Patent Description:
An image forming apparatus that draws an image on a screen or the like by irradiating a mirror device configured with micro electro mechanical systems (MEMS) with light has been known. The mirror device includes a movable mirror that swings about at least one axis.

The mirror device is accommodated in a package in which a vacuum or a negative pressure is created in order to decrease air resistance of the swinging movable mirror. In this case, laser light is incident on the mirror device from an outside through a glass window provided in the package.

In a case where the mirror device is accommodated in the package, a part of the laser light incident on the glass window may be reflected on a surface of the glass window, and this reflected light may be incident on a drawing region of an image for the mirror device as stray light. In this case, in a case where the stray light is incident on the drawing region, an unnecessary bright point occurs in the image.

In <NPL>, <https://briefs. techconnect. org/wp-content/volumes/TCB2016v4/pdf/<NUM>. pdf>, guiding the reflected light outside the drawing region by inclining the glass window is suggested because while providing an anti-reflection film on the surface of the glass window is considered in order to suppress the reflected light, it is difficult to completely suppress the reflected light with the anti-reflection film. <CIT> discloses a MEMS micro-mirror including a single package; a first mirror and second mirror, wherein at least one of the mirrors is configured to oscillate along an oscillation axis. <CIT> discloses an assembly body for micromirror chips that partly encloses an internal cavity, the assembly body including at least two sides oriented away from one another. <CIT> discloses an optical scanning apparatus which is not limited in the disposition of a scanning device, can reduce the adherence of dust to each member of the scanning device, and is enhanced in the reliability of the scanning device. <CIT> discloses a housing for receiving a vibrating device comprising housing walls by which a housing interior is at least partially enclosed and at least one window opening in at least one of the housing walls. <CIT> discloses a scanning device for scanning a two-dimensional area, the scanning device comprising a light source, a first deflection mirror and a second deflection mirror. <CIT> discloses an arrangement having micro-mirrors lying next to one another and carved out from a common substrate wafer on a wafer plane. A base wafer is connected with the substrate wafer, and a partial transparent lid (<NUM>) is connected with the substrate wafer. <CIT> discloses a micromechanical component with a light window; a mirror element, which is adjustable relative to the light window from a first position about at least one axis of rotation in at least one second position; and an optical sensor having a detection surface which is designed to determine a light intensity on the detection surface and to provide a corresponding sensor signal.

However, in a case where the glass window is inclined as disclosed in <NPL>>, a problem arises in that a package size is increased because a thickness of the package is increased. In addition, a problem arises in that a manufacturing cost is increased because of the increase in package size.

An object of the disclosed technology is to provide a light scanning device and an image forming apparatus that can be provided in a small size at a decreased manufacturing cost without causing stray light to be incident on a drawing region.

In order to accomplish the above object, a light scanning device according to claim <NUM> is provided. A light scanning device according to an aspect of the present disclosure is a light scanning device comprising a mirror device that includes a movable mirror which swings about at least one axis, and a package that has at least two or more light transmission surfaces not constituting the same plane and accommodates the mirror device, in which out of the two or more light transmission surfaces of the package, one light transmission surface is a light receiving surface for receiving an incidence ray on the movable mirror from an outside, and the other light transmission surface is a light extraction surface for extracting light reflected by the movable mirror to the outside.

It is preferable that a vacuum or a negative pressure is created inside the package.

It is preferable that a signal input terminal for receiving a driving signal for driving the movable mirror from the outside is provided in the package.

It is preferable that an optical element that guides light incident from the light receiving surface to the movable mirror by deflecting the light is provided inside the package.

The light receiving surface and the light extraction surface are configured with two light transmission surfaces that are not parallel.

An imaging apparatus and a signal output terminal for extracting an imaging signal output from the imaging apparatus to the outside are provided inside the package, and the light extraction surface guides a part of the light reflected by the movable mirror to the imaging apparatus by reflecting the part of the light.

An image forming apparatus according to another aspect of the present disclosure is an image forming apparatus comprising a light scanning device including a mirror device that includes a movable mirror which swings about at least one axis, and a package that has at least two or more light transmission surfaces not constituting the same plane and accommodates the mirror device, and a light emitting device that emits light, in which out of the two or more light transmission surfaces of the package, one light transmission surface is a light receiving surface for receiving an incidence ray on the movable mirror from an outside, and the other light transmission surface is a light extraction surface for extracting light reflected by the movable mirror to the outside, and the light emitted from the light emitting device is incident on the movable mirror through the light receiving surface.

According to the disclosed technology, a light scanning device and an image forming apparatus that can be provided in a small size at a decreased manufacturing cost without causing stray light to be incident on a drawing region can be provided.

