JP4779534B2 - Optical scanning display - Google Patents

Description

  The present invention relates to a technique for displaying an image by two-dimensional scanning of a light beam, and more particularly to a technique for controlling the scanning trajectory.

  An optical scanning display that displays an image by two-dimensional scanning of a light beam is already known (for example, see Patent Document 1). One example is a projector that projects and displays an image on a screen assigned to the outside of the viewer, and another example projects a light beam directly on the retina of the viewer and scans the retina with that light beam. It is a retinal scanning display.

  In any example, this type of optical scanning display generally includes (a) a light source unit that emits a light beam with a luminance corresponding to a luminance signal, and (b) a main light beam that intersects the light beam emitted from the light source unit. A scanning device capable of reciprocating scanning in each of the scanning direction and the sub-scanning direction; and (c) generating the luminance signal based on the video signal and outputting the generated luminance signal to the light source unit. And a control unit for controlling a scanning trajectory by the scanning device.

  In this type of optical scanning display, the main scanning direction is normally set to be equal to the horizontal direction and the sub-scanning direction is set to be equal to the vertical direction. Therefore, scanning in the main scanning direction is horizontal scanning and scanning in the sub-scanning direction. Is referred to as vertical scanning, but the direction of each scanning direction is not limited thereto.

In this type of optical scanning display, the scanning device effectively scans an actual scanning line by actually emitting a light beam during the effective scanning period of the entire period of each round-trip scanning. On the other hand, during the invalid scanning period, the light source unit does not actually emit a light beam, so that a non-existent scanning line is formed as an invalid scanning line.
Japanese Patent No. 2988457

  In this type of optical scanning display, the scanning device is usually configured to perform reciprocal scanning in the sub-scanning direction while performing reciprocal scanning in the main scanning direction for each frame of the image.

  As a method of scanning a light beam to display an image, there are a non-interlace method (also referred to as a progressive method) and an interlace method. In the non-interlace method, all effective scanning lines for displaying an image of one frame are sequentially scanned one by one. On the other hand, in the interlace method, one frame of an image is composed of two fields, and these fields are scanned so that the scanning lines do not overlap each other.

  When the interlace method is adopted, the main scanning frequency can be lowered to, for example, half of the main scanning frequency while keeping the sub-scanning frequency high (for example, at a frequency of 50 Hz or more) to such an extent that flicker is not noticeable. It is possible to suppress a decrease in resolution in the sub-scanning direction (vertical direction) to some extent while maintaining the resolution in the main scanning direction (horizontal direction).

  Therefore, when the interlace method is adopted, the effective scanning line per screen (which corresponds to a field in the interlace method and a frame in the non-interlace method), which is the minimum unit of image display, is a non-interlace method. It is halved compared to the case of using the interlace method.

  Therefore, when the interlace method is adopted, it is easier to lower the required main scanning frequency than when the non-interlace method is adopted, in other words, it is easy to increase the necessary sub-scanning frequency.

  If the resonance phenomenon of the mechanical resonance system is used to scan the light beam, the power consumption due to the scanning can be easily reduced. Therefore, for example, a scanning mirror that deflects an incident light beam by reflection can be configured as a mechanical resonance system, and the deflection angle of the light beam can be periodically changed by the reciprocating motion of the scanning mirror.

  Against this background, in the above-described optical scanning display, in order to save power consumption by the scanning device, the scanning device (a) converts the luminous flux into the first light beam based on the main scanning drive signal. A main scanning unit capable of reciprocating scanning in the main scanning direction using the mechanical resonance system of (1), and (b) a second mechanical resonance system based on the sub-scanning drive signal. In some cases, it may be configured to have a sub-scanning unit capable of reciprocating scanning in the sub-scanning direction.

  In the optical scanning display using the scanning device configured as described above, the ratio of the main scanning frequency and the sub-scanning frequency is maintained at the set ratio, and the spot of the light beam incident on the retina is scanned by the scanning device. This is important because the actual scanning trajectory drawn on the retina is normal.

  In this type of optical scanning display, the height of the main scanning frequency depends on the vibration frequency of the first mechanical resonance system, and similarly, the height of the sub-scanning frequency is the second mechanical resonance. Depends on the vibration frequency of the system.

  In general, the resonance frequency of a mechanical resonance system is not always constant, and may fluctuate due to various reasons such as its operating environment and deterioration over time. For this reason, in order to scan the luminous flux by always efficiently using the resonance phenomenon of the mechanical resonance system, tracking control of the vibration frequency of the mechanical resonance system is performed so as to follow the resonance frequency of the mechanical resonance system. It is effective.

  In the frequency tracking control, for example, the frequency of the drive signal supplied to the drive source of the mechanical resonance system is changed so as to match the resonance frequency of the mechanical resonance system.

  However, in order to realize different main scanning frequencies and sub-scanning frequencies, optical scanning configured to perform main scanning and sub-scanning using two types of mechanical resonance systems having different resonance frequencies, respectively. In the type display, when frequency tracking control is performed on these two types of mechanical resonance systems independently of each other, the ratio between the main scanning frequency and the sub-scanning frequency changes from the set ratio. This is because the resonance frequencies of these two types of mechanical resonance systems do not always change so as not to change the ratio between the main scanning frequency and the sub-scanning frequency from the set ratio.

  Therefore, in such an optical scanning display, it is desirable to perform frequency tracking control so that the ratio between the main scanning frequency and the sub-scanning frequency does not change from the set ratio.

  As described above, in an optical scanning display configured to perform main scanning and sub-scanning using two types of mechanical resonance systems having different resonance frequencies, the phase of main scanning (for example, The difference between the light beam deflection angle by the scanning mirror mentioned above and the phase of time fluctuation by main scanning) and the sub-scanning phase (for example, the phase of light flux deflection angle by the scanning mirror mentioned above and time fluctuation by sub-scanning) is set. Maintaining the value is important because the actual scanning trajectory is normal.

  In this type of optical scanning display, the phase of main scanning depends on the phase of vibration of the first mechanical resonance system, and similarly, the phase of sub-scanning becomes the phase of vibration of the second mechanical resonance system. Dependent.

  In this type of optical scanning display, when the frequency tracking control described above is performed for at least one of the two types of mechanical resonance systems, the vibration frequency of at least one of the mechanical resonance systems is forcibly changed. Accordingly, the phase of the vibration frequency of at least one of the mechanical resonance systems changes. This change causes a change in the difference between the main scanning phase and the sub-scanning phase.

  In this type of optical scanning display, as the difference between the main scanning phase and the sub-scanning phase deviates from the set value, the actual scanning locus deviates from the ideal scanning locus, and as a result, the reproducibility of the display image Decreases.

  Therefore, in this type of optical scanning display, it is desirable to perform frequency tracking control so that the difference between the main scanning phase and the sub-scanning phase does not change significantly from the set value.

  Against the background described above, the present invention provides a technique for displaying an image by two-dimensional scanning of a light beam, by reducing the scanning trajectory, reducing the required main scanning frequency, and increasing the required sub-scanning frequency. An object of the present invention is to enable at least one of an increase in the number of effective scanning lines per frame.

In order to solve the problem, according to the first aspect of the present invention, there is provided an optical scanning display for displaying an image by two-dimensional scanning of a light beam,
A light source unit that emits the luminous flux at a luminance according to a luminance signal;
A scanning device that reciprocally scans a light beam emitted from the light source unit in a main scanning direction and a sub-scanning direction that intersect each other, and (a) based on a main scanning drive signal, the light beam is converted into a first mechanical resonance. A main scanning unit capable of reciprocating scanning in the main scanning direction using a system, and (b) based on a sub-scanning drive signal, the light beam is transmitted using a second mechanical resonance system, A sub-scanning unit capable of reciprocating scanning in the sub-scanning direction, and performing reciprocating scanning more times in the sub-scanning direction in the main scanning direction for each frame of the image;
The luminance signal is generated on the basis of the video signal so that one frame of the image is divided into three or more fields and scanned and displayed by the scanning device, and is effective in the entire period of each round-trip scanning. The generated luminance signal is transmitted to the light source unit so that effective scanning lines formed by the light source unit actually emitting a light beam during a scanning period do not overlap each other in the three or more fields in the same frame. A luminance signal control unit to output to
A detection unit for detecting a scanning state of the scanning device;
A synchronization signal generator for generating a main scanning synchronization signal and a sub-scanning synchronization signal;
A drive signal generator for generating the main scanning drive signal and the sub-scanning drive signal based on the generated main scanning synchronization signal and sub-scanning synchronization signal, respectively
Including
The first mechanical resonance system and the second mechanical resonance system each have a Q value that is different from each other in size.
Of the main scanning unit and the sub-scanning unit, the higher Q value of the corresponding mechanical resonance system is a tracking control scanning unit that is controlled to follow the resonance frequency of itself,
Of the main scanning synchronization signal and the sub-scanning synchronization signal, the one corresponding to the scanning control unit for tracking control is a tracking control synchronization signal for performing the tracking control,
The synchronization signal generator is
First synchronization signal control for controlling the frequency of the tracking control synchronization signal to follow the resonance frequency of the tracking control scanning unit based on the scanning state of the tracking control scanning unit detected by the detection unit. And
Based on the controlled tracking control synchronization signal, a frequency of the main scanning synchronization signal and the sub-scanning synchronization signal that does not correspond to the tracking control synchronization signal is determined by a ratio of the main scanning frequency to the sub-scanning frequency. A second synchronization signal control unit that controls to match the set ratio;
An optical scanning display is provided.
In order to solve the above problems, according to a second aspect of the present invention, there is provided an optical scanning display for displaying an image by two-dimensional scanning of a light beam,
A light source unit that emits the luminous flux at a luminance according to a luminance signal;
A scanning device that reciprocally scans a light beam emitted from the light source unit in a main scanning direction and a sub-scanning direction that intersect each other, and (a) based on a main scanning drive signal, the light beam is converted into a first mechanical resonance. A main scanning unit capable of reciprocating scanning in the main scanning direction using a system, and (b) based on a sub-scanning drive signal, the light beam is transmitted using a second mechanical resonance system, A sub-scanning unit capable of reciprocating scanning in the sub-scanning direction, and performing reciprocating scanning more times in the sub-scanning direction in the main scanning direction for each frame of the image;
The luminance signal is generated on the basis of the video signal so that one frame of the image is divided into three or more fields and scanned and displayed by the scanning device, and is effective in the entire period of each round-trip scanning. The generated luminance signal is transmitted to the light source unit so that effective scanning lines formed by the light source unit actually emitting a light beam during a scanning period do not overlap each other in the three or more fields in the same frame. A luminance signal control unit to output to
A detection unit for detecting a scanning state of the scanning device;
A synchronization signal generator for generating a main scanning synchronization signal and a sub-scanning synchronization signal;
A drive signal generator for generating the main scanning drive signal and the sub-scanning drive signal based on the generated main scanning synchronization signal and sub-scanning synchronization signal, respectively
Including
The main scanning unit performs reciprocal deflection scanning of the light beam so as to be emitted at a main scanning deflection angle that periodically changes at a main scanning frequency,
The sub-scanning unit performs reciprocal deflection scanning of the light beam so as to be emitted at a sub-scanning deflection angle that periodically changes at a sub-scanning frequency,
The detection unit outputs a signal reflecting the main scanning deflection angle and a signal reflecting the sub scanning deflection angle as a main scanning displacement signal and a sub scanning displacement signal, respectively.
The first mechanical resonance system and the second mechanical resonance system each have a Q value that is different from each other in size.
Of the main scanning unit and the sub-scanning unit, the higher Q value of the corresponding mechanical resonance system is a tracking control scanning unit that is controlled to follow the resonance frequency of itself,
Of the main scanning synchronization signal and the sub-scanning synchronization signal, the one corresponding to the scanning control unit for tracking control is a tracking control synchronization signal for performing the tracking control,
The synchronization signal generator is
Based on the scanning state of the follow-up control scanning unit detected by the detection unit, the frequency of the follow-up control synchronization signal is discretely changed by a main scan frequency step size, so that the follow-up control scan unit A first synchronization signal control unit that controls to follow the resonance frequency;
Based on the controlled tracking control synchronization signal, the frequency of the main scanning synchronization signal and the sub-scanning synchronization signal that does not correspond to the tracking control synchronization signal is discretely changed by the sub-scanning frequency step size. A second synchronization signal control unit for controlling the ratio of the main scanning frequency and the sub-scanning frequency to coincide with the set ratio;
Including
The main scanning phase difference of the main scanning displacement signal with respect to the main scanning driving signal is caused by changing the frequency of the main scanning synchronizing signal and the frequency of the sub-scanning synchronizing signal by changing the frequency by the synchronizing signal generator. And a sub-scanning phase difference of the sub-scanning displacement signal with respect to the sub-scanning drive signal varies,
Due to the fluctuation of the main scanning phase difference and the fluctuation of the sub-scanning phase difference, the phase difference between scanning lines of a plurality of scanning lines formed by the scanning device fluctuates,
The main scanning frequency step width is set so as not to exceed the first allowable value so that the fluctuation amount of the inter-scan line phase difference caused by the fluctuation of the main scanning phase difference is within an allowable range,
The sub-scanning frequency step width is set so as not to exceed a second allowable value so that the amount of fluctuation of the inter-scan line phase difference caused by the fluctuation of the sub-scanning phase difference is within the allowable range. An optical scanning display is provided.
The following aspects are obtained by the present invention. Each aspect is divided into sections, each section is given a number, and is described in a form that cites other section numbers as necessary. This is to facilitate understanding of some of the technical features that the present invention can employ and combinations thereof, and the technical features that can be employed by the present invention and combinations thereof are limited to the following embodiments. Should not be interpreted. That is, it should be construed that it is not impeded to appropriately extract and employ the technical features described in the present specification as technical features of the present invention although they are not described in the following embodiments.

  Further, describing each section in the form of quoting the numbers of the other sections does not necessarily prevent the technical features described in each section from being separated from the technical features described in the other sections. It should not be construed as meaning, but it should be construed that the technical features described in each section can be appropriately made independent depending on the nature.

(1) An optical scanning display that displays an image by two-dimensional scanning of a light beam,
A light source unit that emits the luminous flux at a luminance according to a luminance signal;
A scanning device that reciprocally scans a light beam emitted from the light source unit in a main scanning direction and a sub-scanning direction that intersect each other, and (a) based on a main scanning drive signal, the light beam is converted into a first mechanical resonance. A main scanning unit capable of reciprocating scanning in the main scanning direction using a system, and (b) based on a sub-scanning drive signal, the light beam is transmitted using a second mechanical resonance system, A sub-scanning unit capable of reciprocating scanning in the sub-scanning direction, and performing reciprocating scanning more times in the sub-scanning direction in the main scanning direction for each frame of the image;
The luminance signal is generated on the basis of the video signal so that one frame of the image is divided into three or more fields and scanned and displayed by the scanning device, and is effective in the entire period of each round-trip scanning. The generated luminance signal is transmitted to the light source unit so that effective scanning lines formed by the light source unit actually emitting a light beam during a scanning period do not overlap each other in the three or more fields in the same frame. A luminance signal control unit to output to
A detection unit for detecting a scanning state of the scanning device;
A synchronization signal generator for generating a main scanning synchronization signal and a sub-scanning synchronization signal;
A drive signal generator for generating the main scan drive signal and the sub scan drive signal based on the generated main scan synchronization signal and sub scan synchronization signal, respectively,
The synchronization signal generator is
One of the main scanning unit and the sub-scanning unit is set as a tracking control target, and the main scanning synchronization signal and the sub-scanning synchronization signal corresponding to the tracking control target is set as a target synchronization signal. A first synchronization signal control unit that controls the synchronization signal to follow the resonance frequency of the tracking control target based on the scanning state detected by the detection unit;
An optical scanning display including: a second synchronization signal control unit that controls the other of the main scanning synchronization signal and the sub-scanning synchronization signal based on the controlled target synchronization signal.

