JP2017203825A - Display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a display device which allows smooth lighting control even if a duty ratio is small.SOLUTION: Control means 59 adjusts the luminance of light emission of a light emission display unit 22 by a lighting control signal. The control means 59 outputs a lighting control signal including: a first driving signal S1 made of first pulse signals P1 with a first pulse width W1; second driving signals S2, S3, and S4 made of a mixture of the first pulse signals P1 and second pulse signals P2 with a second pulse width W2; and a third driving signal S5 made of the second pulse signals P2.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a display device provided with a light emitting display.

  Conventionally, various display devices including a control unit that adjusts the light emission luminance of a light-emitting display have been proposed. For example, Patent Document 1 discloses the display device. Such a display device includes a microcomputer that adjusts the light emission luminance of a liquid crystal display (light-emitting display), and adjusts the light emission luminance according to a duty ratio of a PWM (Pulse Width Modulation) signal output from the microcomputer. is there. In addition, in order to perform smooth dimming using a PWM signal, it has been proposed to change the duty ratio stepwise, which is disclosed in, for example, Patent Document 2.

Japanese Patent No. 5283325 JP 2011-91024 A

However, when the duty ratio is small, there is a problem that smooth light control is not achieved and the light emission brightness appears to change abruptly. For example, when the resolution of the microcomputer that outputs the PWM signal is 16 bits (65536), when the duty ratio is switched from 1/65536 to 2/65536, the light emission luminance is instantaneously doubled. It feels like it has changed abruptly. In order to solve this problem, a microcomputer having a resolution of 32 bits may be used. However, such a high-performance microcomputer is expensive and causes an increase in cost.
The present invention provides a display device capable of smooth dimming even when the duty ratio is small.

  The present invention is a display device 21 that includes a light-emitting display 22 and a control unit 59 that adjusts the light emission luminance of the light-emitting display 22 using a dimming signal. The first drive signals S1 and S10 composed of the first pulse signal P1 having the first pulse width W1 and the second pulse signal P2 having the first pulse signal P1 and the second pulse width W2 are mixed. The dimming signal including the second driving signals S2, S3, S4, S7, S8, and S9 and the third driving signals S5 and S6 including the second pulse signal P2 is output.

  According to the present invention, the first drive signal S1 at a predetermined time T is composed of a predetermined number of the first pulse signals P1, and the second drive signal S1 at the predetermined time T following the first drive signal S1. In the drive signals S2, S3, S4, the sum of the number of pulses of the first pulse signal P1 and the number of pulses of the second pulse signal P2 is the predetermined number, and the second drive signals S2, S3, The third drive signal S5 at the predetermined time T following S4 is composed of the predetermined number of the second pulse signals P2.

  According to the present invention, the third drive signal S6 at a predetermined time T is composed of a predetermined number of the second pulse signals P2, and the second drive signal S6 at the predetermined time T following the third drive signal S6. In the drive signals S7, S8, S9, the total number of pulses of the first pulse signal P1 and the number of pulses of the second pulse signal P2 is the predetermined number, and the second drive signals S7, S8, S9, The first drive signal S10 at the predetermined time T following S9 is composed of the predetermined number of the first pulse signals P1.

  In the present invention, the ratio of the number of pulses of the first pulse signal P1 to the number of pulses of the second pulse signal P2 of the second drive signals S2, S3, S4 gradually changes. is there.

  The duty ratio of the dimming signal can be gradually changed, and smooth dimming becomes possible.

Sectional drawing which shows embodiment of this invention. The block diagram which shows embodiment same as the above. The external view which shows embodiment same as the above. Explanatory drawing of the light control signal which shows embodiment same as the above. Explanatory drawing of the light control signal which shows embodiment same as the above. Explanatory drawing of the light control signal which shows a comparative example.

