KR20000075112A - Electron gun for color crt - Google Patents

Abstract

PURPOSE: An electron gun for a color CRT(Cathode Ray Tube) is provided to regulate astigmatism through a main lens by applying a fine dynamic focusing electrode to three electron beams and to compensate an asymmetric fine Halo on a screen. CONSTITUTION: An oval electron beam hole(21a) is formed on a constant voltage focusing electrode(21) to make three electron beams pass. Two and more guide inner electrodes(23,24) are formed in the focusing electrode(21) wherein outer electron beam holes(23a,23c,24a,24c) are arranged asymmetrically like a polygon. Plural circular electron beam holes(22a) are formed on a variable voltage focusing electrode(22). A compensation electrode(25) is fixed on the circular hole(22a) to insert a horizontal planar electrode(25a) into the oval electron beam hole(21a). A fine halo is compensated through the asymmetric structure of the electron beam holes and the same voltage is fed to each point of the three electron beams.

Description

Electron gun for color cathode ray tube {electron gun for color CRT}

The present invention relates to an electron gun used in a large color cathode ray tube or a high-definition industrial monitor, and more particularly, to a focusing electrode of an electron gun that improves resolution at the periphery of a screen by correcting astigmatism according to the deflection amount of an electron beam. It is about.

1 is a partial longitudinal sectional view showing a schematic configuration of a general color cathode ray tube, in which red, green, and blue phosphors are applied to an inner surface of a panel 1 to form a phosphor layer 2, and to the rear of the panel 1; The funnel 3 in which the electron gun 4 is sealed to the neck portion 3a is fused to maintain a high vacuum inside.

A shadow mask 6, which serves as color screening of the electron beam 5 emitted from the electron gun 4, is fixed to the support frame 7 at a portion adjacent to the phosphor layer 2 coated on the inner surface of the panel 1. And a deflection yoke 8 is provided on the outer circumferential surface of the funnel for deflecting the electron beam emitted from the electron gun in the vertical or horizontal direction.

The stem 9 is fixed to the rear of the electron gun, that is, the end of the neck portion 3a to be exposed to the outside, so that a voltage is applied to each electrode of the electron gun through a plurality of stem pins 10 fixed to the stem. .

Fig. 2 is a schematic view showing a conventional BPF type electron gun, wherein the electron gun is composed of a triode and a main lens portion.

The three-pole portion has three heaters 12, each of which is a heat source and emits thermal electrons, are arranged horizontally independently of each other, and are arranged to maintain a predetermined distance from the cathode to control hot electrons generated from the cathode. The control electrode 13 and the acceleration electrode 14 arranged to maintain a predetermined distance from the control electrode and serves to accelerate the hot electrons that are collected on the surface of the electron-emitting material of the cathode (not shown) to accelerate. .

The main lens unit is composed of a focusing electrode 15 and an anode 16 for focusing and finally accelerating the electron beam generated in the triode.

Therefore, when the heater 11 embedded in the cathode 12 receives power from the stem pin 10 and generates heat, the heater 11 is separated from the cathode by a heat difference generated by the heater and a voltage difference applied to a plurality of electrodes adjacent to the cathode 12. Electrons are emitted, and the emitted electron beam 5 is accelerated and focused by the potential difference between these electrodes to pass through the holes of a plurality of electrodes which are spaced at regular intervals vertically from the cathode 12 in the screen direction to reach the screen. do.

If the electron beam 5 emitted from the cathode 12 reaches the screen in more detail as follows.

The electron beam 5 emitted from the cathode 12 of the electron gun 4 is appropriately controlled and accelerated in a beam forming region composed of the control electrode 13, the acceleration electrode 14, and the focusing electrode 15. Then, the light is focused and accelerated by an electrostatic lens formed by a voltage difference applied to the focusing electrode 15 and the anode 16 to proceed to the screen side.

At this time, the control electrode 13 is grounded, a low voltage of about 500 to 1000 V is applied to the acceleration electrode 14, a high voltage of about 25 to 35 KV is applied to the anode 16, and the focusing electrode 15 is applied. ), An intermediate voltage corresponding to 20 to 33% of the voltage applied to the anode 16 is applied.

