VIVALDI antenna for RCS detection

Abstract

The invention relates to the field of antenna design, and discloses a VIVALDI antenna for RCS (radar cross section) detection, which comprises a base and a packaging ring mounted on the base, the packaging ring is connected with a plurality of base plates positioned on the outer side of the base, two surfaces of each base plate are sequentially connected with metal radiating surfaces, and the metal radiating surfaces are metal radiating surfaces of the antenna. Antenna index slot lines are further arranged on the two faces of the base plate, the base plate is connected with first open-circuit branches extending into the antenna index slot lines, a certain number of open-circuit branches are loaded on the metal on the two sides of the VIVALDI antenna index slot lines, the surface impedance of the antenna radiating surface can be changed through introduction of the open-circuit branches, and the antenna radiating surface can be improved. The resonance phenomenon of the antenna can be eliminated through the proper branch knot loading position, and the effect of suppressing the distortion of a directional diagram is achieved; in addition, the antenna can serve as a director of the antenna, and the directional diagram distortion effect of the antenna is relieved.

Description

Technical Field

[0001] This invention relates to the field of antenna design, and more particularly to a VIVALDI antenna for RCS detection. Background Technology

[0002] RCS (Radio Frequency Sampling) measurement antennas represent a unique branch of the antenna field, distinct from traditional antenna technology. As measurement antennas, they not only require a wide operating bandwidth to avoid testing errors caused by switching between different frequency bands, but also demand that the emitted electromagnetic waves closely approximate plane waves. This necessitates that the radiation patterns of the antenna array elements remain consistent within the antenna's operating frequency band. However, ultra-wideband antennas present certain technical challenges. Due to their wide bandwidth (typically several harmonics, high / low frequency points), resonance inevitably occurs within the band, leading to radiation pattern distortion. Common distortion effects include pits along the maximum radiation direction, multiple main lobes, and poor front-to-back ratio. Traditional methods for addressing radiation distortion involve slotting around the metal radiating surface, adding parasitic structures, or adding slot lines around exponential slot lines. Due to VIVALDI's ultra-wideband characteristics, its inherent metal structure inevitably exhibits some minor resonances within the wide bandwidth. These resonances affect the antenna's impedance matching, significantly increasing VSWR, and also impact radiation pattern quality, often causing distortion and affecting the overall antenna radiation performance. Summary of the Invention

[0003] To address the technical problem of large ratio difference, this invention provides a VIVALDI antenna for RCS detection.

[0004] The present invention is implemented using the following technical solution: a VIVALDI antenna for RCS detection, comprising a base and an encapsulation ring mounted on the base, wherein multiple base plates located on the outside of the base are connected to the encapsulation ring, and metal radiating surfaces are sequentially connected to both sides of the base plates, wherein the metal radiating surfaces are the metal radiating surfaces of this antenna, and antenna index slots are also provided on both sides of the base plates, and an open-circuit stub extending into the antenna index slots is connected to the base plates, wherein the open-circuit stub consists of two stubs of different lengths, one above the other.

[0005] As a further improvement to the above scheme, the size of the metal radiating surface is 220mm×360mm, and the open branch adopts a rectangular structure.

[0006] As a further improvement to the above scheme, the horizontal length of the shorter open branch is 20-30 mm and the width is 3-7 mm; the interval between the upper and lower branches is 15-25 mm, and the horizontal length of the longer open branch is 30-40 mm and the width is 3-7 mm.

[0007] The longer open-circuit stubs are loaded at a distance of 15–20 mm from the top of the antenna. The loading positions are around the antenna index slots and are arranged at equal intervals.

[0008] As a further improvement to the above scheme, the first branch adopts a hook-shaped structure.

[0009] As a further improvement to the above solution, an antenna pin is connected to the bottom of the encapsulation ring, and an auxiliary device for quick antenna connection and signal transmission is also installed inside the base. The auxiliary device is connected to the antenna pin.

[0010] As a further improvement to the above solution, the auxiliary device includes a protective ring located within the base, a plurality of clamping mechanisms that cooperate with the corresponding base plates are provided within the protective ring, a liquid tank for storing liquid is provided within the protective ring, a placement box located within the protective ring is provided on the liquid tank, and a pushing mechanism that cooperates with the clamping mechanisms is also provided within the protective ring. The pushing mechanism pushes some components in the clamping mechanism to move, triggering the clamping of the antenna pins. A follower box is connected to the bottom of the encapsulation ring, and a pushing block that cooperates with the pushing mechanism is fixedly connected to the middle of the follower box.