  In this optical scanning display, one frame of an image is scanned and displayed in three or more fields, and further, effective scanning lines are formed so as not to overlap each other among the three or more fields in the same frame.

  Even in this way, an image is formed without overlapping effective scanning lines within one frame, and therefore, an image can be displayed in the same manner as in the conventional interlace method or non-interlace method described above.

  Therefore, according to this optical scanning display, the number of fields constituting one frame is increased as compared with the case where the above-described conventional interlace method or non-interlace method is adopted. This reduces the number of effective scanning lines required to display one screen.

  Therefore, according to this optical scanning display, it is easier to lower the required main scanning frequency than when the above-described conventional interlace method is adopted.

  When the main scanning frequency necessary for realizing the same number of scanning lines in one frame is low, the design and structure of the main scanning unit that performs main scanning in the scanning device is facilitated as compared with the case where the main scanning frequency is high.

  Therefore, if it is easy to lower the required main scanning frequency by the optical scanning display according to this section, for example, the design and manufacture of the scanning device and the performance improvement of the scanning device are facilitated.

  If one frame is composed of three or more fields and the necessary sub-scanning frequency is increased, the same main scanning frequency can be increased compared to the case where the necessary sub-scanning frequency cannot be increased because one frame is composed of two or less fields. The number of effective scanning lines formed in one frame under the scanning frequency and the sub scanning frequency increases. An increase in the number of effective scanning lines leads to an improvement in the resolution of the display image in the sub-scanning direction.

  Therefore, if it is easy to increase the number of effective scanning lines by the optical scanning display according to this section, for example, it becomes easy to improve the resolution of the display image.

  In the optical scanning display according to this item, the scanning device further reciprocally scans the light beam in the main scanning direction using the first mechanical resonance system based on (a) the main scanning drive signal. And (b) a sub-scanning unit capable of reciprocally scanning the light beam in the sub-scanning direction using the second mechanical resonance system based on the sub-scanning drive signal. Configured to include.

  In this optical scanning display, a main scanning driving signal and a sub scanning driving signal are generated based on a main scanning synchronizing signal and a sub scanning synchronizing signal, respectively. The main scanning unit and the sub scanning unit are driven based on the generated main scanning driving signal and sub scanning driving signal, respectively.

  In this optical scanning display, one of the main scanning unit and the sub-scanning unit is a tracking control target, and the main scanning synchronization signal and the sub-scanning synchronization signal correspond to the tracking control target. The target synchronization signal.

  In this optical scanning display, the frequency of the target synchronization signal is further controlled to follow the resonance frequency of the tracking control target based on the scanning state of the scanning device (including the scanning state of the main scanning unit). On the other hand, the other of the main scanning synchronization signal and the sub-scanning synchronization signal is controlled based on the target synchronization signal controlled for the tracking control target.

  As a result, according to this optical scanning display, one of the main scanning unit and the sub-scanning unit is set as a tracking control target and controlled so that the actual vibration frequency matches the actual resonance frequency. On the other hand, the other frequency of the main scanning unit and the sub-scanning unit is controlled so as to maintain a certain relationship with the frequency of the target synchronization signal to be tracked.

  Therefore, according to this optical scanning display, power consumption for scanning is reduced and the main scanning unit and the sub-scanning can be saved compared with the case where neither the main scanning unit nor the sub-scanning unit performs frequency tracking control. It is easier to always normalize the actual scanning trajectory by always maintaining the ratio of the main scanning frequency and the sub-scanning frequency at the set ratio than when performing frequency tracking control for both of the units.

(2) The first synchronization signal control unit controls the frequency of the target synchronization signal to follow the resonance frequency of the tracking control target based on the scanning state of the tracking control target detected by the detection unit. The optical scanning display according to item (1), further including a first frequency control unit.

  According to this optical scanning display, one of the main scanning unit and the sub-scanning unit is controlled such that the frequency of its own synchronization signal follows its actual resonance frequency based on its own scanning state. Is done.

(3) The second synchronization signal control unit includes a second frequency control unit that controls the frequency of the other synchronization signal so that the ratio of the main scanning frequency and the sub-scanning frequency matches the set ratio ( The optical scanning display according to item 1) or (2).

  Therefore, according to this optical scanning display, the ratio between the main scanning frequency and the sub scanning frequency is maintained at the set ratio in a situation where frequency tracking control is performed for one of the main scanning unit and the sub scanning unit. Thus, the actual scanning trajectory is normalized.

(4) The optical scanning display according to item (3), wherein the set ratio is an integer ratio which is relatively prime.

(5) The optical scanning according to any one of (1) to (4), wherein the tracking control target has a large Q value of a mechanical resonance system among the main scanning unit and the sub-scanning unit. Type display.

  According to this optical scanning display, when the resonance energy required for the main scanning unit and the sub-scanning unit are different from each other, it is possible to realize the different requests without excess or deficiency.

(6) The optical scanning display according to (5), wherein a Q value of the first mechanical resonance system is larger than a Q value of the second mechanical resonance system.

  According to this optical scanning display, for example, it is necessary to scan a rectangular region having a longer dimension in the vertical direction in the horizontal direction, with the main scanning being horizontal scanning and the sub-scanning being vertical scanning. When the resonance energy required for the part is larger than the resonance energy required for the sub-scanning part, these different requests can be realized without excess or deficiency.

(7) The main scanning unit performs reciprocal deflection scanning of the light beam so as to be emitted at a main scanning deflection angle that periodically changes at the main scanning frequency,
The detection unit outputs a signal reflecting the main scanning deflection angle as a main scanning displacement signal,
The synchronization signal generation unit includes a phase difference control unit that generates the main scanning synchronization signal so that a phase difference of the main scanning displacement signal with respect to the main scanning drive signal becomes a set value. An optical scanning display according to any one of the above.

  In general, when a light beam is scanned using a mechanical resonance system driven by a drive signal generated based on a synchronization signal, the actual vibration frequency of the mechanical resonance system deviates from the actual resonance frequency. The phase difference between the signal reflecting the temporal variation of the scanning deflection angle and the drive signal changes. Therefore, if the drive signal is generated by controlling the synchronization signal so that the phase difference matches the set value, the actual vibration frequency can be changed to follow the actual resonance frequency.

  Based on such knowledge, in the optical scanning display according to this section, the main scanning unit performs reciprocal deflection scanning so that the light beam is emitted at a main scanning deflection angle that periodically changes at the main scanning frequency. The detection unit outputs a signal reflecting the main scanning deflection angle as a main scanning displacement signal.

  Further, in this optical scanning display, the main scanning synchronization signal is generated so that the phase difference of the main scanning displacement signal with respect to the main scanning driving signal becomes a set value. As a result, the actual vibration frequency of the mechanical resonance system of the main scanning unit is changed so as to follow the actual resonance frequency.

(8) The synchronization signal generator may be configured to output at least one of the main scanning synchronization signal and the sub-scanning synchronization signal so that a phase difference between the main scanning synchronization signal and the sub-scanning synchronization signal matches a set value. The optical scanning display according to any one of (1) to (7), further including a phase changing unit that changes the phase of.

  According to this optical scanning display, the phase difference between the main scanning synchronization signal and the sub-scanning synchronization signal is normalized despite the above-described frequency tracking control. Therefore, according to this optical scanning display, the normalization of the ratio between the main scanning frequency and the sub-scanning frequency and the normalization of the phase difference between the temporal variation of the main scanning deflection angle and the temporal variation of the sub-scanning deflection angle are performed. It becomes easier to achieve together.

(9) An optical scanning display that displays an image by two-dimensional scanning of a light beam,
A light source unit that emits the luminous flux at a luminance according to a luminance signal;
A scanning device that reciprocally scans a light beam emitted from the light source unit in a main scanning direction and a sub-scanning direction that intersect each other, and (a) based on a main scanning drive signal, the light beam is converted into a first mechanical resonance. A main scanning unit capable of reciprocating scanning in the main scanning direction using a system, and (b) based on a sub-scanning drive signal, the light beam is transmitted using a second mechanical resonance system, A sub-scanning unit capable of reciprocating scanning in the sub-scanning direction, and performing reciprocating scanning more times in the sub-scanning direction in the main scanning direction for each frame of the image;
The luminance signal is generated on the basis of the video signal so that one frame of the image is divided into three or more fields and scanned and displayed by the scanning device, and is effective in the entire period of each round-trip scanning. The generated luminance signal is transmitted to the light source unit so that effective scanning lines formed by the light source unit actually emitting a light beam during a scanning period do not overlap each other in the three or more fields in the same frame. A luminance signal control unit to output to
A detection unit for detecting a scanning state of the scanning device;
A synchronization signal generator for generating a main scanning synchronization signal and a sub-scanning synchronization signal;
A drive signal generator for generating the main scan drive signal and the sub scan drive signal based on the generated main scan synchronization signal and sub scan synchronization signal, respectively,
The main scanning unit performs reciprocal deflection scanning of the light beam so as to be emitted at a main scanning deflection angle that periodically changes at a main scanning frequency,
The sub-scanning unit performs reciprocal deflection scanning of the light beam so as to be emitted at a sub-scanning deflection angle that periodically changes at a sub-scanning frequency,
The detection unit outputs a signal reflecting the main scanning deflection angle and a signal reflecting the sub scanning deflection angle as a main scanning displacement signal and a sub scanning displacement signal, respectively.
The synchronization signal generator is
At least one of the main scanning synchronization signal and the sub scanning synchronization signal follows a resonance frequency of a corresponding one of the main scanning portion and the sub scanning portion; and the main scanning frequency and the sub scanning frequency The frequency of the main scanning synchronization signal and the frequency of the sub-scanning synchronization signal are respectively set based on the scanning state detected by the detection unit so that the ratio between A frequency changing unit that discretely changes the main scanning frequency step size and the sub scanning frequency step size;
Due to the frequency changing unit changing the frequency of the main scanning synchronization signal and the frequency of the sub scanning synchronization signal, the main scanning phase difference of the main scanning displacement signal with respect to the main scanning drive signal, and the sub scanning synchronization signal The sub-scanning phase difference of the scanning displacement signal with respect to the sub-scanning drive signal varies,
Due to the fluctuation of the main scanning phase difference and the fluctuation of the sub-scanning phase difference, the phase difference between scanning lines of a plurality of scanning lines formed by the scanning device fluctuates,
The main scanning frequency step width is set so as not to exceed the first allowable value so that the fluctuation amount of the inter-scan line phase difference caused by the fluctuation of the main scanning phase difference is within an allowable range,
The sub-scanning frequency step width is set so as not to exceed a second allowable value so that the amount of fluctuation of the inter-scan line phase difference caused by the fluctuation of the sub-scanning phase difference is within the allowable range. Optical scanning display.

  In this optical scanning display, as in the optical scanning display according to item (1), one frame of an image is scanned and displayed in three or more fields, and the effective scanning lines are the same in the same frame. The three or more fields are formed so as not to overlap each other.

  Therefore, according to this optical scanning display, for the same reason as the optical scanning display according to the item (1), the field constituting one frame is more than the case where the conventional interlace method or non-interlace method is adopted. As a result, the number of effective scanning lines required to display one screen, which is the minimum unit of image display, decreases.

  In this optical scanning display, similarly to the optical scanning display according to the item (1), the scanning device uses (a) a light beam based on a main scanning drive signal, and a first mechanical resonance system. A main scanning section capable of reciprocating scanning in the main scanning direction, and (b) reciprocating scanning of the light beam in the sub scanning direction using the second mechanical resonance system based on the sub scanning drive signal. And a sub-scanning unit capable of doing so.

  In this optical scanning display, the main scanning unit performs reciprocal deflection scanning of the light beam so that the main scanning unit emits light at a main scanning deflection angle that periodically changes at the main scanning frequency, and the sub scanning unit periodically performs at the sub scanning frequency. The light beam is reciprocally deflected and scanned so as to be emitted at a changing sub-scanning deflection angle, and the detection unit outputs a signal that reflects the main-scanning deflection angle and a signal that reflects the sub-scanning deflection angle, respectively. Output as a signal.

  In this optical scanning display, a main scanning driving signal and a sub scanning driving signal are generated based on a main scanning synchronizing signal and a sub scanning synchronizing signal, respectively. The main scanning unit and the sub scanning unit are driven based on the generated main scanning driving signal and sub scanning driving signal, respectively.

  In this optical scanning display, at least one of the main scanning synchronization signal and the sub scanning synchronization signal follows the resonance frequency of the corresponding one of the main scanning portion and the sub scanning portion, and the main scanning frequency Based on the scanning state of the scanning device, the frequency of the main scanning synchronization signal and the frequency of the sub-scanning synchronization signal are respectively set so that the ratio between the sub-scanning frequency and the sub-scanning frequency coincides with the set ratio. The scanning frequency step size and the sub scanning frequency step size are discretely changed.

  In this optical scanning display, when the frequency of the main scanning synchronization signal and the frequency of the sub scanning synchronization signal are discretely changed as described above (for example, the frequency and the resonance frequency are the maximum increments). The main scanning phase difference of the main scanning displacement signal with respect to the main scanning driving signal and the sub scanning phase difference of the sub scanning displacement signal with respect to the sub scanning driving signal vary. Further, due to the fluctuation of the main scanning phase difference and the fluctuation of the sub-scanning phase difference, the phase difference between the scanning lines of a plurality of scanning lines formed by the scanning device varies.

  In this optical scanning display, the main scanning frequency step size does not exceed the first allowable value so that the fluctuation amount of the inter-scan line phase difference caused by the fluctuation of the main scanning phase difference is within the allowable range. Set to Similarly, the sub-scanning frequency step width is set so as not to exceed the second allowable value so that the fluctuation amount of the inter-scan line phase difference caused by the fluctuation of the sub-scanning phase difference is within the allowable range. .

  Therefore, according to this optical scanning type display, the main scanning frequency step width and the sub scanning frequency step width are optimized, so the frequency of the main scanning synchronization signal (main scanning frequency) and the frequency of the sub scanning synchronization signal (sub scanning). Frequency) is changed discretely, the amount of fluctuation of the inter-scanning phase difference caused by the fluctuation of the main scanning phase difference is also the amount of the phase difference between the scanning lines caused by the fluctuation of the sub-scanning phase difference. The variation amount is also set to be within an allowable range.

