Optical scanner and image forming apparatus having the same

An optical scanner is disclosed which includes: a first scanning device having a first mirror portion in which a first reflective surface is formed, the first scanning device scanning in a first direction, light which impinges obliquely on the first reflective surface, by oscillatory rotation of the first mirror portion about a first oscillation axi; and a second scanning device having a second mirror portion in which a second reflective surface is formed so as to be generally in parallel to the first reflective surface in a non-active state of the optical scanner, the second scanning device scanning in a second direction intersecting with respect to the first direction, the light exiting the first reflective surface and then entering obliquely the second reflective surface, by oscillatory rotation of the second mirror portion about a second oscillation axis intersecting with respect to the first oscillation axis. The first oscillation axis is oriented substantially parallel to a direction in which the light enters the first reflective surface, when the optical scanner is viewed in a direction perpendicular to the first and second reflective surfaces.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based on Japanese Patent Applications No. 2003-420487 filed Dec. 18, 2003 and No. 2003-397385 filed Nov. 27, 2003, and International Application No. PCT/JP2004/017379 filed Nov. 24, 2004, the contents of which are incorporated hereinto by reference.

This is a continuation of International Application No. PCT/JP2004/017379 filed Nov. 24, 2004, which was published in Japanese under PCT Article 21 (2).

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to an optical scanner for scanning incident light two-dimensionally by oscillatory rotation of a reflective surface on which light is incident, and an image forming apparatus having such an optical scanner, and more particularly to improvements in construction of the optical scanner.

2. Description of the Related Art

There is already known an optical scanner for scanning light, which is of a type in which incident light is scanned two-dimensionally by oscillatory rotation of a reflective surface on which light is incident (See, for example, FIGS. 7 and 8 of Japanese Patent Application Publication No. 2000-111829).

Such an optical scanner is for use in the fields of, for example, image formation and image reading. In the field of image formation, such an optical scanner is applied to retinal scanning display devices which scan a beam of light on the retina of a viewer for direct presentation of an image onto the retina; projectors; laser printers; devices for use in laser lithography; or other applications. In the field of image reading, such an optical scanner is applied to facsimile machines; copiers; image scanners; bar-code readers; or other applications.

For such an optical scanner, in some cases, there are strong needs of a reduction in size and weight, which are satisfied by an exemplary conventional optical scanner disclosed in the aforementioned Japanese Patent Application Publication No. 2000-111829.

More specifically, in the above exemplary conventional optical scanner, horizontal and vertical scanning devices are disposed in series in a direction in which light travels, in the order set forth above. These horizontal and vertical scanning devices are configured to cause respective mirror portions having respective reflective surfaces formed thereon, to angularly oscillate about corresponding respective oscillation axes, to thereby scan light which has obliquely entered the respective reflective surfaces. The mirror portions of the horizontal and vertical scanning devices are formed on the same substrate, resulting in coplanar disposition of the reflective surfaces of these mirror portions.

BRIEF SUMMARY OF THE INVENTION

In the exemplary conventional optical scanner described above, light enters obliquely the reflective surface of the mirror portion of the horizontal scanning device. For this reason, the entry of light results in the formation of an ellipse-shaped spot on the reflective surface. The major axis of the spot is parallel to the light entry direction, while the minor axis of the same spot is perpendicular to the light entry direction.

In the aforementioned exemplary conventional optical scanner, the oscillation axis of the mirror portion of the horizontal scanning device is perpendicular to the light entry direction. For this reason, there is formed on the mirror portion, the spot to be elongated in a direction (hereinafter, also referred to as “rotation radial direction”) perpendicular to the oscillation axis.

In general, a mirror portion is designed in shape to allow the mirror portion to receive light coming in the mirror portion, without overflow of light. In addition, as a dimension of a mirror portion in the rotation radial direction becomes larger, the moment of inertia of the mirror portion becomes larger, resulting in increasing difficulty in increasing a scan frequency of the mirror portion.

Additionally, in general, there are performed on a scanned plane on which light is scanned, a horizontal scan for horizontally scanning light, and a vertical scan for scanning light in a direction intersecting with respect to a horizontal scan line. On the scanned plane, during per succession of scans, the horizontal scan is repeated frequently, while the vertical scan is repeated less frequently than the horizontal scan. For these reasons, in general, the horizontal scan more strongly requires fast oscillatory rotation of the mirror portion, which is to say, to scan light at a high frequency, than the vertical scan.

Despite of the presence of such needs, in the aforementioned exemplary conventional optical scanner, the oscillation axis of the mirror portion of the horizontal scanning device is disposed perpendicular with respect to the light entry direction, resulting in the presence of an unexpected tendency of the mirror portion to increase in size in its rotation radial direction for allowing the mirror portion to receive light coming in the mirror portion, without overflow of light. For these reasons, this exemplary conventional optical scanner faces difficulties in scanning light at a high scan frequency in the horizontal scanning device having a stronger need to increase its scan frequency than that of the vertical horizontal scanning device.

In view of the circumstances described above, the present invention is made for an object to provide an optical scanner for scanning incident light two-dimensionally by oscillatory rotation of a reflective surface on which light is incident and an image forming apparatus having the optical scanner, with a configuration of the optical scanner which more easily achieves an increase in scan rate of light and downsizing of the optical scanner.

According to a first aspect of the present invention, an optical scanner is provided for scanning incident light two-dimensionally by oscillatory rotation of a reflective surface on which light is incident.

This optical scanner include:

a first scanning device having a first mirror portion in which a first reflective surface is formed, the first scanning device scanning in a first direction, light which impinges obliquely on the first reflective surface, by oscillatory rotation of the first mirror portion about a first oscillation axis; and

a second scanning device having a second mirror portion in which a second reflective surface is formed so as to be generally in parallel to the first reflective surface in a non-active state of the optical scanner, the second scanning device scanning in a second direction intersecting with respect to the first direction, the light exiting the first reflective surface and then entering obliquely the second reflective surface, by oscillatory rotation of the second mirror portion about a second oscillation axis intersecting with respect to the first oscillation axis.

In this optical scanner, the first oscillation axis is oriented substantially parallel to a direction in which the light enters the first reflective surface, when the optical scanner is viewed in a direction perpendicular to the first and second reflective surfaces.

According to a second aspect of the present invention, an image forming apparatus is provided for forming apparatus for forming images by scanning a light beam.

This image forming apparatus includes:

a light source emitting the light beam; and

an optical scanner two-dimensionally scanning the light beam once exiting the light source, to thereby form the images.

The optical scanner includes:

a first scanning device having a first mirror portion in which a first reflective surface is formed, the first scanning device scanning in a first direction, the light beam which impinges obliquely on the first reflective surface, by oscillatory rotation of the first mirror portion about a first oscillation axis; and

a second scanning device having a second mirror portion in which a second reflective surface is formed so as to be generally in parallel to the first reflective surface in a non-active state of the optical scanner, the second scanning device scanning in a second direction intersecting with respect to the first direction, the light beam exiting the first reflective surface and then entering obliquely the second reflective surface, by oscillatory rotation of the second mirror portion about a second oscillation axis intersecting with respect to the first oscillation axis.

In this optical scanner, the first oscillation axis is oriented substantially parallel to a direction in which the light beam enters the first reflective surface, when the optical scanner is viewed in a direction perpendicular to the first and second reflective surfaces.

DETAILED DESCRIPTION OF THE INVENTION

The object mentioned above may be achieved according to any one of the following modes of this invention.

These modes will be stated below so as to be sectioned and numbered, and so as to depend upon the other mode or modes, where appropriate. This is for a better understanding of some of a plurality of technological features and a plurality of combinations thereof disclosed in this description, and does not mean that the scope of these features and combinations is interpreted to be limited to the scope of the following modes of this invention.

That is to say, it should be interpreted that it is allowable to select the technological features which are stated in this description but which are not stated in the following modes, as the technological features of this invention.

Furthermore, stating each one of the modes of the invention in such a dependent form as to depend from the other mode or modes does not exclude the possibility that the technological features set forth in a dependent-form mode become independent of those set forth in the corresponding depended mode or modes and to be removed therefrom. It should be interpreted that the technological features set forth in a dependent-form mode is allowed to become independent, where appropriate.

(1) An optical scanner for scanning incident light two-dimensionally by oscillatory rotation of a reflective surface on which light is incident, the optical scanner comprising:

a first scanning device having a first mirror portion in which a first reflective surface is formed, the first scanning device scanning in a first direction, light which impinges obliquely on the first reflective surface, by oscillatory rotation of the first mirror portion about a first oscillation axis; and

a second scanning device having a second mirror portion in which a second reflective surface is formed so as to be generally in parallel to the first reflective surface in a non-active state of the optical scanner, the second scanning device scanning in a second direction intersecting with respect to the first direction, the light exiting the first reflective surface and then entering obliquely the second reflective surface, by oscillatory rotation of the second mirror portion about a second oscillation axis intersecting with respect to the first oscillation axis,

wherein the first oscillation axis is oriented substantially parallel to a direction in which the light enters the first reflective surface, when the optical scanner is viewed in a direction perpendicular to the first and second reflective surfaces.

In this optical scanner, two scanning devices are disposed in series along a light travel direction, and two reflective surfaces of these two scanning devices are disposed generally parallel to each other in a non-active state of the instant optical scanner.

This optical scanner would therefore make it easier, for example, to miniature this optical scanner in a direction perpendicular to the two reflective surfaces, and to miniature this optical scanner in a direction in which these two reflective surfaces are arrayed.

Further, in this optical scanner, one of the two scanning devices which is located on an upstream one of both sides spaced apart in a light travel direction, i.e., the first scanning device, is adapted, such that, when the instant optical scanner is viewed perpendicularly to a reflective surface of the first scanning device, an oscillation axis of a mirror portion of the first scanning device is substantially parallel to a direction in which light enters the reflective surface.

This optical scanner would therefore prevent the elongation of a spot formed on the reflective surface due to oblique entry of light into the reflective surface, from causing a major axis of the spot to be oriented perpendicularly to the oscillation axis of the reflective surface. As a result, the selection in shape of the mirror portion in conformity with such a spot would not cause a dimension of the mirror portion in the rotation radial direction, to be longer than that of the aforementioned exemplary conventional optical scanner.

This optical scanner would therefore facilitate a reduction in moment of inertia of the mirror portion, and would eventually facilitate an increase in scan frequency of the mirror portion. Consequently, this optical scanner would facilitate co-achievement of both an increase in scan frequency and a reduction in size of the optical scanner.

Although this optical scanner is configured such that the first and second reflective surfaces are disposed generally parallel to each other in an non-active state of this optical scanner, a more specific layout of these two reflective surfaces may be, for example, one in which these two reflective surfaces are arrayed on a substantially single flat plane, one in which these two reflective surfaces are disposed on two opposite flat planes which are substantially parallel to each other and which leave a special clearance therebetween, respectively, with these two reflective surfaces not entirely confronting with each other, etc.

The “first oscillation axis” and “second oscillation axis” set forth in this mode may each be defined, for example, as an axis parallel to a corresponding one of the mirror portions, or as an axis passing through the corresponding mirror portion in parallel thereto.