The electron beam passing through the electrostatic lens, which is the main lens of the electron gun, is formed by the intensity of the electric current applied to the deflection yoke 8 surrounding the lower end of the outer shell of the funnel 3 and the upper end of the neck 3a. The path is determined by the influence of the magnetic field.

The electron beam 5 traveling along the path determined by the intensity of the current applied to the deflection yoke 8 passes through the holes of the shadow mask 6 provided in proximity to the fluorescent film 2 and then impinges on the phosphor layer. The screen is reproduced by emitting the phosphor.

In the electron gun operating as described above, as a predetermined voltage is applied to each electrode, an electrostatic lens is formed by a potential difference applied to the focusing electrode 15 and the anode 16 to form an electron beam generated at the triode in the center of the screen. Focusing.

At this time, in order to reproduce an image, the electron beams 5 must be sequentially scanned on each area of the screen, and for this purpose, the electron beams must be deflected to the entire area of the screen.

In general, in the color cathode ray tube using the inline electron gun 4, three electron beams of red, green, and blue (R, G, B) are arranged side by side horizontally so that a non-uniform magnetic field is applied to converge each electron beam in one place of the fluorescent surface. A self convergence type deflection yoke 8 is applied.

As shown in FIGS. 3A and 3B, the magnetic field distribution generated by the deflection yoke 8 to which the self-focusing type is applied, the horizontal deflection field is a pin cushion type, and the vertical deflection field is a barrel type. This allows the mis-convergence to be corrected at the periphery of the fluorescent surface.

However, as illustrated in FIGS. 3C and 3D, each magnetic field can be described by dividing the bipolar component and the quadrupole component. The bipolar component serves to deflect the electron beam in the horizontal and vertical directions, and the quadrupole component is the electron beam. Is focused in the vertical direction and diverges in the horizontal direction, causing the electron beam in the vertical direction to focus at a shorter distance than the electron beam in the horizontal direction, causing a halo phenomenon in which the vertical direction of the electron beam rises convexly on the screen. Therefore, deterioration of image quality is caused.

4A and 4B show in more detail how distortion of the electron beam spot appears on the screen.

4A and 4B, since the deflection magnetic field is not applied at the center of the screen, the electron beam spot has a circular shape, but in the periphery thereof, as described above, the electron beam spot diverges in the horizontal direction and is over-condensed in the vertical direction. Since the horizontal core 17 and the halo 18, which are upper and lower portions of the upper and lower regions, are deteriorated, the resolution is degraded at the periphery of the screen.

FIG. 5A illustrates the principle that the electron beam spot represented by the deflection yoke causes astigmatism without being focused at the periphery of the screen.

Even if the magnetic field is close to uniform, the electron beam spot is distorted by astigmatism due to the fine pin cushion or barrel magnetic component. Therefore, it is natural that the electron beam spot is distorted at the periphery of the screen when the non-uniform magnetic field is adopted.

In addition, this problem becomes more severe as the color cathode ray tube is larger and the larger the angle of deflection is, and it is necessary to solve the problem in consideration of the tendency of consumers who prefer a large cathode ray tube and the increase in the size of the cathode ray tube. It is one of the tasks to be done.

In order to solve the above problems, the quadrupole component is generated by the electron gun 4 to cancel the quadrupole component generated by the self-focusing deflection yoke 8 so that the electron beam components in the horizontal and vertical directions can be simultaneously focused at one point. have.

That is, a splitting of the focusing electrode 15 into a first focusing electrode and a second focusing electrode is performed by dividing the focusing electrode 15 into a quadrupole lens, and generating a potential difference on the four-pole electrode such that a dynamic quadrupole lens is formed between the electrodes. By doing so, astigmatism can be corrected.

However, the electron beam 5 is focused in front of the screen at the periphery due to the difference in the electron beam moving distance between the center of the screen and the periphery, and still exhibits a halo phenomenon.

Therefore, to solve this problem, when the electron beam 5 is deflected to the periphery of the screen, the electrostatic lens is controlled by applying a dynamic voltage (variable voltage) synchronized with the deflection frequency to weaken the power of the main lens and to adjust the focusing distance of the electron beam. The method of correcting the astigmatism of is mainly applied.

The astigmatism correction means according to the prior art will be briefly described with reference to FIGS. 6 to 8 as follows.

6 to 8 show astigmatism correction means shown in U.S. Patent No. 5,061,881 of Matsushita, Japan.

