JPS5973801A - Illuminating method and device utilizing external light - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a lighting method that efficiently utilizes outdoor light and reduces power consumption for lighting when implementing indoor lighting.

[Prior art]

It has been a long time since energy conservation has been taken up as a technical issue, but
Various proposals have been made regarding indoor lighting. One of these is the use of outside light that enters through windows. 1st
The figure shows the situation in a typical indoor room. Direct sunlight entering as outside light is at the height of the window G from the floor F, and when the angle of incidence is 01, the direct sunlight enters the floor F. The arrival IJISO of the applied sunlight B becomes HO-cotθ1.

At this time, the illuminance near the window may reach several thousand lux, and when the reach range SO goes to room noise, the illuminance drops drastically by ≠2, which interferes with normal visual work.

However, it is normal for sparrows to make up for this shortage with artificial lighting. As a means of compensating for this, it is possible to efficiently blink or dim artificial lighting by installing a sensor indoors and capturing the signal, for example,
-20068, etc. however,
On the other hand, near windows where sunlight hits directly, the illuminance may be too high, and the reflected light on the viewing work surface due to the rays of sunlight may be too strong, so it is difficult to use blinds or blinds for the incident light. The incidence is restricted by curtains, etc. the result,
The amount of light that enters through windows decreases, while the amount of light from artificial lighting increases, leading to an overall problem of increased energy waste.

[Purpose of the invention]

By the way, unless the window area is particularly small or the depth of the room (C) is large, in general, the sunlight that enters through the window can be averaged in fractions of the amount of light that enters the entire room). You can cover most of it. Therefore, the uninvented method actively brings sunlight into the room, which was previously restricted, and uses it as indoor lighting.In particular, the conventional method 1 aims to reverse the blinds, which were intended to block light, to let in sunlight. and 1. It is located where you are trying to use it.

[Summary of the invention]

In other words, in the uninvented state, the slab is used as a reflector for the large amount of sunlight emitted by the entire blind, and the slat surface is used to directly direct the sunlight toward the ceiling, and the ceiling is used as a tertiary reflecting surface to serve as a kind of pseudo-7 top light source. The idea is to diffuse the reflected sunlight throughout the room. Furthermore, in order to efficiently reflect this sunlight indoors, we know the conditions of outside light, including sunlight, and control the slope of the blind slats based on that information. The aim is to achieve a homogeneous and comfortable lighting environment as a whole by controlling lighting lights installed on the ceiling, etc., to blink or dim.

[Embodiments of the invention]

Figure 2 shows an example in which blind B is used to bring in sunlight into the room, and LA7 is used.
'C and enters the ceiling surface C.

Similarly, the lower end sunlight Ln reflected by the lower end slit Rn of the pre-indo B enters the incident point On on the ceiling surface C. The distance T of this incident point On from the outer wall can be made larger than the reach distance S0 of the upper end sunlight. This means that the lower solar light Ln is smaller by the angle of its inclination.
Since they are the same, the reflection angle θr should be made smaller fl,
It can be seen that as a result, the receding light L' reaches the ceiling surface C-1 at the back of the interior. Ceiling surface C is designed for a general office, etc., and the drawing table is made of rock end plate, hardwood, etc., and is painted white.
A chain of about 7 to 09 can be expected. Also, most painted surfaces in general are close to perfect diffusion surfaces, so the reflected light incident on this ceiling surface is diffusely reflected by all the trees in the room, and is conventionally expressed as m2.
．． Compared to the case 11 in Figure 1, the entire room is illuminated relatively uniformly.

As the blind B used at this time, for example, the sixth
A configuration like the one shown in the figure is conceivable. Hanawa 6
In the figure, R1 is a concave slat consisting of a downwardly convex curved surface, and this concave surface is finished with a high reflectance and good directivity in reflection, for example, a mirror surface. Further, M, , M are hanging tools for supporting and operating the concave slat Ri, for example, the first
If the hanging tool M1 is on the window side, and the second hanging tool M is all on the inside of the room,
By fixing one side and movable the other, you can
It is possible to change the slope of Soto R1. This state is shown in FIG. That is, by tilting the concave slat Ri, the incident sunlight changes more than the tilt. Therefore, it is possible to send the reflected light L' to the back of the room with a slight change in inclination.