(2) The optical scanner according to mode (1), wherein the first scanning device further includes a first actuator for angularly oscillating the first mirror portion using a piezoelectric element, and

wherein the second scanning device further includes a second actuator for angularly oscillating the second mirror portion using a piezoelectric element.

In this optical scanner, each of two mirror portions is angularly oscillated by its actuator using a piezoelectric element. This optical scanner would therefore readily allow high-speed oscillation of the mirror portions with a reduced size of the optical scanner, compared with the aforementioned exemplary conventional optical scanner in which its mirror portion or portions are oscillated by electromagnetic or electrostatic force.

(3) The optical scanner according to mode (1) or (2), wherein the light incident on the first reflective surface is parallel light or parallel beam of light.

For the optical scanner according to the previous mode (1) or (2), when the light entering the first reflective surface (hereinafter, referred to simply as “incident light”) is selected as non-parallel light, which is to say, diverging light or converging light, an area of cross section of light within the instant optical scanner tends to become larger than when the incident light is selected as parallel light. Due to this, when the incident light is selected as non-parallel light, an area of a mirror portion which is ideally receive light within this instant optical scanner, without overflow of light tends to increase, compared with when the incident light is selected as parallel light. The tendency invites an increase in size, weight, and moment of inertia, of the mirror portions.

In contrast, the optical scanner according to this mode, the incident light is selected as parallel light or a parallel beam of light. This optical scanner would therefore facilitate a reduction in size, weight, and moment of inertia, of the mirror portions, eventually facilitating an increase in scan rate of light.

(4) The optical scanner according to any one of modes (1) through (3), wherein the first scanning device scans the light at a frequency higher than that of the second scanning device.

This optical scanner would allow a scan frequency of the first scanning device to be higher than that of the second scanning device, by utilizing the technical features resulting from the aforementioned specific layout of the optical scanner according to the previous mode (1).

(5) The optical scanner according to mode (4), wherein the first scanning device performs a horizontal scan allowing the light to be scanned horizontally, and

wherein the second scanning device performs a vertical scan allowing the light to be scanned in a direction intersecting with respect to a horizontal scan line.

As described above, in general, there are performed on a scanned plane on which light is scanned, a horizontal scan for scanning light horizontally, and a vertical scan for scanning light in a direction intersecting with respect to a horizontal scan line. On the scanned plane, during per scan cycle, the horizontal scan is repeated frequently, while the vertical scan is repeated less frequently than the horizontal scan. For these reasons, during such a scanning operation, the horizontal scan more strongly requires an increase in scan rate than the vertical scan.

In this optical scanner, the horizontal scan, which, as described above, more strongly requires an increase in scan rate than the vertical scan, is achieved with the first scanning device, which more easily allows fast scan than the second scanning device.

(6) The optical scanner according to mode (4) or (5), wherein the first and second scanning devices scan the light using respective resonance phenomena of the first and second mirror portions.

This optical scanner would easily allow an increase in scan frequency and stabilization in actual scan frequency, of each scanning device, compared with when any of the “first scanning device” and the “second scanning device” in the optical scanner according to the previous mode (4) or (5) is adapted to scan light without using a resonance phenomenon of a corresponding one of the first and second mirror portions.

The optical scanner according to the previous mode (4) or (5), however, may be practiced in an arrangement in which only one of the “first scanning device” and the “second scanning device” scans light using a resonance phenomenon of a corresponding one of the mirror portions.

(7) The optical scanner according to mode (4) or (5), wherein the first scanning device scans the light using a resonance phenomenon of the first mirror portion, while the second scanning device scans the light without using a resonance phenomenon of the second mirror portion.

This optical scanner would easily allow an increase in scan frequency and stabilization in actual scan frequency, of the first scanning device, compared with when the “first scanning device” in the optical scanner according to the previous mode (4) or (5) is adapted to scan light without using a resonance phenomenon of a corresponding one of the first mirror portion.

(8) The optical scanner according to any one of modes (1) through (7), wherein the second reflective surface has a dimension in a direction of the second oscillation axis, which is equal to or larger than a dimension expressed by
2·d·tan(α/2),

where

α denotes an oscillation angle of the light scanned with the first reflective surface, and

d denotes a distance by which centers of the first and second reflective surfaces are spaced apart from each other, when the optical scanner is viewed in a direction perpendicular to the first and second reflective surfaces.

This optical scanner would allow selection of a dimension of the second reflective surface in a direction of the second oscillation axis, in accordance with the layout of the first and second scanning devices of the optical scanner, in consideration of oscillation angle α of the light scanned with the first reflective surface; and distance d by which centers of the first and second reflective surfaces are spaced apart from each other, when the optical scanner is viewed in a direction perpendicular to the first and second reflective surfaces.

(9) The optical scan according to any one of modes (1) through (8), further comprising a common housing accommodating the first and second scanning devices, wherein the housing includes:

an entrance-side transmissive portion allowing light to enter the first reflective surface from an outside; and

an exit-side transmissive portion allowing light to exit the second reflective surface toward the outside.

In this optical scanner, the first and second scanning devices are accommodated in a housing in common to these scanning devices, and further, there is provided the entrance-side transmissive portion for light entering the first reflective surface, while there is provided the exit-side transmissive portion for light exiting the second reflective surface.

This optical scanner would therefore, because of the housing having its occluding capability, prevent unexpected entry of external light into the first and second scanning devices without passing through the entrance-side transmissive portion or the exit-side transmissive portion, resulting in easier minimization of disturbing-light-caused deterioration of an SN ratio of scanning light produced with the instant optical scanner.

Each of the “entrance-side transmissive portion” and the “exit-side transmissive portion” set forth in this mode may be formed as a hole opening in the housing, or may be formed by filling the opening hole with a light transmissive material such as glass.

(10) The optical scanner according to mode (9), wherein the entrance-side transmissive portion is smaller in size than the exit-side transmissive portion.

In the optical scanner according to the previous mode (9), light enters the first reflective surface along an optical path fixed in position, after passing through the entrance-side transmissive portion, while light exits the second reflective surface along an optical path variable in position, after passing through the exit-side transmissive portion. Consequently, the exit-side transmissive portion is required to be light transmissive over a region larger than that of the entrance-side transmissive portion. On the other hand, for any of these transmissive portions, allowing each transmissive portion to be light transmissive over an undesirably large region is likely to deteriorate an SN ratio of scanning light produced with the instant optical scanner.

In view of the above findings, the optical scanner according to this mode is adapted such that the entrance-side transmissive portion is smaller in size than the exit-side transmissive portion.

(11) The optical scanner according to any one of modes (1) through (10), wherein the first and second reflective surfaces are disposed in series in a direction in which the light travels in the optical scanner, in the order set forth above, so as to be coplanar with each other,

the optical scanner further comprising a third reflective surface reflecting light, once exiting the first reflective surface toward the second reflective surface.

This optical scanner provides one form of the layout of the first and second scanning devices in accordance with the optical scanner according to any one of the previous modes (1) through (10).

It is added that, as an alternative form of the layout of the first and second scanning devices in accordance with the optical scanner according to any one of the previous modes (1) through (10), there exists, for example, a layout in which the first and second reflective surfaces are disposed on respective two opposing flat planes leaving a spatial clearance therebetween, such that light exiting the first reflective surface enters the second reflective surface without passing through a separate reflective surface.

(12) The optical scanner according to mode (11), wherein the first and second mirror portions are formed in a same substrate.

(13) The optical scanner according to mode (11) or (12), wherein the second mirror portion includes a portion overlapping the first scanning device when the optical scanner is viewed in a direction of the second oscillation axis.

This optical scanner would make it easier to arrange the first and second scanning devices closely in a direction of the first oscillation axis, than when the second mirror portion fails to include a portion overlapping the first scanning device. As a result, compactness of this optical scanner in a direction of the first oscillation axis, which is to say, a direction in which the first and second mirror portions are arranged, is more easily achieved than when the second mirror portion fails to include a portion overlapping the first scanning device.

(14) The optical scanner according to any one of modes (1) through (13), wherein the second scanning device further includes a stationary frame, and a connection connecting the second mirror portion with the stationary frame so as to allow the second mirror portion to angularly oscillate about the second oscillation axis, and

wherein the second mirror portion includes a portion overlapping the connection when the optical scanner is viewed in a direction of the first oscillation axis.

This optical scanner would make it easier to arrange the second scanning device and the connection closely in a direction of the oscillation axis of the second mirror portion, than when the second mirror portion fails to include a portion overlapping the connection. As a result, compactness of this optical scanner in a direction of the oscillation axis of the second mirror portion, is more easily achieved than when the second mirror portion fails to include a portion overlapping the connection.

(15) The optical scanner according to any one of modes (1) through (14), further comprising a mirror support supporting the first and second mirror portions, wherein the mirror support includes a mounting portion at which the mirror support is to be detachably mounted on a receiver.

This optical scanner, when replacement of the first and second mirror portions is needed, would allow replacement of the mirror support supporting the first and second mirror portions, while letting the receiver lie. Therefore, for replacement of the first and second mirror portions, a reduction can be provided in the number of optical components which are not required to be replaced but which are unavoidably replaced together with the first and second mirror portions.

(16) The optical scanner according to mode (15), wherein the first scanning device further includes a first actuator for angularly oscillating the first mirror portion using a piezoelectric element, and

wherein the second scanning device further includes a second actuator for angularly oscillating the second mirror portion using a piezoelectric element,

the optical scanner comprising power terminals for supply of electric power to the first and second actuators.

This optical scanner would allow the first and second actuators and a power source for supplying power to the first and second actuator, to be separated using the power terminals provided to the instant optical scanner. Therefore, the first and second mirror portions and the power source can be formed in separate bodies, and this enables replacement of the mirror support without requiring replacement of the power source, when replacement of the first and second mirror portions is needed. Consequently, this optical scanner would avoid useless replacement of the power source which is not needed to be replaced.

(17) The optical scanner according to mode (16), wherein the mirror support is inserted into the receiver for attachment thereto, and

wherein the power terminals are disposed at a leading one of both ends of the mirror support in a direction in which the mirror support is inserted into the receiver.

This optical scanner, as a result of insertion of the instant optical scanner into the receiver, allows the power terminals provided to the instant optical scanner, to be connected with terminals on the side of the power source, and then allows the power source to supply power to the first and second actuators within the instant optical scanner.

(18) The optical scanner according to any one of modes (15) through (17), further comprising a light-transmissive cover opposing the first and second mirror portions.

This optical scanner, owing to the light-transmissive cover, would hold the first and second mirror portions clean.

(19) The optical scanner according to any one of modes (15) through (18), further comprising the receiver.

This optical scanner, because of detachable attachment of the mirror support including the first and second mirror portions, to the receiver, would not require full replacement of the instant optical scanner, but merely require replacement of the mirror support, when replacement of the first and second mirror portions is needed.

(20) The optical scanner according to mode (19), wherein the receiver includes an insert groove allowing the mirror support to be inserted into the receiver, and

wherein the mirror support is inserted into the insert groove for support by the receiver.

This optical scanner, as a result of insertion of the mirror support into the insert groove of the receiver, would allow the mirror support to be easily detachably attached with the receiver.