  Therefore, according to this optical scanning display, although the frequency of the main scanning synchronization signal and the frequency of the sub-scanning synchronization signal are discretely changed, the amount of fluctuation in the phase difference between the scanning lines is suppressed, As a result, the actual scanning trajectory is made regular.

(10) The main scanning frequency is f _M , the sub-scanning frequency is f _S , the setting ratio is n _M : n _S (n _M and n _S are relatively prime integers), and the first mechanical resonance system When the Q value is expressed as Q _M , the Q value of the second mechanical resonance system is expressed as Q _S , and a coefficient larger than 1 is expressed as γ, the first allowable value is
πf _M / (4γ · Q _M · n _S )
Defined as
The second tolerance value is
πf _S / (4γ · Q _S · n _M )
(9) The optical scanning display according to item (9).

According to this optical scanning display, the main scanning frequency step size is appropriately set in relation to the main scanning frequency f _M , the setting ratio n _M : n _S, and the Q value Q _{M of} the first mechanical resonance system. The

Further, according to this optical scanning display, the sub-scanning frequency step size is appropriately set in relation to the sub-scanning frequency f _S , the setting ratio n _M : n _S and the Q value Q _{S of} the second mechanical resonance system. Is set.

(11) The optical scanning display according to (10), wherein the coefficient γ has a value of 2 or more and 6 or less.

  According to this optical scanning display, the variation in phase difference between scanning lines caused by discrete changes in the frequency of the main scanning synchronization signal and the frequency of the sub-scanning synchronization signal is greater than when the coefficient γ is less than 2 and greater than 6. The amount is more preferably suppressed.

  For example, when the coefficient γ is smaller than 2, the variation amount of the inter-scan line phase difference tends to be larger than the allowable value. In addition, the larger the coefficient γ, the smaller the amount of fluctuation of the phase difference between the scanning lines, but even if it is larger than 6, the image quality is not improved to the extent that it can be visually recognized. Will be required.

(12) The synchronization signal generator
One of the main scanning unit and the sub-scanning unit is set as a tracking control target, and the main scanning synchronization signal and the sub-scanning synchronization signal corresponding to the tracking control target is set as a target synchronization signal. A first synchronization signal control unit that controls the synchronization signal to follow the resonance frequency of the tracking control target based on the scanning state detected by the detection unit;
Any one of (9) to (11), including a second synchronization signal control unit that controls the other of the main scanning synchronization signal and the sub-scanning synchronization signal based on the controlled target synchronization signal. An optical scanning display according to 1.

  According to this optical scanning display, as in the optical scanning display according to the above item (1), the frequency scanning control is performed for both the main scanning unit and the sub-scanning unit without performing frequency tracking control. The power consumption is reduced, and the ratio between the main scanning frequency and the sub-scanning frequency is always maintained at the set ratio, compared with the case where frequency tracking control is performed for both the main scanning unit and the sub-scanning unit. It is easy to always normalize the trajectory.

(13) The synchronization signal generator may be configured to output at least one of the main scanning synchronization signal and the sub-scanning synchronization signal so that a phase difference between the main scanning synchronization signal and the sub-scanning synchronization signal matches a set value. The optical scanning display according to any one of (9) to (12), further including a phase changing unit that changes the phase of.

  According to this optical scanning display, the phase difference between the main scanning synchronization signal and the sub-scanning synchronization signal is normalized despite the above-described frequency tracking control. Therefore, according to this optical scanning display, the normalization of the ratio between the main scanning frequency and the sub-scanning frequency and the normalization of the phase difference between the temporal variation of the main scanning deflection angle and the temporal variation of the sub-scanning deflection angle are performed. It becomes easier to achieve together.

  Hereinafter, one of more specific embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows a retinal scanning display (hereinafter abbreviated as “RSD”) 10 according to an embodiment of the present invention.

  The RSD 10 projects a laser beam, which is an example of a light beam representing an image, directly onto the retina 16 via the pupil 14 of the observer's eye 12, and scans the projected light beam on the retina 16. Is displayed.

  In the RSD 10, a spot of a laser beam is formed on the retina 16, and the spot is scanned on the retina 16 two-dimensionally, so that an image is perceived as a virtual image by an observer.

  As shown in FIG. 1, the RSD 10 includes an image light generation unit 18 and an optical scanning unit 20.

  As will be described in detail later, the video light generation unit 18 generates a luminance signal for each of the three primary colors based on a video signal supplied from the outside, and is intensity-modulated based on the generated luminance signal. It has a function of generating a laser beam for each color and a function of generating a synchronization signal and supplying it to the optical scanning unit 20.

  Therefore, the video light generation unit 18 includes an R laser 22, a G laser 24, and a B laser 26 that emit red light, green light, and blue light, respectively. The luminance (intensity) of the three colors of laser beams (an example of a light beam) emitted from the R laser 22, G laser 24, and B laser 26 is determined by the R laser driving circuit 28, the G laser driving circuit 30, and the B laser driving circuit 32. Each is modulated.

  In the present embodiment, the R laser 22, G laser 24 and B laser 26 and the corresponding R laser drive circuit 28, G laser drive circuit 30 and B laser drive circuit 32 cooperate with each other to form the light source unit 34. It is composed.

  As shown in FIG. 1, the R laser 22, G laser 24 and B laser 26 are provided with three collimator lenses 40, 42 and 44 and three dichroic mirrors 50, 52 and 54. .

  The laser beams emitted from the lasers 22, 24, and 26 are collimated by the corresponding ones of the collimator lenses 40, 42, and 44, and then enter the corresponding ones of the dichroic mirrors 50, 52, and 54. These three dichroic mirrors 50, 52, and 54 have wavelength selectivity, and synthesize three laser beams emitted from the R laser 22, G laser 24, and B laser 26 into one laser beam. Is provided.

  One dichroic mirror representing the three dichroic mirrors 50, 52, and 54, that is, in the present embodiment, a synthesized laser beam is emitted from the dichroic mirror 50, and the emitted synthesized laser beam is emitted from the coupling optical system. 56 is collected.

  In the present embodiment, the collimator lenses 40, 42, 44, the dichroic mirrors 50, 52, 54, and the coupling optical system 56 together constitute an optical multiplexing unit 58.

  As shown in FIG. 1, the combined laser beam condensed by the coupling optical system 56 passes through an optical fiber 60 as an optical transmission medium and a collimator lens 62 arranged at the output end of the optical fiber 60 in that order. Then, the light enters the optical scanning unit 20.

  As will be described in detail later, the optical scanning unit 20 has a function of two-dimensionally scanning the laser beam emitted from the image light generation unit 18 based on various synchronization signals, and the laser beam is input to the pupil 14 to retina. 16 to form an image.

  Therefore, the optical scanning unit 20 includes a horizontal scanning unit 70 that performs horizontal scanning on the laser beam emitted from the collimator lens 62, and a vertical scanning unit that performs vertical scanning on the laser beam emitted from the horizontal scanning unit 70. 72.

  The optical scanning unit 20 further converges the laser beam emitted from the horizontal scanning unit 70 and transmits it to the vertical scanning unit 72, and converges the laser beam emitted from the vertical scanning unit 72 to cause the eye 12 to converge. And a relay optical system 76 for transmitting to the network.

  As shown in FIG. 1, the horizontal scanning unit 70 includes a horizontal scanning mirror 80 as a vibrating body. The horizontal scanning unit 70 performs horizontal scanning using the torsional resonance of the horizontal scanning mirror 80. The horizontal scanning mirror 80 is formed by an elastic plate-like or film-like member such as silicon.

  FIG. 2 is an enlarged plan view of the configuration of the horizontal scanning unit 70. In the horizontal scanning unit 70, a plate-like horizontal scanning mirror 80 is supported by a pair of beam portions 82 and 82 at both ends in the direction of the swing axis. The pair of beam portions 82, 82 extend along the swing axis in such a manner as to face each other across the horizontal scanning mirror 80. Each of the pair of beam portions 82 and 82 is fixed to the fixed frame 83 at the end opposite to the horizontal scanning mirror 80.

  Each of the beam portions 82, 82 includes one first leaf spring portion 84 extending from the horizontal scanning mirror 80, and two second leaf spring portions 86 extending from the first leaf spring portion 84 and extending in parallel to each other. 86. The first plate spring portion 84 and the second plate spring portions 86 and 86 both have a thickness direction that is common to the thickness direction of the horizontal scanning mirror 80.

  The two second leaf spring portions 86, 86 are opposed to each other across the swing axis. Therefore, if the second plate springs 86 and 86 are bent in opposite directions, the first plate spring 84 is twisted around the swing axis, and the horizontal scanning mirror 80 rotates around the swing axis. Be made. Furthermore, if bending is alternately applied to the same second leaf spring portion 86 in opposite directions, the horizontal scanning mirror 80 is swung around the swing axis.

  In order to apply such bending to each second leaf spring portion 86, 86, a drive source 88 is installed in each second leaf spring portion 86, 86. The drive source 88 can be configured using, for example, an element that converts an applied electric field into a displacement in a direction crossing the application direction.

  An example of such an element is a plate-like piezoelectric element. For example, if the piezoelectric element is vibrated in the length direction in a state where the piezoelectric element is attached to one of both surfaces of the second leaf spring portions 86 and 86 facing each other in the thickness direction, Bending vibration is generated in the second leaf spring portions 86 and 86.

  Similarly, as shown in FIG. 1, the vertical scanning unit 72 includes a vertical scanning mirror 90 as a vibrating body and a drive source 92 (see FIG. 3) that drives the vertical scanning mirror 90 to vibrate the vertical scanning mirror 90. I have. Similar to the horizontal scanning unit 70, the vertical scanning unit 72 performs vertical scanning using the torsional resonance of the vertical scanning mirror 90.

  The vertical scanning mirror 90 is formed of a plate-like or film-like member having elasticity, such as silicon. The drive source 92 can be configured using, for example, an element that converts an applied electric field into a displacement in a direction that intersects the application direction. An example of such an element is a plate-like piezoelectric element. is there.

  Since the configuration of the vertical scanning unit 72 is the same as that of the horizontal scanning unit 70 shown in FIG.

  As shown in FIG. 1, the horizontal scanning unit 70 further includes a horizontal scanning drive circuit 100 for driving a drive source 88 installed on the horizontal scanning mirror 80. The horizontal scanning drive circuit 100 is configured to include an oscillation circuit for generating a drive signal supplied to the drive source 88, for example.

The horizontal scanning unit 70 further includes a horizontal scanning detection circuit 102 that detects the operation of the horizontal scanning mirror 80. The horizontal scanning detection circuit 102 outputs a signal reflecting the deflection angle theta _H of the horizontal scanning mirror 80 as a displacement signal.

  The horizontal scanning detection circuit 102 is configured to optically detect the angular displacement of the horizontal scanning mirror 80, for example. An example of this type of horizontal scanning detection circuit 102 is a beam detector that receives a laser beam incident on the horizontal scanning mirror 80 and reflected from the horizontal scanning mirror 80, and the time when the laser beam is detected by the beam detector. And a measuring unit for measuring the length of time until the time detected by the beam detector, and detecting the angular displacement of the horizontal scanning mirror 80 based on the measured length of time.

  An example of a technique for optically detecting the swing angle of a scanning mirror that is reciprocally swung is described in Japanese Patent Application No. 2004-286286, and the description regarding the example is incorporated herein by reference.

  As shown in FIG. 1, the vertical scanning unit 72 further includes a vertical scanning drive circuit 110 for driving a drive source 92 installed on the vertical scanning mirror 90. The vertical scanning drive circuit 110 is configured to include, for example, an oscillation circuit for generating a drive signal supplied to the drive source 92.

The vertical scanning unit 72 further includes a vertical scanning detection circuit 112 that detects the operation of the vertical scanning mirror 90. The vertical scanning detection circuit 112 outputs a signal reflecting the deflection angle theta _V of the vertical scanning mirror 90 as a displacement signal. The vertical scanning detection circuit 112 is configured to optically detect the angular displacement of the vertical scanning mirror 90, for example, similarly to the horizontal scanning detection circuit 102.

  As shown in FIG. 1, the optical scanning unit 20 further includes a vertical scanning drive circuit 110 for driving a drive source 92 installed on the vertical scanning mirror 90. The vertical scanning drive circuit 110 is configured to include, for example, an oscillation circuit for generating a drive signal supplied to the drive source 92.

  The horizontal scanning frequency of the horizontal scanning unit 70 is determined by the resonance frequency of the horizontal scanning mirror 80, and similarly, the vertical scanning frequency of the vertical scanning unit 72 is determined by the resonance frequency of the vertical scanning mirror 90. In the present embodiment, the resonance frequencies of the horizontal scanning mirror 80 and the vertical scanning mirror 90 are set so that the horizontal scanning frequency is higher than the vertical scanning frequency.

  As shown in FIG. 1, the video light generation unit 18 further includes a signal processing circuit 120. The signal processing circuit 120 includes a computer 122 as shown in FIG. The computer 122 is configured by connecting a CPU 124, a ROM 126, and a RAM 128 to each other via a bus 130. A video signal is supplied to the computer 122 from the outside.

  The ROM 126 stores various programs such as an image display program conceptually shown in the flowchart of FIG. 4 and a scanning control program conceptually shown in the flowchart of FIG. The image display program and the scan control program are executed by the CPU 124 based on the video signal supplied from the outside and using the RAM 128, whereby an image is displayed on the retina 14 of the observer's eye 10. .

  In the signal processing circuit 120, based on a video signal supplied from the outside, a plurality of pixel data (luminance data) representing the brightness of each of a plurality of pixels constituting an image to be displayed is generated, and the generated pixels Based on the data, data processing is performed using the RAM 128, and the R luminance signal for red light, the G luminance signal for green light, and the B luminance signal for blue light are generated.

  As shown in FIG. 1, a video data storage unit 134 is connected to the signal processing circuit 120. The signal processing circuit 120 stores the generated collection of a plurality of luminance data as video data in the video data storage unit 134. The signal processing circuit 120 reads out necessary luminance data from the video data storage unit 134 in order to generate a luminance signal from the luminance data for each color.

  As shown in FIG. 3, an R laser 22, a G laser 24, and a B laser 26 are connected to the signal processing circuit 120 through an R laser driving circuit 28, a G laser driving circuit 30, and a B laser driving circuit 32. The signal processing circuit 120 outputs an R luminance signal to the R laser driving circuit 28, outputs a G luminance signal to the G laser driving circuit 30, and outputs a B luminance signal to the B laser driving circuit 32.

  As shown in FIG. 3, in this signal processing circuit 120, a frame buffer 140 is connected to a computer 122. The frame buffer 140 stores image data necessary for reproducing one frame of an image by scanning with a laser beam and a set of a plurality of pixel data (data representing luminance signals) in association with the scanning line number SL. The frame buffer 140 is provided for each color of the laser beam. FIG. 5 conceptually shows how image data is stored in the frame buffer 140, which will be described in detail later with reference to FIG.

