JP2008076971A - Optical modulating device, light source device, optical modulating element control circuit, and light source device control circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical modulating device capable of improving use efficiency of light without reference to the kind and constitution of an optical modulating element. <P>SOLUTION: An optical detector 2 detects part of light (modulated light L2) modulated by the optical modulating element 1. Further, a driving control unit 32 in a driving unit 3 controls a driving waveform of the optical modulating element 1 (liquid crystal element 12) based upon detected modulated light L3. Projection of irradiation light L0 emitted by a laser 10 is more precisely timed to operations of the liquid crystal element 12 without reference to the kind and constitution of the optical modulating element 1. Based upon the detected modulated light L3, the pulse waveform of the irradiation light L0 emitted by the laser 10 may be controlled. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a light modulation device and a light source device that include a light modulation element that modulates and outputs light from a light source, a light modulation element control circuit that controls such a light modulation element, and a light source device that controls the light source device. The present invention relates to a control circuit.

  Conventionally, a liquid crystal element or the like has been used as a light modulation element that modulates and outputs light from a light source. In particular, a ferroelectric liquid crystal element has a faster response speed than a normal TN (Twisted Nematic) mode liquid crystal element. Therefore, a light modulation element composed of a ferroelectric liquid crystal element is capable of high-speed optical switching. Used in optical systems that require

  FIG. 15 illustrates a configuration example of a conventional light modulation device (light source device) using a liquid crystal element as a light modulation element. This conventional light source device includes a light source 110 composed of a laser or the like, a liquid crystal element 112, a pair of polarizing plates 111A and 111B whose polarization axes are orthogonal to each other, a light source driving unit 134, and a liquid crystal element driving unit 133. ing. With such a configuration, the light L100 emitted from the light source 110 passes through the polarizing plate 111A and enters the liquid crystal element 112. When the light L100 is modulated in the liquid crystal element 112, the polarization angle rotates by 90 degrees, so that the light passes through the polarizing plate 111B as the modulated light L102 and is output from the light source device. On the other hand, when the light L100 is not modulated in the liquid crystal element 112, since the polarization angle does not rotate, the light is absorbed by the polarizing plate 111B and is not output from the light source device.

  Further, for example, Patent Document 1 discloses a technique in which an optical switching element (liquid crystal element) is used as an optical shutter (liquid crystal shutter) of an image display device by utilizing the optical switching characteristics of such an optical modulation element. ing.

JP 2001-75045 A

  By the way, in such a light modulation element, due to the response speed of the element (for example, rise time tr and fall time tf), the timing between the light emission timing of the light source and the operation timing of the light modulation element. There is a problem that a shift occurs. When such a timing shift occurs, the light modulation operation cannot be performed at a desired timing, so that the light use efficiency in the element is reduced. For example, when the light modulation element is applied to an image display device, display is performed. As a result, the image quality is degraded, for example, the contrast of the image is lowered.

  Here, in Patent Document 1, a change in the response time of the light modulation element (liquid crystal shutter) is detected, and the operation timing of the light modulation element is adjusted based on the detection result. Therefore, even when the response time fluctuates depending on the operating environment, it can be considered that it can cope with each time.

  However, in the technique of this Patent Document 1, it is only possible to cope with a change in response time to the last, and it is necessary to prepare the operation timing of the element in advance so as to match the response characteristic of the light modulation element. Therefore, for example, when the response characteristics of the elements differ due to differences in the constituent materials of the elements, it is necessary to optimize the operation timing each time.

  As described above, in the conventional technique, it is difficult to improve the light use efficiency regardless of the type and configuration of the light modulation element.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a light modulation device, a light source device, and a light modulation element capable of improving the light utilization efficiency regardless of the type and configuration of the light modulation element. It is to provide a control circuit and a light source device control circuit.

  The light modulation device of the present invention includes a light modulation element that modulates light from a light source and outputs modulated light, a detection unit that detects the modulated light, and a drive waveform of the light modulation element based on the detected modulated light And a control means for controlling.

  An optical modulation element control circuit according to the present invention is a control circuit applied to an optical modulation element that modulates light from a light source and outputs modulated light, the detection means for detecting the modulated light, and the detected modulation And a control means for controlling the drive waveform of the light modulation element based on the light.

  In the light modulation device and the light modulation element control circuit of the present invention, light (modulated light) emitted from the light source and modulated by the light modulation element is detected. Based on the detected modulated light, the drive waveform of the light modulation element is controlled. Therefore, the light emission timing from the light source and the operation timing of the light modulation element can be better matched regardless of the type and configuration of the light modulation element.