Hereinafter, embodiments according to the disclosed technology will be described in detail with reference to the drawings. As an example, in each of the following embodiments, a form of applying the disclosed technology to an image forming apparatus that forms an image on a projection surface by scanning laser light using a Lissajous method will be described.

<FIG> illustrates an example of a configuration of an image forming apparatus <NUM> of the present embodiment which is an embodiment not according to the claimed subject-matter, but useful for understanding the invention. As illustrated in <FIG>, the image forming apparatus <NUM> of the present embodiment comprises a control device <NUM>, a MEMS driver <NUM>, a light emitting device <NUM>, a multiplexing optical system <NUM>, a collimator <NUM>, and a light scanning device <NUM>. The light scanning device <NUM> is configured with a MEMS mirror <NUM> and a package <NUM> that accommodates the MEMS mirror <NUM>. The MEMS mirror <NUM> is an example of a "mirror device" according to the embodiment of the disclosed technology.

The light emitting device <NUM> includes a laser driver <NUM> and a laser light source <NUM>. The laser driver <NUM> of the present embodiment drives the laser light source <NUM> based on an intensity modulation signal supplied from the control device <NUM> and causes laser light for forming an image to be output from the laser light source <NUM>. For example, the laser light source <NUM> outputs the laser light of three colors of red (R), green (G), and blue (B). The laser light is an example of "light" according to the embodiment of the disclosed technology.

The laser light output from the laser light source <NUM> is multiplexed by the multiplexing optical system <NUM>. Then, the MEMS mirror <NUM> in the package <NUM> is irradiated with the multiplexed laser light through the collimator <NUM>. The laser light condensed in the MEMS mirror <NUM> is reflected toward a projection surface <NUM> by the MEMS mirror <NUM>. For example, the projection surface <NUM> is a screen for projecting the image, or a retina of an eye of a person. That is, the image forming apparatus <NUM> of the present embodiment is used for a projector, augmented reality (AR) glasses, and the like.

In the present embodiment, the projection surface <NUM> is not limited to a surface of an actual object such as the screen and includes an imaginary plane in a space.

The MEMS driver <NUM> drives the MEMS mirror <NUM> under control of the control device <NUM>. In the MEMS mirror <NUM>, a mirror portion <NUM> (refer to <FIG>) that reflects laser light L swings about each of two axes orthogonal to each other as a central axis. In the present embodiment, the laser light L is scanned in a state of drawing a Lissajous curve on the projection surface <NUM> by the swing of the mirror portion <NUM> based on a driving signal. The Lissajous curve is a curve that is decided by a swing frequency about a first axis, a swing frequency about a second axis, and a phase difference therebetween. The mirror portion <NUM> is an example of a "movable mirror" according to the embodiment of the disclosed technology.

The control device <NUM> of the present embodiment includes a field programmable gate array (FPGA) 20A and a memory 20B. For example, the memory 20B is a volatile memory and stores various information such as an image signal representing the image projected to the projection surface <NUM>. For example, the memory 20B stores the image signal input from an outside of the image forming apparatus <NUM>.

<FIG> illustrates an example of a configuration of the MEMS mirror <NUM>. The MEMS mirror <NUM> includes the mirror portion <NUM>, a first support portion <NUM>, a first movable frame <NUM>, a second support portion <NUM>, a second movable frame <NUM>, a connecting portion <NUM>, and a fixed frame <NUM>.

The mirror portion <NUM> has a reflecting surface 40A on which an incidence ray is reflected. For example, the reflecting surface 40A is formed with a thin metal film of gold (Au), aluminum (Al), silver (Ag), or a silver alloy. For example, a shape of the reflecting surface 40A is a circular shape.

The first support portion <NUM> is arranged outside the mirror portion <NUM> at each of positions that face with a second axis a<NUM> interposed therebetween. The first support portions <NUM> are connected to the mirror portion <NUM> on a first axis a<NUM> and support the mirror portion <NUM> in a swingable manner about the first axis a<NUM>.

The first movable frame <NUM> is a rectangular frame surrounding the mirror portion <NUM> and is connected to the mirror portion <NUM> through the first support portions <NUM> on the first axis a<NUM>. A piezoelectric element <NUM> is formed on the first movable frame <NUM> at each of positions that face with the first axis a<NUM> interposed therebetween. In such a manner, a pair of first actuators <NUM> are configured by forming two piezoelectric elements <NUM> on the first movable frame <NUM>.

The pair of first actuators <NUM> are arranged at positions that face with the first axis a<NUM> interposed therebetween. The first actuators <NUM> cause the mirror portion <NUM> to swing about the first axis a<NUM> by applying rotational torque about the first axis a<NUM> to the mirror portion <NUM>.