  As shown in FIG. 3, the signal processing circuit 120 is further connected to a horizontal scanning driving circuit 100 and a vertical scanning driving circuit 110 of the optical scanning unit 20. A horizontal scanning drive signal is supplied from the horizontal scanning driving circuit 100 to the driving source 88, and a vertical scanning driving signal is supplied from the vertical scanning driving circuit 110 to the driving source 110. As a result, the horizontal scanning unit 70 and the vertical scanning unit 72 Horizontal scanning and vertical scanning are performed.

  In FIG. 6, the horizontal scanning drive signal is represented by the upper graph, and the vertical scanning drive signal is represented by the lower graph. As is apparent from these graphs, in the present embodiment, the horizontal scanning drive signal has a higher frequency than the vertical scanning drive signal. The frequency of the vertical scanning drive signal is set to several hundred Hz, for example.

  Here, the synchronization between the operation timing (intensity modulation) of the light source unit 34 and the operation timing (horizontal scanning and vertical scanning) of the optical scanning unit 20 will be described in detail with reference to FIGS.

  FIG. 7 conceptually shows the light source unit 34 and the optical scanning unit 20 together with the signal processing circuit 120 in a block diagram. The signal processing circuit 120 includes a luminance signal generation unit 150 that generates a luminance signal based on the video signal and outputs the luminance signal to the light source unit 34.

  The signal processing circuit 120 further includes a scanning control unit 152. The scanning control unit 152 generates a frame synchronization signal, a horizontal scanning synchronization signal, a vertical synchronization signal, and a dot clock signal, as will be described in detail later with reference to FIG. The scanning control unit 152 supplies the generated frame synchronization signal (including the field synchronization signal), the horizontal synchronization signal, and the dot clock signal to the luminance signal generation unit 150.

  The luminance signal generation unit 150 outputs the luminance signal of each color to the light source unit 34 in response to the timing at which the frame synchronization signal, the horizontal scanning signal, and the dot clock signal are supplied from the scanning control unit 152.

  As will be described in detail later with reference to FIG. 19, the scanning control unit 152 supplies the generated horizontal scanning synchronizing signal to the horizontal scanning driving circuit 100 and drives the vertical scanning synchronizing signal to vertical scanning as shown in FIG. Supply to circuit 110.

  As shown in FIG. 7, the horizontal scanning detection circuit 102 supplies a displacement signal reflecting the operation of the horizontal scanning mirror 80 to the scanning control unit 152. Similarly, the vertical scanning detection circuit 112 supplies a displacement signal reflecting the operation of the vertical scanning mirror 90 to the scanning control unit 152.

  In FIG. 8, the frame synchronization signal, the vertical scanning synchronization signal, and the horizontal scanning synchronization signal are respectively represented by timing charts.

A horizontal scanning synchronization signal is generated for each scanning line. Here, the term “scan line” refers to an effective scan line that exists (in the visible region) and an invalid scan line that does not exist (in the invisible region) (a scan line that is erased because it is outside the image display region). , And an erasing blanking that is erased because it is in the image display area but is a blanking.). The horizontal scanning synchronization signals are sequentially generated in n _H per frame of the image. n _H is equal to the number of reciprocations per frame of horizontal scanning.

  The scanning control unit 152 generates a frame synchronization signal at the time when the initial phase difference time Δt has elapsed from the generation time of a horizontal scanning synchronization signal. This frame synchronization signal is generated for each frame of the image in synchronization with the start time.

The scanning control unit 152 further outputs n _V vertical scanning synchronization signals at the time when the initial phase difference time Δt has elapsed from the generation time of the horizontal scanning synchronization signal, that is, at the same time as the generation time of the frame synchronization signal. The first vertical scanning synchronization signal at is generated. n _V is equal to the number of round trips per frame vertical scanning.

  The scanning control unit 152 outputs the generated frame synchronization signal and horizontal scanning synchronization signal to the luminance signal generation unit 150.

  In the present embodiment, the luminance signal generation unit 150 is configured by a portion of the computer 122 that executes an image display program that will be described in detail later, and the scan control unit 152 performs central control as shown in FIG. Part, that is, a part of the computer 122 that executes a scanning control program, which will be described in detail later, and an electronic circuit.

  Next, the above-described image display program will be described in more detail with reference to FIG. 4. First, the image display principle employed in the image display program will be described.

  FIG. 9 is a front view (a diagram showing the trajectory of the scanning line on the screen) showing that one frame of an image is displayed according to the conventional interlace scanning method. In FIG. 9, a plurality of horizontal solid lines indicate a plurality of effective scanning lines forming odd fields, whereas a plurality of horizontal broken lines indicate a plurality of erasures forming even fields. Shows a return. The erase blanking is not shown.

  According to this conventional interlace scan method, one frame is formed by being divided into two fields. For this reason, when the comparison is made on the assumption that the conditions for the horizontal scanning frequency and the conditions for the vertical scanning frequency are the same, the number of effective scanning lines constituting one frame increases compared to the case where the non-interlace scanning method is adopted.

  This means that the horizontal scanning frequency is apparently decreased and the vertical scanning frequency is apparently increased when compared on the assumption that the conditions regarding the number of effective scanning lines are the same. Therefore, although the field itself forms one screen and the frame frequency is lowered, the field frequency (vertical synchronization frequency) is not lowered, so that the flicker does not stand out.

  The present inventor has proposed an image display method that apparently further increases the vertical scanning frequency by dividing and forming one frame into three or more fields. FIG. 10 is a front view showing an image displayed according to the proposed image display method.

  In FIG. 10A, in each field, the visible scanning point of the light beam moves in one direction in the vertical scanning direction while reciprocating in the horizontal scanning direction on the scanning surface of the light beam. (Hereinafter referred to as “forward scanning lines”) and scanning lines from the right side to the left side (hereinafter referred to as “return scanning lines”) are both formed alternately as effective scanning lines.

  As shown in FIG. 9, when the conventional interlace scanning method is adopted, one frame is divided into two fields, and two effective scanning lines adjacent to each other in one field are one effective in the other field. Interpolated by scan lines.

  On the other hand, when one frame is constituted by three or more fields according to the proposal of the present inventor, two effective scanning lines adjacent to each other in each field are two or more in the remaining two or more fields. Interpolated by valid scan lines. This means that the gap between two effective scanning lines adjacent to each other in each field becomes wider than when the conventional interlace scanning method is adopted, and the sharpness (resolution) of the image is reduced.

  In order to reduce such inconvenience, as shown in FIG. 10A, in each field, not only the forward scanning line but also the return scanning line can be used as an effective scanning line for image display.

  FIG. 10B shows an example of one frame that uses three or more fields shown in FIG. In this example, the same number of effective scanning lines corresponding to each other among three or more fields are shifted in parallel to each other in the vertical scanning direction. Therefore, when this example is adopted, the resolution is reduced within one frame even though the forward scanning line and the return scanning line tend to be non-parallel to each other than when the conventional interlace scanning method is adopted. The occurrence of unevenness is suppressed.

  Furthermore, in the example shown in FIG. 10B, in any field, the visible scanning point of the light beam reciprocates in the horizontal scanning direction on the scanning surface of the light beam while moving in the forward direction in the vertical scanning direction, that is, from the upper side. Move in one direction toward the bottom. That is, in this example, both the forward and backward scan points for horizontal scanning are used for image display, whereas only the forward scan point for vertical scanning is used for image display.

  FIG. 10 (c) shows another example of one frame formed by using three or more fields shown in FIG. 10 (a). In this example, in the odd field, the visible scanning point reciprocates in the horizontal scanning direction on the scanning surface while moving in the forward direction in the vertical scanning direction, that is, in one direction from the upper side to the lower side. In the even field, the visible scanning point reciprocates in the horizontal scanning direction on the scanning surface while moving in the reverse direction in the vertical scanning direction, that is, in one direction from the lower side to the upper side. That is, in this example, both the forward and backward scanning points for horizontal scanning are used for image display, and the forward and backward scanning points for vertical scanning are also used for image display.

  Therefore, when it is desired to apparently increase the vertical scanning frequency, it is more preferable to adopt the example shown in FIG. 10C than to adopt the example shown in FIG.

  However, when the example shown in FIG. 10C is adopted, similarly to the case where the example shown in FIG. 10B is adopted, the return scanning in a certain field in the region surrounded by a circle in the figure. The line overlaps the forward scan line in another field. On the other hand, in the region where the effective scanning lines overlap within one frame, the luminance of the image increases compared to the region where the effective scanning lines do not overlap. Therefore, even if any of these examples is adopted, luminance unevenness may occur due to overlapping of effective scanning lines.

  FIG. 11A shows an example in which the scanning is performed so that the forward scanning line emits light as an effective scanning line while the return scanning line, that is, the return line is erased, in order to eliminate such luminance unevenness. It is shown. In this example, an area parallel to the forward scanning line in one frame is an image display area (area indicated by a rectangular frame in the figure) 158, and the forward scanning line is outside the image display area 158. Even erased.

  However, when the example shown in FIG. 11A is adopted, the image display area 158 is inclined with respect to the horizontal line, and the observer may feel uncomfortable.

  FIG. 11B shows an example shown in FIG. 11A without taking any special measures for the optical system (for example, the horizontal scanning unit 70 and the vertical scanning unit 72) involved in image display in the RSD 10. An example is shown in which the inclination of the optical system is adjusted in advance so that the final image display area 158 extends horizontally in anticipation of the angle at which the image display area 158 is inclined with respect to the horizontal line when adopted. Yes. That is, this example is realized by the joint action of the above-described special signal processing relating to the scanning of the light beam and the tilt adjustment of the optical system. The RSD 10 is designed so that an observer can observe an image in the image display area 158 shown in FIG. 11B with a feeling comparable to that of a conventional RSD.

  Next, the trajectory of the scanning points formed by the horizontal scanning unit 70 and the vertical scanning unit 72 will be described with reference to FIGS.

  In the present embodiment, since the scanning point is generally oscillated in both the horizontal scanning direction and the vertical scanning direction, the raster which is the locus drawn by the scanning point is strictly a Lissajous figure having a sine wave shape. It is.

Accordingly, the vertical scanning angle θ _V is expressed by the equation (1) in FIG. 12, and the vertical scanning angle amplitude (maximum deflection angle) Θ _V is the amplitude, and the number of reciprocations n per frame of the vertical scanning is n. It is expressed by a trigonometric function whose angular velocity is a value obtained by multiplying the product of _V and the frame frequency f ₀ by 2π.

The horizontal scanning angle θ _H is represented by the equation (2) in FIG. 12, and the horizontal scanning angle amplitude (maximum deflection angle) Θ _H is the amplitude, and the number of reciprocations n _H per frame of horizontal scanning is A value obtained by multiplying the product of the frame frequency f ₀ by 2π is an angular velocity, and is expressed by a trigonometric function having an initial phase difference time Δt as an initial phase.

On the other hand, in order to uniformly distribute a plurality of effective scanning lines in each frame (so that a plurality of effective scanning lines do not overlap each other between a plurality of fields in the same frame), the equation (3) in FIG. as represented by a prime and values of the number of round trips n _V roundtrips n _H is, and it is desirable that the initial phase difference time Δt is such a specific value.

The specific value is obtained by dividing an arbitrary odd quarter by the product of the number of round trips n _H , the number of round trips n _V and the frame frequency f ₀ , as represented by equations (3) and (b) in FIG. Value. In the formulas (3) and (b), “n” is an arbitrary integer.

Figure 13 is equal to reciprocating frequency n _V is 3, and the case number of reciprocations n _H is equal to 7 as an example, the equation (3) and the horizontal scanning unit 70 when satisfy the conditions represented by the vertical scanning The raster formed by the section 72 is actually expressed by a plurality of sinusoidal curves, but is approximately expressed by a plurality of straight lines with arcsine correction.

  Here, the principle of displaying an image by the RSD 10 will be described in more detail with reference to FIGS.

  14 to 16 are front views showing a state in which a plurality of scanning lines are formed by the RSD 10 in terms of time. In each figure, a solid line indicates an effective scanning line, and a broken line indicates an erasing return line (ineffective scanning line). In the example shown in FIGS. 14 to 16, one frame of an image is scanned in 8 fields. FIG. 14 shows the first field, FIG. 15 shows the first and second fields together, and FIG. 16 shows the first to eighth fields, that is, all the fields constituting the current frame. Shown together.

  In FIG. 17, the image display area 158 set for one frame shown in FIG. 16 indicates the inclination of the optical system (for example, the horizontal scanning unit 70 and the vertical scanning unit 72) involved in image display in the RSD 10. When designed so as to be compatible with the conventional interlace scan method or the conventional non-interlace scan method, the front view shows an inclination with respect to the horizontal line.

  FIG. 18 shows the image display area 158 shown in FIG. 17 in a posture that extends horizontally by adjusting the inclination of an optical system (for example, the horizontal scanning unit 70 and the vertical scanning unit 72) that is involved in image display in the RSD 10. Has been. Furthermore, in FIG. 18, only a portion existing in the image display area 158 is visualized from among a plurality of scanning lines (scanning lines that can be visualized as effective scanning lines) in one frame shown in FIG. A state in which a portion existing outside the display area 158 is erased is shown. The RSD 10 is designed so that an observer can observe an image in an image display area 158 shown in FIG.

  The image display principle employed in the above-described image display program has been described above. Next, the image display program will be described with reference to FIG.

  When the execution of the image display program is started by the computer 122, first, in step S1 (hereinafter, simply represented by “S1”, the same applies to other steps), the horizontal scanning unit 70 and the vertical scanning unit 72 are used. The horizontal scanning and the vertical scanning are executed in synchronization with each other. As a result, on the condition that the laser beam is emitted from at least one of the R laser 22, the G laser 24, and the B laser 26, the locus of the scanning point (reproduction point) of the laser beam on the retina 14 is desired. The image can be drawn as a Lissajous figure.

  Next, in S2, the current value of the frame number FRM attached to each of a series of frames constituting the video to be displayed is set to 1. Subsequently, in S3, the scanning control unit 152 waits for the latest frame synchronization signal to be generated.

  If the latest frame synchronization signal has been generated, the determination in S3 is YES, and in S4, based on the video signal supplied from the outside, image data for displaying the current frame (each pixel in the image) Data corresponding to the luminance signal) is generated.

The generated image data for one frame is stored in the frame buffer 140 in association with the scanning line number SL as line data divided for each effective scanning line. Image data for one frame is configured as a set of a plurality of line data respectively corresponding to a plurality of effective scanning lines. When one frame is constituted by n _H effective scanning lines, the frame buffer 140 stores image data for n _H rows. Each line data is a set of a plurality of pixel data each representing the luminance of a plurality of pixels located on the corresponding effective scanning line.

  In the example shown in FIG. 5, image data for one frame is configured as a set of nine line data, and the line data is stored in the frame buffer 140 in association with the nine scanning line numbers SL1 to SL9. The

  Subsequently, in S5, the current value of the field number FLD assigned to each of a series of fields constituting each frame is set to 1.

  Thereafter, in S6, it is determined whether or not the current field number FLD is an odd number. If it is an odd number, the determination is YES, and in S7, the line data stored in the frame buffer 140 in association with each effective scanning line constituting the current odd field exists in the image display area 158. A readout area that is appropriate to be read out from the frame buffer 140 as data corresponding to the pixel to be determined is set by calculation. The line data corresponding to each effective scanning line is constituted by a plurality of pixel data respectively representing a plurality of pixels located on the effective scanning line.