(21) The optical scanner according to mode (19) or (20), wherein the first scanning device further includes a first actuator for angularly oscillating the first mirror portion using a piezoelectric element,

wherein the second scanning device further includes a second actuator for angularly oscillating the second mirror portion using a piezoelectric element,

wherein the receiver includes first power terminals for supply of electric power to the first and second actuators,

wherein the mirror support includes second power terminals for supply of electric power to the first and second actuators, and

wherein the first and second power terminals are in electrical contact with each other with the mirror support being supported by the receiver.

This optical scanner would allow the first power terminals of the receiver and the second power terminals of the mirror support to be brought into electrical contact with each other, with the mirror support being supported by the receiver. Therefore, in this state, external supply of electrical power is enabled for driving the first and second mirror portions, to the first and second actuators of the mirror support.

(22) The optical scanner according to mode (20) or (21), wherein the receiver is provided with the insert groove in the form of a pair of insert grooves which are engaged with a pair of lateral portions of the mirror support which are opposite to each other in a direction orthogonal to an insertion direction allowing the mirror support to be inserted into the receiver.

This optical scanner, as a result of engagement of the pair of lateral portions of the mirror support, with the insert grooves of the receiver, would allow the insert grooves to support the mirror support to be supported at its pair of lateral portions.

(23) The optical scanner according to any one of modes (19) through (22), wherein the receiver includes a positioner positioning the mirror support with the mirror support being supported by the receiver.

This optical scanner would allow the mirror support to be located in a suitable position using the positioner of the receiver.

(24) A mirror unit including a scanning mirror scanning light, and a mirror support supporting the scanning mirror in a condition allowing the scanning mirror to scan the light, the mirror unit comprising:

a mounting portion which is detachably mounted on a mirror-unit receiver for detachably receiving the mirror unit.

An exemplary conventional apparatus for scanning light is disclosed in Japanese Patent Application Publication No. HEI 6-139387. This conventional apparatus is for optically reading barcodes by scanning light. This conventional apparatus principally includes: a scanner scanning light on a barcode, to thereby optically read the barcode; and a decoder decoding the barcode which has been read by the scanner.

In the above-described conventional apparatus, the scanner and the decoder are formed in separate bodies allowing them to be detachably attached with each other. Due to this, if only one of these scanner and decoder has been damaged, it merely requires replacement of only one of these scanner and decoder which has been damaged, without requiring full replacement of this apparatus.

In this conventional apparatus, however, a power source and many optical components such as a light source, a reflective mirror, etc. are included within the scanner. If full replacement of the scanner is, therefore, unavoidable in spite that there is required replacement of the reflective mirror due to damage thereto, but there is not required replacement of the power source, the light source, etc. because of no damage thereto, the undamaged power source and many optical components such as the light source, etc. are replaced together with the damaged reflective mirror. For this reason, this conventional apparatus suffers from useless replacement of the power source and many optical components such as the light source, etc. which do not require replacement.

To solve the above drawbacks, the mirror unit according to this mode is provided to achieve the object that, when there is required replacement of the scanning mirror, additional optical components which are unavoidably replaced together with the scanning mirror are reduced in number.

The mirror unit according to this mode is a mirror unit including a scanning mirror scanning light, and a mirror support supporting the scanning mirror in a condition allowing the scanning mirror to scan the light, the mirror unit including a mounting portion which is detachably mounted on a mirror-unit receiver for detachably receiving the mirror unit.

This mirror unit, in which the mirror support is separable from the mirror-unit receiver, would therefore allow replacement of only the mirror unit, while letting the mirror-unit receiver lie, when replacement of the scanning mirror is required. Consequently, this mirror unit would allow a reduction in number of optical components which do not require replacement but which are unavoidably replaced together with the scanning mirror, when the scanning mirror requires replacement.

(25) The mirror unit according to mode (24), further comprising:

an actuator actuating the scanning mirror for scan; and

a power-supplied terminal supplying power to the actuator.

This mirror unit allows the actuator and a power source for supply of power to be separable from each other, via the power-supplied terminal provided to the instant mirror unit. Therefore, the scanning mirror, which is capable of being formed in a separate body from the power source, enables, when there is required replacement of the scanning mirror, replacement of only the mirror unit without replacement of the power source requiring no replacement. This mirror unit would therefore avoid useless replacement of the power source requiring no replacement.

(26) The mirror unit according to mode (25), wherein the power-supplied terminal is disposed at a leading one of both ends of the mirror unit in a direction in which the mirror unit is inserted into the mirror-unit receiver.

This mirror unit, as a result of insertion of the instant mirror unit into the mirror-unit receiver, allows the power-supplied terminal provided to the instant mirror unit, to be connected with a terminal on the side of the power source, and then allows the power source to supply power to the actuator within the mirror unit.

(27) The mirror unit according to any one of modes (24) through (26), further comprising a light-transmissive cover opposing the scanning mirror.

This mirror unit, owing to the light-transmissive cover, would hold the scanning mirror clean.

(28) An optical scanner comprising the mirror unit according to any one of modes (24) through (27), further comprising the mirror-unit receiver set forth in any one of modes (24) through (27).

This optical scanner, because of detachable attachment of the mirror support including the scanning mirror, to the mirror-unit receiver, would not require full replacement of the instant optical scanner, but merely require replacement of the mirror unit, when replacement of the scanning mirror is needed.

(29) The optical scanner according to mode (28), wherein the mirror-unit receiver includes an insert groove formed in the mirror-unit receiver, and wherein the mirror unit is inserted into the insert groove for support by the mirror-unit receiver.

This optical scanner, as a result of insertion of the mirror unit into the insert groove of the mirror-unit receiver, would allow the mirror unit to be easily detachably attached with the mirror-unit receiver.

(30) The optical scanner according to mode (29), wherein the mirror-unit receiver is provided with the insert groove in the form of a pair of insert grooves which are engaged with a pair of lateral portions of the mirror unit which are opposite to each other in a direction orthogonal to an insertion direction allowing the mirror unit to be inserted into the insert grooves.

This optical scanner, as a result of engagement of the pair of lateral portions of the mirror unit, with the insert grooves of the mirror-unit receiver, would allow the insert grooves to support the mirror unit to be supported at its pair of lateral portions.

(31) The optical scanner according to any one of modes (28) through (30), wherein the mirror unit includes an actuator actuating the scanning mirror for scan, and a power-supplied terminal for supply of electrical power to the actuator,

wherein the mirror-unit receiver includes a power-supplying terminal for supply of electrical power to the actuator, and

wherein the power-supplying terminal is in electrical contact with the power-supplied terminal, with the mirror unit being supported by the mirror-unit receiver.

This optical scanner would allow the power-supplying terminal of the mirror-unit receiver and the power-supplied terminal of the mirror unit to be brought into electrical contact with each other, with the mirror unit being supported by the mirror-unit receiver. Therefore, in this state, external supply of electrical power is enabled for driving the scanning mirror, to the actuator of the mirror unit.

(32) The optical scanner according to any one of modes (28) through (31), wherein the mirror-unit receiver includes a positioner positioning the mirror unit with the mirror unit being supported by the mirror-unit receiver.

This optical scanner would allow the mirror unit to be located in a suitable position using the positioner of the mirror-unit receiver.

(33) The optical scanner according to mode (32), wherein the positioner includes a first pressing member pressing the mirror unit in a direction orthogonal to a direction allowing the mirror unit to be inserted into the mirror-unit receiver, to thereby position the mirror unit supported by the mirror-unit receiver, with respect to the orthogonal direction.

This optical scanner would allow the mirror unit to be positioned with respect to a direction orthogonal to the insertion direction of the mirror unit, using the first pressing member.

(34) The optical scanner according to mode (32) or (33), wherein the positioner includes a second pressing member pressing the mirror unit in an insertion direction allowing the mirror unit to be inserted into the mirror-unit receiver, to thereby position the mirror unit supported by the mirror-unit receiver, with respect to the insertion direction.

This optical scanner would allow the mirror unit to be positioned with respect to the insertion direction of the mirror unit, using the second pressing member.

(35) The optical scanner according to any one of modes (32) through (34), wherein the positioner includes a third pressing member pressing the mirror unit in a direction in which a reflective surface of the scanning mirror is oriented, to thereby position the mirror unit.

This optical scanner would allow the mirror unit to be positioned with respect to a direction in which the reflective surface of the scanning mirror is oriented (e.g., a direction normal to the reflective mirror).

(36) The optical scanner according to mode (32), wherein the positioner includes a pressing member for locating the mirror unit under pressure, the pressing member being made up of an elastic material absorbing vibration of the mirror unit with the mirror unit being support by the mirror-unit receiver.

This optical scanner allows the mirror unit to be more stably supported, because the vibration of the mirror unit is absorbed by the pressing member for locating the mirror unit under pressure, which is made up of elastic material.

(37) The optical scanner according to any one of modes (28) through (36), further comprising a fixing member fixing the mirror unit to the mirror-unit receiver, with the mirror unit being supported by the mirror-unit receiver.

This optical scanner allows the mirror unit to be fixed to the mirror-unit receiver via the fixing member.

(38) The optical scanner according to mode (37), wherein the fixing member functions also as a second pressing member pressing the mirror unit in an insertion direction allowing the mirror unit to be inserted into the mirror-unit receiver, to thereby position the mirror unit supported by the mirror-unit receiver, with respect to the insertion direction.

This optical scanner allows the mirror unit to be fixed, with the mirror unit being positioned with respect to the insertion direction of the mirror unit, using the fixing member functioning also as a second pressing member.

(39) An image forming apparatus comprising a modulated-light emitter modulating light in accordance with image information, and emitting the modulated light; and an optical scanning device scanning the modulated light for displaying an image, wherein the optical scanning device includes the optical scanner according to any one of modes (28) through (38).

This image forming apparatus provides an apparatus for forming images using the optical scanner according to any one of the previous modes (28) through (38).

(40) An image forming apparatus forming an image by scanning a beam of light, comprising:

a light source emitting the beam of light; and

the optical scanner according to any one of modes (1)through (23), that two-dimensionally scans the beam of light emitted from the light source for forming the image.

This image forming apparatus allows the formation of images using an optical scanner facilitating co-fulfillment of an increase in scan frequency of the beam of light emitted from the light source, and a reduction in size.

(41) The image forming apparatus according to mode (40), wherein the beam of light emerging from the optical scanner enters an image-formed plane on which the image is formed, without passing through any relay optical systems.

This image forming apparatus would make it easier to achieve a reduction in number of components of the instant image-forming-apparatus and simplification in an assembling work, than when the beam of light emerging from the optical scanner enters the image-formed plane through a relay optical system.

(42) The image forming apparatus according to mode (40) or (41), wherein the beam of light emerging from the optical scanner enters a retina of an eye, whereby the image is projected onto the retina.

Several presently preferred embodiments of the invention will be described in more detail by reference to the drawings in which like numerals are used to indicate like elements throughout.

FIG. 1illustrates schematically the exterior of a head-mounted type retinal scanning display device10(hereinafter, referred to as “RSD”) constructed in accordance with a first embodiment of the present invention. This RSD10is adapted to project a beam of light onto a viewer's retina through a pupil of a viewer's eye, and to scan the beam of light on the retina, to thereby directly project an image onto the retina. InFIG. 3, reference numerals12,14and15denote the eye, the pupil, and the retina, respectively. In the present embodiment, the retina15is an example of the “image-formed plane” set forth in the above mode (16).