The second support portion <NUM> is arranged outside the first movable frame <NUM> at each of positions that face with the first axis a<NUM> interposed therebetween. The second support portions <NUM> are connected to the first movable frame <NUM> on the second axis a<NUM> and support the first movable frame <NUM> and the mirror portion <NUM> in a swingable manner about the second axis a<NUM>. In the present embodiment, the second support portions <NUM> are torsion bars that stretch along the second axis a<NUM>.

The second movable frame <NUM> is a rectangular frame surrounding the first movable frame <NUM> and is connected to the first movable frame <NUM> through the second support portions <NUM> on the second axis a<NUM>. The piezoelectric element <NUM> is formed on the second movable frame <NUM> at each of positions that face with the second axis a<NUM> interposed therebetween. In such a manner, a pair of second actuators <NUM> are configured by forming two piezoelectric elements <NUM> on the second movable frame <NUM>.

The pair of second actuators <NUM> are arranged at positions that face with the second axis a<NUM> interposed therebetween. The second actuators <NUM> cause the mirror portion <NUM> to swing about the second axis a<NUM> by applying rotational torque about the second axis a<NUM> to the mirror portion <NUM> and the first movable frame <NUM>.

The connecting portion <NUM> is arranged outside the second movable frame <NUM> at each of positions that face with the first axis a<NUM> interposed therebetween. The connecting portions <NUM> are connected to the second movable frame <NUM> on the second axis a<NUM>.

The fixed frame <NUM> is a rectangular frame surrounding the second movable frame <NUM> and is connected to the second movable frame <NUM> through the connecting portions <NUM> on the second axis a<NUM>.

In the present embodiment, the first axis a<NUM> and the second axis a<NUM> are orthogonal to each other. In the following description, a direction parallel to the first axis a<NUM> will be referred to as an X direction, a direction parallel to the second axis a<NUM> will be referred to as a Y direction, and a direction orthogonal to the first axis a<NUM> and the second axis a<NUM> will be referred to as a Z direction.

<FIG> illustrates an example of an exterior configuration of the light scanning device <NUM>. The package <NUM> has an almost rectangular parallelepiped shape. For example, the package <NUM> is configured with a substrate <NUM> having a flat plate shape and a lid member <NUM> having a box shape. For example, the substrate <NUM> and the lid member <NUM> are formed of glass having light transmittance. The package <NUM> is configured by joining the lid member <NUM> to the substrate <NUM>. The MEMS mirror <NUM> is accommodated inside the package <NUM>.

In addition, a vacuum or a negative pressure is created inside the package <NUM>. In such a manner, by creating a vacuum or a negative pressure inside the package <NUM>, an energy loss at a time of the swing of the mirror portion <NUM> is reduced, and a large deflection angle can be implemented with a low driving voltage. The negative pressure means that a pressure inside the package <NUM> is lower than a pressure (that is, atmospheric pressure) outside the package <NUM>.

The lid member <NUM> has four light transmission surfaces <NUM>. The four light transmission surfaces <NUM> are configured with one upper surface and three side surfaces. In the present embodiment, the light transmission surface <NUM> as one side surface among the four light transmission surfaces <NUM> functions as a "light receiving surface" for receiving the incidence ray on the mirror portion <NUM> from the outside. In addition, the light transmission surface <NUM> as one upper surface among the four light transmission surfaces <NUM> functions as a "light extraction surface" for extracting the light reflected by the mirror portion <NUM> to the outside. That is, in the present embodiment, the light receiving surface and the light extraction surface are configured with two light transmission surfaces <NUM> that are not parallel.

The laser light L emitted from the light emitting device <NUM> is transmitted through a light receiving region <NUM> on the light receiving surface and is incident into the package <NUM>. The laser light L incident into the package <NUM> is incident on the mirror portion <NUM> of the MEMS mirror <NUM>. The laser light L reflected by the mirror portion <NUM> is transmitted through a light extraction region <NUM> on the light extraction surface and is extracted outside the package <NUM>. The laser light L transmitted through the light extraction region <NUM> is incident on the projection surface <NUM> (refer to <FIG>).

<FIG> illustrates an example of a cross-sectional structure of the light scanning device <NUM>. As illustrated in <FIG>, the MEMS mirror <NUM> is fixed to the substrate <NUM> through a support member <NUM>. For example, the support member <NUM> has a triangular prism shape and has an inclined surface <NUM>. The MEMS mirror <NUM> is joined to the inclined surface <NUM>. That is, a surface of the mirror portion <NUM> is not parallel to any of the light receiving surface and the light extraction surface in a standstill state.