The 2"9 slit shown in FIG. 5 is a convex slit Rf consisting of an upwardly convex curved surface. In this case, the reflected light L' from one slat is dispersed and reflected over a wide range V on the ceiling surface. Of course, Although not shown, flat slats can also be used.In the case of flat slats, the reflected light can be obtained by the width of the 7'Iz slats, so install a special diffuse reflection surface on the ceiling surface to reflect it back into the room. If so, it is convenient.

By the way, when the slit is used as a reflector to reflect the reflected light to the ceiling surface, the m of the incident sunlight is
The direction of reflected light changes depending on the

Furthermore, since a plurality of slats are provided one on top of the other, the upper slit may get in the way depending on the angle of incident light. ≠: In order to efficiently bring sunlight into the room throughout the year, it is necessary to change the inclination of the slit depending on the position of the sun. Of course, since the angle of incident light changes depending on the height of the sun, it goes without saying that this change should also be accommodated.

Diagram 6 shows the incidence of the great sunlight on the G, where 0 indicates the center of the G. 1. TELβru.

In other words, the great sunlight L (, well, enters with a three-dimensional inclination to the fortune-telling ○. The fj of this great sunlight is divided into the fortune-telling O of the window G by the law whip NE and this normal N. a horizontal plane containing;
Fixation (a straight line connecting fortune telling O and the sun, that is, the center of the sun ≠・ line segment P that fully intersects the vertical plane containing the great sunlight heading towards point O
Considering this, the height angle θS is the ladle formed by this line segment P and Ohma i light.
, glandular P and law? The angle formed by FI4t1g is the horizontal angle (expressed as j-1 sunlight L'7')ff2 is the solar azimuth angle %Cθ9. This solar azimuth angle α(θS, φ)i is known as the value shown by the state W@ in which the i window G is completely oriented toward one direction, and in fact, it is Directly facing the southern part of the city [7] If you are unable to advise, you need to compensate for the #i difference.In this way, the slats of the blind reflect one part of the sun and bring it indoors.
The inclination of the slats must be determined by taking into consideration the four-way window to be taken in, the direction of the window, and the solar angle.

By the way, when sunlight is brought into the room by reflection from the slit of this blind and used for visual work, the optimum reflection angle determined by the curvature of the slit can be considered. Reflection angle 0rli,
Experiments, lighting theory, etc. can be used to set an angle that satisfies the conditions of reflecting sunlight onto the ceiling at the back of the room as much as possible and not giving unpleasant reflected glare to occupants. Once this optimum reflection angle θr is obtained, the inclination angle of the slit shown in FIG. 7, that is, the slat angle θb, can be determined by the following equation using the altitude angle θS of the sun. In addition, h? f''
The horizontal line is the normal line at the N-tangent @ l Vc.

θb=θS-θr...between songs...between songs...(1
) Since the optimum reflection angle θr takes a special foot chain, the slat angle Eb is proportional to the solar altitude angle θS as seen from equation (1). In other words, during daylight hours, the sun's high expansion angle θS changes every hour, so the slit angle θb needs to be controlled to follow the changes.Also, the position of the blind is generally parallel to the window. The solar azimuth angle α (θS, φ) is fixed with respect to the horizontal angle φ, and the altitude angle σs
Only K is controlled.

Figure 81 shows the original construction of the room used for the experiment. In the figure, H8 is the ceiling height, W is the frontage, D is the depth, Hl is the height of the window G, and W is the width of the window G. Dimension H, = 2.7
m%'#, -5,0m, DI=9.0m, H,
-1.6 m, W# = 3.6 rn, reflectance is ceiling f
+: 0.8, wall is 0.5, phase is 03. This room d is directly facing window G9m. Jiho using this part 1R,
The fruit is shown in Figure 9.

14) It was conducted at noon on a sunny day in June. In the figure, the song Gravel X is when no blind is used, and the song @Y is the blind t of the concave slat with a mirror reflective surface according to the present invention - the floor surface F with a soft sail tilted to the optimal condition. It shows the illuminance. That is, in the vicinity of the window, 3. Although more than υυυ lux can be obtained, about 1,000 lux is sufficient for general visual work. Therefore, by using blinds to disperse the illuminance, the illuminance was rapidly decreasing, which would become less than 1,000 lux at about 3.5 m if the blinds were not used for one day.
It is possible to obtain high illuminance even in the back of a room. If the required horizontal illuminance is 1.0001 Vx, the only shortfall when using blinds is the shaded part of the room.
Compared to the case where blinds are not used, the amount of auxiliary lighting using lamps is significantly reduced, and it is possible to save power for lighting. The auxiliary illumination provided by the illumination lamp may be controlled to supplement the necessary amount using a lighting sensor.