As illustrated inFIG. 1, the RSD10includes amounted subsystem16mounted on a viewer's head in use, and a light source unit18worn on the viewer, both of which are physically separate from each other. The mounted subsystem16and the light source unit18are optically coupled with each other via a flexible optical fiber20as a light transmissive medium. In use, the light source unit18is, for example, worn on the waist or the back of the viewer, using a fixture such as a belt.

As illustrated inFIG. 1, the mounted subsystem16is of an eyeglasses-type which is held at the viewer's head using the nose and both ears of the viewer, as with conventional eyeglasses. To this end, the mounted subsystem16includes: a frame30supported by the nose of the viewer, located in front of viewer's both eyes12,12; and right- and left-handed temples32,32supported by both ears at both sides of the viewer's head, respectively. The frame30and each temple32,32are foldably hinged with each other.

The RSD10is of a type allowing images to be projected onto the retinas15of both eyes12,12, respectively. To this end, the mounted subsystem16includes separate optical systems for both eyes12,12, respectively. More specifically, the mounted subsystem16includes per each eye12: a scan unit40for scanning a beam of light; and a projection device42for allowing the scanned beam of light to enter a corresponding eye12for projection onto the retina15. The mounted subsystem16is coupled at the scan unit40with the optical fiber20. That is to say, in the present embodiment, the scan unit30and the light source unit18are optically coupled with each other via the optical fiber20.

As illustrated inFIG. 2, the projection device42, in the present embodiment, is of a reflection-type which reflects a beam of light scanned by the scan unit40, into the retina15. More specifically, the projection device42is made up of a semi-transparent mirror similar in shape to each lens of conventional eyeglasses. In the projection device42, its surface facing the viewer is a reflective surface44which, as illustrated inFIG. 3, reflects a beam of light entering from the scan unit40, into the eye12.

The reflective surface44is in the shape of an ellipsoidal surface of revolution formed by rotating a part of an ellipse about a horizontal axis. The reflective surface44has two foci, and, as illustrated inFIG. 2, an exit46of the scan unit40which a beam of light exits is located to coincide with one of these two foci, while the eye12is located to coincide with the other of these two foci, with the mounted subsystem16being mounted on the head.

The projection device42, in addition to being reflective as described above, is transmissive to light which enters the projection device42from the front, for allowing entry of the light into the eye12. Therefore, the viewer is allowed to visually perceive an image delivered from the RSD10, with the image being superimposed on a real scene in front of the viewer, which is seen through the projection device42. However, it is inessential in practicing the present invention to make up the projection device42using a semi-transparent mirror, and the projection device42may be alternatively made up of an optical component which is reflective but is not transmissive.

As is evident from the above explanation, in the present embodiment, sets of the scan unit40and the projection device42are provided for both eyes12,12, respectively, and accordingly, sets of the light source unit18and the optical fiber20are also provided for both eyes12,12, respectively. The light source unit18, however, may be physically in the form of a single light source unit common to both eyes12,12.

FIG. 3illustrates in optical path diagram the light source unit18, optical fiber20, and the scan unit40for a representative one of both eyes12,12.

The light source unit18is constructed so as to include a light source subsystem50, a focusing subsystem52, and a main control circuit54. In order to reproduce any desired color in RGB format, the light source subsystem50includes a laser device60generating a red colored laser beam, a laser device62generating a green colored laser beam, and a laser device64generating a blue colored laser beam. The intensities of the laser beams generated from the laser devices60,62, and64are controlled by the main control circuit54, on a pixel-by-pixel basis, in accordance with an image signal representative of an image to be projected onto the retina15.

In addition, the focusing subsystem52is disposed for focusing three laser beams generated from the three respective laser devices60,62, and64, and is constructed, for example, to include per each laser device60,62,64: collimator lenses70,72, and74for collimating the generated laser beams; and dichroic mirrors80,82, and84. The focused laser beam by the focusing subsystem52is converged by the converging lens90, and the converged laser beam enters the scan unit40through the optical fiber20.

As illustrated inFIG. 3, the scan unit40includes: a collimator lens98for collimating a laser beam exiting the optical fiber20; and an optical scanner100for two-dimensionally scanning a laser beam exiting the collimator lens98, in horizontal and vertical scan directions. In the present embodiment, the collimator lens98allows a laser beam to enter the optical scanner100in parallel light. A laser beam, upon exiting the optical scanner100, enters the reflective surface44of the projection device42without passing through any relay lenses, and is then reflected therefrom into the retina15. The relay lens is an example of the “relay optical system” set forth in the above mode (16).

As illustrated inFIG. 3, with the optical scanner100, a drive circuit110is electrically connected. The drive circuit110drives the optical scanner100in response to a drive signal supplied from the main control circuit54via the optical fiber20or via an electric wire as a separate path from the optical fiber20. The optical scanner100includes a horizontal scanning subsystem120and a vertical scanning subsystem122, both of which are driven by the drive circuit110.

FIG. 4illustrates the optical scanner100in longitudinal cross section. The optical scanner100is constructed with the surface of an oscillating body124being covered with a cover126.

FIG. 5illustrates the oscillating body124in top plan view. The oscillating body124is formed using a base material in the form of a silicon wafer having a thickness of about 100 μm. By etching the base material, first and second oscillating portions130,132are monolithically fabricated on the oscillating body124. The first and second oscillating portions130,132are formed on the oscillating body124in a coplanar array. That is to say, in the present embodiment, the first and second oscillating portions130,132are integrally formed in a planar configuration (configuration in which a plurality of structural elements are disposed in a coplanar relationship).

The first oscillating portion130is excited to vibrate in a resonant condition for its rotary oscillation about a first oscillation axis134for a horizontal scan of a laser beam impinging on the optical scanner100. On the other hand, the second oscillating portion132is excited to vibrate in a resonant condition for rotary oscillation about a second oscillation axis136for a vertical scan of a laser beam exiting the first oscillating portion130.

As illustrated inFIG. 5, on the first and second oscillating portions132, there are formed first and second reflective surfaces140,142, respectively, in a coplanar array in which first and second reflective surfaces140,142are positioned parallel to the surface of the oscillating body124in a non-active state of the optical scanner100. The first reflective surface140is disposed on an upstream side of a direction in which a laser beam travels within the optical scanner100, while the second reflective surface142is disposed on a downstream side. The center of the second reflective surface142is spaced a distance D apart from the center of the first reflective surface140in a direction perpendicular to the second oscillation axis136, which is to say, a direction parallel to the first oscillation axis134. In the optical scanner100, the center of the second reflective surface142is provided on the first oscillation axis134.

In the present embodiment, the first oscillation axis134is positioned with respect to the first oscillating portion130so as to allow the first oscillation axis134to be oriented parallel to a direction of a laser beam impinging on the optical scanner100. On the other hand, the second oscillation axis136is positioned with respect to the second oscillating portion132so as to allow the second oscillation axis136to be oriented perpendicular to a direction of a laser beam impinging on the optical scanner100. As a result, the first and second oscillation axes134,136are positioned orthogonal relative to each other.

As illustrated inFIG. 5, the oscillating body124includes oscillating sections and a non-oscillating section. The oscillating sections are the first and second oscillating portions130,132, and the non-oscillating section is a stationary frame146disposed so as to surround the first and second oscillating portions130,132. The oscillating body124is mounted at the stationary frame146on the cover126.

FIG. 6illustrates the first oscillating portion130in enlarged perspective view, and further illustrates a fragment of the stationary frame146in association with the first oscillating portion130. As illustrated inFIG. 6, the first oscillating portion130includes a first mirror portion150in which the first reflective surface140is formed. From the opposite ends of the first mirror portion150, a pair of beam portions152,152extend in opposite directions to each other. The first oscillating portion130is constructed by coupling the first mirror portion150with the stationary frame146via the pair of beam portions152,152. The pair of beam portions152,152are both disposed on the first oscillation axis134, and are opposed to each other with the first mirror portion150being interposed therebetween.

In each beam portion152, a single first leaf spring154extends from the first mirror portion150, and is bifurcated to form two second leaf springs156,156extending from the first leaf spring154toward the stationary frame146. In each beam portion152, two actuators160,160are attached to the two second leaf springs156,156at their single-sided faces, respectively.

As illustrated inFIG. 7, each actuator160extends along the corresponding second leaf spring156. Each actuator160is in the shape of a sandwich in which a piezoelectric element166is interposed between upper and lower electrodes162,164which coextend in parallel to each actuator160. From the upper and lower electrodes162,164, lead wires170extend, respectively, and are connected with each of terminals172disposed on the stationary frame146.FIG. 7, however, illustrates only the representative ones of the lead wires170and the terminals172for the upper electrode162.

In each thus-structured actuator160, application of a voltage to the piezoelectric element166in a direction perpendicular to its lengthwise direction causes the piezoelectric element166to produce its lengthwise distortion (expansion or contraction), while inducing deflection (flexure) of the corresponding second leaf spring156.

In the present embodiment, voltages opposite in phase are applied to a pair of piezoelectric elements166,166, for exciting the piezoelectric elements166,166to distort in opposite phase, wherein the pair of piezoelectric elements166,166are attached to two of the second leaf springs156,156, respectively, which are located on the same side with respect to the first mirror portion150. As a result, the pair of piezoelectric elements166,166excite the first leaf spring154to produce a moment with a direction causing the first leaf spring154to rotate unidirectionally about the first oscillation axis134.

As illustrated inFIG. 6, the first oscillating portion130employs the total four actuators160, and two of which confront each other with the first mirror portion150being interposed therebetween, are actuated in identical phase. As a result, the four actuators160are each excited to rotate the first mirror portion150in a common direction about the first oscillation axis134.

Although the construction of the first oscillating portion130has been described above, the second oscillating portion132, as illustrated inFIG. 5, is basically common in construction to the first oscillating portion130. That is to say, in the second oscillating portion132, a second mirror portion180in which a second reflective surface142is formed is coupled to the stationary frame146via a pair of beam portions182,182which coextend from the opposite sides of the second mirror portion180, in opposite directions, along the second oscillation axis136. In each beam portion182, a single first leaf spring184extends from the second mirror portion180toward the stationary frame146, and is bifurcated to form two second leaf springs186,186which coextend from the first leaf spring184to the stationary frame146.

For the second oscillating portion132, similarly, in each beam portion182, two actuators190are attached to the two second leaf springs186,186at their single-sided faces, respectively.FIG. 5illustrates in top plan view the second oscillating portion132with the four actuators190being attached thereto. Each actuator190, although not illustrated, is in the shape of a sandwich in which a piezoelectric element is interposed between upper and lower electrodes which coextend along the corresponding second leaf spring186, as with the actuator160. Each actuator190excites the second mirror portion180of the second oscillating portion132to angularly oscillate using the same principle as the principle used for exciting the first mirror portion150of the first oscillating portion130to angularly oscillate.

