JP2017105291A - Head-up display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a head-up display device which is mounted to a vehicle and can more accurately detect light intensity even when the output range of a light source is large.SOLUTION: An HUD device A is mounted to a vehicle, enlarges, projects and displays a display image L while using output light from a light source 11. The HUD device comprises a photodiode 50a which detects output intensity from the light source 11 and emits a detection signal, an operational amplifier 50b which amplifies the detection signal and emits the same as an output signal, and a switch circuit 50g connected to plural resistor 50c-50f for changing the amplification factor of the operational amplifier 50b.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a head-up display device, for example, suitable for a head-up display device for a vehicle having a wide output range from high luminance to low luminance.

  A conventional head-up display is disclosed in, for example, Patent Document 1. Such a head-up display described in Patent Document 1 is attached to the inside of an instrument panel (hereinafter referred to as an instrument panel) of a vehicle, and projects display light emitted from a display device onto a windshield (projection member) of the vehicle. A virtual image is displayed to the vehicle user (driver).

  In addition, there is one in which a DMD (digital micromirror device) is used as an optical engine of a conventional head-up display, which is disclosed in Patent Document 2, for example. This optical engine includes a detection circuit using a photosensor for detecting the light intensity of each light-emitting diode, and performs feedback control so that the light source is output with accurate luminance.

JP-A-9-109732 Japanese Patent Laying-Open No. 2015-132658

  These head-up displays are mounted on vehicles, and the required display becomes large in the output range from high brightness to low brightness in combination with the environment where the difference in brightness is large. A configuration for detection was required.

  Moreover, not only changes in the temperature environment outside the vehicle, but also temperature changes such as high temperatures due to sunlight irradiation and heat generation of the light source elements are large. For this reason, the value of the internal resistance changes depending on the temperature characteristics of each electronic component, and the output of the detection circuit using the photosensor may not be accurate, which has been a problem.

  Accordingly, an object of the present invention is to provide a head-up display device that can detect a more accurate light intensity even when mounted on a vehicle and has a large output range of a light source, paying attention to the above-described problems.

The head-up display device of the present invention is
A head-up display device mounted on a vehicle and displaying an enlarged display image using output light from a light source,
A detection element for detecting an output intensity from the light source and emitting a detection signal;
An amplification circuit for amplifying the detection signal and generating an output signal;
Switching means for switching the amplification factor of the amplifier circuit.

The amplifier circuit uses an operational amplifier,
The switching means is connected between the input and output terminals of the amplifier circuit,
A plurality of resistors connected in parallel to the detection element;
Switch means for selecting one of the resistors and connecting to the output of the amplifier circuit is provided.

In addition, it comprises a control means for inputting the output signal and adjusting the output of the light source,
The control means controls the switching means so as to select a resistor having a larger resistance value from the plurality of resistors and increase the amplification factor of the amplifier circuit at the time of the low luminance. To do.

  The head-up display device of the present invention can detect more accurate light intensity even when the output range of the light source is large.

The figure which shows the vehicle-mounted example of the head-up display apparatus by embodiment of this invention. Sectional drawing which shows the vehicle-mounted example of the head-up display apparatus by the embodiment. Sectional drawing of the head-up display apparatus by the embodiment. The figure which shows the illuminating device by the embodiment. The block diagram which shows the structure of the head-up display apparatus by the embodiment. The figure which shows the circuit structure of the light intensity detection part by the embodiment.

  A display device according to an embodiment of the present invention is a head-up display device (hereinafter referred to as a HUD device) A shown in FIGS. As shown in the figure, the HUD device A is arranged on the dashboard C of the vehicle B and emits the display light L representing the generated image (vehicle information) toward the windshield D. The display light L reflected by the windshield D is visually recognized as a virtual image F of an image formed in front of the windshield D by an observer E (mainly a driver of the vehicle B). In this way, the HUD device A causes the observer E to visually recognize the image as a virtual image F. This image notifies information related to the vehicle B (for example, traveling speed, engine speed, navigation information, etc.).

