medium. In this way, the program can be distributed as a single unit in addition to being incorporated in the device, and version upgrades can be easily performed.

  A display device 1 including a display control device according to a first embodiment of the present invention will be described with reference to FIGS. As shown in FIG. 1, the display device 1 includes a screen 21 and a synchronization control unit 31, and a projector 11 is connected to the display device 1. The display device 1 is a transmissive projection device that transmits and scatters image light from the projector 11 through a screen 21.

  The projector 11 can use a transmission-type or reflection-type liquid crystal light valve that sequentially shifts the black state (a state in which no projection light is emitted) on the screen 21 during the scanning cycle, but other elements may be used. The projector 11 may perform raster scanning in the video scanning cycle and project video light (image light) on the display surface of the screen 21 dot-sequentially. That is, video light is projected intermittently at a predetermined cycle. As the projector 11, for example, a laser projector or the like in which the irradiation direction of the intensity-modulated light beam is reflected by a movable mirror and shaken can be used. The projector 11 can be considered in the same manner as the image light irradiation position being sequentially scanned in one direction on the screen 21.

  The projector 11 may be any projector that can project video light modulated by video information (image information) onto the screen 21. Note that the video information is obtained from a video signal input to the projector 11. Video signals include, for example, NTSC (National Television Standards Committee), analog video signals such as PAL (Phase Alternation by Line), MPEG-TS (Moving Picture Experts Group-Transport Stream) format, HDV (High -There are video signals in digital format such as Definition Video) format. The projector 11 may receive not only a moving image video signal but also a still image video signal such as JPEG (Joint Photographic Experts Group). In this case, the projector 11 may scan the screen 21 repeatedly with the same video light for displaying a still image.

  The screen 21 may be any screen that can change the optical state by applying a voltage. As for the optical state of the screen 21, a scattering state is an image state, and a transparent transmission state in which scattering of incident light is smaller and parallel light transmittance is higher than that is a non-image state. That is, it is possible to switch between a transmission state and a scattering state with respect to light.

  The screen 21 may be, for example, a light control screen that uses a liquid crystal material and changes a scattering state and a transparent transmission state in which scattering of incident light is small. In addition to using liquid crystal elements such as polymer-dispersed liquid crystals, the dimming screen controls the transparent transmission state with small scattering of incident light by moving the white powder in the transparent cell. For example, a device that orients particles by applying a voltage, such as an element to be applied, or a device that utilizes a color change phenomenon of a substance by an electrochemical reversible reaction (electrolytic oxidation-reduction reaction) by applying a voltage (electrochromic) may be used.

  FIG. 2 is a schematic cross-sectional view of the screen 21 that can control the optical state. The screen 21 shown in FIG. 2 has an optical layer 25 in which a composite material containing liquid crystal is sandwiched between a pair of transparent glass plates 23 and 24. A common electrode 26 is formed on the entire surface of one glass plate 24 on the optical layer 25 side. A selection electrode 27 is arranged on the entire surface of the other glass plate 23 on the optical layer 25 side. An intermediate layer made of an insulator may be formed between the electrodes 26 and 27 and the optical layer 25.

  Further, the common electrode 26 and the selection electrode 27 are formed as transparent electrodes by using, for example, ITO (indium tin oxide). The optical layer 25 is disposed between the selection electrode 27 and the common electrode 26. Further, at least one of the common electrode 26 and the selection electrode 27 may be configured as an electrode that is a half mirror that transmits a part of incident light.

  A voltage is applied to the screen 21 so as to generate a potential difference between the common electrode 26 as the first electrode and the selection electrode 27 as the second electrode. The optical state in the optical layer 25 changes depending on the voltage applied to the common electrode 26 and the selection electrode 27.

  The screen 21 is classified into a reverse mode and a normal mode according to a state when a voltage is applied so as to generate a potential difference. The screen 21 operating in the reverse mode is in a transparent transmissive state in a normal state where no voltage is applied. When a voltage is applied, it becomes a scattering state with a scattering rate of parallel rays according to the applied voltage. In a screen operating in the normal mode, the screen is in a scattering state in a normal state where no voltage is applied. When a voltage is applied, a transparent transmission state with parallel light transmittance corresponding to the applied voltage is obtained. As for the optical state of the screen 21, a predetermined scattering state corresponds to an image state, and a transparent transmission state having a higher parallel light transmittance than that corresponds to a non-image state. In this embodiment, the reverse mode is described, but the normal mode is also applicable. That is, the screen 21 can be switched between a transmission state and a scattering state with respect to light by a potential difference between the common electrode 26 and the selection electrode 27.

  The synchronization control unit 31 as the display control unit according to the first embodiment of the present invention controls the screen 21 on which the video (image) is projected as light so as to scatter the projected video light, and is projected. If not, control to transparent state. As shown in FIG. 1, the synchronization control unit 31 is connected to the projector 11 and the screen 21. The synchronization control unit 31 controls the optical state of the screen 21 in synchronization with the projection of the image light from the projector 11.

  Next, in the display device 1 according to the present embodiment, a projection method of the projector 11 that projects in synchronization with the optical characteristics of the screen 21 will be described with reference to FIG. FIG. 3 is an explanatory diagram of a method in which the projector 11 projects image light at intervals. In this case, as shown in FIG. 3B, image light is projected on the screen 21 in a short period of time during a part of the scanning cycle. As shown in FIG. 3C, the screen 21 may be in a scattering state during the partial period.

  When the optical state of the screen 21 is controlled so as to increase the parallel light transmittance of the screen 21 in a period other than the part, the see-through characteristic of the screen 21 is not caused in the scanning cycle without causing a decrease in the luminance of the image. Is obtained. In order to obtain the same luminance as compared with the case where image light is regularly projected, projection light whose intensity is approximately the reciprocal of the duty (duty: a) in the scattering state for one scanning period is required. It becomes. Therefore, in order to obtain a high see-through characteristic, a powerful pulsed projection light output is required.