[0011] As a further improvement to the above solution, the pushing mechanism includes multiple volume boxes fixedly connected to the protective ring. A pushing rod is sealed and slidably sleeved inside the volume box. The moving end of the pushing rod is connected to one side of the clamping mechanism. A pressure control pipe, a return pipe, and a hose are connected to the end of the volume box away from the pushing rod. The hose extends into the liquid tank and is connected to the liquid tank. The other end of the return pipe and the pressure control pipe are both connected to a trigger chamber located at the top of the protective ring. A one-way valve and a pressure control valve are provided on the pressure control pipe. Multiple trigger sleeves for sealing ring limitation are connected inside the trigger chamber.

[0012] It also includes a push column that slides with the placement box, the bottom end of the push column extends and is connected to a pressure plate that slides and seals against the inner wall of the liquid tank, a hose is connected to the pressure plate, and the top of the pressure plate is also connected to an elastic component that is connected to the top plate inside the liquid tank.

[0013] As a further improvement to the above scheme, each clamping mechanism includes a push box arranged symmetrically. A slider is slidably fitted on the bottom surface of the push box near the push rod. The slider and the bottom of the other push box are both fixedly connected to a support rod that is fixedly connected to the bottom plate inside the placement box. A follower sleeve is slidably fitted inside both push boxes. A spring connected to the follower sleeve is fixedly connected to the side of both push boxes. A protective ring is fixedly connected to one side of the follower sleeve. A contact ring that fits into the antenna pin is fixedly connected inside the protective ring. A connecting line extending to the outside of the base is fixedly connected to the bottom of one of the push boxes.

[0014] As a further improvement to the above solution, the antenna pin includes a conductive post connected to the antenna, a protective sleeve is fitted on the outside of the conductive post, a follower block is fixedly fitted on the outside of the protective sleeve, a connecting groove is provided inside the follower block, and an embedded ring embedded in the connecting groove is fixedly connected to the follower sleeve.

[0015] As a further improvement to the above solution, the encapsulation ring is provided with a mounting groove, the encapsulation ring is installed in the mounting groove, the bottom of the base is provided with a volume cavity, and the bottom of the protective ring is also connected to a support column connected to the base.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: By loading a certain number of open-circuit stubs onto the metal on both sides of the index slot of the VIVALDI antenna, the introduction of these open-circuit stubs can change the surface impedance of the antenna radiating surface, thereby affecting the surface current of the antenna. Appropriate stub loading positions can eliminate the resonance phenomenon of the antenna and achieve the effect of suppressing pattern distortion. In addition, they can also act as directors of the antenna to alleviate the pattern distortion effect of this antenna, and are ultimately suitable for RCS detection.

[0017] 2. With the cooperation of the auxiliary devices in the corresponding base, the antenna can be quickly installed and replaced, reducing manual operation while ensuring signal shielding, thereby ensuring stable signal transmission and the working effect of the antenna. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the overall structure of the antenna of the present invention; Figure 2 This is a front view of the metal radiating surface of the antenna of the present invention; Figure 3 These are standing wave images before and after loading in this invention; Figure 4 The main polarization pattern at 0.5 GHz before and after loading of the present invention (the loading pattern shows a dip); Figure 5 This refers to the overall antenna gain within the operating frequency band after the invention is loaded. Figure 6 This is a schematic diagram of another structure of the open-circuit branch of the present invention; Figure 7 This is a schematic diagram of a partial structure of the antenna of the present invention; Figure 8 This is a schematic diagram of the base structure; Figure 9 This is a schematic diagram of a partial structure of the base; Figure 10 for Figure 9 A magnified view of the structure in the middle section; Figure 11 This is a schematic diagram of the front sectional view of the base; Figure 12 for Figure 11 Enlarged view of a portion; Figure 13 This is a side view of the clamping mechanism. Figure 14 This is a partial front view of the clamping mechanism. Figure 15 This is a front view diagram of the antenna pin structure. Figure 16 This is a side view of the antenna pin structure.