FIG. 10 shows the overall system of the present invention, which uses blinds and illumination lights to ensure the necessary illuminance in a room. In the figure, 1 is a window, and 2 is a blind installed close to the inside of the window 1 to let in sunlight. The blind 2Fi slider 21 is equipped with a fixed side hanging cord 22 and a movable side hanging cord 23, and is provided with an operating rope (not shown) for hoisting and lowering the entire blind 1. Reference numeral 24 denotes a blind drive means for operating the blind 1, which includes an electric motor, a movable hanging cord 23t, a drum for winding and adjustment, a drum for winding up a mesh for operation, etc. 13 detects the solar azimuth angle α The solar azimuth angle recognition means, for example, uses a fisheye lens to focus it on a two-dimensional optical sensor with an XY specification method, such as an MO81'E6 image sensor or a CCD type image sensor, and converts it from the position of the solar image. It is used to obtain the azimuth angle. Note that the solar azimuth angle α varies depending on the latitude of the region, the calendar date, and the time, but since the solar azimuth angle α for each day of the year has a fixed value, the value for the region is used as the solar azimuth angle. If stored as a memory, this solar azimuth angle memory can be used as a solar azimuth angle recognition means. Reference numeral 4 denotes a light amount measuring means for determining the amount of light incident on the window 1. This light amount measuring means 1 is mainly used to detect weather conditions and to recognize whether or not it is necessary to control the blind 2 in accordance with the solar azimuth angle α. belongs to. Therefore, when a two-dimensional optical sensor or the like is used as the solar azimuth angle recognition means 3 and an optical measuring means is used, it is possible to recognize at least the presence or absence of direct sunlight, so it is also possible to judge whether it is clear or not based on the solar azimuth angle. It can be obtained at the same time as calculating α. That is, when an optical measuring means is used as the solar azimuth angle recognition means 3, the light m measuring means 4 does not necessarily have to be used at the same time.

These solar azimuth angle recognition means 3 and light amount measurement means 4 are means for recognizing external light conditions, and at least one of them is an essential element in the system of the present invention. Note that as the light amount measuring means 4, an illuminance meter method and a pyranometer method can be considered. The illumination meter method measures light 'Ik using photoelectric conversion elements such as photodiodes, phototransistors, phototubes, and photomultiplier tubes, and is a method for obtaining outdoor horizontal illuminance including direct sunlight. 1. There are some methods that measure and measure only the sky light diffused at night, excluding direct light. Even using this sky light, it is possible to classify it into clear sky light and cloudy sky light. In the case of pyranometer method, use # as a sensor.
! It uses a couple and converts solar radiation m into heat, which is
k'dI! It's about changing your temperament and getting information.

In this case, since it is possible to know the amount of solar radiation reaching the earth's surface regardless of the wavelength of the light, it is possible to obtain information on the amount of solar radiation taken into the room at the same time. Therefore, it is suitable for controlling air conditioning by taking in the amount of heat.

In this way, information on the state of external light incident on the window 1 is taken into the control device 5, and based on this information, a control signal is given to the blind driving means 24, and the inclination of the slit 21 of the blind 2 is adjusted to the incident angle of sunlight. That is, control is performed according to the altitude angle of the sun, and the optimum state is selected to reflect sunlight onto the ceiling surface 6.

7 is a reflected light measuring means for monitoring the blind surface, for example, a luminance meter can be used. The characteristic of the luminance meter method is that, unlike the luminance meter, which captures incident light, it can capture the luminous flux divergence at that location. This reflected light?
j11 The purpose of the constant means 7 is to monitor the occurrence of reflected blur due to the reflected light L' of the sunlight on the slat 211ct=P of the slat 211ct=P.
Since it is a regular reflection of sunlight, it originally has a large brightness, but under normal conditions, the reflected light L' is reflected from the ceiling surface 6.
Since the light is incident on the sun, reflected glare does not occur during normal viewing indoors. However, according to experiments, an image of the sun is formed on each slat 21 due to a change in the slope of the slat 21 of the blind 2, and when the blind 2 is viewed from inside the room, it may appear as a vertical line of high brightness. Of course, this high-intensity line acts as an extremely unpleasant glare for the occupants of the room, and if such a reflection blur γ value occurs, it is necessary to immediately adjust the angle of the slit 21.