  By controlling the projector 11 and the screen 21 in this way, the screen 21 scatters image light with the same brightness as when the screen 21 is always in a scattering state while having transparency capable of recognizing the object behind the screen. And can be transmitted. That is, it is possible to achieve both a see-through property capable of recognizing a background object and a high image visibility.

  Information on the switching timing for the synchronization control between the projector 11 and the screen 21 is sent from the synchronization control unit 31 to the screen 21 based on an image periodic signal such as a vertical synchronization signal output from the projector 11. The projector 11 and the screen 21 and the synchronization control unit 31 may be capable of wireless communication using electromagnetic waves such as microwaves and infrared rays, and information for obtaining these synchronizations may be exchanged by radio signals.

  In the display device 1, for example, in the installation environment of FIG. 1, an image can be visually recognized as shown in FIG. FIG. 4 is an explanatory diagram of a display state in which the image by the image light and the background of the screen 21 overlap. In FIG. 4, an image of a person 41 by video light is shown on the right side of the screen 21, and a tree 42 as a background on the other side of the screen 21 can be seen on the left side.

  Next, FIG. 5 shows a functional configuration of the synchronization control unit 31. The synchronization control unit 31 includes drive control signal generation units 311 and 312, an abnormal state detection unit 313, and a drive state control unit 314.

  A drive control signal generation unit 311 as a drive signal generation unit generates and outputs a drive control signal that is a voltage waveform applied to one electrode (for example, the common electrode 26) of the screen 21.

  The drive control signal generation unit 312 generates and outputs a drive control signal that is a voltage waveform applied to the other electrode (for example, the selection electrode 27) of the screen 21.

  The abnormal state detection unit 313 includes a detection resistor Rcom, a differential amplifier 313a, and a comparator 313b.

  The detection resistor Rcom is a resistance element having one end connected to one electrode of the screen 21 and the other end connected to the drive control signal generation unit 311. That is, the common electrode 26 and the drive control signal generation unit 311 are connected in series.

  The differential amplifier 313a as a detection unit is a circuit for detecting the voltage across the detection resistor Rcom. That is, a potential difference generated between both ends of the resistor is detected by the drive signal. A circuit example of the differential amplifier 313a is shown in FIG.

  The differential amplifier 313a includes an operational amplifier OP, resistors R1, R2, R3, R4, and R5, and a power source (constant voltage source) V3.

  The operational amplifier OP has a positive input (+) connected to the other end of the resistor R3, one end of the resistor R4, and the other end of the resistor R5, and a negative input (−) connected to the other end of the resistor R1 and one end of the resistor R2. The output is connected to the other end of the resistor R2 and becomes the output (Vout) of the differential amplifier circuit 313a. The negative power source input of the operational amplifier OP is connected to the negative side of the power source V3 and one end of the resistor R5, and the positive power source input is connected to the positive side of the power source V3 and the other end of the resistor R4.

  One end of the resistor R1 is connected to the input V1 of the differential amplifier 313a, and the other end is connected to one end of the resistor R2 and the negative input of the operational amplifier OP.

  The resistor R2 has one end connected to the other end of the resistor R1 and the negative input of the operational amplifier OP, and the other end connected to the output of the operational amplifier OP.

  The resistor R3 has one end connected to the input V2 of the differential amplifier 313a and the other end connected to the plus input of the operational amplifier OP, one end of the resistor R4, and the other end of the resistor R5.

  The resistor R4 has one end connected to the other end of the resistor R3, the other end of the resistor R5, and the plus input of the operational amplifier OP, and the other end connected to the plus power input of the operational amplifier OP and the plus side of the power source V3.

  The resistor R5 has one end connected to the negative power source input of the operational amplifier OP and the negative side of the power source V3 and grounded (connected to the ground potential), and the other end connected to the positive input of the operational amplifier OP, the other end of the resistor R3, and the resistor R4. It is connected to one end.

  That is, the resistor R1 and the resistor R2 are connected in series, and the resistor R4 and the resistor R5 are connected in series.

Here, when the resistance value of the resistor R1 = the resistance value of the resistor R3 and the resistance value of the resistor R4 = the resistance value of the resistor R5 = 1/2 of the resistance value of the resistor R2, the output Vout is expressed by the following equation (1). Can be expressed as

When there is no potential difference between the inputs V1 and V2, the output Vout is controlled to have a voltage value that is ½ that of the power supply V3. When the potential difference between the inputs V1 and V2 is within the range of the following equation (2), the operation can be performed within the power supply voltage (that is, within V3) of the differential amplifier 313a.

  The comparator 313b serving as an abnormal signal output unit compares the output of the differential amplifier 313a with a predetermined threshold value, for example, outputs a high level if it is greater than or equal to the threshold value, and outputs a low level if it is less than the threshold value.

  The drive state control unit 314 serving as a projection control unit performs vertical synchronization input from, for example, the projector 11 as to whether the scattering state and the transmission state are alternately changed (see-through operation), or fixed to the scattering state or the transmission state. The determination is made based on a synchronization signal such as a signal, and the drive control signal generators 311 and 312 are controlled. Further, the driving state control unit 314 detects an abnormality of the screen 21 based on the output of the comparator 313b. The drive state control unit 314 stops the projector 11 when the abnormality of the screen 21 is detected. That is, control is performed so that the projection of the image does not reach the screen 21.

  Next, an operation in which the synchronization control unit 31 configured as described above detects an abnormality of the screen 21 will be described with reference to FIGS. FIG. 7 is a circuit diagram showing the drive control signal generators 311 and 312, the detection resistor Rcom, the differential amplifier 313 a, and the screen 21.

  Of the circuits shown in FIG. 7, the screen 21 shows an equivalent circuit. That is, the screen 21 can be represented by a circuit in which a resistor Rsel1, a capacitance Csel, and a resistor Rsel2 are connected in series and a resistor Rsel3 is connected in parallel.

  The electrostatic capacity Csel is the electrostatic capacity of the liquid crystal cell, the resistance Rsel1 is the resistance component of one electrode, the resistance Rsel2 is the resistance component of the other electrode, and the resistance Rsel3 is the DC resistance component of the liquid crystal cell.