  Hereinafter, an embodiment in which the present invention is applied to a vehicle head-up display device 21 will be described with reference to the accompanying drawings. The vehicle head-up display device 21 displays the virtual image V by projecting the display light L onto the windshield G of the vehicle.

  A vehicle head-up display device 21, a liquid crystal display 22 and a reflector 23 are accommodated in a housing 24. The liquid crystal display 22 includes a liquid crystal display element 25, a light emitting element 26, and a case body 27. The liquid crystal display element 25 is obtained by attaching a front polarizing member 31 and a rear polarizing member 32 to the front and rear surfaces of the TFT liquid crystal cell 30, and is supported by a case body 27. The light emitting element 26 is composed of, for example, a white light emitting diode, and is disposed behind the liquid crystal display element 25 to transmit and illuminate the liquid crystal display element 25.

  The reflector 23 includes a reflection mirror 36, a holding member 37, and a stepping motor 38. The reflection mirror 36 is formed by depositing a metal (for example, aluminum) on a resin (for example, polycarbonate) to form a reflection surface 36a. The reflecting surface 36a is a concave surface so that a virtual image is enlarged and displayed. The reflection mirror 36 is bonded to the holding member 37 with a double-sided adhesive tape. The holding member 37 is made of resin (for example, ABS), and the gear portion 40 and the shaft portion 41 are integrally formed. The shaft portion 41 is pivotally supported by the housing 24.

  A gear 42 is attached to the rotating shaft of the stepping motor 38, and the gear 42 is meshed with the gear portion 40 of the holding member 37. The reflection mirror 36 is supported in a rotatable state together with the holding member 37, and the reflection mirror 36 can be rotated by the stepping motor 38 to adjust the projection direction of the display light L. The user operates a push button switch (not shown) to adjust the angular position of the reflection mirror 36 so that the display light L is reflected at the position of the user's eyes (that is, the virtual image can be visually recognized).

  Reference numeral 44 denotes a heat radiating plate, and the heat radiating plate 44 is attached to the rear surface of the light emitting element 26. The heat sink 44 is made of a metal such as aluminum (Al) and has a flat plate shape. Reference numeral 45 denotes a heat radiating member made of a metal such as aluminum (Al). The heat radiating member 45 is disposed in the opening 24 a of the housing 24. The heat radiating member 45 is fixed to the housing 24 by a flange portion 45a with a screw (not shown). A heat radiating plate 44 is bonded to the heat radiating member 45 with a heat conductive adhesive. The heat radiating member 45 has a plurality of heat radiating fins 45b. A packing member 46 closes the space between the heat radiation member 45 and the opening 24 a of the housing 24 to prevent dust from entering the housing 24.

  The housing 24 accommodates the liquid crystal display 22, the reflector 23, and the like. The housing 24 is formed with a window 24b through which the display light L is emitted, and a translucent cover 48 is disposed on the window 24b. The translucent cover 48 is made of a translucent resin (for example, acrylic) and has a curved shape. The housing 24 is provided with light shielding walls 24c and 24d. The light shielding wall 24c is formed so as to hang obliquely from the upper part of the housing 24, and prevents a phenomenon (washout) in which external light such as sunlight enters the liquid crystal display 22 and makes it difficult to see a virtual image. . The light shielding wall 24 d is erected at the lower part of the housing 24.

  Reference numeral 51 denotes an external light sensor such as a photodiode. The external light sensor 51 is mounted on the circuit board 52. The external light sensor 51 mounted on the circuit board 52 is fixed to a holding part that hangs down from the upper part of the housing 24. The external light sensor 51 receives light that has passed through the translucent cover 48, detects the brightness in front of the vehicle, and outputs illuminance data to a microcomputer to be described later. 53 is a cylindrical body, and this cylindrical body 53 is integrally formed with the light shielding wall 24c. The cylindrical body 53 has a substantially cylindrical shape and regulates the angular range of light incident on the external light sensor 51.