  In the light modulation device and the light modulation element control circuit according to the present invention, when the light source emits pulsed light, the control means controls the drive waveform of the light modulation element and the pulse waveform of the pulsed light. Is preferred. In such a configuration, since both the drive waveform of the light modulation element and the pulse waveform of the pulsed light are controlled, the light emission timing and light from the light source are compared with the case where only one control is performed. The operation timing of the modulation element can be further adapted.

  The light source device of the present invention includes a light source that emits pulsed light, a light modulation element that modulates the pulsed light and outputs modulated light, a detection unit that detects the modulated light, and a pulse based on the detected modulated light. And a control means for controlling the pulse waveform of light.

  A light source device control circuit according to the present invention is a control circuit applied to a light source device that modulates pulsed light emitted from a light source and outputs modulated light, and further includes a detection unit that detects the modulated light, And a control means for controlling the pulse waveform of the pulsed light based on the modulated light.

  In the light source device and the light source device control circuit of the present invention, pulsed light (modulated light) emitted from the light source and modulated by the light modulation element is detected. Based on the detected modulated light, the pulse waveform of the pulsed light is controlled. Therefore, the emission timing of the pulsed light from the light source and the operation timing of the light modulation element can be better matched regardless of the type and configuration of the light modulation element.

  The light modulation device, the light source device, the light modulation element control circuit, and the light source device control circuit of the present invention can be applied to a three-dimensional display device having the following configuration, for example.

  A three-dimensional display device according to a first aspect includes a light source, a plurality of pixels, a light modulation unit that modulates light from the light source for each pixel to generate a two-dimensional image, and each pixel of the light modulation unit Diffraction that collects diffraction light of multiple orders generated for each diffraction order for each diffraction order and forms a diffraction image for each diffraction order, which is an optical image in which all the information of the two-dimensional image generated by the light modulation means is aggregated A diffraction image selection means for sequentially selecting each of a plurality of diffraction images formed by the diffraction image formation means in synchronization with the generation timing of the two-dimensional image by the light modulation means; And a conjugate image forming means for forming a conjugate image of the diffraction image selected by the means. In this case, optical means for projecting the formed conjugate image may be further provided.

  In the three-dimensional display device according to the first aspect, a diffraction image, which is an optical image in which all the information of the two-dimensional image generated by the light modulation means is aggregated, is formed for each diffraction order. By using a diffraction image by high-order diffraction, a light beam group having a spatially high density is generated. In synchronization with the generation timing of the two-dimensional image by the light modulation means, each of the plurality of diffraction images is sequentially selected in time, and a conjugate image of the selected diffraction image is formed. By controlling the light beam group spatially and temporally by the diffraction image selection means, it is possible to modulate the intensity, phase, etc., which are attributes of each light beam.

  A three-dimensional display device according to a second aspect includes a light source, a plurality of pixels, a light modulation unit that modulates light from the light source for each pixel to generate a two-dimensional image, and a light modulation unit. A first lens that forms a Fourier transform image with respect to a spatial frequency in the generated two-dimensional image, a spatial filter that spatially and temporally filters the Fourier transform image, and an inverse Fourier transform of the Fourier transform image filtered by the spatial filter A second lens that forms a real image of a two-dimensional image generated by the light modulation means by conversion, and a third lens that forms a conjugate image of a Fourier transform image filtered by a spatial filter It is. In this case, the third lens may further have a function of projecting the conjugate image into an arbitrary space.

  In the three-dimensional display device according to the second aspect, the Fourier transform image for the spatial frequency in the two-dimensional image generated by the light modulation means is spatially and temporally filtered by the spatial filter, and the filtered Fourier transform is performed. A conjugate image of the image is formed.

  Here, in the three-dimensional display device according to the second aspect, the first lens is an optical image in which all information of the two-dimensional video generated by the light modulation unit is aggregated as a Fourier transform image, for example. A diffraction image is formed after spatially dividing each diffraction order. By using a diffraction image by high-order diffraction, a light beam group having a high spatial density is generated. Further, the spatial filter has, for example, a plurality of openings corresponding to the respective diffraction orders of the diffracted light generated in each pixel of the light modulation means, and a plurality of openings while being synchronized with the generation timing of the two-dimensional image by the light modulation means. Is subjected to optical and selective opening / closing control for each diffraction order to filter the Fourier transform image spatially and temporally. By controlling the light beam group of the Fourier transform image spatially and temporally, the intensity and phase of each light beam can be modulated.