[0019] Explanation of key symbols: 01. Base; 02. Encapsulation ring; 04. Metal radiating surface; 06. Antenna index groove; 07. Base plate; 08. Open circuit stub one; 09. Open circuit stub two; 11. Protective ring; 12. Volume cavity; 13. Mounting slot; 14. Conductive post; 15. Trigger cavity; 16. Volume box; 17. Hoses; 18. Support post; 19. Clamping mechanism; 20. Liquid tank; 21. Trigger sleeve; 22. Follower block; 23. Spring one; 24. Push box; 25. Support rod; 26. Pressure plate; 27. Connecting wire; 28. Follower sleeve; 30. Placement box; 17. Hoses; 33. Return pipe; 34. Pressure control pipe; 35. Push rod; 36. Follower box; 38. Push post; 39. Protective sleeve; 40. Connecting slot; 43. Slider; 44. Embedded ring; 45. Protective ring; 46. Contact ring. Detailed Implementation

[0020] The present invention will now be further described in conjunction with the accompanying drawings and specific embodiments. It should be noted that, without conflict, the various embodiments or technical features described below can be arbitrarily combined to form new embodiments. Example

[0021] Please combine Figures 1-4A VIVALDI antenna for RCS detection includes a base 01 and an encapsulation ring 02 mounted on the base 01. A base plate 07 located outside the base 01 is connected to the encapsulation ring 02. Metal radiating surfaces 04 are sequentially connected to the base plate 07, where the metal radiating surface 04 is the antenna's radiating surface. The antenna operates in the 0.3GHz-1GHz range. The signal propagates through the metal radiating surface 04. The base plate 07 also has an antenna index slot line 06, and an open-circuit stub 08 extending into the antenna index slot line 06 is connected to the base plate 07. The open-circuit stub 08 consists of two stubs of different lengths, one above the other. The loading of the open-circuit stub 08 is based on the metal radiating surface 04. The open-circuit stub 08, as a metal recording structure, eliminates minor resonances of the antenna radiator within the frequency band and also acts as an antenna director to improve the antenna pattern. The loading of the metal open-circuit stub 08 eliminates antenna distortion. The size of the metallic radiating surface 04 is 220mm × 360mm. The size of the metallic radiating surface 04 is selected based on the corresponding radio frequency signal. The open stub 1 08 adopts a rectangular structure, and the specific number of open stub 1 08 can be selected according to the actual optimization effect. The shorter open branch 108 has a horizontal length of 20-30 mm and a width of 3-7 mm; the interval between the upper and lower branches is 15-25 mm. The longer open branch 108 has a length of 30-40 mm and a width of 3-7 mm.

[0022] The longer open-circuit stub 08 is loaded at a distance of 15-20 mm from the top of the antenna. The loading position is around the antenna index slot line 06 and is arranged at equal intervals. The corresponding open-circuit stub 08 eliminates the small resonance of the antenna radiator in the frequency band and improves the antenna pattern.

[0023] Among them, such as Figure 3 As shown, the standing wave (SWR) images before and after loading are presented in this application. The solid line represents the SWR curve after loading, and the dashed line represents the SWR curve without loading the structure. After loading the structure, the SWR of the antenna decreases to a certain extent in the 0.45 GHz protection zone and increases to a certain extent in the 0.7 GHz protection zone. Overall, loading the structure has a certain optimization effect on the overall SWR of the antenna.

[0024] like Figure 4 As shown, the image depicts the antenna pattern before and after loading. The solid line represents the loaded pattern, and the dashed line represents the unloaded pattern. The focus is on analyzing the impact on the radiation pattern. The image shows that before loading, the maximum radiation direction of the antenna pattern is located at approximately theta = -50°, which is different from the expected radiation effect of this antenna, resulting in a distorted radiation pattern. After loading the antenna in this application, the antenna pattern returns to normal, and its maximum radiation direction returns to the axial direction (theta = 0°), thus confirming that loading in this application can eliminate the distortion effect of the radiation pattern.