  FIG. 2 is a block diagram showing an electrical configuration of the vehicle head-up display device 21. A vehicle speed sensor 58 detects the vehicle speed and outputs vehicle speed data to the microcomputer 59. The microcomputer 59 displays the vehicle speed on the liquid crystal display element 25 via the drive circuit 60 and lights the light emitting element 26 via the drive circuit 64. The microcomputer 59 adjusts the light emission luminance of the light emitting element 26 according to the illuminance data input from the external light sensor 51 via the drive circuit 64.

  Next, an example of the dimming signal output from the microcomputer 59 to the drive circuit 64 will be described with reference to FIGS. In order to prevent the drawings from becoming complicated, in FIG. 4 and FIG. 5, the dimming signal is drawn with the number of pulses (predetermined number) at the predetermined time T being four, but the predetermined number is arbitrary. .

  FIG. 4 shows a dimming signal output from the microcomputer 59 when the emission luminance of the liquid crystal display 21 is gradually increased. The microcomputer 59 sequentially outputs a drive signal S1, a drive signal S2, a drive signal S3, a drive signal S4, and a drive signal S5. The drive signals S1, S2, S3, S4, and S5 have a predetermined number of first pulse signals P1 and second pulse signals P2 at a predetermined time T. That is, the total number of pulses of the first pulse signal P1 and the second pulse signal P2 is always a constant number for a predetermined time T. The first pulse signal P1 is a rectangular wave having a first pulse width W1. The second pulse signal P2 is a rectangular wave having a second pulse width W2 that is larger than the first pulse width W1.

  The drive signal S1 includes only a predetermined number of first pulse signals P1, and the duty ratio of the drive signal S1 is 4/16. In the drive signals S2, S3, and S4 following the drive signal S1, the first pulse signal P1 and the second pulse signal P2 are mixed. In the drive signals S2, S3 and S4, the total number of pulses of the first pulse signal P1 and the number of pulses of the second pulse signal P2 is a predetermined number.

  In the drive signals S2, S3, and S4, the number of pulses of the first pulse signal P1 is gradually decreased, and the number of pulses of the second pulse signal P2 is gradually increased, and the duty of the drive signals S2, S3, and S4 is increased. The ratio is increasing gradually. Specifically, the duty ratios of the drive signals S2, S3, and S4 are 5/16, 6/16, and 7/16. The drive signal S5 includes only a predetermined number of second pulse signals P2, and the duty ratio of the drive signal S5 is 8/16. The duty ratio of the drive signals S2, S3, S4 is larger than the duty ratio of the drive signal S1 and smaller than the duty ratio of the drive signal S5.

  FIG. 5 shows a dimming signal output from the microcomputer 59 when the emission luminance of the liquid crystal display 21 is gradually reduced. The microcomputer 59 sequentially outputs a drive signal S6, a drive signal S7, a drive signal S8, a drive signal S9, and a drive signal S10. The drive signals S6, S7, S8, S9, and S10 have a predetermined number of first pulse signals P1 and second pulse signals P2 at a predetermined time T.

  The drive signal S6 includes only a predetermined number of second pulse signals P2, and the duty ratio of the drive signal S6 is 8/16. In the drive signals S7, S8, and S9 following the drive signal S6, the first pulse signal P1 and the second pulse signal P2 are mixed. In the drive signals S7, S8, and S9, the total number of pulses of the first pulse signal P1 and the number of pulses of the second pulse signal P2 is a predetermined number.

  In the drive signals S7, S8, and S9, the number of pulses of the first pulse signal P1 gradually increases and the number of pulses of the second pulse signal P2 gradually decreases, and the duty of the drive signals S7, S8, and S9 is decreased. The ratio is progressively smaller. Specifically, the duty ratios of the drive signals S7, S8, and S9 are 7/16, 6/16, and 5/16. The drive signal S10 includes only a predetermined number of first pulse signals P1, and the duty ratio of the drive signal S10 is 4/16. The duty ratio of the drive signals S7, S8, S9 is smaller than the duty ratio of the drive signal S6 and larger than the duty ratio of the drive signal S10.