A signal input terminal <NUM> for receiving a driving signal for driving the mirror portion <NUM> from the outside is provided in the substrate <NUM>. For example, the signal input terminal <NUM> is electrically connected to the MEMS mirror <NUM> through a bonding wire <NUM>. The MEMS driver <NUM> (refer to <FIG>) inputs the driving signal into the MEMS mirror <NUM> through the signal input terminal <NUM>. For example, the signal input terminal <NUM> is individually provided in each of the pair of first actuators <NUM> and the pair of second actuators <NUM>. Driving signals having different frequencies are provided to the pair of first actuators <NUM> and the pair of second actuators <NUM>.

As illustrated in <FIG>, the laser light L emitted from the light emitting device <NUM> is partially reflected on the light receiving surface and becomes stray light LS. Since the light extraction surface is configured with the light transmission surface <NUM> that does not constitute the same plane with the light transmission surface <NUM> constituting the light receiving surface, the stray light LS is not incident on a drawing region (that is, the projection surface <NUM>).

In the light scanning device <NUM> of the present embodiment, inclining a glass window in order to guide the stray light LS outside the drawing region as in the related art is not necessary. Thus, a thickness of the package <NUM> is not increased, and a package size can be decreased. Thus, according to the disclosed technology, the light scanning device <NUM> that can be provided in a small size at a decreased manufacturing cost without causing the stray light to be incident on the drawing region is implemented.

In the embodiment, while the entire package <NUM> is formed of a light transmission material such as glass, the package <NUM> may be partially formed of a light shielding member. For example, a part other than the light receiving region <NUM> and the light extraction region <NUM> in the package <NUM> may be formed of a light shielding member.

Next, a second embodiment which is an embodiment not according to the claimed subject-matter, but useful for understanding the invention will be described. While the laser light is received into the package <NUM> from one side surface of the lid member <NUM> in the first embodiment, the laser light is received into the package <NUM> from the substrate <NUM> in the second embodiment.

<FIG> illustrates an example of a cross-sectional structure of the light scanning device <NUM> according to the second embodiment. The substrate <NUM> transmits light, and a surface of the substrate <NUM> is the light transmission surface <NUM>. In the embodiment, the light transmission surface <NUM> of the substrate <NUM> functions as the "light receiving surface" for receiving the incidence ray on the mirror portion <NUM> from the outside. The laser light L emitted from the light emitting device <NUM> is transmitted through the light receiving region <NUM> of the substrate <NUM> and is incident into the package <NUM>. The laser light L incident into the package <NUM> is incident on an inner surface side of the lid member <NUM>.

An optical element <NUM> is provided on the inner surface side of the lid member <NUM> at a position on which the laser light L is incident. The optical element <NUM> guides the laser light L incident from the light receiving region <NUM> to the mirror portion <NUM> of the MEMS mirror <NUM> by deflecting the laser light L. In the present embodiment, the optical element <NUM> is a reflecting film formed by sputtering or a vapor deposition method. The optical element <NUM> deflects the laser light L by specular reflection so that the laser light L is guided to the mirror portion <NUM>.

In the present embodiment, the MEMS mirror <NUM> is directly fixed to the substrate <NUM> without using the support member <NUM> (refer to <FIG>). That is, in the present embodiment, the MEMS mirror <NUM> is not inclined with respect to the substrate <NUM>. The laser light L reflected by the mirror portion <NUM> is transmitted through the light extraction region <NUM> on the upper surface of the lid member <NUM> and is extracted outside the package <NUM> in the same manner as in the above embodiment.

As described above, in the second embodiment, the laser light L is received from a rear surface side of the package <NUM>. Thus, the stray light LS caused by partial reflection of the laser light L on the light receiving surface is not incident on the drawing region. Accordingly, even in the second embodiment, since inclining the glass window in order to guide the stray light LS outside the drawing region as in the related art is not necessary, the light scanning device <NUM> that can be provided in a small size at a decreased manufacturing cost is implemented. In addition, since it is not necessary to incline the MEMS mirror <NUM> with respect to the substrate <NUM>, the thickness of the package <NUM> can be further decreased.

The optical element <NUM> is not limited to a reflecting film and may be an optical element such as a grating or a hologram. A grating or a hologram can emit the laser light L at an emission angle different from an incidence angle. Thus, using an optical element such as a grating or a hologram as the optical element <NUM> improves a degree of design freedom of a position and the like for arranging the optical element <NUM>.

Next, a third embodiment which is an embodiment according to the claimed subject-matter will be described. In the third embodiment, an imaging apparatus is provided inside the package <NUM>. The imaging apparatus is used for correcting a light emission timing of the laser light L by the light emitting device <NUM>.