  For example, the reading area includes the reading start position (address) and the reading end position (address) of the line data corresponding to each effective scanning line, the original inclination angle of each effective scanning line, that is, FIG. The effective scanning lines shown in FIG. 5 are set according to the inclination angle with respect to the horizontal line and the position and size of the image display area 158.

  Subsequently, in S8 of FIG. 4, the same direction as the order in which a plurality of pixel data existing in the set readout area of the frame buffer 140 is stored side by side from the frame buffer 140. That is, as each effective scanning line progresses from the left side to the right side in the current odd field, the pixel data is read in the same direction as the order of reproduction.

  In the present embodiment, since the upper left corner of the image display area 158 is set as the scanning start point and the lower right corner is set as the scanning end point in the first place, the traveling direction of each effective scanning line in the current odd field is the image display. The area 158 is equal to the forward direction scanned.

  The case where the current field number FLD is an odd number has been described above. However, when the field number FLD is an even number, the determination in S6 is NO and the process proceeds to S9.

  In S9, in accordance with S7, the data corresponding to the pixels existing in the image display area 158 among the line data stored in the frame buffer 140 in association with each effective scanning line constituting the current even field. As a result, a reading area suitable for reading from the frame buffer 140 is set by calculation.

  Subsequently, in S10, the plurality of pixel data existing in the set readout area of the frame buffer 140 is in the reverse direction to the order in which the pixel data is stored side by side from the frame buffer 140, that is, In the current even field, as each effective scanning line advances from the right side to the left side, the pixel data is read out in the same direction as the order of reproduction.

  As described above, in this embodiment, since the upper left corner of the image display area 158 is set as the scanning start point and the lower right corner is set as the scanning end point, the progress of each effective scanning line in the current even field is originally set. The direction is equal to the reverse direction in which the image display area 158 is scanned.

  In the present embodiment, image data representing an image to be displayed is configured as a plurality of pixel data (or luminance data) each representing the luminance of a plurality of pixels arranged in a line in the image. Based on the plurality of pixel data, a luminance signal that is sequentially processed by the light source unit 34 is generated.

  The plurality of pixel data is a first luminance data group processed by the light source unit 34 to form an effective scanning line in a period (one-direction scanning period) in which each effective scanning line is scanned in the forward direction in the odd field. And a second luminance data group processed by the light source unit 34 to form an effective scanning line in a period (reverse scanning period) in which each effective scanning line is scanned in the reverse direction in the even field. .

  In the example shown in FIG. 5, the line data with the scanning line number SL of 1 corresponds to the first luminance data group, and the line data with the scanning line number SL of 2 corresponds to the second luminance data group. To do.

  Whether the current field is an odd field or an even field, the current value of the scanning line number SL is set to 1 in S11. In step S12, the scanning control unit 152 waits for the latest horizontal scanning synchronization signal to be generated.

  When the latest horizontal scanning synchronization signal is generated, the determination in S12 is YES, and in S13, the scanning line number corresponding to the image data read in S8 or S10 matches the current value of the scanning line number SL. It is determined whether or not to do so.

  If the scanning line number matches the current value of the scanning line number SL, the determination in S13 is YES, and in S14, the image data read in S8 or S10 is converted into a luminance signal for each color. Then, it is transferred to each driver 28, 30, 32.

  In response to this, each of the lasers 22, 24, and 26 emits a laser beam of each color so that each pixel has a luminance (intensity) corresponding to a corresponding luminance signal. The emitted laser beam of each color is incident on the horizontal scanning unit 70 and the vertical scanning unit 72 as a combined laser beam.

  As a result, in the example shown in FIG. 14 to FIG. 18, when the current field is an odd field (first, third, fifth, or seventh field) as shown in FIG. Each effective scanning line in the field (only the forward scanning line) is formed by the laser beam in the forward direction from the upper side to the lower side, whereby the current odd field is displayed.

  On the other hand, when the current field is an even field (second, fourth, sixth, or eighth field), as shown in FIG. 16, each effective scanning line (forward scanning line) in the current even field. Only) is formed by the laser beam in the reverse direction from the lower side to the upper side, so that the current even field is displayed.

  Thereafter, in S15 of FIG. 4, it is determined whether or not the current value of the scanning line number SL is equal to or greater than the maximum value SLmax. The maximum value SLmax is equal to the number of effective scanning lines belonging to the current field. If it is assumed that the current value of the scanning line number SL is not equal to or greater than the maximum value SLmax, the determination is NO. In S16, the current value of the scanning line number SL is incremented by 1, and the process returns to S12.

  As a result of repeating the execution of S12 to S16 as many times as necessary, if the determination in S15 is YES, it is determined in S17 whether or not the current value of the field number FLD is equal to or greater than the maximum value FLDmax. The maximum value FLDmax is equal to the number of fields belonging to the current frame.

  If it is assumed that the current value of the field number FLD is not equal to or greater than the maximum value FLDmax, the determination in S17 is NO. In S18, the current value of the field number FLD is incremented by 1, and the process returns to S6.

  As a result of repeating the execution of S6 to S18 as many times as necessary, if the determination in S17 is YES, it is determined in S19 whether or not the current value of the frame number FRM is greater than or equal to the maximum value FRMmax. The maximum value FRMmax is equal to the number of frames belonging to the current video.

  If it is assumed that the current value of the frame number FRM is not greater than or equal to the maximum value FRMmax, the determination in S19 is NO, and the current value of the frame number FRM is incremented by 1 in S20, and then the process returns to S3.

  As a result of repeating the execution of S3 to S20 as many times as necessary, if the determination in S19 is YES, one execution of this image display program is completed.

  Next, the principle employed for driving the horizontal scanning unit 70 and the vertical scanning unit 72 will be described with reference to FIGS.

  FIG. 19 conceptually shows the configuration of the scanning control unit 152 in a block diagram. The scanning control unit 152 includes a central control unit 170 configured by the computer 122 and an electronic circuit unit 172 configured by a plurality of electronic circuits.

  The electronic circuit unit 172 includes a state signal generation circuit 180 that generates a state signal that indicates the operating state of the horizontal scanning mirror 80, and a state signal generation circuit 182 that generates a state signal that indicates the operating state of the vertical scanning mirror 90. ing. The electronic circuit unit 172 further generates a state in which the horizontal scanning synchronization signal, the frame synchronization signal, the vertical scanning synchronization signal, and the dot clock signal are temporally associated with each other and the respective frequencies are adjusted. A synchronization signal generation circuit 184 is provided.

  The state signal generation circuit 180 for horizontal scanning is connected to the horizontal scanning driving circuit 100, the horizontal scanning detection circuit 102, the central control unit 170, and the synchronization signal generation circuit 184.

  The horizontal scanning drive circuit 100 determines the amplitude (maximum shake width) of the horizontal scanning mirror 80, which is the horizontal scanning synchronization signal input from the synchronization signal generation circuit 184 and the horizontal scanning amplitude command signal input from the central control unit 170. A sinusoidal drive signal (drive voltage signal) is generated and supplied to a drive source 88 (for example, a piezoelectric element) in order to rotationally vibrate the horizontal scanning mirror 80 based on the commanded signal.

  In the steady state of the horizontal scanning mirror 80, the vibration frequency of the horizontal scanning mirror 80 is equal to the frequency of the driving signal, and the frequency of the driving signal is equal to the frequency of the horizontal scanning synchronization signal. Further, the displacement phase of the horizontal scanning mirror 80 is equal to the phase of the driving signal, and the phase of the driving signal is equal to the phase of the horizontal scanning synchronization signal. Further, the amplitude of the horizontal scanning mirror 80 depends on the amplitude of the driving signal, and the amplitude of the driving signal depends on the horizontal scanning amplitude command signal.

  In FIG. 20, the horizontal scanning synchronization signal and the driving signal for the horizontal scanning mirror 80 are temporally associated with each other and represented by a graph.

  The horizontal scanning detection circuit 102 detects a signal representing a temporal variation in displacement of the horizontal scanning mirror 80 as a displacement signal. The displacement signal is proportional to the deflection angle of the horizontal scanning mirror 80.

  In FIG. 20, the driving signal and the displacement signal of the horizontal scanning mirror 80 are temporally associated with each other and are represented by a graph. These drive signal and displacement signal have a phase difference of 90 degrees in the ideal resonance state of the horizontal scanning mirror 80.

  As shown in FIG. 19, the status signal generation circuit 180 includes a drive signal output from the horizontal scanning drive circuit 100, a displacement signal output from the horizontal scan detection circuit 102, and a dot output from the synchronization signal generation circuit 184. A clock signal and a frame synchronization signal are received.

  The state signal generation circuit 180 synchronizes with the dot clock signal, a digital displacement amplitude signal representing the amplitude of the displacement signal of the horizontal scanning mirror 80, and a digital representing the phase of the displacement signal of the horizontal scanning mirror 80 with respect to the drive signal. A displacement phase signal (pair drive signal) and a digital displacement phase signal (pair frame synchronization signal) representing the phase of the displacement signal of the horizontal scanning mirror 80 with respect to the frame synchronization signal are generated and supplied to the central controller 170. .

  Specifically, the state signal generation circuit 180 detects a peak point of the displacement signal of the horizontal scanning mirror 80, and generates a displacement amplitude signal by A / D converting the signal level of the detected peak point. To do.

  The state signal generation circuit 180 detects the length of time from the zero cross point of the drive signal to the zero cross point of the displacement signal in units of a period of a master clock signal described later, and the detected time length. A displacement phase signal (a drive signal) is generated as a signal to represent.

  This state signal generation circuit 180 detects the length of time from the rising point of the frame synchronization signal to the zero cross point that first appears in the displacement signal from the rising point, with the period of the master clock signal as a unit, and the detection A displacement phase signal (vs. frame synchronization signal) is generated as a signal representing the length of the time thus obtained.

  In FIG. 20, the driving signal, the displacement signal, and the frame synchronization signal for the horizontal scanning mirror 80 are temporally associated with each other and represented in a graph.

  As shown in FIG. 19, the central control unit 170 generates a horizontal scanning amplitude command signal based on various signals supplied from the state signal generation circuit 180 and supplies the horizontal scanning amplitude command signal to the horizontal scanning driving circuit 100, which will be described in detail later. As described above, various command signals are supplied to the synchronization signal generation circuit 184.

  Similarly to the state signal generation circuit 180 for horizontal scanning, the state signal generation circuit 182 for vertical scanning includes a vertical scanning drive circuit 110, a vertical scanning detection circuit 112, a central control unit 170, and a synchronization signal generation circuit. 184.

  Similar to the horizontal scanning drive circuit 100, the vertical scanning drive circuit 110 is a vertical scanning synchronization signal input from the synchronization signal generation circuit 184 and a vertical scanning amplitude command signal input from the central control unit 170, and is a vertical scanning mirror. Based on the signal for instructing the amplitude (maximum amplitude) of 90, a driving source 92 (for example, a piezoelectric element) is generated by generating a sinusoidal driving signal (driving voltage signal) in order to rotationally vibrate the vertical scanning mirror 90. To supply.

  In the steady state of the vertical scanning mirror 90, the vibration frequency of the vertical scanning mirror 90 is equal to the frequency of the driving signal, and the frequency of the driving signal is equal to the frequency of the vertical scanning synchronization signal. Further, the displacement phase of the vertical scanning mirror 90 is equal to the phase of the driving signal, and the phase of the driving signal is equal to the phase of the vertical scanning synchronization signal. Further, the amplitude of the vertical scanning mirror 90 depends on the amplitude of the driving signal, and the amplitude of the driving signal depends on the vertical scanning amplitude command signal.

  In FIG. 20, the vertical scanning synchronization signal and the driving signal for the vertical scanning mirror 90 are temporally associated with each other and represented in a graph.

  The vertical scanning detection circuit 112 detects a signal representing a temporal variation in displacement of the vertical scanning mirror 90 as a displacement signal. The displacement signal is proportional to the deflection angle of the vertical scanning mirror 90.

  As shown in FIG. 19, the state signal generation circuit 182 receives the displacement signal output from the vertical scanning detection circuit 112 and the dot clock signal and frame synchronization signal output from the synchronization signal generation circuit 184.

  This state signal generation circuit 182 represents the phase of the digital displacement amplitude signal indicating the amplitude of the displacement signal of the vertical scanning mirror 90 and the phase of the displacement signal of the vertical scanning mirror 90 relative to the frame synchronization signal in synchronization with the dot clock signal. A digital displacement phase signal (for frame synchronization signal) is generated and supplied to the central control unit 170.

  Specifically, like the state signal generation circuit 180, the state signal generation circuit 182 detects the peak point of the displacement signal of the vertical scanning mirror 90, and A / D converts the signal level of the detected peak point. By doing so, a displacement amplitude signal is generated.

  Like the state signal generation circuit 180, the state signal generation circuit 182 determines the length of time from the rising point of the frame synchronization signal to the zero cross point that first appears in the displacement signal from the rising point of the frame synchronization signal. As a unit, detection is performed, and a displacement phase signal (vs. frame synchronization signal) is generated as a signal representing the detected length of time.

  In FIG. 20, the driving signal of the vertical scanning mirror 90 and the frame synchronization signal are temporally associated with each other and represented by a graph.

  The central control unit 170 generates a vertical scanning amplitude command signal based on the various signals supplied from the state signal generation circuit 182 and supplies the vertical scanning amplitude command signal to the vertical scanning drive circuit 110. Various command signals are supplied to 184.

  As shown in FIG. 19, the drive signal is supplied to the state signal generation circuit 180 for horizontal scanning, and the state signal generation circuit 180 detects the phase difference of the drive signal with respect to the displacement signal. . This is because, as will be described in detail later, tracking control is performed so that the actual vibration frequency of the horizontal scanning mirror 80 follows the actual resonance frequency.

  On the other hand, no drive signal is supplied to the state signal generation circuit 182 for vertical scanning, and the state signal generation circuit 182 does not detect the phase difference of the drive signal with respect to the displacement signal. This is because frequency tracking control is not performed for the vertical scanning mirror 90, unlike the horizontal scanning mirror 80, as will be described in detail later.

As shown in FIG. 20, the horizontal scanning sync signal changes so as to rise in a horizontal scanning period T _H. Vertical scanning synchronization signal varies to rise in the vertical scanning period T _V. The phase difference between the horizontal scanning synchronization signal and the vertical scanning synchronization signal is the aforementioned initial phase difference time Δt. Frame synchronizing signal is changed so as to rise in a frame period T _0.

  As is clear from the above description, in this embodiment, the spot of the laser beam whose intensity is modulated in accordance with the luminance signal for each pixel is converted into a horizontal scan by the horizontal scanning unit 70 and a vertical scan by the vertical scanning unit 72. The retina 16 is scanned by the joint action.

  As long as the trajectory drawn on the retina 16 by the scanning is normal, when arc sine correction is performed on the sine curve defining the trajectory, for example, as shown in FIG. It is expressed so that it is arranged at equal intervals. That is, the scanning line interval is uniform in the regular scanning locus.