  According to the light modulation device or the light modulation element control circuit of the present invention, the light modulated by the light modulation element (modulated light) is detected, and the drive waveform of the light modulation element is controlled based on the detected modulated light. Thus, the light emission timing from the light source and the operation timing of the light modulation element can be better matched regardless of the type and configuration of the light modulation element. Therefore, the light utilization efficiency can be improved regardless of the type and configuration of the light modulation element.

  In particular, in the case where the light source emits pulsed light, when the drive waveform of the light modulation element and the pulse waveform of the pulsed light are controlled, the light source from the light source is compared with the case where only one waveform is controlled. The light emission timing and the operation timing of the light modulation element can be further matched. Therefore, it is possible to further improve the light use efficiency.

  Further, according to the light source device or the light source device control circuit of the present invention, the pulsed light (modulated light) modulated by the light modulation element is detected, and the pulse waveform of the pulsed light is controlled based on the detected modulated light. Thus, the emission timing of the pulsed light from the light source and the operation timing of the light modulation element can be better matched regardless of the type and configuration of the light modulation element. Therefore, the light utilization efficiency can be improved regardless of the type and configuration of the light modulation element.

[First Embodiment]
FIG. 1 shows the overall configuration of an optical modulation apparatus according to the first embodiment of the present invention. The light modulation device includes a light modulation element 1, a light detection unit 2, and a drive unit 3.

  The laser 10 is a light source that emits irradiation light L0 composed of laser light, and is configured by, for example, a semiconductor laser or a solid-state laser.

  The light modulation element 1 modulates incident light and outputs it, and includes a liquid crystal element 12 and a pair of polarizing plates 11A and 11B disposed before and after the optical path with respect to the liquid crystal element 12. .

  The liquid crystal element 12 has a plurality of pixels arranged in a matrix, and controls the polarization angle of incident light for each pixel in accordance with a drive waveform supplied from the drive unit 3 described later. It is composed of a ferroelectric liquid crystal element. Further, as indicated by arrows in FIG. 1, the polarizing plates 11A and 11B are arranged so that their polarization axes are orthogonal to each other (so-called crossed Nicols arrangement), and incident according to the operation of the liquid crystal element 12. It is designed to transmit or block light. Details of operations of the liquid crystal element 12 and the polarizing plates 11A and 11B will be described later.

  The light detection unit 2 includes a half mirror 21 disposed on an optical path of light (modulated light L2) modulated by the light modulation element 1, a photodetector 22 that is a light detector, and a comparator 23.

  The half mirror 21 reflects a part of the modulated light L2 while transmitting it, and guides the reflected light to the photodetector 22 as detection light L3. The photodetector 22 detects the detection light L3, converts the temporal change in the amount of light into a temporal change in voltage, and outputs it. The comparator 23 compares the magnitude of the detection signal potential (analog data) based on the detection light L2 output from the photodetector 22 with a predetermined potential (for example, a potential of 50% of the maximum potential in the detection signal). The comparison result is output, whereby a binarized signal SC which is a binarized detection signal is output.

  The drive unit 3 drives the laser 10 and the liquid crystal element 12, and includes a phase comparison unit 31, a drive control unit 32, a liquid crystal element drive unit 33, and a light source drive unit 34.

  The liquid crystal element drive unit 33 drives the liquid crystal element 12 with a predetermined drive signal SA. The light source driver 34 drives the laser 10 with a predetermined drive signal.

  As described above, the phase comparison unit 31 refers to the drive signal SA supplied from the liquid crystal element drive unit 33 to the liquid crystal element 12, and also outputs the drive signal (reference signal) SA and the binarized signal SC output from the comparator. And the comparison result is output to the drive control unit 32. The details of the phase difference comparison operation will be described later.

  The drive control unit 32 controls the drive operation of the liquid crystal element drive unit 33 and the light source drive unit 34 based on the comparison result from the phase comparison unit 31. The details of the control of these driving operations will be described later.

  Next, the operation of the light modulation device of this embodiment will be described in detail.

  In this light modulation device, the laser 10 is driven by the light source driving unit 34, and the irradiation light L0 is emitted from the laser 10. The irradiation light L0 passes through the polarizing plate 11A and enters the liquid crystal element 12.