<FIG> illustrates an example of a cross-sectional structure of the light scanning device <NUM> according to the third embodiment. In the present embodiment, an imaging apparatus <NUM> is attached to the substrate <NUM> inside the package <NUM>. The imaging apparatus <NUM> is provided on an optical path of the laser light L reflected on the light extraction region <NUM> out of the laser light L reflected by the mirror portion <NUM>. A signal output terminal <NUM> for extracting an imaging signal output from the imaging apparatus <NUM> to the outside is provided in the substrate <NUM>. Other configurations of the light scanning device <NUM> according to the present embodiment are the same as the configurations of the light scanning device <NUM> according to the first embodiment.

The imaging apparatus <NUM> generates a captured image IP by imaging the laser light L reflected on the light extraction region <NUM> and outputs the generated captured image IP to the control device <NUM> (refer to <FIG>). The imaging apparatus <NUM> is configured with an image sensor such as a charge coupled device (CCD) image sensor or a complementary metal oxide semiconductor (CMOS) image sensor. In addition, the imaging apparatus <NUM> may be configured with a position sensitive detector (PSD). The captured image IP is used for correcting timings of a first reference signal and a second reference signal, described later. The captured image IP is an example of "imaging information" according to the embodiment of the disclosed technology.

<FIG> illustrates an example of a functional configuration of the control device <NUM>. As illustrated in <FIG>, the control device <NUM> is configured with an image input portion <NUM>, an information generation portion <NUM>, an information storage portion <NUM>, a first reference signal output portion 83A, a second reference signal output portion 83B, a light emission controller <NUM>, a correction portion <NUM>, a table holding portion <NUM>, and a humidity and temperature sensor <NUM>. The image input portion <NUM>, the information generation portion <NUM>, the information storage portion <NUM>, the first reference signal output portion 83A, the second reference signal output portion 83B, the light emission controller <NUM>, the correction portion <NUM>, and the table holding portion <NUM> are functional portions implemented by causing the FPGA 20A and the memory 20B to operate in cooperation.

Image data DT that represents the image to be formed is input into the image input portion <NUM> from the outside. Hereinafter, the image corresponding to the image data DT input into the image input portion <NUM> may be referred to as an input image. As an example, in the present embodiment, the image data DT of colors represented by RGB signals is input into the image input portion <NUM>. The image data DT input into the image input portion <NUM> is output to the information generation portion <NUM>. The image data DT input into the image input portion <NUM> is not limited to the present embodiment and may be data corresponding to the image to be formed. For example, the image data DT may be binarized data that represents whether or not to output the laser light L. In addition, for example, the image data DT may be data that represents multiple values of an output amount.

The information generation portion <NUM> generates intensity information SI that represents a correspondence relationship between a scanning position of the laser light L by the MEMS mirror <NUM> and a signal intensity of the input image. In a case where the input image is a color image, the signal intensity represents an intensity of each of the RGB signals. The information storage portion <NUM> stores the intensity information SI generated by the information generation portion <NUM>.

The MEMS driver <NUM> outputs first driving signals V1A and V1B illustrated in <FIG> as an example to the pair of first actuators <NUM> of the MEMS mirror <NUM>, and generates a first zero cross signal ZC1 and outputs the first zero cross signal ZC1 to the first reference signal output portion 83A. The first driving signal V1A and the first driving signal V1B are sine waves having a phase difference of <NUM>°.

The first zero cross signal ZC1 is a pulsed signal that represents points at which the first driving signals V1A and V1B become zero. Signals output to the first reference signal output portion 83A from the MEMS driver <NUM> are not limited to zero cross signals and may be signals having the same periods as the first driving signals V1A and V1B.

The MEMS driver <NUM> outputs second driving signals V2A and V2B illustrated in <FIG> as an example to the pair of second actuators <NUM> of the MEMS mirror <NUM>, and generates a second zero cross signal ZC2 and outputs the second zero cross signal ZC2 to the second reference signal output portion 83B. The second driving signal V2A and the second driving signal V2B are sine waves having a phase difference of <NUM>°.

The second zero cross signal ZC2 is a pulsed signal that represents points at which the second driving signals V2A and V2B become zero. Signals output to the second reference signal output portion 83B from the MEMS driver <NUM> are not limited to zero cross signals and may be signals having the same periods as the second driving signals V2A and V2B.

A frequency (hereinafter, referred to as a first driving frequency) of the first driving signals V1A and V1B and a frequency (hereinafter, referred to as a second driving frequency) of the second driving signals V2A and V2B have different frequency ratios. A frequency ratio of the first driving frequency and the second driving frequency is decided based on a shape of a Lissajous curve of light scanning performed by the MEMS mirror <NUM>.