FIG. 13 shows an example of a normal scanning locus drawn on the retina 16 when the horizontal scanning reciprocation number n _H is 7 and the vertical scanning reciprocation number n _V is 3, in a state where the arc sine correction is performed. It is represented by a graph. In contrast, in FIG. 21, an example of a regular scan trajectory horizontal scanning roundtrips n _H is 11, is drawn on the retina 16 in the case where the vertical scanning reciprocating frequency n _V is 3, it is performed arcsine correction It is represented in a graph with no state.

In the graph of FIG. 21, the horizontal axis represents the horizontal scanning angle (deflection angle of the horizontal scanning mirror 80) θ _H by the magnification with respect to the horizontal scanning angle amplitude Θ _H , while the vertical axis represents the vertical scanning angle (vertical scanning mirror). 90 deflection angle) theta _V of is represented as a proportion of the vertical scan angle amplitude theta _V.

In order for the scanning trajectory to be normal, the conditions represented by the expressions (3) and (a) in FIG. 12 are satisfied for the horizontal scanning reciprocation number n _H and the vertical scanning reciprocation number n _V , and the initial Regarding the phase difference time Δt, it is necessary that the relationship represented by the equations (3) and (b) in FIG.

  The initial phase difference time Δt means a phase difference between the horizontal scanning synchronization signal and the vertical scanning synchronization signal, as shown in FIG. 20, if attention is paid to the relationship between the horizontal scanning synchronization signal and the vertical scanning synchronization signal. .

Therefore, the initial phase difference time Δt is determined by taking the vertical scanning synchronization signal as a reference and the horizontal scanning synchronization signal advance time relative to the vertical scanning synchronization signal (the time of the horizontal scanning angle θ _{H with} respect to the time variation of the vertical scanning angle θ _V ). corresponding to a phase advance of the change.) means, conversely, if based on the horizontal scanning sync signal, vertical with respect to time variations in the vertical scanning synchronization signal delay time for the horizontal sync signal (horizontal scanning angle theta _H corresponding to a phase delay of the time variation of scan angle theta _V.) means.

  The initial phase difference time Δt is a physical quantity that is important to be accurately managed so that the actual scanning trajectory is normal. If the actual value of the initial phase difference time Δt deviates from the ideal value beyond the limit, the scanning line interval becomes non-uniform and the image quality deteriorates. Specifically, in the scanning trajectory, the interval between the scanning lines alternately changes between a narrow interval and a wide interval for each scanning line in the vertical scanning direction.

When the error ε from the ideal value of the actual value of the initial phase difference time Δt increases and reaches 1 / (4n _H · n _V · f ₀ ), two adjacent scan lines overlap each other in the normal scanning locus. Will end up.

  Therefore, as long as the two scanning lines adjacent to each other do not overlap with each other, the maximum value εmax of the allowable value εalw of the error ε of the initial phase difference time Δt is defined as FIG. In the formula (11).

  However, the closer the error ε of the initial phase difference time Δt is to 0, the closer the actual scanning locus is to the ideal scanning locus. Therefore, in the present embodiment, the allowable value εalw of the error ε of the initial phase difference time Δt is expressed by Expression (12) in FIG.

  For example, the coefficient γ is preferably a numerical value of 10 or less, more preferably a numerical value of 8 or less, and further preferably a numerical value of 6 or less.

In order to guarantee a normal scanning trajectory, the reciprocating motion of the laser beam spot in the horizontal direction (time variation of the horizontal scanning angle θ _H ) and the reciprocating motion in the vertical direction (time variation of the vertical scanning angle θ _V ). It is important to accurately adjust the relative phase between them. Therefore, the scanning control unit 152 is designed so that the relative phase is managed with sufficient accuracy, and thereby the horizontal scanning by the horizontal scanning unit 70 and the vertical scanning by the vertical scanning unit 72 are synchronized with sufficient accuracy. Is important.

The level of accuracy to be achieved by the scanning control unit 152 is that the frame frequency f ₀ (= 1 / T ₀ ) is 60 Hz, the number of scanning lines in one frame is 1,000, and the horizontal scanning reciprocation number n. _H is 1,000, taking the case where the vertical scanning reciprocating frequency _{n V} is 11 as an example, it will be described in detail.

In this embodiment, next to the horizontal scanning frequency _{f H} is 60 kHz, the vertical scanning frequency _{f V} becomes 660 Hz. Furthermore, some of the figures mentioned above into equation (3) (b) of FIG. 12, and, when any integer n in the formula and 0, with the vertical scanning period T _V, the equation of FIG. 22 (13) is induced.

In this equation (13), “Δt / T _V ” means the vertical scanning delay time ratio, and in the above specific example, the ideal value of the vertical scanning delay time ratio is “1 / 4,000”. . This vertical scanning delay time ratio can be converted into an angle [deg] as shown in Expression (14) of FIG.

  Therefore, in this specific example, the ideal value of the angle converted from the vertical scanning delay time ratio is 0.09 deg.

In this embodiment, the horizontal scanning time advance ratio, i.e., the ideal value of Delta] t / T _H is "1/44", and also, an ideal value of the angle that has been converted from the horizontal scanning time advance ratio is about 8 deg.

  Thus, the ideal value of the angle converted from the vertical scanning delay time ratio is much smaller than the ideal value of the angle converted from the horizontal scanning advance time ratio. Such a relationship between both ideal values also holds in other general scanning devices. Therefore, since the actual value of the angle converted from the vertical scanning delay time ratio matches the ideal value, the accuracy required for vertical scanning is the ideal value of the angle converted from the horizontal scanning advance time ratio. Higher than the accuracy required for horizontal scanning.

  On the other hand, the angle converted from the vertical scanning delay time ratio is proportional to the frequency of the vertical scanning synchronization signal. Similarly, the angle converted from the horizontal scanning advance time ratio is also proportional to the frequency of the horizontal scanning synchronization signal. Therefore, the accuracy required for the vertical scanning synchronization signal is higher than the accuracy required for the horizontal scanning synchronization signal. In general, as long as the same system is used, the frequency and phase of the vertical scanning synchronization signal and the frequency and phase of the horizontal scanning synchronization signal are controlled with the same relative accuracy.

  Therefore, in the present embodiment, since the actual scanning trajectory is normal, the optical scanning unit 20 is designed to control the frequency and phase of the vertical scanning synchronization signal with accuracy that satisfies the required accuracy. .

  As described above, unless the two scanning lines adjacent to each other in the scanning locus overlap each other, if the actual scanning locus is defined as normal, the ideal value of the vertical scanning delay time ratio is the vertical scanning. The actual value of the delay time ratio is separated from the ideal value, that is, equal to the maximum value Emax of the allowable value Ealw of the error E. Further, the allowable value Ealw is described by Expression (15) in FIG. 22 by using the coefficient γ described above.

  As is clear from the above description, in the present embodiment, both the horizontal scanning unit 70 and the vertical scanning unit 72 are configured as a mechanical resonance system, and the horizontal scanning unit 70 is ideally composed of the horizontal scanning mirror 80. Are operated with the actual vibration frequency matching the actual resonance frequency. Similarly, the vertical scanning unit 72 is ideally operated in a state where the actual vibration frequency of the vertical scanning mirror 90 matches the actual resonance frequency.

  The resonance frequency of both the horizontal scanning mirror 80 and the vertical scanning mirror 90 depends on the mechanical properties of the respective mirrors 80 and 90. Its mechanical properties change due to manufacturing variations, operating environments (eg, environmental temperature, environmental humidity), aging (eg, degradation), and the like. Therefore, the resonance frequency varies.

  Therefore, in order to maintain the horizontal scanning mirror 80 and the vertical scanning mirror 90 in a resonance state in spite of such dependence, the oscillation frequency of the mirrors 80 and 90 is made to follow the actual resonance frequency, that is, Frequency tracking is necessary.

On the other hand, in order for the actual scanning trajectory to be normal, as described above, the condition that the ratio between the horizontal scanning frequency and the vertical scanning frequency is expressed as a relatively prime integer ratio n _H : n _V is satisfied. There must be.

  However, it is virtually impossible to perform frequency tracking for both the horizontal scanning mirror 80 and the vertical scanning mirror 90 so as to be parallel to each other in time and independent from each other while satisfying this condition at all times. Is possible.

On the other hand, in this embodiment, the Q value Q _H of the horizontal scanning unit 70 is higher than the Q value Q _V of the vertical scanning unit 72 in order to generate a larger resonance energy in the vertical scanning unit 72 in the horizontal scanning unit 70. It is set large. An example of the Q _H value is about 1000 and an example of the Q _V value is about 100.

  In general, the Q value of a mechanical resonance system is a value representing the strength of resonance. The Q value is defined by the equation (16) in FIG. 22 when the energy lost per unit time due to Joule heat or the like is represented by S when resonance occurs with the energy W under the frequency ω.

  Furthermore, in general, the greater the Q value of the mechanical resonance system, the more sensitive the resonance energy is to the deviation of the actual vibration frequency from the actual resonance frequency. On the other hand, when the resonance energy is reduced, the vibration amplitude of the mechanical resonance system is reduced, and thereby the scanning angle range of the laser beam (the maximum deflection width of the laser beam during scanning) is reduced.

  Therefore, in the present embodiment, only the horizontal scanning unit 70 is tracking-controlled so that the actual scanning frequency of the horizontal scanning mirror 80 follows the actual resonance frequency.

In each tracking control, the frequency f _H of the horizontal scanning synchronization signal is changed almost instantaneously and discretely (stepwise) with the step width Δf _H. Is repeated until the phase difference of the horizontal scanning mirror 90 is restored to the normal value, that is, until the vibration state of the horizontal scanning mirror 90 is restored to the resonance state.

In each round of the tracking control, the frequency f _H of the horizontal scanning sync signal is changed, also changed the frequency f _V of the vertical scanning synchronization signal accordingly. This is because, as described above, the horizontal scanning frequency f _H and the vertical scanning frequency f _V are expressed as a prime integer ratio n _H : n _V in order to maintain the actual scanning trajectory to be normal. This is because the relationship must be established.

  Further, in the present embodiment, during tracking control, the phase of the horizontal scanning synchronization signal and the phase of the vertical scanning synchronization signal are corrected so that the initial phase difference time Δt can be continuously realized.

However, the in reality, in the horizontal scanning unit 70, the actual oscillation frequency of the horizontal scanning mirror 80, sensitively follow the instantaneous change of f _H (command value of the frequency) the frequency of the horizontal scan synchronization signal hand, in the vertical scanning unit 72, the actual oscillation frequency of the vertical scanning mirror 90 does not follow the less sensitive to momentary changes of f _V (command value of the frequency) the frequency of the vertical scanning synchronization signal. The same applies to the vibration phase.

Therefore, in each round of the tracking control, the frequency f _H of the horizontal scanning sync signal is changed once, and the actual vibration frequency of actual vibration frequency and the vertical scanning mirror 90 in the horizontal scanning mirror 80 is relatively prime And the actual value of the phase difference time (hereinafter referred to as “scanning phase difference time Δt”) between the time variation of the deflection angle of the horizontal scanning mirror 80 and the time variation of the deflection angle of the vertical scanning mirror 90 is the initial value. A period in which the condition of matching the ideal value of the phase difference time Δt is not established transiently occurs.

Therefore, in each round of the tracking control, the frequency f _H of the horizontal scanning sync signal is changed once, temporarily no longer match the actual scanning trace the most ideal scanning trace, this scanning phase difference This causes a transient fluctuation of time Δt.

  In each tracking control, even if the transient fluctuation of the scanning phase difference time Δt cannot be completely avoided, the degree to which the observer can easily notice the degree of deterioration of the actual scanning trajectory due to the transient fluctuation. As long as it is not exceeded, there is no apparent hindrance even if the transient fluctuation is allowed.

Therefore, in the present embodiment, the step width Δf _H is set so that the error ε transiently generated in the scanning phase difference time Δt does not exceed the above-described allowable value εalw.

  In general, when the actual vibration frequency of the scanning mirror changes by Δf from the actual resonance frequency fr in a state where the driving voltage applied to the driving source of the scanning mirror which is a mechanical resonance system is constant, the scanning mirror is supplied to the driving source. A phase change Δφ [rad] occurs between the drive signal and the displacement signal reflecting the operation of the scanning mirror.

  The phase change Δφ is generally defined by Expression (17) in FIG. 22 in the vicinity of the resonance frequency fr.

In order for the actual scanning trajectory to be normal despite the occurrence of the phase change Δφ, the phase change Δφ _V for the vertical scanning is equal to the vertical scanning delay time ratio, as is apparent from the above description. It is necessary that the converted angle [rad] does not exceed and the phase change Δφ _H for the horizontal scanning does not exceed the converted angle [rad] for the horizontal scanning advance time ratio. This is described by equation (18) in FIG.

  “Δt” in the equation (18) is described by the equation (19) in FIG. 22, as is clear from the above description.

  Therefore, Expression (18) is converted to Expression (20) and Expression (21) in FIG. 22 by also using Expression (17). However, in using the equation (17), the magnitude of the phase change Δφ is considered, but the sign is ignored.

In this embodiment, the step width Δf _H for discretely changing the frequency of the horizontal scanning synchronization signal is set so as to satisfy Expression (20) during tracking control, and the frequency of the vertical scanning synchronization signal is discretely set. The step width Δf _V to be changed to is set so as to satisfy the equation (21).

  As described above, in this embodiment, as will be described in detail later with reference to FIG. 19, the synchronization signal processing unit 152 digitally processes the synchronization signal by a combination of the computer 122 and a plurality of electronic circuits. Designed to be On the other hand, the conventional synchronization signal processing unit processes the synchronization signal in an analog manner using the PLL as a basic component.

Therefore, according to the present embodiment, the frequency of the horizontal scanning synchronization signal is discretely changed with a small step size Δf _H with high accuracy, and the frequency of the vertical scanning synchronization signal is changed discretely with a small step size Δf _V. Can be realized more easily than the conventional synchronization signal processing unit.

  Here, the synchronization signal generation circuit 184 in the present embodiment will be described in detail with reference to FIG.

The synchronizing signal generating circuit 184 includes a master oscillator 190 for generating a master clock signal at a master clock frequency Fmst, divided by the master clock signal frequency division number n _D outputted from the master oscillator 190 (of the master clock signal dividing the frequency by the frequency division number n _D), thereby, and a frequency divider 192 for generating a dot clock signal dot clock frequency f _D.

In a specific example in which the frame frequency f ₀ is 60 Hz, the horizontal scanning reciprocation number n _H is 1,000, the vertical scanning reciprocation number n _V is 11, and the number N of dots in one scanning line is 1,000, a dot clock The frequency f _D is 2f ₀ · n _H · N = 120 MHz.

In the present embodiment, the frequency divider 192 is operated so that the relationship represented by the formula f _D = fmst / 4 is established. In this divider, the division number n _D is 4. Therefore, in this specific example, the master clock frequency fmst is 480 MHz.