  In the liquid crystal element 12, for example, in the case of a ferroelectric liquid crystal element, the liquid crystal element driving unit 33 operates as shown in FIGS. 2 and 3 for each pixel. Modulation is performed in the liquid crystal element 12. Specifically, first, in the case of a ferroelectric liquid crystal element, the potential Vcom of a common electrode (not shown) in the liquid crystal element is set in the waveform of the drive signal SA (FIGS. 2B and 3B). Since it is necessary to take DC (direct current) balance as a reference, the waveform of the drive signal SA is positive (drive voltage is (+ V1)) and negative (drive voltage is (−V1)). In the case of positive polarity, the polarization angle of the incident light on the liquid crystal element 12 is rotated by 90 °, whereas in the case of negative polarity, the incident light enters the liquid crystal element 12. The polarization angle of light is not rotated.

  Also, in the waveform of the irradiation light L0 from the laser 10, a period in which the irradiation light L0 is emitted (period in which the light source is in an on state: an active period) and a period in which the irradiation light L0 is not emitted (in the light source is in sync) with the waveform of the drive signal SA. (OFF period: inactive period) appear alternately (FIG. 2 (A), FIG. 3 (A)), so that pulse irradiation is performed.

  Therefore, for example, as shown in FIG. 2, in the pixel in which the drive signal SA is positive during the active period in which the irradiation light L0 is emitted, the polarization angle of the irradiation light L0 incident on the liquid crystal element 12 is rotated by 90 °. As a result, the modulated light L1 passes through the polarizing plate 11B, so that the modulated light L2 is output from the light modulation element 1, and a so-called white display state is obtained. On the other hand, as shown in FIG. 3, for example, in a pixel in which the drive signal SA has a negative polarity during the active period in which the irradiation light L0 is emitted, the polarization angle of the irradiation light L0 incident on the liquid crystal element 12 does not rotate. When the modulated light L1 is blocked by the polarizing plate 11B, the modulated light L2 is not output from the light modulation element 1, and a so-called black display state is obtained.

  Here, the liquid crystal element 12 has a response time (for example, a rise time tr or a fall time tf) according to, for example, a constituent material of the liquid crystal, a driving voltage, a temperature of the element, and the like. It does not operate in the form of a pulse wave like the signal SA.

  Therefore, for example, the conventional light source device (light modulation device) shown in FIG. 15 operates as shown in FIG. 4 and FIG. Specifically, in the white display state shown in FIG. 4, the liquid crystal element 112 actually corresponds to the dotted line in FIG. 4B with respect to the pulse waveform of the drive signal S100 (solid line in FIG. 4B). The rise time tr and fall time tf are generated. For this reason, in the modulated light L102 (FIG. 4C) output from the liquid crystal element 112, the amount of the modulated light L102 in the active period is reduced by an amount corresponding to the region of the code P101 generated by the rise time tr, In the area P102 generated by the rise time tf, the irradiation light L100 is not emitted because it is within the inactive period (FIG. 4A), so the modulated light L102 is not output and does not contribute to the increase in the light amount. . Therefore, in the white display state, the light amount (luminance) of the modulated light L102 is reduced by the rise time tf compared to the ideal state. Here, the rise time tr and the rise time tf are defined as the time from when the drive signal rises or when the drive signal falls until the amount of modulated light reaches 50%.

  Similarly, in the black display state shown in FIG. 5, the liquid crystal element 112 actually has the same waveform as that shown in FIG. 5B with respect to the pulse waveform of the drive signal S100 (solid line in FIG. 5B). It operates like a dotted line, and rise time tr and fall time tf occur. Therefore, in the modulated light L102 (FIG. 5C) output from the liquid crystal element 112, the modulated light L102 is output in the active period by an amount corresponding to the area of the code P103 generated by the fall time tf, and leakage occurs. Light is produced. Therefore, in the black display state, the light amount (luminance) of the modulated light L102 increases due to the fall time tf compared to the ideal state.

  As described above, in the conventional light modulation device, the light amount (luminance) of the modulated light L102 is reduced by the rise time tr in the white display state as compared with the ideal state, while the fall time tf in the black display state. As a result, the amount of light (brightness) of the modulated light L102 increases compared to the ideal state. For example, when this light modulation device is applied to an image display device, the contrast of the display image is lowered and the image quality is deteriorated. It will end up.

  Therefore, in the light modulation device of the present embodiment, the modulated light L2 output from the light modulation element 1 is detected, and the drive waveform (the waveform of the drive signal SA) of the liquid crystal element 12 is controlled based on the detected modulated light. It has come to be. Specifically, first, a part of the modulated light L2 from the light modulation element 1 reflected by the half mirror 21 is detected by the photodetector 22 as detection light L3, and a detection signal SB is output. The SB is binarized by the comparator 23 and output to the phase comparison unit 31 in the drive unit 3 as a binarized signal SC.