The first reference signal output portion 83A outputs a first reference signal PS1 to the light emission controller <NUM> by estimating a point in time when a deflection angle (hereinafter, referred to as a first deflection angle) θ1 of the mirror portion <NUM> about the first axis a<NUM> becomes equal to a first reference angle. In the present embodiment, the first reference angle is set to <NUM>°. The first reference signal output portion 83A generates the first reference signal PS1 by estimating the point in time when the first deflection angle θ1 becomes equal to the first reference angle, based on the first driving signals V1A and V1B.

Specifically, as illustrated in <FIG>, the first reference signal output portion 83A outputs a signal obtained by delaying the first zero cross signal ZC1 input from the MEMS driver <NUM> by a delay time period D1 as the first reference signal PS1. In a case where the mirror portion <NUM> resonates about the first axis a<NUM>, the delay time period D1 is ideally a time period corresponding to <NUM>/<NUM> of a period of the first zero cross signal ZC1. However, a shift occurs due to an environmental condition (a temperature, a humidity, and the like). Thus, in the present embodiment, the first reference signal output portion 83A acquires the delay time period D1 based on a temperature and a humidity detected by the humidity and temperature sensor <NUM> and a look-up table (hereinafter, referred to as the LUT) 86A held in the table holding portion <NUM>, and generates the first reference signal PS1 based on the acquired delay time period D1.

The second reference signal output portion 83B outputs a second reference signal PS2 to the light emission controller <NUM> by estimating a point in time when a deflection angle (hereinafter, referred to as a second deflection angle) θ2 of the mirror portion <NUM> about the second axis a<NUM> becomes equal to a second reference angle. In the present embodiment, the second reference angle is set to <NUM>°. The second reference signal output portion 83B generates the second reference signal PS2 by estimating the point in time when the second deflection angle θ2 becomes equal to the second reference angle, based on the second driving signals V2A and V2B.

Specifically, as illustrated in <FIG>, the second reference signal output portion 83B outputs a signal obtained by delaying the second zero cross signal ZC2 input from the MEMS driver <NUM> by a delay time period D2 as the second reference signal PS2. In a case where the mirror portion <NUM> resonates about the second axis a<NUM>, the delay time period D2 is ideally a time period corresponding to <NUM>/<NUM> of a period of the second zero cross signal ZC2. However, a shift occurs due to an environmental condition (a temperature, a humidity, and the like). Thus, in the present embodiment, the second reference signal output portion 83B acquires the delay time period D2 based on the temperature and the humidity detected by the humidity and temperature sensor <NUM> and the LUT 86A held in the table holding portion <NUM>, and generates the second reference signal PS2 based on the acquired delay time period D2.

A relationship among the delay time period D1, the temperature, and the humidity and a relationship among the delay time period D2, the temperature, and the humidity are recorded in advance in the LUT 86A. For example, these relationships are decided based on a past history.

The light emission controller <NUM> causes the light emitting device <NUM> to emit the laser light L based on the first reference signal PS1 and the second reference signal PS2. In a drawing mode in which the image based on the image data DT is drawn on the projection surface <NUM>, the light emission controller <NUM> reads out the intensity information SI from the information storage portion <NUM> and causes the light emitting device <NUM> to emit the laser light L having an intensity decided based on the first reference signal PS1 and the second reference signal PS2 for each constant time period (for example, for each clock period).

In addition, in the present embodiment, a calibration mode for correcting the timings of the first reference signal PS1 and the second reference signal PS2 output by the first reference signal output portion 83A and the second reference signal output portion 83B, respectively, is performed. In the calibration mode, the light emission controller <NUM> causes the light emitting device <NUM> to emit the laser light L in accordance with the timing at which the first reference signal PS1 is output from the first reference signal output portion 83A, and the timing at which the second reference signal PS2 is output from the second reference signal output portion 83B. That is, in the calibration mode, the light emission controller <NUM> causes the light emitting device <NUM> to emit the laser light L at the point in time when the first deflection angle θ1 is estimated to become equal to the first reference angle (in the present embodiment, <NUM>°), and the point in time when the second deflection angle θ2 is estimated to become equal to the second reference angle (in the present embodiment, <NUM>°).

In the calibration mode, the imaging apparatus <NUM> images the laser light L reflected on the light extraction region <NUM> out of the laser light L that is emitted from the light emitting device <NUM> and is reflected by the mirror portion <NUM>. The imaging apparatus <NUM> outputs the captured image IP generated by the imaging to the correction portion <NUM>. A pattern drawn on the projection surface <NUM> is imaged in the captured image IP.

The correction portion <NUM> corrects the timings of the first reference signal PS1 and the second reference signal PS2 output by the first reference signal output portion 83A and the second reference signal output portion 83B, respectively, based on a shift amount of the pattern captured in the captured image IP from a predetermined shape.