  The resistor Rp connected between the screen 21 and the drive control signal generator 312 is a protective resistor.

  FIG. 8 shows an example of drive waveforms of the circuit shown in FIG. FIG. 8 shows a drive waveform in a normal state. In FIG. 8, the common electrode voltage is a voltage waveform output from the drive control signal generation unit 311 (voltage waveform applied to the common electrode 26), and the selection electrode voltage is a voltage waveform output from the drive control signal generation unit 312 (to the selection electrode 27). Voltage waveform to be applied). Both the common electrode voltage and the selection electrode voltage are sine waves having an amplitude of V volts, and the common electrode voltage and the selection electrode voltage are 180 ° out of phase.

  The inter-screen electrode voltage is a voltage indicating a potential difference between the common electrode 26 and the selection electrode 27 of the screen 21 and indicates a common electrode voltage-selection electrode voltage. For example, when the common electrode voltage is V / 2, the selection electrode voltage is −V / 2, so that V / 2 − (− V / 2) = V. In the present embodiment, the screen 21 in the reverse mode is described. Therefore, when the absolute value of the voltage between the screen electrodes is V volts (the potential difference between the two electrodes is V volts), the scattering state occurs. That is, the drive control signal generation unit 311 generates a drive signal for generating a potential difference between the common electrode 26 and the selection electrode 27.

  The common electrode output side detection resistor terminal indicates the other end side of the detection resistor Rcom (side connected to the drive control signal generation unit 311), and the screen side detection resistor terminal indicates one end side (screen) of the detection resistor Rcom. 21). In the case of FIG. 8, since the screen 21 is normal, the same waveform is obtained at both ends of the detection resistor Rcom.

  The detection signal is obtained by subtracting the waveform of the common electrode output side detection resistor terminal from the waveform of the screen side detection resistor terminal. That is, Vout in FIG. 7 is shown. In addition, when the screen 21 is normal, the amplitude of the detection signal is small, and thus does not exceed a predetermined threshold value.

  The detection result is a result of the comparator 313b, and becomes a low level because the detection signal is not equal to or higher than the threshold value.

  Next, the case where the common electrode 26 and the selection electrode 27 of the screen 21 are short-circuited will be described with reference to FIG. When the common electrode 26 and the selection electrode 27 of the screen 21 are short-circuited (in the case of FIG. 9A), as shown in FIG. 9B, the voltage of the screen-side detection resistance terminal is lowered. Therefore, when a potential difference is generated between both ends of the detection resistor Rcom, the amplitude of the detection signal becomes large and becomes equal to or greater than the threshold value, so that the detection result changes to a high level. That is, an abnormality can be detected when the detection result is at a high level.

  Next, the case where the detection resistor Rcom is in an open state will be described with reference to FIG. If an excessive voltage is applied to the detection resistor Rcom, the resistor may burn out or become high resistance. When the detection resistor Rcom is in an open state (in the case of FIG. 10A), as shown in FIG. 10B, the selection electrode voltage is directly applied to the screen-side detection resistor terminal. Therefore, when a potential difference is generated at the input of the differential amplifier 313a, the amplitude of the detection signal increases and becomes equal to or greater than the threshold value, so that the detection result changes to a high level. That is, an abnormality can be detected when the detection result is at a high level.

  When the detection result as shown in FIG. 9B or FIG. 10B is output from the comparator 313b, the drive state control unit 314 determines that an abnormality has occurred in the screen 21, and stops the projector 11. . That is, in this embodiment, the output signal of the comparator 313b is a signal related to abnormality.

  That is, in this embodiment, the output signal of the comparator 313b is a signal related to abnormality. Note that the output signal of the comparator 313b may be at a high level when it is less than the threshold value, and at a low level when it is greater than or equal to the threshold value (that is, the detection result is inverted from that in FIGS. 9 and 10). In this case, the Low level indicates an abnormality.

  The operation of the synchronization control unit 31 described above is summarized in the flowchart shown in FIG. First, a drive control signal (common electrode voltage, selection electrode voltage) is applied from the drive control signal generation units 311 and 312 (step S1, drive signal generation step), and the potential difference between both ends of the detection resistor Rcom is set to a differential amplifier 313a and a comparator 313b. (Step S2, detection step). In step S3, if the output of the comparator 313b is equal to or greater than the threshold value in the driving state control unit 314 (in the case of YES), the projector 11 is stopped in step S4 because an abnormality is detected (abnormal signal output process), and no abnormality is detected. In the case (in the case of NO), the process returns to step S1 to cause the drive control signal generators 311 and 312 to apply drive control signals.

  According to the present embodiment, in the case of the screen 21 in which an image is intermittently projected and the light can be switched between a transmission state and a scattering state with respect to light by a potential difference between the common electrode 26 and the selection electrode 27, drive control is performed. The detection resistor Rcom connected in series to the common electrode 26 and the drive control signal generation unit 311 is generated by a drive signal generated by the signal generation unit 311 and applied to the common electrode 26 to generate a potential difference with the selection electrode 27. The potential difference generated at both ends is detected by the differential amplifier 313a, and when the potential difference detected by the differential amplifier 313a by the comparator 313b is equal to or greater than the threshold value, the High level is output. By doing this, an abnormality can be detected by detecting the potential difference of the detection resistor Rcom connected to the common electrode 26, so that it is not necessary to input an inspection signal or the like, and the abnormality of the screen 21 even during the display operation. Can be detected.

  That is, detection of the potential difference by the differential amplifier 313a is performed during a period in which an image is projected on the screen 21 (period in which the transmission state and the scattering state are switched), as is apparent from FIG. Therefore, an abnormality of the screen 21 that occurs during the display operation can be detected.

  When the comparator 313b outputs a high level, the drive state control unit 314 controls the projection of the image from the projector 11 so that it does not reach the screen 21, so that the projection light is emitted when an abnormality is detected. Can be stopped. Therefore, the observer can use the screen 21 safely without directly viewing the light from the projector 11.

  In addition, since the comparator 313b outputs a high level when the potential difference is equal to or greater than a predetermined threshold value, it is easy to set the threshold value based on the potential difference that easily occurs at both ends of the detection resistor Rcom. It can be determined whether or not.