  Next, in the case of the white display state, the phase comparison unit 31 has a phase difference between the drive signal SA (FIG. 6B) and the binarized signal SC (FIG. 6D), for example, as shown in FIG. Are compared, and the value of the rise time tr which is the comparison result is output to the drive control unit 32. On the other hand, in the black display state, for example, as shown in FIG. 7, the phase difference between the drive signal SA (FIG. 7B) and the binarized signal SC (FIG. 7D) is compared. The resulting fall time tf value is output to the drive control unit 32.

  Then, by the drive control unit 32, for example, in the case of a white display state, the drive waveform is moved forward on the time axis by the length of the rising time tr, for example, from the drive signal SA to the drive signal SA ′ (FIG. 6E). The driving operation of the liquid crystal element driving unit 33 is controlled so as to shift to. As a result, the modulated light L2 ′ after the drive control is as shown in FIG. 6F, for example, and the region where the amount of light decreases is changed from the region P1 to the code P1 in the modulated light L2 (FIG. 6C). It will be reduced to the area of 'a. Depending on the length of the fall time tf, the amount of the modulated light L2 ′ is reduced not only for the area of the code P1′a but also for the area of the code P1′b shown in FIG. However, even in such a case, the amount of decrease in the amount of light is smaller than that of the original area P1.

  On the other hand, for example, in the case of a black display state, the drive waveform is moved forward on the time axis by an amount corresponding to the length of the fall time tf, for example, from the drive signal SA to the drive signal SA ′ (FIG. 7E). The driving operation of the liquid crystal element driving unit 33 is controlled so as to shift to. Thereby, the modulated light L2 ′ after the drive control is as shown in FIG. 7F, for example, and an area corresponding to the amount of leakage light in the modulated light L2 is in the modulated light L2 (FIG. 7C). The area is reduced from the area P3 to the area P3′a. Depending on the length of the rise time tr, in addition to the area P3′a, the area P3′b shown in FIG. 7F also corresponds to the amount of leaked light. Even in such a case, the amount of leaked light is reduced as compared with the original area P3.

  As described above, in the present embodiment, a part of the light (modulated light L2) modulated by the light modulation element 1 by the light detection unit 2 is detected, and the inside of the drive unit 3 is based on the detected modulated light L3. Since the drive control unit 32 controls the drive waveform of the light modulation element 1 (liquid crystal element 12), the emission timing of the irradiation light L0 emitted from the laser 10 and the operation timing of the liquid crystal element 12 are improved. Can fit. Further, the timing can be adapted regardless of the type and configuration of the light modulation element. Therefore, it is possible to improve the light utilization efficiency regardless of the type and configuration of the light modulation element 1. For example, when this light modulation device is applied to an image display device, the contrast of the display image is increased and the image quality is improved. Can be improved.

  In this embodiment, the case where the drive waveform is controlled by shifting the drive waveform of the light modulation element 1 (liquid crystal element 12) on the time axis has been described. However, the rise time tr and the rise of the drive waveform are described. The drive waveform may be controlled by changing the pulse width of the drive waveform depending on how the fall time tf is taken.

[Second Embodiment]
Next, a second embodiment of the present invention will be described. In the first embodiment, the light modulation device that controls the driving waveform of the liquid crystal element based on the detected modulated light has been described. However, the light modulation device (light source device) of the present embodiment uses the detected modulated light. And the configuration of the apparatus is the same as the configuration of the first embodiment shown in FIG. In addition, the same code | symbol is attached | subjected to the same thing as the component in 1st Embodiment, and description is abbreviate | omitted suitably.

  8 and 9 show the operation of the light modulation device (light source device) according to the present embodiment in a timing waveform. FIG. 8 shows a case of a white display state, and FIG. 9 shows a case of a black display state. Respectively.

  In the light modulation device (light source device) of the present embodiment, a part of the modulated light L2 from the light modulation element 1 is detected in the same manner as in the first embodiment, and the rise time tr is based on this detection light L3. Alternatively, when the falling time tf is output from the phase comparison unit 31, the drive control unit 32 controls the driving operation of the light source driving unit 34, and the pulse waveform of the irradiation light L0 that is the pulsed light emitted from the laser 10 is controlled. The