  As shown in FIGS. 3 and 4, the HUD device A has a mirror unit 6 including an illumination device 1, an illumination optical system 2, a display element 3, a projection optical system 4, a screen 5, a plane mirror 61 and a concave mirror 62. And a housing 7 having a translucent portion 71. Further, as shown in FIG. 5, the lighting device 1 of the HUD device A includes a first control unit 10, a second control unit 20, a dimming circuit 30, a light source driving unit 40, and a light intensity detection unit. 50.

  The illumination device 1 emits light (illumination light L1), which will be described later, toward the illumination optical system 2. As shown in FIG. 4, the light source 11, the circuit board 12, the multiplexing means 13, and the luminance The unevenness reducing means 14 and the permeable membrane 15 are provided.

  The light source 11 includes, for example, light sources 11r, 11g, and 11b made of light emitting diodes (LEDs). The light source 11r emits red light Lr, the light source 11g emits green light Lg, and the light source 11b emits blue light Lb. Each of the light sources 11r, 11g, and 11b is driven by the first control unit 10 and emits light at a predetermined light intensity and timing. In the present embodiment, the light sources 11r, 11g, and 11b are independent light sources 11. However, a plurality of colors of light may be emitted from the common light source 11. Moreover, the light source 11 should just be what emits the light of multiple colors, may be comprised only by 2 colors, and may be comprised by 4 colors (including white) or more. The circuit board 12 is a printed circuit board. Light sources 11r, 11g, and 11b are mounted on the circuit board 12.

  The multiplexing unit 13 emits the light Lr, Lg, and Lb emitted from the light sources 11r, 11g, and 11b and directs the light Lr, Lg, and Lb that arrives substantially in one direction (luminance unevenness reducing unit 14 side). Specifically, the multiplexing means 13 includes a reflecting portion 13a made of a reflecting mirror, and combining portions 13b and 13c made of dichroic mirrors that reflect light of a specific wavelength but transmit light of other wavelengths. It is configured.

  The reflection part 13a is located on the emission side of the light source 11b. The reflection unit 13a reflects the incident blue light Lb toward the multiplexing unit 13b. The multiplexing unit 13b is located on the emission side of the light source 11g. The combining unit 13b reflects the incident green light Lg toward the combining unit 13c, and transmits the blue light Lb from the reflecting unit 13a as it is. The multiplexing unit 13c is located on the emission side of the light source 11r. The multiplexing unit 13c reflects the incident red light Lr toward the illumination optical system 20, and transmits the light Lb and the light Lg from the multiplexing unit 13b as they are. That is, from the multiplexing unit 13c, the illumination light L1 (blue light Lb, green light Lg, or red light Lr) sequentially emitted from the light source 11 is emitted in approximately one direction (luminance unevenness reducing unit 14 side). Note that the multiplexing means 13 aligns the optical axes of the light sources 11r, 11g, and 11b, and may be omitted when a plurality of colors of light are emitted from one light source 11.

  The luminance unevenness reducing unit 14 includes a mirror box, an array lens, and the like, and reduces unevenness of light by irregularly reflecting, scattering, and refracting the illumination light L1 from the multiplexing unit 13. The illuminating device 1 converts the light emitted from the light source 11 into the illumination light L1 (blue) via the multiplexing unit 13 and the luminance unevenness reducing unit 14 (and the transmission film 15 described below) described above. Light Lb, green light Lg, or red light Lr) is emitted toward the illumination optical system 2.

  The transmissive film 15 is made of a transmissive member having a reflectivity of, for example, about 5%, and transmits most of the illumination light L1 that has reached through the luminance unevenness reducing unit 14 as it is. Reflected in the direction of the part 50.

  As shown in FIG. 6, the light intensity detection unit 50 uses, for example, a detection element having a photodiode 50 a and is provided at a position that receives the illumination light L <b> 1 reflected by the transmission film 15. The light intensity detector 50 receives a part of the illumination light L1 and detects the light intensity of each of the lights Lr, Lg, and Lb in a time division manner.

  The light intensity detection unit 50 only needs to be able to detect the light intensity of each of Lr, Lg, and Lb. Therefore, for example, the light Lr, Lg, and Lb before being combined are not the optical paths of the illumination light L1. It may be provided at a location where the light intensity can be detected. Further, the light intensity detection unit 50 may be appropriately provided at a place where a part of the light intensity of the illumination light L1 emitted from the illumination optical system 2 can be detected. The function of the light intensity detector 50 will be described in detail later.