[0025] like Figure 5 The image shown is the gain image of the antenna after loading in this application within the operating frequency band. The maximum gain is about 5.8 dBi, and the overall gain within the frequency band is not abnormal. Based on the above data, it is known that by loading a certain number of open stubs 08 on the metal surface of the exponential slot line of the VIVALDI antenna, the open stubs 08 are loaded on the upper half of the antenna. On the one hand, the open stubs 08 can change the surface current of the antenna metal surface and disrupt the micro resonance; on the other hand, they can act as directors. A suitable director as a metal structure can directly affect the antenna pattern, alleviate the distortion effect of the pattern, change the beamwidth of the pattern, etc., making the antenna suitable for RCS measurement. Example

[0026] Combination Figure 1-6 The further improvement of this embodiment based on embodiment 1 is that: the bottom of the open stub 1 08 is connected to the hook-shaped open stub 2 09. Through the hook-shaped open stub 2 09, the radiation can be better stabilized, resonance can be reduced, and the antenna signal propagation can be guaranteed.

[0027] Example 3: Combination Figure 7-16 Based on Embodiment 1, this embodiment is further improved in that: the bottom of the encapsulation ring 02 is connected to an antenna pin, which connects and transmits the signal to be transmitted. An auxiliary device for quick antenna connection and signal transmission is also installed in the base 01. The auxiliary device is connected to the antenna pin, clamps the antenna pin, and contacts the antenna pin, thereby transmitting the signal through the conductor.

[0028] The auxiliary device includes a protective ring 11 located within the base 01. Multiple clamping mechanisms 19, which cooperate with corresponding base plates 07, are installed within the protective ring 11. A liquid tank 20 for storing liquid is installed within the protective ring 11, and a placement box 30 located within the protective ring 11 is installed on the liquid tank 20. A pushing mechanism, which cooperates with the clamping mechanisms 19, is also installed within the protective ring 11. The pushing mechanism moves some components of the clamping mechanism 19, triggering the clamping of the antenna pins. A follower box 36 is connected to the bottom of the encapsulation ring 02. A pushing block, which cooperates with the pushing mechanism, is fixedly connected to the middle of the follower box 36. The pushing block contacts a component of the pushing mechanism, thereby causing a change in the volume within the liquid tank 20, resulting in liquid flow within the liquid tank 20. This causes the pushing mechanism to perform a corresponding action, and then the clamping mechanism 19 clamps the antenna pins, thus achieving overall signal conduction.

[0029] The actuating mechanism includes multiple volumetric boxes 16 fixedly connected to the protective ring 11. A push rod 35 is sealed and slidably fitted inside each volumetric box 16. The movable end of the push rod 35 is connected to one side of the clamping mechanism 19. A pressure control pipe 34, a return pipe 33, and a hose 17 are connected to the end of the volumetric box 16 away from the push rod 35. The hose 17 extends into and communicates with the liquid tank 20. Changes in the space within the liquid tank 20 cause liquid to enter the volumetric box 16 through the hose 17, thereby causing the internal pressure of the liquid to push the push rod 35, thus actuating the mechanism. The other ends of the return pipe 33 and the pressure control pipe 34 are both connected to a trigger chamber 15 located at the top of the protective ring 11. As the pressure inside the volumetric box 16 continues to increase... The liquid in the volume box 16 enters the trigger chamber 15 after passing through the pressure control pipe 34, which increases the liquid pressure in the trigger chamber 15. The pressure control pipe 34 is equipped with a one-way valve and a pressure control valve, and the return pipe 33 is connected to an electric control valve. Multiple trigger sleeves 21 for limiting the encapsulation ring 02 are connected in the trigger chamber 15. After the liquid in the trigger chamber 15 continues to increase, the trigger sleeves 21 are triggered to move, so that the moving end of the trigger sleeve 21 enters the follower box 36, thereby limiting the follower box 36 and completing the installation limitation of the encapsulation ring 02 and the antenna. The trigger sleeves 21 are interconnected pipes and rods. After the liquid pressure in the trigger chamber 15 increases, it pushes the rod to move, thereby allowing the rod to enter the follower box 36 and limiting the follower box 36.