  In the present embodiment, the duty ratio can be gradually changed by the drive signals S2, S3, S4 or the drive signals S7, S8, S9, and smooth dimming is possible. In particular, when the vehicle head-up display device 21 is used at night, the light emission luminance of the liquid crystal display 22 must be extremely small. Therefore, even a slight change in the light emission luminance is abrupt for a vehicle driver. Therefore, it is preferable to gradually change the duty ratio as in the present embodiment.

  FIG. 6 shows a comparative example. The drive signals U1, U2, U3, U4, and U5 have a predetermined number of first pulse signals P1 and second pulse signals P2 at a predetermined time T. The drive signals U1 and U2 consist only of a predetermined number of first pulse signals P1, and the duty ratio of the drive signals U1 and U2 is 1/4. The drive signals S3, S4, S5 following the drive signals S1, S2 are composed of only a predetermined number of second pulse signals P2, and the duty ratio is 2/4. In the comparative example, the duty ratio changes abruptly at the boundary between the drive signal U2 and the drive signal U3.

  The present embodiment is a vehicle head-up display device 21 that includes a liquid crystal display (light-emitting display) 22 and a control unit 59 that adjusts the light emission luminance of the liquid crystal display 22 by a dimming signal. The control means 59 includes a first drive signal S1 composed of a first pulse signal P1 having a first pulse width W1, and a second pulse signal P2 having a first pulse signal P1 and a second pulse width W2. Output a dimming signal including a second drive signal S2, S3, S4 mixed with a third drive signal S5 composed of a second pulse signal P2, and gradually changes the duty ratio. And smooth dimming is possible.

  In addition, this invention is not limited to this embodiment, A various deformation | transformation is possible. For example, in the present embodiment, the light emission luminance of the light emitting element 26 is adjusted via the drive circuit 64, but the drive circuit 64 may be omitted, and the light emitting element 26 is directly driven by the microcomputer 59. Also good. The light emitting display may be an organic EL display panel or a fluorescent display tube.

21 Vehicle head-up display device (display device)
22 Liquid crystal display (light emitting display)
59 Microcomputer (control means)
W1 First pulse width W2 Second pulse width P1 First pulse signal P2 Second pulse signal S1 First drive signal S2 Second drive signal S3 Second drive signal S4 Second drive signal S5 Second Third drive signal S6 Third drive signal S7 Second drive signal S8 Second drive signal S9 Second drive signal S10 First drive signal T Predetermined time

Claims (4)

A light-emitting display, and control means for adjusting the light emission luminance of the light-emitting display with a dimming signal,
The control means includes a first drive signal composed of a first pulse signal having a first pulse width and a second pulse signal having a mixture of the first pulse signal and a second pulse signal having a second pulse width. And a third drive signal composed of the second pulse signal. The display device outputs the dimming signal. The first drive signal at a predetermined time consists of a predetermined number of the first pulse signals,
The second drive signal at the predetermined time following the first drive signal is the sum of the number of pulses of the first pulse signal and the number of pulses of the second pulse signal is the predetermined number,
The display device according to claim 1, wherein the third drive signal at the predetermined time following the second drive signal includes the predetermined number of the second pulse signals. The third drive signal at a predetermined time consists of a predetermined number of the second pulse signals,
The second drive signal at the predetermined time following the third drive signal is the sum of the number of pulses of the first pulse signal and the number of pulses of the second pulse signal is the predetermined number,
2. The display device according to claim 1, wherein the first drive signal at the predetermined time following the second drive signal includes the predetermined number of the first pulse signals.   2. The display device according to claim 1, wherein in the second drive signal, a ratio between the number of pulses of the first pulse signal and the number of pulses of the second pulse signal gradually changes.

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