  Specifically, in the case of the white display state, for example, as shown in FIG. 8E, the irradiation light L0 to the irradiation light L0 ′ by an amount corresponding to the length of the rise time tr (FIG. 8E )), The driving operation of the light source driving unit 34 is controlled so that the pulse waveform of the irradiation light shifts backward on the time axis. As a result, in the modulated light L2 ″ after drive control, the light amount reduction area is reduced from the area of the code P1 to the area of the code P1 ″ a in the modulated light L2 (FIG. 8C). Depending on the length of the fall time tf, the amount of the modulated light L2 ″ is reduced not only in the area of the code P1 ″ a but also in the area of the code P1 ″ b shown in FIG. 8C. However, even in such a case, the amount of decrease in the amount of light is smaller than that of the original area P1 (for example, as shown in FIG. 8F), the length of the rise time tr. The driving operation of the light source driving unit 34 may be controlled so that the pulse width of the pulse waveform of the irradiation light is narrowed, such as the irradiation light L0 to the irradiation light L0 ″. Is reduced to the area indicated by reference symbol P1 ″ a, and the amount of decrease in the amount of light can be further reduced.

  On the other hand, in the black display state, for example, as shown in FIG. 9 (E), the irradiation light L0 to the irradiation light L0 ′ corresponding to the length of the fall time tf (FIG. 9 (E)). The driving operation of the light source driving unit 34 is controlled so that the pulse waveform of the irradiation light shifts backward on the time axis. As a result, in the modulated light L2 ″ after the drive control, the leakage light region is reduced from the region of the code P3 to the region of the code P3 ″ a in the modulated light L2 (FIG. 9C). Depending on the length of the rising time tr, in addition to the area of the code P3 ″ a, the area of the code P3 ″ b shown in FIG. 9C also corresponds to the leakage light of the modulated light L2 ″. Even in such a case, the amount of leaked light is smaller than that of the original area P3, for example, as shown in FIG. The driving operation of the light source driving unit 34 may be controlled so that the pulse width of the pulse waveform of the irradiation light becomes narrower by an amount corresponding to the irradiation light L0 to the irradiation light L0 ″. The area of the amount of leaked light is reduced to the area indicated by the symbol P3 ″ a, and the quantity of leaked light can be further reduced.

  As described above, in the present embodiment, a part of the light (modulated light L2) modulated by the light modulation element 1 by the light detection unit 2 is detected, and the inside of the drive unit 3 is based on the detected modulated light L3. Since the drive control unit 32 controls the pulse waveform of the irradiation light L0 emitted from the laser 10, the emission timing of the irradiation light L0 emitted from the laser 10 and the operation timing of the liquid crystal element 12 are better adapted. Can do. Further, the timing can be adapted regardless of the type and configuration of the light modulation element. Therefore, also in the present embodiment, it becomes possible to improve the light use efficiency regardless of the type and configuration of the light modulation element 1. For example, when this light modulation device (light source device) is applied to an image display device It is possible to increase the contrast of the display image and improve the image quality.

  Although the present invention has been described with reference to the first and second embodiments, the present invention is not limited to these embodiments, and various modifications can be made.

  For example, as shown in FIG. 10 (in the case of a white display state) and FIG. 11 (in the case of a black display state), the control of the drive waveform of the liquid crystal element 12 described in the first embodiment, You may make it carry out combining both with control of the pulse waveform of the irradiation light L0 demonstrated in embodiment. When configured in this manner, it is possible to further improve the light use efficiency as compared with the first and second embodiments.

  In the above embodiment, the case where the drive waveform of the liquid crystal element 12 or the pulse waveform of the irradiation light L0 is controlled based on the detected modulated light L2 has been described. For example, FIG. 12 (in the white display state) and As shown in FIG. 13 (in the case of the black display state), for example, by changing the voltage (drive voltage) of the drive waveform of the drive signal SA or the temperature of the liquid crystal element 12 based on the detected modulated light L2, The response time of the liquid crystal element 12 may be shortened (the inclination at the time of rising or falling is increased) so that the rising time tr or the falling time tf is shortened. Specifically, the driving voltage is controlled to be high, or the temperature of the liquid crystal element 12 is controlled to be high by, for example, a Peltier element. Even in such a configuration, as shown in FIGS. 12 and 13, it is possible to reduce the amount of adjustment light reduced during white display and the amount of leakage light during black display. Specifically, for example, when the drive voltage is set to be 67% higher, the rise time tr can be reduced to 67% of the original time, for example, and the fall time tf can be reduced to 78% of the original time, for example. can do. For example, when the temperature of the liquid crystal element 12 is set to be 60% higher, for example, the rise time tr can be reduced to 54% of the original time, for example, the fall time tf can be reduced to 64% of the original time. can do. Further, for example, when the drive voltage is set to be 67% higher and the temperature of the liquid crystal element 12 is set to be 60% higher, for example, the rise time tr can be reduced to 29% of the original time, for example, the fall time tf Can be reduced to 40% of the original time. The driving waveform of the liquid crystal element 12 and the control of the pulse waveform of the irradiation light L0 may be used in combination.