  In the above-described embodiment, the detection resistor Rcom is connected between the drive control signal generator 311 and the common electrode 26. However, the present invention is not limited to this, and the connection is, for example, as shown in FIGS. May be. That is, it is only necessary to be connected in series with the first electrode and the drive signal generation unit or in series with the second electrode.

  FIG. 12 shows an example in which the drive control signal generation unit 312 is deleted. In this case, since the selection electrode 27 is fixed to the ground potential (a constant potential), the drive control signal generation unit 311 generates a waveform with an amplitude that is a potential difference that can switch the screen 21 between the scattering state and the transmission state. Output.

  FIG. 13 shows an example in which the drive control signal generation unit 311 is deleted. In this case, since the common electrode 26 is fixed to the ground potential (a constant potential), the drive control signal generation unit 312 functions as a drive signal generation unit, and a potential difference that can switch the screen 21 between the scattering state and the transmission state. Generate and output a waveform with the following amplitude.

  FIG. 14 shows an example in which a detection resistor Rcom is connected between the drive control signal generator 311 and the ground potential (constant potential). Even in such a case, the abnormality of the screen 21 can be detected by the potential difference of the detection resistor Rcom. In this case, the selection electrode 27 may be provided with a drive control signal generator 312 and a protective resistor Rp as shown in FIG.

  A display control apparatus according to a second embodiment of the present invention will be described with reference to FIGS. In this embodiment, the screen 21 is not driven with a sine wave as in the first embodiment, but is driven with a rectangular wave.

  FIG. 15 shows a drive waveform in a normal state. The driving by the rectangular wave includes a common DC system and a frame inversion system. In the common DC method, as shown in FIG. 15A, the voltage on the common electrode (common electrode 26) side is constant at the intermediate potential, and the voltage on the opposite selection electrode 27 side becomes a rectangular wave between the screen electrodes. The voltage fluctuates. In the frame inversion method, as shown in FIG. 15B, a rectangular wave is input to both the common electrode 26 side and the selection electrode 27 side, and the voltage polarity of the screen electrode voltage changes every frame (every video period). To do.

  That is, in the case of the common DC method, the scattering state and transmission state of the screen 21 are controlled by the waveform of the selection electrode voltage, and in the case of the frame inversion method, the scattering state and transmission state of the screen 21 are controlled by both the common electrode voltage and the selection electrode voltage. (The change in the scattering state and the transmission state is shown in the dotted line portion of the voltage between the screen electrodes).

  The selection start signal is a signal that is output from the drive state control unit 314 to the drive control signal generation units 311 and 312 and instructs switching to the scattering state. The selection end signal is a signal that is output from the drive state control unit 314 to the drive control signal generation units 311 and 312 and instructs switching to the transmission state.

  When a voltage waveform as shown in FIG. 15 is applied to the common electrode 26 side and the selection electrode 27 side, when the potential difference between the common electrode voltage and the selection electrode voltage occurs, the capacitance Csel of the screen 21 and the surrounding impedance The transient response is superimposed on the voltage of the detection resistor terminal on the screen 21 side. Therefore, at the timing when the selection start voltage and the selection end voltage are switched, and at an intermediate time (timing when the selection electrode voltage is switched in the case of the common DC system), a detection signal corresponding to the transient response is sent from the differential amplifier 313a as shown in the figure. Is output.

  When the detection signal is equal to or higher than a certain threshold by the comparator 313b, the detection signal becomes High level and is output as a pulse signal. In the example of FIG. 15, the result is 4 (2 when switching the scattering state once) in the common DC method, and the result is 2 (1 when switching the scattering state once) in the frame inversion method. That is, it is possible to determine whether or not the device is operating normally by setting the number of pulses in advance and comparing it with the number of pulses during actual operation.

  Here, an example is shown in which one signal whose threshold value is on the upper side (value increasing side) is detected, but naturally the threshold value may be set to detect the lower signal (the value decreasing side). In addition, both signals may be detected.

  Next, a case where the common electrode 26 and the selection electrode 27 of the screen 21 are short-circuited will be described with reference to FIG. In this case, since the capacitance of the screen 21 is omitted at the screen-side detection resistor terminal, the above-described transient response disappears, and a voltage synthesized with the voltage drop of the detection resistor Rcom and the common electrode voltage appears. Therefore, the number of pulse signals output from the comparator 313b is different from the normal case (becomes less than the normal number of pulses). In the example of FIG. 16, the common DC method is 2 (1 when the scattering state is switched once), and the result is 1 when the frame inversion method is switched (0.5 when the scattering state is switched once, a pulse signal is output every other time). Will be).

  Next, the case where the detection resistor Rcom is in an open state will be described with reference to FIG. In this case, the voltage of the detection resistor terminal on the screen side is affected by the resistance in the differential amplifier 313a, the capacitance of the screen 21, the wiring resistance, and the current from the power supply voltage V3 of the differential amplifier 313a. Therefore, the number of pulse signals output from the comparator 313b is different from the normal case (becomes less than the normal number of pulses).

  As described above, when the number of pulse signals output from the comparator 313b is different from the normal case, the drive state control unit 314 determines that the state is abnormal, and stops the projector 11. That is, a signal relating to an abnormality of the screen 21 is output when the number of pulse signals indicating that the potential difference is greater than or less than a predetermined threshold value within a predetermined period is different from a predetermined number of times. That is, in this embodiment, the drive state control unit 314 functions as an abnormal signal output unit.

  In the illustrated example, the number of pulses is less than a predetermined number. For example, even if the screen is normal, an abnormal current is generated in the power supply system of the drive voltage, and the output current of the switching power supply exceeds the design maximum value. If this happens, a large ripple is generated in the output from the smoothing capacitor, which may exceed the predetermined number of times. That is, the number of pulses may exceed a predetermined number. Even in such a case, the abnormality can be determined by applying the present embodiment.