  As illustrated in FIG. 19, the synchronization signal generation circuit 184 further includes a PLL clock supply unit 194. The clock supply unit 194 includes a frequency divider 196, a frequency divider 198, an error voltage signal generation circuit 200 including a phase comparator and a filter (for example, a loop filter), a voltage controlled oscillator VCO 204, and a frequency divider 206. Are included.

The master clock signal output from the master oscillator 190 is supplied to the clock supply unit 194 as a reference signal after the frequency of the master clock signal is divided by a variable frequency division number n ₀₁ by the frequency divider 196. . The reference signal is compared with an oscillation signal described later in a phase comparator of the error voltage signal generation circuit 200, and an analog error voltage signal indicating a frequency difference (clock error) between the reference signal and the oscillation signal is an error voltage signal. Smoothed by the filter of the generation circuit 200.

  The smoothed error voltage signal is supplied to the voltage controlled oscillator VCO 204 as an analog control signal. The voltage controlled oscillator VCO 204 generates a digital oscillation signal based on the supplied control signal.

  In the present embodiment, the plurality of electronic circuits constituting the synchronization signal generation circuit 184 are configured as digital circuits except for the error voltage signal generation circuit 200 and the voltage controlled oscillator VCO 204. Thereby, it is ensured that the amount (error) of the transient fluctuation of the scanning phase difference time Δt caused by the discrete change of the main scanning frequency and the sub scanning frequency does not exceed the allowable value εalw.

The generated oscillation signal is frequency-divided by the frequency divider n _HV by the frequency divider 206 and then output from the clock supply unit 194. The output oscillation signal is frequency-divided by the frequency dividing number n ₀₂ by the frequency divider 198 and then input to the phase comparator of the error voltage signal generation circuit 200.

In the clock supply unit 194, when the frequency of the output signal of the frequency divider 206 is expressed by _fHV , the relationship expressed by the equations (31) and (32) in FIG.

In the above specific example, the frequency division number n ₀₁ is 4800000, the frequency division number n ₀₂ is 6600, and the frequency division number n _HV is 100.

As shown in FIG. 19, the frequency divider 196 is connected to the central control unit 170. The frequency divider 196 is designed to discretely change the frequency division number n ₀₁ by 1 in accordance with a command signal input from the central control unit 170.

That is, the frequency divider 196 is such that its frequency dividing number n ₀₁ is digitally finely changed. With the discrete change of the frequency dividing number n ₀₁ , the frequency f _HV of the output signal of the frequency divider 206 changes instantaneously and discretely.

As shown in FIG. 19, the synchronizing signal generating circuit 184 further includes a frequency divider 210 for dividing by the frequency of the output signal of the divider 206 dividing number n _V, the output signal of the divider 210 And a delay circuit 212 for delaying with a variable delay time.

The output signal of the master oscillator 190 is input to the delay circuit 212 together with the output signal of the frequency divider 210. The delay circuit 212 is configured as a digital circuit, and, as is well known, by counting the number of master clock pulses input from the master oscillator 190, the output signal of the frequency divider 210 is input. The length of the delay time Δt _H until output is controlled.

The delay circuit 212 is designed to change the length of the delay time Δt _H by changing the target count number of the master clock pulse in accordance with a command signal input from the central control unit 170.

That is, in the delay circuit 212, the length of the delay time Δt _H is digitally changed minutely. The output signal of the delay circuit 212 is supplied to the horizontal scanning drive circuit 100 as a horizontal scanning synchronization signal.

As shown in FIG. 19, the synchronization signal generation circuit 184 further divides the frequency of the output signal of the frequency divider 206 by the frequency division number n _H and the output signal of the frequency divider 216. A delay circuit 218 for delaying with a variable delay time.

The delay circuit 218 receives the output signal of the master oscillator 190 together with the output signal of the frequency divider 216. This delay circuit 218 is configured as a digital circuit, like the delay circuit 212, and receives the output signal of the frequency divider 210 by counting the number of master clock pulses input from the master oscillator 190. The length of the delay time Δt _V until output is controlled.

Similarly to the delay circuit 212, the delay circuit 218 changes the length of the delay time Δt _V by changing the target count number of the master clock pulse in accordance with the command signal input from the central control unit 170. Designed.

That is, the delay circuit 218 is configured such that the length of the delay time Δt _V is minutely changed digitally. The output signal of the delay circuit 218 is supplied to the vertical scanning drive circuit 110 as a vertical scanning synchronization signal.

As described above, in this embodiment, the frequency divider 210 and the frequency divider 216 are connected to the frequency divider 206 in parallel, and the frequency dividers 210 and 216 respectively separate signals having the same frequency. divide by division number _{n V} and _{n H.}

They divisor n _V and n _H is an integer ratio and the frequency of the frequency and the vertical scanning synchronization signal of the horizontal scanning sync signal are disjoint, i.e., n _H: In _n V _(the above examples is 1000: 11).

Therefore, in the present embodiment, even if the frequency division number n ₀₁ of the frequency divider 196 is changed to change the frequency of the horizontal scanning synchronization signal, the vertical frequency and the frequency of the horizontal scanning synchronization signal are excluded except for a transient period. The relationship that the frequency of the scanning synchronization signal is relatively prime is maintained.

As shown in FIG. 19, the synchronization signal generation circuit 184 further includes a frequency divider 220 that divides the frequency of the output signal of the frequency divider 216 by the frequency division number n _V (11 in the above specific example). I have. The output signal of the frequency divider 200 is supplied to the state signal generation circuits 180 and 182 as a frame scanning synchronization signal.

  In the present embodiment, the scanning phase difference time Δt is set by the combined action of the phase of the horizontal scanning synchronization signal being adjusted by the delay circuit 212 and the phase of the vertical scanning synchronization signal being adjusted by the delay circuit 218. It is managed accurately.

  FIG. 24 conceptually shows a flowchart of the above-described scanning control program executed in the central control unit 170.

  This scanning control program is repeatedly executed. At each execution, first, in S101, the displacement signal, displacement phase signal (pair drive signal), and displacement phase signal (frame synchronization signal) of the horizontal scanning mirror 80 are read from the state signal generation circuit 180. .

  Next, in S102, it is determined whether or not the displacement phase represented by the read displacement phase signal (to drive signal) is equal to the target value. If it is assumed that the displacement phase (the driving signal) is equal to the target value this time, the determination is YES and the process proceeds to S103.

On the other hand, if it is assumed that the displacement phase (the drive signal) is not equal to the target value this time, the determination in S102 is NO. Thereafter, in S108, a command signal is output to the frequency divider 196 in order to change the frequency division number _n01 by one. The execution of S108 and S102 is repeated until the displacement phase (the drive signal) becomes equal to the target value by repeatedly changing the frequency dividing number _n01 by one.

In the present embodiment, the optimum value of the frequency division number n ₀₁ is determined in an exploratory manner. Specifically, for example, paying attention to the relationship represented by Expression (17) in FIG. 22, the direction in which the displacement phase (the drive signal) deviates from the target value is either increased or decreased. In accordance with the determined bias direction, the changing direction of the frequency dividing number n ₀₁ is determined to be either increase or decrease. More specifically, when the displacement phase (the drive signal) is smaller than a target value (for example, 90 degrees), the frequency division number _n01 is decreased by 1 to increase the horizontal scanning frequency.

By repeating the execution of S102 and S108, each time the frequency division number _n01 is changed by 1 from its initial value, it is determined whether or not the displacement phase (the drive signal) is equal to the target value.

In the present embodiment, when the frequency division number n ₀₁ is changed by 1, the frequency f _H of the horizontal scanning synchronization signal is changed by the step width Δf _H accordingly. The horizontal scanning unit 70 and the synchronization signal generation circuit 184 are designed so that the step width Δf _H , that is, the minimum discrete change amount satisfies the condition shown by the equation (20) in FIG. The step size Δf _H takes a value of 10 ⁻⁶ or less, for example.

In the present embodiment, when the frequency division number n ₀₁ is changed by 1, the frequency f _V of the vertical scanning synchronization signal is also changed by the step width Δf _V accordingly. The vertical scanning unit 72 and the synchronization signal generating circuit 184 are designed so that the step width Δf _V , that is, the minimum discrete change amount satisfies the condition shown by the equation (21) in FIG. The step width Δf _V takes a value of 10 ⁻⁶ or less, for example.

  In any case, if the determination in S102 is YES, it is determined in S103 whether or not the displacement amplitude represented by the read displacement amplitude signal is equal to the target value. If it is assumed that the displacement amplitude is equal to the target value this time, the determination is YES, and the process proceeds to S104.

  On the other hand, if it is assumed that the displacement amplitude is not equal to the target value this time, the determination in S103 is NO. Thereafter, in S109, the horizontal scanning amplitude command signal is changed by a fixed or variable set amount based on the direction and amount in which the displacement amplitude deviates from the target value, and the changed horizontal scanning amplitude command signal is horizontal scanned. It is output to the drive circuit 100. The execution of S109 is repeated until the determination in S103 becomes YES.

  In any case, if the determination in S103 is YES, in S104, it is determined whether or not the displacement phase represented by the read displacement phase signal (to the frame synchronization signal) is equal to the target value. If it is assumed that the displacement phase (vs. frame synchronization signal) is equal to the target value this time, the determination is YES and the process proceeds to S105.

On the other hand, if it is assumed that the displacement phase (vs. frame synchronization signal) is not equal to the target value this time, the determination in S104 is NO. Thereafter, in S110, a command signal is sent to the delay circuit 212 in order to correct the delay time Δt _H of the horizontal scanning synchronization signal with a fixed or variable set amount based on the direction and amount in which the displacement phase is out of the target value. Is output. The execution of S110 is repeated until the determination in S104 is YES.

  In any case, when the determination in S104 is YES, in S105, the displacement signal of the vertical scanning mirror 90 and the displacement phase signal (for frame synchronization signal) are read from the state signal generation circuit 182.

  Subsequently, in S106, it is determined whether or not the displacement phase represented by the read displacement phase signal (vs. frame synchronization signal) is equal to the target value. If it is assumed that the displacement phase (vs. frame synchronization signal) is equal to the target value this time, the determination is YES and the process proceeds to S107.

On the other hand, if it is assumed that the displacement phase (vs. frame synchronization signal) is not equal to the target value this time, the determination in S106 is NO. Thereafter, in S111, a command signal is sent to the delay circuit 218 in order to correct the delay time Δt _V of the vertical scanning synchronization signal with a fixed or variable set amount based on the direction and amount in which the displacement phase deviates from the target value. Is output. The execution of S111 is repeated until the determination in S106 is YES.

In the present embodiment, the sum of the displacement phase of the horizontal scanning synchronization signal (vs. frame synchronization signal) and the displacement phase of the vertical scanning synchronization signal (vs. frame synchronization signal) is equal to the scanning phase difference time Δt. Therefore, in S110 and S111, the delay time Δt _H and the delay time Δt _V are the sum of the displacement phase of the horizontal scanning synchronization signal (vs. frame synchronization signal) and the displacement phase of the vertical scanning synchronization signal (vs. frame synchronization signal), respectively. Is set to be equal to the ideal value of the scanning phase difference time Δt.

  In any case, if the determination in S106 is YES, it is determined in S107 whether or not the displacement amplitude represented by the read displacement amplitude signal is equal to the target value. This time, if it is assumed that the displacement amplitude is equal to the target value, the determination is YES, and one execution of this scanning control program ends.

  On the other hand, if it is assumed that the displacement amplitude is not equal to the target value this time, the determination in S107 is NO. Thereafter, in S112, the vertical scanning amplitude command signal is changed by a fixed or variable set amount based on the direction and amount in which the displacement amplitude deviates from the target value, and the changed vertical scanning amplitude command signal is changed to the vertical scanning. It is output to the drive circuit 110. The execution of S110 is repeated until the determination in S107 is YES.

  In any case, when the determination in S107 is YES, one execution of this scanning control program is terminated.

  As is clear from the above description, in the present embodiment, the RSD 10 constitutes an example of an “optical scanning display” according to the item (1), and the light source unit 34 is an example of the “light source unit” in the same term. The optical scanning unit 20 is an example of the “scanning device” in the same section.

  Further, in the present embodiment, the luminance signal generation unit 150 configures an example of the “luminance signal control unit” in the above item (1), and at least the horizontal scanning detection circuit 102 configures an example of the “detection unit” in the same term. The horizontal scanning driving circuit 100 and the vertical scanning driving circuit 112 jointly constitute an example of the “driving signal generating unit” in the same section.

  Further, in the present embodiment, horizontal scanning corresponds to an example of “main scanning” in the item (1), vertical scanning corresponds to an example of “sub scanning” in the item, and the horizontal scanning unit 70 corresponds to the same item. The horizontal scanning mirror 80 constitutes an example of “first mechanical resonance system” in the same term, and the vertical scanning part 72 constitutes an example of “sub-scanning part” in the same term. The vertical scanning mirror 90 constitutes an example of the “second mechanical resonance system” in the same section.

  Further, in the present embodiment, the horizontal scanning synchronization signal constitutes an example of the “main scanning synchronization signal” in the item (1), and the vertical scanning synchronization signal constitutes an example of the “sub-scanning synchronization signal” in the item. The horizontal scanning unit 70 constitutes an example of “following control target” in the same term, and the horizontal scanning synchronization signal constitutes an example of “target synchronization signal” in the same term.

  Further, in the present embodiment, the state signal generation circuit 180, the frequency divider 196, and the portion of the computer 122 that executes S101, S102, and S108 in FIG. An example of the “synchronization signal control unit” is configured, and the frequency divider 216 configures an example of the “second synchronization signal control unit” in the same section.

  Further, in the present embodiment, the state signal generation circuit 180, the frequency divider 196, and the part of the computer 122 that executes S101, S102, and S108 in FIG. It constitutes an example of a “frequency control unit”.

Further, in the present embodiment, the frequency divider 216 constitutes an example of the “second frequency control unit” in the item (3), and a disjoint integer ratio n representing the ratio between the horizontal scanning frequency and the vertical scanning frequency. _H: n _V corresponds to an example of the "settings ratio" in the item (4), constitutes an example of a "follow-up control subject" horizontal scanning part 70 in the mode (5), wherein the horizontal scanning mirror 80 ( This constitutes an example of the “first mechanical resonance system” in item 6).

  Further, in the present embodiment, the horizontal scanning unit 70 constitutes an example of the “main scanning unit” in the item (7), and the horizontal scanning angle corresponds to an example of the “main scanning deflection angle” in the same term. The scan detection circuit 102 constitutes an example of the “detection unit” in the same term, and the displacement phase (pair drive signal) represented by the displacement signal (pair drive signal) corresponds to an example of the “phase difference” in the term, Since the state signal generation circuit 180, the frequency divider 196, and the part of the computer 122 that executes S101, S102, and S108 in FIG. 24 together form an example of the “phase difference control unit” in the same term. is there.