The focusing electrode of the astigmatism correction means is divided into a first focusing electrode 19 and a second focusing electrode 20.

The second focusing electrode 20 faces the anode 16 side, and the first focusing electrode 19 faces the second focusing electrode 20.

Longitudinal rectangular electron beam passing holes 19a, 19b, 19c are formed in the first focusing electrode 19, and second rectangular electrode beam passing holes 20a, 20b are formed in the second focusing electrode 20. A plurality of 20c's are formed to form a quadrupole lens therebetween so as to correct astigmatism occurring at the periphery of the screen.

That is, since the electron beam generated in the triode portion, which is the electron beam forming region, passes through the first focusing electrode 19 and the second focusing electrode 20, which are divided into two, and is focused on the main lens, an image is formed on the screen.

In particular, when the electron beam is deflected to the periphery of the screen, the voltage applied to the first focusing electrode 19 is fixed at a constant, but the voltage applied to the second focusing electrode 20 is synchronized to change in accordance with the deflection amount of the electron beam. Therefore, the quadrupole lens is operated by the quadrupole electrode.

In general, the larger the cathode ray tube or the larger the deflection angle, the higher the voltage is applied to the second focusing electrode 20 than the first focusing electrode 19.

The voltage applied to the second focusing electrode 20 is supplied as a parabola waveform in a circuit of a TV or a monitor, and is generally applied at about 300 to 1000 V higher than the voltage applied to the first focusing electrode 19. .

When a voltage is applied to the second focusing electrode 20, a quadrupole lens operates due to a difference between the voltage applied to the first focusing electrode 19 and the voltage applied to the second focusing electrode 20. The spot shape of the electron beam changes into an elongated shape, and thus acts in the direction of improving the halo 18, which is the periphery of the periphery generated by the non-uniform magnetic field of the deflection yoke 8 through the main lens.

FIG. 5B is an explanatory diagram when a quadrupole lens is applied to improve the spreading in the periphery of a conventional screen. The deflection yoke astigmatism is compensated by the quadrupole lens while maintaining the same focusing force of the main lens. It shows the state.

The horizontal lens of the 4-pole lens focuses the horizontal direction of the electron beam having a constant divergence angle at the triode by the deflection yoke 8, and the 4-pole lens by the amount of vertical focusing by the deflection yoke. The vertical lens is configured to emit in the vertical direction.

To this end, a main lens weakening component (dynamic voltage) is required. The main lens weakening component focuses an electron beam at an arbitrary position around the screen which requires a coincidence electron beam in the horizontal and vertical directions as shown in FIG. 5B. It serves to match in the vertical direction.

With such a suitable quadrupole lens and dynamic voltage, the electron beam can be optimally focused at the periphery of the screen.

As described above, in recent years, dynamic electron guns have been developed to compensate for the deterioration of the electron beam spot due to the larger deflection force toward the screen portion due to the larger size and higher definition of the cathode ray tube. However, the conventional electron gun has three electron beams. It is a situation that the fine halo phenomenon (FIG. 9B) by the deflection force difference (FIG. 9A) of the electron beam deflected from the outer side and the electron beam deflected from the inside cannot be correct | amended.

At this time, the fine halo size on the right side of the screen is B <G <R, and the fine halo size on the left side of the screen is R <G <B.

In the case of a deflection yoke using a non-uniform magnetic field, as shown in FIG. 9A, the deflection force becomes larger toward the periphery of the screen so that the three electron beams show a difference in deflection force with respect to each other. Since they cannot be corrected for each, fine halo phenomena occur at the periphery of the screen.

In addition, the problem of dynamic implementation is that there is a considerable difficulty in fine tuning and requires a high technical accumulation in the manufacturing process to obtain the desired characteristics.

The present invention has been made to solve such a problem in the prior art, by applying a focusing electrode capable of fine dynamic adjustment between the three electron beams to facilitate the adjustment of the astigmatism possible by the adjustment of the main lens and at the same time fine adjustment is possible. The purpose of the present invention is to improve the fine halo generated asymmetrically on the left and right sides of the screen, which could not be compensated by the existing dynamic action.