[0030] It also includes a push column 38 that is slidably fitted with the placement box 30. The bottom end of the push column 38 extends and is connected to a pressure plate 26 that slides and seals against the inner wall of the liquid tank 20. The hose 17 is connected to the pressure plate 26. The top of the pressure plate 26 is also connected to an elastic component that is connected to the top plate inside the liquid tank 20. When the push column 38 contacts the push block, the push block pushes the push column 38 to move, thereby causing the pressure plate 26 to move, changing the space inside the liquid tank 20, and causing the liquid inside the liquid tank 20 to enter the volume box 16 through the hose 17, realizing the flow of liquid inside the liquid tank 20. When disassembled, the elastic component can make the pressure plate 26 return to its original position, completing the initial return of the entire device.

[0031] Each clamping mechanism 19 includes a symmetrically arranged push box 24. A slider 43 is slidably fitted on the bottom surface of the push box 24 near the push rod 35. The slider 43 and the bottom of the other push box 24 are both fixedly connected to a support rod 25 that is fixedly connected to the bottom plate of the placement box 30. A follower sleeve 28 is slidably fitted inside each of the two push boxes 24. A spring 23 connected to the follower sleeve 28 is fixedly connected to the side of each of the two push boxes 24. The follower sleeve 28 can move along the shape of the push box 24. During the movement of the push rod 35, the push box 24 on one side moves, and the spring 23 drives the corresponding follower sleeve 28 to move. The two springs 23 have different elastic coefficients, with the elastic coefficient of the relatively fixed push box 24 being larger. When the two follower sleeves 28 are close to each other, they can clamp the corresponding pins to realize the installation work.

[0032] A protective ring 45 is fixedly connected to one side of the follower sleeve 28. A contact ring 46 that is sleeved with the antenna pin is fixedly connected inside the protective ring 45. A connecting line 27 extending to the outside of the base 01 is fixedly connected to the bottom of one of the push boxes 24. The protective ring 45 performs the function of signal shielding. The contact ring 46 is made of metal to enable signal conduction. The connecting line 27 is an existing wire to enable signal conduction.

[0033] The antenna pin includes a conductive post 14 connected to the antenna. A protective sleeve 39 is fitted on the outside of the conductive post 14. A follower block 22 is fixedly fitted on the outside of the protective sleeve 39. A connecting groove 40 is provided inside the follower block 22. An embedded ring 44 embedded in the connecting groove 40 is fixedly connected to the follower sleeve 28. The conductive post 14 guides the signal, and the protective sleeve 39 shields the signal.

[0034] The encapsulation ring 02 is provided with a mounting groove 13, and the encapsulation ring 02 is installed on the mounting groove 13. The bottom of the base 01 is provided with a volume cavity 12. The bottom of the protective ring 11 is also connected to a support column 18 connected to the base 01. The mounting groove 13 facilitates the snap-fit ​​of the base plate 07 for installation. The support column 18 supports and stabilizes the protective ring 11.

[0035] The implementation principle of this embodiment is as follows: During installation, the base plate 07 is installed into the corresponding mounting slot 13, and the conductive post 14 is inserted into the contact ring 46. At this time, the encapsulation ring 02 continues to move, thereby driving the follower box 36 and the push block to move. The push block contacts the push post 38, pushing the push post 38 and the pressure plate 26 to move, so that the liquid in the liquid tank 20 enters the volume tank 16 through the hose 17. The liquid in the volume tank 16 increases, squeezing the push rod 35 to move, thereby causing the push box 24 on one side to move, further driving the follower sleeve 28, the push rod 35 and the contact ring 46 to move. Contact ring 46 approaches and clamps onto conductive post 14 to connect the antenna and transmit signals. At this time, the liquid in volume tank 16 continues to increase, and the internal liquid pressure breaks through the pressure valve. The liquid enters the trigger chamber 15 after passing through pressure control tube 34. The increase in pressure triggers trigger sleeve 21, causing trigger sleeve 21 to snap into follower box 36, thereby limiting the encapsulation ring 02 and follower box 36. When disassembling, the return pipe 33 is opened, allowing the liquid in trigger chamber 15 to re-enter volume tank 16 and then further re-enter liquid tank 20 through hose 17, restoring the initial state.

[0036] The above embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention shall fall within the scope of protection claimed by the present invention.

Claims

1. A VIVALDI antenna for RCS detection, characterized in that, The device includes a base and an encapsulation ring mounted on the base. Multiple base plates located on the outside of the base are connected to the encapsulation ring. Both sides of each base plate are sequentially connected to a metal radiating surface, which is the metal radiating surface of this antenna. Both sides of each base plate are also provided with antenna index slots. An open-circuit stub extending into the antenna index slots is connected to each base plate. The open-circuit stub consists of two stubs of different lengths, one above the other.