In the present embodiment, one frame of an image to be projected onto the retina15is formed with a plurality of horizontal scan lines, and a plurality of vertical scan lines which the plurality of horizontal scan lines intersect and which are fewer than the horizontal scan lines. However, not all the scan lines are visualized, and the retrace blanking is performed for the scan lines as desired. For this reason, a horizontal scan is required to scan a laser beam at a higher rate or a higher frequency, while a vertical scan is required to scan a laser beam at a lower rate or a lower frequency. On the other hand, the larger a moment of inertia (=mr2) of each first mirror portion150,180about each oscillation axis134,136, the more easily the scan frequency of each first mirror portion150,180is reduced.

Therefore, in the present embodiment, as illustrated inFIG. 5, the second mirror portion180of the second oscillating portion132for vertical scan is dimensioned to be larger in a direction (rotation radial direction) perpendicular to the oscillation axis134,136than the first mirror portion150of the first oscillating portion130for horizontal scan.

As illustrated inFIG. 5, in the present embodiment, the second mirror portion180of the second oscillating portion132for vertical scan is dimensioned to be larger also in the direction of the oscillation axis134,136than the first mirror portion150of the first oscillating portion130for horizontal scan. The establishment of a dimension L of the second oscillating portion132in the direction of the second oscillation axis136will be described in greater detail below.

FIG. 4illustrates the cover126in sectional side view. The cover126is constructed such that a vertical wall portion202extends from a circumferential edge of a plate portion200.FIG. 8illustrates the cover126in top plan view. The cover126includes an entrance-side transmissive portion204allowing a laser beam to enter from the outside, while the cover126includes an exit-side transmissive portion206allowing a laser beam to exit toward the outside. In the present embodiment, the entrance-side and exit-side transmissive portions204,206are each in the form of a through hole not being filled inside. The entrance-side transmissive portion204is formed in the plate portion200of the cover126at its one end, while the exit-side transmissive portion206is formed in the plate portion200and the vertical wall portion202of the cover126at its remaining end.

In the present embodiment, a laser beam impinges obliquely and acutely on the first oscillating portion130through the entrance-side transmissive portion204, while a laser beam exits obliquely and acutely the second oscillating portion132through the exit-side transmissive portion206.

As illustrated inFIGS. 4 and 8, a stationary mirror210is attached to a back face of the plate portion200which faces the first and second oscillating portion130,132. The stationary mirror210is fixedly attached at a fixed position. As illustrated inFIG. 4, the stationary mirror210is disposed generally at an intermediate point in a path extending from the first mirror portion150to the second mirror portion180. The stationary mirror210, by the use of its third reflective surface212, reflects a laser beam exiting the first mirror portion150at an acute angle therewith, toward the second mirror portion180at an acute angle therewith.

FIG. 9is illustrates in top plan view an optical path along which a laser beam travels from an entry event into to an exit event from the optical scanner100. The laser beam, upon entry as parallel light, is scanned by the first mirror portion150in a horizontal direction (in an up-and-down direction as viewed inFIG. 9). The scanned laser beam is reflected from the stationary mirror210, and then enters the second mirror portion180. The entering laser beam is scanned by the second mirror portion180in a vertical direction (in a plane perpendicular to the sheet ofFIG. 9).

Where α denotes an oscillation angle of a laser beam scanned with the first mirror portion150, and d denotes a distance by which centers of the first and second reflective surfaces140,142of the first and second mirror portions150,180are spaced apart from each other, the dimension L of the second reflective surface142in the direction of the second oscillation axis136is set to a value equal to or larger than a dimension expressed by
2·d·tan(α/2)

As illustrated inFIG. 9, in the present embodiment, an optical path of a laser beam to be passed through the entrance-side transmissive portion204remains unchanged in position during a scanning operation by the optical scanner100, while an optical path of a laser beam to be passed through the exit-side transmissive portion206changes in position during a scanning operation by the optical scanner10, so as to draw a sector-shaped figure.

With emphasis on the differences in optical path between the entrance-side and exit-side transmissive portions204,206, in the present embodiment, the entrance-side transmissive portion204is made to be smaller in size than the exit-side transmissive portion206, and additionally, the entrance-side and exit-side transmissive portions204,206are each designed, with variations in manufactures and changes in temperature, etc., in mind, so as to have a minimum size allowing for a practically-required margin but not allowing for any additional margins. As a result, entry of disturbing light and dust into the optical scanner100through the entrance-side and exit-side transmissive portions204,206is restricted.

As is evident from the above description, in the present embodiment, the first oscillating portion130, a portion of the cover126pertinent to the first oscillating portion130, the four actuators160pertinent to the first oscillating portion130, and a portion of the drive circuit110which actuates the actuators160corporate to constitute the horizontal scanning subsystem120. Further, the second oscillating portion132, a portion of the cover126pertinent to the second oscillating portion132, the four actuators190pertinent to the second oscillating portion132, and a portion of the drive circuit110which actuates the actuators190corporate to constitute the vertical scanning subsystem122.

As described above, in the present embodiment, the horizontal scanning subsystem120, which is one of the horizontal and vertical scanning subsystems120,122, and which is disposed on an upstream side of a travel direction of a laser beam, is adapted such that its first oscillation axis134is positioned exactly parallel to an entry direction in which a laser beam enters the first reflective surface140, when the optical scanner100is viewed perpendicularly to the first reflective surface140of the horizontal scanning subsystem120. For the first oscillation axis134, being exactly parallel to the entry direction is not essential, and being substantially parallel is adequate.

Therefore, the present embodiment, even if a spot of a laser beam formed on the first reflective surface140is deformed to be elongated due to oblique entry of the laser beam into the first reflective surface140, would prevent a major axis of the spot from being oriented perpendicular with respect to the first oscillation axis134of the reflective surface140. As a result, the selection of the shape of the first mirror portion150so as to fit such a spot would not require the dimension of the first mirror portion150in the rotation radial direction to be larger than that of the aforementioned exemplary conventional technique.

Accordingly, the present embodiment makes it easier to reduce a moment of inertia of the first mirror portion150, eventually facilitating an increase in scan frequency of the first mirror portion150. As a result, the present embodiment facilitates co-achievement of an increase in scan frequency and a reduction in size.

As is evident from the above description, in the present embodiment, the horizontal scanning subsystem120constitutes an example of the “first scanning device” set forth in the above mode (1), the vertical scanning subsystem122constitutes an example of the “second scanning device” set forth in the same mode, and the laser beam constitutes an example of the “light” set forth in the same mode.

Further, in the present embodiment, the four actuators160, which actuate the first oscillating portion130, each constitute an example of the “first actuator” set forth in the above mode (2), the four actuators190, which actuate the second oscillating portion132, each constitute an example of the “second actuator” set forth in the same mode, and the cover126constitutes an example of the “housing” set forth in the above mode (9).

Still further, in the present embodiment, the first and second reflective surfaces140,142constitutes an example of the “first and second reflective surfaces” set forth in the above mode (11), and the third reflective surface212of the stationary mirror210constitutes an example of the “third reflective mirror” set forth in the same mode.

Additionally, in the present embodiment, the light source unit18constitutes an example of the “light source” set forth in the above mode (40), the scan unit40constitutes an example of the “optical scanner” set forth in the same mode, and the laser beam constitutes an example of the “light beam” set forth in the same mode.

It is added that, in the present embodiment, although the first and second mirror portions150,180are both designed to exploit their resonance phenomena for laser beam scan, the present invention may be alternatively practiced in an arrangement in which the first mirror portion150exploits its resonance phenomenon for laser beam scan, while the second mirror portion180does not exploit its resonance phenomena for laser beam scan.

Next, there will be described a second embodiment of the present invention. The present embodiment, however, is in common in many elements to the first embodiment, while is different only in elements pertinent to an optical scanner from the first embodiment, and therefore, only the different elements of the present embodiment will be described in greater detail below, while the common elements of the present embodiment will be omitted in detailed description by reference using the identical reference numerals or names to those in the first embodiment.

FIG. 10illustrates in exploded perspective view an optical scanner230constructed according to the present embodiment. The optical scanner230includes a cover232and an oscillating body234.

The cover232, which is in common in construction to the cover126in the first embodiment, is composed of the plate portion200and the vertical wall portion202, and further the cover232is provided with the entrance-side transmissive portion204and the exit-side transmissive portion206formed in the cover232.

In addition, the oscillating body234includes a horizontal scanning subsystem236and a vertical scanning subsystem238.

The horizontal scanning subsystem236, which is in common in construction to the horizontal scanning subsystem120in the first embodiment, as illustrated inFIG. 11, includes the first oscillating portion130which is excited to angularly oscillate about the first oscillation axis134. The first oscillating portion130includes the first mirror portion150in which the first reflective surface140is formed. The first oscillation axis134is positioned to be oriented parallel to a laser beam impinging on the optical scanner230.

The first mirror portion150is coupled with a stationary frame240, so as to allow an angular oscillation of the first mirror portion150, via the pair of beam portions152,152each constructed to include the one first leaf spring154and the two second leaf springs156,156disposed in parallel to each other. To the four actuators160, the four second leaf springs156of the horizontal scanning subsystem236are attached, respectively. The horizontal scanning subsystem236scans a laser beam in the horizontal direction at a higher rate, based on the principle identical to that of the horizontal scanning subsystem120in the first embodiment.

In the present embodiment, the horizontal scanning subsystem236is composed of: the first oscillating portion130; a portion of the stationary frame240which surrounds the first oscillating portion130; and the four actuators160.

On the other hand, the vertical scanning subsystem238, although is common in basic construction to the vertical scanning subsystem122, differs particularly in the shape of a mirror portion from the vertical scanning subsystem122.

As illustrated inFIG. 11, the vertical scanning subsystem238includes a second oscillating portion250excited to angularly oscillate about the second oscillation axis136which is oriented perpendicular to the first oscillation axis134. The second oscillating portion250includes a second mirror portion254on which a second reflective surface252is formed. The second mirror portion254, differently from the second mirror portion180in the first embodiment, has a non-symmetrical shape about the second oscillation axis136.

More specifically, in the second mirror portion254, a cutout258is formed on one of both sides of the second mirror portion254with respect to the second oscillation axis136, which is proximal to the horizontal scanning subsystem236. Into the cutout258, there is partially inserted one of both ends of the horizontal scanning subsystem236in the direction of the first oscillation axis134, which is proximal to the vertical scanning subsystem238. As a result, the second mirror portion254includes overlapping portions260, which overlap the horizontal scanning subsystem236as viewed in a direction of the second oscillation axis136, and which are disposed at two positions opposing each other with the horizontal scanning subsystem236being interposed therebetween, respectively.

On the other hand, designing both the horizontal scanning subsystem236and the vertical scanning subsystem238to scan laser beams in a resonant mode, and reducing the scanning frequency of the vertical scanning subsystem238to be lower than that of the horizontal scanning subsystem236, require, in general, increasing a moment of inertia of the second mirror portion254to be larger than that of the first mirror portion150. In addition, the larger a dimension of the second mirror portion254in its rotation radial direction, i.e., its width dimension, the larger a moment of inertia of the second mirror portion254.