<FIG> illustrates an example of the pattern drawn on the projection surface <NUM> in the calibration mode. In the present example, the frequency ratio of the first driving frequency and the second driving frequency is set to <NUM>:<NUM> for simplification of description. In the present example, a Lissajous curve <NUM> is drawn on the projection surface <NUM> by the light scanning performed by the MEMS mirror <NUM>.

<FIG> illustrates a case where a shift does not occur between the swing of the mirror portion <NUM> and the timings of the first reference signal PS1 and the second reference signal PS2. In such a manner, in a case where a shift does not occur, the light emitting device <NUM> emits the laser light L at the point in time of θ1 = <NUM> and the point in time of θ2 = <NUM>. Thus, a first reference line L1 and a second reference line L2 on the projection surface <NUM> are irradiated with the laser light L. The first reference line L1 is a straight line that passes through a center of the Lissajous curve <NUM> and is parallel to the X direction. The second reference line L2 is a straight line that passes through the center of the Lissajous curve <NUM> and is parallel to the Y direction. Reference numeral P denotes a point (that is, a bright point) irradiated with the laser light L on the projection surface <NUM>.

In a case where the frequency ratio of the first driving frequency and the second driving frequency is set to make the Lissajous curve <NUM> more precise, the bright points P draw straight line patterns along the first reference line L1 and the second reference line L2.

<FIG> illustrates a case where a shift occurs between the swing of the mirror portion <NUM> and the timings of the first reference signal PS1 and the second reference signal PS2. In such a manner, in a case where a shift occurs, the light emitting device <NUM> emits the laser light L at points in time shifted from the point in time of θ1 = <NUM> and the point in time of θ2 = <NUM>. Thus, positions shifted from the first reference line L1 and the second reference line L2 on the projection surface <NUM> are irradiated with the laser light L. In the present example, straight lines L1A and L1B shifted from the first reference line L1 and straight lines L2A and L2B shifted from the second reference line L2 are irradiated with the laser light L.

The straight line L1A is a line that is irradiated with the laser light L on an advancing path of Lissajous scanning. The straight line L1B is a line that is irradiated with the laser light L on a returning path of the Lissajous scanning. In addition, the straight line L2A is a line that is irradiated with the laser light L on the advancing path of the Lissajous scanning. The straight line L2B is a line that is irradiated with the laser light L on the returning path of the Lissajous scanning. The advancing path refers to a path along which the first deflection angle θ1 is increased for the Y direction, and a path along which the second deflection angle θ2 is increased for the X direction. The returning path refers to a path along which the first deflection angle θ1 is decreased for the Y direction, and a path along which the second deflection angle θ2 is decreased for the X direction.

In such a manner, in a case where a shift occurs between the swing of the mirror portion <NUM> and the timings of the first reference signal PS1 and the second reference signal PS2, the first reference line L1 is separated into the straight line L1A and the straight line L1B, and the second reference line L2 is separated into the straight line L2A and the straight line L2B.

In a case where the frequency ratio of the first driving frequency and the second driving frequency is set to make the Lissajous curve <NUM> more precise, the bright points P draw straight line patterns along the straight line L1A, the straight line L1B, the straight line L2A, and the straight line L2B.

<FIG> illustrates an example of a functional configuration of the correction portion <NUM>. The correction portion <NUM> includes a correction amount calculation portion <NUM> and a signal correction portion <NUM>. The captured image IP is input into the correction portion <NUM> from the imaging apparatus <NUM>.

The correction amount calculation portion <NUM> derives a shift amount ΔY between the straight line L1A and the straight line L1B in the Y direction and a shift amount ΔX between the straight line L2A and the straight line L2B in the X direction based on the captured image IP. In addition, the correction amount calculation portion <NUM> derives a correction amount δ1 of the timing of the first reference signal PS1 for ΔX = <NUM> and a correction amount δ2 of the timing of the second reference signal PS2 for ΔY = <NUM> and outputs the derived correction amounts δ1 and δ2 to the signal correction portion <NUM>. For example, the correction amount calculation portion <NUM> derives the correction amounts δ1 and δ2 based on a relationship between the shift amount ΔX and the correction amount δ1 and a relationship between the shift amount ΔY and the correction amount δ2 stored in advance. Each of the relationship between the shift amount ΔX and the correction amount δ1 and the relationship between the shift amount ΔY and the correction amount δ2 is an almost proportional relationship.

The correction amount calculation portion <NUM> derives the shift amounts ΔX and ΔY based on the captured image IP obtained in a state where the timings of the first reference signal PS1 and the second reference signal PS2 are not corrected (that is, a state of δ1 = <NUM> and δ2 = <NUM>), and derives the correction amounts δ1 and δ2 based on the derived shift amounts ΔX and ΔY.