According to an aspect of the present invention for achieving the above object, a three-pole portion consisting of a plurality of cathodes for emitting an electron beam, a control electrode and an acceleration electrode for adjusting the radiation amount of the electron beam, and a main lens for focusing the electron beam on the screen A focusing electrode to be formed and an anode for ultimately accelerating the electron beam are arranged inline, and the focusing electrode is divided to form a constant voltage applied to one focusing electrode of the divided focusing electrodes and synchronized with a deflection current to the other focusing electrode. In a color cathode ray tube electron gun in which a dynamic quadrupole lens is formed between the divided focusing electrodes when a variable voltage is applied, three electron beams are common to a fixed voltage focusing electrode located on an opposite surface of the variable voltage focusing electrode. An elliptical electron beam passing hole is formed to pass through, and an outer portion of the fixed voltage focusing electrode is formed outside. Two or more guide inner electrodes having a polygonal left and right asymmetrical beams are provided, and a plurality of circular electron beam passing holes are formed in the variable voltage focusing electrode positioned on the opposite surface of the fixed voltage focusing electrode, and the circular electron beam passing through A correction electrode having a horizontal plate electrode protruding in the vertical direction with respect to the flat surface is fixed to the upper and lower portions of the ball so that the horizontal plate electrode of the correction electrode is inserted into the elliptical electron beam through hole formed in the fixed voltage focusing electrode. An electron gun for color cathode ray tubes is provided.

1 is a partial longitudinal cross-sectional view showing a schematic configuration of a general color cathode ray tube;

2 is a schematic view showing the configuration of a conventional electron gun

3A to 3D illustrate distortion of an electron beam spot due to a non-uniform magnetic field of a self-focusing deflection yoke.

3A is a distribution diagram of a pin cushion type horizontal deflection magnetic field

3b is a distribution diagram of a barrel-type vertical deflection magnetic field;

3C is an exploded explanatory diagram of the dipole and quadrupole components of a pincushioned horizontal deflection magnetic field;

3D is an exploded explanatory diagram of the dipole and quadrupole components of the barrel-type vertical deflection magnetic field;

4A and 4B show the shape of a distorted electron beam spot on a conventional color cathode ray tube screen.

5A and 5B are schematic diagrams for explaining the principle of astigmatism generation at the periphery of the screen caused by the deflection yoke.

6 is a longitudinal sectional view showing conventional astigmatism correction means;

7 is a front view showing a conventional first focusing electrode

8 is a front view illustrating a conventional second focusing electrode;

9A and 9B illustrate a difference in deflection force when the electron beam is deflected, and thus a fine halo phenomenon.

10 is a longitudinal sectional view showing an embodiment of the present invention.

11 is a front view showing a fixed voltage focusing electrode of the present invention.

12A and 12B are perspective views of a correction electrode fixed to the variable voltage focusing electrode

13A to 16B are front views showing an embodiment of a guide inner electrode applied to the present invention.

17A to 17C are graphs showing simulation results of the present invention.

18A and 18B are graphs showing the relationship between astigmatism and L in the present invention.

Explanation of symbols for main parts of the drawings

21: fixed voltage focusing electrode 21a: electron beam through hole

22 variable voltage focusing electrode 23 first guide inner electrode

24: second guide inner electrode 25: correction electrode

25a: horizontal flat electrode

23a, 23c, 24a, 24c: outer electron beam passing hole

Hereinafter, the present invention will be described in more detail with reference to FIGS. 10 to 18 as an embodiment.

FIG. 10 is a longitudinal sectional view showing an embodiment of the present invention, FIG. 11 is a front view showing a fixed voltage focusing electrode, and FIGS. 12A and 12B are perspective views of a correction electrode fixed to the variable voltage focusing electrode.

The present invention improves the fine halo caused by the deflection position difference between the three electron beams through the asymmetry correction of the quadrupole lens, and enables fine adjustment of the astigmatism without affecting the shape of the main lens, which has not been realized in the prior art. In one embodiment, it is disposed after the tripolar portion, which is an electron beam forming portion for generating three electron beams, and serves to focus the electron beam.

The focusing electrode of the present invention comprises a first focusing electrode (hereinafter referred to as " fixed voltage focusing electrode ") 21 to which a fixed voltage is applied, and an electron beam disposed by the deflection yoke 8 next to the fixed voltage focusing electrode. And a second focusing electrode 22 (hereinafter referred to as a " variable voltage focusing electrode ") to which a variable voltage which is variable according to the deflection amount is applied.