  The illumination optical system 2 is composed of a concave lens or the like, and adjusts the illumination light L1 emitted from the illumination device 1 to a size corresponding to the display element 3.

  The display element 3 can be a DMD having a plurality of movable micromirrors, and the illumination light L1 emitted from the illumination optical system 2 can be obtained by controlling each mirror in an on or off state. Reflect appropriately. The display element 3 projects the image (light for generating an image) toward the projection optical system 4 by reflecting the illumination light L1 in this way.

  Specifically, an electrode is provided below the micromirror. By driving each mirror with a very short cycle (for example, a microsecond cycle), the mirror is turned on or off. Become. Each mirror is movable with a hinge as a fulcrum, and when the mirror is in an on state, the mirror surface is tilted by +12 degrees with the hinge as a fulcrum, and when the mirror is in an off state, the mirror surface is tilted by -12 degrees with the hinge as a fulcrum. The on-state mirror reflects the illumination light L1 from the illumination optical system 2 in the direction of the projection optical system 4, and the off-state mirror does not reflect the illumination light L1 in the direction of the projection optical system 4. The display element 3 projects an image (display light L) toward the projection optical system 4 by driving each mirror individually.

  The projection optical system 4 is configured by a concave lens or a convex lens, and is an optical system for efficiently projecting the display light L from the display element 3 onto the screen 5.

  The screen 5 includes a holographic diffuser, a microlens array, a diffusion plate, and the like. The screen 5 receives the display light L from the projection optical system 4 on the back surface (the surface on the display element 3 side), and on the front surface (the mirror unit 6 side). Display an image.

  The plane mirror 61 reflects the display light L representing the image displayed on the screen 5 toward the concave mirror 62. The concave mirror 62 emits the reflected light in the direction of the windshield D by reflecting the display light L that has arrived from the plane mirror 61 on the concave surface. As a result, the virtual image F to be formed becomes larger than the image displayed on the screen 5. The display light L reflected by the concave mirror 62 reaches the windshield D via the translucent part 71.

  The housing 7 houses the illumination device 1, the illumination optical system 2, the display element 3, the projection optical system 4, the screen 5, the plane mirror 61, the concave mirror 62, and the like at predetermined positions. The casing 7 is formed of a portion other than the light transmitting portion 71 by, for example, a light shielding member. The translucent part 71 is made of a translucent resin such as acrylic and transmits the display light L from the concave mirror 62. The translucent part 71 is fitted to the housing 7, for example. The translucent portion 71 is formed in, for example, a curved shape so that the outside light that has reached (for example, sunlight or light from a streetlight) is not reflected in the direction of the viewer E.

  Next, with reference to FIGS. 5 and 6, a configuration related to light source driving will be described in detail.

  As illustrated in FIG. 5, the illumination device 1 includes a first control unit 10, a second control unit 20, a dimming circuit 30, a light source driving unit 40, and a light intensity detection unit 50. These are mounted, for example, on a printed circuit board disposed in the housing 70. A part or all of the first control unit 10, the second control unit 20, the dimming circuit 30, and the light source driving unit 40 may be mounted on the circuit board 12 as the printed circuit board.

  The first control unit 10 includes a microcontroller and includes a CPU, a memory (RAM, ROM), and the like. The CPU controls each unit by reading and executing a program necessary for the operation of the HUD device A stored in advance in the ROM. The first control unit 10 receives a video signal for displaying an image from a vehicle ECU (electronic control unit) 60 of the vehicle B by LVDS (Low Voltage Differential Signal) communication, etc. The controller 10 receives an external illuminance signal (dimming signal) SL around the vehicle B from the vehicle ECU 60, adjusts the light emission intensity of the light source 11 based on these signals, and further passes through the second controller 20. A desired display image is displayed on the display element 3.

  The video signal output from the first control unit 10 is input to the second control unit 20 via an image processing IC (not shown). Further, the video signal from the vehicle ECU 60 may be directly input to the second control unit 20 to be described later via an image processing IC (not shown) without passing through the first control unit 10.