The signal correction portion <NUM> corrects the timing of the first reference signal PS1 output from the first reference signal output portion 83A based on the correction amount δ1 input from the correction amount calculation portion <NUM>, and corrects the timing of the second reference signal PS2 output from the second reference signal output portion 83B based on the correction amount δ2 input from the correction amount calculation portion <NUM>.

<FIG> illustrate an example of timing correction performed by the signal correction portion <NUM>. <FIG> illustrates an example of correcting the timing of the first reference signal PS1 based on the correction amount δ1. <FIG> illustrates an example of correcting the timing of the second reference signal PS2 based on the correction amount δ2. Correcting the timings of the first reference signal PS1 and the second reference signal PS2 results in ΔX = <NUM> and ΔY = <NUM>. Accordingly, the straight line L1A matches the straight line L1B, and the straight line L2A matches the straight line L2B.

The signal correction portion <NUM> may be provided inside each of the first reference signal output portion 83A and the second reference signal output portion 83B. In this case, the first reference signal output portion 83A corrects the timing of the first reference signal PS1 based on the correction amount δ1 input from the correction amount calculation portion <NUM>. Similarly, the second reference signal output portion 83B corrects the timing of the second reference signal PS2 based on the correction amount δ2 input from the correction amount calculation portion <NUM>.

For example, the calibration mode is executed for a predetermined period when the image forming apparatus <NUM> is started. After the calibration mode is finished, the first reference signal output portion 83A and the second reference signal output portion 83B continue the timing correction based on the correction amounts δ1 and δ2 in the drawing mode. The calibration mode may be periodically executed during execution of the drawing mode.

As described above, the image forming apparatus <NUM> according to the present embodiment can suppress distortion of the image drawn on the projection surface <NUM> by correcting the timings of the first reference signal PS1 and the second reference signal PS2 based on the imaging information acquired by the imaging apparatus <NUM>.

In each of the embodiments, while the MEMS mirror <NUM> of two axes is used as the light scanning device, a MEMS mirror of one axis may be used as the light scanning device. Accordingly, the disclosed technology can also be applied to an image forming apparatus comprising a light scanning device of one axis in which a movable mirror swings about a first axis.

In the third embodiment, for example, the following various processors can be used as a hardware structure of a processing unit that executes various processing of the image input portion <NUM>, the information generation portion <NUM>, the information storage portion <NUM>, the first reference signal output portion 83A, the second reference signal output portion 83B, the light emission controller <NUM>, the correction portion <NUM>, and the table holding portion <NUM>. The various processors include, in addition to a central processing unit (CPU) that is a general-purpose processor functioning as various processing units by executing software (program), a programmable logic device (PLD) such as the FPGA that is a processor having a circuit configuration changeable after manufacturing, a dedicated electric circuit such as an application specific integrated circuit (ASIC) that is a processor having a circuit configuration dedicatedly designed to execute specific processing, and the like.

One processing unit may be configured with one of the various processors or may be configured with a combination of two or more processors of the same type or different types (for example, a combination of a plurality of FPGAs and/or a combination of a CPU and an FPGA). In addition, a plurality of processing units may be configured with one processor.

Examples of the plurality of processing units configured with one processor include, first, as represented by a computer such as a client and a server, a form in which one processor is configured with a combination of one or more CPUs and software, and the processor functions as the plurality of processing units. Second, as represented by a system on chip (SoC) or the like, a form of using a processor that implements functions of the entire system including the plurality of processing units by one integrated circuit (IC) chip is included. In such a manner, various processing units are configured using one or more of the various processors as a hardware structure.

Claim 1:
A light scanning device (<NUM>) comprising:
a mirror device that includes a movable mirror (<NUM>) which swings about at least one axis; and
a package (<NUM>) that has at least two or more light transmission surfaces (<NUM>) not constituting the same plane and accommodates the mirror device (<NUM>), wherein the package (<NUM>) is configured with a substrate (<NUM>) having a flat plate shape and a lid member (<NUM>) having a box shape, wherein an imaging apparatus (<NUM>) and a signal output terminal (<NUM>) for extracting an imaging signal output from the imaging apparatus (<NUM>) to the outside are provided inside the package (<NUM>),
wherein out of the two or more light transmission surfaces (<NUM>) of the package (<NUM>), one light transmission surface is a light receiving surface for receiving an incidence ray on the movable mirror (<NUM>) from an outside, and the other light transmission surface is a light extraction surface for extracting light reflected by the movable mirror (<NUM>) to the outside,
wherein the light extraction surface guides a part of the light reflected by the movable mirror (<NUM>) to the imaging apparatus (<NUM>) by reflecting the part of the light, and
wherein the light receiving surface and the light extraction surface are configured with two light transmission surfaces (<NUM>) that are not parallel.