An elliptical electron beam through-hole 21a through which three electron beams as shown in FIG. 11 pass in common is formed in the fixed voltage focusing electrode 21 positioned on the opposite surface of the variable voltage focusing electrode 22. The first guide inner electrode 23 having an elongated rectangular electron beam through hole 23b through which the central electron beam passes and an elongated outer electron beam through hole 23a and 23c having asymmetric left and right inside the electrode 21. Is fixed, and the electron beam passing holes 24a, 24b, 24c having the same shape as the first guide inner electrode 23 are opposite to the elliptical electron beam passing holes 21a formed in the fixed voltage focusing electrode 21. The formed second guide inner electrode 24 is fixed.

The asymmetric electron beam through holes 23a, 23c, 24a, and 24c positioned at the outer side of the electron beam through holes formed in the first and second guide inner electrodes 23 and 24 are vertically shown in FIG. 13A. As shown in FIG. 14A and FIG. 15A, polygonal as shown in FIGS. 14A and 15A, circular shape added to the trapezoid as shown in FIG. 16A, or arcs in the center of the structure of FIGS. 13A, 14A, 15A and 16A. 13B, 14B, 15B, and 16B have a keyhole-like structure, which exhibits the same characteristics.

A plurality of circular electron beam through holes 22a, 22b, 22c are formed in the variable voltage focusing electrode 22 facing the fixed voltage focusing electrode 21, and a flat surface is formed on one side of the variable voltage focusing electrode. The correction electrode 25 on the square plate having the horizontal flat electrode 25a protruding perpendicularly to is fixed so that the horizontal flat electrode is located inside the electron beam through hole 21a formed in the fixed voltage focusing electrode 21. The correction electrode 25 has a circular electron beam through hole 25b.

However, the circular electron beam through hole 25b formed in the correction electrode 25 may be formed as a horizontal rectangular electron beam through hole instead of a circle.

The quadrupole lens formed between the fixed voltage focusing electrode 21 and the variable voltage focusing electrode 22 of the present invention is operated by a potential difference when the fixed voltage is about 300 to 1,000 V lower than the variable voltage, and the electron beam of the screen The astigmatism is corrected by generating a corrected magnetic field in the quadrupole lens as much as the astigmatism generated when deflected to the peripheral portion, which will be described in detail below.

First, the voltage of each part of the screen (Center: Center, Top: Top, Edge: Edge, Corner: Corner) in the non-dynamic state is measured.

Here, the non-dynamic state means when a voltage having the same magnitude is simultaneously applied to the fixed voltage focusing electrode 21 to which the fixed voltage is applied and the variable voltage focusing electrode 22 to which the variable voltage is applied.

In this way, if the voltage of each part is measured on the non-dynamic screen, the horizontal focus voltage at each point remains almost constant, but the focus voltage in the vertical direction changes exponentially in the order of center, top, edge, and corner. do.

Therefore, the astigmatism component to be improved here is related to the vertical direction. Since the voltage difference between the center and each part becomes the aberration component of the deflection yoke of each part to be finally improved, a quadrupole lens corresponding to this component is constructed to determine the deflection yoke. What is necessary is to improve aberration components.

At this time, each of the electron beam passing holes 23a, 23b, 23c of the first guide inner electrode 23 of the fixed voltage focusing electrode 21 constituting the quadrupole lens is related.

In other words, the larger the vertical hole is, the stronger the quadrupole lens is, and the smaller the proportion is, the weaker the proportion is.

However, in the electron gun, a path difference is generated between the three electron beams in the deflection phase, and minute astigmatism components are generated as shown in Fig. 9A, but the conventional quadrupole lens cannot remove such fine astigmatism.

That is, even when the electron beam is deflected in the right direction, as shown in 9a, the electron beam on the right has a fine deflection yoke astigmatism due to the stronger deflection force.

However, according to the present invention, the left and right sides of the electron beam passing holes 23a, 23c, 24a, and 24c formed in the outer side of the first and second guide inner electrodes 23 and 24 are asymmetrical to allow the outer electron beam to pass therethrough. Since the micro deflection yoke astigmatism generated when the electron beam is deflected to the outside forms an asymmetric quadrupole lens with a different amount, the fine astigmatism of the outer electron beam is canceled out.