The first control unit 10 controls each unit as follows in order to control the light source 11.
(1) The first control unit 10 outputs the reference signal SA to one input terminal of the comparison circuit 41. The reference signal SA indicates a set value of the light source 11 and is generated based on an external illuminance signal (dimming signal) SL input from the vehicle ECU 60 to the first control unit 10. For example, the first control unit 10 refers to the table data in which the intensity value indicated by the external illuminance signal SL corresponds to the set value from the memory, and the duty of the set value corresponding to the intensity value indicated by the acquired external illuminance signal SL. A ratio pulse signal is output, this pulse signal is converted into an analog signal by an analog converter comprising an integration circuit (not shown), and this analog signal is output to the comparison circuit 41 as a reference signal SA.

  The frequency of the pulse signal for generating the reference signal SA output from the first control unit 10 is desirably 30 kHz or more. The magnitude of the value of the reference signal SA associated with the external illuminance signal SL differs for each color of light emitted from the light source 11. Accordingly, the magnitude of the reference signal SA output from the first control unit 10 to the comparison circuit 41 is different for each subframe that emits a different color. With such a configuration, even when the light intensity detection signal SFB of each color is processed by the common comparison circuit 41, the light amount of each color emitted from the light source 11 can be appropriately determined and adjusted.

  (2) The first control unit 10 outputs the limit signal SC to the input terminal of the logic circuit 42 via the second control unit 20. The limit signal SC is used as a permission signal SC or a comparison signal SB for causing the logic circuit 42 to output a drive signal SD corresponding to the comparison signal SB for a predetermined period with respect to the comparison signal SB input from the comparison circuit 41. It consists of a prohibition signal SC for causing the logic circuit 42 to output an unreliable drive signal SD. The first control unit 10 determines whether or not the external illuminance signal SL input from the vehicle ECU 60 is less than a predetermined threshold value. If the external illuminance signal SL is less than the threshold value, the first control unit 10 permits the second control unit 20 to When the external illuminance signal SL is equal to or greater than the threshold value, the second control unit 20 is caused to output the limit signal SC including the permission signal.

  (3) Furthermore, the first control unit 10 controls the light control circuit 30 and sets a voltage to be applied to the light source 11.

  (4) Further, the first control unit 10 is an amplification provided between the light intensity detection unit 50 (not shown) and the comparison circuit 41 with a gain set in advance according to the external illuminance signal SL input from the vehicle ECU 60. Output to the circuit.

  The second control unit 20 can apply an integrated circuit (LSI) that realizes a desired function by hardware. In addition, a memory (not shown) is connected to the second control unit 20, and data for outputting a limit signal SC corresponding to a signal from the first control unit 10, Data for controlling an enable signal EN for controlling the light emission timing of the light source 11 according to the illumination control data from the control unit 10 and the display element 3 according to the display control data from the first control unit 10 are controlled. The data for is stored.

  The light control circuit 30 includes a power supply IC, a switching circuit using a transistor, and the like. The dimming circuit 30 applies a voltage of an appropriate value to the light source 11 under the control of the first control unit 10 using electric power from a battery (not shown) of the vehicle B. The light control circuit 30 is connected to the anode side of the light sources 11r, 11g, and 11b as shown in FIG. Thus, by providing a common supply voltage line on the anode side of each color light emitting diode, the number of components such as the dimming circuit 30 and the number of wirings can be reduced. The dimming circuit 30 may be integrated into an integrated circuit of the light source driving means 40 described later.

  As the light source driving means 40, an integrated circuit that realizes a desired function by hardware can be applied. The light source drive means 40 includes a comparison circuit 41, a logic circuit 42, and a switch means 43, and is based on the light intensity of the illumination light L1 (blue light Lb, green light Lg, or red light Lr) emitted from the light source 11. The light intensity detection signal SFB is input from the light intensity detection unit 50, a drive signal SD for driving the light source 11 is generated from the light intensity detection signal SFB, and the switch means 43 is turned on / off based on the drive signal SD. By operating, the light source 11 is turned on / off.