Further, in the present embodiment, as described above, the second mirror portion254is made to overlap the horizontal scanning subsystem236in the direction of the second oscillation axis136, and it is facilitated to array the horizontal and vertical scanning subsystems236,238so as to be closely spaced apart from each other in the array direction. That is, a longitudinal dimension of the optical scanner230(dimension in a longitudinal direction parallel to the first oscillation axis134) is allowed to be smaller than a simple sum of maximum lengths of the horizontal and vertical scanning subsystems236,238.

Therefore, the present embodiment would make it easier to make the longitudinal dimension of the optical scanner230smaller for the scanning frequency of the vertical scanning subsystem238and for the width of the second mirror portion254. That is, the present embodiment would facilitate the miniaturization of the optical scanner230in its longitudinal direction.

As illustrated inFIG. 11, a pair of beam portions264,264extend in opposite directions from opposite lateral edges of the second mirror portion254spaced apart in the direction of the second oscillation axis136. The pair of beam portions264,264connect the second mirror portion254with the stationary frame240so as to allow the second mirror portion254to angularly oscillate about the second oscillation axis136.

Each beam portion264includes: a first leaf spring270extending along the second oscillation axis136; and a second leaf spring272extending parallel to the first leaf spring270at a position offset from the first leaf spring270. The first leaf spring270couples the second mirror portion254and the stationary frame240with each other. On the other hand, the second leaf spring272couples with the stationary frame240, the first leaf spring270at an extension274which radially extends outwardly of the first leaf spring270at its halfway point.

In each beam portion264, an actuator280is attached to the second leaf spring272. The actuator280is in common in construction to the actuator160in the horizontal scanning subsystem236. In the present embodiment, the pair of actuators280,280which are attached to the pair of second leaf springs272,272, offset from the second oscillation axis136, respectively, are driven in identical phase. Due to this, the second leaf spring272is deflected at its connection with the extension274, in a direction perpendicular to the surface of the second leaf spring272. The deflection is converted by the extension274into a rotational moment about the second oscillation axis136, whereby the second mirror portion254is excited to angularly oscillate about the second oscillation axis136.

As described above, in order to reduce the scanning frequency of the vertical scanning subsystem238to be lower than that of the horizontal scanning subsystem236, to increase a moment of inertia of the second mirror portion254is desirable. To this end, to increase a dimension of the second mirror portion254in the rotation radial direction (transverse dimension) is effective, and to increase a dimension of the second mirror portion254in the direction of the second oscillation axis136(longitudinal dimension) is also effective.

On the other hand, the larger the longitudinal dimension of the second mirror portion254, the stronger a tendency that the width (transverse dimension) of the optical scanner230increases.

In this regard, in the present embodiment, as illustrated inFIG. 11, the second mirror portion254includes overlapping portions284,284overlapping the respective beam portions264as viewed in a direction perpendicular to the second oscillation axis136. That is, the width of the optical scanner230is allowed to be smaller than a simple sum of a maximum longitudinal dimension of the second mirror portion254and a total of longitudinal dimensions of the pair of beam portions264.

Therefore, the present embodiment would make it easier to make the transverse dimension of the optical scanner230smaller for the longitudinal dimension of the second mirror portion254, resulting in facilitation in miniaturizing the optical scanner230in its lateral direction.

As is evident from the above description, in the present embodiment, the overlapping portions260constitute an example of the “portion overlapping the first scanning device” set forth in the above mode (13), the beam portions264constitute an example of the “connection” set forth in the above mode (14), and the overlapping portions284constitute an example of the “portion overlapping the connection” set forth in the same mode.

Next, there will be described a third embodiment of the present invention will be described. The present embodiment, however, is in common in many elements to the second embodiment, while is different only in elements pertinent to an optical scanner from the second embodiment, and therefore, only the different elements of the present embodiment will be described in greater detail below, while the common elements of the present embodiment will be omitted in detailed description by reference using the identical reference numerals or names to those in the second embodiment.

Referring toFIG. 12, there is illustrated in exploded perspective view an optical scanner292in a head-mounted retinal scanning display device290(hereinafter, abbreviated as “RSD”) constructed in accordance with the present embodiment. The RSD290, except for its components of the optical scanner292, is in common in construction to the RSD10in accordance with the second embodiment.

As illustrated inFIG. 12, the optical scanner292in the present embodiment includes the cover232and the oscillating body234, similarly with the second embodiment. The optical scanner292, differently from the second embodiment, further includes a receiver294.

The receiver294, when the cover232and the oscillating body234are assembled, is detachably attached to an assembly300of the cover232and the oscillating body234. As illustrated inFIG. 12, the receiver294in the shape of a flattened-box extends in its length direction. The receiver294includes: (a) an opening302and a bottom portion304opposing each other in the length direction of the receiver294; and (b) a pair of lateral portions306,306coextending between the opening302and the bottom portion304in the length direction of the receiver294.

As illustrated inFIG. 12, the pair of lateral portions306,306are opposed to each other with a space therebetween, in a width direction of the receiver294. The lateral portions306,306have at their opposing faces insert grooves308,308, respectively, which coextend along the respective lateral portions306,306. Each insert groove308,308is formed by means of an upper plate portion310,310and a lower plate portion312,312opposing each other in a thickness direction of the receiver294, both of which belong to a corresponding one of the lateral portions306,306; and an end plate portion314,314extending in the length direction of the receiver294. The end plate portions314,314extend in the length direction of the receiver294so as to interconnect the upper plate portions310,310and the lower plate portions312,312at their distal edges from a center of the receiver294in its width direction. That is, the pair of insert grooves308,308are formed at the pair of lateral portions306,306of the receiver294, in opposition to each other in the width direction of the receiver294.

As illustrated inFIG. 12, the receiver294includes an opening320formed at an upper face of the receiver294. With the assembly300of the cover232and the oscillating body234being inserted into the receiver294, the entrance-side transmissive portion204and the exit-side transmissive portion206are exposed at the opening320of the receiver294.

The assembly300of the cover232and the oscillating body234to the receiver294, when needed to be attached to the receiver294, is inserted into the receiver294through its opening302. The assembly300is brought into engagement with the pair of insert grooves308,308of the receiver294, and, while being guided by the pair of insert grooves308,308, is moved toward a bottom portion304of the receiver294. The assembly300is inserted into the receiver294to a depth allowing leading ends324,326of the assembly300in the insertion direction, to abut on the bottom portion304of the receiver294.

As illustrated inFIG. 12, the oscillating body234in the shape of a flattened box extends in its length direction, and a plurality of second power terminals TA01–TA12are provided to the leading end324of both ends of the oscillating body234in the insertion direction of the assembly300. The second power terminals TA01–TA12are provided as many as a totality of the electrodes162,164of the actuators160for actuating the first mirror portion150and the electrodes162,164of the actuators280for actuating the second mirror portion254, with which the oscillating body234is provided. In association with the second power terminals TA01–TA12, first power terminals TB01–TB12are disposed at the bottom portion304of the receiver294, as many as the second power terminals TA01–TA12.

It is adapted that, when the oscillating body234is brought into abutment at its leading end324on the bottom portion304of the receiver294as a result of insertion thereinto, the plurality of second power terminals TA01–TA12of the oscillating body234and the plurality of first power terminals TB01–TB12of the receiver294are brought into electrical contact with each other in one-to-one correspondence. This enables electric power output from an external power source not illustrated, to be supplied to the individual electrodes162,164of the oscillating body234, by passing through the first power terminals TB01–TB12and the second power terminals TA01–TA12, in the description order.

The optical scanner292is provided with a positioning configuration for positioning the assembly300, with the assembly300of the cover232and the oscillating body234being attached to the receiver294as a result of insertion thereinto. The positioning configuration includes: a first positioner for positioning the assembly300with respect to the width direction of the receiver294; a second positioner for positioning the assembly300with respect to the thickness direction of the receiver294; a third positioner for positioning the assembly300with respect to the length direction of the receiver294.

FIG. 13is a cross section taken on line X—X inFIG. 12. The above-mentioned first positioner includes a first pressing member330disposed between the assembly300and the receiver294, at one of the pair of insert grooves308,308, which oppose each other in the width direction of the receiver294, along a direction in which the one insert groove308extends, which is to say, the length direction of the receiver294. The first pressing member330, made up of an elastic material, elastically presses the assembly300onto the receiver294in a direction in which one of the pair of insert grooves308,308faces the other, which is to say, the width direction of the receiver294(the direction indicated by the arrow labeled as “F1” inFIG. 13). The pressing allows the assembly300to be positioned with respect to the width direction of the receiver294.

In addition, the third positioner positions the assembly300with respect to the length direction of the receiver294, by pressing elastically the assembly300onto the receiver294in the insertion direction of the assembly300, which is to say, the length direction of the receiver294. The third positioner includes a protrusion-to-recess fit-into portion (not illustrated), which has a structure common to that in which a protrusion550and a recess552illustrated inFIG. 21are fitted into each other. The protrusion-to-recess fit-into portion, which will be described by reference toFIG. 21for convenience purposes, includes the protrusion550disposed at one of the assembly300and the receiver294, and the recess552disposed at the other. In this protrusion-to-recess fit-into portion, the protrusion550is elastically fitted into the recess552.

The protrusion550and the recess552each have an inclined surface (including a surface inclined at 90°) inclined relative to the length direction of the receiver294. As a result of their inclined surfaces being elastically pressed against each other in the length direction of the receiver294, with the protrusion550and the recess552being fitted into each other, there is produced a force to press the assembly300onto the receiver294in its length direction.

As illustrated inFIG. 13, the aforementioned second positioner includes second pressing members340,340disposed between the assembly300and the receiver294, at the pair of insert grooves308,308, which oppose each other in the width direction of the receiver294, along a direction in which the pair of insert grooves308,308extend, which is to say, the length direction of the receiver294. The second pressing members340,340, made up of an elastic material, elastically press the assembly300onto the receiver294in a direction in which the lower plate portions312,312, which are ones of the upper plate portions310,310and the lower plate portions312,312opposing each other in the thickness direction of the receiver294for each lateral portions306,306, faces the upper plate portions310,310, which are the other ones, which is to say, the thickness direction of the receiver294(the direction indicated by the arrow labeled as “F3” inFIG. 13). The pressing allows the assembly300to be positioned with respect to the thickness direction of the receiver294.

Next, there will be described a fourth embodiment of the present invention.FIGS. 14–22illustrate a mirror unit400constructed in accordance with the present embodiment. As illustrated inFIG. 14, in the mirror unit400, a scanning mirror402and an actuator404are disposed in a mirror support406, the actuator400being adapted to actuate the scanning mirror402for its angular oscillation in directions indicated by the arrows labeled as “α” and “β” in this Figure.

The mirror unit400is optics angularly oscillating the scanning mirror402in a manner described above, to thereby reflect incoming light N impinging on the scanning mirror402, into a direction depending on the angular position of the scanning mirror402, as scanning light H. As illustrated inFIG. 15, the mirror unit400is configured so as to be detachably attached to a mirror-unit receiver408.

FIG. 16illustrates the mirror unit400when attached with the mirror-unit receiver408(when in use). In the present embodiment, an optical scanning device410is constructed by attaching the mirror unit400to the mirror-unit receiver408. This optical scanning device410controls an angular oscillation of the scanning mirror402, to thereby scan the scanning light H emerging from the scanning mirror402on a screen which is an example of an image-formed plane. As a result, an image is displayed on the screen.