  According to the present embodiment, the driving state control unit 314 has a predetermined number of pulse signals indicating that the potential difference between both ends of the detection resistor Rcom is greater than or less than a predetermined threshold within one frame period. Since the projector 11 is stopped by outputting a signal related to the abnormality of the screen 21 when the number of times is different from the predetermined number of times, the driving waveform is a rectangular wave, and the CR is configured by the capacitance Csel of the screen 21 and the surrounding impedance. Depending on the relationship between the circuits, even when the waveform output from the comparator 313b is a detection signal corresponding to the transient response, it can be determined whether there is an abnormality.

  In the method shown in the second embodiment, an example of detecting the short circuit between the electrodes of the screen 21 or the high resistance state of the detection resistor Rcom is shown. However, by checking the pulse width of the comparator 313b, The signs can be detected before any abnormalities occur. Details will be described with reference to FIG.

  FIG. 18 is a graph showing the relationship between the value of the capacitance Csel of the screen 21 and the time change of the output voltage of the differential amplifier 313a. FIG. 18B is an enlarged view of the section X in FIG.

  Since the differential amplifier 313a detects a transient response between the capacitance of the screen 21 and the detection resistor Rcom connected thereto, the change in the capacitance with the time change of the screen 21 is the change time of the output voltage of the differential amplifier 313a. Appear in That is, as shown in FIG. 18, the smaller the capacitance, the sharper the rise, and thus the period of time equal to or greater than the threshold value becomes longer, so that the pulse width becomes longer. Therefore, the change in the capacitance of the screen 21 appears with the pulse width. For this reason, by performing a reliability test in advance and capturing the characteristics of the capacitance when the screen 21 does not normally scatter, it is possible to stop before an abnormality occurs.

  That is, a signal related to the abnormality of the screen 21 may be output based on the width of the pulse signal. By doing so, the width of the pulse signal changes due to a change in the capacitance of the screen 21, so that an abnormality of the screen 21 can be detected. In particular, it is possible to capture signs of abnormality due to changes over time.

  Next, a display device according to a third embodiment of the present invention is described with reference to FIGS. The same parts as those in the first to second embodiments described above are denoted by the same reference numerals and the description thereof is omitted.

  In the display device 1 according to the present embodiment, as shown in FIGS. 19 and 20, the screen 21 is divided into a plurality of regions. FIG. 19 is a schematic cross-sectional view of the screen 21 that can control the optical state for each divided region. FIG. 20 is a screen showing the arrangement of the plurality of selection electrodes 27 on the screen 21 shown in FIG. A schematic front view is shown. The screen 21 shown in FIG. 18 has an optical layer 25 in which a composite material containing liquid crystal is sandwiched between a pair of transparent glass plates 23 and 24. A common electrode 26 is formed on the entire surface of one glass plate 24 on the optical layer 25 side. A plurality of selection electrodes 27 are arranged side by side on the optical layer 25 side of the other glass plate 23.

  The plurality of selection electrodes 27 divide the region irradiated with the image light on the screen 21 into strips in one direction (for example, the scanning direction) (see FIG. 20). The plurality of selection electrodes 27 are individually connected to the synchronization control unit 31 and can individually apply voltages. Adjacent selection electrodes 27 are arranged apart from each other. In FIG. 20, strip-like regions are arranged vertically, but the regions may also be divided into a matrix by dividing in the horizontal direction.

  Further, the optical layer 25 of this embodiment can be adjusted for each divided region between a transparent transmission state in which the scattering of incident light is small and a scattering state in which the incident light is scattered.

  The width of the gap region in the optical layer 25 corresponding to the region where the selection electrode 27 is not formed between the selection electrodes 27 is about 5 to 100 micrometers, and is desirably as narrow as possible. The thickness of the optical layer 25 is several to several tens of micrometers, and is determined in consideration of optical characteristics and drive voltage.

  Next, the basic operation principle of the display device 1 of this embodiment will be described. FIG. 21 is an explanatory diagram of synchronous control of scanning and driving of the screen 21. The projector 11 vertically scans the screen 21 from the top to the bottom with image light modulated by the image information. The projector 11 scans the screen 21 vertically from top to bottom for each scanning repetition period (hereinafter also referred to as a scanning cycle).

  FIGS. 21A to 21E show the scanning state at each time point in one scanning cycle in the scanning order. The screen 21 in FIG. 21 has five divided regions 22. The five divided regions 22 are arranged vertically along the scanning direction of the image light.

  The synchronization control unit 31 controls the optical states of the five divided regions 22 individually in synchronization with the one-dimensional vertical scanning of the screen 21 by the projector 11. When the image light is not projected, each divided region 22 is controlled to a non-image state, that is, a transparent transmissive state with small scattering of incident light.

  When the scanning of the image light is started, the scanning light of the projector 11 is first irradiated to the uppermost divided region 22 of the screen 21 as shown in FIG. Hereinafter, in this description, reference numeral 221 is used to distinguish the divided region 22 irradiated with the scanning light from other divided regions 22 that are not scanned. The synchronization control unit 31 specifies a period during which the uppermost divided area 221 is scanned in the scanning cycle based on the synchronization signal from the projector, and controls the uppermost divided area 221 to the video state. The image light that scans the uppermost divided area 221 is scattered by the divided area 221 in the scattering state and passes through the screen 21.

  Next, the scanning of the image light moves to the second divided region 221 from the top of the screen 21 as shown in FIG. The synchronization control unit 31 specifies a period during which the second divided region 221 from the top in the scanning cycle is scanned, and controls the second divided region 221 from the top to the video state. The image light that scans the second divided region 221 from the top is scattered by the divided region 221 in the scattering state and passes through the screen 21. Further, the synchronization control unit 31 controls the second divided area 221 from the top to the video state, and then controls the uppermost divided area 22 to the non-video state. Thereafter, as shown in FIGS. 21C to 21E, the synchronization control unit 31 controls the divided area 221 scanned by the scanning light to the video state, and sets the other divided areas 22 to the non-video state. Control.