  The comparison circuit 41 includes a comparator (comparator), compares the light intensity detection signal SFB input from the light intensity detection unit 50 with the reference signal SA output from the first control unit 10, and compares the comparison result as a comparison result. Signal SB is output to logic circuit 42. An amplifier circuit is provided between the light intensity detection unit 50 and the comparison circuit 41, and the light intensity detection signal SFB is amplified by the amplification circuit and then input to the comparison circuit 41. In the amplifier circuit, as described above, the first control unit 10 determines the gain according to the external illuminance signal SL input from the vehicle ECU 60.

  The logic circuit 42 is configured using a plurality of AND circuits. The logic circuit 42 receives the limit signal SC and the enable signal EN from the second control unit 20 and the comparison signal SB from the comparison circuit 41, and a red drive signal for driving the red light source 11r by these AND circuits. The SDR or the green drive signal SDG for driving the green light source 11g or the blue drive signal SDB for driving the blue light source 11b is output to the red switch means 431, the green switch means 432, and the blue switch means 433, respectively.

  The switch means 43 is composed of a switching circuit using, for example, an n-type channel or p-type channel FET (field effect transistor). The switch means 43 performs an on / off operation according to the output from the logic circuit 42. As shown in FIG. 5, for example, as shown in FIG. 5, the red switch means 431 connected to the cathode side of the red light source 11r, the green switch means 432 connected to the cathode side of the green light source 11g, and the cathode side of the blue light source 11b It has blue switch means 433 connected.

  Each of the light sources 11r, 11g, and 11b is supplied with a drive current according to the light emission timing determined by each enable signal EN by the logic circuit 42. Thereby, the light sources 11r, 11g, and 11b of different colors are sequentially turned on every predetermined period (period in which the enable signal EN is turned on) (field sequential color system).

  The light intensity detector 50 receives the illumination light L1 emitted from the light source 11, and detects the light intensities of the lights Lr, Lg, and Lb in a time division manner. The light intensity detector 50 outputs a light intensity detection signal SFB (voltage signal) indicating the detected emission intensity. In this case, the light intensity detection signal SFB indicating the light emission intensity of the light source 11 input by the light intensity detection unit 50 is input, and the light source driving means 40 receives the drive signal SD (red drive signal SDR, green drive from the light intensity detection signal SFB). Signal SDG, blue drive signal SDB) is generated, and feedback control is performed to drive each color light source 11 again based on this drive signal SD, so that monitoring control is performed so that the light source 11 has a desired light emission intensity. .

  Further, as shown in FIG. 6, the light intensity detector 50 includes a photodiode 50a, an operational amplifier (amplifier circuit) 50b, a plurality of resistors 50c, 50d, 50e, and 50f, and a switch circuit 50g.

  The photodiode 50a is provided in the housing 7, and is provided such that the light intensity detection surface faces the position where the illumination light L1 reflected by the transmission film 15 is received. The detection element including the photodiode 50a can emit a detection signal according to the received light intensity (output intensity from the light source 11), and is connected to the operational amplifier 50b. To 50 f respectively.

  The operational amplifier 50b is connected to the GND terminal (installation side terminal) and the output terminal (cathode terminal) of the photodiode 50a on the input side, and the comparison circuit 41 is connected to the output side. It is connected to the circuit 50g. The operational amplifier 50b amplifies the detection signal from the photodiode 50a with a desired amplification factor by feeding back a resistance value determined by a switching means including a plurality of resistors 50c to 50f and a switch circuit, and outputs it as an output signal. The data can be output to the comparison circuit 41.

  The plurality of resistors 50c to 50f are interposed between the connection line between the photodiode 50a and the operational amplifier 50b and the output terminal of the operational amplifier 50b, and determine the amplification factor of the detection signal of the photodiode 50a. It is selectively connected by a switch circuit 50g. The plurality of resistors 50c to 50f have different resistance values, and are provided in accordance with the output range of the detection signal of the photodiode 50a so that detection can be performed from high illuminance to low illuminance.

  The switch circuit 50g can be a semiconductor, selects one of the plurality of resistors 50c to t50f to switch the amplification factor based on a control signal from the first control unit 10, and selects an operational amplifier. An amplification factor of 50b is defined. The first control unit 10 amplifies and outputs the detection signal with a low amplification factor when the illumination light L1 based on the output from the light source 11 is large, and detects when the illumination light l1 is small. The sensitivity range of the light intensity detector 50 is switched so that the signal is amplified and output at a high amplification factor.