2. A VIVALDI antenna for RCS detection as described in claim 1, characterized in that, The size of the metal radiating surface is 220mm×360mm, and the open branch adopts a rectangular structure.

3. A VIVALDI antenna for RCS detection as described in claim 1, characterized in that, The shorter open branch has a horizontal length of 20-30 mm and a width of 3-7 mm; the interval between the upper and lower branches is 15-25 mm; the longer open branch has a horizontal length of 30-40 mm and a width of 3-7 mm. The longer open-circuit stubs are loaded at a distance of 15-20 mm from the top of the antenna, and are located around the antenna index slots and are arranged at equal intervals.

4. A VIVALDI antenna for RCS detection as described in claim 1, characterized in that, The open branch adopts a hook-shaped structure.

5. A VIVALDI antenna for RCS detection as described in claim 1, characterized in that, The bottom of the encapsulation ring is connected to an antenna pin, and an auxiliary device for quick antenna connection and signal transmission is also installed inside the base. The auxiliary device is connected to the antenna pin.

6. A VIVALDI antenna for RCS detection as described in claim 5, characterized in that, The auxiliary device includes a protective ring located within the base, with multiple clamping mechanisms that cooperate with corresponding base plates within the protective ring. A liquid tank for storing liquid is located within the protective ring, and a placement box located within the protective ring is mounted on the liquid tank. A pushing mechanism that cooperates with the clamping mechanisms is also located within the protective ring. The pushing mechanism moves some components of the clamping mechanisms, triggering clamping of the antenna pins. A follower box is connected to the bottom of the encapsulation ring, and a pushing block that cooperates with the pushing mechanism is fixedly connected to the middle of the follower box.

7. A VIVALDI antenna for RCS detection as described in claim 6, characterized in that, The pushing mechanism includes multiple volume boxes fixedly connected to the protective ring. A pushing rod is sealed and slidably sleeved inside each volume box. The moving end of the pushing rod is connected to one side of the clamping mechanism. A pressure control pipe, a return pipe, and a hose are connected to the end of each volume box away from the pushing rod. The hose extends into the liquid tank and communicates with the liquid tank. The other ends of the return pipe and the pressure control pipe are both connected to a trigger chamber located at the top of the protective ring. A one-way valve and a pressure control valve are provided on the pressure control pipe. Multiple trigger sleeves for sealing the ring are connected inside the trigger chamber. It also includes a push column that is slidably fitted with the placement box, the bottom end of the push column extending and connected to a pressure plate that slides and seals against the inner wall of the liquid tank, the hose being connected to the pressure plate, and the top of the pressure plate being connected to an elastic component that is connected to the top plate inside the liquid tank.

8. A VIVALDI antenna for RCS detection as described in claim 7, characterized in that, Each of the clamping mechanisms includes a symmetrically arranged push box. A slider is slidably fitted on the bottom surface of the push box near the push rod. The slider and the bottom of the other push box are both fixedly connected to a support rod that is fixedly connected to the bottom plate inside the placement box. A follower sleeve is slidably fitted inside both push boxes. A spring connected to the follower sleeve is fixedly connected to the side of both push boxes. A protective ring is fixedly connected to one side of the follower sleeve. A contact ring that fits into the antenna pin is fixedly connected inside the protective ring. A connecting line extending to the outside of the base is fixedly connected to the bottom of one of the push boxes.

9. A VIVALDI antenna for RCS detection as described in claim 8, characterized in that, The antenna pin includes a conductive post connected to the antenna. A protective sleeve is fitted on the outside of the conductive post. A follower block is fixedly fitted on the outside of the protective sleeve. A connecting groove is provided inside the follower block. An embedded ring is fixedly connected to the follower sleeve and embedded in the connecting groove.

10. A VIVALDI antenna for RCS detection as described in claim 9, characterized in that, The encapsulation ring is provided with a mounting groove, and the encapsulation ring is installed on the mounting groove. The bottom of the base is provided with a volume cavity, and the bottom of the protective ring is also connected to a support column connected to the base.

Images