  Through the above-described synchronization control, the portion of the screen 21 irradiated with the scanning light is maintained in the video state. Thereby, the image light that scans the screen 21 is scattered by the screen 21 in the scattering state. Further, the portion of the screen 21 that is not irradiated with the scanning light is controlled to a non-image state. Each divided region 22 is controlled to a transparent transmission state in a non-video state during most of the period when it is not scanned with scanning light. During the image light projection period, the see-through characteristic of the screen 21 is obtained while maintaining the image visibility.

  FIG. 22 shows a description of the projection method of the projector 11 according to the present embodiment. FIG. 22 is an explanatory diagram of the projector 11 that scans the screen 21. FIG. 22A is an explanatory diagram of a projection method in which the projector 11 scans the screen 21. In this case, video light is always projected onto the screen 21 during the scanning cycle. However, when attention is paid to each part of the screen 21, the image light is projected in a part of the scanning cycle as shown in FIG. For this reason, as shown in FIG. 22C, each part of the screen may be in a scattering state in the partial scanning period TP in which each part is scanned. Further, if each part of the screen 21 is controlled so as to increase the parallel light transmittance in a period other than the partial scanning period TP, the see-through characteristic of the screen 21 can be achieved without causing a decrease in the luminance of the image in the scanning period. can get.

  When the light is divided into strips in one direction like the screen 21 shown in FIG. 20, the projection light of the projector 11 is sequentially scanned in the division direction of the screen 21. Based on the synchronization signal from the projector 11, the synchronization control unit 31 sets the plurality of divided regions 22 so that the part irradiated with the projection light of the projector 11 is maintained in the video state (scattering state in this embodiment). In the scanning order, the transparent transmission state is controlled to the scattering state. By this synchronization control, each divided region 22 of the screen 21 is in a scattering state as a video state in a period Ton (see FIG. 23) including a video period in which projection light is irradiated on the region. Further, in the non-image period Toff (see FIG. 23) where the projection light is not irradiated, a transparent transmission state as a non-image state is obtained.

  Therefore, the screen 21 can scatter and transmit the image light with the same brightness as the case where the screen 21 is always in a scattering state while having transparency that can recognize the object on the back surface. That is, it is possible to achieve both a see-through property capable of recognizing a background object and a high image visibility.

  FIG. 23 is a schematic timing chart of scanning and driving of the screen 21. The horizontal axis is time. The vertical axis indicates the position in the vertical direction of the screen, and corresponds to a plurality of divided regions 22 on the screen 21.

  Each divided region 22 of the screen 21 is controlled from a transparent transmission state to a scattering state before the timing at which the image light starts to scan each region. Further, the divided region 22 in the scattering state is controlled from the scattering state to the transparent transmission state after the scanning of the region is completed.

  The plurality of divided regions 22 are controlled in the image state (scattering state) in synchronization with the partial scanning period TP in which the image light is irradiated to each region, thereby sequentially shifting the time in the scanning order. Switch to video state. The image light that scans the screen 21 is efficiently scattered by the portion maintained in the image state, and it is possible to obtain bright and high visibility. In FIG. 23, the image light scanning is indicated by three arrows, which indicate image lights corresponding to the three primary colors of red, green and blue light.

  By the above synchronization control, the screen 21 can display an image because the portion irradiated with the image light is maintained in the scattering state in the period Ton including the timing when the image light is irradiated.

  Moreover, since the screen 21 is controlled to be in a transparent transmissive state at times other than the period Ton during the projection period of the image light, the screen 21 can be seen through. Since the light transmitted through the screen 21 appears to be averaged (integrated) to the human eye, a see-through characteristic without flicker is obtained in a sufficiently short scanning period.

  FIG. 24 shows a circuit configuration example of the synchronization control unit 31 when the screen 21 having the above-described configuration is used. In FIG. 24, the drive control signal generation unit 311, the detection resistor Rcom, and the differential amplifier 313 a have the same configuration as shown in FIG. That is, the detection resistor Rcom is connected in series only between the common electrode 26 as the first electrode and the drive control signal generation unit 311.

  It is assumed that the screen 21 is divided into five areas A to E. Therefore, an equivalent circuit in which the resistance of one electrode, the capacitance of the liquid crystal cell, and the other resistance are connected in series is configured for each region (the DC resistance component is not shown). For example, in the region A, the resistor Rsel11, the capacitance Csel11, and the resistor Rsel21 are connected in series.

  A protective resistor is also connected for each region. That is, as shown in FIG. 24, the protective resistor Rp1 is connected to the region A, the protective resistor Rp2 is connected to the region B, the protective resistor Rp3 is connected to the region C, and the protective resistor Rp4 is connected to the region D. Are connected, and a protective resistor Rp5 is connected to the region E.

  The drive control signal generation unit 312 is provided with signal generation circuits Vel1 to Vsel5 that generate drive control signals for each region.

  FIG. 25 shows drive waveforms of the circuit shown in FIG. FIG. 25 shows a drive waveform in a normal state. In FIG. 24, the common electrode voltage is a voltage waveform output by the drive control signal generation unit 311 (for example, a voltage waveform applied to the common electrode 26). The selection electrode A voltage is a voltage waveform output from the signal generation circuit Vsel1 corresponding to the region A (that is, the voltage waveform applied to one divided selection electrode 27), and the selection electrode B voltage is a signal corresponding to the region B. The voltage waveform output from the generation circuit Vsel2 and the selection electrode C voltage are the voltage waveforms output from the signal generation circuit Vsel3 corresponding to the region C. The selection electrode D voltage is the voltage waveform output from the signal generation circuit Vsel4 corresponding to the region D. The selection electrode E voltage is a voltage waveform output from the signal generation circuit Vsel5 corresponding to the region E.

  Region A in FIG. 25 (selection A-common) is a change in the scattering state and transmission state of region A, and the screen electrode voltage (solid line) and the scattering state of region A when the selection electrode A voltage and the common electrode voltage are applied. And a change in transmission state (dotted line). Hereinafter, the region B (selection B-common) to the region E (selection E-common) also show the screen electrode voltage, the scattering state of the region, and the change of the transmission state in the same manner.