  Further, in the present embodiment, the scanning phase difference time Δt (the displacement phase (versus frame synchronization signal) represented by the displacement signal for horizontal scanning (versus frame synchronization signal) and the displacement signal (pair The displacement phase represented by the frame synchronization signal) is defined by a combination with the displacement phase (vs. frame synchronization signal).) Corresponds to an example of the “phase difference” in the item (8), and the state signal generation circuits 180 and 182 The delay circuits 212 and 218 and the portion of the computer 122 that executes S101, S104, S105, S106, S110, and S111 in FIG. 24 jointly constitute an example of the “phase changing unit” in the same term. It is.

  Further, in the present embodiment, the RSD 10 constitutes an example of the “light scanning display” according to the item (9), the light source unit 34 constitutes an example of the “light source part” in the term, and the optical scanning unit 20 Constitutes an example of the “scanning device” in the same section.

Further, in the present embodiment, the luminance signal generation unit 150 constitutes an example of the “luminance signal control unit” in the item (9), and the horizontal scanning detection circuit 102 and the vertical scanning detection circuit 112 cooperate with each other. That is, an example of the “detection unit” in the section is configured, and the horizontal scanning drive circuit 100 and the vertical scanning drive circuit 110 together form an example of the “drive signal generation unit” in the same section.

  Further, in the present embodiment, horizontal scanning corresponds to an example of “main scanning” in the item (9), vertical scanning corresponds to an example of “sub scanning” in the item, and the horizontal scanning unit 70 corresponds to the same item. The horizontal scanning mirror 80 constitutes an example of “first mechanical resonance system” in the same term, and the vertical scanning part 72 constitutes an example of “sub-scanning part” in the same term. The vertical scanning mirror 90 constitutes an example of the “second mechanical resonance system” in the same section.

Further, in the present embodiment, the horizontal scanning synchronization signal constitutes an example of the “main scanning synchronization signal” in the above item (9), and the vertical scanning synchronization signal constitutes an example of the “sub-scanning synchronization signal” in the same term. N _H : n _V, which is a ratio of prime integers, corresponds to an example of “setting ratio” in the same term, and a horizontal scanning angle corresponds to an example of “main scanning deflection angle” in the same term, and vertical scanning. The angle corresponds to an example of “sub-scanning deflection angle” in the same term.

Further, in the present embodiment, the state signal generation circuit 180, the frequency dividers 196 and 216, and the part of the computer 122 that executes S101, S102, and S108 in FIG. An example of “frequency changing unit” is configured, step size Δf _H corresponds to an example of “main scanning frequency step size” in the same term, and step size Δf _V corresponds to an example of “sub scanning frequency step size” in the same term. It is doing.

  Furthermore, in the present embodiment, the allowable value εalw represented by the equation (12) in FIG. 22 corresponds to an example of the “allowable range” in the term (9) (range where the width is 0), and the equation (20 ) Corresponds to an example of the “first allowable value” in the same term, and the numerical value represented by the term written on the right side of the equation (21) This corresponds to an example of “second allowable value”.

  Further, in the present embodiment, the state signal generation circuit 180, the frequency divider 196, and the part of the computer 122 that executes S101, S102, and S108 in FIG. Configures an example of “synchronization signal control unit”, frequency divider 216 configures an example of “second synchronization signal control unit” in the same term, and horizontal scanning unit 70 configures an example of “following control target” in the same term The horizontal scanning synchronization signal constitutes an example of the “target synchronization signal” in the same section.

  Further, in the present embodiment, the scanning phase difference time Δt corresponds to an example of the “phase difference” in the item (13), and the state signal generation circuits 180 and 182, the delay circuits 212 and 218, and the computer 122 24, the portions that execute S101, S104, S105, S106, S110, and S111 together form an example of the “phase changing unit” in the same term.

  As mentioned above, although one embodiment of the present invention was described in detail based on a drawing, this is an illustration, and it is various based on the knowledge of those skilled in the art including the aspect described in the section of the [Disclosure of the Invention]. The present invention can be implemented in other forms that have been modified or improved.

1 is a system diagram showing a retinal scanning display 10 according to an embodiment of the present invention. FIG. It is a top view which shows the horizontal scanning part 70 in FIG. 2 is a block diagram conceptually showing an optical scanning unit 20, a light source unit 34, and a signal processing circuit 120 in FIG. 4 is a flowchart conceptually showing an image display program executed by a computer 122 in FIG. 3. It is a figure for demonstrating the logical structure of the frame buffer 140 in FIG. 3 in a tabular form. 4 is a graph showing a horizontal scan drive signal supplied from the horizontal scan drive circuit 100 to the drive source 88 and a vertical scan drive signal supplied from the vertical scan drive circuit 110 to the drive source 110 in FIG. 3. FIG. 2 is a block diagram representing the functions performed by the optical scanning unit 20, the light source unit 34, and the signal processing circuit 120 in FIG. 8 is a timing chart showing a horizontal scanning synchronization signal, a vertical scanning synchronization signal, and a frame synchronization signal in FIG. 7. It is a front view which shows the several effective scanning line formed in order to display an image with the conventional interlace scan system. It is a front view showing an example of a plurality of effective scanning lines formed in order to display an image by dividing each frame of an image into three or more fields and scanning. It is a front view which shows another example of the some effective scanning line formed in order to display an image by the method of dividing and dividing each frame of an image into three or more fields. It is a figure explaining the geometric characteristic of a plurality of scanning lines formed as a Lissajous figure by the cooperative action of horizontal scanning and vertical scanning. FIG. 13 is a front view showing an example of a plurality of scanning lines expressed by the formula shown in FIG. 12. It is a figure for demonstrating formation of the scanning line by execution of the image display program shown in FIG. It is another figure for demonstrating formation of the scanning line by execution of the image display program shown in FIG. FIG. 5 is still another diagram for explaining the formation of scanning lines by executing the image display program shown in FIG. 4. FIG. 5 is still another diagram for explaining the formation of scanning lines by executing the image display program shown in FIG. 4. FIG. 5 is still another diagram for explaining the formation of scanning lines by executing the image display program shown in FIG. 4. It is a block diagram which shows the detail of the synchronizing signal process part 152 in FIG. It is a timing chart for demonstrating the time transition of the various signals in FIG. It is a front view which shows an example of the scanning locus | trajectory formed as a Lissajous figure by the cooperative action of horizontal scanning and vertical scanning. It is a several formula for demonstrating the design of the synchronizing signal process part 152 shown in FIG. 20 is another plurality of equations for explaining the design of the synchronization signal processing unit 152 shown in FIG. 19. 20 is a flowchart conceptually showing a scanning control program executed by a computer 122 shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Retina scanning display 20 Optical scanning unit 34 Light source part 70 Horizontal scanning part 72 Vertical scanning part 80 Horizontal scanning mirror 90 Vertical scanning mirror 100 Horizontal scanning drive circuit 102 Horizontal scanning detection circuit 110 Vertical scanning driving circuit 112 Vertical scanning detection circuit 120 Signal Processing circuit 122 Computer 150 Luminance signal generation unit 152 Synchronization signal processing unit 180 Status signal generation circuit 182 Status signal generation circuit 184 Synchronization signal generation circuit 196 Frequency divider 210 Frequency divider 212 Delay circuit 216 Frequency divider 218 Delay circuit

Claims (9)

An optical scanning display that displays an image by two-dimensional scanning of a light beam,
A light source unit that emits the luminous flux at a luminance according to a luminance signal;
A scanning device that reciprocally scans a light beam emitted from the light source unit in a main scanning direction and a sub-scanning direction that intersect each other, and (a) based on a main scanning drive signal, the light beam is converted into a first mechanical resonance. A main scanning unit capable of reciprocating scanning in the main scanning direction using a system, and (b) based on a sub-scanning drive signal, the light beam is transmitted using a second mechanical resonance system, A sub-scanning unit capable of reciprocating scanning in the sub-scanning direction, and performing reciprocating scanning more times in the sub-scanning direction in the main scanning direction for each frame of the image;
The luminance signal is generated on the basis of the video signal so that one frame of the image is divided into three or more fields and scanned and displayed by the scanning device, and is effective in the entire period of each round-trip scanning. The generated luminance signal is transmitted to the light source unit so that effective scanning lines formed by the light source unit actually emitting a light beam during a scanning period do not overlap each other in the three or more fields in the same frame. A luminance signal control unit to output to
A detection unit for detecting a scanning state of the scanning device;
A synchronization signal generator for generating a main scanning synchronization signal and a sub-scanning synchronization signal;
A drive signal generator for generating the main scan drive signal and the sub scan drive signal based on the generated main scan synchronization signal and sub scan synchronization signal, respectively,
The first mechanical resonance system and the second mechanical resonance system each have a Q value that is different from each other in size.
Of the main scanning unit and the sub-scanning unit, the higher Q value of the corresponding mechanical resonance system is a tracking control scanning unit that is controlled to follow the resonance frequency of itself,
Of the main scanning synchronization signal and the sub-scanning synchronization signal, the one corresponding to the scanning control unit for tracking control is a tracking control synchronization signal for performing the tracking control,
The synchronization signal generator is
First synchronization signal control for controlling the frequency of the tracking control synchronization signal to follow the resonance frequency of the tracking control scanning unit based on the scanning state of the tracking control scanning unit detected by the detection unit. And
Based on the controlled tracking control synchronization signal, a frequency of the main scanning synchronization signal and the sub-scanning synchronization signal that does not correspond to the tracking control synchronization signal is determined by a ratio of the main scanning frequency to the sub-scanning frequency. And a second synchronization signal control unit that controls to match the set ratio . The optical scanning display according to claim 1, wherein the set ratio is an integer ratio which is relatively prime . The Q value of the first mechanical resonance system is larger than the Q value of the second mechanical resonance system,
The tracking control scanning unit is the main scanning unit,
The optical scanning display according to claim 1 , wherein the tracking control synchronization signal is the main scanning synchronization signal . The main scanning unit performs reciprocal deflection scanning of the light beam so as to emit at a main scanning deflection angle that periodically changes at the main scanning frequency,
The detection unit outputs a signal reflecting the main scanning deflection angle as a main scanning displacement signal,
4. The phase difference control unit according to claim 1, wherein the synchronization signal generation unit includes a phase difference control unit that generates the main scanning synchronization signal so that a phase difference of the main scanning displacement signal with respect to the main scanning drive signal becomes a set value . An optical scanning display according to 1. The synchronization signal generation unit sets a phase of at least one of the main scanning synchronization signal and the sub scanning synchronization signal so that a phase difference between the main scanning synchronization signal and the sub scanning synchronization signal matches a set value. The optical scanning display according to claim 1 , further comprising a phase changing unit to be changed . An optical scanning display that displays an image by two-dimensional scanning of a light beam,
A light source unit that emits the luminous flux at a luminance according to a luminance signal;
A scanning device that reciprocally scans a light beam emitted from the light source unit in a main scanning direction and a sub-scanning direction that intersect each other, and (a) based on a main scanning drive signal, the light beam is converted into a first mechanical resonance. A main scanning unit capable of reciprocating scanning in the main scanning direction using a system, and (b) based on a sub-scanning drive signal, the light beam is transmitted using a second mechanical resonance system, A sub-scanning unit capable of reciprocating scanning in the sub-scanning direction, and performing reciprocating scanning more times in the sub-scanning direction in the main scanning direction for each frame of the image;
The luminance signal is generated on the basis of the video signal so that one frame of the image is divided into three or more fields and scanned and displayed by the scanning device, and is effective in the entire period of each round-trip scanning. The generated luminance signal is transmitted to the light source unit so that effective scanning lines formed by the light source unit actually emitting a light beam during a scanning period do not overlap each other in the three or more fields in the same frame. A luminance signal control unit to output to
A detection unit for detecting a scanning state of the scanning device;
A synchronization signal generator for generating a main scanning synchronization signal and a sub-scanning synchronization signal;
A drive signal generator for generating the main scanning drive signal and the sub-scanning drive signal based on the generated main scanning synchronization signal and sub-scanning synchronization signal, respectively
Including
The main scanning unit performs reciprocal deflection scanning of the light beam so as to be emitted at a main scanning deflection angle that periodically changes at a main scanning frequency,
The sub-scanning unit performs reciprocal deflection scanning of the light beam so as to be emitted at a sub-scanning deflection angle that periodically changes at a sub-scanning frequency,
The detection unit outputs a signal reflecting the main scanning deflection angle and a signal reflecting the sub scanning deflection angle as a main scanning displacement signal and a sub scanning displacement signal, respectively.
The first mechanical resonance system and the second mechanical resonance system each have a Q value that is different from each other in size.
Of the main scanning unit and the sub-scanning unit, the higher Q value of the corresponding mechanical resonance system is a tracking control scanning unit that is controlled to follow the resonance frequency of itself,
Of the main scanning synchronization signal and the sub-scanning synchronization signal, the one corresponding to the scanning control unit for tracking control is a tracking control synchronization signal for performing the tracking control,
The synchronization signal generator is
Based on the scanning state of the follow-up control scanning unit detected by the detection unit, the frequency of the follow-up control synchronization signal is discretely changed by a main scan frequency step size, so that the follow-up control scan unit A first synchronization signal control unit that controls to follow the resonance frequency;
Based on the controlled tracking control synchronization signal, the frequency of the main scanning synchronization signal and the sub-scanning synchronization signal that does not correspond to the tracking control synchronization signal is discretely changed by the sub-scanning frequency step size. A second synchronization signal control unit for controlling the ratio of the main scanning frequency and the sub-scanning frequency to coincide with the set ratio;
Including
The main scanning phase difference of the main scanning displacement signal with respect to the main scanning driving signal is caused by changing the frequency of the main scanning synchronizing signal and the frequency of the sub-scanning synchronizing signal by changing the frequency by the synchronizing signal generator. And a sub-scanning phase difference of the sub-scanning displacement signal with respect to the sub-scanning drive signal varies,
Due to the fluctuation of the main scanning phase difference and the fluctuation of the sub-scanning phase difference, the phase difference between scanning lines of a plurality of scanning lines formed by the scanning device fluctuates,
The main scanning frequency step width is set so as not to exceed the first allowable value so that the fluctuation amount of the inter-scan line phase difference caused by the fluctuation of the main scanning phase difference is within an allowable range,
The sub-scanning frequency step width is set so as not to exceed a second allowable value so that the amount of fluctuation of the inter-scan line phase difference caused by the fluctuation of the sub-scanning phase difference is within the allowable range. Optical scanning display. The main scanning frequency is f _M , the sub-scanning frequency is f _S , the set ratio is n _M : n _S (n _M and n _S are both integers), and the Q value of the first mechanical resonance system is Q _M When the Q value of the second mechanical resonance system is expressed as Q _S , and the coefficient larger than 1 is expressed as γ, the first allowable value is
πf _M / (4γ · Q _M · n _S )
Defined as
The second tolerance value is
πf _S / (4γ · Q _S · n _M )
The optical scanning display according to claim 6 , defined as The optical scanning display according to claim 7 , wherein the coefficient γ has a value of 2 or more and 6 or less . The synchronization signal generation unit sets a phase of at least one of the main scanning synchronization signal and the sub scanning synchronization signal so that a phase difference between the main scanning synchronization signal and the sub scanning synchronization signal matches a set value. 9. The optical scanning display according to claim 6, further comprising a phase changing unit to be changed .

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