  In the above embodiment, the rise time tr and the fall time tf are defined as 50% of the light amount of the modulated light L2, but the present invention is not limited to this. Further, instead of determining the phase difference from only one point, the determination may be made from a plurality of points. In addition, the drive waveform of the drive waveform liquid crystal element 12 and the pulse waveform of the irradiation light L0 are not controlled based on the rise time tr or the fall time tf itself, but the drive waveform based on the rise time tr or the fall time tf. Alternatively, the drive waveform and the pulse waveform may be controlled by adjusting the shift amount of the pulse waveform and the pulse width change amount. Furthermore, the control of the drive waveform and the pulse waveform may be performed in another timing region that is not used for image display (for example, a timing region such as the beginning of a frame).

  The positions of the half mirror 21 and the photodetector 22 may be any positions on the optical path as long as the modulated light L2 can be detected.

  Moreover, although the case where the light source of irradiation light L0 was comprised with the laser was demonstrated in the said embodiment, you may comprise with a light emitting diode (LED; Light Emitting Diode) etc. other than a laser, for example.

  In the above embodiment, the liquid crystal element 12 is a ferroelectric liquid crystal element. However, the liquid crystal element 12 may be a liquid crystal element other than the ferroelectric liquid crystal element, and may be a light modulation element other than the liquid crystal element.

  Furthermore, in the above-described embodiment, the transmission type light modulation element that modulates the irradiation light L0 while transmitting it has been described. However, a reflection type light modulation element that modulates the irradiation light L0 while reflecting it may be used.

  The light modulation device of the present invention can be applied to, for example, the light modulation element 1 (two-dimensional spatial light modulator) or the spatial filter 6 in a three-dimensional display device as shown in FIG. By configuring in this way, it is possible to generate a large amount of light groups with a spatial density higher than that of the conventional apparatus and a single device shown in FIG. Specifically, the three-dimensional display device shown in FIG. 14 (configuration when the light modulation device of the present invention is applied to the light modulation element 1) includes a light source 10 and an illumination optical system that shapes light from the light source 1. 2, an SLM (spatial light modulator: light modulation element) 1 that generates a two-dimensional image by modulating light from a light source for each pixel, and a spatial light modulator 1. A first lens 51 for forming a Fourier transform image with respect to a spatial frequency in a two-dimensional image, and a spatial filter 6 capable of temporal aperture control for spatially and temporally filtering the Fourier transform image are provided. . The three-dimensional display device further forms a real image (inverse Fourier transform image) 7 of the two-dimensional image generated by the spatial light modulator 1 by performing inverse Fourier transform on the Fourier transform image filtered by the spatial filter 6. A second lens 52 and a third lens 53 that forms a conjugate image 8 of the Fourier transform image filtered by the spatial filter 6 are provided. Note that f1 indicates the focal length of the first lens 51, f2 indicates the focal length of the second lens 52, and f3 indicates the focal length of the third lens 53. The spatial light modulator 1 corresponds to a specific example of “light modulation means”. The first lens 51 corresponds to a specific example of “diffraction image forming unit”. The spatial filter 6 corresponds to a specific example of “diffraction image selection unit”. The second lens 52 and the third lens 53 correspond to a specific example of “conjugated image forming unit”. According to the three-dimensional display device having such a configuration, the Fourier transform image with respect to the spatial frequency in the two-dimensional image generated by the spatial light modulator 1 is spatially and temporally filtered by the spatial filter 6 and filtered. Since the conjugate image 8 of the Fourier transform image is formed, it is possible to generate and scatter the light beam group with high spatial density without increasing the size of the entire apparatus. In addition, individual light beams that are constituent elements of the light beam group can be independently controlled in time and space. As a result, it is possible to obtain a stereoscopic image by light rays having the same quality as a real-world object.