Returning next toFIG. 14, there will be described a specific construction of the mirror support406of the mirror unit400.

The mirror support406includes a casing420and a base plate422attached to the casing420. On the base plate422, the aforementioned scanning mirror402and the actuator404are disposed. The casing420is formed, for example, such that the casing420is generally in the form of a rectangular solid, and has a base-plate-attached portion424in a recess formed at one of faces of the casing420.

The base plate422is disposed in the base-plate-attached portion424. The base-plate-attached portion424includes at its bottom plane, a plurality of relay terminals430–444. Covering an upper opening of the base-plate-attached portion424with a transparent cover which is transmissive to light, as not illustrated, enables an inner space of the base-plate-attached portion424to be sealed for preventing introduction thereinto of foreign matter such as dirt and dust from the outside.

As illustrated inFIG. 15, although the mirror unit400is detachably attached to the mirror-unit receiver408, there exists as one of modes in which the mirror unit400is detachably attached to the mirror-unit receiver408, a mode in which the mirror unit400is attached to the mirror-unit receiver408so as to be insertable into and extractable from the mirror-unit receiver408. The mirror unit400will be described below by way of an example of this mode.

In this mode, a catch450is disposed in the casing420of the mirror unit400at its rearmost one of both ends in the insertion direction (which is also referred to as a trailing end, and is an upper end inFIG. 15), on an upper one of both faces of the rearmost end in the thickness direction, the upper face being located on the same side as the scanning mirror402. The catch450is provided for facilitating a worker to catch the mirror unit400in an attempt to insert or extract the mirror unit400, to thereby achieve an enhanced workability.

As illustrated inFIG. 15, the pair of lateral portions306,306of the casing420which are spaced apart in its width direction are mounting portions452,454which are insertable into the mirror-unit receiver408. In addition, a plurality of power-supplied terminals456–470are disposed in a leading one of both ends of the casing420in the insertion direction, on its leading end face opposing the mirror-unit receiver408. These power-supplied terminals456–470are in electrical contact with the plurality of relay terminals430–444(seeFIG. 14) via wirings, etc., as not illustrated.

Next, there will be described the scanning mirror402and the actuator404by reference toFIGS. 17 and 18.

FIG. 17illustrates in perspective view the exterior of the scanning mirror402disposed on the base plate422and the exterior of the actuator404actuating the scanning mirror402. As illustrated inFIG. 17, the scanning mirror402is plate-shaped, and a reflective surface is formed on an upper surface of the scanning mirror402illustrated in this Figure.

A pair of rotation-axis portions480,482coextend in opposite directions from the scanning mirror402through its rotation centerline. Each rotation-axis portion480,482is bifurcated halfway when going away from the scanning mirror402. As a result, there are coupled with one of the rotation-axis portions480, two connections484,486coextending in parallel, with the aforementioned rotation centerline being interposed therebetween, and there are coupled with the other of the rotation-axis portions482, two connections488,490coextending in parallel, with the aforementioned rotation centerline being interposed therebetween.

On each connection484,486,488,490, as illustrated inFIG. 18illustrating the connection484as a representative connection, at its upper face in this Figure, there is disposed a piezoelectric element492which is an example of an element for converting electric field or voltage into displacement or distortion.

As illustrated inFIG. 18, each actuator404attached to each connection484,486,488,490, includes: the piezoelectric element492; and a lower electrode493L (lower electrodes493aL,493bL,493cL,493dL corresponding to the connections484,486,488,490, respectively) and an upper electrode493U (upper electrodes493aU,493bU,493cU,493dU corresponding to the connections484,486,488,490, respectively) which are laid on the piezoelectric element492at its both faces, respectively, with the piezoelectric element492being sandwiched between the electrodes493L and493U. In the present embodiment, the piezoelectric element492, which is of a unimorph type, is attached to a single side of the connection484which is an elastic material, via the lower electrode493aL.

Now, an operation of each actuator404will be described by way of an example of the piezoelectric element492sandwiched between the lower electrode493aL and the upper electrode493aU each corresponding to the connection484. As a voltage impressed across the lower electrode493aL and the upper electrode493aU varies in direction, the piezoelectric element492and the connection484repeat alternately a shifting from a neutral state depicted inFIG. 18(a) to an upwardly curved state depicted inFIG. 18(b), and a shifting from the neutral state depicted inFIG. 18(a) to an downwardly curved state depicted inFIG. 18(c). As a result, a direction in which the connection484is deflected varies repeatedly between in upward and downward directions.

Accordingly, the rotation-axis portions480,482rotate in a direction of the arrow indicated inFIG. 17and the scanning mirror402also angularly rotates in the same direction, once the piezoelectric element492sandwiched between the lower electrode493aL and the upper electrode493aU in the connection484illustrated inFIG. 17, and the piezoelectric element492sandwiched between the lower electrode493cL and the upper electrode493cU in the connection488, are deflected to upwardly convex as illustrated inFIG. 18(b), and the piezoelectric element492sandwiched between the lower electrode493bL and the upper electrode493bU in the connection486, and the piezoelectric element492sandwiched between the lower electrode493dL and the upper electrode493dU in the connection490, are deflected to downwardly convex as illustrated inFIG. 18(c).

Therefore, controlling voltages applied between the lower electrodes493aL,493bL,493cL,493dL, and the upper electrodes493aU,493bU,493cU,493dL, for controlling the angular oscillation of the scanning mirror402, would allow the reflection for deflection of the incoming light N into the scanning light H, resulting in achievement of the capability of scanning light.

As illustrated inFIG. 17, the lower and upper electrodes493aL,493aU corresponding to the connection484are electrically connected with a lower-electrode terminal494and an upper-electrode terminal502, respectively. Similarly, the lower and upper electrodes493bL,493bU corresponding to the connection486are electrically connected with a lower-electrode terminal496and an upper-electrode terminal504, respectively. Still similarly, the lower and upper electrodes493cL,493cU corresponding to the connection488are electrically connected with a lower-electrode terminal498and an upper-electrode terminal506, respectively. Yet still similarly, the lower and upper electrodes493dL,493dU corresponding to the connection490are electrically connected with a lower-electrode terminal500and an upper-electrode terminal508, respectively.

As illustrated inFIG. 14, the lower-electrode terminal494, the upper-electrode terminal502, the upper electrode terminal504, and the lower-electrode terminal498are electrically connected with the plurality of relay terminals430,432,434,436disposed on the casing420, respectively, via bonding wires W. Similarly, the lower-electrode terminal498, the upper-electrode terminal506, the upper electrode terminal508, and the lower-electrode terminal500are electrically connected with the plurality of relay terminals438,440,442,444disposed on the casing420, respectively, via bonding wires W.

As illustrated inFIG. 15, the mirror-unit receiver408, which detachably supports the mirror unit400, may be made to have a configuration allowing the mirror-unit receiver408to receive the mirror unit400in an insertable and extractable manner, as descried above.

By reference toFIGS. 15 and 16, there will be described a more specific construction of the mirror-unit receiver408receiving the mirror unit400in an insertable and extractable manner.

As illustrated inFIG. 15, the mirror-unit receiver408includes: a leading-end receiving section520receiving the leading end of the mirror unit400; and a pair of lateral-portion receiving sections522,524disposed upright on the leading-end receiving section520and receiving the pair of mounting portions452,454composing the mirror unit400.

There are formed in the pair of lateral-portion receiving sections522,524, a pair of insert grooves526,528into and from which there are insertable and extractable, the pair of mounting portions452,454which are included in the casing420of the mirror unit400. The pair of insert grooves526,528are closed at their leading end sides in the insertion direction with the leading-end receiving section520, and are opened at their trailing end sides to function as insertion openings530,532allowing the pair of mounting portions452,454to be inserted.

As illustrated inFIG. 16, the pair of lateral-portion receiving sections522,524of the mirror-unit receiver408are designed to have a dimension in the insertion direction, i.e., length smaller than that of the mirror unit400, so as to allow the catch450of the mirror unit400to be exposed from the mirror-unit receiver408, with the mirror unit400being received by the mirror-unit receiver408.

As illustrated inFIG. 15, at the leading-end receiving section520of the mirror-unit receiver408, a plurality of power-supplying terminals P1–P8are disposed. The power-supplying terminals P1–P8are in electrical contact with the plurality of power-supplied terminals456–470of the mirror unit400, respectively, with the mirror unit400being inserted into the mirror-unit receiver408, as illustrated inFIG. 16.

Electric power supplied from an external power source not illustrated is delivered to the lower electrodes493aL,493bL,493cL, and493dL, and the upper electrodes493aU,493bU,493cU, and493dL, via the plurality of power-supplying terminals P1–P8, the plurality of power-supplied terminals456–470, the plurality of relay terminals430–444, the lower-electrode terminals494–500, and the upper-electrode terminals502–508, in the description order.

As illustrated inFIG. 16, the present embodiment includes a positioning configuration for positioning the mirror unit400, with the mirror unit400being mounted on the mirror-unit receiver408.

Referring now toFIGS. 19–22, the positioning configuration will be described. The positioning configuration includes a first positioner, a second positioner, and a third positioner. Referring first toFIG. 19, the first positioner will be described.

FIG. 19is a cross section taken on line A—A inFIG. 15. The aforementioned first positioner includes a first pressing member540disposed between the insert groove526and the mirror unit400, the insert groove526being one of the insert grooves526,528in the mirror-unit receiver408. The first pressing member540is made up of an elastic material. The first pressing member540is disposed to extend along an entire length of a groove bottom540of the insert groove526.

The first pressing member540elastically presses the mirror unit400onto the other insert groove528, with the mirror unit400being inserted into the insert grooves526,528. The elasticity of the first pressing member540causes the mirror unit400to be pressed at one (hereinafter, referred to as “opposite lateral-face”) of lateral faces of the casing420which is opposite to the other lateral-face with which the first pressing member540is engaged, onto an groove bottom544of the other insert groove528. The pressing allows the mirror unit400to be positioned with respect to the width direction of the mirror unit400, which is to say, a direction which is perpendicular with respect to the insertion direction of the mirror unit400, and which is in parallel to the reflective surface of the scanning mirror402(the direction indicated by the arrow labeled as “F1” inFIG. 19).

The opposite lateral-face of the casing420of the mirror unit400and the groove bottom544of the insert groove528onto which the opposite lateral-face is pressed are each in the shape of a flat surface so as to allow a surface-to-surface contact therebetween. This allows the mirror unit400to be positioned with a further improved precision.

As illustrated inFIG. 20which is a sectional view taken on line B—B inFIG. 19, the groove bottom544of the insert groove528and the leading-end receiving section520are formed to form a predetermined angle (e.g., 90 degrees). This allows the mirror unit400to be positioned with a still further improved precision. The direction of the arrow labeled as “INS” inFIG. 20indicates the insertion direction of the mirror unit400.

That is to say, the aforementioned first positioner is constructed with the first pressing member540depicted inFIG. 19, the flat-shaped opposite lateral-face of the casing420of the mirror unit400, and the flat-shaped groove bottom544of the insert groove528.