The second guide inner electrode 24 fixed to one end of the fixed voltage focusing electrode 21 maintains a predetermined distance from the first guide inner electrode 23 as shown in FIG. Fine correction of astigmatism by (L) is possible.

17A to 17C show detailed simulation data of the present invention, and the graphs of FIGS. 18A and 18B show the relationship between the distance L of astigmatism in the above structure.

When such a structure is applied, only a very fine astigmatism can be corrected without affecting other parts including the main lens in the fine astigmatism correction, thereby enabling a much higher quality than the conventional art.

In addition, the peripheral convergence error caused by the lowering of the convergence force of the outer electron beam generated when the voltage of 300 to 1,000 V is applied to the variable voltage focusing electrode 22 more than the fixed voltage focusing electrode 21 is prevented. 2 The greater the vertical width of the outer electron beam passing holes 24a and 24c formed in the guide inner electrode 24, the greater the overconvergence, and under the opposite case, the underconvergence.

In order to improve this, the vertical force of the outer electron beam passing holes 24a and 24c formed in the second guide inner electrode 24 is asymmetric to adjust the action force.

In addition, in order to strengthen the action of the four-pole lens, the horizontal flat electrode 25a of the correction electrode 25 may be configured as shown in FIG. 12B. It is understood that even the shape of the electrode makes it possible to construct a stronger quadrupole lens.

As described above, the present invention provides the first and second guide inners installed in the fixed voltage focusing electrode 21 for the generation of minute astigmatism of the deflection yoke with respect to the outer electron beam of the variable voltage focusing electrode 22 of the conventional electron gun. The shape of the outer electron beam through holes 23a, 23c, 24a, and 24c of the electrodes 23 and 24 is asymmetrical in shape to improve the fine halo generated at the periphery of the screen. At each point of, the same applied voltage is induced.

In addition, by adjusting the shape and spacing of the outer electron beam through holes formed in the first and second guide inner electrodes 23 and 24, it is possible to solve the miss convergence generated at the periphery of the screen without applying a high voltage. The voltage can be reduced.

Claims (6)

A three-pole portion comprising a plurality of cathodes emitting an electron beam, a control electrode and an acceleration electrode for adjusting the radiation amount of the electron beam, a focusing electrode forming a main lens for focusing the electron beam on a screen, and an anode for finally accelerating the electron beam Arranged in-line, and when the focusing electrode is divided to apply a constant voltage to the focusing electrode on one side of the divided focusing electrodes and a variable voltage in synchronization with the deflection current is applied to the focusing electrode on the other side between the divided focusing electrodes An electron gun for a color cathode ray tube in which a dynamic quadrupole lens is formed in an ellipsoidal electron beam through-hole, in which three electron beams pass in common to a fixed voltage focusing electrode positioned on an opposite surface of the variable voltage focusing electrode, and the fixed voltage focusing is performed. Inside the electrode, the outer electron beam passing hole is polygonal and asymmetrical Two or more inner inner electrodes are provided, and a plurality of circular electron beam through holes are formed in the variable voltage focusing electrode positioned on the opposite surface of the fixed voltage focusing electrode, and the upper and lower portions of the circular electron beam through holes are perpendicular to the flat surface. An electron gun for a color cathode ray tube, characterized in that a correction electrode having a horizontal flat electrode protruding into the fixed electrode is inserted into the elliptical electron beam through hole formed in the fixed voltage focusing electrode. The method of claim 1, An electron gun for a color cathode ray tube, characterized in that the electron beam passing hole of the guide inner electrode provided inside the fixed voltage focusing electrode has an elongated shape. The method of claim 2, The electron gun for the color cathode ray tube, characterized in that the outer hole of the electron beam through hole of the guide inner electrode fixed in the fixed voltage focusing electrode has a trapezoidal shape. The method of claim 2, Electron gun for the color cathode ray tube, characterized in that the outer hole of the electron beam through hole of the guide inner electrode fixed inside the fixed voltage focusing electrode has a circular shape added to the trapezoid. The method according to any one of claims 1, 3, and 4, An electron gun for a color cathode ray tube, characterized in that the electron beam passing hole formed in the guide inner electrode has a keyhole shape having an arc at a central portion thereof. The method of claim 1, And a pair of horizontal flat electrodes formed on the correction electrode are not parallel to each other and are formed at an acute angle with respect to the flat surface.