  As in the second embodiment, the selection start signal is a signal that is output from the drive state control unit 314 to the drive control signal generation units 311 and 312 and instructs switching to the scattering state. As in the second embodiment, the selection end signal is a signal that is output from the drive state control unit 314 to the drive control signal generation units 311 and 312 and instructs switching to the transmission state. These selection start signal and selection end signal are output for each region. The selection start signal and the selection end signal are output in the order of the areas A to E.

  When a voltage waveform as shown in FIG. 25 is applied to the common electrode side and the selection electrode side, as in the second embodiment, when the potential difference between the common electrode voltage and the selection electrode voltage is generated, The transient response is superimposed on the voltage at the detection resistor terminal on the screen 21 side due to the relationship between the capacitance Csel and the CR circuit composed of the peripheral impedance. Therefore, at the timing when the selection start voltage and selection end voltage are switched, a detection signal corresponding to the transient response is output from the differential amplifier 313a as shown in the figure.

  As a result, the detection signal becomes a high level when the comparator 313b is below a certain threshold and is output as a pulse signal (of course, the pulse signal may be output when it is above the threshold). Then, the number of pulses in the common electrode voltage half-cycle period (one video period, for example, one frame period) is counted, and it can be determined whether or not it is normal by comparing with the preset normal value. . In addition, since the period of the scattering state and the waveform applied to the electrode are determined in advance, the timing at which the pulse signal is generated can be predicted in advance. Therefore, it is possible to determine whether the number of pulses is normal or not, and it is possible to detect in which region an abnormality has occurred based on the generation timing of the pulse signal.

  In the case of FIG. 25, the number of pulses is 6 when the common electrode voltage is 0 volts, and the number of pulses is 5 when the common electrode voltage is V volts.

  FIG. 26 shows an example in which the scattering period of the region extends over one frame period (one video cycle). Note that FIG. 26 is operating normally. In the case of FIG. 26, the regions C, D, and E extend over one frame period (period in which the common electrode voltage is 0 or V volts). That is, the period from the selection start signal to the selection end signal extends over a plurality of frame periods (see arrow ar in FIG. 26).

  Even in this case, it can be determined whether or not it is normal based on the number of pulse signals output from the comparator 313b. In the case of FIG. 26, the number of pulses is 6 when the common electrode voltage is 0 volts, and the number of pulses is 5 when the common electrode voltage is V volts.

  Here, for example, when a foreign object is mixed between the electrodes in the region C and short-circuiting occurs during use, or the short-circuit occurs and an overcurrent flows through the protective resistor Rp3, resulting in a high resistance state. The case will be described with reference to FIG.

  In such a case, since no voltage is applied to the region C, the region C is always in a transmissive state. Therefore, the projection light from the projector 11 leaks and the video is not only missing, but there is a possibility that the observer may look directly, and it is dangerous when looking directly for a long time.

  Therefore, with the configuration of the present embodiment, the detection signal corresponding to the transient response output from the differential amplifier 313a is not output at the timing corresponding to the region C. Therefore, the number of pulse signals output from the comparator 313b is smaller than that in the normal operation, and it can be determined that the state is abnormal. Further, by confirming the timing when the pulse signal is not output, the region where the abnormality has occurred can be identified.

  In other words, in this embodiment, the occurrence of an abnormality can be monitored in real time, and no detection signal is output at the start and end of selection of the location where the abnormality has occurred. can do. Therefore, based on this result, measures can be taken by forcibly dropping the projection light from the projector 11.

  According to the present embodiment, the selection electrode 27 is divided into a plurality of parts, and the detection resistor Rcom is connected between the common electrode 26 and the drive control signal generation unit 311. Therefore, the selection electrode 27 is divided, Even when each is driven individually, an abnormality in each divided region can be detected with one resistor on the common electrode 26 side.

  In the third embodiment, the selection start signal and the selection end signal may be close or overlap. In this case, the transient response related to the screen rise and the transient response related to the fall are canceled out, and the detection level may be lowered to be below the threshold (see FIG. 28). Then, although it is normal, it is erroneously determined as abnormal.

  In such a case, the time may be shifted so that the selection start signal and the selection end signal do not overlap (see FIG. 29). For example, if the selection start signal is controlled in a 10 μs step, the selection end signal may be controlled in a 10 μs step with a delay of 5 μs. As a result, a delay of 5 μs can be made. However, since the signal on the driving start side is easily canceled, depending on the case, it is possible to stably detect even if the scattering state changes by selecting the frame and detecting the number of pulses of the signal on the driving end side. Also good.

  Further, in the first to third embodiments described above, when an abnormality is detected, the projector 11 is stopped. However, this is not limited to turning off the power, but only light emission of the light source may be stopped. Further, a black image may be inserted without stopping. Further, a shutter or the like that blocks the projection light of the projector without controlling the projector 11 may be provided between the projector 11 and the screen 21. In short, it suffices if projection light does not reach the screen 21.

  In the first to third embodiments described above, when the voltage output from the common electrode voltage and the selection electrode voltage is excessively higher than the threshold voltage in order to speed up the change (rise) to the scattering state. A phenomenon that the degree of scattering decreases after the scattering characteristics of the screen 21 reach the peak of scattering may occur. For this reason, a driving method (also referred to as overdrive) in which a first voltage is applied to speed up the start to the scattering state, and then a second voltage that can stably maintain the scattering state is applied. May be applied).

  A display control apparatus according to a fourth embodiment of the present invention will be described with reference to FIG. In the case of the present embodiment, the screen 21 is a dimming screen in which the image light is not projected and the transmittance can be arbitrarily changed. Such a screen 21 is used in place of, for example, a blind or a curtain so that the transmittance is adjusted as necessary so that the opposite side of the screen 21 cannot be seen (from the opposite side) or transmitted in a translucent manner. The rate can be adjusted to make it less visible.

  For example, in the configuration of FIG. 30, it is possible to make the tree 42 visible by changing the transmittance by, for example, the operation of the user or the like so that the tree 42 cannot be observed normally.

  Even in such a screen 21, when an abnormality occurs and the screen 21 is unintentionally transmitted, a problem arises in that what is originally desired to be hidden is visible.