Referring next toFIG. 21, the aforementioned second positioner will be described. This second positioner is for positioning the mirror unit400by press in the insert direction. The direction of the arrow labeled as “INS” inFIG. 21indicates the insertion direction of the mirror unit400.

In order for this second positioner to be constructed, as illustrated inFIG. 21, the protrusion550is formed in the mirror unit400, while the recess552into which the protrusion550can be fitted is formed in the mirror-unit receiver408. A portion of the mirror-unit receiver408at which the recess552is formed is smaller in flexural rigidity than a portion of the mirror unit400at which the protrusion550is formed, prone to be localized elastic deformation.

The protrusion550and the recess552each have an inclined surface (including a surface inclined at 90°) inclined relative to the length direction of the mirror-unit receiver408. As a result of their inclined surfaces being elastically pressed against each other in the length direction of the mirror-unit receiver408, with the protrusion550and the recess552being fitted into each other, there is produced a force to press the mirror unit400onto the mirror-unit receiver408in its length direction. The protrusion550is elastically fitted into the recess552functioning as a second pressing member.

The protrusion550and the recess552are configured to have a relative positional relation to achieve that, at a point after the mirror unit400is inserted into the insert grooves526,528, and just before the leading end face of the mirror unit400is brought into abutment with the leading-end receiving section520of the mirror-unit receiver408, as illustrated inFIG. 16, the protrusion550starts being fitted into the recess550, as illustrated inFIG. 21, and that, in the abutment state, the protrusion550is pressed onto the recess552under pressure.

In the present embodiment using the thus-configured second positioner, once the protrusion550, as a result of inserting the mirror unit400into the insert grooves526,528of the mirror-unit receiver408, has been fitted into the recess552, an elastic force generated between the protrusion550and the recess552is transmitted to the mirror unit400. Due to the transmitted elastic force, the mirror unit400is pressed in the insertion direction. As a result, the mirror unit400is fixed in position with respect to the insertion direction of the mirror unit400, with the leading end face of the mirror unit400being in surface contact with the leading-end receiving section520of the mirror-unit receiver408.

Although the construction of the second positioner of a protrusion-to-recess fit-into type allowing the mirror unit400to be positioned with respect to the insertion direction, by the use of elastic press, by way of an example of the construction in which the protrusion550is disposed in the mirror unit400, while the recess552is disposed in the mirror-unit receiver408, the present invention may be practiced by employing the construction in which the protrusion550is disposed in the mirror-unit receiver408, while the recess552is disposed in the mirror unit400.

Referring next toFIG. 19, the aforementioned third positioner will be described.

As illustrated inFIG. 19, this third positioner includes third pressing members560provided within the insert grooves526,528. The third pressing members560are disposed between the mirror unit400and the mirror-unit receiver408. This third pressing members560, located behind the mirror unit400with respect to the reflection direction of the scanning mirror402of the mirror unit400, elastically press the mirror unit400onto the mirror-unit receiver408, in a direction in which the reflective surface of the scanning mirror402is facing (the direction indicated by the arrow labeled as “F3” inFIG. 19).

Due to the pressing, the mirror unit400is pressed at an upper face of the casing420, onto groove walls562,564of the insert grooves526,528, and is positioned with respect to a direction perpendicular with respect to the insertion direction of the mirror unit400, and perpendicular with respect to the reflective surface of the scanning mirror402. Forming frontal faces of the mounting portions452,454of the casing420of the mirror unit400and the groove walls562,564of the inserts grooves526,528so as to allow surface contact with each other, would allow the mirror unit400to be positioned with a still improved precision.

As illustrated inFIG. 22which is a sectional view taken on line C—C inFIG. 19, when the mirror-unit receiver408is formed such that, per each insert groove526,528, pairs of groove walls562,562,564,564and the leading-end receiving section520form a predetermined angle (e.g., 90 degrees), the mirror unit400is positioned with a still further improved precision. The direction of the arrow labeled as “INS” inFIG. 20indicates the insertion direction of the mirror unit400.

That is to say, the aforementioned third positioner is constructed with the third pressing member560depicted inFIG. 19, the frontal faces of the mounting portions452,454of the casing420, and the groove walls562,564of the insert grooves526,528.

Next, there will be described the procedure for assembling the mirror unit400and the mirror-unit receiver408constructed in the above manner.

As illustrated inFIG. 15, first, a worker moves the mirror unit400toward the mirror-unit receiver408, and inserts the mounting portions452,454of the mirror unit400into the insert grooves526,528of the mirror-unit receiver408, from the insertion openings530,532. Subsequently, the worker, as illustrated inFIG. 16, inserts the mirror unit400into the mirror-unit receiver408, until the leading end face of the mirror unit400is brought into abutment with the leading-end receiving section520of the mirror-unit receiver408. In the abutment state, the mirror unit400is fixed in position.

More specifically, as illustrated inFIG. 21, as a result of the protrusion550being fitted into the recess552, the mirror unit400is positioned with respect to the insertion direction. In addition, as a result of the first pressing member540depicted inFIG. 19pressing the mirror unit400onto the groove bottom544of the insert groove528, the mirror unit400is positioned with respect the width direction (the direction also referred to as a lateral direction, and indicated by “F1” in this Figure). Moreover, as a result of the third pressing members560,560depicted inFIG. 19pressing the mirror unit400upwardly (the direction also referred to as the thickness direction, and indicated by “F3” in this Figure), and pressing the upper face of the mirror unit400onto the groove walls562,564of the insert grooves526,528, the mirror unit400is allowed to be positioned with respect to the thickness direction.

Upon completion of the positioning of the mirror unit400in the above manner, the plurality of power-supplied terminals456–470of the mirror unit400are brought into electrical contact with the plurality of power-supplying terminals P1–P8, respectively, and as a result, supply of electric power from the external power source not illustrated to the actuator404of the scanning mirror402is enabled.

As illustrated inFIG. 14, the scanning mirror402reflects the incident light N emerging from a light source not illustrated, and outputs the reflected light as the scanning light H. Once the actuator404actuates the scanning mirror402for its angular oscillation, using electric power supplied from the external power source, there is performed the deflection of the scanning light H by the scanning mirror402, which is to say, a scan. Scanning the aforementioned screen with the scanning light H allows an image to be displayed on the screen.

Next, there will be described the procedure for a worker to conduct replacement of the optical scanning device410, in a hypothetical case in which the mirror unit400is needed to be replaced due to damaged at its component, for example, the scanning mirror402, the actuator404, etc.

In this case, in the attached state illustrated inFIG. 16, the worker first attempts to pull out the mirror unit400from the mirror-unit receiver408, by catching the mirror unit400at its catch450. When a force exerted on the mirror unit400by the worker becomes large to some extent, the recess552illustrated inFIG. 21elastically deforms in a direction away from the protrusion550, and the recess552gets over the protrusion550and disengages from the protrusion550. As a result, the mirror unit400is extracted from the mirror-unit receiver408, whereby the mirror unit400is separated from the mirror-unit receiver408.

Thereafter, the worker inserts a new mirror unit400into the mirror-unit receiver408to thereby assemble the mirror unit400and the mirror-unit receiver408with each other.

As is evident from the above explanation, in the optical scanning device410according to the present embodiment, the mirror unit400is configured to be attachable to and detachable from the mirror-unit receiver408, and therefore, for example, where the scanning mirror402and the actuator404thereof are needed to be replaced due to damaged, only the mirror unit400can be replaced, without replacement of the mirror-unit receiver408having no need for replacement.

Incidentally, the optical scanning device410, when used as, for example, a component of an image display apparatus, is essentially required, for properly displaying images, to hold the mirror unit400in a suitable installation position on its optical path. In addition, for example, replacement of the mirror unit400with a new mirror unit400may possibly cause the new mirror unit400to be installed in a position non-coincident with a regular position on its optical path. For these reasons, replacement of the mirror unit400would involve a need for realignment of the installation position of the new mirror unit400.

In the present embodiment, however, when there is a need for replacement of the mirror unit400, the mirror-unit receiver408is held fixed to the instant image display apparatus, without any changes in its installation position, and therefore, a mere inserting action of a new mirror unit400into that mirror-unit receiver408would assure that the new mirror unit400is installed in a regular position on its optical path.

The present embodiment, accordingly, would allow the alignment of the installation position of the mirror unit400resulting from its replacement, to be fully omitted, or, if not, would not require such alignment to be conducted as carefully as conventional techniques, whereby, at any rate, a worker's load would be eliminated.

Next, there will be described a fifth embodiment of the present invention.

FIG. 23illustrates in perspective view an image display apparatus570constructed according to the present embodiment, in which light is scanned using the optical scanning device410constructed according to the fourth embodiment. The image display apparatus570is constructed to include: a modulated-light emitter572for emitting modulated light S; a horizontal scanning subsystem (an example of a primary scanning device)574for scanning the emitted modulated light S horizontally; a vertical scanning subsystem (an example of a secondary scanning device)576for scanning the modulated light S vertically; a collimator lens578; a reflective mirror580; and relay optical systems582,584.

The horizontal and vertical scanning subsystems574,576are configured using the optical scanning device410constructed according to the fourth embodiment. More specifically, in the horizontal scanning subsystem574, the scanning mirror402of the optical scanning device410is angularly oscillated for horizontally scanning the modulated light S. In addition, in the vertical scanning subsystem576, the scanning mirror402of the optical scanning device410is angularly oscillated for vertically scanning the modulated light S.

In the image display apparatus570, the modulated-light emitter572modulates laser light in response to an external signal, to thereby emit the modulated light S. The modulated light S emitted from the modulated-light emitter572, after being converged by the collimator lens578, is reflected from the reflective mirror580into the horizontal scanning subsystem574.

The modulated light S impinging on the horizontal scanning subsystem574undergoes a horizontal scan at the horizontal scanning subsystem574, and then exits there. The modulated light S horizontally scanned at the horizontal scanning subsystem574enters the vertical scanning subsystem576via the relay optical systems582,584. The modulated light S impinging on the vertical scanning subsystem576undergoes a vertical scan at the vertical scanning subsystem576, and then exits there. With the exiting modulated light S, the aforementioned screen590is scanned, to thereby display an image on the screen590.

When the image display apparatus570according to the present embodiment is used, provided that the mirror-unit receiver408has been installed in a regular position on the optical path, mere attachment, needed for replacement of the mirror unit400, of a new mirror unit400to the mirror-unit receiver408would automatically regulate the installation position of the new mirror unit400on the optical path.

It is added that the image display apparatus570, although is of a projector type in which an image is projected onto the screen590spatially disposed, to thereby display the image on the screen590, may be alternatively of a retinal scanning type in which the modulated light S is projected directly onto the retina of the viewer and is scanned on the retina, to thereby display an image on the retina. In this case, this image display apparatus570functions as a retinal scanning display device similarly with the first, second, and third embodiments.

It is further added that the image display apparatus570illustrated inFIG. 23, although employs the optical scanning device410according to the fourth embodiment for forming a visible image, may employ it for forming an invisible image, or for reading a visible image. An example of the image display apparatus570which uses the optical scanning device410for forming an invisible image is a laser printer using the optical scanning device410for forming an electrostatic latent image on a photosensitive material.