  Therefore, the light intensity detector 50 can accurately detect a large illuminance range without preparing a large number of phototransistors and their detection locations. Therefore, it is suitable for the HUD device A that needs to output the display light L in a large range from high luminance to low luminance suitable for the influence of the external environment such as sunlight.

  In addition, by applying the circuit configuration shown in FIG. 6, for example, assuming use in a dark environment such as at night, since it is a low-light state that is sensitive as a human sensitivity characteristic, more accurate detection of light intensity is possible. Although necessary, at this time, a resistor having a large resistance value is selected to determine the amplification factor, so that the influence of the internal resistance of the switch circuit 50g connected to the resistors 50c to 50f can be reduced. Therefore, particularly in a low illuminance state, the circuit configuration is such that the influence of the internal resistance, which changes the resistance value depending on the temperature, can be reduced, and more accurate light intensity can be detected.

  Such a HUD device A is a HUD device A that is mounted on a vehicle and that projects and displays a display image (display light) L by using the output light from the light source 11, and outputs the output intensity from the light source 11. A photodiode 50a that detects and emits a detection signal, an operational amplifier 50b that amplifies the detection signal and emits it as an output signal, and a switch circuit 50g connected to a plurality of resistors 50c to 50f for switching the amplification factor of the operational amplifier 50b And comprising.

  Therefore, accurate light intensity can be detected even if the necessary display is a large output range from high luminance to low luminance according to an environment mounted on a vehicle and having a large difference in brightness. Further, as in the above-described embodiment, the red light Lr, the green light Lg, and the blue light Lb from the light sources 11r, 11g, and 11b can be time-divided and the light intensity can be accurately detected. Since the balance can be adjusted, the HUD apparatus A can display the display image with a desired color more accurately.

  The head-up display device of the present invention has been described by way of example in the configuration of the above-described embodiment, but the present invention is not limited to this, and the gist of the present invention can be applied to other configurations. It goes without saying that various improvements and display changes can be made without departing from the scope.

  The present invention relates to a head-up display device, for example, mounted on a moving body including an automobile, a motorcycle, or an agricultural machine or a construction machine, and is suitable as an in-vehicle display device for road information such as vehicle information and turn-by-turn display. is there.

DESCRIPTION OF SYMBOLS 1 Illuminating device 2 Illumination optical system 3 Display element 4 Projection optical system 5 Screen 6 Mirror unit 61 Plane mirror 62 Concave mirror 7 Case 71 Translucent part

DESCRIPTION OF SYMBOLS 11 Light source 12 Circuit board 13 Multiplexing means 14 Brightness nonuniformity reduction means 15 Transmission film

DESCRIPTION OF SYMBOLS 10 1st control part 20 2nd control part 30 Light control circuit 40 Light source drive means 41 Comparison circuit 42 Logic circuit 43 Switch means (switching means)
50 Light intensity detector 50a Photodiode (detection element)
50b Operational amplifier (amplifier circuit)
50c-50f Resistor 50g Switch circuit 60 Vehicle ECU

A HUD device (head-up display device)
B Vehicle C Dashboard L Display light L1 Illumination light D Windshield E Observer F Virtual image

Claims (3)

A head-up display device mounted on a vehicle and displaying an enlarged display image using output light from a light source,
A detection element for detecting an output intensity from the light source and emitting a detection signal;
An amplification circuit for amplifying the detection signal and generating an output signal;
A head-up display device comprising switching means for switching the amplification factor of the amplifier circuit. The amplifier circuit uses an operational amplifier,
The switching means is connected between the input and output terminals of the amplifier circuit,
A plurality of resistors connected in parallel to the detection element;
2. The head-up display device according to claim 1, further comprising switch means for selecting any one of the resistors and connecting the selected resistor to the output of the amplifier circuit. A control means for inputting the output signal and adjusting the output of the light source;
The control means controls the switching means so as to select a resistor having a larger resistance value from the plurality of resistors and increase the amplification factor of the amplifier circuit at the time of the low luminance. The head-up display device according to claim 2.

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