In this way, sunlight is absorbed without reflected glare, and the interior of the room is illuminated by sunlight even to the back. The indoor illuminance in this state is measured by a separately provided illuminance measuring means 8. As this illuminance measuring means 8,
The above-mentioned illumination meter method or luminance meter method is suitable. Although only one illuminance measuring means 8 is shown in the figure, two or more are installed along the depth of the room, and the information obtained by this illuminance measuring means 8 is given to the control device 5 to determine the The difference from the required illuminance is corrected by blinking or dimming the illuminant 9. For example, the shaded area shown in FIG.
To be precise, this value is a quantity that constantly changes, and is large in the morning, small during the day, and large again in the evening.

In order for the arsenal to follow this change step by step, it is preferable to provide a plurality of illuminance measuring means≠2.

The reflected light L' cannot be taken in by the slit 21 of the blind 2 if the sun is hidden by clouds or the like. When the sun cannot be seen, when the brightness is low even though the sun is out in the morning and evening, when the horizontal angle/Z relative to window 1 is large and the altitude angle of the sun is small, there is direct light. However, the illuminance is relatively low and there is no point in reflecting it.

Therefore, in such a case, it is necessary to set the pre-ind itself to be rolled up and to place the slat 21 horizontally.

It is preferable that such settings are performed by storing a time schedule in the control device. Further, it is preferable that a value ζ reflected light measuring means 7 (not shown) is installed for each blind 2, and that a plurality of rows of illuminating lights 9 are provided in parallel to the window 1, for example. Of course, all light sources such as fluorescent lamps, incandescent lamps, and high-pressure discharge lamps can be used.

In this way, there is a reflected light measuring means 7 in the room for eliminating reflected glare on people in the room, and an illuminance measuring means 8 for obtaining information for blinking or dimming the lighting lights in order to ensure the required illuminance. provided. All of these are indoor light condition recognition means that recognize the indoor light condition, and reflective glare can theoretically be prevented from occurring if it is taken into account when determining the above-mentioned optimal reflection angle. 8-value illuminance measuring means is important as a means of recognizing indoor light conditions.

Of course, it is possible to calculate the design illuminance deficiency distribution by efficiently introducing sunlight into the room, so a separate Ω point reduction control device is used to control the blinking or dimming of the illumination light 9. It is also possible to control it using a controller, or manually if it is mass-produced.

Figure 1 is explained using Figure 10.
This is a block diagram showing the brightness system, and includes external light condition B recognition means 3 such as solar azimuth angle recognition means and light amount measurement means.
The blinds 10 for daylighting are controlled by taking in necessary information on the state of external light from 0 and, if necessary, taking in information from an indoor state detecting means 70 such as a reflected light measuring means, a time schedule, etc. Mayu, on the other hand, the illuminance ff1ll
Indicates that the lighting lights 90 should be fully automatically or manually blinked or dimmed by 6 degrees, based on information from a room condition recognition device such as a control device, or a time schedule created from predictive data.

FIG. 12 shows a flowchart for controlling the lighting system shown in FIGS. 10 and 11. Ko (7)
Using a flowchart, the operations of each element that have been individually explained up to now will be explained as one flow. in this case,
The time schedule can be set arbitrarily.In other words, in a large system, it is determined whether or not it is a control time zone based on the signal from the clock built into the control device. depends on the time schedule that is set according to the actual usage of the room.After entering the control time zone, monitoring is performed to see if it is possible to enter a different control time zone.In addition, when performing this type of control, In this case, it is set to enable both automatic and manual operation, and manual operation is treated as a type of interrupt operation within automatic operation.Therefore, if the control time period is interrupted, automatic control tI is always activated. We will monitor whether or not the situation is normal.