It is a block diagram showing the structure of the light modulation apparatus which concerns on the 1st Embodiment of this invention. It is a timing waveform diagram for explaining the basic operation at the time of white display. It is a timing waveform diagram for explaining the basic operation at the time of black display. It is a timing waveform diagram showing the operation at the time of white display according to a comparative example. It is a timing waveform diagram showing the operation at the time of black display according to a comparative example. It is a timing waveform diagram for explaining the element drive waveform control operation at the time of white display according to the first embodiment. FIG. 6 is a timing waveform diagram for explaining an element drive waveform control operation during black display according to the first embodiment. It is a timing waveform diagram for demonstrating the emission waveform control operation at the time of the white display which concerns on the 2nd Embodiment of this invention. It is a timing waveform diagram for demonstrating the emission waveform control operation at the time of the black display which concerns on 2nd Embodiment. It is a timing waveform diagram for demonstrating control operation | movement of the element drive waveform at the time of the white display which concerns on the modification of this invention, and an emitted waveform. It is a timing waveform diagram for demonstrating control operation | movement of the element drive waveform at the time of the black display which concerns on the modification of this invention, and an emitted waveform. It is a timing waveform diagram for demonstrating the element drive waveform control operation | movement at the time of the white display which concerns on the modification of this invention. It is a timing waveform diagram for demonstrating the element drive waveform control operation at the time of the black display which concerns on the modification of this invention. It is a block diagram showing the example of a structure at the time of applying the light modulation apparatus shown in FIG. 1 to a three-dimensional display apparatus. It is a block diagram showing the structural example of the conventional light modulation apparatus (light source device).

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Light modulation element, 10 ... Laser, 11A, 11B ... Polarizing plate, 12 ... Liquid crystal element, 2 ... Light detection part, 21 ... Half mirror, 22 ... Photo detector, 23 ... Comparator, 3 ... Drive part, 31 ... Phase comparison 32, drive control unit, 33 ... liquid crystal element drive unit, 34 ... light source drive unit, 4 ... illumination optical system, 51-53 ... first to third lenses, 6 ... spatial filter, 7 ... two-dimensional image Real image (inverse Fourier transform image), 8 ... conjugate image of Fourier transform, L0, L0 ', L0 "... irradiation light, L1, L2, L2' ... modulated light, L3 ... detection light, SA, SA '... drive signal ( Reference signal), SB ... detection signal, SC ... binarized signal, tr ... rise time, tf ... fall time, Vcom ... common electrode potential, V1 ... drive voltage.

Claims (22)

A light modulation element that modulates light from the light source and outputs modulated light; and
Detecting means for detecting the modulated light;
And a control means for controlling a drive waveform of the light modulation element based on the detected modulated light. The light modulation apparatus according to claim 1, wherein the control unit shifts the drive waveform on a time axis. 3. The optical modulation device according to claim 2, wherein the control unit shifts the drive waveform forward on the time axis by an amount corresponding to a length of a rise time or a fall time of the drive waveform. The light modulation device according to claim 1, wherein the control unit changes a voltage of the drive waveform. The light modulation device according to claim 4, wherein the control unit performs control so that a voltage of the driving waveform is increased. The light modulation device according to claim 1, wherein the control unit changes a temperature of the light modulation element. The light modulation device according to claim 6, wherein the control unit controls the temperature of the light modulation element to be high. The light source emits pulsed light;
The light modulation device according to claim 1, wherein the control unit controls a drive waveform of the light modulation element and a pulse waveform of the pulsed light. The light modulation device according to claim 8, wherein the control unit shifts the pulse waveform on a time axis. The light modulation device according to claim 9, wherein the control unit shifts the pulse waveform backward on the time axis. The light modulation device according to claim 8, wherein the control unit changes a pulse width of the pulsed light. The light modulation device according to claim 11, wherein the control unit controls the pulse light to have a narrow pulse width. The light modulation device according to claim 1, wherein the light modulation element is a ferroelectric liquid crystal element. A light source that emits pulsed light;
A light modulation element that modulates the pulsed light and outputs modulated light; and
Detecting means for detecting the modulated light;
And a control unit that controls a pulse waveform of the pulsed light based on the detected modulated light. The light source apparatus according to claim 14, wherein the control unit shifts the pulse waveform on a time axis. The light source device according to claim 15, wherein the control unit shifts the pulse waveform backward on the time axis. The light source apparatus according to claim 14, wherein the control unit changes a pulse width of the pulsed light. The light source device according to claim 17, wherein the control unit controls the pulse light to have a narrow pulse width. The light source device according to claim 14, wherein the light modulation element is a ferroelectric liquid crystal element. A control circuit applied to a light modulation element that modulates light from a light source and outputs modulated light,
Detecting means for detecting the modulated light;
And a control means for controlling a drive waveform of the light modulation element based on the detected modulated light. The light source emits pulsed light;
21. The light modulation element control circuit according to claim 20, wherein the control unit controls a drive waveform of the light modulation element and a pulse waveform of the pulsed light. A control circuit applied to a light source device that modulates pulsed light emitted from a light source and outputs modulated light,
Detecting means for detecting the modulated light;
And a control means for controlling a pulse waveform of the pulsed light based on the detected modulated light.

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