  Therefore, by applying the synchronization control unit (display control device) 31 described in the first to third embodiments, it is not necessary to input an inspection signal or the like, and the screen 21 can be operated even during a normal operation such as blindfolding. Abnormalities can be detected.

  In addition, you may comprise as a computer program (display control program) which operate | moves by CPU etc. of the said microcomputer by utilizing the microcomputer (microcomputer) which can input the electric potential difference of the detection resistance Rcom mentioned above. In this way, a part of the synchronization control unit 31 can be caused to function in the computer.

  Further, the present invention is not limited to the above embodiment. That is, those skilled in the art can implement various modifications in accordance with conventionally known knowledge without departing from the scope of the present invention. Of course, such modifications are also included in the scope of the present invention as long as the configuration of the display control apparatus of the present invention is provided.

DESCRIPTION OF SYMBOLS 1 Display apparatus 11 Projector 21 Screen 25 Optical layer 26 Common electrode (1st electrode)
27 Selection electrode (second electrode)
31 Synchronization control unit (display control device)
311 Drive control signal generator (drive signal generator)
312 Drive control signal generator (drive signal generator)
313a Differential amplifier (detector)
313b Comparator (abnormal signal output unit)
314 Drive state control unit (abnormal signal output unit, projection control unit)
Rcom detection resistance (resistance)

In order to solve the above-mentioned problem, the invention according to claim 1 switches between a light transmission state and a light scattering state according to a first potential difference between two electrodes between which an image is intermittently projected and sandwiches an optical layer. A display control apparatus for a screen that is capable of generating a resistance connected to one of the two electrodes and a second signal generated at both ends of the resistance by a drive signal that generates the first potential difference within a predetermined period. An output unit that outputs a signal relating to the abnormality of the screen when the number of pulse signals indicating that the potential difference is greater than or less than a predetermined threshold value is different from a predetermined number of times. Yes.

According to the sixth aspect of the present invention, the screen display control is capable of switching between the light transmission state and the light scattering state by the first potential difference between the two electrodes sandwiching the optical layer, the image being projected intermittently. In the method, a second potential difference generated at both ends of a resistor connected to one of the two electrodes by a drive signal for generating the first potential difference within a predetermined period is greater than or equal to a predetermined threshold value or It is characterized in that it comprises as output Engineering the number of pulse signal indicating that a less outputs a signal relating to abnormality of the screen is different from the preset predetermined number of times.

The invention according to claim 7, the display control method according to claim 7, characterized in that is executed by a computer.

The invention of claim 8 is characterized in that storing a display control program according to claim 8.

Claims (14)

A screen display control apparatus having an optical layer sandwiched between a first electrode and a second electrode, and capable of changing a transmittance with respect to light by a potential difference between the first electrode and the second electrode. And
A drive signal generator connected to the first electrode and generating a drive signal for generating the potential difference;
A resistor connected in series with the first electrode and the drive signal generator, or in series with the second electrode;
A detection unit for detecting a potential difference generated at both ends of the resistor by the drive signal;
An abnormality signal output unit that outputs a signal relating to an abnormality of the screen based on the potential difference detected by the detection unit;
A display control device comprising: An image is intermittently projected and has an optical layer sandwiched between a first electrode and a second electrode, and a transmission state and a scattering state with respect to light due to a potential difference between the first electrode and the second electrode A display control device for a screen that can be switched between
A drive signal generator connected to the first electrode and generating a drive signal for generating the potential difference;
A resistor connected in series with the first electrode and the drive signal generator, or in series with the second electrode;
A detection unit for detecting a potential difference generated at both ends of the resistor by the drive signal;
An abnormality signal output unit that outputs a signal relating to an abnormality of the screen based on the potential difference detected by the detection unit;
A display control device comprising:   The display control apparatus according to claim 2, wherein the detection by the detection unit is performed during a period in which the image is projected on the screen.   The display control apparatus according to claim 2, further comprising: a projection control unit that controls the projection of the image so as not to reach the screen when a signal related to the abnormality is output.   5. The display according to claim 2, wherein the abnormality signal output unit outputs a signal relating to abnormality of the screen when the potential difference is equal to or greater than a predetermined threshold value. Control device.   The abnormal signal output unit is a signal relating to an abnormality of the screen when the number of pulse signals indicating that the potential difference is greater than or less than a predetermined threshold value within a predetermined period is different from a predetermined number of times. The display control apparatus according to any one of claims 2 to 4, wherein:   The display control apparatus according to claim 6, wherein the abnormality signal output unit outputs a signal related to abnormality of the screen based on a width of the pulse signal. The second electrode is divided into a plurality of pieces;
The display control device according to claim 2, wherein the resistor is connected between the first electrode and the drive signal generation unit. A screen display control method having an optical layer sandwiched between a first electrode and a second electrode and capable of changing the transmittance with respect to light by a potential difference between the first electrode and the second electrode. And
A drive signal generating step of generating a drive signal for generating the potential difference by applying to the first electrode;
A detection step of detecting a potential difference generated at both ends of a resistor connected in series with the first electrode and the drive signal generation unit or in series with the second electrode according to the drive signal;
An abnormal signal output step of outputting a signal relating to an abnormality of the screen based on the potential difference detected in the detection step;
A display control method comprising:   A display control program that causes a computer to execute the display control method according to claim 9.   A computer-readable recording medium storing the display control program according to claim 10. An image is intermittently projected and has an optical layer sandwiched between a first electrode and a second electrode, and a transmission state and a scattering state with respect to light due to a potential difference between the first electrode and the second electrode A display control method for a screen that can be switched between
A drive signal generating step of generating a drive signal for generating the potential difference by applying to the first electrode;
A detection step of detecting a potential difference generated at both ends of a resistor connected in series with the first electrode and the drive signal generation unit or in series with the second electrode according to the drive signal;
An abnormal signal output step of outputting a signal relating to an abnormality of the screen based on the potential difference detected in the detection step;
A display control method comprising:   A display control program that causes a computer to execute the display control method according to claim 12.   A computer-readable recording medium storing the display control program according to claim 13.

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