First, it is determined whether the blind control @jf is set to automatic, and if it is set to automatic and frU (1) The outside light state information obtained by the above-mentioned outside light state recognition means is taken in. At this time, the information taken in and E7 If there is at least direct sunlight, it is information about the butterfly's azimuth.Based on this information, the azimuth angle of the butterfly is There is a cloth that can also control the solar azimuth, in which case it is necessary to correspond to the software that controls the control device for each state.Basically, information on the solar azimuth is obtained by solar azimuth recognition means. and set it by the light amount measuring means to obtain the vertical light (λ information.Then, the light amount 53a light f
Control the slat angle of the blind by comparing i E I .

In other words, if the reference light 'Ji E 1 is less than the standard light, set the slat angle horizontally, and if the reference light quantity E is around the gold, then set the slit angle to obtain the optimum reflection angle for the solar azimuth angle. Control. The concept of this optimal reflection angle is as described above, and the blind drive device is driven based on the calculation result in the control device. To simplify this kind of basic control, divide the solar azimuth into seasons such as spring, summer, autumn, and winter, set the average azimuth, and set the slat angle of the puller in advance for that solar azimuth. The slit angle is calculated and written in a storage device as a means for recognizing external light conditions, for example, in the form of time fluorescence. In this way, control can be performed based on the previously stored information by simply providing a light amount measuring means and taking in information on the amount of external light.

Next, reflected light is captured by the reflected light measuring means and reflected glare is monitored. When reflected glare occurs, the information is fed back as slit angle adjustment information to perform adjustment. At this time, adjustment is performed in the direction in which the reflected light faces upward. After the reflective gray is removed in this way, it is manually checked whether the illumination lamp is in the automatic control state.

If there are a number of automatic control states, the illuminance information is captured by the illuminance measuring means. In this case as well, the set reference illuminance E, -
Based on the difference, a control signal for blinking or dimming the illumination lamp is obtained and the illumination lamp is controlled.

It should be noted that, theoretically, reflected glare will not occur if the blinds are installed with high precision and control is performed to prevent reflected glare. As mentioned above, this reflected light measuring means and its measurement information are
Depending on the accuracy of the blind itself and the accuracy of slit angle control, there may be no problem even without this control. In that case, you can omit this. However, it is of course not necessary to control the illumination lights within this control system, such as building a system that can be controlled manually.

In this lighting system, we consider blinking or dimming of the lighting lights, and suggest that a combination of a control system and a separate control system is also possible (Thus,
Once the required illuminance can be secured throughout the indoor silkworm body, it is only necessary to monitor the occurrence of new interruptions.

Of course, this state is maintained throughout the set control time period.

In an actual system, it is necessary to set a sufficient delay i''L and time to prevent complicated driving of blinds and flickering of illumination lights due to movement of clouds using the light amount measuring means d';
It is equipped with an automatic switching mechanism from manual operation settings to automatic control, and of course a power outage compensation circuit.

FIG. 13 shows an example of the configuration of the ili control device. 5.1
Reference numeral 1 denotes a control device, which has one predetermined 10 input key 501 for inputting various control conditions. This input 1 signal is passed through the encoder 502 and the padlock 503 to the input data register 504, passes through the code conversion circuit 505 and the register 506, and is transferred to the main storage device 520 (c-).

510 is an oscillator using a crystal or the like, and a divider 511,
A timing signal is generated via a frequency divider 512. 5
13 is a counter which combines the signals from the time register 514 and supplies it to the driver 515 to display the time 516;
07/ri decoder, 508 is a control timing circuit,
This is a 509 input signal changeover switch. Reference numeral 300 denotes an outside light U recognition means, and the next information obtained by this is sent to the interface 'JJ7Ace 52' of the control device 500 via the amplification circuit 301.
1 and import it into the main memory Rs 20. These pieces of information are given to the holding register 524 via the φ card data register 522 and the decoder 523, and are input to the processor 530 at the necessary timing. 710 is a reflected light measuring means, 71.1 is an amplifying circuit thereof, 720 is an illuminance measuring means, and 721 is an amplifying circuit thereof, and information obtained from these is provided through interfaces 525 and 526'f, respectively.
! : is input to the arithmetic unit 530 through the process. The results of all these calculations are supplied to the relay circuit through the entire doripa 531, and by driving the relay circuit 532, the lighting lamp 900
, controls the blind 100. In addition, in this device, control of the illumination lamp 900 by the illuminance measuring means 72'0,
Since control of the blind 100 based on other information is parallel control, it is also possible to separate the control. Next, when solar azimuth angle information is stored in the main storage device 520 instead of the solar azimuth angle recognition means in the external light state recognition means 500, the signal of the counter 513 is taken in through a code conversion circuit, a register, etc. It is better to read the information while matching it with the time information.

Due to such reflection of outside light into the room, sunlight, which was previously completely wasted, can be used for lighting. Therefore, assuming that indoor lighting is controlled, the window value ;If facing south and the opening ratio (window area/total area of wall where the window surface exists) is 35~'0%ulJr, if the normal operating hours are from 9:00 a.m. to 6:00 p.m. Through annual rWi, lighting power can be saved by 30-tO%.

〔Effect of the invention〕

As explained above, the great invention is to use blinds that were conventionally used to block light to let in light.By reflecting sunlight on the ceiling surface, the ceiling surface can be used as a pseudo light source for visual work. Obtaining suitable diffused light. As a result, the required illuminance is approximately doubled in depth compared to the case without the blind door 2, and unpleasant glare can also be prevented, resulting in a good lighting environment value 2. Furthermore, since there is less need for auxiliary illumination due to lighting of illumination lights, it is possible to save a large amount of power for illumination.

[Brief explanation of drawings]

The 8X1 diagram is a cross-sectional view of a room showing how sunlight enters through a window, Figure 2 is a cross-sectional view of a room showing how sunlight is reflected onto the ceiling with blinds, and Figure 3F is a cross-sectional view of a room showing how sunlight is reflected on the ceiling through blinds. A sectional view showing an example, Fig. 4 is an explanatory drawing explaining the inclination of the slat and the shape of reflected light, Fig. 5 is a sectional view showing another example of slats, and Fig. 6 is a sunlight on the window. Figure 7 is an explanatory diagram showing the relationship between the inclination angle of the slit and the reflection angle. Figure 8 is an explanatory diagram explaining the incident state of the slit. A characteristic diagram showing the experimental results, FIG. 10 is a curse diagram explaining the lighting system according to the present invention, FIG. Fig. 13 is a block diagram showing an example of the control device according to the present invention. In the figure, 1 is a window, 2 blinds, 21 is a slit, and 3 is a solar azimuth angle recognition means. , 4 is a light amount measuring means, 5Fi
A control device, 7 a reflected light measuring means, 8 an illuminance measuring means, L
, and L' is its reflected light. $6 Atsushi 8 Figure 0 1B 36 5.4
729 (yn) No. fj Figure 0 Continuation of page 1/'7 Eviction applicant Nichibei Co., Ltd. 3-15-7 Nihonbashi, Chuo-ku, Tokyo

Claims (1)

[Claims] 1. The inclination of the slats of the blind is controlled based on the information on the outside light condition to efficiently bring in outside light into the room, and the blind is installed indoors based on the information on the indoor light condition at that time. A lighting method that utilizes outside light, which is characterized by adjusting and uniformizing the illuminance in a room by dimming and dimming lighting lights, etc. 2. an outside light condition recognition means for recognizing outside light conditions; a control device for calculating the slope of the slat according to the outside light information obtained by the outside light condition recognition means; a blind controlled by the control device; Outdoor light consisting of an indoor light recognition means that recognizes the light state, a control device that calculates the blinking or dimming state according to the indoor light information obtained by the indoor light recognition means, and lighting lights that are controlled by the control device. A lighting device that uses 3. An illumination device using external light as set forth in claim 2, characterized in that it comprises a light amount measuring means and a solar azimuth angle recognizing means as means for recognizing the state of external light. 4. An illumination device using external light, as set forth in claim 3, characterized in that a solar azimuth angle memory in which annual solar azimuth angles are stored in advance is used as the solar azimuth angle recognition means. 5. Scope of the Claims In claim 2, there is provided a constant illumination device 6 that uses external light, characterized in that it is equipped with means for measuring reflected light of a blind and means for measuring indoor illuminance as means for recognizing indoor light. In item 5, the lighting device using external light, characterized in that information from the reflected light measuring means is input to a control device, and the inclination of the slit of the blind can be adjusted.